Hybrid powertrain vehicle

• US 5,495,912 A
• Filed: 06/03/1994
• Issued: 03/05/1996
• Est. Priority Date: 06/03/1994
• Status: Expired due to Term

• Current Assignee: Government of The United States of America, As Represented By The Administrator of The United States Environmental Protection Agency
• Original Assignee: United States Environmental Protection Agency
• Inventors: Safoutin, Michael J., Gray, Charles L. Jr., Hellman, Karl H.
• Primary Examiner(s): Camby, Richard M.
• Application Number:
  US08/253,944
• Time in Patent Office: 641 Days
• Field of Search: 180/165, 180/305, 180/306, 180/307, 180/308, 180/65.1, 180/65.2, 180/65.3, 180/65.4, 60/413, 60/414, 60/418, 60/420, 364/424.1, 364/426.01, 74/665 A, 74/665 B
• US Class Current: 180/165
• CPC Class Codes: B60K 6/12 by means of a chargeable fluidic accumulator
• CPC Class Codes: B60T 1/10 by utilising wheel movement for accumulating energy, e.g. driving air compressors
• CPC Class Codes: Y02T 10/62 Hybrid vehicles

Abstract

Engine output speed is controlled for optimum efficiency by adjustment of input speed of a continuously variable transmission (CVT). Where power in excess of that provided by the engine is required, additional power is input to the drivetrain from a fluidic motor driven by fluid pressure stored in an accumulator. In driving conditions where the engine, operating at optimum efficiency, produces power in excess of that demanded by of the vehicle, the fluidic motor is reversed for operation as a pump and excess engine power is utilized to drive the pump and store energy in the accumulator in the form of fluid pressure. A CPU determines power output required of the engine as a sum of that indicated by a sensor which senses power demanded of the vehicle by a driver and an increment of power required to maintain the pressure of the accumulator above a threshold amount. An engine speed controller controls the rotary speed of the engine output, to produce the required total power output, by changing the input speed of the CVT. In order to maintain optimum engine efficiency, a memory associated with the CPU is stored with maps correlating values for optimum engine speed with values for engine output power and the optimum engine speed is read from the map by reference to the determined total requirement for engine output power. Optionally, the vehicle may include first and second engines with the second engine providing a power assist under driving conditions demanding power in excess of that available from the primary engine in combination with the fluidic motor. The invention also includes a method of operating the system in order to achieve the objective of optimum engine efficiency.

Claims

1. A hybrid powertrain vehicle comprising:

a vehicle frame;

drive wheels rotatably mounted on said vehicle frame;

a primary engine, mounted on said vehicle frame, for providing engine power by rotation of an output shaft;

power storage means, mounted on said vehicle frame, for storing and releasing power generated by said primary engine;

first drive train means for transmitting said engine power to said drive wheels, said first drive train means including a transmission having adjustable speed input and output;

reversible means for selectively, while driven by said rotation of said engine in a first mode, transmitting said engine power to said power storage means or, operating as a motor in a second mode, transmitting stored power from said power storage means to said first drive train;

second drive train means, in parallel with at least a portion of said first drive train means, connecting said reversible means to said first drive train means, for, in said second mode, transmitting said stored power to said first drive train means and for, in said first mode, transmitting said rotation of said engine to said reversible means for transfer of a portion of said engine power to said power storage means simultaneously with transfer of the remainder of said engine power to said drive wheels;

vehicle speed sensor means for sensing vehicle speed;

stored power sensor means for sensing a quantity of power stored within said power storage means;

power demand sensing means for sensing power demanded of the vehicle by a driver;

comparing means for comparing said sensed quantity of stored power with a predetermined minimum amount of stored power and generating a demand signal upon determination that said sensed quantity is below said predetermined amount;

power output determining means for determining an additional increment of power in accordance with said demand signal and for determining an engine output power as a sum of the sensed power demand and the additional increment of power;

engine speed control means for controlling speed of said rotation of said output shaft by changing the input speed of said transmission responsive to a transmission signal;

engine speed determining means for determining an engine speed of optimum efficiency in accordance with said determined engine output power and said sensed vehicle speed and for outputting the transmission signal, indicative of the determined engine speed, to said engine speed control means;

engine load control means for controlling said engine power by controlling fuel feed to said primary engine responsive to said transmission signal; and

mode control means for converting operation of said reversible means between said first and second modes responsive to the demand signal.

2. A hybrid powertrain vehicle according to claim 1 further comprising:

a secondary engine;

a secondary engine clutch for connecting an output of said secondary engine to said first drive means responsive to the sensed power demand.

3. A hybrid powertrain vehicle according to claim 2, wherein said comparing means compares the sensed power demand with a maximum power predetermined for said primary engine and generates a command signal for starting said secondary engine and for engaging said secondary engine clutch when said sensed power demand exceeds said predetermined maximum power.

4. A hybrid powertrain vehicle according to claim 3, wherein said command signal is generated only upon determination that said sensed quantity of stored power is below said predetermined amount.

5. A hybrid powertrain vehicle according to claim 1 further comprising a freewheel clutch interposed between said transmission and said drive wheels for disengaging said drive wheels from said first drive train responsive to a signal indicative of zero sensed power demand.

6. A hybrid powertrain vehicle according to claim 1 further comprising a memory containing a stored map correlating values for said optimum engine speed and engine output power;

and wherein

said engine speed determining means applies said determined engine output power and said sensed vehicle speed to said map to determine the engine speed of optimum efficiency.

7. A method for controlling a vehicle equipped with the hybrid powertrain propulsion system including drive wheels, reversible drive means, a primary engine for rotatable driving said drive wheels and said reversible drive means simultaneously in parallel, power storage means for storing engine power generated by said primary engine, a transmission having adjustable speed input and speed output and engine speed control means for changing the input speed of said transmission, said method comprising:

sensing vehicle speed;

sensing a quantity of power stored within the power storage means;

sensing power demanded of the vehicle by a driver;

feeding power from the power storage means, through the reversible drive means, utilizing the reversible drive means as a motor for driving said drive wheels responsive to a signal indicating a demanded power above that output by the primary engine;

simultaneously (1) transmitting a portion of the output power of the primary engine into said power storage means, using said reversible drive means, responsive to a sensed quantity of stored power lower than a predetermined value and (2) transmitting the remainder of the output power of the primary engine to the drive wheels;

comparing the sensed quantity of stored power with a predetermined minimum value and generating a demand signal upon determining that the sensed quantity of stored power is below the predetermined low value;

determining an additional output power in accordance with the demand signal and determining an engine output power as the sum of the sensed power demand and the additional output power;

controlling the rotary speed of the primary engine by changing the input speed of the transmission responsive to a transmission signal; and

determining an engine speed of optimum efficiency in accordance with the determined engine output power and the sensed vehicle speed and outputting the transmission signal in accordance with the determined engine speed.

8. The method of claim 7 wherein said propulsion system includes a memory containing a stored first map correlating values for optimum engine speed and determined engine output power, and a second map correlating values for vehicle speed and said transmission signals, each of said transmission speeds representing a transmission speed (gear) ratio to achieve optimum engine speed;

and wherein

said determining of optimum engine speed is by applying the determined engine output power and a sensed vehicle speed to said maps to select an engine speed of optimum efficiency for said determined engine output power and said sensed vehicle speed and for setting said transmission signal.

9. A hybrid powertrain vehicle comprising:

a vehicle frame;

drive wheels rotatably mounted on said vehicle frame;

a primary engine, mounted on said vehicle frame, for providing engine power as rotation of an output shaft;

a fluid pressure accumulator, mounted on said vehicle frame, for storing and releasing fluid pressure;

first drive train means for transmitting said engine power to said drive wheels, said first drive train means including a continuously variable transmission having at least one pulley of variable effective diameter;

reversible fluidic displacement means for, in a first mode, operating as a motor fluidically driven by fluid pressure released by said accumulator, to output motor power to said first drive train and for, in a second mode, operating as a pump driven by said rotation of said engine, through said first drive train, to store said fluid pressure;

second drive train means, connecting said fluidic displacement means to said first drive train means, for, in said first mode, transmitting said motor power to said first drive train means and for, in said second mode, transmitting engine power to said fluidic displacement means;

vehicle speed sensor means for sensing vehicle speed;

pressure sensor means for sensing the fluid pressure within said accumulator;

power demand sensing means for sensing power demanded of the vehicle by a driver;

comparing means for comparing said sensed fluid pressure with a predetermined minimum fluid pressure and generating a demand signal upon determination that said sensed fluid pressure is below said predetermined fluid pressure;

power output determining means for determining an additional increment of power in accordance with said demand signal and for determining an engine output power as a sum of the sensed power demand and the additional increment of power;

engine speed control means for controlling rotary speed of said output shaft by changing the effective diameter of said pulley responsive to a transmission signal;

engine speed determining means for determining an engine speed of optimum efficiency in accordance with said determined engine output power and said sensed vehicle speed and for outputting the transmission signal, indicative of the determined engine speed, to said engine speed control means;

engine load control means for controlling said engine power by controlling fuel feed to said primary engine responsive to said transmission signal; and

mode control means for converting operation of said fluidic displacement means between said first and second modes responsive to the demand signal and for varying the displacement of said fluidic displacement means responsive to the sensed fluid pressure.

10. A hybrid powertrain vehicle according to claim 9 further comprising:

a secondary engine;

a secondary engine clutch for connecting an output of said secondary engine to said first drive means responsive to the sensed power demand.

11. A hybrid powertrain vehicle according to claim 10, wherein said comparing means compares the sensed power demand with a maximum power predetermined for said primary engine and generates a command signal for starting said secondary engine and for engaging said secondary engine clutch when said sensed power demand exceeds said predetermined maximum power.

12. A hybrid powertrain vehicle according to claim 11, wherein said command signal is generated only upon determination that said sensed fluid pressure is below said predetermined fluid pressure.

13. A hybrid powertrain vehicle according to claim 9 further comprising a freewheel clutch interposed between said transmission and said drive wheels for disengaging said drive wheels from said first drive train responsive to a signal indicative of zero sensed power demand.

14. A hybrid powertrain vehicle according to claim 9 further comprising a memory containing a stored map correlating values for said optimum engine speed and engine output power;

and wherein

said engine speed determining means applies said determined engine output power and said sensed vehicle speed to said map to determine the engine speed of optimum efficiency.

15. A method for controlling a vehicle equipped with the hybrid powertrain propulsion system including drive wheels, a primary engine for powering the drive wheels, a reversible fluidic displacement means, an accumulator for accumulating fluid pressure, a continuously variable transmission having a moveable pulley of variable effective diameter and a controller for mechanically moving that pulley to change the effective diameter, said method comprising:

sensing vehicle speed;

sensing fluid pressure within the accumulator;

sensing power demanded of the vehicle by a driver;

feeding fluid pressure from the accumulator, through the reversible fluid displacement device, to utilize the reversible fluid displacement device as a motor for driving said drive wheels responsive to a signal indicating a demanded power above that output by the primary engine;

pumping fluid pressure into the accumulator, using a portion of the output power of the primary engine to drive the reversible fluid displacement means as a pump, responsive to a sensed fluid pressure lower than a predetermined value;

comparing the sensed fluid pressure with a predetermined minimum fluid pressure and generating a demand signal upon determining that the sensed fluid pressure is below the predetermined low fluid pressure;

determining an additional output power in accordance with the demand signal and determining an engine output power as the sum of the sensed power demand and the additional output power;

controlling the rotary speed of the primary engine by changing the effective diameter of the moveable pulley responsive to a transmission signal; and

determining an engine speed of optimum efficiency in accordance with the determined engine output power and the sensed vehicle speed and outputting the transmission signal in accordance with the determined engine speed.

16. The method of claim 15 wherein said propulsion system includes a memory containing a stored first map correlating values for optimum engine speed and determined engine output power, and a second map correlating values for vehicle speed and said transmission signals, each of said transmission speeds representing a transmission speed (gear) ratio to achieve optimum engine speed;

and wherein

said determining of optimum engine speed is by applying the determined engine output power and a sensed vehicle speed to said maps to select an engine speed of optimum efficiency for said determined engine output power and said sensed vehicle speed and for setting said transmission signal.