DRIVE SYSTEM

Abstract: A drive system for electrically powered vehicles where a specifically shaped flywheel (22) is driven by a motor (20). A friction wheel (26) engages the flywheel (22) to provide the driven output. The flywheel (22) is preferably of a concave conical shape with the wheel (26) adapted to be moved angularly thereon to vary the transmission ratio.

Description: DRIVE SYSTEM The present invention relates to a drive system and relates parti-cularly, although not exclusively, to a drive system for electric powered vehicles. With the dwindling supply of fossil and related fuels, electric vehicles are being proposed and used in an attempt to reduce our dependence on the internal combustion engine. Electric vehicles have found favour in city and suburban routes where their lower maximum speed is not a handicap. Although electric vehicles have many advantages e.g. low runn¬ ing cost, virtual absence of pollution and easy recharging, their use in "stop-start" motoring is limited. Frequent "starting up" and accelerating of an electric motor driven vehicle continually places a high energy drain on a conventional lead-acid battery and accordingly the discharge efficiency of such batteries is severely reduced and may restrict the range of the electric vehicle by up to 66%. It is an object of the present invention to provide a drive system for electric vehicles which will increase the operating range of an electric vehicle when used in frequent "start-stop" or commuter duty. A further object of the invention is to reduce the number of lead-acid batteries required to supply power to an electric vehicle and to reduce the size of the electric motor driving the vehicle. According to one aspect of the present invention there is provided a drive system or a vehicle, including a flywheel adapted to be motor driven and a transmission including a wheel adapted to be driven by the flywheel by frictional engage¬ ment of said wheel with a face of said flywheel. OM The flywheel is preferably connected to an electric motor, said wheel and said flywheel being adapted to be moved relative to one another to vary the transmission ratio. The preferred shape of the flywheel is concave conical. In order that the invention may be better understood and put into practical effect there will be described with reference to the accompanying drawings a preferred non-limitative practical e bod- iment of a drive system according to the present invention. In the drawings:- FIG. 1 is a side view of a vehicle including the drive system of the present invention; FIG. 2 is a top view of the drive system in the vehicle of FIG. 1 without wheel positioning means; and FIG. is a similar view to that of FIG. 2 but including one type of wheel positioning means. A three-wheeled vehicle 2 is shown which has driven wheels , 6 and a steerable wheel 8 which is controlled by handlebars 10. On the floor 12 of the vehicle is a speed pedal 1-4- to allow control of the speed of the vehicle. A brake control 16 is mounted on the handlebars 10 for actuating braking means (not shown). A drive system 18 includes an electric motor 20 as a primary power source and an associated fly¬ wheel 22 as a supplementary power source. The electric motor 20 is preferably a high speed motor of the permanent magnet type and is powered by a battery pack 24-. The flywheel 22 is usually of a concave conical shape but may be of any suitable shape dep¬ endent upon the desired drive characteristics- A friction wheel 26, the axle 28 of which couples via a universal joint 32, a constant velocity -_: * ._ joint or other similar means to a drive shaft 30, is adapted to engage with the face of the flywheel 22. The friction wheel 26 is " ovable in an arc with its contact area staying in a fixed geometric relation- ship with the curved flywheel 22 to maintain a close geometric approximation to a continuously variable bevel drive having minimum scrub at any driving contact point in its operating range. A spring 33 provides thrust to wheel 26 to enable it to transmit torque to shaft 30. Wheel 26 is maintained in its correct planar relationship with flywheel 22 by a sliding rotating bearing 4-3 acting on a fixed slide or other means. The drive shaft 30 is coupled by a chain and sprocket arrangement 3*^ to the drive axle 36 for wheels , 6 via differential 35- τ ^e chain and sprocket arrangement may be substituted by a pulley and belt system, a geared arrangement or any other suitable means. The transmission ratio of the drive system is dependent on the position of the driven wheel 26 relative to the flywheel 22 and this position is continuously varied to control vehicle speed and load on the drive system. The means of varying this posit¬ ion may be mechanical, by foot or hand levers (not shown) or monitored by an electronic control circuit (not shown) which may monitor and compute the drive ratio required for varying drive conditions. In FIG. 3 there is shown an arm 38 around shaft 28 which includes a geared sprocket segment 0 meshing with a gear of an electric reduction motor 42, actuation of which is controlled by the electronic control circuit to give in effect an automatic gear box. In a manually controlled version instruments showing drive motor speed and other drive-required f OMPI information may be provided to enable the driver to in effect compute his own driving ratio to ensure optimum operation with a minimum of cost. In use, with the vehicle stationary, friction wheel 26 is disengaged from the flywheel 22 and is located in position 5 (indicated in phantom in FIG. 3). To set the vehicle in motion the motor 20 driving the flywheel 22 is energised and the flywheel 22 allowed to reach its selected idle or starting speed (which will be quite high) and at which speed the flywheel will store enough energy to provide initial acceleration to the vehicle before dropping in speed by a significant amount. Therefore, the energy stored in the flywheel 22 is used for the initial accelerat- ion of the vehicle 2 rather than the energy stored in the battery 24. The driver then operates a mechanism e.g. speed pedal 14 to move the wheel 26 into engage¬ ment, with flywheel 22 (shown in phantom at 44 in FIG. 2) and so actuate the drive system. Vehicle acceler- ation and speed will depend on the transmission ratio selected - either manually or automatically, and the speed at which this ratio is changed. To increase the speed of the vehicle and vary the transmission ratio, the friction wheel is moved along the face of flywheel 22 dependent on the position of the speed pedal 14. As the friction wheel moves from the phantom position 44 the greater angular velocity of the flywheel in this region will accordingly increase the speed of the friction wheel. Various mechanical, electric or hydraulic interconnections from the speed pedal to the elect¬ ronic control circuit could be made to enable the driver to select the correct drive ratio for a partic¬ ular load and speed. The use of microprocessor tech- nology may be used for the control of the drive system OM -* or simple instruments provided for the operator to make adjustments to the transmission ratio as required. The friction wheel may be of any suitable type but is preferably a tyred wheel having a solid or pneumatic tyre. When the vehicle 2 is stationary and the motor 20 activated, the motor drives the flywheel 22 at high speed. 3y keeping the motor revolving at high speed the efficiency of the motor is above ?0 whereas at * low speeds the efficiency may be reduced to as low as 10% and the range of speeds used by the motor under normal use will be reduced. As the speed pedal 14 is further depressed, the friction wheel 26 moves along the flywheel 22 to regions of greater radius. This is, in effect, increasing the transmission ratio. After the first period of acceleration using the energy in the fly¬ wheel 22, the motor.20 drives the vehicle using the energy of battery 24. Once the friction wheel 22 assumes the "cruise" position shown in Figure 3 the vehicle 2 is cruising at relatively high speed using the battery 24 and motor 20. The energy in flywheel 22 "smooths" the peaks in the power consumption from the battery 24 while cruising. Thus at steady speed conditions a ratio will be selected that allows the motor to run at a speed within its optimum operating range. High torque to climb hills will be achieved by selecting a higher transmission ratio and lower output speed whilst down grades will use a lower trans- mission ratio and higher output speed. Deceleration will occur by moving the transmission to a higher ratio position which will then transform the kinetic energy of the moving vehicle to the flywheel by accel¬ erating it to a higher speed and so providing a supplementary energy storage system. Should there be sufficient kinetic energy available i.e. by descending OMP — o— a hill, the flywheel and motor will reach a situation where the motor will become a generator and so restore electrical energy to the ' battery system. This reverse cycle of recharging the energy storage system will apply every time the vehicle speed is reduced by a significant amount i.e. at every stop. It is to be understood that many modifications may be made in details of design or construction with¬ out departing from the ambit of the invention, the nature of which is to be ascertained from the appended claims. OMP

Claims: The claims defining the invention are as follows: 1. ■ A drive system for a vehicle, including a flywheel adapted to be motor driven and a transmission including a wheel adapted to be driven by the flywheel by frictional engagement of said wheel with a ace of said flywheel. 2. The drive system as claimed in Claim 1, wherein said flywheel has a concave conical shape. 3. The drive system as claimed in Glaim 1 or Claim 2, wherein said flywheel is driven by an electric motor. 4. The drive system as claimed in any preceding claim, wherein said wheel and said flywheel are adapted to be moved relative to one another to vary the trans¬ mission ratio. 5- The drive system as claimed in Claim 4, wherein said wheel includes an output shaft whose angular dis¬ position is variable to alter the transmission ratio by changing the position of contact of said wheel on said flywheel. 6. The drive system as claimed in Claim 4 or Claim 5 - wherein relative movement of said flywheel and wheel is dependent on the position of an operator operated pedal or lever. 7. The drive system as claimed in any preceding claim, wherein the position of said wheel on said fly¬ wheel is controlled by an electronic drive means. 8. The drive system as claimed in any preceding claim wherein said wheel is resiliently biassed to said flywheel. 9» A drive system for a vehicle substantially as hereinbefore described with reference to the accompany¬ ing drawings. - • RE OMP

Inventors: DEAN H
Applicants: DEAN H
Application year: 1981
Main classification: F16H15
IPC codes: B60K6, F16H15