Abstract:
A power supply for powering a hydraulic implement includes: an electric storage unit; an electric motor, an electric generator, a hydraulic pump and a control unit; the electric motor adapted for receiving electric power and driving the hydraulic pump to power the hydraulic implement; the electric generator adapted for translating mechanical energy into the electric power; the electric storage unit also being adapted for providing the electric power; and the control unit for selecting a source of the electric power from one of the generator and the electric storage unit. A method for operating the power supply and a vehicle are also provided.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to hydraulic drives, and particularly to a hydraulic drive that is driven by a hybrid power supply. 
     2. Description of the Related Art 
     Many work vehicles make use of hydraulic systems. For example, consider a traditional utility truck used for servicing residential telephone, electric and cable supplies. Such vehicles with hydraulic systems on-board are virtually ubiquitous in industry. The hydraulic systems provide users with a number of advantages, such as rapid deployment, convenience of use, as well as a robust power supply for tooling (such as hydraulically driven drills). However, such hydraulic systems are not without disadvantages. 
     Consider that many tasks facilitated by operation of hydraulic systems involve work of a prolonged duration. Accordingly, power supplies on-board the work vehicle are often inadequate to drive the hydraulic system for the duration of the work. One solution is to idle the work vehicle and make use of mechanical output from an engine of the work vehicle. Unfortunately, this is not economic in terms of fuel consumption or vehicle wear. Further, this is of increasing concern to regulatory agencies. More specifically, as the Environmental Protection Agency has pronounced that it does not have the power to enact a nationwide anti-idle law, many states, counties and municipalities have enacted their own rules regarding idling of work vehicles. Given the great variety of these rules, operators of work vehicles are challenged to rely upon traditional methods for powering hydraulic systems on-board work vehicles. 
     One example of an effort to address the need is provided in U.S. Pat. No. 7,104,920, entitled “Hybrid vehicle powertrain system with power take-off driven vehicle accessory” discloses a hybrid vehicle powertrain system that includes a first prime mover, a first prime mover driven power transmission mechanism having a power take-off adapted to drive a vehicle accessory, and a second prime mover. The second prime mover is operable to drive the power transmission mechanism alone or in combination with the first prime mover to provide power to the power take-off through the power transmission mechanism. The patent further discloses methods for operating a hybrid vehicle powertrain system. Unfortunately, the technology provided in this example has certain drawbacks. By way of example, having a powertrain system that includes the second prime mover, such as an electric or hydraulic motor, may cause excess wear and inefficient operation, among other things. 
     Accordingly, what are needed are techniques for powering hydraulic systems used in work vehicles. Preferably, the techniques minimize vehicle wear, fuel consumption and are compliant with ant-idle rules and regulations. 
     SUMMARY OF THE INVENTION 
     The shortcomings of the prior art are overcome and additional advantages are provided through the provision of a power supply for powering a hydraulic implement, the power supply including: an electric storage unit; an electric motor, an electric generator, a hydraulic pump and a control unit; the electric motor adapted for receiving electric power and driving the hydraulic pump to power the hydraulic implement; the electric generator adapted for translating mechanical energy from a power take off into the electric power; the electric storage unit also being adapted for providing the electric power; and the control unit configured for selecting a source of the electric power from one of the generator and the electric storage unit. 
     A method for powering a hydraulic implement, the method including: driving a hydraulic pump with an electric motor, the electric motor powered by electric power from an electric storage unit; upon depletion of the electric storage unit, starting an engine to drive a power take off unit; driving a generator with the power take off unit; and charging the electric storage unit and powering the electric motor from the generator. 
     A vehicle including at least one hydraulic system for powering a hydraulic implement, the vehicle including: a hybrid power supply for powering the hydraulic system, the hybrid power supply including an electric storage unit; an electric motor, an electric generator, a hydraulic pump and a control unit; the electric motor adapted for receiving electric power and driving the hydraulic pump to power the hydraulic implement; the electric generator adapted for translating mechanical energy from a power take off of the vehicle into the electric power; the electric storage unit also being adapted for providing the electric power; and the control unit for selecting a source of the electric power from one of the generator and the electric storage unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  depicts aspects of a vehicle implementing a hydraulic system; 
         FIG. 2  illustrates aspects of a hybrid power supply for driving the hydraulic system of  FIG. 1 ; and 
         FIG. 3  is a flow chart depicting exemplary logic for operation of the hybrid power supply of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The teachings herein provide a hybrid power supply for driving a hydraulic system. In the examples provided herein, the hydraulic system is implemented on a work vehicle, such as a utility truck to power a hydraulic implement. Advantageously, the hybrid power supply may be added to an existing vehicle as a retrofit, and therefore need not be integrated into a vehicle, such as at the time of manufacture. One skilled in the art will recognize that the embodiments provided are merely illustrative and are not limiting of the invention.  FIGS. 1 and 2  provide an illustrative embodiment of the hybrid power supply. 
     Turning now to  FIG. 1  there is shown an embodiment of a vehicle  10 . The vehicle  10  includes a hydraulic implement  1 . In this example, the hydraulic implement  1  is a bucket lift which provides mobility to a user. 
     In this embodiment, the vehicle  10  includes an engine  2 , a transmission  3  and a drive shaft  4 . The engine  2 , transmission  3  and drive shaft  4  cooperate as a drive train to provide energy to a hybrid power supply  20 . In this embodiment, the energy supplied is rotational energy provided by a power take off, as shown in  FIG. 2 . 
     Referring now to  FIG. 2 , an embodiment of the hybrid power supply  20  includes a motor/generator  12 , a hydraulic pump  16 , a control unit  15  and an electric storage  18 . The motor/generator  12  at least one of drives the hydraulic pump  16  and charges the electric storage  18 . The hydraulic pump  16  provides pressurized hydraulic fluid to the hydraulic implement  1  for performing work. Generally, the hydraulic pump  16  is driven by the motor/generator  12 , however, the hybrid power supply  20  may further include apparatus for driving the hydraulic pump  16  directly from the power take off  11 . The control unit  15  generally governs operation and interface with the hybrid power supply  20 . 
     In general, the motor/generator  12  is unitary and performs a dual role. That is, the motor/generator  12  can be a dual purpose unit which provides rotational energy to the hydraulic pump  16  or electrical energy for charging the electric storage  18 . Alternatively, at least one dedicated motor and at least one dedicated generator may be used in the hybrid power supply  20  in place of (or to augment) the motor/generator  12 . As an example, in one configuration, the motor/generator  12  receives electric power from the electric storage  18  and provides rotational force to at least one hydraulic pump  16 . In another configuration, the motor/generator  12  receives rotational force from the power take off  11 , and generates electric power for charging the electric storage  18 . Of course, other arrangements for powering the hybrid power supply  20  may be realized. For example, in another embodiment, a separate generator is included with the engine  2  and driven from a crankshaft of the engine  2  by a main belt or an additional belt (not shown). 
     Included with the hybrid power supply  20  are the electric storage  18  and the control unit  15 . In some embodiments, the electric storage  18  includes at least one battery and may include a plurality of batteries. In other embodiments, or in embodiments that are in addition to those with at least one battery, the electric storage  18  includes at least one fuel cell. In short, any resource capable of providing adequate electric supply and storage may be used as the electric storage  18 . 
     The control unit  15  generally governs operation of and interface with the hybrid power supply  20 . For example, the control unit  15  may be adapted for monitoring output of the electric storage  18 , initiating charging of the electric storage  18 , activating and deactivating the motor/generator  12 , receiving user commands, starting and stopping of the engine  2 , execution of software and other such functions. Having thus described components of the hybrid power supply  20 , certain aspects are now discussed in greater detail. 
     In operation, the hybrid power supply  20  powers the hydraulic pump  16  by using electrical energy from the electric storage  18  (i.e., while the engine  2  is off), by converting mechanical energy from the power take off into electrical energy, or by direct coupling of the hydraulic pump  16  to the power take off  11 . By coupling the motor/generator  12  to the power take off  11 , the motor/generator  12  provides for powering the hydraulic pump  16  as well as charging of the electric storage  18  while the engine  2  is on. 
     When the vehicle  10  is appropriately configured (such as by configuring safety interlock devices, for example, by placing the vehicle  10  into park or neutral), and the hybrid power supply  20  is activated, the control unit  15  may provide for monitoring output of the electric storage  18  and starting the engine  2  as necessary. That is, the control unit  15  effectively governs and switches between power supplies for the hydraulic pump  16 . More specifically, the control unit  15  will automatically switch between electric power generated by mechanical power from the power take off  11  (i.e., electric power from the generator) and the electric power from the electric storage  18 , and vice-versa. During recharging of the electric storage  18 , the hydraulic pump  16  will generally continue to operate without interruptions in service. 
     As one might surmise, a portion of the mechanical power provided by the power take off  11  will be used to charge the electric storage  18 , while another portion will drive the hydraulic pump  16 . Accordingly, the control unit  15  may be configured in a variety of ways for multiplexing. One embodiment of multiplexing is by having the motor/generator  12  default to charge state (as a generator), with priority given to hydraulic demand (operation as a motor, when needed, to drive the hydraulic pump  16 ). Another embodiment of multiplexing calls for multiplexing as a function of time, where switching functions of the motor/generator  12  occurs in various (generally rapid) intervals. 
     During travel of the vehicle  10 , the hybrid power supply  20  will generally recharge the electric storage  18 . That is, power from the power take off  11  may be continuously converted to electrical energy for charging the electric storage  18 . In some embodiments, such as where the motor/generator  12  is large enough, the motor/generator  12  may be used to provide power assistance or braking to the transmission  3  (or other portion of a drive train for the vehicle  10 ) by backdriving through the power take off  11 . 
     During periods of non-use (e.g., when the vehicle  10  is out of service), the hybrid power supply  20  can be coupled to external power  21 . Coupling to external power provides for economic charging of the electric storage  18  (such as at night, when electric power is purchased at off peak rates). 
     In some embodiments, a separate motor and charging unit are included in the hybrid power supply  20 . In these embodiments, a generator may be driven by the engine  2 , a belt, or from the power take off  11 , while an electric motor and hydraulic pump are remotely mounted. In further embodiments, a separate electric generator  22  (e.g., a liquid fuel generator such as gasoline, diesel or other or a fuel cell) is used in place of or in addition to the engine  2 . 
     Accordingly, the control unit  15  may include a variety of components. Exemplary components of the control unit  15  include those that are adapted for monitoring of electric signals, switching of electric signals, detecting position, governing mechanical engaging and disengagement (such as engaging and disengaging the hydraulic pump  16  and the motor/generator  12 ) and others. 
     Further, the control unit  15  may include at least one of a processor, a memory (at least one of read only memory and random access memory), a storage, an interface, a wireless interface, a remote interface, a user input device, a display, an auditory input and an audible output, a network interface, a user input device (such as at least one of a keyboard and a pointing device), at least one of an audible output and an auditory input and any other such devices as are known in the art. Accordingly, the control unit  15  may be controlled by software (machine executable instructions stored on machine readable media) loadable into the control unit  15 , or the control unit  15  may be in communication with the software (such as through an interface to a remote source). Accordingly, the control unit  15  may provide users with precise control (such as governing a setpoint for switching between electrical power and mechanical power), diagnostic information (such as identifying electrical performance of each battery in a plurality of batteries) and performance information (such as identifying hydraulic pressure, flow rate, demand, system temperature, oil life) for governing the hybrid power supply  20 . In some embodiments, the hybrid power supply is configured to limit idling of the engine  2  (such as by providing a large electric storage  18  capable of extended periods of operation). 
     Referring now to  FIG. 3 , exemplary logic  30  for operation of the hybrid power supply  20  is provided. In this example, a user starts operation  31  by operation that may be as simple as flipping a switch. In some embodiments, the hybrid power supply  20  will not engage without setting of safety interlocks (such that auto-start of the engine  2  will not cause an unsafe condition). Subsequently, in a first stage of operation  32 , the control unit  15  powers the hybrid power supply  20  from the electric storage  18 . In an ongoing stage  33 , the control unit  15  monitors the electric supply and tests for adequate power. If the power supplied by the electric storage  18  is not adequate, then the control unit  15  initiates a charging sequence. In a first stage of the charging sequence  36 , the control unit  15  automatically starts the engine  2  of the vehicle  10 . In a next stage of the charging sequence  37 , the generator provides electrical output to the electric storage  18 . In a demand stage of the charging sequence  38 , if a user calls for hydraulic power, the control unit  15  powers the motor/generator  12  and pump  16  using the power take off  11 . Once the ongoing stage  33  determines the electric storage  18  is adequately charged, the control unit  15  terminates the charging sequence  34  and shuts down the engine  2 . Ultimately, the user performs shutdown  39  of the hybrid power supply. 
     The hybrid power supply  20  provides numerous advantages over the prior art. For example, the hybrid power supply  20  permits the hydraulic implement  1  to be used beyond exhaustion of a battery of the vehicle  10 . The hybrid power supply  20  can be installed as a retrofit (i.e., a kit) into many existing vehicles  10 , thus providing for compliance with anti-idle rules and regulations for existing equipment. The hybrid power supply  20  may be used with vehicles having either a manual transmission  3  or an automatic transmission  3 . 
     The flow diagrams depicted herein are just examples. There may be many variations to these diagrams or the steps (or operations) described therein without departing from the spirit of the invention. For instance, the stages may be performed in a differing order, stages may be added, deleted or modified. All of these variations are considered a part of the claimed invention. 
     Further, it should be recognized that the hydraulic implement  1  may include, without limitation, at least one of a lift, jack, drill, wrench, drive, piston, pump, valve, motor, loader, hoe, scoop, mower, digger and any other hydraulically powered mechanism as is known in the art or may be later devised. The hydraulic implement  1  may be a dedicated component (such as one permanently affixed to the vehicle  10 ), or one that is temporarily attached (such as through a coupling or port for switchable use of hydraulic implements). The hybrid power supply  20  may be used in conjunction with any vehicle  10  providing the hydraulic implement  1 . In addition, the hybrid power supply  20  may include a plurality of the components disclosed herein. For example, the hybrid power supply  20  may include a plurality of motors, generators, combination motor/generator units, electric storage units, hydraulic pumps, control units and other supporting components and accessories. 
     In support of the teachings herein, various computer components including software may be had to provide for operation and analyses of the apparatus and methods disclosed herein. Accordingly, it is considered that these teachings may be implemented in conjunction with a set of computer executable instructions stored on a computer readable medium, comprising ROM, RAM, CD ROM, flash or any other computer readable medium, now known or unknown, that when executed cause a computer to implement the method of the present invention. These instructions may provide for equipment operation, control, data collection and analysis and other functions deemed relevant by a user. 
     While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.