CA1285887C - Mechanical power regeneration system - Google Patents
Mechanical power regeneration systemInfo
- Publication number
- CA1285887C CA1285887C CA000525478A CA525478A CA1285887C CA 1285887 C CA1285887 C CA 1285887C CA 000525478 A CA000525478 A CA 000525478A CA 525478 A CA525478 A CA 525478A CA 1285887 C CA1285887 C CA 1285887C
- Authority
- CA
- Canada
- Prior art keywords
- pump
- pressure accumulator
- controlled
- hydraulic
- check valve
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 230000008929 regeneration Effects 0.000 title claims abstract description 19
- 238000011069 regeneration method Methods 0.000 title claims abstract description 19
- 238000006073 displacement reaction Methods 0.000 claims abstract description 28
- 239000012530 fluid Substances 0.000 claims abstract description 16
- 230000005540 biological transmission Effects 0.000 claims abstract description 10
- 239000000446 fuel Substances 0.000 abstract description 7
- 239000003921 oil Substances 0.000 description 13
- 230000006870 function Effects 0.000 description 9
- 238000004146 energy storage Methods 0.000 description 8
- 230000000979 retarding effect Effects 0.000 description 4
- 230000008901 benefit Effects 0.000 description 3
- 230000001172 regenerating effect Effects 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 230000007935 neutral effect Effects 0.000 description 2
- 208000032369 Primary transmission Diseases 0.000 description 1
- 208000036366 Sensation of pressure Diseases 0.000 description 1
- 102100033740 Tenomodulin Human genes 0.000 description 1
- 101710114852 Tenomodulin Proteins 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011038 discontinuous diafiltration by volume reduction Methods 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 239000010720 hydraulic oil Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 238000012163 sequencing technique Methods 0.000 description 1
Classifications
-
- Y02T10/6208—
Landscapes
- Control Of Fluid Gearings (AREA)
Abstract
MECHANICAL POWER REGENERATION SYSTEM
ABSTRACT OF THE DISCLOSURE
A mechanical power regeneration system for a road vehicle has a sole variable displacement hydraulic pump in the transmission system, the sole hydraulic pump being driven by the rear wheels of the vehicle and thus may be positive-ly driven by the drive axle of the vehicle, whilst a first check valve is connected between the output side of the pump and a first hydraulic line to a high pressure accumulator unit, a second hydraulic line to a low pressure accumulator unit, a second check valve is connected between the second hydraulic line and the input side of the pump, a first con-trolled valve is connected between the first hydraulic line and the input side of the pump and a second controlled valve is connected between the second hydraulic line and the output side of the pump. In operation, when the brakes of the vehicle are applied to place it in a braking mode the first and second controlled valves are controlled by a controller unit to be closed and hydraulic fluid is transferred by the pump from the low pressure accumulator to the high pressure accumulator through the second check valve and the first check valve.
When the vehicle is placed in a drive mode and requires a positive traction force, the controller unit controls the first and second controlled valves to open and stored hydrau-lic energy in the high pressure accumulator is transferred by means of fuel flow through the first controlled valve to the input side of the pump to apply a positive traction force to the rear wheels, the return path of the fluid leaving the pump being from its output side through the second controlled valve to the low pressure accumulator unit. The invention may be used with movable objects other than road vehicles For example, the invention may be applied to elevators or other lifts.
ABSTRACT OF THE DISCLOSURE
A mechanical power regeneration system for a road vehicle has a sole variable displacement hydraulic pump in the transmission system, the sole hydraulic pump being driven by the rear wheels of the vehicle and thus may be positive-ly driven by the drive axle of the vehicle, whilst a first check valve is connected between the output side of the pump and a first hydraulic line to a high pressure accumulator unit, a second hydraulic line to a low pressure accumulator unit, a second check valve is connected between the second hydraulic line and the input side of the pump, a first con-trolled valve is connected between the first hydraulic line and the input side of the pump and a second controlled valve is connected between the second hydraulic line and the output side of the pump. In operation, when the brakes of the vehicle are applied to place it in a braking mode the first and second controlled valves are controlled by a controller unit to be closed and hydraulic fluid is transferred by the pump from the low pressure accumulator to the high pressure accumulator through the second check valve and the first check valve.
When the vehicle is placed in a drive mode and requires a positive traction force, the controller unit controls the first and second controlled valves to open and stored hydrau-lic energy in the high pressure accumulator is transferred by means of fuel flow through the first controlled valve to the input side of the pump to apply a positive traction force to the rear wheels, the return path of the fluid leaving the pump being from its output side through the second controlled valve to the low pressure accumulator unit. The invention may be used with movable objects other than road vehicles For example, the invention may be applied to elevators or other lifts.
Description
-~ 2~5~
MECHANICAL POWER REGENERATION SYSTEM
This invention relates to a mechanical power regener-ation system for storing and converting energy resulting from braking of a moving object such as a vehicle or elevator.
BACK~ROUND OF THE INVENTION
In United Kingdom Patent No. 2,065,836 (granted May 10, 1984) one of the inventors, William S. Heggie, describes a hydraulic transmission system which has been used successfully for vehicles. In that system two variable displacement hy-draulic pump units are used and a hydraulic unit is coupled to the engine.
In other proposed systems two or more hydraulic pumps are used as well as a relatively large number of hydraulic components, one connected to the engine and one connected to the wheels through a clutch arrangement - see, for example, the description of a VOLVO system in the United Kingdom publi-cation "The Automotive Engineer" April/May 1986, page 20.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a mechanical power regeneration system which is of simpler construction.
According to the present invention there is provided a mechanical power regeneration system for a movable object comprising a sole variable displacement hydraulic pump in the power regeneration system, said sole hydraulic pump being directly geared to the movable object and thus may be positively driven by the movable object, a first check valve connected between the output side of said pump and a first hydraulic line of a high pressure accumulator unit, a second hyd~aulic line of a low pressure accumulator unit, a second check valve connected between said second hydraulic line and the input side of said pump, a first controlled valve connected between said first hydraulic line and said input side of said pump, a secsnd controlled valve connected between said second hydraulic line and said output side of said pump, whereby, in operation, when said movable object is to be slowed down by placing it in a braking mode said first and second controlled valves are controlled by a control unit to be closed and hydraulic :.
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fluid is transferred by said pump from said low pressure accumulator to said high pressure accumulator through said second check valve and said ~irst check valve, and when the movable object is placed in a drive mode and requires a posi-tive traction force said control unit controls said firstand second controlled valves to open and stored hydraulic energy in said high pressure accumulator is transferred via hydrualic fluid through said first controlled valve to the input side of said pump to apply a positive traction force to said movable object, the return path of said hydraulic fluid pump being from its output side through said second controlled valve to said low pressure accumulator unit.
More specifically the pxesent invention provides a mechanical power regeneration system for a bus comprising a 15 sole variable displacement hydraulic pump in the power regen- :
eration system, said sole hydraulic pump being directly geared to the rear wheels of the bus and thus may be positively driven by the drive axle of said bus, a first check valve connected between the output side of said pump and a first hydraulic line of a high pressure accumulator unit, a second hydraulic line of a low pressure accumulator unit, a second check valve connected between said second hydraulic line and the input side of said pump, a first controlled valve connected between said first hydraulic line and said input side of said pump, a second controlled valve connected between said sacond hy-draulic line and said output side of said pump, whereby, in : operation, when the brakes of said bus are applied to placa it in a braking mode said first and second controlled valves are controlled by a control unit to be closed and hydraulic fluid is transferred by said pump from said low pressure accumulator to said high pressure accumulator through said second check valve and said first check valve, and when the bus is placed in a drive mode and requires a positive trac-tion force said control unit controls said first and second controlled valves to open and stored hydraulic energy in said high pressure accumulator is transferred through said :
first controlled valve to the input side of said pump to apply a positive traction force to said rear wheels, the :
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9L28S~38~
return path of said pump being from its output side through said second controlled valve to said low pressure accumulator unit O
DESCRIPTION OF THE DRAWINGS
Figure 1 is a diagrammatic representation of a me i chanical power regeneration system for a rear engined bus, Figure 2 diagrammatically illustrates, in block form, a controller unit with the connection lines to units in Figure 1, and Figure 3 diagrammatically illustrates the controller unit in greater detail.
DESCRIPTION OF SOME EMBODIMENTS
Referring to Figure 1, there is disclosed a mechani-. cal power regeneration system suitable for use with a bus.
The power regeneration system includes only one variable dis-placement hydraulic pump/motor unit 2 which is directly driven from the rear wheels 4 and 6 to be always positively driven thereby when the wheels turn. 'It is to be noted that the pump 2 is connected to the differential unit 8 on the drive axle 2Q lO independently of the engine 12.
The output side of pump 2 is connec~ed through a ; first hydraulic check valve 14 to a first hydraulic line 16 connected to the hydraulic connection of a high pressure : accumulator unit 18.
A second hydraulic line 20 is connected to a low pressure accumulator 22. A second check valve 24 is connect-ed between said second hydraulic line 20 and the input side :~
: of pump 20 In Figure l, a first controlled valve 26 is shown connected between line 16 and the input side of pump 2 whilst a second controlled valve 28 is connected between the output side of pump 2 and the line 20~ ~.
A third check valve 30 is in series with a first controlled relief valve 32 and the series ~rrangement is connected across the output and input sides of said pump 2 with valve 30 arranged to pass fluid when the pressure at -~ the output side of pump 2 is greater than the pressure at : the input side of pump 2 and when said first controlled relief .
-, .,, - . .
.: . :. . .- - .: . .. : -5~7 to the high pressure accumulator unit 18. Every time the brake pedal is actuated, for normal levels of retardation, the hydraulic system comes into operation to retard the vehicle without use of the service brakes. In this condi--tion, the pump 2 recharges the accumulator 180 When the bus is driven normally, in its drive mode, and the bus initially requires a positive traction force then action on the accelerator pedal causes the controller unit 50 (Figure 2) to open valves 26 and 28 whilst maintain-ing valves 32 and 36 closed. Any stored energy in the highpressure accumulator unit 18 is re-applied to the driving wheels 4 and 6, by discharging the high pressure oil through valve 26 to the inlet side of pump 8. The path of the oil is then from the outlet side of pump 2 through the valve 28 to the low pressure accumulator unit 22.
It is to be noted that only one pump 2 and two con-trolled valves 26 and 28 are required for operation of the ~ bus as described above. Valves 32 and 36 are merely relief -~ valves~ Valve 36 is controlled to open when thebus is placed in a reverse mode so as to act as a relief line for the hydraullc pressure produced by pump 2. The path of the oil is from the inlet s~de of pump 2, through relief valve 36, through check - valve 34 back to the output side of pump 2.
SUI~MARY - PRINCIPLES OF OPERATION
~- 25 RUISE MODE (Mo hydraulic brakin~ or tr ction) - Pump 2 - displacement at minimum Engine fuel lever = f (Accelerator pedal positionO3 Valves 26 and 28 open.
BRAKING MODE
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- 30 Pump 2 - displacement = f (Brake pedal position, (pressure at gauge 40) Valves 26 and 28 closedO
- Oil is transferred from low pressure accumulator 22 to high pressure accumulator 18, providing retarding force to road wheels via pump 2.
HOLD MODE (Hi~h Pressure accumulator ener~y hold) . . _ Valve 26 closed.
Valve 28 open.
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- ~: . ., . ~. :
.
.- . , ' ~ :
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~ ~S~1~7 , to the high pressure accumulator unit 18. Every time the brake pedal is actuated, for normal levels of retardation, the hydraulic system comes into operation to retard the vehicle without use of the service brakes. In this condi-tion, the pump 2 recharges the accumulator 18nWhen the bus is driven normally, in its drive mode, and the bus initially requires a positive traction ~orce ` then action on the accelerator pedal causes the controller unit 50 (Figure 2) to open valves 26 and 28 whilst maintain-- 10 ing valves 32 and 36 closed. Any stored energy in the high pressure accumulator unit 18 is re-applied to the driving wheels 4 and 6, by discharging the high pressure oil through valve 26 to the inlet side of pump 8. The path of the oil is then from the outlet side of pump 2 through the valve 28 - 15 to the low pressure accumulator unit 22.
; It is to be noted that only one pump 2 and two con-trolled valves 26 and 28 are required for operation of the bus as described above. Valves 32 and 36 are merely relief valves. Valve 36 is controlled to open when the~us is placed in a reverse mode so as to act as a relief line for the hydraul~c pressure produced by pump 2. Th~ path of the oil is from the inlet side of pump 2, through relief valve 36, through check valve 34 back to the output side of pump 2.
SUMMARY - PRINCIPL}5S OF OPERATION
25 CRUISE MODE (Mo hydraulic brakinq or traction) Pump 2 - displacement at minimum Engine fuel lever = f ~Accelerator pedal positionO3 Valves 2 6 and 28 open.
BRAKING MODE
Pump 2 - displacement = f (Brake pedal position, (pressure at gauge 40) Valves 26 and 28 closPd.
Oil is transferred from low pressure accumulator 22 to high pressure accumulator 18, providing retarding force to road wheels via pump 2.
HOLD MODE IHi~h pressure accumulator ener~y hold) Valve 26 closed.
Valve 28 open.
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6~Z8~887 HYDRAULIC TR~CTION
Pump 2 - displacement = f (Accelerator p~dal) Engine fuel lever = f (Accelerator pedal, pressure at gauge 38) Valves 26 and 28 open.
High pressure oil in accumulator 18 discharges to accumulator 22 via pump 2, providlng a tractive force to the road wheels.
On exhaustion of high pressure accumulator charge, lQ pump 2 displacement is set to minimum giving the CRUISE mode above.-REVERSE
Valve 26 is closed. Valve 28 is open.
Relief valve 36 is open.
High pressure accumulator charge is held.
- Oil transfer from pump is recirculated.
A significant finding we made was that the thermo-dynamically ideal accumulator (that which provides a given energy storage capacity at the minimum gas volume), does not provide the optimum perfo`rmance, considering overall energy conservation, over the range of real driving situations.
~- The performance analyses presented here have per-mitted the design parameters for a prototype vehicle to be optimised to significant advantage.
PUMP SIZE AND OE ARING
In practice, it is necessary to speed up the pump drive in order to obtain adequate energy conversion rates using any of the currently available sizes of hydraulic pumpsO
In predicting the retardation, it is necessary to relate the hydraulic pressure, to the retarding tractive effort.
Pump power PP = DP.dP(Np/60) kW (1) where Np = VEL.RR.DR/RS revs/min. (2) ; Tractive force TF = PP/VEL.3600 N (3) = DPodP(VEL.RR.DR/RS/60).(3600/VEL) N (4) ; where:
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Sy~bol Description Unit dP = Pump differential pressure MPa DP - Pump Displacement/revolution DR = Pump gearbox speedup ratio LOP = Lower Operating Pressure MPa Np = Pump speed revs/min PP = Pump Power kW
RR = Driveshaft speed at RSrevs/min RS = Vehicle Road Speed or RR km/h lO SPD = Specific Pump Displacement Q/m travel TF = Tractive Force N
VEL = Vehicle velocity km/h Eq. (4) can usefully be simplified by introducing the concept of Specific Pump Displacement, which may be de-fined as the volumetric displacement of the hydraulic pump per unit of linear vehicle travel.
i.e. Spècific Pump Displacement SPD = DP.DR.RR/RS.60/lOOO /m (5) giving TF = SPD.dP.lO N (6) R. Sandri and W.S. Heggie, in "Heat Transfer and Energy Storage in Pneumatic Accumulators"~ International Symposium, Advanced and Hybrid Vehicles, University of Strath-- clyde, September 1984, have shown the fundamental gas charac-25 teristics of the pressure range of interest 20-3709 MPa (3-5000 psi). From this, the gas volume and pressure limits re-quired for the storage of a given quantity of energy can be determined. There is an optimum LOP of approximately 10.4 MPa (1530 psi).
It should be noted that the relationship between the specific energy storage and the LOP is a general relation-ship, whereas the relationship between the actual gas volume and the LOP is depen-dent on the quantity of energy to be stored.
In either case, the actual values are affected by the pressure in the low pressure accumulator over the cycle.
The most obvious advantage obtained by raising the LOP, is the corresponding increase in tractive effort obtained in accordance with Eq. l6). There will however be a severe ..... . . . . . . .
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~X8S~37 reduction in energy s~orage capacity i~ the LOP is increased much above 20 MPa (3000 psi).
- HYDRO-PNEUMATIC ENERGY STORAGE CHARACTERISTICS
There are two characteristics of special note, related to the fact that as the magnitude o~ the stored ener-gy is increased within a given accumulator, there is a simultaneous reduetion in gas volume and increase in pressureO
Firstly, the quantity of energy stored at any in-stant is dep~ndent on the volume displaced by the oil. This corresponds to the distance travelled during stopping, assum-ing a constant pump displacement. Secondly, as the gas pres-sure increases as a power function of the-volume reduction, the hydraulic oil pressure, (equalling the gas pressure), will give rise to a tractive retarding force also increasing as a power function of the distance travelled during the retarda-tion, with the same pump displacement.
REQUIRED SYSTEM PERFORMANCE
Little information was available concerning the actual braking cycles involved in typical city bus routes.
Therefore some data was collected from a bus travelling along a 6 mile radial route between a city and its suburb. It was found that the majority of the stops occurred at an average retardation rate not exceeding 1.68 m/s ~5.5 ft/sec); and - that the majority of the stops occurred in the 32 to 48 km/h (20 to 30 mph) range. The following performance targets for the energy recovery system were derived from this data:-1. The system should be able to fuliy store the available kinetic energy for a 48 km/h (30 mph) stop~
2. The system should be capable o~ providing an average retardation rate of 1.68 m/s (5.5 ft/sec) for a stop from 32 km/h (20 mph).
Due to the gas compression characteristics mentioned above, this target implies that the 48 km/h (30 mph) stop, would exceed the 1.68 m/s (5.5 ft/sec ) limit at the same pump displacement-In the test bus, ~ree piston cylindrical accumulators --- . ' .
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~28S887 units were usedO With the bladder type accumulator, parti-cularly when mounted in the horizontal position, the bag tends to take an off-centre attitude, resulting in an oil velocity differential between opposite sides, tendin~ to further draw the bag to the lower velocity side. This can cause fluttering resulting in bag damage and pressure fluctuation.
A bent axis multiple co-axial piston was used as a pump/motor 2 because it displays several advantages over swash-plate devices, including better overall efficiency especially at low displacement.
Pilot opPrated check valves wére used where 100~
shut off is important and also to simplify valve sequencing operationsO
In the block schematic of the controller unit 50 in Figure 2, the inputs to the controller unit are from the accelerator pedal o~ the bus and the brake pedal via appro-priate rheostats as shown in greater detail in Figure 3.
An input is also obtained from the gear selector of the bus to indicate when gear is in reverse (R~, drive (D) or neutral ; 20 (N)o The outputs of controller unit S0 go to valve 26, 28, 36 and to engine 12 (Figure 1). A connection is also ; shown in relation to the Hydraulic Pump displacement.
The Controller unit is shown in greater de~ail in Figure 3. The nomenclature used will be clear from Figure 3 and is standard to that used by persons skilled in the art. Certain graphical representations are included for clarity.
The processor used on the bus was a custom designed unit based on a single board microcomputer utilizing an 8086 CPU. The system was designed to act as both a system controller and data ac~uisition system. The control program and test data were stored on a removable bubble memory.
Re~erring to Figure 3, driver input is provided by a modified gear shi~t and potentiometers 52 and 54 operated - by the accelerator (Ap) and the brake pedal (Bp). Five out~
; puts control the three valves 26, 28 and 36, the fuel rack (Ra) and the pump/motor displacement (D2).
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-- 10 -- , ~8S88~
Functions Fl and F2 modify the output of the con-troller 50 to the fuel rack, melding engine with accumulator power to provide a repeatable response to the accelerator (Ap) regardless o~ the state of charge of the high pressure accumulator 18 as indicated by gauge 38 ~Figure 1).
The double switch (SW) disables displacement con-trol (D2) of the pump/motor unit 2 of Figure 1 and pro~ides fuel rack control as a direct function of the accelerator potentiometer 52 when reverse or neutral modes are selected.
The same is true when operating with the high pressure accumu-lator 18 fully discharged.
In Figure 3, F3 is used to attenuate pump displace-ment when the accumulator is fully charged to limit thermal -build up at the relief valve. F4 and F5 provide modulation of the hydraulic tractive effort during acceleration and braking respec~ively.
Function F7 backs off Pump/Motor displacement as a function of speed to comply with speed load restrictions.
Function F6 acts similarly to F'7 except that it is based on inlet pressure as an anti-cavitation protection.
The latter two functions were devised in order to design safely for the maximum ratings o~ the hydraulic trans-mission system~ The alternative, of course, would be a larger unit or gearing down the speed with a consequent loss of performance.
In Figure 3 the setting of the movable arm of poten-tiometer 52 is dependent on the position othe accelerator pedal of the bus. The setting determines the magnitude of input signal ~AP) provided to the microcomputer unit. Simi-larly, the setting of the movable arm of potentiometer 54determines the magnitude of the input signal (BP) provided to a second input of the microcomputer unit. The microcom- -puter unit is designed to analyse its inputs and to pro~ide . corresponding control signals to the controlled valves 26 and 28 (Figure 1).
The microcomputer is also responsive to the gear - lever of the bus being placed in reverse. A further control -- signal is then provided to controlled relief valve 36 (Figure 1) whereby the hydraulic fluid from the pump 2 is recirculated - . . . ~: ,- . . ......... ' ... :' . - . . . ' ., ~
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128S8~3~
through the controlled relief valve 36 and check valve 34.
There has been described, a system designed to regenerate mechanical energy, being separate and distinct from the primary power transmission which connects a prime mover (iOe. internal or external combustion engine, electxic motor etc.) to its load; the system comprising:-variable displacement hydraulic unit which may function as either a pump or a motor, and which is directly coupled to the load; a high pressure, hydro-pneumatic accumulator or energy storage; a low pressure hydro-pneumatic accumulator, to serve as a reservoir of oil of adequate pressure to satis-fy the requirements of the pump/motor unit, an energy storage sensor,, which provides a measure of the energy level in the energy storage unit, for use by regenerative power control system, and a control system which controls the prime mover power level, the power regenerator power level, and the active control valves, using as operator inputs, only such convention-al controls as accelerator and brake pedals, and primary trans-mission control inputs.
Two active controllable valves determine the control mode of the regenerative power system. The power regenerator may be separable from the load by means of a mechanical clutch, under automatic control. The prime mover may be disconnected from the load, under automatic control. The regenerative power controller may generate a control demand on the primary power trans~ission, for the selection of a drive ratio.
The power regenerator and the energy storage devices may, of course, be electrical.
It will be readily apparent to a person skilled in the art that a number of variations and modiications can be made without, departing ~rom the true spirit of the inven-tion which will now be pointed out in the appended claims.
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MECHANICAL POWER REGENERATION SYSTEM
This invention relates to a mechanical power regener-ation system for storing and converting energy resulting from braking of a moving object such as a vehicle or elevator.
BACK~ROUND OF THE INVENTION
In United Kingdom Patent No. 2,065,836 (granted May 10, 1984) one of the inventors, William S. Heggie, describes a hydraulic transmission system which has been used successfully for vehicles. In that system two variable displacement hy-draulic pump units are used and a hydraulic unit is coupled to the engine.
In other proposed systems two or more hydraulic pumps are used as well as a relatively large number of hydraulic components, one connected to the engine and one connected to the wheels through a clutch arrangement - see, for example, the description of a VOLVO system in the United Kingdom publi-cation "The Automotive Engineer" April/May 1986, page 20.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a mechanical power regeneration system which is of simpler construction.
According to the present invention there is provided a mechanical power regeneration system for a movable object comprising a sole variable displacement hydraulic pump in the power regeneration system, said sole hydraulic pump being directly geared to the movable object and thus may be positively driven by the movable object, a first check valve connected between the output side of said pump and a first hydraulic line of a high pressure accumulator unit, a second hyd~aulic line of a low pressure accumulator unit, a second check valve connected between said second hydraulic line and the input side of said pump, a first controlled valve connected between said first hydraulic line and said input side of said pump, a secsnd controlled valve connected between said second hydraulic line and said output side of said pump, whereby, in operation, when said movable object is to be slowed down by placing it in a braking mode said first and second controlled valves are controlled by a control unit to be closed and hydraulic :.
., ' ~ ' `'' - , :' ` :,'- ' ` `
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i~37 2 .
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fluid is transferred by said pump from said low pressure accumulator to said high pressure accumulator through said second check valve and said ~irst check valve, and when the movable object is placed in a drive mode and requires a posi-tive traction force said control unit controls said firstand second controlled valves to open and stored hydraulic energy in said high pressure accumulator is transferred via hydrualic fluid through said first controlled valve to the input side of said pump to apply a positive traction force to said movable object, the return path of said hydraulic fluid pump being from its output side through said second controlled valve to said low pressure accumulator unit.
More specifically the pxesent invention provides a mechanical power regeneration system for a bus comprising a 15 sole variable displacement hydraulic pump in the power regen- :
eration system, said sole hydraulic pump being directly geared to the rear wheels of the bus and thus may be positively driven by the drive axle of said bus, a first check valve connected between the output side of said pump and a first hydraulic line of a high pressure accumulator unit, a second hydraulic line of a low pressure accumulator unit, a second check valve connected between said second hydraulic line and the input side of said pump, a first controlled valve connected between said first hydraulic line and said input side of said pump, a second controlled valve connected between said sacond hy-draulic line and said output side of said pump, whereby, in : operation, when the brakes of said bus are applied to placa it in a braking mode said first and second controlled valves are controlled by a control unit to be closed and hydraulic fluid is transferred by said pump from said low pressure accumulator to said high pressure accumulator through said second check valve and said first check valve, and when the bus is placed in a drive mode and requires a positive trac-tion force said control unit controls said first and second controlled valves to open and stored hydraulic energy in said high pressure accumulator is transferred through said :
first controlled valve to the input side of said pump to apply a positive traction force to said rear wheels, the :
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9L28S~38~
return path of said pump being from its output side through said second controlled valve to said low pressure accumulator unit O
DESCRIPTION OF THE DRAWINGS
Figure 1 is a diagrammatic representation of a me i chanical power regeneration system for a rear engined bus, Figure 2 diagrammatically illustrates, in block form, a controller unit with the connection lines to units in Figure 1, and Figure 3 diagrammatically illustrates the controller unit in greater detail.
DESCRIPTION OF SOME EMBODIMENTS
Referring to Figure 1, there is disclosed a mechani-. cal power regeneration system suitable for use with a bus.
The power regeneration system includes only one variable dis-placement hydraulic pump/motor unit 2 which is directly driven from the rear wheels 4 and 6 to be always positively driven thereby when the wheels turn. 'It is to be noted that the pump 2 is connected to the differential unit 8 on the drive axle 2Q lO independently of the engine 12.
The output side of pump 2 is connec~ed through a ; first hydraulic check valve 14 to a first hydraulic line 16 connected to the hydraulic connection of a high pressure : accumulator unit 18.
A second hydraulic line 20 is connected to a low pressure accumulator 22. A second check valve 24 is connect-ed between said second hydraulic line 20 and the input side :~
: of pump 20 In Figure l, a first controlled valve 26 is shown connected between line 16 and the input side of pump 2 whilst a second controlled valve 28 is connected between the output side of pump 2 and the line 20~ ~.
A third check valve 30 is in series with a first controlled relief valve 32 and the series ~rrangement is connected across the output and input sides of said pump 2 with valve 30 arranged to pass fluid when the pressure at -~ the output side of pump 2 is greater than the pressure at : the input side of pump 2 and when said first controlled relief .
-, .,, - . .
.: . :. . .- - .: . .. : -5~7 to the high pressure accumulator unit 18. Every time the brake pedal is actuated, for normal levels of retardation, the hydraulic system comes into operation to retard the vehicle without use of the service brakes. In this condi--tion, the pump 2 recharges the accumulator 180 When the bus is driven normally, in its drive mode, and the bus initially requires a positive traction force then action on the accelerator pedal causes the controller unit 50 (Figure 2) to open valves 26 and 28 whilst maintain-ing valves 32 and 36 closed. Any stored energy in the highpressure accumulator unit 18 is re-applied to the driving wheels 4 and 6, by discharging the high pressure oil through valve 26 to the inlet side of pump 8. The path of the oil is then from the outlet side of pump 2 through the valve 28 to the low pressure accumulator unit 22.
It is to be noted that only one pump 2 and two con-trolled valves 26 and 28 are required for operation of the ~ bus as described above. Valves 32 and 36 are merely relief -~ valves~ Valve 36 is controlled to open when thebus is placed in a reverse mode so as to act as a relief line for the hydraullc pressure produced by pump 2. The path of the oil is from the inlet s~de of pump 2, through relief valve 36, through check - valve 34 back to the output side of pump 2.
SUI~MARY - PRINCIPLES OF OPERATION
~- 25 RUISE MODE (Mo hydraulic brakin~ or tr ction) - Pump 2 - displacement at minimum Engine fuel lever = f (Accelerator pedal positionO3 Valves 26 and 28 open.
BRAKING MODE
. _ ~
- 30 Pump 2 - displacement = f (Brake pedal position, (pressure at gauge 40) Valves 26 and 28 closedO
- Oil is transferred from low pressure accumulator 22 to high pressure accumulator 18, providing retarding force to road wheels via pump 2.
HOLD MODE (Hi~h Pressure accumulator ener~y hold) . . _ Valve 26 closed.
Valve 28 open.
.
- ~: . ., . ~. :
.
.- . , ' ~ :
.
~ ~S~1~7 , to the high pressure accumulator unit 18. Every time the brake pedal is actuated, for normal levels of retardation, the hydraulic system comes into operation to retard the vehicle without use of the service brakes. In this condi-tion, the pump 2 recharges the accumulator 18nWhen the bus is driven normally, in its drive mode, and the bus initially requires a positive traction ~orce ` then action on the accelerator pedal causes the controller unit 50 (Figure 2) to open valves 26 and 28 whilst maintain-- 10 ing valves 32 and 36 closed. Any stored energy in the high pressure accumulator unit 18 is re-applied to the driving wheels 4 and 6, by discharging the high pressure oil through valve 26 to the inlet side of pump 8. The path of the oil is then from the outlet side of pump 2 through the valve 28 - 15 to the low pressure accumulator unit 22.
; It is to be noted that only one pump 2 and two con-trolled valves 26 and 28 are required for operation of the bus as described above. Valves 32 and 36 are merely relief valves. Valve 36 is controlled to open when the~us is placed in a reverse mode so as to act as a relief line for the hydraul~c pressure produced by pump 2. Th~ path of the oil is from the inlet side of pump 2, through relief valve 36, through check valve 34 back to the output side of pump 2.
SUMMARY - PRINCIPL}5S OF OPERATION
25 CRUISE MODE (Mo hydraulic brakinq or traction) Pump 2 - displacement at minimum Engine fuel lever = f ~Accelerator pedal positionO3 Valves 2 6 and 28 open.
BRAKING MODE
Pump 2 - displacement = f (Brake pedal position, (pressure at gauge 40) Valves 26 and 28 closPd.
Oil is transferred from low pressure accumulator 22 to high pressure accumulator 18, providing retarding force to road wheels via pump 2.
HOLD MODE IHi~h pressure accumulator ener~y hold) Valve 26 closed.
Valve 28 open.
: - . .... :: , .
- --.
6~Z8~887 HYDRAULIC TR~CTION
Pump 2 - displacement = f (Accelerator p~dal) Engine fuel lever = f (Accelerator pedal, pressure at gauge 38) Valves 26 and 28 open.
High pressure oil in accumulator 18 discharges to accumulator 22 via pump 2, providlng a tractive force to the road wheels.
On exhaustion of high pressure accumulator charge, lQ pump 2 displacement is set to minimum giving the CRUISE mode above.-REVERSE
Valve 26 is closed. Valve 28 is open.
Relief valve 36 is open.
High pressure accumulator charge is held.
- Oil transfer from pump is recirculated.
A significant finding we made was that the thermo-dynamically ideal accumulator (that which provides a given energy storage capacity at the minimum gas volume), does not provide the optimum perfo`rmance, considering overall energy conservation, over the range of real driving situations.
~- The performance analyses presented here have per-mitted the design parameters for a prototype vehicle to be optimised to significant advantage.
PUMP SIZE AND OE ARING
In practice, it is necessary to speed up the pump drive in order to obtain adequate energy conversion rates using any of the currently available sizes of hydraulic pumpsO
In predicting the retardation, it is necessary to relate the hydraulic pressure, to the retarding tractive effort.
Pump power PP = DP.dP(Np/60) kW (1) where Np = VEL.RR.DR/RS revs/min. (2) ; Tractive force TF = PP/VEL.3600 N (3) = DPodP(VEL.RR.DR/RS/60).(3600/VEL) N (4) ; where:
`'-' : . . , . , -~28~
Sy~bol Description Unit dP = Pump differential pressure MPa DP - Pump Displacement/revolution DR = Pump gearbox speedup ratio LOP = Lower Operating Pressure MPa Np = Pump speed revs/min PP = Pump Power kW
RR = Driveshaft speed at RSrevs/min RS = Vehicle Road Speed or RR km/h lO SPD = Specific Pump Displacement Q/m travel TF = Tractive Force N
VEL = Vehicle velocity km/h Eq. (4) can usefully be simplified by introducing the concept of Specific Pump Displacement, which may be de-fined as the volumetric displacement of the hydraulic pump per unit of linear vehicle travel.
i.e. Spècific Pump Displacement SPD = DP.DR.RR/RS.60/lOOO /m (5) giving TF = SPD.dP.lO N (6) R. Sandri and W.S. Heggie, in "Heat Transfer and Energy Storage in Pneumatic Accumulators"~ International Symposium, Advanced and Hybrid Vehicles, University of Strath-- clyde, September 1984, have shown the fundamental gas charac-25 teristics of the pressure range of interest 20-3709 MPa (3-5000 psi). From this, the gas volume and pressure limits re-quired for the storage of a given quantity of energy can be determined. There is an optimum LOP of approximately 10.4 MPa (1530 psi).
It should be noted that the relationship between the specific energy storage and the LOP is a general relation-ship, whereas the relationship between the actual gas volume and the LOP is depen-dent on the quantity of energy to be stored.
In either case, the actual values are affected by the pressure in the low pressure accumulator over the cycle.
The most obvious advantage obtained by raising the LOP, is the corresponding increase in tractive effort obtained in accordance with Eq. l6). There will however be a severe ..... . . . . . . .
- .
. . , - . . . -, - .. : . - , . - ~ ~ - . , . : .. .
~X8S~37 reduction in energy s~orage capacity i~ the LOP is increased much above 20 MPa (3000 psi).
- HYDRO-PNEUMATIC ENERGY STORAGE CHARACTERISTICS
There are two characteristics of special note, related to the fact that as the magnitude o~ the stored ener-gy is increased within a given accumulator, there is a simultaneous reduetion in gas volume and increase in pressureO
Firstly, the quantity of energy stored at any in-stant is dep~ndent on the volume displaced by the oil. This corresponds to the distance travelled during stopping, assum-ing a constant pump displacement. Secondly, as the gas pres-sure increases as a power function of the-volume reduction, the hydraulic oil pressure, (equalling the gas pressure), will give rise to a tractive retarding force also increasing as a power function of the distance travelled during the retarda-tion, with the same pump displacement.
REQUIRED SYSTEM PERFORMANCE
Little information was available concerning the actual braking cycles involved in typical city bus routes.
Therefore some data was collected from a bus travelling along a 6 mile radial route between a city and its suburb. It was found that the majority of the stops occurred at an average retardation rate not exceeding 1.68 m/s ~5.5 ft/sec); and - that the majority of the stops occurred in the 32 to 48 km/h (20 to 30 mph) range. The following performance targets for the energy recovery system were derived from this data:-1. The system should be able to fuliy store the available kinetic energy for a 48 km/h (30 mph) stop~
2. The system should be capable o~ providing an average retardation rate of 1.68 m/s (5.5 ft/sec) for a stop from 32 km/h (20 mph).
Due to the gas compression characteristics mentioned above, this target implies that the 48 km/h (30 mph) stop, would exceed the 1.68 m/s (5.5 ft/sec ) limit at the same pump displacement-In the test bus, ~ree piston cylindrical accumulators --- . ' .
`
.
- . ,: . ~, , . - : . : . , . -. . .
~ . - : . - . . . . - :
~28S887 units were usedO With the bladder type accumulator, parti-cularly when mounted in the horizontal position, the bag tends to take an off-centre attitude, resulting in an oil velocity differential between opposite sides, tendin~ to further draw the bag to the lower velocity side. This can cause fluttering resulting in bag damage and pressure fluctuation.
A bent axis multiple co-axial piston was used as a pump/motor 2 because it displays several advantages over swash-plate devices, including better overall efficiency especially at low displacement.
Pilot opPrated check valves wére used where 100~
shut off is important and also to simplify valve sequencing operationsO
In the block schematic of the controller unit 50 in Figure 2, the inputs to the controller unit are from the accelerator pedal o~ the bus and the brake pedal via appro-priate rheostats as shown in greater detail in Figure 3.
An input is also obtained from the gear selector of the bus to indicate when gear is in reverse (R~, drive (D) or neutral ; 20 (N)o The outputs of controller unit S0 go to valve 26, 28, 36 and to engine 12 (Figure 1). A connection is also ; shown in relation to the Hydraulic Pump displacement.
The Controller unit is shown in greater de~ail in Figure 3. The nomenclature used will be clear from Figure 3 and is standard to that used by persons skilled in the art. Certain graphical representations are included for clarity.
The processor used on the bus was a custom designed unit based on a single board microcomputer utilizing an 8086 CPU. The system was designed to act as both a system controller and data ac~uisition system. The control program and test data were stored on a removable bubble memory.
Re~erring to Figure 3, driver input is provided by a modified gear shi~t and potentiometers 52 and 54 operated - by the accelerator (Ap) and the brake pedal (Bp). Five out~
; puts control the three valves 26, 28 and 36, the fuel rack (Ra) and the pump/motor displacement (D2).
, .- ' . : ., . .: :
'. ', ~ ~ ' ~ - . -- . ~ ' ' . ' , :.
-- 10 -- , ~8S88~
Functions Fl and F2 modify the output of the con-troller 50 to the fuel rack, melding engine with accumulator power to provide a repeatable response to the accelerator (Ap) regardless o~ the state of charge of the high pressure accumulator 18 as indicated by gauge 38 ~Figure 1).
The double switch (SW) disables displacement con-trol (D2) of the pump/motor unit 2 of Figure 1 and pro~ides fuel rack control as a direct function of the accelerator potentiometer 52 when reverse or neutral modes are selected.
The same is true when operating with the high pressure accumu-lator 18 fully discharged.
In Figure 3, F3 is used to attenuate pump displace-ment when the accumulator is fully charged to limit thermal -build up at the relief valve. F4 and F5 provide modulation of the hydraulic tractive effort during acceleration and braking respec~ively.
Function F7 backs off Pump/Motor displacement as a function of speed to comply with speed load restrictions.
Function F6 acts similarly to F'7 except that it is based on inlet pressure as an anti-cavitation protection.
The latter two functions were devised in order to design safely for the maximum ratings o~ the hydraulic trans-mission system~ The alternative, of course, would be a larger unit or gearing down the speed with a consequent loss of performance.
In Figure 3 the setting of the movable arm of poten-tiometer 52 is dependent on the position othe accelerator pedal of the bus. The setting determines the magnitude of input signal ~AP) provided to the microcomputer unit. Simi-larly, the setting of the movable arm of potentiometer 54determines the magnitude of the input signal (BP) provided to a second input of the microcomputer unit. The microcom- -puter unit is designed to analyse its inputs and to pro~ide . corresponding control signals to the controlled valves 26 and 28 (Figure 1).
The microcomputer is also responsive to the gear - lever of the bus being placed in reverse. A further control -- signal is then provided to controlled relief valve 36 (Figure 1) whereby the hydraulic fluid from the pump 2 is recirculated - . . . ~: ,- . . ......... ' ... :' . - . . . ' ., ~
: .
128S8~3~
through the controlled relief valve 36 and check valve 34.
There has been described, a system designed to regenerate mechanical energy, being separate and distinct from the primary power transmission which connects a prime mover (iOe. internal or external combustion engine, electxic motor etc.) to its load; the system comprising:-variable displacement hydraulic unit which may function as either a pump or a motor, and which is directly coupled to the load; a high pressure, hydro-pneumatic accumulator or energy storage; a low pressure hydro-pneumatic accumulator, to serve as a reservoir of oil of adequate pressure to satis-fy the requirements of the pump/motor unit, an energy storage sensor,, which provides a measure of the energy level in the energy storage unit, for use by regenerative power control system, and a control system which controls the prime mover power level, the power regenerator power level, and the active control valves, using as operator inputs, only such convention-al controls as accelerator and brake pedals, and primary trans-mission control inputs.
Two active controllable valves determine the control mode of the regenerative power system. The power regenerator may be separable from the load by means of a mechanical clutch, under automatic control. The prime mover may be disconnected from the load, under automatic control. The regenerative power controller may generate a control demand on the primary power trans~ission, for the selection of a drive ratio.
The power regenerator and the energy storage devices may, of course, be electrical.
It will be readily apparent to a person skilled in the art that a number of variations and modiications can be made without, departing ~rom the true spirit of the inven-tion which will now be pointed out in the appended claims.
, .
.
-- . .
. .
Claims (4)
1. A mechanical power regeneration system for a movable object having a primary power transmission connecting a prime mover to a load, said system being separate and distinct from the primary power transmission, comprising:
(a) a variable displacement hydraulic pump assembly including a pump in the power regeneration system, (b) said hydraulic pump being positively driven by the movable object in at least one operational mode of said movable object, (c) a first check valve connected between the output side of said pump and a first hydraulic line of a high pressure accumulator unit, (d) a second hydraulic line of a low pressure accumulator unit, (e) a second check valve connected between said second hydraulic line and the input side of said pump, (f) a first controlled valve connected between said first hydraulic line and said input side of said pump, (g) a second controlled valve connected between said second hydraulic line and said output side of said pump, (h) whereby, in operation, when said movable object is to be slowed down by placing it in a braking mode said first and second controlled valves are controlled by a controller unit to be closed and hydraulic fluid is transferred by said pump from said low pressure accumulator to said high pressure accumulator through said second check valve and said first check valve, and (i) when the movable object is placed in a drive mode and requires a positive traction force said controller unit controls said first and second controlled valves to open and stored hydraulic energy in said high pressure accumulator is transferred via hydraulic fluid through said first controlled valve to the input side of said pump to apply a positive traction force to said movable object, the return path of said hydraulic fluid pump being from its output side through said second controlled valve to said low pressure accumulator unit.
(a) a variable displacement hydraulic pump assembly including a pump in the power regeneration system, (b) said hydraulic pump being positively driven by the movable object in at least one operational mode of said movable object, (c) a first check valve connected between the output side of said pump and a first hydraulic line of a high pressure accumulator unit, (d) a second hydraulic line of a low pressure accumulator unit, (e) a second check valve connected between said second hydraulic line and the input side of said pump, (f) a first controlled valve connected between said first hydraulic line and said input side of said pump, (g) a second controlled valve connected between said second hydraulic line and said output side of said pump, (h) whereby, in operation, when said movable object is to be slowed down by placing it in a braking mode said first and second controlled valves are controlled by a controller unit to be closed and hydraulic fluid is transferred by said pump from said low pressure accumulator to said high pressure accumulator through said second check valve and said first check valve, and (i) when the movable object is placed in a drive mode and requires a positive traction force said controller unit controls said first and second controlled valves to open and stored hydraulic energy in said high pressure accumulator is transferred via hydraulic fluid through said first controlled valve to the input side of said pump to apply a positive traction force to said movable object, the return path of said hydraulic fluid pump being from its output side through said second controlled valve to said low pressure accumulator unit.
2. A mechanical power regeneration system for a vehicle having a primary power transmission connecting a prime mover to a load, said system being separate and distinct from the primary power transmission, comprising:
(a) a variable displacement hydraulic pump assembly including a pump in the power regeneration system, (b) said hydraulic pump being directly driven from the wheels of the vehicle in at least one operational mode of said vehicle, (c) a first check valve connected between the output side of said pump and a first hydraulic line of a high pressure accumulator unit, (d) a second hydraulic line of a low pressure accumulator unit, (e) a second check valve connected between said second hydraulic line and the input side of said pump, (f) a first controlled valve connected between said first hydraulic line and said input side of said pump, (g) a second controlled valve connected between said second hydraulic line and said output side of said pump, (h) whereby, in operation, when the brakes of said vehicle are applied to place it in a braking mode said first and second controlled valves are controlled by a controller unit to be closed and hydraulic fluid is transferred by said pump from said low pressure accumulator to said high pressure accumulator through said second check valve and said first check valve, and (i) when the vehicle is placed in a drive mode and requires a positive traction force said controller unit controls said first and second controlled valves to open and stored hydraulic energy in said high pressure accumulator is transferred through said first controlled valve to the input side of said pump to apply a positive traction force to said wheels, the return path of said pump being from its output side through said second controlled valve to said low pressure accumulator unit.
(a) a variable displacement hydraulic pump assembly including a pump in the power regeneration system, (b) said hydraulic pump being directly driven from the wheels of the vehicle in at least one operational mode of said vehicle, (c) a first check valve connected between the output side of said pump and a first hydraulic line of a high pressure accumulator unit, (d) a second hydraulic line of a low pressure accumulator unit, (e) a second check valve connected between said second hydraulic line and the input side of said pump, (f) a first controlled valve connected between said first hydraulic line and said input side of said pump, (g) a second controlled valve connected between said second hydraulic line and said output side of said pump, (h) whereby, in operation, when the brakes of said vehicle are applied to place it in a braking mode said first and second controlled valves are controlled by a controller unit to be closed and hydraulic fluid is transferred by said pump from said low pressure accumulator to said high pressure accumulator through said second check valve and said first check valve, and (i) when the vehicle is placed in a drive mode and requires a positive traction force said controller unit controls said first and second controlled valves to open and stored hydraulic energy in said high pressure accumulator is transferred through said first controlled valve to the input side of said pump to apply a positive traction force to said wheels, the return path of said pump being from its output side through said second controlled valve to said low pressure accumulator unit.
3. A mechanical power regeneration system according to claim 2 wherein:
(a) a first potentiometer is provided having a movable arm responsive to the position of an accelerator pedal of the vehicle to provide a first input to a microcomputer unit, (b) a second potentiometer is provided having a movable arm responsive to the position of a brake pedal of the vehicle to provide a second input to said microcomputer unit, and (c) said microcomputer unit providing corresponding control signals to said first and second controlled valves.
(a) a first potentiometer is provided having a movable arm responsive to the position of an accelerator pedal of the vehicle to provide a first input to a microcomputer unit, (b) a second potentiometer is provided having a movable arm responsive to the position of a brake pedal of the vehicle to provide a second input to said microcomputer unit, and (c) said microcomputer unit providing corresponding control signals to said first and second controlled valves.
4. A mechanical power regeneration system for a movable object having a primary power transmission connecting a prime mover to a load, said system being separate and distinct from the primary power transmission, comprising:
(a) a variable displacement hydraulic pump assembly including a pump in the power regeneration system, (b) said hydraulic pump being positively driven by the movable object in at least one operational mode of said movable object, (c) a first check valve connected between the output side of said pump and a first hydraulic line of a high pressure accumulator unit, (d) a second hydraulic line of a low pressure accumulator unit, (e) a second check valve connected between said second hydraulic line and the input side of said pump, (f) a first controlled valve connected between said first hydraulic line and said input side of said pump, (g) a second controlled valve connected between said second hydraulic line and said output side of said pump, (h) whereby, in operation, when said movable object is to be slowed down by placing it in a braking mode said first and second controlled valves are controlled by a controller unit to be closed and hydraulic fluid is transferred by said pump from said low pressure accumulator to said high pressure accumulator through said second check valve and said first check valve, and (i) when the movable object is placed in a drive mode and requires a positive traction force said controller unit controls said first and second controlled valves to open and stored hydraulic energy in said high pressure accumulator is transferred via hydraulic fluid through said first controlled valve to the input side of said pump to apply a positive traction force to said movable object, the return path of said hydraulic fluid pump being from its output side through said second controlled valve to said low pressure accumulator unit, (j) a third check valve connected in series with a controlled relief valve across the input and output sides of said pump, and (k) said microcomputer unit providing a control signal to said controlled relief valve when the movable object is in a reverse mode whereby when the movable object is reversed, hydraulic fluid is recirculated around the pump through said controlled relief valve.
(a) a variable displacement hydraulic pump assembly including a pump in the power regeneration system, (b) said hydraulic pump being positively driven by the movable object in at least one operational mode of said movable object, (c) a first check valve connected between the output side of said pump and a first hydraulic line of a high pressure accumulator unit, (d) a second hydraulic line of a low pressure accumulator unit, (e) a second check valve connected between said second hydraulic line and the input side of said pump, (f) a first controlled valve connected between said first hydraulic line and said input side of said pump, (g) a second controlled valve connected between said second hydraulic line and said output side of said pump, (h) whereby, in operation, when said movable object is to be slowed down by placing it in a braking mode said first and second controlled valves are controlled by a controller unit to be closed and hydraulic fluid is transferred by said pump from said low pressure accumulator to said high pressure accumulator through said second check valve and said first check valve, and (i) when the movable object is placed in a drive mode and requires a positive traction force said controller unit controls said first and second controlled valves to open and stored hydraulic energy in said high pressure accumulator is transferred via hydraulic fluid through said first controlled valve to the input side of said pump to apply a positive traction force to said movable object, the return path of said hydraulic fluid pump being from its output side through said second controlled valve to said low pressure accumulator unit, (j) a third check valve connected in series with a controlled relief valve across the input and output sides of said pump, and (k) said microcomputer unit providing a control signal to said controlled relief valve when the movable object is in a reverse mode whereby when the movable object is reversed, hydraulic fluid is recirculated around the pump through said controlled relief valve.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000525478A CA1285887C (en) | 1986-12-16 | 1986-12-16 | Mechanical power regeneration system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000525478A CA1285887C (en) | 1986-12-16 | 1986-12-16 | Mechanical power regeneration system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1285887C true CA1285887C (en) | 1991-07-09 |
Family
ID=4134567
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000525478A Expired - Lifetime CA1285887C (en) | 1986-12-16 | 1986-12-16 | Mechanical power regeneration system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1285887C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107458387A (en) * | 2017-08-11 | 2017-12-12 | 四川省机械研究设计院 | Hydraulic pressure for electro-hydraulic railcar aids in acceleration system |
-
1986
- 1986-12-16 CA CA000525478A patent/CA1285887C/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107458387A (en) * | 2017-08-11 | 2017-12-12 | 四川省机械研究设计院 | Hydraulic pressure for electro-hydraulic railcar aids in acceleration system |
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