System and method for shifting two speed transmission
Methods and systems for shifting a transmission that includes a dog clutch are described. In one example, the transmission may be coupled to an electric machine and a rotational speed of the electric machine may be adjusted to reduce a speed differential between rotating transmission components. A position of a shifter actuator may be adjusted according to an estimate of when the speed differential is equal to a predetermined value.
1 . An electric propulsion system, comprising:
an electric machine;
a step gear ratio transmission including at least two gear ratios, the step gear ratio transmission including a shifter actuator; and
one or more controllers including executable instructions that cause the one or more controllers to estimate an amount of time for a differential speed between a rotational speed of an on-coming gear and a rotational speed of a transmission shaft to be less than a threshold rotational speed.
2 . The electric propulsion system of claim 1 , where threshold rotational speed is a maximum rotational speed difference between the rotational speed of the on-coming gear and the rotational speed of the transmission shaft for engaging the on-coming gear.
3 . The electric propulsion system of claim 2 , where the amount of time is determined via an observer.
4 . The electric propulsion system of claim 3 , further comprising additional executable instructions that cause the one or more controllers to estimate an amount of time to engage the on-coming gear via the shifter actuator based on an average speed of the shifter actuator.
5 . The electric propulsion system of claim 4 , further comprising additional executable instructions that cause the one or more controllers to reduce the differential speed between the rotational speed of the of the on-coming gear and the rotational speed of the transmission shaft via operating the electric machine in a speed control mode and adjusting speed of the electric machine when an off-going gear is disengaged and while the step gear ratio transmission is in a neutral state.
6 . The electric propulsion system of claim 5 , where speed of the electric machine is adjusted during a speed synchronization phase of a gear shift.
7 . The electric propulsion system of claim 1 , where the shifter actuator is mechanically coupled to a shift fork and a dog clutch, and where the transmission shaft is a transmission output shaft.
8 . The electric propulsion system of claim 1 , where the transmission shaft is an intermediate shaft.
9 . An electric propulsion system, comprising:
an electric machine;
a step gear ratio transmission including at least two gear ratios, the step gear ratio transmission including a shifter actuator; and
one or more controllers including executable instructions that cause the one or more controllers to estimate an amount of time for a differential speed between a rotational speed of an on-coming gear and a rotational speed of a transmission shaft to be less than a threshold rotational speed, and additional instructions that cause the one or more controllers to adjust a position of the shifter actuator in response to the amount of time for the differential speed between the rotational speed of the on-coming gear and the rotational speed of the transmission shaft being less than the threshold rotational speed.
10 . The electric propulsion system of claim 9 , further comprising additional executable instructions to operate the electric machine in a speed control mode while adjusting the position of the shifter actuator.
11 . The electric propulsion system of claim 10 , where the electric machine is operating in the speed control mode during a synchronization phase of a gear shift.
12 . The electric propulsion system of claim 9 , where the transmission shaft is an intermediate shaft, and where the position of the shifter actuator is adjusted from a neutral position to a reliably engaged position.
13 . The electric propulsion system of claim 9 , where the shifter actuator is mechanically coupled to a dog clutch.