Abstract:
A regeneration system for use in a vehicle having a reciprocating-piston engine. The regeneration system captures energy (e.g. braking energy), stores the energy, and subsequently uses the stored energy to generate motive power for the vehicle. The motive power can be generated in conjunction with motive power provided by the engine. The regeneration system comprises a variable displacement pump/motor that is connected to a connecting rod in each cylinder of the engine. The pump/motor comprises a fluid chamber, a primary piston mechanically coupled to the connecting rod and a slave piston coupled to the primary piston via resilient means. A control unit controls a plurality of valves to direct the exchange of pressurized hydraulic fluid between the pump/motor and a hydraulic accumulator in synchronous timing with the operation of the engine.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from U.S. Provisional Patent Application Ser. No. 11/626,497, filed Jan. 24, 2007, the entirety of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of energy recovery systems. In particular, to a regeneration system for use with a reciprocating-piston engine. 
       BACKGROUND 
       [0003]    With the growing concerns over environmental impacts and the every increasing cost of energy products, both producers and consumers of internal combustion engines are interested in means to improve the operational efficiency of these engines. One area receiving considerable attention is the use of energy recovery systems in road vehicles, commonly referred to as hybrids vehicles. These systems have mechanisms for capturing energy during braking, storing the captured energy and later consuming the energy to provide motive power to the vehicle. Typically these systems use a single electrical generator/motor or a single hydraulic pump/motor for capturing the energy and for providing motive power from the captured energy. The generator/motor or pump/motor is typically coupled to the drive-train of the vehicle via a transmission (e.g. a continuously variable transmission) or gear system (e.g. a planetary gear set) that is downstream from the prime mover (e.g. internal combustion engine). Motive power can be provided by the generator/motor or pump/motor in conjunction with motive power provided by the prime mover. When a multi-cylinder reciprocating-piston engine is used as the prime mover, the engine typically generates motive power that includes power pulses that correspond to the power generation sequence of the individual cylinders in the engine. The motive power provided by the generator/motor or pump/motor is not typically synchronized to the power pulses of the internal combustion engine and therefore does not contribute to smoothing out (i.e. mitigating) the power pulses. In some instances (especially in the case of a reciprocating pump/motor) additional asynchronous power pulses may be added to the total motive power flow. 
         [0004]    What is needed is an energy recovery (i.e. regeneration) system for use with a reciprocating-piston engine that can provide motive power in a way that mitigates the power pulses intrinsic to the output of the engine. 
       SUMMARY OF INVENTION 
       [0005]    A regeneration system for use in a vehicle having a reciprocating-piston engine. The regeneration system captures energy (e.g. braking energy), stores the energy, and subsequently uses the stored energy to generate motive power for the vehicle. The motive power can be generated in conjunction with motive power provided by the engine. The regeneration system comprises a pump/motor that is connected to a connecting rod in each cylinder of the engine. The pump/motor comprises a fluid chamber, a primary piston mechanically coupled to the connecting rod and a slave piston coupled to the primary piston via resilient means. The primary and slave pistons reciprocate in the fluid chamber responsive to the movement of the connecting rod and to the injection and discharge of hydraulic fluid to and from the fluid chamber (i.e. the pump/motor). A control unit controls a plurality of valves to direct the exchange of pressurized hydraulic fluid between the pump/motor and a hydraulic accumulator in synchronous timing with the operation of the engine. 
         [0006]    In accordance with one aspect of the present invention, there is provided a regeneration system for use with a reciprocating-piston engine having at least one combustion cylinder in which a piston, connected to a crankshaft by a connect rod, reciprocates, the regeneration system comprising: a hydraulic pump/motor, a source of hydraulic fluid, a three-way control valve, a sink for hydraulic fluid, a pressure control valve, a hydraulic accumulator and a control unit. The hydraulic pump/motor having: a hydraulic chamber; a primary piston for reciprocation in the hydraulic chamber and mechanically coupled to the connect rod; a slave piston for reciprocation in the hydraulic chamber; a resilient mechanism for coupling the slave piston to the primary piston and for providing, in conjunction with the slave piston, variable displacement operation of the pump/motor; and a inlet/outlet port for admitting and expelling hydraulic fluid to and from the hydraulic chamber; wherein the pump/motor is operable in a pump mode for converting power received from the connecting rod to pressurized hydraulic fluid expelled from the hydraulic chamber, and in a motor mode for converting pressurized hydraulic fluid admitted into the hydraulic chamber to motive power transferred to the connecting rod. The source of hydraulic fluid, in fluid communication with the inlet/outlet port via a check valve, for supplying hydraulic fluid to the pump/motor, when operating in pump mode, responsive to an injection control signal. The three-way control valve having a first port, a second port and a third port, the three-way control valve operable, responsive to a position control signal, between a first position in which the first port is in fluid communication with the second port, a second position in which the first port is in fluid communication with the third port, and a third position in which none of the first, second and third ports is in fluid with any other of the first, second and third ports, and wherein the first port is in fluid communication with the inlet/outlet port. The sink, in fluid communication with the inlet/outlet port via the third port of the three-way valve, for receiving hydraulic fluid from the pump/motor, when operating in motor mode, responsive to a dump control signal. The pressure control valve, having an inlet port in fluid communication with the third port of the three-way valve and an outlet port, for varying the resistance to hydraulic flow between the inlet port and the outlet port responsive to a pressure control signal. The hydraulic accumulator, in fluid communication with the second port of the three-way control valve, for supplying pressurized hydraulic fluid to the pump/motor when operating in motor mode, and in fluid communication with the third port of the three-way valve via the outlet port of the pressure control valve for receiving pressurized hydraulic fluid from the pump/motor when operating in pump mode. The control unit for receiving a crankshaft position signal and an accumulator pressure signal, and for generating the injection control signal, the position control signal, the dump control signal and the pressure control signal in accordance the operating mode of the pump/motor, a desired degree of brake force and a desired degree of motive power generation and with timing of the control signals derived from the crankshaft position. Wherein pressurized hydraulic fluid derived from engine power in the pump/motor, operating in pump mode, is received by and stored in the hydraulic accumulator, and motive power derived form pressurized hydraulic fluid, received from the hydraulic accumulator, in the pump/motor, operating in the motor mode, is transferred to the crankshaft. 
         [0007]    Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art or science to which it pertains upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0008]    The present invention will be described in conjunction with drawings in which: 
           [0009]      FIG. 1  is a schematic representation of an exemplary embodiment of a regeneration system for use with a reciprocating-piston engine. 
           [0010]      FIG. 2  is a schematic representation of an alternative exemplary embodiment of the regeneration system for use with a reciprocating-piston engine. 
           [0011]      FIG. 3  is a schematic representation of another alternative exemplary embodiment of the regeneration system for use with a reciprocating-piston engine. 
           [0012]      FIG. 4  is a schematic representation of the position and extension of a hydraulic pump/motor at four illustrative points in the rotation of a crankshaft. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]      FIG. 1  is a schematic representation of an exemplary embodiment of a regeneration system  100  for use with a reciprocating-piston engine. The internal combustion engine has at least one combustion cylinder  910  and a crankshaft  920  for converting the reciprocating motion of an engine piston  930  to rotational motion. The engine piston  930  is connected to the crankshaft  920  by a connecting rod  940 . The internal combustion engine can be any of the well known reciprocating piston type engines operating in a four-stroke or a two-stroke mode of operation. The regeneration system  100  is described herein with reference to a four-stoke, spark ignition (i.e. Otto cycle) engine but is equally applicable to other well known reciprocating piston engine types. The regeneration system  100  comprises a hydraulic pump/motor  110 , a source  120  for supplying hydraulic fluid, a sink  130  for receiving hydraulic fluid, a three-way control valve  140 , a hydraulic accumulator  150  and a control unit  160 . 
         [0014]    The pump/motor  110  is pivotally connected to the connecting rod  940  at a first end and to a point that is stationary relative to the rotational center of the crankshaft  920  at a second end. The connection points of the pump/motor  110  are arranged so that the pump/motor  110  cycles through one intake stroke and one discharge stroke for one complete rotation (i.e. revolution) of the crankshaft  920 .  FIG. 4  is a schematic representation of the position and extension of the pump/motor  110  at four illustrative points in the rotation of the crankshaft  920 . Referring again to  FIG. 1 , the pump/motor  110  has a hydraulic chamber  112  in which a primary piston  114  reciprocates. The primary piston  114  is mechanically connected to the connecting rod  940  so that the primary piston  114  reciprocates in the hydraulic chamber  112  responsive to rotation of the crankshaft  920 . A slave piston  116  is also contained for reciprocation in the hydraulic chamber  112 . The slave piston  116  is coupled to the primary piston  114  by a resilient mechanism  118  such as, for example, a spring. The resilient mechanism  118  is a progressive rate device for which the pressure required to compress the resilient mechanism  118  increases as the resilient mechanism  118  is further compressed. The slave piston  116  in conjunction with the resilient mechanism  118  provide for the pump/motor  110  to operate as a variable displacement device. The pump/motor  110  has an inlet/outlet port  119  for admitting and expelling hydraulic fluid to and from the hydraulic chamber  112 . The pump/motor  110  can be operated alternatively in a pump mode and in a motor mode. 
         [0015]    The source  120  of hydraulic fluid comprises a pump  124  such as, for example, a lubricating pump for the engine, connected to a reservoir  126  of hydraulic fluid such as, for example, the engine oil pan (i.e. sump). The pump  124  outputs hydraulic fluid of sufficient pressure to overcome (i.e. compress) the resilient mechanism  118  in the hydraulic chamber  112 . In an alternative embodiment any other well known similar source of pressurized fluid can be used. The source  120  of pressurized hydraulic fluid further comprises an injection check valve  122  and an injection control valve  125 . The injection check valve  122  permits the flow of pressurized hydraulic fluid from the pump  124  to the pump/motor  110  and prevents flow in the opposite direction. The source  120  of hydraulic fluid is connected in fluid communication with the inlet/outlet port  119  for supplying hydraulic fluid to the pump/motor  110 , operating in pump mode, via the injection control valve  125 . The injection control valve  125  is operable between a closed position blocking fluid flow-through and an open position permitting fluid flow-through responsive to an injection control signal from the control unit  160 . The volume of hydraulic fluid injected into the pump/motor  110  can be regulated by the timing (relative to the rotational position of the crankshaft) and duration (e.g. a modulation pulse width) of opening of the injection control valve  125 . The volume of injected hydraulic fluid can be varied from none (i.e. no fluid) to the maximum volume of the hydraulic cylinder  112 . In an alternative embodiment (not illustrated) the injection control valve  125  can be pressure control type valve that, responsive to the injection control signal, controls the flow of hydraulic fluid by regulating a pressure differential between an inlet side (i.e. from the dump  124 ) and an outlet side (i.e. toward the inlet/outlet port  119 ) of the injection control valve  125 . 
         [0016]    The sink  130  for pressurized hydraulic fluid comprises a reservoir  126  for hydraulic fluid such as, for example, the engine oil pan (i.e. sump) and a dump valve  135  that alternately permits the flow of pressurized hydraulic fluid toward the reservoir  126  responsive to a dump control signal from the control unit  160  and blocks the flow of pressurized hydraulic fluid toward the reservoir  126 . The sink  130  for receiving hydraulic fluid is connected, via the three-way control valve  140 , in fluid communication with the inlet/outlet port  119  for receiving hydraulic fluid from the pump/motor  110  when operating in motor mode. 
         [0017]    The three-way control valve  140  comprises a first port  141 , a second port  142  and a third port  143 . The three-way control valve  140  is operable between a first position in which the first port  141  is in fluid communication with the second port  142 , a second position in which the first port  141  is in fluid communication with the third port  143  and a third position in which none of the ports  141 ,  142 ,  143  is in fluid communication with any other of the ports  141 ,  142 ,  143  (i.e. fluid flow through the three-way valve  140  is blocked). The first port  141  is connected in fluid communication with the inlet/outlet port  119  of the pump/motor  110  and the third port  143  is connected in fluid communication with the sink  130 . 
         [0018]    The hydraulic accumulator  150  is connected in fluid communication with the second port  142  of the three-way control valve  140  for supplying pressurized hydraulic fluid to the pump/motor  110  when operating in motor mode. The hydraulic accumulator  150  is connected in fluid communication with the third port  143  of the three-way control valve  140  via a pressure control valve  176  for receiving pressurized hydraulic fluid from the pump/motor  110  when operating in pump mode. 
         [0019]    The control unit  160  provides for controlling the injection control valve  125 , the three-way control valve  140 , the pressure control valve  176  and the dump valve  135  in accordance the operating mode of the pump/motor (i.e. pump mode or motor mode), a desired degree of brake force and a desired degree of motive power generation. The three-way control valve  140  can be operated into any of the first position, the second position and the third position, as described above with reference to  FIG. 1 , responsive to a position control signal from the control unit  160 . The control unit  160  receives a signal from a crankshaft position sensor  925  from which the rotational position of the crankshaft  920  can be derived. The position of the combustion piston  930  can be derived from a pre-determined relationship between the combustion cylinder  910  and the crankshaft  920 . The position of the primary piston  114  can be derived from a pre-determined relationship between the primary piston  114  and the connecting rod  940 . The control unit  160  further receives a pressure signal from a pressure transducer  155  in fluid communication with the accumulator  150 . 
         [0020]    Referring to the exemplary embodiment of  FIGS. 1 and 4 , as the crankshaft  920  rotates and the engine piston  930  reciprocates, the primary piston  114  of the pump/motor  110  also reciprocates in the hydraulic chamber  112 . The connection of the pump/motor  110  to the connecting rod  940  is arranged so that the hydraulic chamber  112  volume is minimized when the engine piston  930  is proximate 90 degrees after its top-dead-center (TDC) position in the combustion cylinder  910 . The TDC position corresponds to the 0 (zero) degree and the 360 degree positions for the purposes of this document. The hydraulic chamber  112  volume is maximized when the engine piston  930  is proximate 270 degrees after the TDC position. 
         [0021]    In an alternative embodiment (not illustrated) the connection of the pump/motor  110  to the connecting rod  114  can be arranged so that the hydraulic chamber  112  volume is minimized when the engine piston  112  is proximate another predetermined rotational position (e.g. any position between 0-180 degrees relative to TDC) and the hydraulic chamber  112  volume is maximized at a position 180 degree after the predetermined rotational position. The alternative embodiment will function substantially as described in this document with reference to the preferred embodiment except that the timing relationships are adjusted accordingly. 
         [0022]    When the pump/motor  110  is operating in pump mode, hydraulic fluid is pressurized in the pump/motor  110  and then is subsequently transferred to the hydraulic accumulator  150  (i.e. the regeneration system  100  is storing energy). Hydraulic fluid from the source  120  is injected into hydraulic chamber  112  via inlet/outlet port  119  as the engine piston  930  moves between a minimum hydraulic chamber  112  volume position and a maximum hydraulic chamber  112  volume position (e.g. proximately 90 degrees to 270 degrees after TDC). The volume of hydraulic fluid injected into the hydraulic chamber  112  is regulated by the timing and duration of opening of the injection control valve  125  responsive to the injection control signal received from the control unit  160 . The volume of injected hydraulic fluid can be varied from none (i.e. no fluid) to the maximum volume of the hydraulic cylinder  112 . The injected hydraulic fluid is of sufficient pressure to overcome the resilient mechanism  118 . The slave piston  116  in conjunction with the resilient mechanism  118  compensate for any difference between the volume of injected hydraulic fluid and the increasing volume of the hydraulic chamber  112 . Hydraulic fluid is expelled from the hydraulic chamber  112  via inlet/outlet port  119  as the engine piston  930  moves between the maximum hydraulic chamber  112  volume position and the minimum hydraulic chamber  112  volume position (e.g. proximately 270 degrees after TDC, through TDC, to 90 degrees after TDC). The hydraulic fluid is directed to the hydraulic accumulator  150  via the three-way valve  140  operated into the second position in which the first port  141  and third port  143  are in fluid communication. The pressure control valve  176  is hydraulically connected between the three-way valve  140  and the hydraulic accumulator  150 . Responsive to a pressure control signal from the control unit  160 , the pressure control valve  176  regulates a pressure differential between an inlet side (i.e. from the pump/motor  110 ) and an outlet side (i.e. toward the accumulator  150 ). The pressure control valve  176  can vary the resistance to fluid flow from the inlet side to the outlet side. The resistance to fluid flow generated by the pressure control valve  176  can create a backpressure on the pump/motor  110  inlet/outlet port  119 . The degree of backpressure on the pump/motor  110  regulates a brake effect created by the pump/motor  110  in pumping mode. The braking effect in the pump/motor  110  is imparted to the crankshaft  920  thereby creating engine braking. Pressurized hydraulic fluid flowing through the pressure control valve  176  is stored in the accumulator  150 . 
         [0023]    A pressure relief valve  172  is also connected to the hydraulic accumulator  150 . The pressure relief valve  172  opens when a pre-determined pressure threshold is exceeded to release hydraulic fluid and pressure from the hydraulic accumulator  150  toward the reservoir  126 , via an optional heat sink  174 , to prevent over pressurization of the accumulator  150 . 
         [0024]    The amount of energy extracted from the internal combustion engine is proportional to the volume of hydraulic fluid expelled from the pump/motor  110  when operating in pump mode. A smaller volume expelled corresponds to less energy extracted and a larger volume expelled corresponds to more energy extracted. The volume of fluid expelled is substantially equal to the volume of fluid injected. When it is desirable to minimize any parasitic load on the internal combustion engine caused by the regeneration system  100 , no fluid is injected in pump mode and therefore no energy is extracted. 
         [0025]    When the pump/motor  110  is operating in motor mode, hydraulic fluid in the hydraulic accumulator  150  is transferred to the pump/motor  110  to provide power to be imparted to the crankshaft  920  via the connecting rod  940  (i.e. the regeneration system  100  is converting stored energy to motive power). Hydraulic fluid from the hydraulic accumulator  150  is injected into hydraulic chamber  112  via the inlet/outlet port  119  as the engine piston  930  moves between the minimum hydraulic chamber  112  volume position and the maximum hydraulic chamber  112  volume position (e.g. proximately 90 degrees to 270 degrees after TDC). The injection of hydraulic fluid is regulated using the three-way valve  140  operated into the first position in which the first port  141  and second port  142  are in fluid communication. The volume of hydraulic fluid injected into the hydraulic chamber  112  is regulated by the timing (relative to the rotational position of the crankshaft) and duration (e.g. a pulse width modulated duration) of operating the three-way control valve  140  into the first position responsive to a position control signal received from the control unit  160 . The volume of injected hydraulic fluid can be varied from none (i.e. no fluid) to the maximum volume of the hydraulic cylinder  112 . The injected hydraulic fluid is of sufficient pressure to overcome the resilient mechanism  118 . The slave piston  116  in conjunction with the resilient mechanism  118  compensates for any difference between the volume of injected hydraulic fluid and the increasing volume of the hydraulic chamber  112 . Hydraulic fluid is expelled from the hydraulic chamber  112  via inlet/outlet port  119  as the engine piston  930  moves between the maximum hydraulic chamber  112  volume position and the minimum hydraulic chamber  112  volume position (e.g. proximately 270 degrees after TDC, through TDC, to 90 degrees after TDC). The hydraulic fluid is directed toward the sink  130  via the three-way valve  140  operated into the second position in which the first port  141  and third port  143  are in fluid communication. The dump valve  135  is opened responsive to a dump control signal from the control unit  160  to provide a fluid path to the reservoir  126  and thereby minimize backpressure on the hydraulic fluid being expelled from the pump/motor  110 . The volume of hydraulic fluid injected into the pump/motor  110  regulates a motive power generated by the pump/motor  110  in motor mode. The motive power generated by the pump/motor  110  is imparted to the crankshaft  920  thereby adding to the motive power generated by the engine. 
         [0026]      FIG. 2  is a schematic representation of an alternative exemplary embodiment of the regeneration system  100  for use with an exemplary internal combustion engine having four combustion cylinders. Operation of each of the components comprising the regeneration system  100  is substantially the same as for the corresponding component described above with reference to  FIG. 1  except as noted below. For clarity, only the connecting rods  940  of each of the four combustion cylinders are illustrated. Each of the four connecting rods  940  (i.e. combustion cylinders) has a corresponding a separate pump/motor  110 . The pump/motor  110  for each combustion cylinder  910  has an associated check valve  122 . The pump  124 , injection control valve  125 , and reservoir  126  for hydraulic fluid are common and shared by all of pump/motors  110 . Each pump/motor  110  is in hydraulic communication with a separate three-way control valve  140 . A hydraulic gallery  170  (i.e. manifold) interconnects the third port  143  of each of three-way control valves  140 . The dump control valve  135 , the pressure control valve  176 , the accumulator  150 , the pressure transducer  155 , the control unit  160 , the pressure relief valve  172 , and the heat sink  174  are common and shared by all of combustion cylinders. The combustion cylinders are rotationally spaced apart with respect to their connection to the crankshaft to provide a predetermined firing order (i.e. ignition sequence). Each of the pump/motors  110  is in a fixed timing relationship with a corresponding combustion cylinder. The control unit  160  times (relative to the rotational position of the crankshaft) the operation of the injection control valve  125 , the pressure control valve  176 , the dump valve  135 , and each of the three-way valves  140  based on the predetermined firing order and the derived crankshaft position in order to synchronize control of each of the pump/motors  110  with the corresponding combustion cylinder. For example, when operating in motor mode the injection of fluid into each pump/motor  110  can be timed to coincide with an intake stroke of the corresponding combustion cylinder thereby complimenting power pulses generated in power strokes of the corresponding combustion cylinder. In  FIG. 2 , each of the pump/motors  110  is illustrated with a volume of hydraulic fluid injected into each hydraulic cylinder  112  less than the maximum volume of the hydraulic cylinder  112 . The arrows adjacent to the connecting rods  940  indicate the direction of travel of the primary piston  114  in the corresponding pump/motor  110 . 
         [0027]      FIG. 3  is a schematic representation of an alternative exemplary embodiment of the regeneration system  100  for use with an exemplary internal combustion engine having four combustion cylinders. The regeneration system of  FIG. 3  is similar to and operates in substantially the same way as the regeneration system  100  described above with reference to  FIG. 2  with the following exceptions. The regeneration system  100  does not comprise the pressure control valve  176 , instead a discharge check valve  178  is in fluid communication between the hydraulic gallery  170  and the accumulator  150  for permitting the transfer of pressurized hydraulic fluid to the accumulator  150  and for preventing flow in the opposite direction. The degree of backpressure applied to the pump/motor  110  in pumping mode is not regulated by the control unit  160 , instead it is a function of the pressure in the accumulator  150 . In  FIG. 3 , each of the pump/motors  110  is illustrated with a zero volume of hydraulic fluid (i.e. no fluid) injected into each hydraulic cylinder  112 . The arrows adjacent to the connecting rods  940  indicate the direction of travel of the primary piston  114  in the corresponding pump/motor  110 . 
         [0028]    In a further alternative embodiment the regeneration system  100  can be used with a reciprocating-piston engine having one or more combustion cylinders  930  and operating substantially as described above with reference to  FIGS. 1-4 . 
         [0029]    It will be apparent to one skilled in the art that numerous modifications and departures from the specific embodiments described herein may be made without departing from the spirit and scope of the present invention.