WO2006007647A1

WO2006007647A1 - Air starting system

Info

Publication number: WO2006007647A1
Application number: PCT/AU2005/001060
Authority: WO
Inventors: Phillip John Nelthorpe; Graham Vincent Mccullough
Original assignee: Voest Alpine Mining And Tunnelling Pty Ltd
Priority date: 2004-07-23
Filing date: 2005-07-19
Publication date: 2006-01-26

Abstract

A starting system for a combustion engine (2) comprising an electronic control module (3) adapted to govern the speed of the combustion engine and a pneumatic circuit (6) adapted to control the starting sequence of said combustion engine. The pneumatic circuit comprising a receiver (7) and a pneumatic motor (8) for applying a predetermined starting torque to the combustion engine; and a hydraulic circuit (11) comprising a hydraulic motor (15) mechanically coupled to an alternator (12) adapted to provide electrical power at a substantially constant voltage level to the electronic control module. The hydraulic motor being driven hydraulically from a supply header (13) capable of being pressurised while the combustion engine is started.

Description

Air Starting System

TECHNICAL FIELD

The present invention relates to starting systems for combustion engines and in particular to electronically governed diesel engines operated in areas having potentially volatile atmospheres, such as in underground coal mines.

BACKGROUND

Providing sufficient safety features to guard against explosion has long been a problem when operating machinery such as diesel engines and their support systems in volatile environments like coal mines, hi underground or enclosed environments, methane gas concentrations (above 1.25% for example) and volatile dust particulate such as coal dust introduce significant risks to personnel and equipment. Extensive regulatory efforts have been undertaken in various countries, such as the Coal Mines (Underground) Regulation NSW 1999 in Australia or the U.S. Bureau of Mines Requirement in the USA, to impose strict safety requirements on equipment to be used in these hazardous environments.

The starting circuits of electrically governed diesel engines are particularly problematic due to the electrical power required by their governor circuits, hi prior art devices, such as US5528901 (Willis), a battery has typically been used to power the electronic governor until a mechanically coupled alternator takes over electrical power needs. However, in volatile atmospheres, using a battery necessitates explosion proofing such that any spark or thermal effect produced by the battery or its circuitry is incapable of causing ignition of explosive mixtures of methane or other flammable gasses and air. Generally batteries introduce an additional hazard by producing hydrogen gas when being charged. Thus the battery must be designed and maintained to ensure any hydrogen generated is adequately dissipated or charging avoided altogether. In order to avoid the space requirement and cost of including a high power battery, some of the prior art devices utilise hydro - mechanical governors such as in the diesel generator disclosed in International Patent Publication No. WO 85/03546 (Berriman).

For combustion engines in general, prior art devices exist utilising pneumatic starting motors instead of electric motors. For example, RU2120056 (Chekhunov) and EP0784743 (Willis) are both directed to pneumatic starting systems for combustion engines. Additionally, prior art devices include hydraulically driven alternators instead of mechanically driven alternators, such as provided by EP0570754 (Fasola). However, these devices do not overcome the safety hazards associated with operating an electronically governed combustion engine in industrial areas having potentially volatile atmospheres.

The present invention aims at addressing or ameliorating at least some of the aforementioned problems of the prior art.

SUMMARY OF THE INVENTION

The present invention, in a broad form, provides a starting system for a combustion engine comprising: an electronic control module adapted to govern the speed of said combustion engine; a pneumatic circuit adapted to control the starting sequence of said combustion engine, said pneumatic circuit comprising a receiver and a pneumatic motor for applying a predetermined starting torque to said combustion engine; and a hydraulic circuit comprising a hydraulic motor mechanically coupled to an alternator adapted to provide electrical power at a substantially constant voltage level to said electronic control module, said hydraulic motor being driven hydraulically from a supply header, said supply header capable of being pressurised while said combustion engine is started.

Preferably, said hydraulic circuit contains an accumulator that pressurises said supply header during said starting sequence.

Preferably, said hydraulic circuit contains an alternator pump mechanically driven by said combustion engine to pressurise said supply header when said combustion engine is running.

Preferably, said alternator pump has a flow control valve to divert excess hydraulic fluid to a reservoir such that said alternator rotates at a substantially constant rate thereby delivering said substantially constant voltage whilst the speed of said combustion engine varies.

Preferably, a low power battery provides electrical power to support low power circuit functions of said electronic control module.

Preferably, said hydraulic circuit includes a hand pump for charging said accumulator, hi a second preferable embodiment, said accumulator may be charged by a pneumatically driven pump adapted to be driven from said pneumatic circuit, hi a further preferable embodiment, said accumulator may be charged by a pneumatically driven pump adapted to be driven from an external, pre-existing pressurised pneumatic system.

Preferably, said accumulator may be charged by a pre-existing external supply of pressurised hydraulic fluid.

Preferably, said accumulator is charged by a hydraulic system pump mechanically driven by said combustion engine when said combustion engine is running.

Preferably, said combustion engine mechanically drives a hydraulic pump fluidly connected to hydraulic fan motors, said hydraulic fan motors adapted to drive cooling fans for cooling said combustion engine.

Preferably, said starting system prevents starting said combustion engine unless predetermined safety conditions are satisfied at the time of starting.

Preferably, said receiver may be charged by an external, pre-existing pressurised pneumatic system.

Preferably, said combustion engine is a diesel engine.

Preferably, said combustion engine is operated in areas having potentially volatile atmospheres.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

FIG 1 is a symbolic, perspective view of a starting system and a diesel engine according to a first preferred embodiment of the present invention

FIG 2 is a schematic diagram of the hydraulic circuit portion

FIG 3 is a symbolic, perspective view of a pneumatically driven pump which replaces the hand pump shown in Fig. 1 in a second preferred embodiment of the present invention.

BEST MODE OF CARRYING OUT INVENTION

The present invention generally relates to starting systems for combustion engines. A first preferred embodiment of this invention is for the diesel engine 2 shown in Figure 1. Figure 2 provides a schematic view of hydraulic circuit 11. In both figures, like reference numerals refer to the same component, hi the shown embodiment, starting system 1 comprises an electronic control module 3, a pneumatic circuit 6 and a hydraulic circuit 11, which operate in combination to start diesel engine 2. Those components and their operation are described below.

Electronic control module 3 contains circuitry (not shown) to govern the speed of diesel engine 2. Further electronic functions of the electronic control module 3 include establishing failsafe operating modes and providing diagnostic fault codes, both of which are advantageous during improper system operation. When diesel engine 2 is running, alternator 12 powers electronic control module 3 by providing at least one substantially constant DC voltage level.

Pneumatic circuit 6 stores energy in the form of pressurised air in receiver 7. Receiver 7 may be periodically charged by an external, pre-existing pressurised pneumatic system (not shown). This is an advantageous arrangement, as most industrial areas that have potentially volatile atmospheres also have existing pneumatic networks installed in order to drive pneumatic tools and sometimes supply auxiliary breathing systems. The energy stored in receiver 7 is used during the starting sequence to drive pneumatic motor 8, assuming all predetermined safety conditions are met. Where the diesel engine 2 is mounted to a mine vehicle (not shown), predetermined safety conditions might include 'park brake applied' or Operators cab door closed', for example, and prevent air from flowing through pneumatic circuit 6 by closing an associated valve or venting pressure to atmosphere if the predetermined safety conditions are not satisfied. Electronic control module 3 may also prevent energising start solenoid 4 if predetermined safety conditions are not met.

Hydraulic circuit 11 comprises a hydraulic motor 15 that drives alternator 12 during normal operation and starting of diesel engine 2. Hydraulic motor 15 is driven from supply header 13, which has a plurality of pressurising sources interconnected by alternator manifold 23. During the starting sequence, supply header 13 is pressurised by accumulator 14. Whether supply header 13 is hydraulically connected to accumulator 14 is determined by whether sufficient pressure is present in pneumatic line 10 from pneumatic circuit 6 to alternator manifold 23.

Accumulator 14 advantageously stores energy in a pressurised volume of hydraulic fluid. As such, accumulator 14 is able to supply the driving force to hydraulic motor 15 and alternator 12, before diesel engine 2 is running, to provide sufficient electrical power to electronic control module 3. Accumulator 14 is adapted to be charged by a number of sources, including by hand pump 19. When diesel engine 2 is running, accumulator 14 is recharged via supply line 24 from a hydraulic system pump (not shown) mechanically driven by diesel engine 2. In this embodiment, the hydraulic system is a high pressure system, near 2500 psi, used to operate steering cylinders and lift arm functions of machinery (not shown) attached to diesel engine 2.

Alternator pump 16 shown in Figure 2, is mechanically coupled to the rotation of a crankshaft (not shown) of diesel engine 2. When diesel engine 2 is running, alternator pump 16 is supplying all of the hydraulic fluid driving hydraulic motor 15. The voltage generated by alternator 12 is proportional to its rotational speed, which is governed by the speed of hydraulic motor 15. As it is desirable to have alternator 12 generate a substantially constant voltage, , flow control valve 17 is used to divert excess hydraulic fluid delivered from alternator pump 16 to reservoir 18. Thus, even though alternator pump 16 varies speed with diesel engine 2 as the latter meets different operational needs, hydraulic motor 15 rotates at a substantially constant rate. As such, alternator 12 is able to maintain the substantially constant voltage level required to power electronic control module 3.

Referring to Figure 2, hydraulic circuit 11 further supports the cooling system (not shown) of diesel engine 2 in that hydraulic fan motors 22 drive the cooling system's cooling fans (not shown). Hydraulic fan motors 22 are themselves hydraulically driven by hydraulic pump 21, which is mechanically rotated by a coupling to a crankshaft (not shown) of diesel engine 2 when running. Hydraulic pump 21, alternator pump 16, and hand pump 19 take suction from, while flow control valve 17 and hydraulic motor 15 discharge hydraulic fluid to, reservoir 18.

In use, starting system 1 undergoes the following start sequence. Accumulator 14 is charged by hand pump 19, if not sufficiently charged from previous diesel engine 2 operation. When the operator depresses start valve 9, if the predetermined safety conditions are met, pneumatic pressure from receiver 7 is directed to alternator manifold 23 via pneumatic line 10. Alternator manifold 23 opens to hydraulically connect accumulator 14 to supply header 13, thereby rotating alternator 12 through hydraulic motor 15. Alternator 12 supplies electrical current to electronic control module 3. When the output voltage of alternator 12 reaches a predetermined level, in the present embodiment near 24Vdc, electronic control module 3 energises start solenoid 4. Start solenoid 4 opens to allow pneumatic pressure, from downstream start valve 9, to cause pneumatic motor 8 to engage to driveably couple to a crankshaft (not shown) of diesel engine 2. After pneumatic motor 8 is engaged, starter relay valve 5 pilots open to allow pneumatic pressure from receiver 7 to drive pneumatic motor 8, thereby cranking diesel engine 2 and allowing the combustion process to begin.

Once diesel engine 2 is running, the operator releases start valve 9 which causes pneumatic pressure to vent from pneumatic line 10, thereby causing alternator manifold 23 to hydraulically disconnect accumulator 14 from supply header 13. As diesel engine 2 is running at this point, supply header 13 remains pressurised from alternator pump 16. Flow control valve 17 maintains a constant flow to supply header 13 as discussed above, while diesel engine 2 may vary speed as necessary for operation. During normal operation of diesel engine 2, accumulator 14 is recharged via supply line from a hydraulic system pump (not shown) mechanically driven by diesel engine 2. hi this embodiment, the hydraulic system is a high pressure system, near 2500 psi, used to operate steering cylinders and lift arm functions of machinery (not shown) attached to diesel engine 2. hi a second preferred embodiment (not shown), electronic control module 3 may receive supplementary electric power from a low power battery to support low power circuit functions such as warm-up and initialisation self checks, establishing failsafe operating mode, and suppling diagnostic fault finding circuitry for post shutdown analysis. Such a battery is preferably of sufficiently low power to require minimal explosion proofing as applicable in a given hazardous environment, hi the preferred form, the low power battery may be arranged so as to supplement electric power supplied by alternator 12.

Li a further preferred embodiment (not shown), pneumatic circuit 6 may include a compressor, such as a small rotary type air compressor, driven by diesel engine 2 in order to recharge receiver 7 while diesel engine 2 is running. hi a further preferred embodiment, hydraulic circuit 11 may replace or supplement hand pump 19 with pneumatically driven pump 20 shown hi Figure 3. hi alternative configurations, pneumatically driven pump 20 could be driven from pneumatic circuit 6 or from an external, pre-existing pressurised pneumatic system of the industrial area Pneumatically driven pump 20 provides advantages of speed and torque, where hand pump 19 may require significant mechanical advantage to operate. Whilst the above embodiments describe using a pneumatic pressure system, it will be appreciated that pneumatic circuit 6 may just as easily use some other inert gas as its working medium.

The foregoing describes only a preferred embodiment of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention.

The term "comprising" (and its grammatical variations) as used herein is used in the inclusive sense of "having" or "including" and not in the exclusive sense of "consisting only of.

Claims

1. A starting system for a combustion engine comprising:

-an electronic control module adapted to govern the speed of said combustion engine;

-a pneumatic circuit adapted to control the starting sequence of said combustion engine, said pneumatic circuit comprising a receiver and a pneumatic motor for applying a predetermined starting torque to said combustion engine; and

-a hydraulic circuit comprising a hydraulic motor mechanically coupled to an alternator adapted to provide electrical power at a substantially constant voltage level to said electronic control module, said hydraulic motor being driven hydraulically from a supply header, said supply header capable of being pressurised while said combustion engine is started.

2. A starting system for a combustion engine as claimed in claim 1, wherein said hydraulic circuit contains an accumulator that pressurises said supply header during said starting sequence.

3. A starting system for a combustion engine as claimed in claim 1, wherein said hydraulic circuit contains an alternator pump mechanically driven by said combustion engine to pressurise said supply header when said combustion engine is running.

4. A starting system for a combustion engine as claimed in claim 3, wherein said alternator pump has a flow control valve to divert excess hydraulic fluid to a reservoir such that said alternator rotates at a substantially constant rate thereby delivering said substantially constant voltage whilst the speed of said combustion engine varies.

5. A starting system for a combustion engine as claimed in claim 1, wherein a low power battery provides electrical power to support low power circuit functions of said electronic control module.

6. A starting system for a combustion engine as claimed in claim 2, wherein said hydraulic circuit includes a hand pump for charging said accumulator.

7. A starting system for a combustion engine as claimed in claim 2, wherein said accumulator may be charged by a pneumatically driven pump adapted to be driven from said pneumatic circuit.

8. A starting system for a combustion engine as claimed in claim 2, wherein said accumulator may be charged by a pneumatically driven pump adapted to be driven from an external, pre-existing pressurised pneumatic system.

9. A starting system for a combustion engine as claimed hi claim 2, wherein said accumulator may be charged by a pre-existing external supply of pressurised hydraulic fluid.

10. A starting system for a combustion engine as claimed in claim 2, wherein said accumulator is charged by a hydraulic system pump mechanically driven by said combustion engine when said combustion engine is running.

11. A starting system for a combustion engine as claimed in claim 2, wherein said combustion engine mechanically drives a hydraulic pump fluidly connected to hydraulic fan motors, said hydraulic fan motors adapted to drive cooling fans for cooling said combustion engine.

12. A starting system for a combustion engine as claimed in claim 1 , wherein said starting system prevents starting said combustion engine unless predetermined safety conditions are satisfied at the time of starting.

13. A starting system for a combustion engine as claimed in claim 1, wherein said receiver may be charged by an external, pre-existing pressurised pneumatic system.

14. A starting system for a combustion engine as claimed in claim 1, wherein said combustion engine is a diesel engine.

15. A starting system for a combustion engine as claimed in claim 1, wherein said combustion engine is operated in areas having potentially volatile atmospheres.