GB2463136A

GB2463136A - Hybrid vehicle with a stability control module and a drivetrain that includes a flywheel

Info

Publication number: GB2463136A
Application number: GB0914213A
Authority: GB
Inventors: Timothy James Bowman; Robert Colin Helle-Lorentzen; Donatus Andreas Josephine Kees
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2008-09-04
Filing date: 2009-08-14
Publication date: 2010-03-10
Anticipated expiration: 2029-08-14
Also published as: GB0914213D0; CN101665081A; GB2463136B; CN105835680A; GB0816109D0

Abstract

A hybrid vehicle comprises a prime mover such as an internal combustion engine 2 and a flywheel 9 as a secondary mover. The engine 2 is connected via a gearbox and final drive assembly 4 to a first set of wheels 3. Flywheel 9 drives a second set of wheels 5 and is part of a drivetrain comprising a differential 7, a propshaft 8, an electro hydraulic clutch 11, an oil pump 12, reduction epicyclic gearing 13 and, for example, a continuously variable transmission (CVT) 10. An electronic control module (ECM) 14 receives inputs form various sensors 16, 17, 18 and from a stability control module 24 which, via the ECM 14, sends a signal to the drivetrain that is configured to operate in response to the signal. The arrangement permits all wheel drive and stability control of the hybrid vehicle.

Description

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HYBRID VEHtCLES This invention relates to drivetrains for vehicles and particularly to hybrid vehicles having a prime mover and a s secondary mover incorporating a flywheel.

SAE technical paper 2008 -01-0083, April 14-17, 2008, describes an arrangement consisting of a continuously variable transmission (CVT) connected between the engine and io gearbox of a vehicle and configured to drive a flywheel through a gearset. The arrangement can add or subtract power to that supplied by the engine to a driven pair of wheels of the vehicle. The flywheel can be spun up to engine speeds and can potentially reach higher speeds under vehicle braking conditions. Typically, flywheels are composed, at least partly, of carbon fibre and operate in an evacuated chamber so that aerodynamic losses are minimised.

Additional gearing can be provided to allow ancillaries such as air conditioning and power steering to be driven by the flywheel.

US 2008/0105475 discloses an automotive vehicle having a powertrain for the vehicle, a flywheel and a continuously variab1e transmission which interconnects the powertrain and the flywheel. When the vehicle decelerates, energy from the powertrain and its associated transmission is transferred to the flywheel. When the vehicle accelerates, the energy of the flywheel is transferred to the powertrain.

The present invention comprises a hybrid vehicle having first and second sets of wheels and having a power source for driving the first set of wheels and a drivetrain including a flywheel and a transmission having a continuously variable gear ratio for driving the second set of wheels, and a stability control module wherein the drivetrain is configured to operate in response to a signed from the stability control module.

The prime mover may be an internal combustion engine or an electric motor for example.

A drivetrain in accordance with the invention can be easily integrated into an existing vehicle platform having front wheel or rear wheel drive.

The transmission may be an infinitely variable transmission having a geared neutral.

In a preferred embodiment, the transmission is a continuously variable transmission (CVT) and the drivetrain is further includes a clutch located between the CVT and the flywheel.

By virtue of the invention, the energy in the rotating set of wheels which is not being driven directly by the vehicle's prime mover (e.g. internal combustion engine) can be stored in the flywheel and later released to drive said set of wheels. Manipulation of the transmission ratio and clutch achieves control of energy storage and recovery.

When the ratio of the CVT is changed so as to speed up the flywheel, energy is stored and when the ratio is changed so as to slow down the flywheel, energy is recovered and transferred to the wheels. In one mode of operation, the clutch is open while the vehicle is moving at a constant speed and then closed when decelerating, allowing the flywheel to spin up.

The invention has an advantage over known arrangements where the flywheel and prime mover are driving the same set of wheels because there is no need to integrate the additional components of the arrangement into the engine compartment. Therefore, there is no requirement to upgrade engine mounts to withstand the additional weight and processional forces created by the flywhee],.'s motion furthermore, there is no need to modify the existing drivetrain in order to create an input/output path for transferring drive (energy) to and from the flywheel.

Preferably a reduction gear is located between the transmission and the flywheel.

The reduction gear may be an epicyclic gear ic arrangement.

The reduction gear enables a high speed flywheel to match the lower operational speeds of the CVT.

The higher the rotational speed of the flywheel, the greater the energy stored In order to extend the available ratios of the transmission (and particularly a CVT finite ratio range is typically (six) an optional gear set may be provided. This may take the form of a gearbox for connection between the second set of wheels and the transmission. The gearbox may have two or more ratios.

A CVT requires a pressured oil supply in order to operate and in particular to set a ratio. Hence a pump is required. A mechanical pump is preferred to an electrical one because of its superior efficiency. Preferably the oil pump is located between the transmission and the second set of wheels so that it may be driven by said set of wheels.

This configuration is preferable to having the pump driven by the flywheel as under certain vehicle operating conditions, the flywheel speed can be zero and therefore, oil pressure would also be zero. When oil pressure is zero the CVT is unable to change gear ratio. In situations where it is desirable for the transmission to change gear ratio when the vehicle has come to a halt (and therefore the wheels are stationary and not driving the oil pump) then the drivetrain may be supplemented with an accumulator for maintaining a pressurised oil supply to the transmission.

Once the vehicle has been parked and therefore the drive to the flywheel has stopped, the flywheel's rotational speed will gradually decay through frictional and aerodynamic losses. This decay represents wastage of energy. Advantageously, the invention provides the further io option of including an energy conversion device which can utilise the rotational energy which has been stored in the flywheel. This device may take the form of an electric generator or alternator or a hydraulic pump for example. It may be a separate device attached to the flywheel shaft or may be incorporated as a part of the flywheel assembly.

The flywheel may be contained in an evacuated housing which may have a vacuum pump associated therewith for maintaining a desired low pressure in order to keep aerodynamic losses to a minimum.

As a further option, an additional clutch may be located between the transmission and the second set of wheels. This has the advantage of enabling the transmission to be decoupled from said wheels when no transfer of energy between said wheels and flywheel is desired. Otherwise, the vehicle's motion would be driving the transmission unnecessarily, incurring the associated frictional losses.

Some embodiments of the invention will now be described, by way of example only, with reference to the drawings of which; Fig. 1 is a schematic block diagram of a vehicle having a drivetrain in accordance with a first embodiment of the invention, and Fig. 2 is a schematic block diagram of a vehicle having a drivetrain in accordance with a second embodiment of the invention.

With reference to Fig 1, a vehicle 1 is equipped with an internal combustion engine 2 which provides motive power to a first set of wheels 3 through a gearbox and final drive assembly 4.

A second set of wheels 5 is connected via half shafts 6 and a final drive and differential unit 7 to a propshaft 8.

The propshaft can drive and be driven by a flywheel 9.

Interposed between the propshaft 8 and flywheel 9 is a transmission unit 10 having a continuously variable gear ratio. The transmission may be an infinitely variable transmission (IVT) having a geared neutral but in this preferred embodiment, the transmission unit 10 is a continuously variable transmission (CVT) and an electro hydraulic clutch 11 is provided for decoupling the CVT 10 (and consequently the wheels 5) from the flywheel 9 under certain operating conditions.

A pressurised supply of oil is supplied to the CVT 10 by an oil pump 12 which is driven by the propshaft 8.

An epicyclic gear arrangement 13 located between the clutch 11 and the flywheel 9 provides a 10:1 reduction ratio between the CVT 10 and the flywheel 9.

An electronic control module ECM 14 receives inputs from an accelerator pedal position sensor 15, brake pedal position sensor 16, a propshaft speed sensor 17, and a speed sensor 18 associated with the flywheel. Output connections from the electronic control module 14 are made to the CVT 10 and the clutch 11.

The CVT 10 can be of conventional design whose ratio can be varied in a known manner by operation of solenoid.

Valves (not shown) which control the oil flow. Activation of the valves is under the control of the ECM 14.

s Conveniently, the CVT 10 can be of the steel belt variator type and having a ratio spread of typically six.

Some exemplary modes of operation of the embodiment of Fig. 1 will now be described.

With the vehicle running at a steady speed with light pressure on the accelerator pedal and the clutch 11 held open, no drive will be transmitted from the second set of wheels 5 to the flywheel 9 and so the latter will remain is stationary. However, oil pressure will be supplied to the CVT 10 by the pump 12 which is being driven by the propshaft 8.

If the driver should release the accelerator pedal or depress the brake pedal, this is detected by the sensors 15,16 and relayed to the electronic control module 14. Also knowing the propshaft speed from the sensor 17, the ECM 14 outputs a control signal which causes the clutch 11 to close and calculates the CVT ratio required in order to accelerate the flywheel. It outputs a second control signal in order to hydraulically control the CVT1O so that the ratio is set to the calculated value.

Hence energy is transferred from the second set of wheels 5 to the flywheel 9 rather than being dissipated as heat in the vehicle's braking system. The action of energy transference into the flywheel causes the vehicle to decelerate.

Once the ECM 14 detects that the vehicle 1 has come to a standstill (by monitoring the propshaft speed sensor 17 output), it opens the clutch 11 and the flywheel 9 continues to spin freely at a speed monitored by the electronic control module 14. The magnitude of the energy which is now stored in the rotating flywheel 9 is a function of its speed.

As the vehicle 1 commences to accelerate away from rest (detected by the ECM 14 via signals from the accelerator pedal position sensor 15 and the propshaft speed sensor 17), the ECM 14 re-sets the CVT 10 ratio to a new (calculated) io value and gradually closes the clutch 11 so that energy from the flywheel 9 is now used to drive the second set of wheels thus assisting the engine 2 in propelling the vehicle.

Hence the flywheel 9 commences to slow down until all its stored energy has been recovered (by the second set of wheels 5) and it eventually comes to rest. At this point, the ECM 14 can open the clutch 11 until it detects another deceleration manoeuvre With reference now to Fig 2, this embodiment includes the components of Fig 1 with some additional components and capabilities to be described herebelow. Components common to both Fig.1 and Fig 2 bear the same reference numerals.

A gear set 19 is located between the second set of wheels 5 and the oil pump 12, linking the propshaft 8 and CVT1O and serving to extend the ratio range of the CVT 10.

An additional clutch 20 is located between the propshaft 8 and the gearset 19.

An oil accumulator 21 is linked to the oil pump 12 and CVT 10 for ensuring that an adequate oil supply is provided to the CVT 10.

The ECM 14 has two additional control outputs, one to the gear set 19 and one to the additional clutch 20.

An alternator 22 is connected to the shaft of the flywheel 9 and has a output line 23 which can be connected with the vehicle's battery charging equipment (not shown) A stability control module 24 is electrically connected with the ECM14.

The embodiment of Fig 2 is capable of operating in the same fashion as described with reference to Fig 1.

Additionally, the embodiment of Fig 2 has the capability of decoupling not only the flywheel 9 (and epicycle gear arrangement 13) from the wheels 5 but the CVT 10 also, by means of the additional clutch 20. The additional clutch 20 is electronically controlled by the EON 14. So under conditions where is it appropriate neither to store nor release energy from the flywheel 9, the additional clutch 20 is held open. Hence, the propshaft 8 will not be driving the CVT 10 ( or gearset 19), which would otherwise unnecessarily incur frictional losses.

While the additional clutch 20 is open, there will be no drive to the oil pump 12 either so to maintain oil pressure to the CVT so that a ratio can be set in readiness f or re-engagement of the clutches 11, 20, the accumulator 21 is provided.

In this embodiment, one of three fixed, additional gear ratios can be selected (under the control of the EON 14) from the gear set 19.

The key advantage of the flywheel hybrids is the magnitude of the power that can be transmitted between the flywheel and the vehicle wheels. A road car is capable of very high power transfer during braking and the key to hybrid system effectiveness is capturing as much of this normally wasted energy as possible. This is achieved by the careful matching of the flywheel rotational speed to that of the vehicle. The rotational speed of a high-speed flywheel varies approximately between zero and 60,000 RPM or higher, whereas the vehicle's speed varies from zero to over 160 kph. There are two extremes of real-world operating s conditions. The first is when the flywheel may have zero speed and the vehicle's speed is maximum. The second is when the flywheel is at its maximum speed and the vehicle's speed is zero. To match these extreme conditions ideally an infinitely variable transmission is required, or io alternatively the CVT transmission 10 used in conjunction with the clutches. However, a CVT has a finite ratio range of typically six. This ratio range is inadequate to cover the entire operating spectrum of flywheel and vehicle speed, even with appropriately selected additional gear ratio sets.

is consequently the gear sets ratios are optimized for a given goal such as maximising fuel consumption savings on a defined drive cycle.

In this example, with a CVT ratio range of six, the ratios in the gear set are 1:1, 90% of 6 and 90% of 36.

This allows 10% of overlap between each gear selection for optirnised performance.

Selection of the gears is done electronically in a conventional fashion under the control of the ECM 14.

If the vehicle is not to be used over a long period of time, such as a weekend, say, and when it was parked, there was still a substantial amount of energy stored in the flywheel 9, then the alternator 22 can be deployed to make use of this energy. Otherwise, the rotational speed of the flywheel 9 would gradually decay to zero and the energy would be permanently lost. In such situations, the alternator 22 is activated. (This could be done by means of a driver-operated switch (not shown) for example) . The alternator 22 is configured to convert the mechanical energy of the rotating flywheel into an electric current which is -10 -used to top up the charge in the vehicle's battery (not shown) In an alternative arrangement, the ECM 14 has the capability to learn the drivers usage patterns and controls activation of the alternator 22 when it has anticipated that the vehicle will be left unused for a comparatively long time.

In an alternative arrangement of Fig 2, the oil pump 12 is located between the three speed gearset and the additional clutch 20.

In a further embodiment, shaft speed sensors (not shown) are positioned either side of the CVT 10 (i.e. between the CVT 10 and the oil pump 12 and between the CVT and the clutch 11) . These shaft speed sensors have their outputs connected to the ECM 14. They assist the ECM 14 in selecting the optimum CVT ratio (depending on the prevailing vehicle operating conditions) and permit the ECM 14 to control the slip in the clutches 11 and 12 for a smooth take-up of the drive between flywheel 9 and wheels 5.

In a further alternative arrangement, the clutch 11 and epicyclic gear 13 are transposed. This arrangement reduces the frictional losses coupled to the flywheel 9. The clutch 11, however, needs to be capable of operating at flywheel speeds but would be dealing with substantially less torque.

Flywheel operation may be employed as a means of traction control by integrating its control with an on-board stability control programme, for example. In a vehicle equipped with a conventional traction and/or stability control system, wheel slip is brought under control by automatically reducing the engine torque demand and/or applying braking effort to one or more wheels via the antilock braking system (ABS).

-11 -The present invention provides either negative or positive torque at the pair of wheels which are not directly driven by the engine. So when the clutch 11 is closed and the CVT ratio is adjusted so that the flywheel speed increases, the flywheel 9 takes energy from the wheel set 5, thereby exerting a braking effect (negative torque) on this set of wheels 5. Conversely, when the clutch 11 is closed and the CVT ratio is adjusted so as to slow down the flywheel 9, energy is transferred to the wheels 5, thereby providing a positive torque.

The ECM 14 is arranged to communicate with the vehicle's stability control module 24 and to cause the flywheel to either store or release energy in response to a command signal from the stability control module 24.

Therefore vehicle understeer and oversteer can be controlled. -12

Claims

CLAIMS1. A hybrid vehicle having first and second sets of s wheels and a power source for driving the first set of wheels and a drivetrain including a flywheel and a transmission having a continuously variable gear ratio for driving the second set of wheels and a stability control module wherein the drivetrain is configured to operate in io response to a signal from the stability control module.
2. A hybrid vehicle according to claim 1 in which the transmission is an infinitely variable transmission having a geared neutral.
3. A hybrid vehicle according to claim 1 in which the transmission is a continuously variable transmission (CVT) and in which the drivetrain further includes a clutch located between the CVT and the flywheel.
4. A hybrid vehicle according to any preceding claim, further including a reduction gear located between the transmission and the flywheel.
5. A hybrid vehicle according to claim 4 in which the reduction gear is an epicyclic gear arrangement.
6. A hybrid vehicle according to any preceding claim and further including a gearbox for connection between the second set of wheels and the transmission.
7. A hybrid vehicle according to any preceding claim and further including a mechanical oil pump for supplying oil to the transmission in which the oil pump is located between the transmission and the second set of wheels.-13 -
8. A hybrid vehicle according to claim 7 and further including an accumulator for maintaining a pressurised oil supply to the transmission when the vehicle stationary
9. A hybrid vehicle according to any preceding claim and further including an energy conversion device associated with the flywheel.
10. A hybrid vehicle according to any proceeding claim and further including a clutch located between the transmission and the second set of wheels.
11. A hybrid vehicle substantially as hereinbefore described with reference to the drawings.