Abstract:
An interface for interfacing an accelerator control input, a service brake control input, and a parking brake control input with a hybrid electric vehicle&#39;s electric control system that controls propulsion of the vehicle by controlling the motor torque output of an electric traction drive motor that drives driven wheels of the vehicle. The application of either the service brakes or the parking brake concurrent with the accelerator pedal being at non-idle causes the interface to override the motor torque being requested by the accelerator control input in favor of a zero motor torque request to the control system.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to wheeled automotive vehicles of the type in which torque that propels the vehicle is applied to driven wheels through a drivetrain from an on-board electric motor that is itself powered selectively, either by an on-board internal combustion engine driving an on-board electric generator, or by an on-board D.C. power supply, such as a compliment of D.C. batteries for example. A vehicle of this type is sometimes referred to as a hybrid electric vehicle, or HEV. More particularly the invention relates to an interface for interfacing an accelerator control input, a service brake control input, and a parking brake control input with an HEV electric control system that controls propulsion of the vehicle by controlling the motor torque output of the electric motor. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     A representative, electric-powered, wheeled, automotive vehicle has an on-board electric motor whose motor torque output provides torque input to a drivetrain that includes driven wheels supporting the vehicle on a surface along which the vehicle travels. A known electric power source for the motor comprises an on-board compliment of D.C. batteries. The drivetrain delivers the torque to the driven wheels, thereby propelling the vehicle along the underlying surface. 
     A representative, engine-powered, wheeled, automotive vehicle has an internal combustion engine that provides torque input to the drivetrain, and that torque is transmitted through the drivetrain to the driven wheels that propel the vehicle. 
     An HEV is like an electric-powered vehicle in that torque output of an electric motor provides torque input to the drivetrain. It differs however in that it has an alternative power source for the electric motor, that is additional to an on-board compliment of D.C. batteries. That alternative power source comprises an internal combustion engine that drives an electric generator. As the engine runs, it operates the electric generator, and in turn, the generator delivers electricity to run the electric motor. 
     An HEV also has an electric control system that may include distinct, but inter-related, sub-systems for controlling operation of the electric motor, operation of the internal combustion engine, operation of the electric generator, and re-charging of the D.C. batteries. The control allows the options of operating the vehicle by use of D.C. battery power, or of operating the vehicle by running the engine to operate the electric generator. The engine may also operate the electric generator to re-charge the batteries. 
     A suitable electric motor is a traction motor. The electric motor may be a D.C. motor or an A.C. one. Likewise, for the generator. Depending on particular choices for the motor and generator, the electric control may include rectifiers and/or inverters for converting one form of electric power into the other. 
     An HEV may be similar to an internal-combustion-engine-powered automotive vehicle in having like control inputs available to the vehicle driver, including an accelerator control input, a service brake control input, and a parking brake control input, each of which can be operated by the driver independently of the others. Each control input includes an actuator such as a hand-operated pull or lever, or a foot-operated pedal. For example, depressing an accelerator pedal from an idle position accelerates the vehicle, depressing a service brake pedal applies the service brakes, and depressing a parking brake pedal, or pulling a parking brake handle, applies a parking brake. 
     The service brakes are typically fluid-power-operated, with each wheel having its own brake mechanism. The parking brake may be a mechanical, non-fluid-operated mechanism, or mechanisms, proximate a portion, or portions, of the drivetrain. Because of the independent operability of each of the three control inputs, it is possible that either one of the brakes may be applied while the accelerator pedal is being depressed. 
     “Two-toed” operation of the service brake pedal and the accelerator pedal may potentially damage, and/or shorten the life of, involved components. Applying the parking brake while the accelerator pedal is depressed would be considered undesirable for similar reasons. Having the accelerator pedal depressed as the parking brake is being released would also be considered undesirable. 
     In one respect, the present invention is directed to solutions for avoiding potential problems due to simultaneous operation of an accelerator and a brake in an HEV. 
     One general aspect of the invention relates to an automotive vehicle comprising: a drivetrain, including wheels for supporting the vehicle on a surface along which the vehicle is propelled; an on-board electric motor that, when operated, delivers torque output through the drivetrain to driven ones of the wheels for propelling the vehicle along such a surface; an on-board internal combustion engine; an on-board electric generator; an on-board D.C. power supply; an electric control system for controlling the electric motor, including the application of electric power input to the electric motor selectively from the generator and from the D.C. power supply respectively; an accelerator control input for requesting motor torque output from the electric motor; a service brake control input for selectively applying a service brake associated with one or more of the wheels; a parking brake control input for selectively applying a parking brake associated with the drivetrain; and an interface for interfacing the accelerator control input, the service brake control input, and the parking brake control input with the electric control system to control propulsion of the vehicle. The interface comprises a service brake interface portion for detecting application of the service brake by the service brake control input, a parking brake interface portion for detecting application of the parking brake by the parking brake control input, and an interface output portion for causing the electric control to operate the electric motor such that no motor torque output is delivered through the drivetrain from the motor when either brake interface portion detects application of the respective brake by the respective brake control input. 
     Another general aspect of the invention relates to an automotive vehicle comprising: a drivetrain, including wheels for supporting the vehicle on a surface along which the vehicle is propelled; an on-board electric motor that, when operated, delivers torque output through the drivetrain to driven ones of the wheels for propelling the vehicle along such a surface; an on-board internal combustion engine; an on-board electric generator; an on-board D.C. power supply; an electric control system for controlling the electric motor, including the application of electric power input to the electric motor selectively from the generator and from the D.C. power supply respectively; an accelerator control input for requesting motor torque output from the electric motor; a brake control input for selectively applying a brake associated with the drivetrain; and an interface for interfacing the accelerator control input and the brake control input with the electric control system to control propulsion of the vehicle. The interface comprises a brake interface portion for detecting application of the brake by the brake control input and an interface output portion for causing the electric control to operate the electric motor such that when the brake interface portion detects application of the brake by the brake control input, the motor torque output is rendered insufficient to cause propulsion of the vehicle along the surface. 
     Still another general aspect of the invention relates to a method of operating an automotive vehicle that has: a drivetrain, including wheels for supporting the vehicle on a surface along which the vehicle is propelled; an on-board electric motor that, when operated, delivers torque output through the drivetrain to driven ones of the wheels for propelling the vehicle along such a surface; an on-board internal combustion engine; an on-board electric generator; an on-board D.C. power supply; an electric control system for controlling the electric motor, including the application of electric power input to the electric motor selectively from the generator and from the D.C. power supply respectively; an accelerator control input for requesting motor torque output from the electric motor; a brake control input for selectively applying a brake associated with the drivetrain; and an interface for interfacing the accelerator control input and the brake control input with the electric control system to control propulsion of the vehicle, the interface comprising a brake interface portion for detecting application of the brake by the brake control input, and an interface output portion. The method comprises causing the electric control to operate the electric motor such that when the brake interface portion detects application of the brake by the brake control input, the motor torque output is rendered insufficient to cause propulsion of the vehicle along the surface. 
     More specific aspects of the invention will been set forth in the ensuing description, claims, and accompanying drawings. 
     The drawings, which will now be briefly described, are incorporated herein to illustrate a preferred embodiment of the invention and a best mode presently contemplated for carrying out the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a general schematic block diagram of an HBEV powertrain including an electric control system. 
     FIG. 2 is a schematic software diagram illustrating principles of the invention. 
     FIG. 3 is a schematic hardware diagram illustrating principles of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates a hybrid electric vehicle (HEV)  10  that has an electric motor  12  whose shaft applies torque input to a drivetrain  14  that includes an axle  16  having driven wheels  18 . HEV  10  includes other wheels  18  which may be non-driven. One source of electric power for operating motor  12  comprises an on-board compliment of D.C. batteries  20 . Another source comprises an internal combustion engine  22 , a diesel engine for example, that drives an electric generator  24 . As engine  22  runs, it operates electric generator  24 , which can deliver electricity to run motor  12 . Drivetrain  14  delivers torque to driven wheels  18  on axle  16 , thereby propelling vehicle  10  along a surface on which all wheels  18  support the vehicle. 
     FIG. 1 further shows an associated electric control system  26  that may include distinct, but inter-related, subsystems for controlling operation of motor  12 , operation of engine  22 , operation of electric generator  24 , and re-charging of D.C. batteries  20 . The control allows the options of operating HEV  10  by use of D.C. battery power from batteries  20 , or of operating the vehicle by running engine  22  to operate generator  24 . Engine  22  can also operate generator  24  to re-charge batteries  20 . 
     HEV  10  is similar to certain internal-combustion-engine-powered automotive vehicles in having like control inputs for the driver to operate, including an accelerator control input  28 , a service brake control input  30 , and a parking brake control input  32 , each of which is operable independent of the others. Each control input includes a respective actuator, foot-operated pedals  28 A,  30 A respectively for accelerator control input  28  and service brake control input  30  respectively, and either a foot-operated pedal, or a hand-operated pull or lever,  32 A for parking brake control  32 . Depressing accelerator pedal  28 A from an idle position accelerates HEV  10 . Depressing service brake pedal  30 A from rest position applies service brakes  34 . A parking brake  36  is applied by pulling pull, or lever,  32 A. 
     Service brakes  34  are fluid-power-operated, and each wheel  18  has its own service brake mechanism. Parking brake  36  is a mechanical, non-fluid-operated mechanism, or mechanisms, proximate a portion, or portions, of drivetrain  14 . 
     Accelerator control input  28  further includes an electric circuit device  38 , a potentiometer for example, forming one of a number of control inputs to electric control system  26 . Service brake control input  30  further includes an electric circuit device  40 , a switch for example, forming another control input to system  26 , and parking brake control input  32  further includes an electric circuit device  42 , a switch for example, forming yet another control input to system  26 . Each respective switch  40 ,  42  is set to trip just as the vehicle driver commences application of the respective brake. 
     Accelerator pedal  28 A, acting through potentiometer  38 , provides a torque request signal input to system  26 . As accelerator pedal  28 A is increasingly depressed from an idle position, a wiper of potentiometer  38  is increasingly displaced from idle position to deliver an increasing torque request signal. System  26  responds by causing motor  12  to deliver increasing torque in correlation with the increasing torque request signal. While the torque load that is imposed by HEV  10  on motor  12  is a function of several factors, including road load and wind resistance load, the speed at which HEV  10  travels will generally increase as accelerator pedal  28 A is increasingly depressed and will generally decrease as the pedal is increasingly released. When the accelerator pedal is in idle position, no torque request signal is being input to system  26 . 
     If the vehicle driver depresses service brake pedal  30 A with the same foot used to operate accelerator pedal  28 A, a return spring acting on accelerator pedal  28 A should be effective to return the released accelerator pedal to idle before the driver depresses the service brake pedal. In that case, potentiometer  38  will have returned to idle position before switch  40  is tripped to signal that the service brake is being applied. Because potentiometer  38  delivers a zero torque request signal input to system  26  when in idle position, system  26  should be commanding motor  12  to deliver no torque to drivetrain  14  when switch  40  is tripped to signal service brake application. Such a mode of operation is desirable in order to avoid the counter-effect of motor  12  trying to drive driven wheels  18  at the same time that the service brakes are trying to stop them. 
     Because of the independent operability of each of the three control inputs, it is possible for either one, or both, brakes  34 ,  36  to be applied while accelerator pedal  28 A is being depressed. For example, if the driver depresses brake pedal  30 A with one foot while the other foot is still depressing accelerator pedal  28 A, the motor torque that would be applied through drivetrain  14  to drive wheels  18  would counteract the braking force being applied to the driven wheels by the service brakes. Such a condition is considered undesirable for reasons explained earlier. The present invention, as will be more fully explained, prevents that condition from occurring. 
     Parking brake  36  can also be applied while accelerator pedal  28 A is being depressed, and that is another condition that would be considered undesirable. The present invention, as will be more fully explained also, prevents that condition too from occurring. 
     FIG. 2 discloses a torque command strategy software solution suitable for a system  26  that is microprocessor-based. For controlling the operation of motor  12 , the microprocessor-based system embodies a traction control strategy, depicted generally by a block  50 . The Figure shows some of the various control inputs to block  50 , including a software implementation of an interface  52  embodying principles of the present invention. The interface includes a torque demand look-up table  54 , and software equivalents of a switch  56 , an OR logic gate  58 , and a maximum value selector  60 . 
     Switches  40  and  42  provide respective inputs to OR logic gate  58 , which in turn controls switch  56 . One input to maximum value selector  60  corresponds to the signal from potentiometer  38  representing the extent to which accelerator pedal  28 A is depressed. The other input to maximum value selector  60  is a cruise control speed request signal derived from a cruise control system that, when turned on by the driver, sets a desired speed at which the vehicle runs. The output of maximum value selector  60  is the larger of the two inputs, and that output is passed as an input to switch  56 . Another input to switch  56  is fixed at zero. 
     Switch  56  functions to pass the signal from maximum value selector  60  to torque demand look-up table  54  so long as neither switch  40  or  42  has been tripped. In that case, table  54  supplies to block  50  a torque command signal that is correlated by the table to the value of the larger of the accelerator pedal speed request signal and the cruise control speed request signal. While the requested torque will be delivered to the driven wheels under typically normal operating conditions, the occurrence of atypical operating conditions, such as may be sensed by other control inputs, may cause the actual torque delivered to be different from the requested torque that would be delivered under typically normal conditions. For example, a wheel speed sensor that senses wheel slip may cause torque delivered to driven wheels to differ from torque requested by table  54 . 
     When either switch  40  or  42  is tripped, switch  56  passes the fixed zero input to table  54  instead of the signal from maximum value selector  60 . Under this condition, a zero torque demand signal is applied to block  50  from interface  52 . Under typical normal operation, this will result in zero motor torque, or at least insufficient motor torque to propel the vehicle, being delivered from motor  12 . 
     It should be appreciated that if the vehicle lacks a cruise control feature, maximum value selector  60  could be omitted, and the signal derived from potentiometer  38  applied directly to switch  56 . 
     FIG. 3 discloses a torque command strategy hardware solution suitable for implementing interface  52 . The hardware includes two normally closed relays  60 ,  62  having respective coils  60 A,  62 A and respective normally closed contacts  60 B,  62 B connected in circuit with other circuit devices as portrayed. Relay  60  is present because the particular accelerator pedal position sensor that contains potentiometer  38  also contains an idle validation switch. The fact that an idle validation switch is present in the sensor does not directly bear on the present invention, and it is to be therefore appreciated that it is shown merely for reference. 
     Insofar as principles of the present invention are concerned, FIG. 3 shows that the wiper of potentiometer  38  is connected through contacts  62 B to block  50 . Switches  40  and  42  are connected to relay coils  60 A,  62 A such that tripping of either switch will energize both coils to operate both sets of contacts  60 B,  62 B open. The opening of contacts  62 B disconnects block  50  from potentiometer  38  which is understood by the system to mean that zero motor torque output is being requested. 
     While a presently preferred embodiment of the invention has been illustrated and described, it should be appreciated that principles of the invention are applicable to all embodiments and uses that fall within the scope of the following claims.