Field of the Invention

The present invention relates to a drive and regenerative braking system for providing power to propel a vehicle and which can slow a vehicle from an increased velocity while regenerating some of the energy normally lost while doing so.

Background of the Invention

A major challenge facing the automotive industry is to provide efficient and economic solutions to assist in the reduction of atmospheric pollution and increase in fuel efficiency and avoid costs associated with over-sized prime movers such as internal combustion engines (ICE). A further challenge is to use pollution free alternative fuels such as hydrogen in fuel cells to reduce pollution.

When a vehicle is braked from an increased velocity to a reduced velocity, energy is lost through heat and sound. Rather than relying fully on brakes to slow a vehicle, it is known to utilise a vehicle's engine and gear box to achieve the braking, however that still results in lost energy.

It is known in electrical or hybrid (a combination of electrical and internal combustion) powered vehicles to provide systems which not only brake the vehicle, but which also recapture some of the kinetic energy that would normally be lost when braking. A system which can provide power to propel a vehicle and which can slow a vehicle from an increased velocity while regenerating some of the energy normally lost while braking, will be termed herein a "drive and regenerative braking system". Regeneration systems in electrical or hybrid powered vehicles generally function by electrically switching a motor to act as a generator that converts motion into electricity rather than converting electricity into motion. That energy would then be stored in the battery for example. The stored energy may be converted back to mechanical energy by an electric motor. It is generally accepted that the use of storage batteries as the sole means of power supply is not a practical solution, except for small applications. With increasing crude oil costs, fuel is becoming significantly more expensive. Further, atmospheric pollution and green house gas effects need to be reduced. It would be desirable to provide a regenerative braking system which uses a mechanical energy storage device (such as a flywheel) which is suitable for use with an internal combustion engine, to regenerate some of the energy normally lost while braking and thereby assist in minimising fuel costs.

Systems which are capable of regenerating some of the energy normally lost while braking are described in US 4,519,485; US 4,679,646; US 3,665,788; US 4,588,040; US 5,067,932; US 5,575,730; US 6,120,411; US 4,411,171; US 4,393,964; US 4,276,951; US 3,749,194; US 4,495,836; and US 4,171,029. Generally these systems require complex control systems to minimise slippage or shock loadings associated with engaging a storage flywheel with inertia of the vehicle.

It is therefore an object of at least preferred embodiments of the present invention to provide a drive and regenerative braking system which can operate with a relatively simple control system and/or which at least provides the public with a useful alternative.

Summary of the Invention

The term 'comprising' as used in this specification and claims means 'consisting at least in part of, that is to say when interpreting statements in this specification and claims which include that term, the features prefaced by that term in each statement all need to be present but other features can also be present.

In accordance with a first aspect of the present invention, there is provided a drive and regenerative braking system for a vehicle, the system comprising: a drive train including a drive shaft which is selectively operatively connected to an output of a source of motive power, the drive shaft arranged to provide motion to an input of a first variable transmission unit having an output which is operable, in response to motion of the drive shaft, to drive at least one wheel of the vehicle to move the vehicle, and including a mechanism to selectively decouple the first transmission unit; and a regeneration arrangement including a second variable transmission unit and a flywheel arranged to store energy received from the second transmission unit and to selectively deliver that stored energy to the drive shaft, and including a mechanism to selectively decouple the second transmission unit; the system configured such that when it is desired to slow the vehicle, the first transmission unit is decoupled and the second transmission unit is coupled and energy is transferred from the wheel(s) via the second transmission unit to the flywheel for storage, thereby slowing the wheel(s) and storing energy.

The first transmission unit is "decoupled" when rotational movement of the drive shaft cannot drive the wheel(s), and is "coupled" when rotational movement of the drive shaft is able to drive the wheel(s). The second transmission unit is "decoupled" when energy cannot be transferred via the second transmission unit from the wheel(s) to the flywheel, and is "coupled" when energy is able to be transferred via the second transmission unit from the wheel(s) to the flywheel. Normally, when the first transmission is coupled the second transmission is decoupled and vice versa.

The system is preferably configured such that when it is desired to propel the vehicle, the first transmission unit is coupled and the second transmission unit is decoupled and energy is transmitted to the wheel(s) via the first transmission unit from the flywheel and/or the connected source of motive power.

Preferably, the system comprises a first one-way clutch arranged to couple the output of the source of motive power to the drive shaft and which allows the drive shaft to overrun the output of the source of motive power if the speed of the drive shaft is greater than the speed of the output of the source of motive power. Preferably, the system comprises a second one-way clutch arranged to couple an output of the flywheel to the drive shaft and which allows the drive shaft to overrun the output of the flywheel if the speed of the drive shaft is greater than the speed of the output of the flywheel.

It will be appreciated that the first and second one way clutches are both configured to drive the drive shaft in one direction.

The arrangement of the first and second one-way clutches which connect the source of motive power and flywheel to the drive shaft is preferably such that when the rotational speed of output of the source of motive power is tending to exceed the rotational speed of the drive shaft, torque is transmitted to the drive shaft over the first one-way clutch; when the rotational speed of the output of the flywheel is tending to exceed the rotational speed of the drive shaft, torque is transmitted to the drive shaft over the second-one way clutch; and when the rotational speed of the drive shaft is greater than the rotational speed of the output of the source of motive power or the rotational speed of the output of the flywheel, the respective clutch freewheels.

As used herein, a one-way clutch as a device which allows substantially free relative movement (free-wheeling) of a given component in relation to the other component when the relative speed between the components is, say, positive but does not allow relative movement when the relative speed is zero and tending to become negative. In other words the one-way clutch is a device which locks or engages the two components when there is tendency for the relative speed to become negative from zero. Another term for a one-way clutch is "overrunning clutch". The clutches may be mechanical one-way clutches, but the term also covers other alternatives such as brakes which are controlled to allow rotational movement in one direction but not the other and fluid based systems for example.

The output of the flywheel would generally be a shaft either fitted to, or operatively connected to, the flywheel. If a gear arrangement is provided between the flywheel and the second one-way clutch, then the speed of the output of the gear arrangement would determine whether or not the flywheel would be coupled to the drive shaft. Such an alternative is intended to be captured by the wording "output of the flywheel".

At least one of the transmission units may be an infinitely variable transmission unit.

In the most preferred embodiment, one or both of the transmission units are gyroscopic variable transmission units, such as described in US Patent No. 6,640,659, the disclosure of which is incorporated herein by reference. As used herein, a "gyroscopic variable transmission unit" is a transmission unit that has at least: a fixed housing or support; an input member which is either rotatable about an axis of rotation relative to said fixed housing or support or reciprocable along an axis relative to said fixed housing or support; a torque shaft; and an output member arranged to be rotated about an axis of rotation by the torque shaft; a first one-way clutch between the torque shaft and output member; a linkage arrangement rotatable about the axis of the input member under the influence of said input member; and a gyroscopic rotor mounted on the linkage arrangement and having a spin axis which is cyclically angularly deflected in response to the input member to generate gyroscopic reaction forces, the reaction forces generated by the rotor as its axis is cyclically deflected being applied to the torque shaft as positive and negative torque; the first-one way clutch being configured to apply the positive torque to the output member; and the torque shaft being connected over a second one-way clutch of opposite sense to the first one-way clutch either to said housing or support to apply the negative torque to the housing or support, or alternatively to the output member over a rotation reversal system to apply the negative torque to the output member as positive torque. The torque shaft may be part of the linkage arrangement or may be separate to the linkage arrangement.

Whilst either a gyroscopic variable transmission unit having a rotatable input member or a gyroscopic variable transmission unit having a reciprocable input member could be used as either or both transmission unit(s), it is preferred that the gyroscopic variable transmission unit(s) has/have a reciprocable input member. Clearly, it will be necessary to convert the rotating movement of the drive shaft and the shaft in the regeneration arrangement to reciprocating movement of the respective transmission input members. That could be achieved using any known method such as a wobble plate, a crank and connecting rod arrangement, or a cam arrangement for example.

At least one of the mechanisms to selectively decouple the first and second transmission units may be external to the respective transmission unit. For example, the mechanism to selectively decouple the first transmission unit may comprise a physical clutch between the first transmission unit and the wheel(s). The mechanism to selectively decouple the second transmission unit may comprise a physical clutch between the second transmission unit and the flywheel.

At least one of the mechanisms to selectively decouple the first and second transmission units may be internal to the respective transmission unit. In the embodiment having at least one gyroscopic variable transmission unit, the mechanism to selectively decouple the transmission unit may be configured to restrain movement of the torque shaft of the respective gyroscopic variable transmission unit.

For example, the mechanism to selectively decouple may comprise a disc mounted for rotation with the respective torque shaft, and a caliper configured to selectively frictionally restrain movement of the disc thereby restraining movement of the torque shaft.

Alternatively, the mechanism to selectively decouple may comprise a gear mounted for rotation with the respective torque shaft, the gear operatively meshed with a further gear which includes an offset linkage operatively connected to a hydraulic piston, the mechanism to selectively decouple configured such that preventing movement of the hydraulic piston prevents movement of the gears, thereby preventing movement of the torque shaft.

In another alternative, an outer housing of the second one-way clutch of the respective transmission unit may be selectively rotatable relative to the fixed housing or support of the transmission unit, with the respective transmission unit decoupled when the outer housing is allowed to rotate relative to the fixed housing or support.

One or more speed-reducing or speed-multiplying arrangements could be provided between the drive shaft and the first transmission unit, between the first transmission unit and the wheel(s), and/or between the wheel(s) and the second transmission unit to facilitate the design of the first and second transmission units. A speed-multiplying arrangement may be provided between the second transmission unit and the flywheel and/or a speed- reducing arrangement between the flywheel and the second one-way clutch to facilitate greater storage of energy in the flywheel. In that embodiment, the second one-way clutch will couple the output of the speed-reducing arrangement to the drive shaft if the speed of the output of the speed-reducing arrangement is substantially the same as the speed of the drive shaft, and will allow the drive shaft to overrun the output of the speed-reducing arrangement if the speed of the drive shaft is greater than the speed of the output of the speed-reducing arrangement. If desired additional power inputs may be incorporated into the system. For example a fuel cell-driven motor may be provided and arranged to charge the flywheel when the first transmission unit is decoupled. The fuel cell motor may be connected on either side of the second transmission unit. Alternatively or in addition, a further power input such as a fuel cell motor may be applied to the drive shaft over a third one-way clutch when the first transmission is coupled. The third one-way clutch will be similar to the first and second one-way clutches in that the drive shaft overruns the output of the additional power input if the speed of the drive shaft is greater than the speed of the output of the additional power input.

The drive shaft is preferably operatively connected to a crank shaft of an internal combustion engine via the first one-way clutch. The internal combustion engine may have an in-line, "V", or opposed piston configuration, or could be another type such as a rotary engine for example.

In accordance with a second aspect of the present invention, there is provided a drive and regenerative braking system for a vehicle, the system comprising: a drive train including a drive shaft which is operatively connected to an output of a source of motive power through a first one-way clutch arranged to couple the output of the source of motive power to the drive shaft and which allows the drive shaft to overrun the output of the source of motive power if the speed of the drive shaft is greater than the speed of the output of the source of motive power, the drive shaft arranged to provide motion to an input of a first infinitely variable transmission unit or gyroscopic variable transmission unit (as herein defined) having an output which is operable, in response to motion of the drive shaft, to drive at least one wheel of the vehicle to move the vehicle, and including a mechanism to selectively decouple the first transmission unit; and a regeneration arrangement including a second infinitely variable transmission unit or gyroscopic variable transmission unit (as herein defined) and a flywheel arranged to store energy received from the second transmission unit and to deliver that stored energy to the drive shaft through a second one¬ way clutch arranged to couple the flywheel to the drive shaft and which allows the drive shaft to overrun the output of the flywheel if the speed of the drive shaft is greater than the speed of the output of the flywheel, and including a mechanism to selectively decouple the second transmission unit; the system configured such that when it is desired to slow the vehicle, the first transmission unit is decoupled and the second transmission unit is coupled and energy is transferred from the wheel(s) via the second transmission unit to the flywheel for storage, thereby slowing the wheel(s) and storing energy, and when it is desired to propel the vehicle the first transmission unit is coupled and the second transmission unit is decoupled, and energy is transmitted to the wheel(s) via the first transmission unit from the flywheel and/or the connected source of motive power.

In accordance with a third aspect of the present invention, there is provided a drive and regenerative braking system for a vehicle, the system comprising: a drive train including a drive shaft which is operatively connected to an output of a source of motive power through a first one-way clutch arranged to couple the output of the source of motive power to the drive shaft and which allows the drive shaft to overrun the output of the source of motive power if the speed of the drive shaft is greater than the speed of the output of the source of motive power, the drive shaft arranged to provide motion to an input of a first gyroscopic variable transmission unit (as herein defined) having an output which is operable, in response to motion of the drive shaft, to drive at least one wheel of the vehicle to move the vehicle, and including a mechanism to selectively decouple the first transmission unit; and a regeneration arrangement including a second gyroscopic variable transmission unit (as herein defined) and a flywheel arranged to store energy received from the second transmission unit and to deliver that stored energy to the drive shaft through a second one-way clutch arranged to couple the flywheel to the drive shaft and which allows the drive shaft to overrun the output of the flywheel if the speed of the drive shaft is greater than the speed of the output of the flywheel, and including a mechanism to selectively decouple the second transmission unit; the system configured such that when it is desired to slow the vehicle, the first transmission unit is decoupled and the second transmission unit is coupled and energy is transferred from the wheel(s) via the second transmission unit to the flywheel for storage, thereby slowing the wheel(s) and storing energy, and when it is desired to propel the vehicle the first transmission unit is coupled and the second transmission unit is decoupled, and energy is transmitted to the wheel(s) via the first transmission unit from the flywheel and/or the connected source of motive power. The systems of the second and third aspects may include any of the features outlined in respect of the first aspect above.

The invention consists in the foregoing and also envisages constructions of which the following gives examples only.

Brief Description of the Drawings

Preferred embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings in which:

Figure 1 is a schematic view of a drive and regenerative braking system of a preferred embodiment of the present invention;

Figure 2a schematically shows a differential-type gyroscopic variable transmission unit which may be used in the system of Figure 1 ;

Figure 2b schematically shows a reciprocating-type gyroscopic variable transmission unit which may be used in the system of Figure 1;

Figure 2c schematically shows an alternative reciprocating-type gyroscopic variable transmission unit which may be used in the system of Figure 1;

Figure 2d schematically shows a crank and connecting rod arrangement for transferring motion from a rotating shaft to the reciprocable input of the gyroscopic variable transmission unit of Figure 2b or 2c;

Figure 3 shows details of a preferred arrangement for selectively decoupling the gyroscopic variable transmission of Figure 2a, 2b, or 2c;

Figure 4 is a sectional view of part of an alternative preferred arrangement for selectively decoupling the gyroscopic variable transmission of Figure 2a, 2b, or 2c;

Figure 5a and 5b show details of preferred arrangements for adjusting the effective inertia of the torque shaft of the gyroscopic variable transmission of Figure 2a, 2b, or 2c, to selectively decouple the transmission; Figure 6 is a schematic view a regenerative braking system of an alternative preferred embodiment of the present invention; and

Figure 7 is a schematic view of an infinitely variable transmission unit which can be used in the system of Figure 6.

Detailed Description of Preferred Forms

Figure 1 schematically shows a preferred drive and regenerative braking system indicated generally by reference numeral 1 which includes a drive train 3 and a regeneration arrangement 5. The drive train 3 includes a drive shaft 7 which is operatively connected to an output of a source of motive power, which in the preferred embodiment is the crankshaft 9 of an internal combustion engine 11. The drive shaft 7 is arranged to provide motion from the crankshaft 9 to a first transmission unit 13 having an output 15 which is operable, in response to motion of the drive shaft 7, to drive at least one road wheel 17 of the vehicle to move the vehicle. Generally, two road wheels would be arranged to be driven by the output 15 via a differential mechanism (not shown).

The drive train includes a mechanism to decouple the first transmission unit 13. In the embodiment shown, the mechanism 19 is external to the transmission unit 13. However, as will be described below, the mechanism to selectively decouple the first transmission unit 13 may be part of the transmission unit. When the transmission unit 13 is coupled, torque can be transmitted from the drive shaft 7 to the wheels 17. The first transmission unit is decoupled when rotational movement of the drive shaft cannot drive the road wheel(s), and is coupled when rotational movement of the drive shaft is able to drive the road wheel(s).

The regeneration arrangement 5 includes a second transmission unit 21 arranged to receive energy from the wheels 17 and a flywheel 23 arranged to store energy received from the output of the second transmission unit and to selectively deliver that stored energy to the drive shaft. The regeneration arrangement 5 includes a mechanism to selectively decouple the second transmission unit 21. In the embodiment shown, the mechanism 25 is external to the transmission unit. Again, the mechanism to selectively decouple the second transmission unit 21 may be part of the transmission unit. The second transmission unit is generally decoupled except when transferring energy from the road wheels to the flywheel.

The first and second transmission units are either infinitely variable transmission (IVT) units or gyroscopic variable transmission (GVT) units, or a combination thereof.

In the most preferred embodiment, either or both of the transmission units 13, 21 are gyroscopic variable transmission (GVT) units. Such transmission units are described in US Patent No. 6,640,659. As mentioned previously, a transmission is considered a GVT if it has at least: a fixed housing or support; an input member which is either rotatable about an axis of rotation relative to said fixed housing or support or reciprocable along an axis relative to said fixed housing or support; a torque shaft; and an output member arranged to be rotated about an axis of rotation by the torque shaft; a first one-way clutch between the torque shaft and output member; a linkage arrangement rotatable about the axis of the input member under the influence of said input member; and a gyroscopic rotor mounted on the linkage arrangement and having a spin axis which is cyclically angularly deflected in response to the input member to generate gyroscopic reaction forces, the reaction forces generated by the rotor as its axis is cyclically deflected being applied to the torque shaft as positive and negative torque; the first-one way clutch being configured to apply the positive torque to the output member; and the torque shaft being connected over a second one-way clutch of opposite sense to the first one-way clutch either to said housing or support to apply the negative torque to the housing or support, or alternatively to the output member over a rotation reversal system to apply the negative torque to the output member as positive torque. The torque shaft may be part of the linkage arrangement or may be separate to the linkage arrangement. It will be appreciated that the arrangement of the first and second one-way clutches of the GVT is such that in normal operation, the output member of the GVT is driven by the torque shaft in one sense of rotation only.

A suitable differential-type GVT unit is shown in Figure 2a. That GVT unit includes an input member 101 which is rotatable relative to a fixed housing or support 103. A gimbal arrangement has a main outer frame 105 is fixed for rotation with the input member 101. A shaft 107 is rotatably mounted on the main frame 105, and a torque shaft 109 is coupled to the shaft 107 differentially through a gear train having gears 111, 113, 115, and 117. A shaft 119 is rotatably mounted on the main frame 105 and the gears 113, 115 are attached to the shaft. Shaft 107 is coaxial with shaft 121 which is also rotatably mounted on the main frame, and an inner sub-frame 123 of the gimbal is attached to the shafts 107, 121.

A gyroscopic rotor 125 is rotatably mounted on the sub-frame 123, preferably via a shaft 127. Rotation of the rotor 125 may be driven by a motor 129 (for example, an electric motor), or could be driven as a result of input/output motions via a gear system for example. The torque shaft 109 is connected via a first one-way clutch 131 to an output member 133 and via a second opposite one-way clutch 135 to the fixed housing or support. As will be described below, in some embodiments it may be desirable to selectively allow the second one-way clutch 135 to rotate relative to the fixed housing or support, to decouple the transmission.

During operation of the transmission, the input motion of the input member 101 causes precession of the spin axis and thereby the spin vector of the rotor 125. As the spin vector is precessed continuously, a cyclical gyroscopic reaction is generated from the spin vector. The cyclical reaction is rectified by the one-way clutches 131, 135 so that the rectified (positive) component is applied to the output member 133 of the transmission. In the embodiment shown, the other (negative) component is transmitted to the fixed housing or support via one-way clutch 135. In an alternative embodiment, a reversing gear train could be used to deliver that component to the output member, thereby providing full rectification.

The above-mentioned cyclical reaction is affected by the output rotation as well. When the output rotation is zero the cyclical reaction has no component acting on the input and hence no power is drawn from the input. However when the output rotation is present a corresponding reaction component on the input occurs to match the energy output. Thus, such a GVT is inherently able to match the input and the output energy without any external controls, and by utilising good bearing technology and practices advantageously features high efficiency / low loss at all times. Feedback control is only required to achieve desired operating point and it is achieved by stroke control of the input (if a reciprocating input GVT is used), rotor speed control and/or control of the inertia of the torque shaft.

When the torque shaft 109 of the transmission receives the positive torque, the torque shaft is accelerated to synchronise with the transmission output member 133 at which point the first one-way clutch 131 transmits torque to the output member, transmitting power. During the negative torque part of the cycle, the torque shaft 109 is decelerated until its rotational speed is zero at which point it is synchronised with the fixed housing or support 103 and the second one-way clutch 135 transmits the negative torque to the housing.

The theory behind the gyroscopic reactions in the operation of the transmission is described in more detail in US Patent No. 6,640,659. It would also be possible to utilise a reciprocating input GVT as either or both of the transmissions, if an arrangement was provided to convert rotational movement of the drive shaft to reciprocating movement of the input member.

Figure 2b shows a reciprocating-type GVT unit which can be used in the system of Figure 1. The transmission has an input member 101' which is reciprocable along an axis relative to a fixed housing or support 103'. An output member 133' is rotatable relative to the fixed housing or support 103'. An outer frame 105' is rotatably supported in the housing 103' by means of co-axial shafts 106'. An inner frame 123' is rotatably supported on the outer frame 105' by means of co-axial shafts 107'. A mis-alignment joint 108' such as a constant velocity joint is coupled to the output member 133' so that the pivot point of the misalignment joint is preferably coincident with the intersection point of the pivot axes of the inner and outer frames. A flexible joint 110' capable of relatively small degrees of linear and angular misalignment may be provided between the output member 133' and the misalignment joint 108' to accept any deviation between the intersection points. A torque shaft 109' is rotatably supported on a shaft support 104'.

The shaft 109' is connected to an input link 112' through a pin joint. In its simplest form, the link 112' is a rod with provisions for pin joints at its ends. Attached to the input member 101' are grooved flanges 114', 116' which accept rolling elements 118' and a flange 120' is rotatably mounted in between the flanges between the rolling elements. The flange 120' is provided with an extension such as a fork 122' to accept a pin joint 124' with the input link as shown.

A first one-way clutch 131' operatively connects the members 109', 133' while a second, opposite one-way clutch 135' connects the torque shaft 109' to the shaft support 104'. A rotor shaft support 126' is attached to the torque shaft 109' and a rotor 125' is rotatably mounted on rotor shaft support 126' by means of a rotor shaft 127'. 129' is a motor mounted on the rotor shaft support 126' and configured to drive the rotor 125' via the rotor shaft 127'.

The operation of this type of gyroscopic transmission is described in US 6,640,659, however to summarise, reciprocating motion of the input member 101 ' causes precession of the spin axis of the gyroscopic rotor 125'. Positive torque is delivered from the torque shaft 109' to the output member 133' via one-way clutch 131', and negative torque is delivered to the shaft support 104' via one-way clutch 135'.

Figure 2c shows another reciprocating-type GVT unit that can be used in the system of Figure 1. The transmission has an input member 101" which is reciprocable along an axis relative to a fixed housing or support 103".

An output member 133" is rotatable relative to the fixed housing or support 103", and is connected to a gear 133a" which engages a gear 131a" on a first one-way clutch 131", which is mounted between the gear 131a" and the torque shaft 109". The torque shaft 109" is rotatable relative to the fixed housing or support 103". An opposed one-way clutch 135" is mounted between the torque shaft 112" and the fixed housing or support 103". A fork 143" is attached to the torque shaft 109". A rotor shaft 127" of the gyroscopic rotor 125" is rotatably mounted on a frame member 147". The frame member 147" is rotatably mounted on the fork 143" by means of co-axial shafts 148" which extend from the frame member 147".

A thrust bearing arrangement 118" connects the input member 101" to an outer frame member 140" which forms a rack of a rack and pinion arrangement. Pinions 142" are attached to the shafts 148", such that reciprocating motion of the input member 101" is translated into oscillation of the rotor shaft 127" about the axis of the shafts 148" thereby creating an output torque and reaction torque on the torque shaft 109".

In the configuration of Figure 2c, the input motion also spins the rotor. A bevel gear 144" is rotatably mounted to one of the forks 143" concentrically with the shafts 148". A compound gear 145" is rotatably mounted on the frame member 147". The bevel gear ring of bevel gear 145" engages the gear 144", while the spur gear ring of bevel gear 145" engages gear 146" which is coupled to the rotor shaft 127" through a one-way clutch (not shown).

The operation of this type of gyroscopic transmission is described in US 6,640,659, however to summarise reciprocating motion of the input member 101" results in reciprocating motion of the rack 140", which in turn causes oscillation of the rotor shaft 127" about the axis of the shafts 148" due to movement of the pinions 148", and also rotation of the rotor 125" relative to the frame member 147" via the gears 144", 145", and 146". That results in the formation of gyroscopic forces which rotate the fork 143" about the axis of the torque shaft 109", and the delivery of an output torque and reaction torque on the torque shaft 109". In the same manner as described above, positive or output torque from the torque shaft is applied to the output member 133" via the first one-way clutch 131" and gears 131a" and 133a", while negative or reaction torque from the torque shaft is applied to the fixed housing or support 103" by the second one-way clutch 135".

It will be apparent that it will be necessary to create a reciprocating motion of the input member 101 ', 101" from rotation of another shaft. That can be achieved using a crank and connecting rod, a wobble plate, or a cam or similar arrangement. It is preferred that reciprocating type GVT units are used, as they have higher possible speed ratios.

Figure 2d schematically shows a suitable crank and connecting rod arrangement 8 for creating a reciprocating motion of the input member 101', 101" from rotation of another shaft, such as the drive shaft 7. A crank 8a is cantilevered from the drive shaft 7, is configured to rotate with rotation of the drive shaft. A connecting rod 8b is pivoted to the crank 8a at pivot 8c. A slider 8d is pivoted to the connecting rod at pivot 8e. The slider is arranged to move within a part of the fixed housing or support 103' which acts as a guide for the slider, and is operatively connected to the input member 101', 101" of the GVT unit. As the drive shaft 7 rotates, the crank and connecting rod arrangement 8 causes the input member 101', 101" to reciprocate in the guide. It will be appreciated that if a reciprocating-type GVT unit is used as the second transmission unit in the system, a similar crank and connecting rod arrangement 8 could be provided for that transmission unit.

Other types of GVT units could also be used.

If a gyroscopic variable transmission unit such as shown in Figure 2a is used as the first transmission unit 13 in the present system, the input member 101 of the transmission unit could be the drive shaft 7 or operatively connected to the drive shaft 7, and the output member 133 of the transmission unit could be the output shaft 15 or operatively connected to the output shaft 15. Similarly, if a gyroscopic variable transmission unit such as shown in Figure 2a is used as the second transmission unit in the present system, the input member 101 of the transmission unit would be operatively connected to be driven by the road wheels, and the output member 133 would be operatively connected to deliver torque to the flywheel 23. If a gyroscopic variable transmission unit such as shown in Figure 2b or 2c is used as the first transmission unit 13 in the present system, the input member 101', 101" of the transmission unit would be operatively connected to the drive shaft 7 (via a wobble plate or the like), and the output member 133', 133" of the transmission unit could be the output shaft 15 or operatively connected to the output shaft 15. Similarly, if a gyroscopic variable transmission unit such as shown in Figure 2b or 2c is used as the second transmission unit in the present system, the input member 101', 101" of the transmission unit would be operatively connected to be driven by the road wheels (via a wobble plate or the like), and the output member 133', 133" would be operatively connected to deliver torque to the flywheel.

The second GVT unit can be smaller than the first GVT unit, as it is only used to transfer energy to the flywheel when the vehicle is being braked. It should be noted that in Figure 1, speed adjusting arrangements 27, 29 (such as gear arrangements) are provided in the drive train between the drive shaft 7 and the first transmission unit 13 and between the first transmission unit 13 and the wheels. Such arrangements could be provided to reduce the rotational speed transmitted from the drive shaft 7 to the first transmission unit 13 and from the first transmission unit 13 to the wheels for example. Alternatively, they could be speed multiplying arrangements, or a combination. However, it will be appreciated that such speed adjusting arrangements are not essential for the functioning of the invention. Further, one or more speed adjusting arrangements (not shown) could be provided as part of the regeneration arrangement, for example before or after the second transmission unit 21. It is preferred that one or more speed-reducing or speed-multiplying arrangements are provided between the drive shaft and the first transmission unit, between the first transmission unit and the road wheel(s), and/or between the road wheels and the second transmission unit to facilitate the design of the first and second transmission units. A speed-multiplying arrangement 30 may be provided between the second transmission unit and the flywheel and a speed-reducing arrangement 32 between the flywheel and the second one-way clutch to facilitate greater storage of energy in the flywheel.

The crank shaft 9 of the internal combustion engine 11 is operatively connected to the drive shaft 7 over a first one-way clutch 31, and the flywheel 23 is operatively connected to the drive shaft over a second one-way clutch 33.

General operation of the regenerative braking system is as follows:

When the vehicle is being propelled or accelerated by the internal combustion engine 11 , the second transmission unit 21 will be decoupled and the first transmission unit 13 will be coupled. When the crank shaft 9 is spinning with a rotational speed not less than the drive shaft 7, torque is transmitted from the crank shaft 9 to the drive shaft 7, and to the input of the first transmission unit 13 via a speed adjusting arrangement 27 (if present). Due to the configuration of the one-way clutch 33, that clutch will free wheel so that no torque is transmitted from the engine output 9 to the flywheel 23. The torque is transmitted from the output of the first transmission unit to the road wheels 17 via a speed adjusting arrangement 29 (if present) to accelerate or propel the vehicle.

When it is desired to slow the vehicle, the motive power from the source 11 is cut off such that the crank shaft 9 is in idling mode and the first transmission unit 13 is decoupled and the second transmission unit 21 is coupled. Torque is transferred from the road wheels 17 to the input of the second transmission unit 21 and from the output of the second transmission unit 21 to the flywheel which accelerates, thereby storing energy and slowing the road wheel speed. The flywheel can be caused to continue accelerating as the road wheels slow down by increasing the rotational speed of the gyroscopic rotor of the second transmission unit 21 if desired. When it is desired to again propel the vehicle, the second transmission unit 21 is decoupled and the first transmission unit 13 is coupled. Until the flywheel speed drops below the drive shaft speed, torque is transferred from the flywheel 23 via the one-way clutch 33 to the drive shaft 7, thereby regenerating some of the energy that would normally be lost during braking until the engine speed exceeds the flywheel speed. As the engine speed is increased to match the drive shaft speed, torque is transferred from the crankshaft to the drive shaft 7 via the one-way clutch 31. It will be understood that at least during initial acceleration, the energy being transferred to the first transmission unit 13 will be provided first by the flywheel 23 and then the motor 11.

If at any time the drive shaft 7 is rotating faster than the motor 11 and the flywheel 23, both one-way clutches 31, 33 will freewheel. This event is unlikely unless the drive shaft 7 is driven by another input source in which case the power is supplied by that source alone.

If desired, other power inputs may be incorporated into the drive train. For example a power unit such as a first fuel cell driven motor FC1 is connected to the drive shaft 7 over a third one-way clutch 34. The third one-way clutch will be similar to the first 31 and second 33 one-way clutches in that the drive shaft 7 overruns the output of the fuel cell driven motor if its speed is greater than the speed of the output of the fuel cell driven motor. A second fuel cell driven motor FC2 is operatively connected to an input of the second transmission unit 21 over a one-way clutch 36 and is arranged to charge the flywheel when the first transmission unit is decoupled. The clutch 36 is configured such that the shaft 38 overruns the output of the second fuel cell driven motor if its speed is greater than the speed of the output of the second fuel cell driven motor. The second fuel cell driven motor may be connected on either side of the second transmission unit.

The embodiment shown has the mechanism 19, 25 to selectively decouple the transmissions external to the transmissions. The mechanisms may be physical clutches for example, such that the respective transmission is coupled when the clutch is engaged and decoupled when the clutch is released. However, other decoupling mechanisms described herein are preferred, as when the clutches 19, 25 are engaged they may cause slippage and shock loadings.

It is possible to provide the mechanisms to selectively decouple the transmissions internal to the transmissions. One example configuration is shown schematically in Figure 3.

In that configuration, a gear 151 is mounted on the torque shaft 109 of the transmission, and meshes with a further gear 153. A linkage 155 is pivotally connected to the gear 153 via an eccentrically positioned pin 157, and is pivotally mounted at its other end to a shaft 159 of a piston 161 which is reciprocally movable in a hydraulic cylinder 163 as indicated by arrow A. This is a crank/connecting rod arrangement. During normal operation, when the transmission unit is coupled, as the torque shaft rotates the gear 151 also rotates as does gear 153, and via linkage 155 the piston 161 reciprocates in the cylinder 163. As the piston 161 reciprocates, the hydraulic fluid travels from end to end via the bypass line 165 through open control valve 169. When it is desired to decouple the transmission unit, the control valve 169 is closed. That will prevent the piston from moving within the cylinder 163, as the hydraulic fluid will be substantially incompressible. That, in turn, will prevent the gear 153 from turning, which will also prevent the gear 151 and thereby the attached torque shaft 109 from rotating. An air pocket 167 is provided in the bypass line to prevent sudden stoppage and therefore shock as the valve 169 is quickly closed. As the torque shaft cannot rotate, the transmission unit is decoupled, because positive and negative torque are both applied to the transmission housing and the input and output members are free to rotate without affecting one another. Other mechanisms could also be used to decouple the transmissions. For example, the gear 151 could be replaced by a brake disc, and a caliper could be provided to frictionally restrain movement of the torque shaft 109.

Another alternative is shown in Figure 4, and utilises the second clutch 135 between the torque shaft 109 and the fixed housing or support 103 to decouple the transmission. Only one half of the clutch arrangement is shown in Figure 4, although it will be appreciated that the lower half will be of the same configuration. As can be seen from Figure 4, the one¬ way clutch 135 (which, for example, may comprise a pair of discs, one of which is mounted on the shaft and one of which is mounted in a housing) is housed in a clutch housing 173. In this embodiment, the clutch housing 173 is rotatable relative to the main fixed housing or support 103 of the transmission unit. The housing 173 includes or carries a brake disc 175, and a brake caliper 177 is fixed relative to the fixed housing or support 103 of the transmission unit. During normal operation when the transmission is coupled, the housing 173 of the clutch 135 is fixed relative to the fixed housing or support 103 by the caliper 177 which grips and frictionally restrains the disc 175 and thereby the housing 173. In that configuration, negative torque on the torque shaft 109 is transmitted via the clutch 135 to the fixed housing or support 103.

The clutch 135 can be decoupled by releasing the brake caliper 177 so that the clutch housing 173 of the clutch is free to rotate relative to the fixed housing or support 103. The positive gyroscopic torque initially acting on the torque shaft 109 will rotate the torque shaft up to synchronise with the output member 133 of the transmission, at which point the first one way clutch 131 will transmit positive torque to the output member 133. During the negative phase of the transmission, the torque shaft will slow to zero and, as the clutch housing 173 can rotate relative to the fixed housing or support 103, will then continue to accelerate in a negative direction - the negative torque will be carried by the torque shaft but not transmitted to the fixed housing. As the transmission again undergoes a positive phase, the torque shaft will accelerate in the positive direction back to zero rpm, and will then accelerate towards the rotational speed of the output. However, the configuration is such that the rotational speed of the torque shaft will only just reach the rotational speed of the output member 133 before decelerating again, meaning that no torque will be transmitted to the output member 133 of the transmission. As such, the transmission is decoupled. When it is desired to recouple the transmission, the caliper 177 can again be used to frictionally restrain the disc 175, preventing movement of the clutch housing 173 relative to the fixed housing or support 103, so that negative torque is again transmitted to the housing and positive torque is transmitted to the output member. There would be advantages in using a relatively heavy clutch housing 173 or disc 185, so that the rotational speed of the torque shaft in the negative direction does not become excessive. The rotational movement of the clutch housing 173 could alternatively be controlled by a gear mechanism similar to that shown in Figure 3.

An advantage of the decoupling mechanisms described with reference to Figures 3 and 4 is that the change from a coupled configuration to a decoupled configuration can be made very rapidly.

Other mechanisms for decoupling could be used. For example, if the rotor speed is independently controllable relative to the input speed (via an electric motor or the like), the rotor speed could be slowed to zero rpm, so that no torque is transmitted to the transmission output. In that embodiment, the mechanism to decouple the transmission will comprise the speed controller for the rotor.

Another alternative is to adjust the inertia of the torque shaft. A flyball type arrangement is shown in Figure 5a. In that embodiment, the torque shaft 109 of the transmission is connected over a one-way clutch 135 to a fixed housing or support 103 and over an opposed one-way clutch 131 to an output gear 133. A pair of elbow linkages 201 are hinged at 203, 205 and 207. Masses 209 are carried by the elbow linkages. A thrust bearing 211 is provided between a shoulder 213 on a shaft 215 and the elbow linkages 201, so that when the torque shaft rotates 109 the elbow linkages can also rotate but the shaft 215 can remain stationary. A gear 217 is mounted on a screw thread on the shaft 215 and engages with a gear 219 which is driven by a servomotor 221.

During operation, the effective inertia of the torque shaft 109 is altered by rotation of the gear 217, which as a result of the screw thread moves the shaft 215 linearly along the axis of the torque shaft causing the masses to move radially. When the masses 209 are at their outermost positions, the torque shaft inertia 109 will be at a maximum, thereby effectively decoupling the transmission by preventing the torque shaft from reaching the output speed. When the masses 209 are at their inner positions, the torque shaft inertia will be at a minimum, such that the transmission is coupled. This method of decoupling is possible only if the output speed is significant, as the decoupling is achieved when the torque shaft can not reach the output speed.

Another alternative is shown in Figure 5b. A flywheel 231 is mounted on bearings 233 on a linkage member 235 which is pivotally connected at pivots 237 to linkage members 239, 241. One linkage member 239 is pivotally connected to the torque shaft 109 of the transmission which is mounted in a double thrust bearing 243 in the fixed housing or support. The other linkage member 241 is pivotally connected to a shaft 245 which is mounted for rotation in a double thrust bearing 247 in a housing 249. The angle of the linkage member 235 upon which the flywheel 231 is rotatably mounted is adjustable by axial movement of the housing 249 and thereby the shaft 245. In the position shown, the contribution of the flywheel to torque shaft inertia is at a maximum, and the transmission is decoupled by preventing the torque shaft from reaching the output speed. When the axis of the linkage member 235 coincides with the axis of the torque shaft 109, the contribution of flywheel inertia to the torque shaft is zero, and the transmission of torque is at a maximum.

Any of the decoupling arrangements of Figures 3 to 5b could be used with a reciprocating- type GVT unit such as shown in Figure 2b or 2c.

While other types of continuously or infinitely variable transmissions could be used in the regenerative braking system, it is preferred that the transmission units are gyroscopic variable transmissions. By using GVT's, it is not necessary that external clutches are provided to decouple the transmission units, rather decoupling can be achieved by internal or internal mechanisms as described above. Further, the reciprocating GVT has a wide range of speed ratios, defined as the ratio of the rotational speed of the output member relative to the rotational speed of the input member. The speed ratio may be as high as 30:1 with a reciprocating GVT, which is significantly greater than the 5:1 maximum that may be typical for other types of CVT' s or IVT' s - due to the nature of the GVT. This is particularly advantageous for spinning up the flywheel to a greater speed, and the resulting high speed ratio gives a high braking effort on the road wheels, approaching that of disc or drum brakes.

Figure 6 shows an alternative embodiment drive and regenerative braking system which, while it may be used with GVT units, is particularly suitable for use with infinitely variable transmission (IVT) units. Unless described below, the features and functioning of the system should be considered to be the same as in Figure 1, and like reference numerals indicate like parts with the addition of 300. In this embodiment, the transmission units 313, 321 are IVT units, such as shown schematically in Figure 7. The IVT unit shown in Figure 7 has a rotatable input member 401 operatively connected to a sun gear 403. The sun gear is coupled to an output member 405 via a planet carrier 406. 407 are pinions of the planet carrier. The pinions engage a ring gear 409 which is operatively connected to a continuously variable transmission (CVT) 411 which acts as a variator and is operatively connected to the input member 401. It will be appreciated that the configuration of the gear components in the FVT could be changed from that shown in Figure 7, but the FVT unit will generally have a planetary gear set and a continuously variable transmission, with the energy being recycled through the CVT. The block arrows in Figure 7 indicate the possible power flow directions through the FVT unit.

The first FVT unit 313 is connected to the output shaft 315 over a one-way clutch 320. The second IVT unit 321 is operatively connected to the flywheel 323 over a one-way clutch 326. When the drive shaft 307 is to drive the road wheels 317, a decoupling brake 319 is released. The output member 405 of the IVT unit will then be operatively connected to the output shaft 315 over the one-way clutch 320. When the speed of the output member 405 reaches the speed of the output shaft 315, torque will be transferred to the shaft 315. When the transmission unit 313 is to be decoupled, the brake is actuated, thereby locking the output member 405 of the transmission. Any reverse drive from the road wheels 317 will not be transmitted back to the transmission, and the one-way clutch 320 will freewheel.

Similarly, when the vehicle is to be slowed, the first transmission is decoupled, and a decoupling brake 325 is released thereby coupling the second transmission 321 to the flywheel over the one-way clutch 326. When the speed of the output member 405 of the second transmission 321 reaches the speed of the flywheel 323, torque will be transferred to the flywheel 323. When the system is to propel the vehicle again, the brake 319 is released thereby coupling the first transmission, and the brake 325 is actuated thereby decoupling the second transmission. Any reverse drive from the flywheel will not be transmitted back to the second transmission 321, and the one-way clutch 326 will freewheel.

A selectable reversing gear arrangement 335 may be provided in the system of Figure 1 and Figure 6 to enable the vehicle to be driven in reverse by the source of motive power 311.

In the above systems, control systems will be provided to control the decoupling mechanisms for the transmissions, and to control the operation of the GVT units (for example the spin speed of the GVT rotor), if one or two GVT units are used.

The above described drive and regenerative braking systems are particularly useful for internal combustion engines, and enable regeneration of some of the energy normally lost while braking. By regenerating some of the normally-lost energy, fuel consumption can be reduced. Such a system is particularly useful for trucks which, due to their weight, rely heavily on engine/transmission braking - and due to the large distances traveled, generally have high fuel consumption.

Further, due to the use of the one-way clutches 31, 33, 131, 131', 135, 135', 331, 333, 320, 326 (depending on the embodiment), despite the relatively high inertia of the flywheel and the vehicle overall, shock loadings are substantially eliminated without the use of complex control systems. At each one-way clutch, torque can only be transmitted between neighbouring components once the speed of the first component is substantially the same as the speed of the second component. That substantially eliminates shock loadings.

It should be understood that the above describes preferred forms of the invention and modifications made thereto without departing from the scope of the invention as defined by the following claims. For example, the systems are each described as having a first one-way clutch 31, 331 and a second one-way clutch 33, 333. Instead of using one-way clutches, first and second conventional clutches could be provided. The clutches could be selectively operated by a feedback control system which would sense the speed differences and torque direction between shafts so that the shafts are coupled when the speed difference approaches zero from say a positive value but decoupled when the torque direction changes so that the speed difference is increasing towards a positive value. However, it is preferred that the one-way clutches are used, as they are less complex and provide smooth engagement and disengagement.