HYBRID KINETIC DRIVE SYSTEM
An economic solution for Hybrid Vehicle (including Plug-in Hybrid
Vehicle). A novel Hybrid-Technology
using a flywheel and an Infinite Continuously Variable Transmission to perform
an additional source of power.
1. The benefits of Hybrid
Technology
Although all passenger cars need just a few horse-powers to keep running at 60km/h they are often equipped with engines of 100HP or more for desire acceleration. Consequently such large engines operate most of the time far under their capacity resulting in low efficiency and gasoline utility.
Hybrid vehicles deploy a second source of power to drive the vehicles at low speed, to provide additional power during acceleration and to recuperate some energy during deceleration. That helps in reducing the engine capacity and permits the engine to operate at optimum conditions to achieve high thermal efficiency, affording good gas mileage and less pollution.
2. Hybrid Kinetic Drive System
The
Hybrid Kinetic Drive System (HKDS) is a novel class of hybrid technology.
Similar to the drive system of the Hybrid Electric Vehicles (HEVs), HKDS also
contains two power
sources. While the HEVs use electrical
devices (motor/generator(s) and battery) as the secondary power source, HKDS
deploys a mechanical module entitled Flywheel Infinite-CVT Combine (FIC).
An FIC includes a small flywheel
(02), a continuously variable transmission (CVT) (03), a planetary gearset (04)
and a reduction gearing (05) that connects the flywheel to the other devices
(see Block diagram 01).
The flywheel functions as an energy
storage device. The CVT performs a
two-way transmission of energy between the flywheel and the load
(vehicle). The planetary gearset enlarges
the speed range of the load, creating an infinite speed ratio so that the FIC
is able to mobilize a vehicle from rest or to slow down the vehicle to a
complete stop.
The CVT smoothly varies its own
speed-ratio and varies the speed-ratio between the flywheel and the load as a
result. As the speed-ratio between the flywheel and the load decreases the
flywheel provides energy to run and accelerate the vehicle. When braking takes place, the speed-ratio
increases, the kinetic energy is recovered from the slowing-down vehicle to
increase the spinning speed of the flywheel.
Power transmission depends on the
rate of change of the speed-ratio: faster variation of the speed-ratio results
in a higher power transfer between the flywheel and the vehicle. Since the energy storage at the flywheel is
already in dynamic form, the power capacity of the FIC depends solely on the
CVT’s capacity. In order to minimize the
frictional lost and for smooth driving, the FIC deploys a newly invented CVT called
Internal-Tracing CVT (ITCVT) which is able transfer power sufficiently as
required in acceleration and in regeneration.
The required
energy storage at the flywheel depends on the vehicle size and the cruising
speed to be achieved solely with the FIC.
For a typical cruising speed of 14m/s (50km/h), a medium size passenger
car requires a net energy storage of 450Kj as can be provided by a composite
flywheel of 7kg and 14cm diameter spinning at 72,000rpm. The required energy storage would be reduced
to below 300Kj for a compact car with the cruising speed of 8m/s (29km/h).
To
minimize the frictional loss, the flywheel needs hi-tech bearings and a vacuum
housing. By the safety concern, it may
need a jacket that is able to absorb all releasing energy without breaking
apart.
Storing energy by spinning an object at high speed seems to be a dangerous potential. However, the flywheel on this system is not the only one runs that fast. The turbo chargers may spin up to 120,000rpm or faster. At that fast, certain large turbo chargers store as much as 500kj. Concerning the working condition, (high temperature, the shape and material of the turbine and the pump) the turbo chargers have much higher risk of explosion than the flywheel on the HKDS. Note that the turbo chargers are not designed with the safety jackets. When applying on larger vehicles (vans, buses …) the FIC needs a higher storing energy. Instead of a large flywheel, a series of small flywheel connecting together could be used. This solution may help in design the safety jackets, insuring that the jackets able to hold all broken parts.
As shown on the block diagram 01, the synchronic clutch (07) is used to shift the connection from the engine to the FIC or to the load, permitting engine power to flow to the load with or without passing through the FIC.
HKDS is thus a multi-drive system,
performing more than one drive-line between the engine and the load to permit
load driving by the engine or by the FIC or by both of them. HKDS also permits power from the engine to
flow to the load without passing through the FIC. In operation, around 70% energy from engine
is transferred to the load through this drive-line with gearing efficiency.
That greatly reduces the frictional lost at the CVT and improves its working
lifetime as well.
In operation, the FIC has 4
functions
1.
Provide
power to run the vehicle with the engine shut-off.
2.
Supply additional energy during acceleration.
3.
Recover energy during
deceleration.
4.
Drives the vehicle
while the shifting occurs at the 2-speed gearing unit.
When
the vehicle runs at low speed, the FIC is the sole source of power. The engine
operates intermittently to recharge the flywheel.
When the vehicle runs faster, the engine starts and the vehicle is driven by two sources of power. When cruising or running with low resistance, the power is supplied by the engine only. The FIC is used in acceleration, deceleration and shifting processes.
Go to 4. Detail Description for
more information on the ITCVT and the HKDS.
Desire acceleration requires about 100hp while the max output of a Nickel-Metal Hydride (NiMH) battery of 60kg is about 30hp and the max input is much lower than that. As the battery supplying max output, as much as 50% of the energy drawn from a battery is a thermal loss due to the internal impendence. In addition, energy has to be transformed from chemic to electric then dynamic form to run the vehicle and another trip from dynamic back to chemic when recharging. That turns a great percentage of energy into heat at the electrical devices.
It is clear that heavy battery and the other electrical devices required for hybrid electric vehicles would bring-up the production cost several thousands more than comparable car with conventional gas engines. The high costs of production and maintenance are the major weaknesses that obstruct the HEVs to be widespread. In fact, the HEVs need financial help from the local governments to get to the market.
HKDS does not comprise electrical devices. With lower production and maintenance cost, HKDS promises an interesting over all saving. In the other hand, HKDS does not have difficulty on performing power capacity. With a reasonable size and operation speed, the ITCVT is able to transfer the power in acceleration and deceleration sufficiently, providing a great driving performance, and bringing the HKDS to be ideal drive system for sport car.
The high power comes from the FIC is much more helpful in minimizing the engine capacity and permits it operate with optimum thermal efficiency. It also permits regenerate braking energy with high rate. With these mentioned advantages, HKDS promises significant higher gas mileages in comparison to the HEVs.
3. Further Applications
·
HKDS for
the Intercity Buses.
Speed-up and braking are frequent occurrences in the common operation of intercity buses. Every time a full bus of 12 metric ton is stopped from 50km/h, around 1 000kj of kinetic energy is dissipated as heat at the brakes. If a bus stops every 250 meters, the dissipated energy is 3 times the energy used in against the road load and air resistance.
Air pollution and the enormous braking energy being lost are the impetus for some manufacturers of Hybrid Electric Bus. However, an effective electric-system requires high power-capacity electric devices (up to 200Kw). Large and expensive electric devices turn the Hybrid Electric Bus into a bad economic solution even if thousands of gallons of diesel can be saved a year.
The HKDS is not on the question of power capacity. An ITCVT on a bus can be built as large as needed to effect two way energy transmissions between the flywheel and the load. It is feasible to build a FIC with a sufficient torque capacity to accelerate or decelerate at 4m/s-s. That allows the FIC to stop the bus without braking (except emergency braking), bringing the rate of regeneration up to 70% or higher.
The additional power from the FIC provides the desired acceleration to enable the use of engine power below 50kw in the whole speed range from 0 to 60km/h, permitting deploy a small gasoline engine for lower cost and weight and for reducing noisy as well as emission.
Installation of HKDS on intercity buses involves no energy loss at the torque converter or loss at idling. The engine always operates with higher thermal efficiency and more than 70% kinetic energy is recovered at braking. It is estimated that two third of fuel may be saved with obvious pollution abatement.
·
HKDS for
Plug-In Hybrid Vehicle
Most large cities have to deal to the getting worse air polluted problem that exhausted from the internal combustion engines. Automobile advance technology could not adapt to the increasing number of running cars.
Electric cars have been advanced as a means of pollution abatement. However, an electric vehicle has a limited travel distance between charging. Since electric vehicles use high capacity batteries, a full recharge takes much more time than filling a gas tank even at a high current source. Cost and weight of the electric devices are also disadvantages of the electric vehicles.
One type of hybrid vehicles, often known as plug‑in hybrid vehicle, also contains two sources of power similar to the HEV but with higher capacity battery to drive the vehicle a preferable distance. The plug-in hybrid vehicles overcome the issue of travel distance but their popularity is even more severely affected by the cost factor.
The most difficulty task in building an electric vehicle relies on the power capacity required at electrical source. Even running in city, a medium size passenger car needs at least 50kw for acceptable acceleration. In city, vehicle speeds-up and slows-down frequently. Very often, when speeding up, the power needed may go up to 40kw or higher. To supply the required power effectively, it needs a high power motor/generator and quite large battery or battery and capacitor. The adding cost, the weight of the electric devices and the inconvenience recharging are the major concerns must be solved to put the electric vehicles on the market.
HKDS improves the acceptability of hybrid electric cars. Firstly, it reduces the required capacities of the electric motor and the battery. Secondly, it minimizes the loading power from the battery thereby reduces the energy loss due to the internal impendence at the battery. Thirdly, it permits an effective recovery of the braking energy.
There have some solutions in adding the electric motor/generator on the system. One among them, illustrated on block diagram 02, deploys two synchronic clutches (07) and (08). The synchronic clutches (07) is used to connect the engine to the electric motor or the FIC or the differential or to connect the electric motor to the FIC. The synchronic clutch (08) is used to connect or disconnect the electric motor to the differential (see detail description).
In city
running (up to
The capacity of the electric motor varies with the size of the vehicle. A medium passenger car needs around 5kw to run at a steady speed of 70km/h. An 8 to 10kw electric motor would be adequate to start the engine and to run the car in the city.
The composite drive system limits the electric power under 6Kw. That may bring-up the battery average efficiency to higher than 90% and also provide more options in choosing the type of battery for longer cycle life, higher energy density and lower costs.
The battery capacity also depends on the desired travel distance. A compact car needs around 250kj to cover 1km distance in city. As an example, a Nickel-Metal Hydride (NiMH) battery pack (300 cells, 65kg) having nominal energy storage of 2.34kwh would be able to run the car 25km or 30 minute sufficient for city uses. That would allow the driver getting out and in his city or going to market then back home. The battery can be fully recharged within 2 hours at a home current source or can be quickly recharged (less than 20 minute) at 10Kw sources. When this type of vehicle is widely used, driver can recharge his car battery at the parking lots at the markets or restaurants.
Generally, it costs around 0.1 $CAN of gasoline per Km driving in city. By electricity, the cost is below 0.01 $CAN.
The benefits of this solution may be summarized as follows:
1. Travel distance is not limited by battery capacity;
2. Reduction of fuel usage;
3. Reduction of the capacities of the electric motor and battery with accompanying lower production cost;
4. Convenient recharging;
5. High driving performance;
6. Possible overall savings.
Installation of HKDS on plug-in hybrid vehicles may prove to be a realistic and economical solution in the fight against pollution, in reducing the green house effect and solve the air polluted problem at large cities.
We are in the
process of building prototypes and we are seeking partners and/or
collaborators. We invite inquiries and we are
ready to provide more details of the invention. Please feel free to contact us.
4. Detail Description
4.1 Internal Tracing CVT
The CVT on a HKDS transfers energy between
two large moment inertia objects (the flywheel and the vehicle) by varying the
speed ratio. The variation of the speed ratio must be quite smooth. A small jump at the speed ratio may lead to
jolt, vibration and damages at related components. In order to regenerate braking energy
effectively, the system also requires a CVT that has a high capacity and fast
speed ratio change.
The V-Belt CVT seems not to be
suitable for the FIC by the way it handle the speed ratio and its limited
capacity. The speed ratio at a V-Belt
CVT is the ratio between two effective radii of the sheaves. The effective radius of a sheave is not
varied by the distance between two halves of the sheave only. It is also varied due to the operation speed
and especially due to the driving resistance.
That characteristic will lead to jolt and vibration, especially during
regeneration. In addition, even running
without load, there is always a tension needed on the belt to maintain it in
shape, causing a significant frictional loss at the bearings and the belt.
Another type of CVT, well known as Half-Toroidal CVT, is applied by Nissan automobile company on their Cedrid and Gloria vehicles. In compare to V-Belt CVT, the fundamental advantages of the CVT include a higher torque capacity and faster ratio changes. The CVT may be classified as a tracing drive, a drive that transfers power through the small areas called contact-zone by clamping the drive components together. As the CVTs running without load, the clamping force is minimized, resulting to lower frictional loss in comparison to at the V-Belt type.
While the Toroidal CVTs use the rollers as the intermediate members to transfer power from driving to driven components, the ITCVT transfers power directly between drive components. That makes the ITCVT become more compact and simpler in controlling the speed ratio. Beside the advantage of lower production cost, the compact design of the ITCVT also allows multiplying the number of the contact zones as well as enlarging the effective radius, results higher capacity and efficiency.
A typical Internal-Tracing CVTs is illustratively shown in Fig.01 and Fig.02. Fig.01 shows the transmission at the speed ratio of 1:1. Fig.02 shows the transmission at the speed ratio of 3:1. In the figures, there are a number (n) of cones (01) mounting on an inner shaft (03). The cones are designed in a way so that they can move along the axial, vary the distance between them. Inserted between the cones is a number (n-1) of plates (02) that is mounted inside a drum (04). The drum is mounted on the support (05) by bearings. As shown in detail view of a plate (Fig.02), two tracing surfaces are formed at both sides of the plate.
A ring gear (06), mounted on the drum, is used to transfer the power from the plates to gear (07). The support (05) is mounted on the housing by journals (08). The center-line of the journals is coincident to the one of the gear (07) so that the support can turn around this center, varying the distance between the center lines of the cones and the plates while maintaining the distance between centers of the gears (06) and (07).
The clamping force is provided by hydraulic pressure that applies on the outer face at one end cone. A sensor is needed to measure the driving resistance. Due to the driving resistance, the clamping pressure is controlled. A hydraulic cylinder (09) is used to control the speed ratio by varying the distance between the center lines of the cones and the rings.
In operation, by the clamping pressure, the cones contact to the tracing surfaces at the small areas called contact zone. The effective radius is the distance between the center-line to the center of the contact zone. The speed-ratio from the cones to the plates is provided by the equation: i = r2 / r1 where r1 and r2 are the effective radii of the plates and the cones respectively. As the hydraulic cylinder active, the drum turns around the center-line of the gear (07). At the same time the cones move along the axial, keeping contact to the plates at the tracing surfaces. As the drum turns around the center-line of the gear (07), it varies the effective radius r1 of the cones then varies the speed-ratio as a result.
As the speed ratio getting close to 1:1, the contact zone develops more rapidly and finally it has a donut shape as the speed ratio gets 1:1. At this specific speed ratio, the whole CVT runs at a same speed. The CVT may be considered as a solid unit, transferring 100% energy from driving to driven components. This unit feature permits the ITCVT having a high capacity and efficiency as it operates at a speed ratio range close to 1:1. In assembly, a speed ratio close to 1:1 is used to start the vehicle from rest.
On tradition automatic transmission applying a CVT, the moment inertia of the CVT becomes a resistance as the engine speeding-up. The size, weight and the operation speed of the CVT should be limited. The HKDS operates different. Most energy used in acceleration comes from the flywheel. The engine does not need to speed-up in order to accelerate the vehicle. That allows deploying a CVT as large as needed for required capacity and for life time working.
4.2 Typical HKDS
A Kinetic Drive System mainly
includes a 2-speed (or 3-speed) gearing unit (06), a synchronic clutch (10) and
a FIC. The FIC contains a flywheel (02),
a CVT (03), a planetary gearset (04) and a reduction gearing (05) that connects
the flywheel to the other devices (see Fig.03).
The planetary gearset has three
members: the sun gear, the ring gear and the planetary carrier. The sun gear connects to gear (14) that
meshes to gear (15) mounting on the drum of the CVT. The ring gear is the output of the FIC,
connecting to the differential (09) through the chain assembly (07) and the
D&R gearing (08). The planetary carrier connects one side to a shaft that
passes through the hollow shaft of the driving sprocket and connects to the
synchronic clutch (10). On the other side, it connects to
gear (16). From gear (16), power can
flow to two directions: to the CVT through gear (17) and to the flywheel (02)
through the reduction gearing (05).
At the reduction gearing there is a multi-plate clutch (12). Paralleled to the clutch (12) is a one way clutch (13). The one-way clutch is set up so that it transfers energy from the vehicle to the flywheel only. The clutches (12) serves in speeding up the flywheel and the clutch (13) serves in case of emergency braking.
The planetary gearset enlarges the
speed range of the load, creating an infinite speed ratio between the flywheel
and the load so that the FIC can start vehicle from rest or slow down it to
completely stop. In order to eliminate
the drive and reverse gearing unit, the planetary gearset may create a larger
speed range (from –x to +y) so that the FIC can perform reverse gear.
The driving sprocket connects one
side to the output of the FIC as mentioned.
On the other side it connects to the synchronic clutch (10). The synchronic clutch (10) is used to
shift the connection from the output of the 2-speed gearing unit (06) to the
planetary carrier or to the driving sprocket, permitting power from the engine can flow to the load with
or without passing the FIC.
4.2 Operation
·
Starting
HKDS needs to speed-up the flywheel for normal driving. Right after starting the engine, the first gear clutch smoothly engages the engine to the CVT then the engine speed up. As the engine speed reaches around 1,200 to 1,400 rpm, the oil cooled multi-plate clutch (12) starts engaging the flywheel. The engaging pressure at the clutch is controlled in order to maintain the engine at this speed range. As the clutch completely engaged, the engine continues speeding-up the flywheel until the engine reaches to a predetermine speed. The 2-speed gearing unit shifts to the second gear. The shifting process is briefly described as following:
The first gear clutch disengages and, at the same time, the ignition turns off (or the throttle valve closes). That makes the engine speed drop down. When both sides of the second gear clutch run at the same speed, the second gear clutch engages and the engine ignition turns on (or the throttle valve reopens). The engine continues to speed up the flywheel until it store required energy. The second gear clutch disengages and the engine shuts down.
Depending on the engine power and the storage energy needed, it may take 15 seconds or more to speed-up the flywheel. Drivers do not have to wait for such time; they can start moving the vehicle less than 5 second after turning on the switch, right after the oil cooled multi-plate clutch completely engages.
During the starting process, the CVT is set at the lowest gear-ratio of 1:1. That results to an infinite speed-ratio between the FIC and the vehicle. To start the vehicle from rest, the CVT increases its speed ratio from 1:1 at a rate proportional to the position of the acceleration pedal. That causes the speed-ratio between the between the FIC and the vehicle reduce from infinity, making the vehicle start moving. Properly control the speed ratio and the engaging pressure at the D&R gearing unit will perform a smooth starting or a crept behaviors as well.
In case the driver just needs to move the vehicle in a short distance, the oil cooled multi-plate clutch is set at inactive mode, the system operates as a traditional automatic transmission with CVT.
·
During the vehicle running, the flywheel releases its kinetic energy by reducing its speed. From rest to around 50 km/h, every time the flywheel slows-down to the low limit speed (refer to Gr.01), the engine operates, supplying power to run the vehicle and speed-ups the flywheel until it reaches the full speed.
Gr.01 generally illustrates the flywheel energy management. As shown on the Gr.01, as the flywheel slows-down from full speed to low-limit speed, it releases at least 200 Kj. The amount energy is able to run the car an average time of 3 minutes. At the low-limit speed, the flywheel can release 150 Kj at least, able to speed-up the vehicle to 50km/h or helping in acceleration or in the shifting process.
·
Regenerating,
Braking
When the driver releases the acceleration pedal, the CVT slowly increases the speed ratio. The energy from the vehicle is used to speed-up the flywheel. When the brake pedal is pressed, the oil cooled clutch releases and the FIC increases the speed-ratio faster, proportional to the pressure on brake pedal. Energy from the vehicle passes through the one-way clutch to the flywheel and the FIC functions as a brake. Higher pressure on the brake pedal will allow the brake applied. Both systems are used to stop the vehicle. In case the flywheel getting close to high limit speed (the vehicle going down a high steep slope or getting stop from high speed), more pressure is contributed on the brake system to prevent the flywheel from over speeding.
In case of an emergency brake, the FIC may not increase its speed-ratio fast enough, the one-way clutch releases, disconnecting the flywheel from the vehicle automatically.
·
Higher
than 50 km/h
When the vehicle gets over 50 km/h and when the flywheel reaches low limit speed, the engine starts. At the 2-speed gearing unit, the gear ratio is set depending on the driving resistance. In normal driving condition, the 2-speed gearing sets at the second gear (speed ratio of 1:1) and the synchronic clutch shifts the connection from the output of the 2-speed gearing unit to the driving sprocket, permitting power from engine transferring to the load without passing the FIC. As the engine operates, the vehicle is driven by two sources of power. When cruising or running with low resistance, the power is supplied by the engine, the FIC functions as a “follower”, varying its speed ratio due to the actual situation. The clamping pressure at the CVT is minimized and the speed ratio is controlled so that the flywheel runs at the full speed.
In case the vehicle runs with driving resistance higher than the engine can supply, the FIC provides adding power. As the flywheel speed drops to low-limit, the 2-speed gearing unit shifts down to lower gear, permitting the engine to supply more power. During the shifting process, the FIC supplies power needed. The 2-speed gearing unit has time to perform a quite smooth shifting.
In case the vehicle runs with much higher driving resistance (go up hill or high acceleration), the engine may start earlier (before 50 km/h), the 2-sppeed gearing is set at the first gear, allowing the engine operating at higher speed, performing more power.
As the driver releases the acceleration pedal, the clutch at the 2-speed gearing unit releases. That allows the engine dropping to idle speed. When the driver reapplies the pedal, before the engine getting enough speed to engage the clutch, the vehicle is driven by the FIC.
When the driver shuts-off the vehicle, a generator (that connects to the reduction gearing) transfers the flywheel’s energy into electricity, recharging the battery.
4.4 Typical drive system for Plug-in Hybrid
Vehicle
Fig.04 partially shows a drive system for Plug-in Hybrid Vehicle. There is an electric motor/generator (18) added. Its output, gear (19), meshes to gear (20) that is supported by a hollow shaft thereby the connections from the driving sprocket and the planetary carrier can pass through and reach the synchronic clutch (10). The gear (20) also connects one side to the synchronic clutch (10). On the other side, it connects to another synchronic clutch (21) that permits engaging or disengaging the electric motor and driving sprocket. As mentioned, the synchronic clutch (10) is used to connect the engine to the electric motor or the FIC or the differential or to connect the electric motor to the FIC.
The synchronic clutches permit the electric motor to start the engine, to perform reverse gear and recharge the battery when needed. That helps eliminating the starter, generator and drive-reverse gearing.
The two gears (19) and (20) provide
an additional gear ratio, helping in reduction the torque capacity required at
the motor. In another concept, for fewer
components, the gear (20) could be replaced by a rotor of a thin and large
diameter electric motor/generator.
4.5 Operation
For the Hybrid Plug-in Vehicle, drivers do not need to wait for speeding up the flywheel. The electric motor, after starting the engine, turns its connection to the differential and drives the vehicle during the engine speeds-up the flywheel. To perform reserve gear, there is no clamping pressure at the CVT thereby disconnects the FIC from the drive system and permits its output to run in opposite direction.
When the flywheel reaches recommended speed, the engine is disconnected and shut-down; the vehicle is powered by the FIC and the electric motor. The synchronic clutches permit the electric motor connecting to the FIC or to the driving sprocket to drive the vehicle and maintain the flywheel at a recommended speed. Since the electric motor/generator can supply power permanently, the net energy storage required at the flywheel could be from 250kj to 300kj.
When the vehicle runs faster than 70km/h, the engine starts and the vehicle is driven mainly by the engine and the FIC. The electric motor/generator could be considered as a secondary adding power source, helping in reducing the capacities needed at the FIC.
The engine also operates when the battery’s energy reaches to a low level. When running in city (up to 70km/h), as the engine operates, it supplies power to drive the vehicle, maintain the flywheel speed and recharge the battery until the battery achieves 10% to 15% its nominal energy storage so that the battery can supply power to run the vehicle during the engine shut-off.
We invite you to examine the document and would be eager to respond to any question that you might have.
Please feel free to contact us.
Ducquang Tang
514-596-2850