Capacitive supercharger for electric shift mechanism

The invention provides a method of and an implementing assembly for shifting the transmission 12 of a vehicle having a battery 24 between park and various shift positions with a reversible motor 10 by supplying electrical energy from the battery 24 to the motor 10 to shift the transmission 12 in response to a shift selection 14 and characterized by storing electrical energy in a super capacitor 20 and transmitting that electrical energy stored in the capacitor 20 to the motor 10 for actuating the motor 10. The capacitor is placed in parallel with the battery 24 for charging the capacitor and in series with the battery 24 and the motor 10 to transmit the stored energy of the capacitor to the motor 10. The capacitor 20 stores sufficient electrical energy to actuate the motor 10 independently of the battery 24.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The subject invention relates to an improved system for supplying 
electrical energy to an actuator which positions the transmission of an 
automotive vehicle between park and various shift positions. 
2. Description of the Prior Art 
Normally, a vehicle operator moves the shift selector to the desired 
position and an electrical signal is generated to supply electrical power 
from the vehicle battery to a motor, i.e., actuator, to shift the 
transmission. However, in the event the vehicle battery is dead, i.e., 
fully discharged, there is insufficient electrical power for energizing 
the motor to shift the transmission. This is particularly a problem when 
the transmission is in the park position and a heavy load is on the 
transmission, thereby making it very difficult to move the transmission 
out of the park position. Under such heavy loads, the motor could be 
supplied with additional electrical energy to overcome such forces. 
It is well known to use capacitors to store electrical energy for later 
discharge to energize an accessory; however, it was left to applicants to 
solve this transmission shifting problems by using a capacitor. Examples 
of such prior uses are shown in U.S. Pat. No. 5,119,010 to Shirata et al, 
U.S. Pat. No. 5,243,522 to Salzmann and U.S. Pat. No. 5,260,637 to Pizzi. 
SUMMARY OF THE INVENTION AND ADVANTAGES 
The subject invention provides an improved method of shifting the 
transmission of a vehicle having a battery between park and various shift 
positions with a reversible motor. The method comprises the well known 
step of supplying electrical energy from the battery to the motor to shift 
the transmission in response to a shift selection but is characterized by 
storing electrical energy in a super capacitor and transmitting that 
electrical energy to the motor for actuating the motor. 
An assembly for performing the method of electrically controlling the 
shifting of a transmission in an automotive vehicle comprises an electric 
motor for shifting the transmission between park and various shift 
positions, an operator controlled selector device for selecting one of 
park and the various shift positions, and a motor control circuit for 
transmitting electrical signals from the selector device to the electric 
motor to actuate the motor. The assembly characterized is by a capacitor 
circuit for storing electrical energy to actuate the motor in response to 
signals form the motor control circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the Figures, wherein like numerals indicate like or 
corresponding parts throughout the several views, an assembly for 
electrically controlling the shifting of a transmission in an automotive 
vehicle is schematically shown in FIG. 1. 
The assembly includes an electric motor 10 for shifting the transmission 12 
of a vehicle between park and various shift positions, as is well known. 
An operator controlled selector device 14 is moved by the vehicle operator 
for selecting one of park and the various shift positions. Such a selector 
device 14 is the shift lever of an automobile, whether mounted on the 
steering column or on a center console. A central control circuit 16 is 
included for controlling the transmission of electrical signals from the 
selector device 14 to the electric motor 10 to actuate the motor 10. 
The assembly is characterized by a capacitor circuit, generally shown at 
18, for storing electrical energy to actuate the motor 10 in response to 
signals from the central control circuit 16. The capacitor circuit 18 
includes a super capacitor 20 and a switching circuit 22 for placing the 
super capacitor 20 in parallel with a battery 24 for charging of the super 
capacitor 20 and for placing the super capacitor 20 in series with the 
battery 24 and the motor 10 for discharging the super capacitor 20 to the 
motor 10. More specifically, the switching circuit 22 includes two 
switches 26, e.g., transistors as shown in FIG. 2, operated in unison 
between closed positions, as shown in phantom lines in FIG. 1, to place 
the super capacitor 20 in parallel with the battery 24 to charge the super 
capacitor 20, and open positions as shown in full lines as a series switch 
28, which is open when the switches 26 are closed, is closed to place the 
super capacitor 20 in series with the battery 24. 
The motor 10 is a reversible motor 10 and a motor control 30 is included 
for controlling the direction of movement of the motor 10. The central 
control circuit 16 also controls the switching circuit 22 and the motor 
control circuit 16. 
A position feedback circuit 32 is included for sensing the position of the 
transmission 12 and feeding a signal to the central control circuit 16. In 
this manner, the selected position of the transmission is assured, i.e., 
the motor is moved to the selected position. 
It is important that the super capacitor 20 has an energy capacity 
sufficient to actuate the motor 10 independently of the battery 24. In the 
event the battery is dead, the super capacitor 20 will have sufficient 
energy to move the motor 10 to the selected position. In the normal 
operating condition, the super capacitor 20 increases the power supplied 
by the battery 24 to overcome the loads associated with friction with 
friction and pull out of the park position. This increased torque for 
starting also allows the overall motor size to be reduced to thereby lower 
the cost of the motor. 
Accordingly, the invention provides a method of shifting the transmission 
12 of a vehicle having a battery 24 between park and various shift 
positions with a reversible motor 10 by supplying electrical energy from 
the battery 24 to the motor 10 to shift the transmission 12 in response to 
a shift selection 14 and characterized by storing electrical energy in a 
super capacitor 20 and transmitting that electrical energy stored in the 
capacitor 20 to the motor 10 for actuating the motor 10. In further 
definition, the capacitor is placed in parallel with the battery 24 for 
charging the capacitor and in series with the battery 24 and the motor 10 
to transmit the stored energy of the capacitor to the motor 10. The 
storing step is further defined as storing sufficient electrical energy in 
the capacitor 20 to actuate the motor 10 independently of the battery 24. 
The invention has been described in an illustrative manner, and it is to be 
understood that the terminology which has been used is intended to be in 
the nature of words of description rather than of limitation. 
Obviously, many modifications and variations of the present invention are 
possible in light of the above teachings. It is, therefore, to be 
understood that within the scope of the appended claims, wherein reference 
numerals are merely for convenience and are not to be in any way limiting, 
the invention may be practiced otherwise than as specifically described.