WO2000052329A2 - Flywheelstarter/generator for i.c.-engines - Google Patents

Abstract

This invention relates to an electric machine which may act as a (flywheel)-starter-motor, and/or a generator for internal-combustion-engines (called i.c.engines or engines hereafter). A planetary gear/brake/clutch arrangement offers two gear-speeds and a freewheel. Thanks to the freewheel-mode, the machine may be permanently connected to the i.c.engine and is therefore perfectly suited for turbo-compounding, offering a fast shaft to combine an exhaust-turbine with a, preferably, non-turbo compressor. The invention moreover relates to the various practical forms, matching control-devices and auxiliaries which enable the machine to be used in a number of different applications. The electric configuration of the machines used, may differ, depending on the application.

Description

FLYWHEELSTARTER/GENERATOR FOR I.C.-ENGINES

This invention relates to an electric machine which may act as a (flywheel)-starter-motor, and/or a generator for internal-combustion-engines (called i.e. engines or engines hereafter). A planetary gear/brake/clutch arrangement offers two gear- speeds and a freewheel. Thanks to the freewheel -mode, the machine may be permanently connected to the i.c.engine and is therefore perfectly suited for turbo-compounding, offering a fast shaft to combine a exhaust-turbine with a, preferably, non-turbo compressor. The invention moreover relates to the various practical forms, matching control-devices and auxiliaries which enable the machine to be used in a number of different applications. The electric configuration of the machines used, may differ, depending on the application.

On itself the use of flywheels for starting must be considered as public domain, in W.W.II (hand-driven) flywheels where used for starting aeroplane-engines.

For car-starting, patent PCT/NL88/00044 of this author, has many of the features claimed in this patent in common. PCT/NL88/00044 however, describes a double-rotating electrical machine of which the outer-rotor and the inner-rotor are interconnected by the members of a planetary gear. The machine acts as an Electric Differential Torque Converter (called E.D.T.C. hereafter) and the patent describes a number of applications for this machine among which a starter/generator for cars. As turbo-compressors have a narrow speed-bandwidht, the E.D.T.C's main-function in PCT/NL88/00044 is to provide a fast turbo-shaft at more or less constant speed to compensate for the constantly alternating speed of car-engines. The fast shaft in the current patent application offers no constant speed and is therefore better suited for non-turbo compressors.

In spite of its common features like the use of a flywheel and a planetary gear, the machine described here is no torque converter, and as a starter/generator much more straight-forward and more flexible. For the purposes described here, this invention is therefore much better suited, as the E.D.T.C. is unnecessary heavy, complicated and expensive. Even in its most basic form, the E.D.T.C. involves an extra set of heavy bearings, a complicated commutation system, a double tacho-system, an inverter and a microprocessor. Moreover, although with the outer-rotor blocked the E.D.T.C may start as a conventional starter, the system is inefficient as a flywheel starter. Because of its construction, with the planetary gear integrated in the electrical machine, the E.D.T.C. has no possibility of a freewheeling flywheel. Instead, to spin up the flywheel/outer-rotor, the inner-rotor has to rotate in the opposite direction. As the speed of the inner-rotor will be at least 3 times that of the flywheel, the inner-rotor and the sun-wheel quickly reach their upper speed-limit, severely limiting the maximum speed of the flywheel. Therefore said flywheel must be bulky to compensate for its low speed. Also, as the highspeed inner-rotor has considerable inertia, this energy has to be compensated for in the flywheel as it counteracts to the flywheel-movement and its energy will subtract from that of the flywheel once both rotors are connected to the friction-disk.

The E.D.T.C. has no two-speed provision, neither in motor- nor in generator-mode. Also, no practical solution is presented in PCT/NL88/00044 for establishing the need for a flywheel-start on the basis of engine-temperature and/or battery-condition. As for turbine/compressor operation: Lacking a freewheeling flywheel, the E.D.T.C. is unable to effectively preserve kinetic energy for the compressor to close the so called "turbine-gap" at low engine-speeds.

Finally, unlike the E.D.T.C, the current machine can feed high amounts of surplus turbine power back directly to the crankshaft, independent of powering of the inverter or the electrical machine. With the E.D.T.C, inverter-power and the power of the electrical machine will be considerably higher than necessary for starting alone, like in this patent, as it has to be proportional to the turbine-power handled.

Fig 1 shows the basic arrangement of the machine 101 where one side of the rotor is connected to sun-wheel 104 of a planetary gear 105 and the other side of said rotor is connected to flywheel 102. The ringwheel 109 of said planetary gear is connected to a brake, preferably of the tape and drum type in which case said ringwheel preferably is encased in a oilcooled drum 112 around which the braketape 110 is positioned. A servomotor, spindlemotor, or solenoid 111 acts upon said braketape. The free running mode permits the accumulation of kinetic energy in said flywheel, while in brake mode said energy may be released, more or less gradually, to start the engine c.q. permitting a conventional direct start when totally blocked. The outgoing shaft of said planetary gear is connected to planetcarrier 106 and the other side of said shaft is connected to the engine, be it directly or using the usual "Bendix" starter-construction of a splined sheath 1 13 and solenoid 1 14 arrangement, moving gear 107 into contact with engine- fly wheel 108. Fig. 2 shows a construction for the manual operation of the flywheel -starter.

Ringwheel-brake 201 is operated using spring 202 and lever 203 whether or not using a bowden-cable. Spring 202 is situated around rod 205 and may, in rest, permanently engage or disengage said brake, depending on the application. Handle 209. acting on lever 203, has a switch 207 connected to it, to activate the starter and eventual glowplugs. Springloaded securing-pin 206, keeping handle 209 in place once pulled, may be either manually operated or by a solenoid, activated by a centrifugal-switch at max. r.p.m.

As a flywheel-starter-motor the device is very well suited for use with Diesel-engines. Especially at low ambient temperatures these engines demand very heavy starter-motors and big batteries in order to compensate for the combined effects of reduced battery-capacity, low engine-temperature and lower compression-end-temperatures associated with freezing conditions. By storing kinetic energy, discharging the battery with relative low current over a longer period, the device is able to start the i.c.engine immediately. The advantages are clear: Installed battery-capacity may be be minimal and is applied much more favourably, while peak-currents are reduced. The latter is especially important with semi-conductor controlled machines i.e. permanent-magnet machines.

Fig. 3A shows a simple electric circuit for Diesel-engines with traditional manually activated glowplugs. (Dashboard-)switch 301 activates solenoid/startrelays 302 which in turn activates startermotor 303. In rest, contact 305 of relays 304 connects said starter in series with glowplugs 306 with may have a parallel or a series-parallel arrangement and act as current limitter for said starter in order to prevent a to rapid spin-up.

For actual starting said glowplugs are shortcut by contact 305, coming in when switch 307 activates relays 304. A second contact on said relays activates brake-servo 308 blocking the ringwheel-brake. Full electric power is now fed to the starter and. combined with the flywheel energy, applied to the engine. It may be clear this results, even in extreme cold conditions, in a net start-torque which would normally not even be available at optimum conditions. As the engine temperature on itself is a reliable indicator for the need of a fly wheelstart, the machines control-electronics can be easily incorporated in existing temperature-based automatic diesel startcircuits, whether or not with a fixed preglow-timing.

Fig. 3B shows a electronic circuit with a more refined automatic startmode-selector.

Beside engine temperature, battery-condition is tested here as well, both indirectly however. This makes the circuit very well suited for critical applications like emergency-power-generators etc. where battery-condition may be affected by long off-duty-cycles. The circuit is shown here in spin-up mode. Primarily, the engine is started in a direct mode. When relays/solenoid 328 comes in,

(closing the integrated switch 328) the starter and amplifier 321 are powered up. Said amplifier feeds relays 320, closing contacts 320 one of which shortcuts series-connected glowplugs 331. Brake servo 329 comes in and a direct start follows. This start-attempt may be aborted directly or after some revolutions, when the voltage-drop of the battery 330 is to big. As the internal resistance of the battery increases if its (charge-)condition decreases and temperature drops, this comes to expression as a resulting voltage-drop once the battery is heavily loaded, i.e. during the direct-start-mode of a cold engine. As a result of this voltage-drop condenser 323, initially charged under no-load-conditions using 324 and 325, is discharged by circuit 326 and 327, until the voltage drops under the treshold-level of zener 322. Amplifier 321 is now blocked, brake-servo 329 is disengaged and glowplugs 331 series-connected with the starter. This results in a low-current spm-up/preglow period during which the battery-voltage recovers and condenser 323 is gradually charged again, the timing of which depending on battery condition and the values of 325, 323 and 322. Once the voltage over 323 rises again above said threshold, a direct start is once again initiated, now combining the energy accumulated in the flywheel.

Fig. 3C shows a circuit where engine temperature is measured directly, using thermistor 350 and temperature meter 352, already in place in most vehicle-dashboards. Again the circuit is shown in spinup mode. As condenser 353 is only charged via 355 when dashboardswitch 351 is closed, the starter always spins up before starting. The timing before a direct start takes place, now depends on the value of condenser 353 and the actual, temperature based, value of thermistor 350.

It may be clear that the principles used in fig. 3b and 3 c allows for variations depending on the application. One example is for use with gasoline-engines where sparkplug-energy may drop to low levels under adverse conditions. As no (current limiting) preglowing takes place, energy accumulates very rapidly in the flywheel. Starting eventually may be pure mechanical, preserving all battery-power for the sparkplugs.

In all circuits described here a centrifugal switch (not shown here except for 407 in fig.4) may switch off the machine when maximum flywheel-speed is reached. As at this point the battery-voltage very rapidly recovers, a direct start follows almost immediately. With conventional DC-series-motors its increasing impedance with rising r.p.m. (allowing battery-voltage to recover) may offer another reference. The machine may be switched to direct-mode once the (decreasing) voltage over the sparkplugs reach a given value. For manually operated ringwheel brakes a modification of figure 3b or 3c may be used.

Fig. 4a shows shows the relevant part in common. The circuit is shown in the situation where relays 401 is deactivated because of low battery- voltage and its restcontact activates lamp 403. This is a signal to deactivate the ringwheelbrake thereby closing switch 405. When relays 401 comes in again, buzzer 405 sounds as a signal to engage the ringwheelbrake. Fig. 4b shows a tacho-circuit to control the ringwheelbrake-tension. Tacho 420 may be placed to the teeth of the engine-flywheel and its output, rectified by 421, used to control amp. 422 feeding brake-solenoid 423, or a servo- or spindlemotor. As shown, the amplifier delivers full power to said solenoid until, with increasing engine-speed, the tacho-output exceeds the zener-threshold and reduces the power to the solenoid. Alternatively the amplifier may feed a spindlemotor and'or the tacho may be placed on the starter. The spindle-motor overcomes a spring-load and pulse the tape with a tachoregulated force.

In fig. 5 said spindlemotor 501 is shown in a double-function. From its freewheel-middle-position it may act either for the ringwheel-brake or for a tacho-controlled locking device, locking the ringwheel and the planet-carrier of the planetary gear. Using a bowden-cable 502 the spindlemotor can pull a flanged pin 503 through hollow outputshaft 504 against spring 505. Secured to the other end of said pin, through slots in said outputshaft, is the actual locking device 506, fitting in a blank space in the flange of brakedrum 508 when pulled to the left. When the bowden-cable releases, spring 505 pushes 506 back to the right decoupling said gears. The locking construction is very similar to those used for planetary bicycle gearings, and it may be clear that wellknown alternative constructions may be used as well, for example using plate-couplings, to achieve the same result. The resulting two-speed-plus-freewheel machine may be used as a starter/generator and directly coupled to the engine. The two-step gearing allows for high generator-output at all engine speeds and the machine may act as a temporary power booster for extra acceleration by going into motor-mode.

It may be clear that for starter/generator use, preferably brushless machines should be used, ideally with permanent magnets. To overcome the drawback of to high centrifugal forces acting on said magnets the machine may be inverse built. In that case, extra flywheel-mass may be added to the (outward) rotor.

Using a two-quadrant inverter, the machine, due to its fast shaft and flexible coupling to the engine, is perfectly suited for turbo-compounding, feeding surplus exhaust-energy from the engine back to its crankshaft. Fig 6 shows a diagram for this, where machine 601 whether or not using extra step-up gears or a coupling 602 is connected to turbine 603 and a (preferably) non-turbo compressor 604. The use of non-turbo compressor (like Wankel, Roots- and Velox -blowers) have the advantage of a more linear yield and lower speed. By feeding exhaust-energy back to the crankshaft, motor-efficiency may be increased by up to 1 % while the sustained compressor may increase specific power up to 35 % and more over the total bandwidth.

For cars, a problem with direct coupled turbo's lies in the sudden big speed variations while shifting gears. Using multiple tacho's combined with car-management-information like from clutch and accelerator-pedals, a micro-controller, not shown here, is fully able to coordinate the machines gearshifting and inverter-mode with turbo-, compressor- and engine-management whether or not in combination with servo-controlled compressor- put-restrictions and/or wastegates. Therefore, with sudden engine-speed variations the machine immediately goes into freewheel-mode during which the machines flywheel preserves power for the compressor, curing the dreaded turbo-gap by maintaining high compressor yield. In this freewheel-mode the machine may sustain or even increase compressor-speed by going into electric motor-mode. A very fast compressor-acceleration may further be achieved mechanically, by using the machine's first gear with the brake in slip-mode.

Claims

CLADvIS

1 Electric machine for starting combustion engines where one side of the rotor of said machine is connected to the sun-wheel of a planetary gear and the other side of said rotor is connected to a flywheel.

2 Electric machine according to previous claim where the outgoing shaft of said planetary gear is connected to its planetcarrier and the other side of said shaft is connected to the engine, be it directly or using the usual starter-construction of a splined sheath and solenoid arrangement moving a gear into contact with the engine-flywheel.

3 Electric machine according to previous claims where the ringwheel of said planetary gear is connected to a brake, preferably of the tape and drum type which, in free running mode, may permit the accumulation of kinetic energy in said flywheel, while in brake mode said energy may be released to start said engine c.q. permits a conventional direct-start.

4 Electric circuit for a machine according to one or more of the preceding claims where, for diesel-engines, in order to limit the power-built-up in said flywheel during spin-up, said machine may be connected in series with a series-, parallel-, or series-parallel-arrangement of the glowplugs of said engine.

5 Electronic circuit for a machine according to one or more of the preceding claims where, in order to establish the necessity for a flywheelstart and its eventual spin-up time and, for diesels, the preglow-time, engine-temperature and or the voltage-drop of the battery is measured the latter during the first revolutions of a direct start of said engine, preferably using a series-switched zener-diode forming a threshold beneath which said brake is deactivated for spin-up of said flywheel.

6 Electronic circuit according to the preceding claim where, for timing, a condenser is charged and/or discharged by a circuit of two anti-parallel diodes, both connected to the battery via series-resistors, whereby the value of the discharge resistor is chosen to allow for at least several revolutions of said engine during the initial direct start, and the value of the charge resistor is chosen to allow for sufficient spin-up time for said flywheel. 7 Electric machine according to one or more of the preceding claims where, for a double-function as generator said machine is, more or less directly, coupled to (the crankshaft of) said engine and the servo-system allows for a fixation of said planetary gear together with previous measures allowing for a two-speed plus freewheel-mode.

8 Electric machine according to one or more of the preceding claims where the machine may be inversely built and flywheel-mass added to said rotor.

9 Electric machine according to one or more of the preceding claims where the machines rotor is connected to a turbine-shaft, whether or not using extra gears or clutches, whether or not combined with one or more non-turbo compressor(s) on said turbine-shaft.

10 Control-system for an electric machine according to the preceding claim where sudden changes of the engine-speed results in a freewheel -mode of said machine during which a two-quadrant inverter may go into generator or motor-mode to control or boost said compressor-speed and/or the gearing of said machine may be forced in a slipping first-gear mode to mechanically boost said compressor-speed.