Parallel hybrid drive system utilizing power take off connection as transfer for a secondary energy source

Field of the Invention

0001The present invention relates to a parallel hybrid propulsion system and controlling the system to use an electric motor to supplement drive power to wheels of a vehicle, when its internal combustion engine is driving the wheels and providing regenerative braking when the engine is not delivering power to the wheels, whereby the battery in the parallel hybrid drive system is recharged.

Background of Invention

0002A hybrid electric propulsion system is comprised of a multiplicity of power sources combined to provide traction power to the wheels of a vehicle. There are two major types of hybrid electric propulsion systems, Series and Parallel.

0003Series hybrid technology is based on all electric traction where electrical power is derived from an energy storage source such as a battery and/or capacitor where the energy storage device is charged from the AC mains, regenerative breaking and/or an on board electric generation device.

0004Parallel hybrid technology is based on the mechanical combination of a multiplicity of power sources in order to generate motive power to the wheels of a vehicle. In a parallel hybrid propulsion system, motive power is typically generated by an internal combustion engine (ICE) with additional mechanical power introduced into the motive system via an electric motor and/or other power source such as a pneumatic motor.

0005The unique technology being presented herein is based on the use of an automatic transmission which utilizes pressurized fluid and centrifugal force in order to change gears to increase the speed of a vehicle. Most automatic transmissions for medium and heavy-duty weight class vehicles (USDOT Class 6,7,8) have a Power Take Off (PTO) gear option.

0006A PTO gear is a direct connection to the power output of a transmission and is typically connected to the torque converter section of the transmission, which is a 1:1 ratio connection to the crankshaft of the ICE (once the torque converter has locked). The PTO gear is accessible via a cover plate on the external housing of a transmission. The PTO cover is removed and a PTO element is connected to the transmission's PTO gear.

0007The PTO element is a device having an input gear which meshes with the transmission's PTO gear and has and output shaft which can connect to a u-joint style driveshaft. The PTO output is typically used for driving auxiliaries such as air compressors, water pumps, and/or hydraulic pumps. PTO operation can be achieved in a stationary mode and/or while driving.

0008In the prior art patents of <patcit id="pcit0001" dnum="US6484830B"><text>Gruenwald et al. (US patents 6,484,830</text></patcit>, <patcit id="pcit0002" dnum="US6651759B"><text>6,651,759</text></patcit>, <patcit id="pcit0003" dnum="US7004273B"><text>7,004,273</text></patcit> and <patcit id="pcit0004" dnum="US7252165B"><text>7,252,165</text></patcit>), there is described a hybrid system using ultracapacitors, which couples an AC induction motor through a PTO shaft to use regenerative braking energy to help propel the vehicle

0009<patcit id="pcit0005" dnum="EP0492152A"><text>EP 0 492 152</text></patcit>, on which the preambles of claims 1 and 7 are based, discloses a vehicle power drive system comprising an internal combustion engine connected through a transmission to drive wheels of the vehicle. The transmission has a power take off and PTO output gear. A parallel hybrid drive system connected to the PTO comprises an electric motor, a battery and a vehicle monitoring and control system. The electric motor is connected through a shaft to the PTO for bi-directional power flow, and the electric motor is coupled to a pump. The battery is connected to the electric motor for sending and receiving electric power. The system can be selectively operated in a mode, in which only the engine is used to drive the vehicle and the electric motor can be simultaneously operated as generator to charge the battery, a mode, in which both the engine and the electric motor are used to drive the motor, and a mode in which only the electric motor is used to drive the motor. In any mode, the electric motor is operated as generator upon braking in order to convert the braking energy into energy for charging the battery.

Objects of the Invention

0010An object of the invention is to deploy a parallel hybrid electric propulsion system utilized the exist components found on a Class 6,7 or 8 truck or bus.

0011Another object of the invention is to provide bi-directional PTO operation.

0012Another object of the invention is the appropriate function of the parallel hybrid drive system that must include synchronized rotation between power sources.

0013Another object of the invention is the mitigation of the forces which are exerted on the internal components of the system during the above mentioned change.

0014Another object of the invention is the Vehicle Monitoring and Control System (VMCS) which oversees the various inputs to the hybrid system.

0015Another object of the invention is the use of an electric motor which is powered by a energy storage system, such as, for example, a battery system, to provide power under both driving conditions and stationary operation to an accessory system typically mounted to a conventional PTO.

Summary of Invention

0016In keeping with these objects and others which may become apparent, the present invention provides a vehicle power drive system as claimed in claim 1 and a method of retrofitting a vehicle power drive system as claimed in claim 7.

0017Thus, a parallel hybrid drive system is created utilizing the Power Take Off (PTO) connection on an automatic transmission, to act as transfer port for a secondary energy source for motive power and regenerative braking.

0018The vast majority of Class 6,7,&amp; 8 USDOT designated trucks and buses utilize transmission with a PTO gear option. The goal of the invention is to provide a parallel hybrid system which can be easily connected to some vehicles have a PTO in order to reduce fuel consumption.

0019An object of the invention is to deploy a parallel hybrid electric propulsion system utilized the exist components found on a Class 6, 7 or 8 truck or bus. Parallel hybrid drive systems which are currently being deployed by others require the use of a specialized transmission or a rework of the existing driveline at significant cost to the user. The invention discussed herein is a "add-on" parallel hybrid propulsion system which can be installed at any time during the usable life of a vehicle, at the factory or by a vehicle upfitter. The added benefit of the invention is through the use of mostly standard components, the maintenance costs, time and protocols are not changed dramatically.

0020Another object of the invention is to provide bi-directional PTO operation. As discussed earlier, the PTO output gear is connected to the engine crankshaft and relates to engine RPM directly. By applying power to the PTO input gear via an electric motor powered by a battery, the power output to the wheels is supplemented by the battery pack thus reducing the power supplied by the internal combustion engine in turn reducing fuel consumption. The electric motor can also provide drag or a negative force through the PTO element resulting in a method to stop the vehicle. The electric motor's negative force is used to charge the battery; during this phase, the electric motor functions as a generator. Those skilled in the art, refer to this as regenerative braking.

0021Another object of the invention is the appropriate function of the parallel hybrid drive system that must include synchronized rotation between power sources. In this case the power sources may be defined as a diesel internal combustion engine and an electric motor. The engine possesses the sole duty of delivering power to the transmission, while the motor will have the dual task of supplying power to the transmission and accepting power for charging (i.e. regenerative braking). The two different tasks cause the electric motor to change back and forth between working as the driver to being driven.

0022Another object of the invention is the mitigation of the forces which are exerted on the internal components of the system during the above mentioned change. The changing forces will cause the backlash within the components to reverse. For example the internal gear train of the PTO has specified tolerance values that allow backlash to occur. During operation any gear will receive contact from another gear on one side of each tooth only. The side at which the contact exists is determined by where the force is being exerted. As mentioned the forces in this system will reverse also causing the contact points to reverse. In order for the system to appropriately operate (to operate efficiency and not reduce life expectancy) all internal components must be able to accept the reversal of backlash. The potentially destructive bi-directional forces are mitigated through use of feedback control using the indexing function integrated into the electric motor assembly. Through the use of a "dampening" function within the software control algorithm the electric motor is able to reduce the potentiality harmful vibration caused by gear backlash and power transmission to the wheels.

0023Another object of the invention is the Vehicle Monitoring and Control System which oversees the various inputs to the traction system. The VMCS manages the following input/outputs in order to determine the amount and frequency of the power being applied to the PTO in order to maintain vehicle drivability and optimize overall efficiency: <ul id="ul0001" list-style="bullet" compact="compact"><li>Accelerator pedal position</li><li>Engine throttle position</li><li>Battery voltage</li><li>Vehicle speed</li><li>Torque request</li></ul>

0024During driving, two specific modes are entered: 1) acceleration mode and 2) stopping mode. During acceleration mode the system routes power from the electric motor through transmission to the wheels. During stopping mode the electric motor provides resistance through the transmission to wheels in order to create electrical energy while stopping the vehicle (also called regenerative energy).

0025Others such as Gruenwald and Palumbo '165 used a AC induction motor which produces less torque than the motor (for a given weight and size)

0026The present invention has selected a permanent magnet motor which provides the additional torque for launch assist and regenerative breaking to make the system more effective. Palumbo makes a note that the 215 frame is the largest induction style motor which can fit, which limits the power of the machine utilized.

0027The present invention also alters the way the transmission shifts now by changing the CAN (vehicle network) commands for down/up shifting in order provide undetectable power blending from the electric motor and the engine through the transmission to the wheels.

0028In addition the transmission's torque converter is locked and unlocked. The variable state torque converter on the transmission types being used with the PTO Hybrid technology is to reduce the effective-losses in the engine and torque converter during regenerative braking.

0029In this way, the vehicle monitoring and control system (VMCS) which incorporates the Driver Interface Node (DIN), Auxiliary Power Unit Controller (APUC), Charge Port Interface (CPI), Battery Management System (BMS), and the Master Events Controller (MEC) as well as other subsystems oversees control and changeover between operating modes as well as the details of power blending, shift control, torque converter locking and unlocking, damping control, and safety aspects of regenerative braking in the midst of anti-lock or stability control events.

0030Therefore, the vehicle power drive system of the present invention includes an internal combustion engine connected through a transmission to drive wheels of the vehicle. The transmission has a power take off (PTO) and PTO output gear. A parallel hybrid drive system, which is connected to the PTO includes an electric motor, an energy storage system (such as, for example, a battery system) and a vehicle monitoring and control system (VMCS). The electric motor is connected through a shaft to the PTO for bi-directional power flow. Typically, the electric motor operates an accessory device such as a hydraulic pump, an air compressor and a mounted accessory. The energy storage system is connected to the electric motor for sending and receiving electric power. The vehicle monitoring and control system (VMCS) has: <ol id="ol0001" compact="compact"><li>a) a first, accelerating mode for delivering electric power from the energy storage system to the electric motor, to provide drive power to the transmission for - supplementing drive power being delivered by the engine to the wheels of the vehicle and,</li><li>b) a second, deceleration mode having the electric motor receive shaft power from the PTO while acting as a generator, to provide regenerative braking and recharging the energy storage system when the engine is not delivering power to the wheels, wherein further the PTO can be disengaged from the transmission, allowing the electric motor to freely provide power to the aforesaid accessory device from the energy storage system.</li></ol>

0031The PTO is connected to a PTO output gear in the transmission. The aforesaid energy storage system preferably includes a battery pack, a battery charger for charging the battery pack using an outside electric power source, and a battery management system.The electric motor can have an optional auxiliary power take off, which can be disengaged when the VMCS is in the first mode. The VMCS optionally includes a dampening function to reduce vibration and gear backlash in the PTO when engaging either a switching mode, wherein the dampening function monitors the velocity and direction of the electric motor and the PTO output gear and adjusts the velocity and speed of the electric motor, thereby creating a closed-loop feedback loop to ensure smooth and efficient operation of the vehicle power drive system. The electrical motor can optionally be a permanent magnet motor providing additional torque during the aforesaid first accelerating mode and more regenerative power in the aforesaid second deceleration mode.

0032The VMCS preferably monitors accelerator pedal position, engine throttle position, battery voltage, vehicle speed, and/or torque request to determine the amount and frequency of power being applied to the PTO for maintaining vehicle drivability and optimize overall efficiency.

0033The hybrid system preferably includes a high voltage DC connection center between the energy storage system and an inverter for the electric motor to control electric power flow between the energy storage system, such as, for example, a battery system, and the electric motor.

0034The VMCS preferably has a third park/neutral mode in which the electric motor recharges the battery pack. Additionally, the VMCS preferably has a fourth, all-electric stationary mode with the engine shut down, in which the electric motor operates the auxiliary power take off.

0035In general, the vehicle power drive system of the present includes an internal combustion engine connected through a transmission to drive wheels of a vehicle, with the transmission having a power take off (PTO), wherein the drive system is retrofitted by the steps of: <ol id="ol0002" compact="compact"><li>a) connecting a parallel hybrid drive system to the PTO through a bi-directional power flow shaft, wherein the parallel hybrid drive system comprising an electric motor, a energy storage system, and an vehicle monitoring and control system (VMCS); and,</li><li>b) the VMCS controls the parallel hybrid drive system to use the electric motor to supplement drive power to the wheels of the vehicle when the internal combustion engine is driving the wheels and provides regenerative braking when the engine is not delivering power to the wheels whereby the battery in the parallel hybrid drive system is recharged.</li></ol>

0036The retrofitting can also include the step of connecting the PTO to a torque converter in the transmission, as well as the step of recharging the energy storage system using an outside electric power source. The retrofitting can also include the step of withdrawing auxiliary power from the electric motor when the electric motor is recharging the energy storage system, or the step of disengaging the auxiliary power take off when the electric motor is delivering shaft power to the transmission.

0037Preferably, the VMCS uses a dampening function to reduce vibration in the PTO when switching between supplemental drive power and regenerative braking. The VMCS preferably also monitors accelerator pedal position, engine throttle position, battery voltage, vehicle speed, and/or torque request to determine the amount and frequency of power being applied to the PTO for maintaining vehicle drivability and to optimize overall efficiency.

0038The hybrid system can use a high voltage DC connection center between the energy storage system and an inverter for the electric motor, to control electric power flow between the energy storage system and the electric motor, which can also recharge the energy storage system during park or neutral position of the transmission.

0039The VMCS also provides a method for tuning the amount of power provided for launch assist and regenerative braking power applied in the forward and/or reverse direction, wherein further the VMCS has a tuning chart for the setting provided for each gear, the settings including pedal position vs. positive or negative torque applied, battery voltage vs. torque provided, torque provided vs. state of charge (SOC), and driver inputs including system disable.

0040The system also shifts through each gear, and the transmission provides a signal over the vehicle data network to, wherein the VMCS, in order to provide advanced notice of a shift event, and wherein further based upon this information and the pedal position, so that the VMCS can increase or decrease the power provided to the electric motor, allowing for smoother and more efficient shifting, thereby enhancing the vehicle ride and reducing fuel consumption.

0041The VMCS also interfaces with any original equipment manufacturers (OEM) vehicle data system in order to eliminate or reduce regenerative braking based on anti-lock or traction control events.

Brief Description of the Drawings

0042The present invention can best be understood in connection with the accompanying drawings. It is noted that the invention is not limited to the precise embodiments shown in drawings, in which: <ul id="ul0002" list-style="none" compact="compact"><li><figref idref="f0001">Figure 1</figref> is a high level block diagram showing the relationship between the major hardware elements of the invention.</li><li><figref idref="f0002">Figure 2</figref> is a detailed block diagram of the components and subsystems of the entire vehicle system of this invention.</li><li><figref idref="f0003">Figure 3</figref> is a diagram showing only those blocks used during vehicle acceleration along with arrows indicating power flows.</li><li><figref idref="f0004">Figure 4</figref> is a diagram showing only those blocks used during vehicle deceleration including arrows to show power flow directions.</li><li><figref idref="f0005">Figure 5</figref> is a diagram showing the blocks used in the driving mode of "park/neutral" with arrows showing possible power flow paths.</li><li><figref idref="f0006">Figure 6</figref> is a diagram showing the blocks involved in the support of an all-electric stationary mode also indicating power flow directions via arrows.</li><li><figref idref="f0007">Figure 7</figref> is a diagram showing the elements involved in supporting an engine powered stationary mode indicating power flow directions.</li><li><figref idref="f0008">Figure 8</figref> is a diagram showing the blocks and power flows involved in the plug-in charging mode of the PTO Hybrid System of this invention.</li></ul>

Detailed Description of Drawings

0043<figref idref="f0001">Figure 1</figref> is a high level functional illustration of the invention. The illustration shows the interrelation of all the systems the proposed parallel hybrid propulsion system as affixed to a automatic transmission (2) powered by an internal combustion engine (1) in a Class 6, 7 or 8 bus or truck.

0044Elements (1), (2), (3), (7) and (8) are typical components found in a conventional Class 6, 7 or 8 truck or bus. These include the internal combustion engine (1), the transmission (2), a power take-off (PTO) element (3), wherein the transmission (2) communicates with a differential (7) deriving wheels (8). Those skilled in the art understand the operation of these components and how they interact with each other under typical driving conditions.

0045The mechanical portion of the invention is illustrated in the elements including PTO device (3), electric motor (4), power electronics/battery.(5), Vehicle Monitoring and Control System (VMCS) (6) and an auxiliary device (10), such as a compressor. The PTO element (3) is connected to an electric motor (4) with a short driveshaft (9). The shaft (9) can transmit power into or out of the PTO element (3). The electric motor (4) is powered by a power electronics/battery system (5), also a bi-directional system which can provide power to, or accept power from the electric motor (3) which is acted on mechanically via the PTO (3).

0046The Vehicle Monitoring and Control System (VMCS) (6) oversees the operation of the power electronics/battery system (5) by monitoring the inputs described above along with providing output data to the driver and/or other on-board vehicle systems.

0047An optional auxiliary device, (1) such as a compressor (10), can be mounted on the electric motor end shaft. These auxiliary systems can include a variety of rotating machines used to transmit fluids and/or power via the PTO.

Operational Modes:

0048The following diagrams shown in <figref idref="f0002 f0003 f0004 f0005 f0006 f0007 f0008">Figures 2-8</figref> are illustrations of the power flow in each of the operational modes that the PTO Hybrid can be operated within: <ul id="ul0003" list-style="none" compact="compact"><li><figref idref="f0002">Fig. 2</figref> is an Overall system diagram.</li><li><figref idref="f0003">Fig. 3</figref> is a Driving mode during acceleration</li><li><figref idref="f0004">Fig. 4</figref> is a Driving mode during deceleration</li><li><figref idref="f0005">Fig. 5</figref> is a Driving mode during park/neutral</li><li><figref idref="f0006">Fig. 6</figref> is a Stationary mode during an all electric operation</li><li><figref idref="f0007">Fig. 7</figref> is a Stationary mode during engine operation</li><li><figref idref="f0008">Fig. 8</figref> is a Plug in mode during battery charging</li></ul>

0049The Diagrams of <figref idref="f0003 f0004 f0005 f0006 f0007 f0008">Figures 3-8</figref> illustrate the flow of mechanical energy, electrical energy, controls power and control logic within each of the operational modes.

0050<figref idref="f0002">Figure 2</figref> shows all of the major subsystems and elements used in PTO hybrid system of this invention. Most of the blocks shown are self-explanatory, however some may need elaboration. Note the "battery isolator/combiner" (15) on the left center; this controls connections between the vehicle battery (16) and a separate 12V battery (17) of the present invention which operates control systems as well as a "Heating System" (18). The central block, "High Voltage DC Connection Center"(19) has 3 connections; to the inverters (20) which convert DC from the battery packs to AC to operate the PM motor, and to the DC to DC converter (21) which steps the 600VDC down to 12V for typical vehicle loads including connections to both 300V battery packs, SES1 (25) and SES2 (26) with their own local management systems and chargers. The AC charge port (30) on the right connects through charge port interface (31) (CPI) to both battery chargers. Note that the "Electric Motor" (4) which is used through the "PTO clutch" (3) for both acceleration and regenerative braking also powers a "Hydraulic Pump" (35) for bucket hydraulics. Auxiliary power unit controller (37) ("APUC") and driver interface node (38) (DIN) provide the power requirement to the Motor/Drive inverter motor based on the accelerator pedal position and the power required during stationary mode operation respectively, with the "Motor Drive/Inverter" (20) which in turn provides electrical energy to the electric motor (4).

0051In <figref idref="f0003">Figure 3</figref>, during the acceleration mode, power flows from both 300V battery packs, through the high voltage DC connection center (19), and the motor drive/inverter (20) to the electric motor (4) which drives the wheels (8) through its PTO entry point blending its power with that from engine (1). This launch assist is controlled by demand as well as the charge status of battery packs SES1 (25) and SES2 (26); it recycles energy gathered during braking to reduce fuel consumption and pollution.

0052In contrast, in <figref idref="f0004">Figure 4</figref> during the deceleration mode, mechanical power flows from the differential (7) and gear box through the PTO (3), spinning the electric motor (4) as a generator to charge up both 300V battery packs through the motor drive/inverter (20) and the high voltage connection center (19). Thus energy which would have been wasted as heat in the brakes is recovered for later use.

0053<figref idref="f0005">Figure 5</figref> shows a typical operation while the vehicle is in "Park/Neutral" with the engine (1) running whereby engine power can be used to spin the electric motor (4) through the PTO (3) as a generator to top up both 300V battery packs and /or power the auxiliary drive. Note that in this mode the hydraulic pump (35) is disengaged from the electric motor (4).

0054<figref idref="f0006">Figure 6</figref> shows activity which can be supported by the PTO hybrid system of this invention while the vehicle is parked with the engine (1) off. In this mode, no site pollution or emissions are generated, and engine noise is absent. All power is provided from the two 300V battery packs. This all-electric mode can power bucket hydraulics, auxiliaries, and charging of vehicle 12V battery (16) as well as a 12V battery of the present invention through a DC/DC converter (21). The bold power arrows show the flow paths.

0055<figref idref="f0007">Figure 7</figref> shows the power flow for the engine-driven counterpart stationary mode. In this mode all power is derived from the engine (1), and the 300V battery packs can be recharged via engine power. This mode could be used briefly until the 300V batteries are charged if they had been depleted at a work site in all-electric mode. However, this mode can also supply bucket hydraulics since the motor (4), while spun by the engine (1) as a generator to charge the 300 V battery packs, is also shaft-connected to the hydraulic pump (35).

0056<figref idref="f0008">Figure 8</figref> is a diagram showing the connections for plug-in charging at a charging station. 12V battery chargers not part of the vehicle system are used to charge the two 12V batteries, while the chargers built into 300V packs SES1 (25) and SES2 (26) are used to charge those high voltage packs.

0057In the foregoing description, certain terms and visual depictions are used to illustrate the preferred embodiment. However, no unnecessary limitations are to be construed by the terms used or illustrations depicted, beyond what is shown in the prior art, since the terms and illustrations are exemplary only, and are not meant to limit the scope of the present invention.

0058It is further known that other modifications may be made to the present invention, without departing the scope of the invention, as noted in the appended Claims.