Engine starter
The starter or starter is an auxiliary unit for starting internal combustion engines . Manual starting procedures are also described here, which are usually not referred to as starters or starters .
Purpose and requirements
Combustion engines and gas turbines , in contrast to steam engines and electric motors , cannot deliver any torque when they are at a standstill and therefore cannot start up themselves. Combustion engine or gas turbine must be accelerated to a minimum speed (ignition speed) from which the combustion process in the machine continues to run independently. In the case of an internal combustion engine, this means that the energy gained from the combustion must continue to drive the engine after the first ignition until the next ignition and combustion takes place. Below the ignition speed, too much of the air (or mixture) to be compressed and too much heat escape via the combustion chamber walls (mainly piston crown and cylinder head) at the piston ring impact and possibly valves. Both of these reduce the temperature in the combustion chamber so that a proper combustion process cannot take place.
This article does not go into the fact that the engine must be brought into a state in which it can run and start before starting. These include a. that the machine must be technically in order, starting limit temperatures are observed, the rotational resistance is not too great (machine disengaged and, if necessary, decompression switched on), fuel supply and possibly ignition switched on, throttle lever and possibly choke or starting excess quantity have been brought into the correct positions. From the size of a typical locomotive engine, the engines must be preheated (approx. 40 ° C to operating temperature) and the oil pressure must be built up before starting.
Attachment to the engine
Installation close to the engine
Often the simplest form is to mount the starter directly on the crankshaft. A separate shaft bearing is not required and usually no separate housing for the starter. The disadvantage is that a very high torque has to be applied in order to overcome the starting resistances of the engine. For this reason, the attachment was previously only used on very small engines. Today, however, it is used again in hybridized car engines because the electric machine there has a very high output so that the vehicle can also be driven electrically.
Pinion starter
The most common attachment today is that the starter engine drives the ring gear on the flywheel of the internal combustion engine via a pinion on its shaft . This typically results in a reduction ratio of 1:10 or greater, so that the starter can be designed correspondingly smaller. With this arrangement, the starter cannot be used to recharge the memory (battery). For larger starters and motors, mounting flanges standardized in accordance with SAE dominate, while proprietary connections are dominant for passenger cars and smaller motors.
transmission
The starter can also be attached to the engine via a gear unit (usually belt drive ), whereby the starter is typically not decoupled from the engine when the engine is in operation, i.e. it runs permanently. This requires lower reduction ratios than with the pinion starter so that the speed in the starter does not get too high when the engine is running.
Special designs
Special designs, e.g. B. compressed air starting via the cylinder, often require a structural adaptation of the engine to this starting method, z. B. an additional valve in the cylinder head.
Manual starting procedure
Cranking and starting the crank
Probably the oldest starting method is turning an engine directly by gripping the spokes or the rim of the flywheel, but this method quickly reached its limits: The engines became larger and more powerful (which increased the starting resistance to be overcome), but at the same time more compact and lighter (thus also with lighter flywheels). In addition, the flywheel became increasingly difficult to access or completely inaccessible. Nevertheless, the cranking has been preserved as a crank start:
- The starting crank was developed so that you no longer have to reach into the flywheel, which is often difficult to access and rotating during operation, with your hands. This was soon tracked into the engine using a special claw. It is essential that the starting crank cannot disengage while the motor is starting, but that it is reliably disengaged ("ejected") after the motor has started.
- The cranking device no longer acted directly on the crankshaft, but via a reduction gear. This enables a higher speed to be achieved on the crankshaft. In the case of small diesel engines, the camshaft was turned on because this provided the required gear reduction to the crankshaft with practically no additional construction effort.
- A decompression device was introduced for engines with high compression resistance (high compression as in diesel engines) .
- In the commercial sector, the employers' liability insurance association stipulated sufficient accessibility to the pivot point, e.g. B. Starting shaft min. 600 mm above the operator's location.
Nevertheless, safe turning requires a certain understanding of both the designer and the operator:
- The actually required large flywheel (weight and diameter) is contrary to the desired compact dimensions and a low price. In addition, z. For example, suitable measures can be taken to prevent the motor from starting "backwards", the offset of the crank must be adapted to the motor, etc.
- The operator must stand securely to the side of the crank handle and be able to push the crank handle away from him with his full body weight when it is pointing upwards.
- The compression resistance during cranking cannot be overcome by force, but only by sufficient speed at the time of the first compression (not sometime before) and the energy then stored in the flywheel. Incorrect operation was only avoided with the (speed-controlled) fully automatic decompression from the 1990s.
- Start pilot and other prohibited aids can lead to engine damage and uncontrolled pre-ignition.
These errors led to the dreaded kickback of the motor and the crank handle. In order to avoid injuries to the thumb or wrist, the " monkey grip " was recommended for grasping the cranking crank until in the 1980s professional associations required a motor-side protection device in the commercial sector. This requirement made the crank start so expensive that it was gradually replaced by a reversing start and an electric start.
In the motor vehicle sector, vehicles with a starting crank (as a reserve and for maintenance) were still produced after 1945: VW Beetles and derivatives; Renault R4 , Dauphine ; also jack crank: Citroën 2CV .
Rope start
Rope start is a simple starting method that copes very well with small centrifugal masses and was therefore widespread until reversing start and electric start (outside Germany) were widespread. The low cost of the engine and starting device is offset by very demanding operation with a higher risk of injury.
Reversing start
The reversing starter is the most common, simpler alternative to an electric starter today. As with other manual starting methods, you save not only the starter itself, but also the ring gear, alternator, battery and wiring. In the case of air-cooled engines, there is often a simpler design for the flywheel. This concerns acquisition costs, maintenance effort and - particularly important for mobile devices - weight.
Kickstart
The kick starter is mainly used on motorcycles and its function is similar to the reversing start.
Power starting systems
In contrast to the manual or manual starting methods, the term force starting devices is sometimes used. This refers to all processes in which the energy for starting the engine is made available from a memory at the moment of the starting process. Which form of energy is used is irrelevant (mechanical, chemical, etc.), just as this storage device is recharged. The systems typically consist of the starter itself, an energy store, a controller and a device to recharge the store.
Electric starter
Thrust armature starter
The thrust armature starter is probably the oldest type of electric starter and is now only used for increasingly larger outputs. Externally it can be recognized by the lack of a magnetic switch and a cap at the rear end that protrudes laterally over the actual starter housing compared to the thrust screw drive starter.
In its simplest form, the starter shaft, pinion and armature are firmly connected to one another, are axially displaceable in the starter housing and are drawn in in the rest position by spring force. For the starting process, the armature is pushed forward against the spring force so that the pinion engages in the ring gear. In its end position, the armature closes a contact for the starter current and the starter starts to turn and starts the engine. Then the armature is pushed back into the rest position by spring force and the flow of current to the starter is interrupted. In this simple form, the armature is moved purely mechanically by the operator; in a motor vehicle this was the start pedal, which acted on the rear end of the starter shaft via a lever mechanism. The tooth flanks of the pinion and the ring gear would have to be beveled, otherwise in the worst case the pinion could not mesh (tooth on tooth). There was no freewheel, so the engine took the starter shaft with it until it spun out on its own.
For more than 5 decades, however, the starters have been electrically controllable and are significantly more complex: To move the starter shaft, a feed solenoid is located on its rear end under the hood mentioned above and replaces the mechanical actuation. A relay and a step switch are also located under this hood. The stator has a series winding for starting and an additional auxiliary winding for engaging the starter. Furthermore, the pinion is now connected to the armature shaft via a multi-plate clutch. The relay is activated by the start command ( terminal 50 ) and releases the current from the battery (terminal 30) to the auxiliary winding of the stator and the feed magnet on the starter shaft, which flows through the starter rotor to ground (terminal 31). The starter shaft is turned slowly, closing the multi-plate clutch and taking the pinion with it. At the same time, the starter shaft with pinion is pushed forward by the feed magnet for meshing. If the pinion is meshed to the end position, the step switch switches the current flow from the auxiliary to the main winding of the starter motor. Due to the higher torque, the starter can now start the combustion engine. If the start command is canceled, the starter is completely de-energized and the starter shaft is pushed back into the rest position by spring force. If the pinion is still meshed when the engine is starting, the multi-plate clutch between the pinion and the starter armature opens and prevents the starter from being carried along and destroyed.
The meshing is done cleanly and quietly, as the pinion is not yet rotating or is rotating slowly. Even with today's designs, the pinion is not necessarily disengaged when the motor is starting, the construction effort is relatively high.
Bendix starter
At the time, the Bendix starter offered the advantage of automatically and compulsorily disengaging the pinion from the ring gear while the engine was running at a cheap price. Due to its low price, it is still used today on very small and cheap gasoline engines, e.g. B. for lawn mowers. Bendix starters are easy to identify by their cylindrical housing without a magnetic switch next to them.
On the starter shaft there is a thread on which the pinion runs as a traveling nut (the Bendix drive). The pinion is normally held in the starter motor in the rest position by a spring. If the starter is switched on (and thus the rotor is accelerated strongly), the pinion is driven out of the starter by its inertia on the thread and meshes with the ring gear. As soon as the starter is switched off, the spring pushes the pinion back into the rest position. When the engine starts up and drives the starter pinion, this forcibly drives the pinion out of the ring gear.
The Bendix starter does not have an integrated relay to control the high starter current, so it requires an external relay or a heavy-duty starter switch and / or relatively long starter cables. The pinion is thrown against the ring gear in a relatively uncontrolled manner and can easily not mesh, the starter and pinion then continue to turn, the pinion grinds on the flank of the ring gear. This requires careful machining of the tooth flanks of the pinion and the ring gear, but both wear out quickly. Successful as well as faulty tracking are uncomfortably loud.
Thrust screw drive starter
Since around the 1960s, the thrust screw drive starter began to dominate the competing types Bendix and thrust armature because it combined the advantages of both types: Reliable tracing when the internal combustion engine starts up quickly, with controlled, safe, low-wear and low-noise tracing without significant wear. The two housing cylinders lying next to each other are characteristic, the smaller one being the magnetic switch .
The axially displaceable pinion (item 2), which is held in the starter motor by spring force, sits on the starter shaft . If the magnetic switch is activated (usually by the ignition lock ), a relatively small current flows through the winding of the magnetic switch and pulls its armature in against a spring force. The lever moves the pinion towards the ring gear . The current then flows through the main winding of the starter, causing it to rotate slowly in order to support the engagement. In the end position of the magnet switch armature, the pinion is engaged and a contact is closed in the magnet switch, with which the magnet switch is switched to the holding winding and the current for the starter motor (items 3 - 5) is released. When the start button or the ignition key is released, the power supply to the magnetic switch is interrupted, its armature is pushed into the rest position by spring force, the current flow to the starter motor is interrupted and the pinion is disengaged from the ring gear. A freewheel between the pinion and armature shaft of the starter prevents the starting internal combustion engine from taking the starter motor with it and damaging it via the still engaged pinion. The axial displacement of the pinion on the starter shaft can be designed as a screw thread (see picture of the dismantled starter). This supports the freewheel and the pinion forcibly disengages when the internal combustion engine starts. However, this is not a mandatory part of the concept, the push- screw drive starter refers to the fact that the starter is rotated when the pinion is advanced in order to support engagement.
- Since about 1980 you could use engines from z. B. Mitsubishi see early representatives of the countershaft starter . The spur gears used on these starters lead to significantly higher forces within the gearbox than on the planetary gears used later, but enabled smaller (and therefore cheaper) starter motors than with the direct drive that was common up until then . In particular compared to today's starters with planetary gears, the starters are very short and can be easily recognized by the starter motor outside the alignment of the pinion shaft. The production was probably limited to Japan.
- From around the turn of the millennium, high-quality permanent magnets became available and starters gradually switched from series motors to permanent magnet motors .
- In the 2010s, starters were increasingly converted from direct drives to countershaft designs with planetary gears. The coaxial design of the planetary gear and the smaller motor made possible by the reduction mean that these starters in the starter housing are a little slimmer (and a little longer for small powers).
The on- board electrical system voltage influenced by the power requirement of the starter is standardized as a so-called starting curve .
Shuttle starter (Lanz Bulldog)
The pendulum starter or pendulum starter is used to start the Lanz single-cylinder engine and was specially developed for this purpose by the Lanz and Bosch companies. Except for the freewheel, the mechanical structure is almost identical to the push-screw drive starter .
During the starting process, the pendulum starter turns the single-cylinder engine until the maximum permissible starter torque is reached due to the compression before the top dead center is reached. At this point the pendulum starter automatically changes the direction of rotation. Together with the previously applied compression power, supported by the large flywheel, the further power of the pendulum starter causes the process between the dead centers to rock, which is repeated until the engine ignites. Since the pendulum starter does not have to be able to turn the engine past dead center during the starting process, relatively small starters and batteries (12 volts , 56 ampere hours ) are sufficient.
Starter generators
Starter generators work as an electric motor (starter) when the engine is started and as a generator ( alternator ) when the internal combustion engine is running . For example, an earlier common DC generator was equipped with an additional series winding that could be used to start the internal combustion engine. As soon as the engine was running, the normal shunt winding was switched over to charge the battery. DC alternators had very low outputs (up to approx. 15A). so that the starting torque was very low despite the series connection: It was sufficient for small two-stroke engines, but even the smallest diesel engine needed decompression to make it easier to start. With the increasing power requirements for engines and on-board electrics, starter generators and direct current alternators died out.
Hybrid cars have been available since around the 2010s . The powerful electric motor for electric driving and recuperation can also be used, if the drive train is designed accordingly, to start the engine and supply the electrical (low-voltage) on-board network. You save on the ring gear, starter and alternator (costs, weight, installation space) and the loud noise caused by the pinion and ring gear when starting. This development was made possible by the modern semiconductor technology used today instead of the earlier direct current technology.
Dynastart
The Luma-Werke in Stuttgart manufactured a starter generator mounted on the crankshaft for DKW under the brand name Dynastart from 1930 . From 1934, Siba , taken over by Bosch in 1957 , built the Dynastart machines for DKW. The design was later used in the AWZ P70 , DKW F8 , BMW Isetta , BMW 600 , Heinkel Cab , NSU Prinz , Goggomobil , Messerschmitt Kabinenroller , Steyr-Puch Haflinger and from 1969 in the Vespa 50 Elestart. The two-stroke engines often used in small vehicles have the property that they can run backwards if they are started in the appropriate direction of rotation. By simply reversing the polarity of the starter generator, one transmission reverse gear could be saved. At least Bosch delivered the light starter in the form of a direct current generator, which was connected to the engine via a belt drive. This was used by Steyr ( Type 50/55 Baby , Type 200 and Haflinger SUV ), among others .
Today the brand name DynaStart is used by ZF Friedrichshafen for modern crankshaft starter generators based on the principle of the permanent magnet synchronous machine .
Crankshaft starter generator
The crankshaft starter generator (KSG or ISG) is mounted directly on the crankshaft . Due to the omitted alternator and since the ancillary units of the internal combustion engine have to be electrified for sailing or operation as an electric car, a belt drive can be dispensed with. The starter generator sits i today. d. Usually on the transmission input shaft and causes a few centimeters of additional length in the clutch housing. To avoid this with transverse installation, the starter can also be mounted on the gearbox in the form of a power take-off.
Starter generators for aircraft engines ( TL and PTL engines ) also work according to this principle.
Belt-driven starter generator
The belt-driven starter generator (RSG, formerly light starter) is connected to the engine with a similar functionality via a belt drive; normally only another belt tensioner has to be used, which tolerates the different pulling direction during the starting process. The disadvantage is that a real hybrid operation (not mild hybrid or stop-start) is hardly possible: When recuperation or electric driving, the engine of the engine is always dragged along.
This system is used for B. as mild hybrid or stop-start in the Daimler (Smart MHD BR451) .
Air starter
Pneumatic starters (colloquially: compressed air starters) are preferred where electric starters cannot be used due to their (insufficient) power or other operating conditions. Compressed air is used as the energy carrier, but many other gases are theoretically possible. Pinion starters are used on up to medium-sized motors, which are therefore similar to electric starters. Large and largest diesel engines, e.g. B. in ships, are started by controlled feed into the combustion chambers.
Compressed air starters as pinion starters have the same structure as electric starters, except that the electric starter motor is replaced by a pneumatic one. The compressed air supply must also be controlled (solenoid valve instead of relay) and the pinion must be engaged and disengaged. Use in an explosive environment requires additional measures, including a starter pinion made of brass (no sparking) and z. B. nitrogen as a pressure medium.
In the oldest and simplest version of a compressed air system, only one cylinder head was equipped with a manually controlled compressed air valve. With the help of a heavy crowbar or the like, the combustion engine for this cylinder and the desired direction of rotation was set to shortly after TDC (top dead center) . After the other start preparations, the compressed air valve was opened briefly in order to set the motor rotating. Due to the flywheel, it continues to turn and starts running. When the engine is running, the compressed air valve is occasionally opened manually so that combustion gases (possibly via a cleaning stage) can flow back into the compressed air reservoir.
Modern engines with compressed air supply via the cylinder head have a compressed air valve on each of several cylinders, which are controlled via an additional camshaft during the starting process. The camshaft takes on the role of the operator from the above. simple arrangement. In order to enable the engine to start in both directions of rotation, the starting camshaft can be "shifted", or the normal camshaft in the case of four-stroke engines or controlled two-stroke engines. To start it up itself, compressed air is fed to the manifold to the compressed air valves, the valves open and close when the piston of the respective cylinder is in the correct position. As soon as the engine starts up, the compressed air supply to the collecting line is shut off and the compressed air valve remains closed.
Smaller engines with compressed air starting often have an attached air compressor, as is also required for the braking system of trucks. In the case of large engines, the necessary auxiliary units, including the compressed air generation, are driven by their own engines; several redundant systems are required on seagoing vessels.
Hydraulic starter
Hydraulic starters are pinion starters and have the same structure as electric starters, except that the electric starter motor has been replaced by a hydraulic one. There, too, the hydraulic oil supply must be controlled (solenoid valve instead of relay) and the pinion must be engaged and disengaged.
Spring-operated starter
Spring-loaded starters are pinion starters, the housing is relatively large in diameter and length, which is why installation problems can occur despite the same flange mounting on the motor. The energy is stored in the spring package inside the starter.
On the starter shaft there is a pinion and a steep thread on which a traveling nut runs. The starter shown here also has the large bevel gear of a bevel gear at the rear end of the starter shaft, the mating gear sits on the tensioning shaft (the hexagon in the picture). The clamping mechanism is locked into place by the silver push button and z. B. be tensioned with a crank, the spring assembly. First the pinion meshes with the ring gear, then the motor is turned backwards a little. A mark appears on the viewing window when the spring assembly is panned. The motor is now ready to start, it can now be triggered using the lever with the black button, the spring assembly relaxes and thereby drives the motor, and finally the pinion is disengaged from the ring gear.
Spring-loaded starters are used as a power-operated emergency start system when (temporarily) no electricity is available for the electric starter. This is why they are often installed as a second starter on the engine. A tensioned spring-loaded starter blocks the motor so that it cannot run and cannot be started in any other way. If a tensioned, dismantled starter is triggered without a load, this at least leads to self-destruction of the starter; there is also a risk of injury due to the pinion rotating unexpectedly with great force.
Flywheel starter
Flywheel starters use a large, rapidly rotating flywheel mass that is connected to the engine via a non-positive coupling during the starting process in order to take it along.
The flywheel can rotate permanently (emergency power generator, uninterruptible emergency power supply) or it can only be brought up to speed during start preparation. It is irrelevant how the flywheel is driven. This can be a very small electric motor, which in continuous operation has to be able to overcome little more than the bearing resistance (more when accelerating). However, a person can also slowly accelerate a flywheel using a crank drive, if necessary with a variable reduction ratio, and then start very large motors with it. A well-known model with a crank-operated flywheel starter was the DB 605 aircraft engine . The flywheel can rotate with the engine during operation, which improves the concentricity.
Starting with a small combustion engine
One way to start a large engine is to first start a much smaller engine in order to start the large engine. This technique was used to a greater extent in agricultural machinery built in the former Soviet Union . For example, the T-150K or Kirovets K-700 tractors have such starters, as do Soviet chain tractors such as the Stalinez-80 or the Stalinez-100 . Starting in the 1930s, American construction machinery manufacturer Caterpillar installed such starter engines in its large-volume diesel two-stroke engines on bulldozers (e.g. CAT D3) for decades. Gasoline or diesel powered two-stroke engines were preferred , which were started by means of a cable pull or also electrically, in order to then start the large diesel engine. In the case of water-cooled starter motors, the cooling circuit of the starter motor was partially connected to that of the large motor. Some of the hot exhaust gases from the starter engine were also routed to the intake tract of the large diesel engine in order to preheat its intake air for a safe engine start, especially at low outside temperatures.
The jet engines of the Me 262 were also started with a 250 cm³ boxer engine, which was installed in front of the engine in the cone of the air inlet.
Pyrotechnic starter
A pyrotechnic propellant charge forces an enlargement of the combustion chamber due to the explosively rapid pressure increase during combustion, usually a piston in a cylinder is driven outwards. The duration of the starting process is therefore limited to the time until the piston has completed its stroke. For a new start attempt, the piston (with the motor) must be manually returned to the start position and a new pyrolytic charge inserted.
Ignition fix
Under the brand name Zündfix there was / is a pyrotechnic starter that is mounted on the cylinder head of the engine. This usually requires a specially machined cylinder head into which this starter is screwed. This could be equipped u. a. of Deutz engines of series FL410 / D and FL912 . In addition to the other starting preparations, the corresponding piston is turned to shortly after TDC (top dead center) to start the engine , an ignition capsule is inserted into the starter and hit on the head of the starter with a hammer. Inside the starter, the primer ignites, drives the piston of the engine down and starts the engine.
The system obviously worked well with pre-chamber engines as well. Another advantage was that the engine could be prepared for the triggering hammer blow in favorable weather conditions, so that the engine could be started quickly with a single hammer blow in bad weather.
Coffman starter
The Coffman starter was primarily used in aircraft engines in the 1930s. The functional principle is based on a cartridge filled with a pyrotechnic propellant charge .
After ignition, the gases produced during combustion drive a piston that is mounted in a cylinder with a thread similar to a screw with a steep pitch . This causes the piston to rotate, which is transmitted to the crankshaft via gear wheels.
The advantages were that
- no cranking was necessary to start, which was a safety gain should it come to a kickback. As with the electric starter, this also eliminated the need for an auxiliary team to rev the engine by cranking or, in the worst case, tearing the propeller, either by hand or by pulling a cable.
- the start was sometimes faster because the propellant charge immediately transferred a lot of power, while the low human power meant that large engines only gradually got going.
- no heavy battery was required for an electric starter, which was particularly beneficial for fighters, which were more maneuverable due to their lower weight.
The main disadvantage was the one-time use starter cartridge that was necessary for each start-up attempt. The engine rotation by the starter only lasts for a few revolutions, so that poorly starting engines often require several attempts to start with the corresponding number of starter cartridges.
The Coffman starter was z. B. used in some versions of the Supermarine Spitfire and the F4U Corsair .
The starting process with Coffman cartridges was used dramaturgically in the film The Flight of the Phoenix from 1965 and its new production from 2004.
literature
Reference books
- Jürgen Kasedorf, Richard Koch: Service primer for vehicle electrics . Vogel Buchverlag, Würzburg 2001, ISBN 3-8023-1881-1
- Rudolf Hüppen, Dieter Korp: Car electrics all types . Motorbuchverlag, Stuttgart, ISBN 3-87943-059-4
Technical brochures
- Bosch Technical Instruction Electrical Starting Systems. Robert Bosch GmbH, Stuttgart, VDT-UBE 501/1
Web links
Individual evidence
- ↑ Dauphine classic car parts
- ↑ Kineteco Spring Starters - manufacturer's website , May 14, 2020.
- ↑ Dick, Patterson, Perkins, Simsa: Classic fighters , HEEL Verlag GmbH 2000, p. 129, ISBN 3-89365-847-5 .