GB2178797A - Cold starting of diesel engines - Google Patents

Abstract

A device for cold starting of diesel engines comprises a frame 1 on which is mounted an electric motor 2, the motor having an output shaft 3 with a 'Bendix' thread 3a on which is mounted a sprocket 4 engaging a gear 5, which is connectable to a crankshaft extension of an engine by a shaft 6, adapted at its end 7 by e.g. stubs 10 to engage the crankshaft extension. The motor 2 is arranged to be powered by a battery through a switch 16. A hydraulic or pneumatic motor may be used instead of electric motor 2. The motor may drive the shaft 6 through a belt and pulleys and include a uni-directional sprague clutch. Two uni-directional drive transmission elements may be included for safety. <IMAGE>

Description

SPECIFICATION Cold starting of diesel engines This invention relates to a device for use in cold starting of diesel engines, particularly in cold winter weather.

Cold starting of diesel (compression-ignition) engines, particularly in extremely cold weather, presents a problem in that it is the compression ofthe fuel/air mixture in the cylinder, and consequent adiabatic temperature increase which causes igni- tion. If however the initial temperature is too low, due to the intake of su b-freezing air, then the temperature increase in compression may not be sufficientto enable the temperature of the mixture to reach its flash point.

Alternative approaches to the problem are eitherto resort two hand cranking of the engine, if a suitable crankshaft extension is provided, or preheating the fuel/air mixture prior to injection using preheating coils. Engines for use in vehicles and machines used on building and other civil engineering sites are usually adapted for hand starting, and forsecurity and maintainance reasons, batteries which would be needed for preheaters are not provided, so that the preheating option is not available.In normal conditions hand cranking of such engines is quite effective, but in conditions of extreme cold, however hand cranking becomes increasingly more difficultdueto the increase in the viscosity of sump and lubricating oil, thus increasing the resistance ofthe engine, so that momentum cannot be easily built up in the fly wheel ofthe engine and this may not be achieved before physical exhaustion has set in, or patience been lost.

An objectofthis invention is to provideadevicefor cold starting of diesel engines without built in heaters or batteries which is simple and robust in operation and construction, but capable of turning a crankshaft as long as required to build flywheel momentum and for an engine to start and begin running steadily.

According to the invention there is provided a deviceforcold starting a diesel engine comprising in combination anyone or more ofthefollowing:- a) a motorforgenerating torque; b) atransmission assemblyof atleasttwo ele- ments, for reduction of rotational speed and amplification oftorquegenerated by the motor; c) an output shaft connectable to the crankshaft of adiesel enginefortransmission oftorquetosaid crankshaft; and d) the transmission assembly incorporating at least one unidirectional drive element.

The motor is preferably an electric motor, e.g. a standard automobile starter motor connected to a power source such as an electrical battery. The electrical battery and an operating switch may be mounted in a common housing with a self regulating charger; the switch being for example a push button operated solenoid switch which closes the motorcir cuitonlywhilethe button is depressed.

Alternatively, but less preferrably, the motor may be a pneumatic or hydraulic motor, or an internal combustion engine, e.g. petrol fueled. The motorand transmission assembly and output shaft are prefer ably mounted firmly on a portable support, so as to be transportablefrom placeto place, with meanstoen- gage with the machine orvehicle body to hold the support against reaction from the drive.

Preferrablythe motor is a standard automobile starter motor with a sprocket or pinion mounted on a shaft with a 'Bendix' thread to act as a uni-directional drive element and disengage from a gear train when the enginefires and begins to apply torque to the gear train.

A preferred embodiment of device according to this invention for cold starting a diesel engine will now be described by way of example, with reference to the accompanying drawings,wherein: Figure lisa perspective view of the device mounted behind a vehicle powered buy a diesel engine; Figure2 is a rear elevation ofthe deivce; and Figure 3 is a partially cut away view from above of the device.

The device according to the invention for cold starting diesel engines shown in the drawings comprises a supportframe 1 carrying an electric motor 2, having an output shaft 3 which in turn carries a sprocket 4 on a Bendix' thread 3a. Motor 2 is a standard automobile starter motor. Sprocket 4 meshes with a ring gear 5 on a shaft 6 which is adapted at its end 7 to be connected to an extension 8 ofthe crankshaft of a diesel engine, such as may be used as a take-offshaft orfor hand cranking. Gear 5 is covered by a shield 18.

The shaft end 7 is adapted by stubs 10 for connection to extension 8, either directly, orthrough an adaptor (not shown). The form of end 7, or of any adaptor, may be varied as required by the particular model of crankshaft extension.

The motor2 is connected by leads 13, 14tothe terminals of an electric battery (not shown). A push button actuated solenoid operated starter switch 16 is connected into one lead, and is constructed to operate in such a way that motor 2will only be energised while the button is positively pressed by the operator.

Theframe 1 comprises esentiallyan elongate bar, and this has a plurality ofappertures 20 for mounting on a vehicle by means of a rod 21 therethrough, and a post 22 on the vehicle.

In use, for cold starting a diesel engine, the exhaust valve ofthe engine is opened by operating the engine'sdecompression lever. The shaft 6 of the gear 5 is connected to the crankshaft extension 8, and the motor actuated by operation of the switch 16. The motor drivesthe gear 5 through shaft 3 and sprocket 4, and gear 5 drives the crankshaft through shaft 7 and extension 8, thus causing the enginetoturn over and imparting momentumtoitsflywheel.Whenthefly- wheel has sufficient momentum, the exhaust valve is closed to commence the injectionlcompression cycle.

This may be repeated until the engine begins firing.

Sprocket 4 and ring g ea r 5 constitute a two element geartrain which operates to reduce the rotational speed ofthe output from motor 2, with consequent amplification oftorque,the ratio of diameters of said sprocket and ring gear, and theirtoothing, determining the gear ratio in the usual way. The torque must obviously be sufficient to overcome the inertia ofthe crankshaft and parts moved by it such as the piston and flywheel, and the oil viscosity, which may be considerably increased in cold conditions. When the engine starts, sprocket 4 disengages from the gear 5 due to the 'Bendix' thread on shaft 3, which prevents backtorquefrom being applied to motor2andthus prevents damage to the motor.The motor 2 can be operated until the engine fires continuously for a desired time.

The device described is an efficient and more effec tive substitute for hand cranking, but uses the same principle of turning the crankshaft until flywheel momentum is sufficientto enable the engine to fire, including the effect of frictional heating in warming the engine up to flash point. Thetorqueapplied through the shaft 6 is predictably related to the power of motor 2 and the ratio of gear train 4,5 whereas the force applied manuallyvaries between individuals and decreases with increasing fatigue if sufficient momentum cannot be imparted after a few turns.

The device is simple and robust, and does not need any special skill to use, and thus can be used by drivers and operators on building and civil engineering sites in the coldest weather, reducing down time of plant and machinery dueto failureto start in cold weather. The cost ofthe device is estimated to be similarto that of one factory fitted starter, but one device will serve to start as many engines as need to be started, one after another.

The motor is preferrably, as described, an automobile starter motor, but other power sources such as hydraulic or pneumatic motors may be used. The switch 16 may be convenientlyembodied in a portable battery housing which also contains the battery and a self regulating charger, with a 150 amp. connec torforthe motor, of a type which allows easysepara- tion.

In an alternative embodiment, the motor may be connected to the shaft 6 by a V- belt drive, incorporating a uni-directional Sprague clutch. Apulley ofsmal lerdiameteris mounted on the output shaft of the motor, and a pulley of greater diameter on the shaft 6.

The reduction ratio of the transmission assembly thus constituted is equal to the ratio of diameters of the pulleys, as their peripheral speeds are matched by the belt.

Anysuitableform of uni-directional drivetransmission element may be used, and a second unidirectional element may be included as a safetyfeature.

Claims (7)

1. Acoldstarterfordieselengines,comprising:- a) a motorforgeneratingtorque; b) a transmission assem bly of at least two ele- mentsforreduction of rotational speed and amplification oftorque generated by the motor; c) an output shaft connectable to an extension of the crankshaft of a diesel engine, fortransmission of torque to said crankshaft; and d) at least one uni-directional drive element being incorporated in the transmission assembly.

2. Astarteraccordingto claim 1 or2whereinthe motor is an electric motor.

3. A starter according to claim 1 or 2 wherein the motor, transmission assembly and output shaft are mounted firmly on a portable support, so asto be transportable from place to place, with means to engage a machine or vehicle bodyto hold the support against reaction from the device.

4. A starter according to claim 3 wherein the transmission assembly comprises a gear train of at least two gear elements.

5. A starter according to claim 3 wherein the transmission assembly comprises a belt and pulley assembly.

6. A starter according to claim 4 wherein the unidirectional drive element comprises a 'Bendix' thread on the output shaft of the motor, on which a sprocket or pinion forming part of the gear train is mounted.

7. A starter for cold starting of diesel engines, substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawings.