Now that I have had several PMs and requests from RR members to explain the DAF transmission I think its about time I did this should keep me from repeating myself quite so often.
Here is a diagram of the variomatic as used in the 44 model.
The transmission is now known as a CVT transmission and uses the same basic principles, some cars using cvts now are Audis multitronic some nissans murano I think and nearly all Hybrids including the Toyota Prius.
Variomatics use a centrifugal clutch and a straight prop shaft to the splitter for primary pulleys. As the engine speed increases the clutch is engaged and drive is then given to the primary pulleys. There is a dog clutch and simple gear box between the primarys which allows for the selection of forward reverse and neutral.
The transmission changes ratio due to a mixture of inlet manifold pressure and centrifugal weights in the primary pulleys. Pressure changes cause a diaphragm in the primary pulleys to move and cause the pulley to expand and contract, this in turn forces the secondary pulleys to expand or contract under spring pressure as the belt diameter does not change. At high speeds centrifugal weights lessen this effect.
Another Vaccum system is conected to the braking system and ratio hold switch on the dashboard this acts on the other side of the diaphragm causing the primary to expand and the secondarys to contract, this effectively lowers the gear ratio and provides engine braking.
Thats basicly how the system works and really is very simple.
Here are a couple of videos one showing the transmission working and the other of a volvo vario showing how smooth the acceleration and ratio changes are
Here is a diagram of the variomatic as used in the 44 model.
The transmission is now known as a CVT transmission and uses the same basic principles, some cars using cvts now are Audis multitronic some nissans murano I think and nearly all Hybrids including the Toyota Prius.
Variomatics use a centrifugal clutch and a straight prop shaft to the splitter for primary pulleys. As the engine speed increases the clutch is engaged and drive is then given to the primary pulleys. There is a dog clutch and simple gear box between the primarys which allows for the selection of forward reverse and neutral.
The transmission changes ratio due to a mixture of inlet manifold pressure and centrifugal weights in the primary pulleys. Pressure changes cause a diaphragm in the primary pulleys to move and cause the pulley to expand and contract, this in turn forces the secondary pulleys to expand or contract under spring pressure as the belt diameter does not change. At high speeds centrifugal weights lessen this effect.
Another Vaccum system is conected to the braking system and ratio hold switch on the dashboard this acts on the other side of the diaphragm causing the primary to expand and the secondarys to contract, this effectively lowers the gear ratio and provides engine braking.
Thats basicly how the system works and really is very simple.
Here are a couple of videos one showing the transmission working and the other of a volvo vario showing how smooth the acceleration and ratio changes are