“Hondamatic” applied to the four-wheel ATV “Rubicon”

The infinitely variable, hydraulic mechanical automatic transmission features high durability and superb drivability. The HMT “Hondamatic” employed in the Rubicon has an integrated cylinder. The piston-type hydraulic motor and the hydraulic pump laid on a common axis transmit power and allow changing of the reduction ratio. The system allows selection of various types of modes such as the automatic reduction ratio control with a focus on using high power output, or on high torque, etc. Manual shifting mode can also be selected. In any mode, the reduction ratio is changed smoothly and steplessly without using a belt or gears.
Power transmission route of “Hondamatic”
To explain the power transmission route of “Hondamatic” employed in the Rubicon, firstly, the power (torque and revolutions) generated from the engine is transmitted via the clutch, etc. to the HMT and drives the swash plate of the HMT pump. The revolutions are reduced and the torque is increased by the hydraulic pump and the hydraulic motor, and the power is further transmitted from the output shaft to the sub transmission. From there on, the power is transmitted to the front and rear wheels via the sub transmission having 2 forward speeds (L, D), neutral and reverse.

Hondamatic cut model
Hondamatic cut model

Engine cut model
Engine cut model
Click the picture for enlarged view
Outlines on how Hondamatic functions
The Hondamatic is a system that provides an output from the pump and motor cylinder integrated with the output shaft by converting the input power into hydraulic pressure and by the movements of the hydraulic piston pump and the hydraulic piston motor. That means that the input power is split in the hydraulic pump into the hydraulic component and the mechanical component. That is, the “hydraulic power transmission” in that the power is transformed into the hydraulic pressure, amplified in the motor side, and becomes the torque by which the motor pistons turn the motor-side cylinder, and the “mechanical transmission” in that the power is transformed into the torque by which the pump pistons directly turn the pump-side cylinder by the hydraulic reaction force. As the pump cylinder and the motor cylinder are connected, and further integrated with the output shaft, the two transmission powers applied to each cylinder are given out as a single output. Thus, by supplementing the low efficiency part of the hydraulic trasmission with the mechanical transmission, high efficiency is attained. Detailed mechanism of Hondamatic
Working principles of hydraulic transmission and mechanical transmission
Input Engine power output (torque and revolutions)
Input gear
Pump-side swash plate is driven
Hydraulic (1)The seven pump pistons laid on an identical radius are pressed one after transmission another, by the angled swash plate, causing a hydraulic pressure to occur in the cylinder
(2)The high fluid pressure acts on the opposing motor pistons, and acts like pressing out the piston up to the corresponding displacement of each cylinder
(3)By the reaction force from the swash plate, the motor pistons provides the motor- side cylinder with the revolutions and the torque Tm
Mechanical (1)The reaction torque from the fluid acts on the pistons in the hydraulic pump
Transmission(2)The pump pistons press the pump cylinder and provide revolutions and torque Tin
Output The output shaft integrated with the cylinder is driven
to the sub transmission



The rotation force F coming in the pump swash plate produces hydraulic pressure
When producing the hydraulic pressure, the piston presses the cylinder wall by F’


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