Eugenio,77
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Apr 2023

Addendum to the article: "Typology of Japanese hybrids"

The construction and operation principle of the transmission of the plug-in hybrid Prius 2016-2022 turned out to be mythologized, although in reality everything is extremely simple.

If in the conventional ZVW51/50/55 the motor-generator MG1 only performs the functions of a generator or starter for ICE, then in the PHEV it can be used as a traction motor together with MG2.


To ensure that MG1 can work as motor and prevent the ICE from rotating in the opposite direction, an one-way clutch is installed. When MG1 rotates in the opposite direction, the pawls engage with the notches of the clutch, providing blocking. When rotating in the same direction, the pawl passes through the notches without engagement, and as the speed increases, the centrifugal force exceeds the force of the spring, and the pawls do not enter the notches at all, which reduces losses.

1 - flywheel assy, 2 - one-way clutch assy, 3 - one-way clutch holding plate, 4 - pawl, 5 - spring, 6 - outer race (revolving gear), 7 - inner race (fixed gear). a - engine counter-rotation direction (locked), b - engine rotation direction (free), c - notch

1 - carrier, 2 - input shaft, 3 - sun gear, 4 - pinion gear, 5 - one-way clutch, 6 - final drive gear, 7 - final driven gear, 8 - counter driven gear, 9 - MG2 reduction gear, 10 - MG2 motor generator, 11 - counter drive gear (compound gear), 12 - ring gear, 13 - MG1 motor generator, 14 - oil pump, 15 - PSD (power split planetary gear unit). a - locked, b - free, c - inner race (fixed gear), d - outer race (revolving gear)

MG1 is used as an electric motor only in one mode - the car is moving with the help of electric motors, the battery has a sufficient charge level, and maximum power is required. Since MG1 usually rotates in the opposite direction to the ICE, the one-way clutch is locked, and the torque from MG1 is transmitted to the ring gear and further to the wheels, in addition to the torque from MG2.

1 - MG1, 2 - MG2, 3 - PSD, 4 - one-way clutch. a - drive, b - negative torque, c - positive torque, d - locked.

Specs of ZVW52 motor-generators:
MG1 - 1SM - 23 kW / 40 Nm, 600 V
MG2 - 1NM - 53 kW / 163 Nm, 600 V
30-minute power: 1NM - 37 kW, 1SM - 15.8 kW.

HEV typology : Toyota HSD · Daihatsu e-Smart · Honda i-MMD (e:HEV) ·
Honda i-DCD · Mitsubishi PHEV · Nissan e-Power · Subaru e-Boxer

Toyota Hybrid : E-Four · THS-C · HEV trans · BEV/FCEV · HEV trucks