AU644255B2 - Control system for diesel engines - Google Patents

Description

1 644255

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

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0 S. S 0 0 Name of Applicant(s): Address for Service: Invention Title:

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ALLGAS ENERGY LIMITED CULLEN CO., Patent Trade Mark Attorneys, 240 Queen Street, Brisbane, Qld. 4000, Australia.

CONTROL SYSTEM FOR DIESEL *560

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Details of Associated Provisional Applications: filed 17 December 1990 No. PK3942 The following statement is a full description of this invention, including the best method of performing it known to us: 2 THIS INVENTION relates to a control system for diesel engines running on a mixture of natural gas and diesel fuel.

Normally in such engines it is usual that gas may be supplied to the engine after the engine has been idling on diesel fuel. When gas is supplied to the engine this reduces the rate of supply of diesel fuel until a pilot level is attained which then may be used to ignite the gas.

In particular the control system of the invention is especially directed to controlling the amount of natural gas utilized in such diesel engines in response to engine 0* load and speed and the specific requirements of a person driving the diesel engine.

Hitherto it has been a long felt want in regard to diesel engines running on a mixture of natural gas and diesel fuel that the amount of gas utilised in such engines be precisely controlled for the purpose of economy and S" efficiency. However conventional control systems which have been utilised to date have not been totally satisfactory in achieving this particular objective.

In one conventional control system a mechanical metering device was utilised to control gas flow to the diesel engine which was associated with a throttle valve or butterfly valve op"' tively connected to the accelerator pedal. The amount of diesel fuel supplied to the engine was regulated by the diesel governor up to the pilot limit.

3 However a particular disadvantage of this conventional arrangement was that the supply of gas to the engine was totally controlled by the driver and at light engine load or at high speed cruising this only resulted in wastage of gas because although the diesel governor reduced supply of diesel fuel to the engine, gas continued to flow at a high rate. This conventional arrangement was therefore inefficient because of the fact that control of gas supply to the engine was totally at the behest of the driver. Thus there was no means of reducing the supply of gas to the engine at high speeds.

In another conventional arrangement an electronic apparatus was utilized which required the use of a microprocessor for control of a reduction in the supply of diesel fuel to the engine and the introduction of gas supply to the engine. A throttle valve was controlled either directly by the microprocessor or directly by the accelerator ,*pedal. However this arrangement was found to be complex and expensive. It was also found to be difficult to operate and I *:'.maintain especially in relation to different types or makes of diesel engines. This arrangement was also expensive to install and could not be adjusted or installed by an .:..**unskilled person but required a specialized electrical mechanic.

It therefore is an object of the invention to provide a control system for a diesel engine running on diesel fuel and natural gas which precisely controls the rate of supply of natural gas to the diesel engine so as to alleviate the problems of the prior art referred to above.

The control system of the invention includes switch means for switching on the supply of natural gas to the engine when the engine exceeds a predetermined minimum speed or and (ii) control means for controlling the amount of natural gas fed to the engine wherein said control means is operatively connected to a throttle valve and operable when a pressure differential is present between said throttle valve and said control means.

Alternat,2ely the switch means may operate by means of a preset time delay after throttle opening. In another variation the switch means may operate by means of a driver operated switch.

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All engine speed sensor is therefore preferably

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o provided in association with the switch means so as to close the switch means and open the gas supply when the preferred minimum engine speed is reached or exceeded from 900- 1800 rpm). The speed sensor may be fitted to a rotating part of the engine which is related to engine speed such as a V U flywheel ring gear, fuel pump coupling, or alternator cooling fan so as to give a frequency input to the switch means.

The switch means may also be operatively connected to a solenoid valve which opens in response to closing of the switch means to permit gas flow to the engine. The switch means may be a mechanically operated switch or more preferably a relay operatively associated with an integrated circuit which closes the circuit when the voltage has built up to a predetermined value. The speed switch may be electrically connected to the ignition switch and be controlled by a magnetic pick up which is the preferred form of sensor. However it will be appreciated that a sensor may 4* be dispensed with if the speed switch is connected to the alternator which may supply a signal to the speed switch to o* close the speed switch when a predetermined frequency is attained.

The control means may include a gas flow control **so: a"valve which includes a valve body, a movable valve member located in the valve body and a valve seat whereby the valve is closed when the valve member abuts the valve seat and is *open when the valve member is spaced from the seat. In a more preferred form the valve aay include a flexible or resilient diaphragm which may be mounted to a hollow interior or valve inner bore and which is operatively associated with the movable valve member. The inclusion of the flexible diaphragm makes the control valve responsive to changes in 6 negative pressure at the throttle valve resulting in movement of the valve member from the closed position to the open position and vice versa.

Preferably the movement of the valve member may be adjustable so as to determine the maximum amount of natural gas which may be supplied to the diesel engine. It will be readily appreciated that this value will vary depending upon the type and make of diesel engine.

The valve member and/or flexible diaphragm is also I- preferably associated with a restoring spring or other "a suitable biassing means which biasses the valve member to a position wherein the valve is in the open position.

The valve member may also include a movable abutment member which may abut the valve seat when the valve 6 6" is in the closed position. This is useful so that movement of the abutment member along the valve member may give the correct or desired relationship between throttle valve negative pressure and 'valve member travel.

The diesel control system of the invention may also 2 include diesel limit means to limit the amount of diesel fuel supplied to the diesel engine. In one form, the limit means may be operatively associated with a fuel metering means present in a diesel fuel pump which metering means can be mechanically operated or fluid actuated (eg hydraulically or pneumatically).

It will of course be appreciated that the diesel 7 pump may be mechanically operated or fluid actuated.

In this arrangement the limit means may be associated with a rack and pinion with metering sleeve wherein rack movement is limited by direct operation on the rack.

Alternatively the limit means may be associated with the maximum diesel fuel pump setting or be associated with partial closure of the fuel pump stop mechanism.

The limit means may be of a suitable type including 3- a fluid actuated ram or a mechanical linkage associated with S a diesel pump input lever or a combination of these specific forms of limit means.

The limit cylinder is suitably attached to the fuel control of the diesel pump in any suitable manner when the me 'e speed switch is closed and gas initially supplied to the piston or plunger of the limit cylinder limiting the rate of supply of diesel fuel until a maximum pilot level is obtained. The variation of pilot level below the maximum value is determined by the diesel pump governor.

Pi The control system of the invention may also o include damping means for.damping the rate at which diesel V"e fuel is withdrawn from the diesel engine when the speed switch is closed and gas is initially supplied to the diesel engine. Preferably the damping means allows a slow reduction in the rate of supply of diesel fuel to the engine when the speed switch is closed and a fast increase in the rate of 8 supply of diesel fuel when the speed switch is opened (ie.

when the gas supply is shut off).

To this end the damping means may include a fluid actuated damping member or damping ram comprising a cylinder or barrel having a piston associated therewith which is movable pneumatically. More preferably a damping valve may be used operatively associated with the diRsel limit cylinder having a bleed passage and a movable valve member such as a ball biassed to the closed position when the ball abuts the If valve seat.

St .t When the gas supply is cut off the gas may flow *o through a main passage of the damping valve thereby causing movement of the ball away from the valve seat and thereby facilitating a quick release of gas from the limit cylinder and a fast retraction of the piston of the limit cylinder so that diesel fuel may be supplied to the engine at a maximum rate.

Alternative forms of damping means include a spring operated damper or other forms of fluid actuated dampers (eg a hydraulically operated damper).

Reference may now be made to a preferred embodiment of the invention as shown in the accompanying drawings wherein FIG 1 is a schematic view of a control system constructed in accordance with the invention; FIG 2 is a detailed view of the control valve or 9 gas governor used in the control system of FIG 1; FIG 3 is a dotailed view of the diesel limit means and of the damping means with FIGS 3a and 3b showing the s..ethod of preparation of the damping means; and FIG 4 is a drawing of the electrical circuitry involved in the switch means described above.

The control system as shown in FIG 1 is designed to control fuel supply to a diesel engine running on mixed fuel (natural gas/diesel) in response to load and speed and the 1" requirements of the driver. The system is most effective for S use on naturally aspirated diesel engines and can be adapted to suit diesel engines of all sizes and types.

The system functions by cutting the diesel fuel *0 level used by the engine to a pilot level. The diesel pilot is ignited in the usual way by the compression in the cylinder. The diesel flame then ignites the natural gas/air mixture in the combustion chamber. The system controls how 0 0 much gas is injected or aspirated into the engine and the diesel is governed by the engine as per normal operation. If the system is not functioning or the gas is cut off, the 0 engine will perform as a normal diesel engine.

As shown in FIG 1, the vehicle cylinders 1 are used to store the natural gas. The cylinders come in a wide range of sizes and the number fitted to each vehicle depends on the range of the vehicle required and the space limitations of the vehicle. A possible arrainement of cylinders and the connecting tubing is shown. Other connecting arrangements and means are possible. The cylinders can be filled via the filling connection 3 from a standard compressed natural gas dispenser. The isolation valve 2 is used to isolate the cylinders from the rest of the system in the event of a gas leak to stop loss of all gas on board. A pressure sensor 5 is fitted to the high pressure line from the cylinders to the engine and connected to the dashboard fuel indicator 4 to give the driver an indication 1 r of how much natural gas remains on board. A fused gas on Sswitch 21 is provided for safety. The 12VDC supply to the 0S indicator 4 is obtained from the vehicle gas on switch 21 and reduced from 24VDC if available.

The high pressure gas is connected to a primary

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regulator 6. The primary regulator 6 may be heated by engine coolant. The size of regulator and pressure setting is selected depending on the maximum gas requirements of the engine. The low pressure gas supply to the engine is Scontrolled by a normally closed solenoid 7 which opens when 1 the engine requires the natural gas. A normally open solenoid 8 is connected in parallel with the solenoid 7 so that all gas in the engine supply line is vented to the S xhaust or intake pipe when ga. is not required by the engine. To this end a check valve 22 is operatively associated with solenoids 7 and 8 as shown.

Alternatively a three way solenoid valve may be 11 employed instead of solenoids 7 and 8.

When gas is supplied to the engine via the solenoid 7, a pressure line is connected to a pneumatic cylinder 10. The damper 9 allows slow extension of the S diesel limit cylinder 10 and fast retraction when gas is shut off. This provides a smooth transition from diesel to mixed fuel and back to diesel. Once actuated by gas pressure, the diesel limit cylinder 10 adjusts the maximum delivery of the diesel pump to the engine to a pilot level.

3' The pilot level diesel supply is used to ignite the natural gas supplied to the engine. The standard diesel governor varies the pilot level up to a set maximum. The diecel can be limited in many ways such as direct rack limit or stop lever movement. Various links can be employed to provide the vrecessary diesel limit operation.

The gas is supplied to the engine through a zero pressure or vacuum demand regulator 11 and a gas governor 12. The demand regulator 11 supplies gas to the engine as long as there is a suction or vacuum on its outlet (ie. while I the engine or intake manifold has a lower pressure than the outlet of the demand regulator). The gas governor 12 is a valve which controls the supply of gas to the engine depending on the throttle valve pressure differential. The gas governor senses the pressure differential via a connection to a control butterfly or throttle valve 14 in the air intake line. The governor 12 has an ad'istment screw for 12 setting maximum gas supplied to the engine. The gas governor 12 is also coi.nected to the engine tappet cover breather to give a supply of lubricating oil mist to the internal surfaces of the gas governor. The gas from the gas governor is fed into the intake air stream using a mixer 13 downstream of the air filter 15 and upstream of the control butterfly 14.

The control butterfly 14 is moved by a mechanical linkage 16 connected to the accelerator cable input to the I" diesel pump. This linkage could be either by levers or cable.

A speed switch 18 is included in the system to improve performance. At low engine speed, the engine may r* Perform better on diesel only than on mixed fuel. For this *9 reason, the speed switch is set to bring in the gas supply at a certain engine speed. A speed sensor 19 is fitted to a rotating piece of the engine which is relative to engine speed to give a frequency input to the speed switch 18. A low gas pressure switch 17 is provided to ensure that no gas is supplied to the engine where there is insufficient gas *99999 pressure to actuate the diesel limit cylinder 10. This to prevent excessive fuelling. An oil pressure switch 20 is added to the circuit to ensure no gas is supplied to the engine should the engine oil pressure be low (ie. not running). The 24VDC power to the speed switch 18 is supplied from the ignition switch of the vehicle through the gas on 13 switch 21 to the speed switch 18. I- all switches are in the on position, the speed switch 18 activates the solenoids 7 and 8 to supply gas to the engine once the preset engine speed is exceeded. The cut in speed can be adjusted at the speed switch to suit the vehicle.

The control valve shown in FIG 2 is to be used as part of a mechanical control system using the engine to control the natural gas supply in a feedback circuit. The control valve or gas governor 30 adjusts the amount of gas I- delivered with respect to engine load and speed. It does

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this by monitoring the engine intake manifold throttle pressure differential fromi a suitable device such as a throttle butterfly or throttle valve.

Oe The valve 30 consists of a body 32 and a cap 31 which are bolted together and sealed by an 0 ring 45. A mounting bracket 35 is fitted between parts 31 and 32 as shown for mounting purposes. The governor body 33 and the governor cap 34 are bolted together with the diaphragm 29 between them. The governor body 33 is bolted to the valve body 32.

It is possible to rotate components 31, 32, 34 and 35 to any of four right angles positions relative to each other due to four screws being used between adjoining components. This makes fitting of the component much easier than if this were not the case.

The valve mechanism consists of a spindle 41 which is made long enough to suit the valve body. The fuel disc or movable abutment member 42 is located along the length of the spindle to give the correct relationship between manifold pressure differential and valve travel. The fuel disc seats on the spindle over an 0 ring 44 and is held in place by two circlips 43. The spindle is supported at the outer end by a bush 40 held in an adjustment screw housing 39. At the valve body 32 end, the spindle 41 is held in place by another nylon bush 46.

1The valve spindle head 47 connects the valve 6* spindle to the control diaphragm 48 using a retainer pin and circlip 49. This makes the movement of the valve spindle 41 related to the movement of the control diaphragm 48. The *e S entire valve spindle assembly is self-aligning giving sealing between the fuel disc 42 and the valve body 32 when closed.

The maximum travel of the spindle is controlled by the set screw 39 fixed by locknut 38. This adjustment determines the maximum natural gas fuel supplied to the engine, a factor which varies from engine to engine. The i internal diameter of the valve body 32 determines the sealing orifice of the valve. This diameter can be sized to give higher gas flow, depending on the capacity of engine the governor is to be used on.

The gas inlet and outlet to the valve is via two pieces of tube 36 and 37 fitted to valve cap 31 and the valve body 32 respectively. Gas inlet is from a suitable regulator and gaF outlet is to a suitable mixer in the air intake duct.

A hose fitting 51 is screwed into the governor cap 34. This enables connection of the governor cap to the engine intake manifold throttle via a hose. This supplies a pressure differential to the upper side of the control diaphragm 29. As the pressure differential experienced by the governor control diaphragm decreases below a preset value, the diaphragm 29 moves to reduce the gas supply. It does this by pulling the spindle 41 and thus the fuel disc 42 3" towards the sealing surface of the valve body 32. The movement of the control diaphragm 29 is determined by the spring 52 used and the opening of the butterfly 14. At a

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*certain pressure differential the valve is closed giving gas control.

A spring damper 53 is screwed into the governor cap 34 to control governor hunting at intermediate speeds and light engine loads. The damper is held in place by rubber 0 locking ring 54 which is compressed by the damper cap A hose connection 50 is screwed into the governor i. body 33 to connect a hose to the engine tappet cover breather. This allows a small amount of oil, in the form of "blow by" mist, to enter the governor and lubricate the spindle 51 as it slides on the nylon bushes 40 and 46. The oil mist also ensures the diaphragm 29 retains flexibility.

In FIG 3 there is shown diesel injection pump having a fuel control rack 61. There is also provided an 16 adaptor 62 attached to pump 60 with internal thread 63 into which diesel limit cylinder 64 can be screwed. A lock nut is provided to facilitate fixing of limit cylinder 64 to adaptor 62. The limit cylinder 64 includes a plunger 66 biassed by spring 67 to the retracted position. The plunger 66 has attached thereto a piston 68 with an annular seal 69.

There is also shown end cap 70 retained by circlip 71 and o'ring 72. There is also shown flexible hose 73 having inlet end 74 attached to end cap 70. There is also shown flexible 3 hose 73 having inlet end 74 attached to end cap 70. There is .0 also shown damping valve 75 attached to end 76 of hose 73.

The damping valve 76 includes a main passage 77 and bleed Q •port 78 and valve body 79. Also shown is valve ball The operation of the damping valve 75 is shown in FIGS 3a and 3b. Upon gas switching the ball check 80 closes valve seat 81 thus forcling gas to flow through bleed port 78 causing -he plunger 66 of limit cylinder 64 to extend slowly o' until it abuts shoulder 82. This limits therefore the travel of rack 61.

SUpon the speed switch 18 opening the gas pressure *co is vented resulted in ball 80 unseating from valve seat 81 o and thereby allowing the plunger 66 to retract quickly until S*rack movement is uninhibited.

In FIG 4 there is shown a block diagram of the electrical circuitry concerning the speed switch which operates as discussed on the drawing.

17 The tachometer I/C is a conventional integrated circuit chip obtained from any electrical supplier and is illustrated in Radio Spares Data Sheet 4901.

It will also be appreciated that the control system of the invention will operate on all gaseous fuels requiring pilot ignition. Thus the term "natural gas" also includes within its scope all gaseous fuels requiring pilot ignition and thus could include manufactured gas within its scope.

It will also be appreciated that the limit means 1 r and damping discussed previously may not have to be used in ".relation to certain types of diesel engines such as marine engines or fixed speed engines.

From the foregoing it therefore will be appreciated that the invention facilitates precise control of the amount of gas utilised in the diosel engines running on the mixture of natural gas and diesel fuel and thus has substantial advantages over the prior art.

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Claims (17)

1. 2. A control system as claimed in Claim 1 wherein an engine speed sensor is operably associated with the switch S means so as to close the switch means when the engine minimum speed is reached or exceeded.
2. 3. A control system as claimed in Claim 2 wherein the W speed sensor is fitted to a rotating part of the engine.
3. 4. A control system as claimed in any preceding claim wherein the switch means is operatively connected to a solenoid valve which opens in response to closing of the S:se*S switch means to permit natural gas flow to the engine.
4. 5. A control system as claimed in Claim 4 wherein the switch means is a relay operatively associated with an integrated circuit which closes the circuit when the voltage has built up to a predetermined value.
5. 6. A control system as claimed in any preceding claim 19 wherein the switch means is electrically connected to an ignition switch.
6. 7. A control system as claimed in Claim 6 wherein the sensor is a magnetic pick up.
7. 8. A control system as claimed in Claim 1 wherein the switch means is connected to an alternator which supplies a signal to the switch means to close same when a predetermined frequency is attained.
8. 9. A control system as claimed in any preceding claim wherein the control means includes a gas flow control valve which includes a valve body, a movable valve member located in the valve body and a valve seat whereby the valve is closed when the valve member abuts the valve seat and is open when the valve member is spaced from the seat.
9. 10. A control system as claimed in Claim 9 wherein the valve member includes a flexible or resilient diaphragm which may be mounted to a hollow interior or valve inner bore and a CC which is operatively associated with the movable valve member.
10. 11. A control system as claimed in Claim 9 or 10 wherein the movement of the valve nmember is adjustable so as to determine the maximum amount of natural gas which may be supplied to the diesel engine.
11. 12. A control system as claimed in Claim 10 or 11 wherein the valve member and/or the flexible diaphragm is associated with biasing means which biases the valve member to an open position.
12. 13. A control system as claimed in any one of Claims 9 M to 12 and further including a movable abutment member which may abut the valve seat when the valve member is in the closed position.
13. 14. A control system as claimed in any preceding claim and further including diesel limit means associated with a diesel fuel pump for limiting the amount of diesel fuel supplied to the diesel engine. A control system as claimed in Claim 14 wherein the diesel limit means is operatively associated with a fuel metering means present in the diesel fuel pump.
14. 16. A control system as claimed in Claim 14 wherein the diesel limit means includes a fluid actuated ram or mechanical linkage associated with an input lever of the diesel pump.
15. 17. A control system as claimed in Claim 14 wherein the limit means is associated with a maximum fuel setting of the diesel plump or is associated with partial closure of a stop mechanism of the fuel pump. q
16. 18. A control system as claimed in any preceding claim also including damping means for damping the rate at which diesel fuel is withdrawn from the diesel engine when the switch means is closed and natural gas is initially supplied to the diesel engine.
17. 19. A control system for diesel engines substantially as herein described with reference to the accompanying drawings. DATED this 5 day of October, 1993. ALLGAS ENERGY LIMITED By their Patent Attorneys CULLEN CO. ABSTRACT A control system for diesel engines running on a mixture of natural gas and diesel fuel which may control the rate of supply of natural gas to the diesel engine. The control system includes switch means (18) for switching on the supply of natural gas to the diesel engine and control means for controlling the amount of natural gas fed to the di sel engine when the control means (30) is operatively connected to a throttle valve (16) and operable when a pressure differential is present between the throttle valve S S, and the control means. Suitably the switch means is operable @0 to allow natural gas to be supplied to the diesel engine when j e the engine exceeds a certain minimum speed of r.p.m. Mhe control means may include a gas flow control valve which 4 'e includes a valve body a movable valve member (41) located in the valve body and a valve seat whereby the valve is closed when the valve member abuts the valve seat and is 4 4 open when the valve member is spaced from the seat. C. a ii