Device and method for adjusting the speed of a vehicle

Abstract

A device ( 1 ) and a method implementable therewith for regulating the driving speed of at least one vehicle ( 3 ), having an electric motor/generator ( 17 ) connected or connectable to a drive train ( 7; 7 ′) for at least one wheel ( 11, 13; 11′, 13 ′) as a function of at least its actual speed and setpoint speed. The device ( 1 ) includes a control unit ( 31 ) for controlling the torque of the electric motor/generator ( 17 ), means for driving the electric motor/generator ( 17 ), means ( 37 ) for recording the actual speed of the vehicle ( 3 ) and means ( 39 ) for preselecting the setpoint speed of the vehicle ( 3 ). The device ( 1 ) is characterized in that the electric motor/generator ( 17 ) is usable in generator operation to generate a braking torque and in engine operation to generate a driving torque.

What is claimed is:  
     
         1 . A device ( 1 ) for regulating the driving speed of a vehicle ( 3 ) having at least one electric motor/generator ( 17 ) connected or connectable to a drive train ( 7 ;  7 ′) for at least one wheel ( 11 ,  13 ;  11 ′,  13 ′) as a function of at least its actual speed and setpoint speed, comprising a control unit ( 31 ) for controlling the torque of the electric motor/generator ( 17 ), means for driving the electric motor/generator ( 17 ), means ( 37 ) for recording the actual speed of the vehicle ( 3 ), and means ( 39 ) for preselecting the setpoint speed of the vehicle ( 3 ), 
 wherein the electric motor/generator ( 17 ) may be used in generator operation to generate a braking torque as well as in motor operation to generate a driving torque.  
 
     
     
         2 . The device as recited in  claim 1 , wherein the electric motor/generator ( 17 ) is connected by electric lines ( 43 ,  45 ) to a current storage device ( 47 ) and at least one electric consumer ( 49 ).  
     
     
         3 . The device as recited in one of the preceding claims, wherein the control unit ( 31 ) has at least one electronic control device ( 33 ) which is designed to demand of the electric motor/generator ( 17 ) a positive torque (driving torque) when the actual speed drops below the setpoint speed in driving operation of the vehicle ( 3 ) and to demand a negative torque (braking torque) when the actual speed exceeds the setpoint speed.  
     
     
         4 . The device as recited in one of the preceding claims, wherein the electric power consumption by at least one electric consumer ( 49 ) can be increased by the control unit ( 31 ).  
     
     
         5 . The device as recited in one of the preceding claims, wherein the torque of an internal combustion engine ( 15 ), which is connected or connectable to a drive train ( 7 ;  7 ′) for at least one wheel ( 11 ,  13 ;  11 ′,  13 ′), is controllable by the control unit ( 31 ).  
     
     
         6 . The device as recited in one of the preceding claims, wherein the internal combustion engine ( 15 ) and the electric motor/generator ( 17 ) are connected or connectable to the same drive train ( 7 ) or to different drive trains ( 7 ;  7 ′).  
     
     
         7 . The device as recited in one of the preceding claims, wherein strategies for distributing the torque required to implement the required setpoint speed of the vehicle ( 3 ) between the internal combustion engine ( 15 ) and the at least one electric motor/generator ( 17 ) are stored in the control unit ( 31 ).  
     
     
         8 . The device as recited in one of the preceding claims, wherein a brake ( 29 ) is provided for the at least one wheel ( 11 ;  13 ;  11 ′;  13 ′), and the brake ( 29 ) is operable by the control unit ( 31 ).  
     
     
         9 . A drive system ( 5 ;  5 ′,  5 ″) for a vehicle ( 3 ), comprising at least one electric motor/generator ( 17 ) and, optionally, an internal combustion engine ( 15 ), each being connected or connectable to at least one drive train ( 7 ,  7 ′) for at least one wheel ( 11 ;  13 ;  11 ′;  13 ′), and having a device ( 1 ) for regulating the driving speed of the vehicle ( 3 ), in particular as recited in one of claims  1  through  8 .  
     
     
         10 . A method of regulating the driving speed of a vehicle ( 3 ) having at least one electric motor/generator ( 17 ), as a function of at least its actual speed and the required setpoint speed, the actual speed being determined and the setpoint speed being adjustable, and a comparison of the actual speed with the setpoint speed being performed, wherein deceleration of the vehicle ( 3 ) is required when the actual speed is greater than the setpoint speed, and, to do so, the electric motor/generator ( 17 ) is operated as a generator, and when the actual speed is less than the setpoint speed, the electric motor/generator ( 17 ) is operated as a motor.  
     
     
         11 . The method as recited in one of the preceding claims, wherein in addition at least one brake ( 29 ) cooperating with at least one wheel ( 11 ;  13 ;  11 ′;  13 ′) of the vehicle ( 3 ) is actuated to increase the braking torque when the actual speed is greater than the setpoint speed.  
     
     
         12 . The method as recited in one of the preceding claims, wherein for the purpose of decelerating and accelerating the vehicle ( 3 ), the torque of an internal combustion engine ( 15 ) of the vehicle ( 3 ) is varied accordingly.  
     
     
         13 . The method as recited in one of the preceding claims, wherein when the electric motor/generator ( 17 ) is in motor operation, it is supplied with current by at least one current storage device ( 47 ) for driving the vehicle ( 3 ), and, when the electric motor/generator ( 17 ) is in generator operation, the current it generates is stored by the at least one current storage device ( 47 ) and/or is consumed by at least one electric consumer ( 49 ).  
     
     
         14 . The method as recited in one of the preceding claims, wherein when there is at least one electric consumer ( 49 ), the electric power consumption is increased if the at least one current storage device ( 47 ) cannot store all of the current generated by the electric motor/generator ( 17 ) in generator operation and the deceleration of the vehicle ( 3 ) due to the braking torque of the electric motor/generator ( 17 ) is not sufficient.  
     
     
         15 . The method as recited in one of the preceding claims, wherein short-term and/or relatively minor fluctuations in the driving torque required to keep the vehicle ( 3 ) at a constant speed are compensated exclusively by the electric motor/generator ( 17 ).  
     
     
         16 . The method as recited in  claim 15 , wherein the vehicle is compensated by regenerative braking when the driving speed is too high, and when the driving speed is too low, it is compensated by the electric motor/generator supplying a driving torque.  
     
     
         17 . The method as recited in one of the preceding claims  15  and  16 , 
 wherein after a certain period of time (t max ) during which fluctuations in the driving torque are compensated exclusively by the electric motor/generator, the torque of the internal combustion engine is regulated up or down, preferably via an integrator, and the contribution of the electric motor/generator to the total driving torque is returned to zero.  
 
     
     
         18 . The method as recited in one of the preceding claims  15  through  17 , 
 wherein if the torque supplied by the electric motor/generator is not sufficient to maintain the required setpoint speed, the torque of the internal combustion engine or the gear ratio is adjusted accordingly.