GB2314820A

GB2314820A - An electric propulsion system for vehicles

Info

Publication number: GB2314820A
Application number: GB9614152A
Authority: GB
Inventors: Russell John Searle
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-07-05
Filing date: 1996-07-05
Publication date: 1998-01-14
Also published as: GB9614152D0

Abstract

An electric auxiliary drive for a bicycle comprises a friction roller (G) driven by an electric motor (E) and in engagement with a bicycle tyre (H). The motor and roller are pivoted about a point (J) which intersects the diameter of the bicycle wheel such that the reaction to the rotation of the roller urges the roller against the tyre. The motor is activated above a predetermined level of pedal effort by using the effect of pedal thrust reaction on the rider's body. This is determined by handgrips which incorporate compressed air chambers, the air pressure operating switches to energise the motor.

Description

AN ELECTRIC PROPULSION SYSTEM FOR VEHICLES Successful auxiliary electric propulsion for pedal cycles for example, depends upon very low wastage and maximum utilisation of the energy available.

A major cause of wastage is the use of auxiliary power either when it does not provide maximum benefit to the rider or when it is not efficient in its use of the energy available.

The present invention reduces these inefficiencies by limiting the application of power to coincide with a predetermined minimum level of effort exerted on the pedals, thus reducing the effort required during each revolution of the pedal crank but power still remaining available by manual control.

Also mechanical losses in the servo action tyre drive system, which is chosen for its simplicity and adaptability, are reduced to a very low level, being proportionate to the power transmitted. Also slip and tyre wear are effectively eliminated.

The result of these improvements is that a lightweight system is now capable of giving power assistance when required for an average journey up to 25 KM, greater than the performance of existing systems.

An important feature of the servo action of the tyre drive system is that its geometry provides a "depth of engagement V torque transmitted" characteristic which is not critical of tyre pressure.

A practical embodiment of the system is shown in Fig. 1. The motor (E), which is attached to the vehicle by means of a rotatable bearing at U), carries the roller (G) which is held in contact with the tyre (H) by spring means.

Alternatively the roller may be permanently in contact with the tyre, taking up a position in which its point of contact is in line with its axis and the axis of the wheel, there being an abutment to resist movement of the roller about its mounting axis in the direction of rotation of the wheel. The axis of the motor (E), is parallel to the axis of the wheel and to the axis of the bearing (J) which axis also intersects the wheel and is in line with or forward of a line joining the motor and wheel axes, such that the arc of movement of the motor and roller intersects the tyre.

A method of activating the auxiliary electric propulsion above a pre-determined level of pedal effort is achieved by using the effect of pedal thrust reaction on the riders body at its interface with the bicycle, for example by the arms pulling on the steering hand grips, as shown in Fig. 2 or the body being supported by a back rest.

In a practical solution described by reference to Fig. 2a; a compressible air chamber which may be in the form of an elastic tube (A) is incorporated in each hand grip (B) being exposed to the effect of finger pressure on a forwardly disposed surface, so that in resisting pedal thrust reaction the air is compressed which operates remote switching means via a capillary tube to activate the motor.

In the arrangement shown, to prevent inadvertent operation of the system by the air chamber being compressed other than by reaction to pedal thrust, the steering member B and the air chamber A are surrounded by a loosely attached member such as the rigid tube C, which forms the hand grip, operation of the system only being possible by moving the hand grip C in the direction indicated, by pulling on the handle bars.

The air chambers of each hand grip may be connected to a common circuit so that pressure on both is necessary to operate the switching means. Alternatively, two switches connected in series may be used.

Alternatively, a pressure sensitive electrical switch is operated from each handgrip, the switches being connected in series with the motor circuit so that both have to be closed for the motor to operate.

A uni-directional clutch i.e. freewheel mechanism, may be interposed between the motor (E) and the roller (G).

Claims

The present invention refers to electric power driven vehicles or electric power assisted vehicles such as bicycles.

In a primary feature of the invention which concerns vehicles in which drive is by means of a roller engaging with the tyre of a wheel, the bearing of the roller is compliantly mounted to the frame of the vehicle about an axis, spaced from that of the roller, which passes through the diameter of the wheel or tyre, such that the roller is displaceable in an arc which intersects the periphery of the wheel.

In a second feature of the invention according to the preceding feature, wherein the roller is displaced about its mounting axis, in response to driving torque reaction, in a direction opposite to the direction of rotation of the wheel.

In a third feature of the invention according to the preceding features wherein means are provided to resist movement of the roller about its mounting axis in a direction similar to the direction of rotation of the wheel when driven.

In a further primary feature of the invention which concems pedal powered vehicles with power assistance, means are provided to sense the pedal thrust reaction on the rider which thereby activates the electric traction motor.

In a fourth feature of the invention according to the preceding feature wherein pedal thrust reaction is transmitted to the frame of the vehicle from the rider via the steering hand grips which incorporate pressure sensing means to activate the electric traction motor.

In a fifth feature according to the preceding feature wherein a pneumatic actuator is attached to a forwardly disposed surface of the steering hand grips being connected pneumatically with electrical switching means to operate the traction motor.

In a sixth feature according to the fourth and fifth features wherein an intermediate member surrounds the pressure sensing means and the steering member such that in resisting pedal thrust reaction the intermediate member is moved relative to the steering member to operate the sensing means.