Why are most Japanese cars with automatic transmissions CVT gearboxes?
Why are most Japanese cars with automatic transmissions CVT gearboxes?
The mainstream gearboxes currently used in automobiles include AT gearboxes, DCT (or DSG) gearboxes and CVT gearboxes. Among them, AT gearboxes are more common, DCT (or DSG) gearboxes are currently mainly used in German cars or domestic brands, and CVT gearboxes are the favorite of Japanese cars. Of course, some domestic brands also use them.
The two most famous AT gearbox manufacturers are Japan Aisin and ZF, which also reflects that Japan does not lack AT gearbox technology. However, in comparison, Japanese cars are still mainly equipped with CVT gearboxes, and the reason is closely related to Japan's development concept.
Japanese cars generally have low fuel consumption. There are many factors that affect automobile fuel consumption, in addition to the engine and gearbox, there are also main reduction ratio, vehicle weight, drag coefficient, tires, etc. Among them, the engine and gearbox are the two most important factors. So how much does the CVT gearbox affect fuel consumption?
CVT gearbox, also known as continuously variable transmission, has a relatively simple structure, mainly including basic components such as driving wheel set, driven wheel set, metal belt and hydraulic pump. The metal belt is composed of two bundles of metal rings and hundreds of metal sheets. The driving wheel set and the driven wheel set are composed of a movable plate and a fixed plate. The pulley on the side close to the oil cylinder can slide on the shaft, and the other side is fixed.
Both the movable plate and the fixed plate are conical structures, and their conical surfaces form V-shaped grooves to mesh with the V-shaped metal transmission belt. The power output by the engine output shaft is first transmitted to the CVT driving wheel, then transmitted to the driven wheel through the V-shaped transmission belt, and finally transmitted to the wheels through the reducer and differential to drive the car.
The working process of the CVT transmission is to change the working radius of the driving wheel and the driven wheel conical surface meshing with the V-shaped transmission belt by axial movement of the movable plate of the driving wheel and the driven wheel, thereby changing the transmission ratio. The axial movement of the movable plate is achieved by the driver adjusting the oil cylinder pressure of the driving wheel and the driven wheel through the control system according to the needs. Since the working radius of the driving wheel and the driven wheel can be adjusted continuously, stepless speed change is achieved.
Engine K24Z1
Through the entire shifting process of the CVT transmission, it is not difficult to find its several advantages:
The first is fuel saving：Since CVT can achieve stepless speed change in a fairly wide range, it can obtain the best match between the transmission system and the engine working conditions, thereby improving the fuel economy of the whole vehicle.
The second is power.：Due to the stepless speed change characteristics of CVT, it can obtain the transmission ratio with the largest backup power, so its power is significantly better than MT and AT transmissions.
The third is emissions：CVT has a wide speed ratio operating range, which enables the engine to work in the best working conditions, thereby improving the combustion process and reducing exhaust emissions.
The last is cost： The CVT system has a simple structure and fewer parts than AT. Once automakers start mass production, the cost of CVT will be lower than AT.
Engine 2AZ (RAV4)