GB2327656A - Electric vehicle with flywheel drive - Google Patents

Abstract

An electric vehicle receives electrical power continuously from a remote source, e.g. from live conductor rails or overhead wire, and comprises an electric motor, a flywheel, means to drive the flywheel from the electric motor, and means to propel the vehicle from the flywheel with or without the electric motor. As shown, the vehicle collects power from the overhead wires 11 by pantographs 12 for electric motor 21, which may be used to drive wheels 22 directly and is used to drive the flywheel 23 via automatic gearbox 24. Flywheel 23 may be used to drive wheels 22 via gearbox 25, independently of or in combination with the electric motor 21.

Description

Tittle: Electric Vehicle Description of Invention This invention relates to an electric vehicle of the type adapted to receive electrical power continuously from a source usually provided beneath or above the vehicle, such as a conductor rail or overhead wire, extending along the path of travel of the vehicle.

Such vehicles are commonly used, both on conventional gauge railways and underground systems, but increasingly are utilised on urban tramway systems and the like, since they provide a relatively quiet transportation system, and one in which no or very few exhaust gasses are emitted to the environment in which the vehicle operates.

Such vehicles generally comprise a conventional electric motor powered by electric current drawn from the live rail or overhead wire, which electric motor drives the vehicle directly, possibly via the intermediary of a gear box, of conventional type.

However, such vehicles suffer from the disadvantage that the power consumption thereof varies greatly during the course of their operation, since more power is required to accelerate the vehicle from rest than is required to keep the vehicle moving at a generally constant speed.

Since many electricity companies impose heavy surcharges on industrial customers when the power demand exceeds a certain threshold, such uneven demand is clearly undesirable.

Furthermore, since the electrical power demand in some circumstances may be very high, the current carrying components of the trackway system, such as, for example, the live rail or overhead wire, must be manufactured to be capable of carrying high electric currents, which increases the cost, both in terms of manufacture and maintenance thereof, considerably.

It is accordingly an object of the present invention to provide an improved electric vehicle which overcomes or reduces the problems outlined above.

According to one aspect of the invention, there is provided an electric vehicle adapted to receive electrical power continuously from a source remote from the vehicle, the vehicle comprising an electric motor, a flywheel, means to enable the flywheel to be rotated by the electric motor, and means to permit the flywheel to propel the vehicle, in combination with the electric motor or independently thereof.

Preferably, the electric motor is adapted to propel the vehicle.

Preferably, the electric motor is continuously driven by the electrical power, and conveniently, the electric motor runs at a generally constant speed.

Preferably, the electric motor is linked to the flywheel via the intermediary of a gear mechanism such as a gear box, conveniently an automatic gear box, such that the amount of energy provided to the flywheel from the electric motor may be varied as required.

The flywheel is preferably adapted to rotate at at least 1000 rpm, and preferably is able to rotate at at least 2000 rpm, conveniently having a revolution rate of about 4000 rpm or more.

Similarly, the flywheel may be capable of storing approximately 1 kWh of electrical energy, and preferably, is able to store at least 2 kWh, conveniently 4 kWh of electrical energy or more.

Thus, rotation of the flywheel at a generally constant rotational velocity may be maintained by application of varying amounts of power from the electric motor via the gear mechanism.

The drive means may be operative only at certain times to drive the vehicle, such as, for example, when the vehicle accelerates from rest, or at other times when a relatively large amount of power is required.

There is preferably provided a second gear mechanism between the flywheel and the driven wheels, such that relatively quick acceleration of the vehicle may be obtained, preferably using energy stored in the flywheel, but also so that the vehicle may travel, once moved from rest, at a relatively high speed.

Preferably, there is provided brake means operative, on deceleration of the vehicle, to convert kinetic energy due to movement of the vehicle to rotational kinetic energy stored in the flywheel.

Such brake means, known conventionally as regenerative brake means, provide that as the vehicle slows, energy is provided to the flywheel, which energy may subsequently be used to cause the vehicle to accelerate or to maintain a generally constant speed.

The invention provides advantages over electric vehicles currently known in that excessive electrical power consumption over relatively short periods of time is obviated, which not only has economic advantages as previously described, but also, in that a lighter electric motor may be utilised than would otherwise be necessary, and that less heavy duty current carrying components are required on the transport system since the maximum electric current drawn is less than is the case when no flywheel is utilised, and no energy can thus be stored.

The invention will now be described in greater detail by way of example only, by reference to the accompanying drawings, wherein FIGURE 1 is a side view of one type of electric vehicle in accordance with the invention, and FIGURE 2 is a schematic illustration of the means by which the vehicle is powered.

Referring to Figure 1, there is shown an electric vehicle 10 adapted to receive electrical power from conductor wires 11 provided above the vehicle, by use of pantographs 12. The vehicle 10 comprises wheels 13 adapted to run on tracks 14, in conventional manner.

Referring to Figure 2, the means by which the vehicle 10 of Figure 1 is powered is shown in schematic form.

Electrical power from an electrical power source 20 is fed to an electric motor 21 in conventional manner, such as by use of the pantographs 12 shown in Figure 1.

The electric motor is connected to the vehicle drive wheels 22 directly, such that in one mode of operation, the electric motor alone is used to drive the vehicle. It will of course be appreciated that there may be provided a gear mechanism such as an automatic gear box between the motor and the drive wheels, in conventional manner.

The electric motor is connected to a flywheel 23 in a manner such that if it is desired, some of the power produced by the electric motor may be provided to the flywheel rather than directly to the vehicle drive wheels.

There is provided an automatic gear box 24 between the motor and the flywheel so that the amount of power given to the flywheel may be varied.

The flywheel is connected to the vehicle drive wheels 22 in a manner such that if desired, some of the energy stored in the flywheel may be used to propel the vehicle, in conjunction with, or in place of, the electric motor.

Thus, in use, the vehicle may be propelled as follows: Initially, the electric motor is used to power up the flywheel, conveniently to a revolution rate of about 4000 rpm, which in the preferred embodiment equates roughly to 4 kWh of electrical energy stored therein. It will of course be appreciated that by alteration of the mass and radius of the flywheel, the amount of energy stored therein may be varied as desired. Additionally, it will be appreciated that greater revolution rates may well be possible.

Once the flywheel has attained its maximum rotational velocity, some of the energy stored therein is transmitted to the vehicle drive wheels via the intermediary of a gear box 25, which enables the vehicle to accelerate from rest relatively quickly. It will be appreciated that during such acceleration, the amount of electrical power drawn from the electrical power source remains constant, and there is thus no excess power consumption caused by the acceleration, which would be the case if a flywheel were not used.

Once the vehicle is travelling at a desired velocity, with no further acceleration required, it will be appreciated that the amount of power required to maintain the velocity is less than that required to attain it, and the electric motor may then be used directly to propel the vehicle, without the need of the intermediate flywheel. In fact, power may be additionally provided to the flywheel at this stage, so that it may be powered up for subsequent use when the vehicle is required to accelerate once again.

The vehicle is provided with a re-generative braking arrangement such that when it is desired to slow the vehicle, some of the kinetic energy of the vehicle may be put back into the flywheel, in generally conventional manner.

The vehicle provides advantages over those currently known in that the electrical current drawn from the power source is constant, thus removing the possibility of an excess amount of power being drawn, which may give rise to a heavy surcharge, as explained above.

Furthermore, since the amount of current drawn is relatively low, the current carrying components of both the vehicle and the trackway system need not be manufactured so as to be able to carry high electrical currents, which reduces both manufacturing and maintenance costs.

The features disclosed in the foregoing description the following claims or the accompanying drawings, expressed in their specific fonns or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, or a class or group of substances or compositions, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (13)

1 An electric vehicle adapted to receive electric power continuously from a source remote from the vehicle, the vehicle comprising an electric motor, a flywheel, means to enable the flywheel to be rotated by the electric motor, and means to permit the flywheel to propel the flywheel, in combination with the electric motor or independently thereof.

2 A vehicle according to claim 1 wherein the electric motor is adapted to propel the vehicle.

3 A vehicle according to one of claims 1 and 2 wherein the electric motor is continuously driven by the electrical power.

4 A vehicle according to any one of the preceding claims wherein the electric motor runs at a generally constant speed.

5 A vehicle according to any one of the preceding claims wherein the electric motor is linked to the flywheel via the intermediary of a gear transmission mechanism.

6 A vehicle according to any one of the preceding claims wherein the flywheel is adapted to rotate at least 1000 rpm.

7 A vehicle according to claim 6 wherein the flywheel is adapted to rotate at at least 2000 rpm, preferably 4,000 rpm or more.

8 A vehicle according to any one of the preceding claims wherein the flywheel is capable of storing at least 1 kWh of electrical energy, preferably at least 2 kWh, preferably 4 kWh or more.

9 A vehicle according to any one of the preceding claims comprising a second gear mechanism between the flywheel and the driven wheels of the vehicle.

10 A vehicle according to any one of the preceding claims comprising brake means operative on deceleration of the vehicle to convert kinetic energy due to movement of the vehicle to rotational kinetic energy stored in the flywheel.

11 An electric vehicle constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.

12 A method of operating an electric vehicle when carried out substantially as hereinbefore described with reference to the accompanying drawings.

13 Any novel feature or novel combination of features hereinbefore described and/or shown in the accompanying drawings.