Patent Application
20100056326
The increasing demand to improve fuel economy, eliminate emissions, and reduce noise levels has driven the automotive market to develop a variety of propulsion mechanisms. As an alternative to the traditional internal combustion engine (ICE) powertrain the industry has developed a hybrid electric system powered by an electric traction motor(s) and an internal combustion engine. During varying driving conditions, hybrid electric vehicles (HEVs) will alternate between the separate power sources, depending on the most efficient manner of operation of each source.
While this provides for a more efficient operation and reduces carbon emissions, it is not without its problems. For example, power steering systems have become standard equipment on all large Class 8 over the highway trucks or tractors. These systems, as well as others, utilize power generated by the internal combustion engine in order to operate. For example, power steering pumps for steering systems or air compressors for braking systems, etc, are driven by the internal combustion engine.
In order to allow the HEV to shut-off the engine to improve fuel efficiency, reduce emissions, etc., a system not heretofore developed is needed to maintain the functionality of these systems and others. Embodiments of the present invention are directed to such systems.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
In accordance with aspects of the present invention, a system is provided for use in a hybrid electric vehicle that includes at least one fuel powered engine having an engine-on condition and an engine-off condition. The system comprises an accumulator for storing hydraulic fluid under pressure, a hydraulic motor, and a fluid pump adapted to be driven by a fuel powered engine. The fluid pump is capable of supplying hydraulic fluid to the hydraulic motor and to the accumulator during an engine-on condition of the fuel powered engine. The system further comprises a controlling component for monitoring the pressure of the accumulator, wherein the controlling component generates a control signal that prohibits the fuel powered engine from transitioning from its engine-on condition to its engine-off condition if the pressure within the accumulator is below a threshold value.
In accordance with another aspect of the present invention, a hybrid vehicle is provided. The hybrid vehicle comprises a fuel powered engine having an engine-on condition and an engine-off condition, a motor, a first controlling component for controlling the operation of the fuel powered engine and the motor, an accumulator for storing power steering fluid under pressure, a sensor associated with the accumulator for generating signals indicative of the fluid pressure of the accumulator, a power steering gear having a hydraulic motor, and a power steering pump driven by the fuel powered engine in the engine-on condition. The power steering pump is capable of supplying power steering fluid to the power steering gear and to the accumulator during an engine-on condition of the fuel powered engine. The hybrid vehicle further includes a second controlling component that monitors the signals generated by the sensor and generates a control signal that instructs the first controlling component to maintain operation of the fuel powered engine in its engine-on condition when the pressure within the accumulator is below a threshold value.
In accordance with yet another aspect of the present invention, a method of maintaining power steering functionality is employed in a hybrid vehicle having a fuel powered engine having an engine-on condition and an engine-off condition, a motor, and a first controller for controlling the operation of the fuel powered engine and the motor. The method of maintaining the power steering functionality of the vehicle comprises the steps of: providing an accumulator that receives pressurized fluid from a fluid pump when the internal combustion engine in the engine-on condition, and transmits pressurized fluid to a steering gear in the engine-off condition; monitoring the pressure of the accumulator during engine-on and engine-off conditions; and prohibiting the vehicle from transitioning from the engine-on condition to the engine-off condition when the pressure within the accumulator is below a threshold value.
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
Embodiments of the present invention will now be described with reference to the drawings where like numerals correspond to like elements. Embodiments of the present invention are generally directed to steering systems suitable for use in vehicles, such as Class 8 trucks. More particularly, embodiments of the present invention are directed to steering systems suitable for use with vehicles of the hybrid type (e.g., gas-electric, diesel-electric, gas-hydraulic, diesel-hydraulic, etc.) that maintain power steering functionality during “engine off” conditions.
Although exemplary embodiments of the present invention will be described hereinafter with reference to a hybrid powered heavy duty truck, it will be appreciated that aspects of the present invention have wide application, and therefore, may be suitable for use with many other types of vehicles, including but not limited to light & medium duty vehicles, passenger vehicles, motor homes, buses, commercial vehicles, marine vessels, et, that are hybrid powered. Accordingly, the following descriptions and illustrations herein should be considered illustrative in nature, and thus, not limiting the scope of the present invention, as claimed.
Prior to discussing the details of various aspects of the present invention, it should be understood that the following description includes sections that are presented largely in terms of logic and operations that may be performed by conventional electronic components. These electronic components, which may be grouped in a single location or distributed over a wide area, can generally include processors, memory, storage devices, input/output circuitry, etc. It will be appreciated by one skilled in the art that the logic described herein may be implemented in a variety of configurations, including but not limited to, analog circuitry, digital circuitry, processing units, etc., and combinations thereof. In circumstances were the components are distributed, the components are accessible to each other via communication links.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of exemplary embodiments of the present invention. It will be apparent to one skilled in the art, however, that many embodiments of the present invention may be practiced without some or all of the specific details. In some instances, well-known process steps have not been described in detail in order not to unnecessarily obscure various aspects of the present invention.
As briefly described above, embodiments of the present invention are directed to steering systems suitable for use in a vehicle. One suitable vehicle in which the steering systems may be employed will now be described in more detail with reference to
One of ordinary skill in the art will appreciate that the hybrid powertrain 22 and associated subsystems/components may include many more components than those depicted in
In the embodiment shown in
Still referring to
One or more clutch assemblies 44 may be positioned between the internal combustion engine 26 and electric motor generator 28 and the power transfer unit 30 and/or the transmission 32 to selectively engage/disengage the internal combustion engine 26 and/or the electric motor generator 28 from the power transfer unit 30 and/or the transmission 32. The one or more clutch assemblies 44 may be part of the power transfer unit 30 or may be discrete therefrom. In one embodiment, the power transfer unit 30 may include a planetary gear set conventionally arranged for carrying out the functions 1-4 described above. Of course, other types of power transfer units, including other gear sets and transmissions, may be employed. In another embodiment, the power transfer unit 30 and the transmission 32 may be arranged as a unitary device that provides both the functions of the power transfer unit 30 and that of the transmission 32. One type of unitary device that may be employed by the powertrain 22 is known in the art as a power split device.
The vehicle 20 also includes at least two axles such as a steer axle 50 and at least one drive axle, such as axles 52 and 54. The output shaft 42 of the transmission 32, which may include a vehicle drive shaft 46, is drivingly coupled to the drive axles 52 and 54 for transmitting the output torque generated by the internal combustion engine 26 and/or the electric motor generator 28 to the drive axles 52 and 54. The steer axle 50 supports corresponding front wheels 66 and the drive axles 52 and 54 support corresponding rear wheels 68, each of the wheels having service brake components 70. The service brake components 70 may include wheel speed sensors (not shown), electronically controlled pressure valves, and the like, to effect control of the vehicle braking system.
The vehicle 20 may also include conventional operator control inputs, such as a clutch pedal 72 (in some manual systems), an ignition or start switch 74, an accelerator pedal 76, a service brake pedal 78, a parking brake 80, and a steering wheel 82 to effect turning of the front wheels 66 of the vehicle 20. The vehicle 20 may further include a cab mounted operator interface, such as a control console 84, which may include any of a number of output devices 88, such as lights, graphical displays, speakers, gages, and the like, and various input devices 90, such as toggle switches, push button switches, potentiometers, or the like. To provide power to the control console 84, a DC/DC converter 96 is connected to the high voltage bus 40. The DC/DC converter 96 reduces the voltage it receives, and outputs power at this lower voltage to the control console 84. The D/C to D/C converter 96 can output power to other low voltage electrical devices on the vehicle 20. The DC/DC converter 96 may also condition the power prior to directing it to the low voltage electrical devices.
To control the various aspects of the hybrid powertrain 22, a powertrain controller 100 is provided. As shown in
In one embodiment, the powertrain controller 100 may control the operation of one or more of the following devices: the internal combustion engine 26; the electric motor generator 28; the power transfer unit 30; the transmission 32; the energy storage device 38, optional clutch assemblies 44, etc. In one embodiment, the powertrain controller 100 may include a programmable digital computer, microprocessor or the like that is configured to receive various input signals, including without limitation, the operating speeds of internal combustion engine 26 via sensor 102 and the electric motor generator 28 via sensor 104, transmission input speed via sensor 106, selected transmission ratio, transmission output speed via sensor 108 and vehicle speed via wheel speed sensors (not shown), throttle position via sensor 110, and state of charge (SOC) of the energy storage device 38. The powertrain controller 100 processes these signals and others accordingly to logic rules to control the operation of the hybrid powertrain 22. For example, to start or restart the internal combustion engine 26, the powertrain controller 100 may be programmed to signal delivery of fuel to the internal combustion engine 26 and to signal the operation of the electrical motor generator 28 or optional starter to start the engine. It will be appreciated that the powertrain 100 may receive these input signals directly from the associated sensor(s), devices, etc., or may receive the input signals from other vehicle subsystems, as will be described in more detail below.
To support this control, various devices (e.g., the internal combustion engine 26, the electric motor generator 28, etc.) controlled by the powertrain controller 100 may include their own controllers, which communicate with the powertrain controller 100 through a vehicle-wide network, also referred to as a controller area network (CAN) 112, as shown in
For example, an engine controller 114 may communicate with the powertrain controller 100 and may function to monitor and control various aspects of the operation of the internal combustion engine 26, including ignition timing (on some vehicles), fuel delivery, variable valve timing (if equipped) and the like. To that end, the engine controller 114 typically receives signals from a variety of sensors, including but not limited to the wheel speed sensors (not shown) of the brake components 70, the engine speed sensor 102, the accelerator pedal position sensor 110, etc., either directly or by other system or device controllers (i.e., the transmission controller 116, power transfer unit controller 118, the powertrain controller 100, etc.), processes such signals and others, and transmits a variety of control signals to devices including but not limited to fuel control devices 122 for selectively supplying fuel to the internal combustion engine 26, an engine retarder 124 such as a jake brake, etc. As will be described in more detail below, the engine controller 114 may transmit signals indicative of vehicle operational data (e.g., engine speed, throttle position, etc.) to the powertrain controller 100 or other system controllers via the CAN 112 and may receive control signals from the powertrain controller 100 or from controllers of other vehicle subsystems either directly or via CAN 112 to effect the operation of the internal combustion engine 26.
Similarly, the electric motor generator 28 may include one or more controllers 126 that sends and receives signals to and from the powertrain controller 100 and the electric motor generator 28 for controlling the direction of power flow to/from the electrical motor generator 28. The vehicle may include other controllers, such as an energy storage device controller 120, communicatively connected to the CAN 112.
As used herein, controllers, control units, control modules, program modules, etc., can contain logic for carrying out general or specific operational features of the vehicle 20. The logic can be implemented in hardware components, such as analog circuitry, digital circuitry, processing units, or combinations thereof, or software components having instructions which can be processed by the processing units, etc. Therefore, as used herein, the term “controlling component” can be used to generally described these aforementioned components, and can be either hardware or software, or combinations thereof, that implement logic for carrying out various aspects of the present invention.
Referring now to
When it is desired to start the hybrid vehicle 20 from rest (i.e., parked), the ignition switch 74 is moved to the start position. Next, the vehicle operator chooses the appropriate gear, releases the parking brake 80, if set, lifts their foot off of the service brake pedal 78, and applies pressure on the accelerator pedal 76. At this time, the powertrain controller 100 monitors various hybrid powertrain operating parameters, for example, the SOC of the energy storage device 38 and the load state of the vehicle 20, and depending on the SOC of the energy storage device 38 and the load state of the vehicle (typically calculated by accelerator pedal position and/or vehicle speed), the powertrain controller 100 controls the operation of the electric motor generator 28 only (“electric launch mode”), the internal combustion engine only, or combines the output of both via the power transfer unit 30 (“blended torque mode”) to provide motive force to the vehicle 20.
For example, if the powertrain controller 100 determines that the SOC of the energy storage device 38 is at a sufficient level with respect to the vehicle load state, the powertrain controller 100 operates the powertrain 22 in the electric launch mode. For example, in a low load state and/or a low vehicle speed, and a high SOC, the powertrain controller 100 operates solely in the electric launch mode. In the electric launch mode, the internal combustion engine is off (engine-off condition), and the powertrain controller 100 signals delivery of electrical energy from the energy storage device 38 to power the electrical motor generator 28. Upon receipt of electrical power from the energy storage device 38, the electric motor generator 28 acts as a motor to generate output torque for propelling the vehicle 20.
On the other hand, if the powertrain controller 100 determines that the SOC of the energy storage device 38 is low with respect to the calculated vehicle load state, the powertrain controller 100 operates the powertrain 22 either in the hybrid assist mode, also known as the “blended torque mode,” or the engine only mode. In the blended torque mode, the power controller 100 signals delivery of electrical energy from the energy storage device 38 to power the electrical motor generator 28 and fuel delivery to the internal combustion engine 26 so as to be started by the electric motor generator 28, and then signals the internal combustion engine 26 and the energy storage device/electric motor generator to generate output torque, which is “blended” or combined by the power transfer unit 30 according to control signals from the powertrain controller 100. For example, in a medium load state where the powertrain controller 100 determines that improved fuel efficiency may be realized by operating in the blended torque mode, or if additional torque in needed from the electric motor generator 28 during, for example, rapid acceleration situations, the internal combustion engine 26, along with the electric motor generator 28 is operated by the powertrain controller 100 so that the generated output torque is combined by the power transfer unit 30 and sent to the drive axles 52 and 54 through the transmission 32.
It should also be appreciated that the vehicle 20 may start out in electric launch mode, but based on continuously monitored operating conditions of the powertrain, e.g., SOC and vehicle load, the powertrain controller 100 may determine that the internal combustion engine 26 is needed to meet the output demands of the vehicle 20. In this case, the powertrain controller 100 signals for the internal combustion engine 26 to be started by the electric motor generator 28 or a separate starter motor, and signals the appropriate components, e.g., power transfer unit 30, clutch assemblies 44, etc. to combine the output torque of the internal combustion engine 26 and the electric motor generator 28 for propelling the vehicle 20.
When the hybrid vehicle 20 is cruising (i.e. not accelerating), and the internal combustion engine 26 can meet the vehicle load demand, the powertrain controller 100 controls the operation of the internal combustion engine 26, the electric motor generator 28, and the power transfer unit 28 based on the SOC of the energy storage device 38. If the energy storage device SOC is low, the powertrain controller 100 operates the power transfer unit 30 to split the power from the internal combustion engine 26 between the drive axles 52, 54 and the electric motor generator 28 so that the electric motor generator 28 acts as a generator and charges the energy storage device 38. This is called the “energy storage device charging mode.” If the SOC of the energy storage device 38 is high, the powertrain controller 100 may operate the internal combustion engine 26 solely to propel the vehicle, or may operate the power transfer unit 32 and the electric motor generator 28 in the blended torque mode, as described above.
At any time the powertrain controller 100 determines during vehicle operation that the SOC of the energy storage device 38 becomes equal to or lower than a threshold level, the internal combustion engine 26 is immediately driven, and the output torque of the internal combustion engine 26 is transmitted to the electrical motor generator 28 through the power transfer device 30. In this case, the electrical motor generator 28 is operated as a power generator to charge the energy storage device 38. This may occur during vehicle transport or idling situations as well.
The energy storage device 38 may also be charged during vehicle movement via the regenerative braking mode. That is, instead of using the brakes to slow or stop the vehicle 20, the electric motor generator 28 is used to slow the vehicle 20. At the same time, the energy from the rotating rear wheels 68 is transferred to the electric motor generator 28 via the transmission 32 and power transfer unit 30 (the internal combustion engine 26 is either in the engine-off mode or is decoupled from the power transfer unit 30 by the clutch assembly 44), which in turn, causes the electric motor generator 28 to act as a generator to charge the energy storage device 38.
Referring now to
As best shown in
In one embodiment, the steering gear 144 includes a recirculating ball assembly 154 for effecting rotation of the output shaft 150. The recirculating ball assembly 154 is comprised of an actuating shaft 156, a recirculating ball bearing block 158, and a plurality of ball bearings 160. The recirculating ball bearing block 158 is freely movably over the actuating shaft 156, where rotation of the actuating shaft 156 causes the recirculating ball bearing block 158 to move along the actuating shaft 156 in a direction dependent on rotational direction of the actuating shaft 156. The recirculating ball bearing block 158 is formed with a toothed rack 162 on one side, which engages a section gear 164 fixed for rotation with the output shaft 150. In this embodiment, the output shaft 150 is configured for connection to the pitman arm 152 in a conventional manner.
In accordance with aspects of the present invention, the steering system 140 of
To control the hydraulic motor 172 upon rotation of the steering wheel 82 by the vehicle operator, a control valve 180 is provided. The control valve 180 is configured to receive pressurized fluid from the power steering pump 160 via supply line 168, and to supply pressurized hydraulic fluid to either the first or second chambers from supply/return lines 184 and 186, respectively, depending on the direction of steering wheel rotation. The control valve 180 is further configured to return fluid from the other of the first or second chambers 172 or 174 (via the other of the supply/return lines 184 and 186) to the reservoir 166 via return line 170. In one embodiment, the control valve 180 may be electrically controlled based on output generated by a steering sensor 188 (See
While a steering gear of the recirculating ball-type has been shown in one embodiment of the present invention, it will be appreciated that the steering system 140 may use any conventional or future developed powered steering gears, including a powered steering gear of the rack and pinion type. It will be appreciated that different steer axles, steering components, etc., may be required for such steering gears, which can be configured by those skilled in the art.
Thus, when the internal combustion engine 26 is generating output torque, also known as the “engine-on condition”, the power steering pump 160 is driven by an engine driven belt or chain, thereby supplying fluid from the reservoir 166 to the steering gear 144. On the other hand, when the internal combustion engine 26 is not generating torque, also known as the “engine-off condition,” the steering pump 160 is not driven, and as a result, pressurized fluid is not supplied to the steering gear 144.
To address this deficiency, especially in a hybrid vehicle, the steering system 140 also provides power steering functionality to the steering gear 144 during the engine-off condition. To that end, the steering system 140 further includes an accumulator 200, a power steering controller 202, a distribution valve assembly 204, and a pressure sensor 206 that generates output signals indicative of the pressure level or pressure change in the accumulator 200. Due to safety concerns associated with the potential for the vehicle 20 to cease having power steering functionality during engine-off conditions, embodiments of the steering system 140 continuously monitor the pressure of the accumulator 200 via the pressure sensor 206. In several embodiment, the steering system 140 keeps track of whether the accumulator pressure exceeds a first threshold level or engine shut-down prohibition level and/or a second threshold level or engine restart level. From these signals, as will be described in more detail below, the powertrain controller 100 can instruct the internal combustion engine 26 to restart from its engine-off condition and/or prohibit the internal combustion engine 26 operating in its engine-on condition to transition to its engine-off condition.
Still referring to
In one embodiment, the distribution valve assembly 204 comprises one or more solenoid controlled or other electronically controlled valves that are selectively operated to provide the following fluid delivery paths: 1) pressurized fluid generated by the power steering pump 160 during engine-on vehicle operation is supplied to the steering gear 144 and the accumulator 200 for storage; 2) pressurized fluid from the accumulator 200 is supplied to the steering gear 144 during engine-off vehicle operation. In other embodiments, the distribution valve assembly 204 may include mechanically actuated (spring or the like) valves configured and arranged to provide the functionality described above. In another embodiment, the distribution valve assembly 204 may include a pressure relief valve that can exhaust excess pressurized fluid to the reservoir 162 via return line 218.
Referring to
It will be appreciated that the sensor 206 may output its signals directly to the power steering controller 202, or may communicate with the power steering controller 202 via the CAN 112. It will be also appreciated that the power steering controller 202 may communicate with other electronic components of the vehicle 20 via the CAN 112 for collecting data from other electronic components to be utilized by the power steering controller 202. In one embodiment the engine controller 114 may monitor the speed of the internal combustion engine 26 of the vehicle via engine, wheel and/or transmission sensors, including the engine output speed sensor 102, and communicate such speeds to the power steering controller 202 via the CAN 112 so that the power steering controller 202 may adjust the operation of the distribution valve assembly 204 in relation to vehicle and/or engine speed. For example, at high engine speeds, the distribution valve assembly 204 can be operated to divert excess pressure from supply line segment 168A via exhaust line 218, if desired.
In several embodiments, the power steering controller 202, and any one of the various sensors, switches, actuators, etc., of the steering system 140 may contain logic rules implemented in a variety of combinations of hardware circuitry components and programmed microprocessors to effect control of the various vehicle systems and subsystems described herein. To that end, as further illustrated in
Referring now to
The power steering controller 202 continues to monitor the pressure sensor 206. If the pressure reading from the pressure sensor 206 is somehow below the engine shut-off prohibition level, the power steering controller 202 generates signals and transmits such signals via the CAN 112 to the powertrain controller 100. The signals, when received by the powertrain controller 100, prohibit the powertrain controller 100 from transitioning the vehicle from the engine-on condition to the engine-off condition. For example, as the vehicle 20 continues to operate in the engine-on condition, if a determination is made by the powertrain controller 100 that the vehicle 20 can save fuel by switching the operation of the internal combustion engine 26 from the engine-on to the engine-off condition (e.g., low speed, low vehicle load), the signals transmitted by the power steering controller 202 to the powertrain controller 100 indicating a pressure below the engine shut-off prohibition level prohibit the powertrain controller 100 from transitioning the vehicle 20 from the engine-on to the engine-off condition.
On the other hand, the vehicle 20 could be operating with the internal combustion engine 26 not developing output torque (i.e., engine-off condition). This may occur when the vehicle 20 is at rest, for example, at a stop light or the like, or could be operating at relatively low vehicle speeds or vehicles loads in which the electric motor generator 28 is providing the motive power for the vehicle (e.g., electric launch mode). In this condition, if the accumulator 200 contains fluid below a predetermined pressure level (hereinafter “restart engine level”) as determined by pressure signals from the sensor 206 and processed by the power steering controller 202, the power steering controller 202 generates signals to be transmitted to the powertrain controller 100 in order for the powertrain controller 100 to signal an engine restart. As described above, this may include signaling the fuel delivery devices to deliver fuel to the internal combustion engine 26 and signaling the electric motor generator 28 or alternative starter to start the internal combustion engine 26, thereby transitioning the internal combustion engine 26 from the engine-off condition to the engine-on condition. In this way, delivery of pressured fluid to the steering gear 144 can be maintained, via operation of the power steering pump 160. The accumulator 200 can also be charged at this time, depending on vehicle speed, etc.
If the accumulator 200 contains fluid above the restart engine level as determined by pressure signals processed by the power steering controller 202, the distribution valve assembly 204 supplies pressurized fluid to the steering gear 144 so that the steering system 140 may continue to operate as normal (i.e., as it would operate with pressurized fluid being delivered by the power steering pump). In this engine-off condition, the accumulator 200 continues to supply pressurized fluid to the steering gear 144 for a set period of time based on accumulator capacity. It will be appreciated that the capacity of the accumulator 200 may be chosen based on the specific vehicle and intended application. At the same time, the power steering controller 202 continues to monitor the pressure signals from the sensor 206. If the power steering controller 206 determines that the pressure of the accumulator 200 has dropped below the restart engine level, the power steering controller 202 generates and transmits the appropriate restart signals to the powertrain controller 100, as described above.
As shown in
The principles, representative embodiments, and modes of operation of the present invention have been described in the foregoing description. However, aspects of the present invention which are intended to be protected are not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. It will be appreciated that variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes, and equivalents fall within the spirit and scope of the present invention, as claimed.
