Nissan cvt how does it work

The driving pulley is also called the input pulley because it's where the energy from the engine enters the transmission. The second pulley is called the driven pulley because the first pulley is turning it.

As an output pulley , the driven pulley transfers energy to the driveshaft. When one pulley increases its radius, the other decreases its radius to keep the belt tight. As the two pulleys change their radii relative to one another, they create an infinite number of gear ratios -- from low to high and everything in between. The simplicity and stepless nature of CVTs make them an ideal transmission for a variety of machines and devices, not just cars.

CVTs have been used for years in power tools and drill presses. They've also been used in a variety of vehicles, including tractors, snowmobiles and motor scooters. In all of these applications, the transmissions have relied on high-density rubber belts, which can slip and stretch, thereby reducing their efficiency.

The introduction of new materials makes CVTs even more reliable and efficient. One of the most important advances has been the design and development of metal belts to connect the pulleys.

These flexible belts are composed of several typically nine or 12 thin bands of steel that hold together high-strength, bow-tie-shaped pieces of metal.

Metal belts don't slip and are highly durable , enabling CVTs to handle more engine torque. They are also quieter than rubber-belt-driven CVTs. Although such a system seems drastically different, all of the components are analogous to a belt-and-pulley system and lead to the same results -- a continuously variable transmission. Here's how it works:. The wheels can rotate along two axes. They spin around the horizontal axis and tilt in or out around the vertical axis, which allows the wheels to touch the discs in different areas.

When the wheels are in contact with the driving disc near the center, they must contact the driven disc near the rim, resulting in a reduction in speed and an increase in torque i. When the wheels touch the driving disc near the rim, they must contact the driven disc near the center, resulting in an increase in speed and a decrease in torque i. A simple tilt of the wheels, then, incrementally changes the gear ratio, providing for smooth, nearly instantaneous ratio changes.

There is another type of CVT, known as a hydrostatic CVT, that uses variable-displacement pumps to vary the fluid flow into hydrostatic motors. In this type of transmission, the rotational motion of the engine operates a hydrostatic pump on the driving side. The pump converts rotational motion into fluid flow. Then, with a hydrostatic motor located on the driven side, the fluid flow is converted back into rotational motion.

Often, a hydrostatic transmission is combined with a planetary gearset and clutches to create a hybrid system known as a hydromechanical transmission. Hydromechanical transmissions transfer power from the engine to the wheels in three different modes. At a low speed, power is transmitted hydraulically, and at a high speed, power is transmitted mechanically. Between these extremes, the transmission uses both hydraulic and mechanical means to transfer power.

Hydromechanical transmissions are ideal for heavy-duty applications, which is why they are common in agricultural tractors and all-terrain vehicles. Continuously variable transmissions are becoming more popular for good reason. They boast several advantages that make them appealing both to drivers and to environmentalists. Here are some of the key features and benefits of CVTs:.

Cars with CVTs have been common in Europe for years. But it's taken a while for the technology to gain a foothold in the United States. Sold between and , the Justy never attracted the attention of American drivers.

The best way to answer that question is to take one of these cars for a test drive. When you step on the gas pedal of a car with a continuously variable transmission, you notice the difference immediately. The engine revs up toward the rpms at which it produces the most power, and then it stays there.

But the car doesn't react immediately. Then, a moment later, the transmission kicks in, accelerating the car slowly, steadily and without any shifts. That's because the CVT converts every point on the engine's operating curve to a corresponding point on its own operating curve. If you look at the power output curve for the car without a CVT, you can see this to be true.

Notice that the tachometer in this situation shows the engine revving up and down with each gear change, which is recorded as a spike in the power output curve and which the driver feels as a jolt. CVTs are equally efficient on hills. There is no "gear hunting," because the CVT cycles steplessly down to a gear ratio appropriate for the driving conditions. A conventional automatic transmission shifts back and forth trying to find the right gear, which is far less efficient.

With all of their advantages, CVTs do have some shortcomings. In the United States, they are still trying to overcome an image problem. The Subaru Justy, for example, was known as a gutless micro-car. Traditionally, belt-drive CVTs were limited in the amount of torque they could handle and were larger and heavier than their automatic and manual counterparts.

For more information on continuously variable transmissions and related topics, check out the links that follow. Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar.

Mobile Newsletter chat subscribe. Under the Hood. How CVTs Work. By: William Harris. Photo courtesy Nissan Global. How does a CVT compare to a conventional, planetary automatic transmission? What parts does it have and how do those parts work? What advantages do CVTs offer over conventional automatic transmissions? What about disadvantages? What's the driving experience like in a car with a CVT?

What kind of makes and models incorporate CVTs? Are there any other applications for CVTs other than automobiles? Transmission Basics " ". Read More. Pulley-based CVTs " ". A high-power metal or rubber belt A variable-input "driving" pulley An output "driven" pulley. The distance between the center of the pulleys to where the belt makes contact in the groove is known as the pitch radius.

Since neither the pulleys or the belt are fixed, they can provide an infinite number of gear ratios, unlike the automatic, which has a set number of gears. Not all CVTs are created the same. The most common type is the pulley-based, but some other types include the Toroidal CVT, which uses rotating discs along with power rollers to produce the same result as the pulleys.

The hydrostatic CVT uses pumps to control fluid flow, which then produces a rotational motion. Toyota recently made some changes to its CVT. CNET says it now uses what they call a Launch gear to provide drivers with the feeling of a conventional transmission. The launch gear is almost like the first gear in a regular automatic transmission. As the vehicle speeds up, the transmission will switch this out, so it starts working as a CVT.

Toyota says that using these new fixed gear ratios will not only feel more like a regular transmission; it will also increase belt efficiency and improve performance. One of the advantages of a CVT is its ability to continuously change its gear ratio. This means that no matter what the engine speed it, it is always performing at its peak efficiency.

CVTs often offer better fuel economy as a result, especially when driving in the city. Digital Trends says that most cars equipped with CVTs offer a smoother ride than a similar car with a regular automatic.

This is because the transmission never shifts. There is no abrupt downshifting when the car needs additional power, and there is no feeling of gear hunting that you sometimes feel with a traditional automatic. A CVT is lighter than a traditional automatic, and this, combined with the smoother operation, helps to improve the fuel efficiency of vehicles that come equipped with a CVT.

Because of the lack of gearing, it is easier for CVT vehicles to find and maintain an ideal torque ratio as well. It has an easier time taking off from a stoplight and an easier time climbing difficult terrain because the variable transmission allows it to run in the right "gear" and stay there.

While the lack of upshifting and downshifting is considered an advantage of the CVT, some drivers miss the sensation of the vehicle moving through the shift points.

If you prefer a sportier driving experience, then the lack of fixed gears makes the ride less engaging. Another complaint that drivers tend to make about a CVT is the loud droning sound that occurs during acceleration. This happens because the CVT forces the engine to continuously run a constantly high rpm as it gets up to speed. As Car Engineer explains, the general public has been less accepting of the CVT due to the difference in noise perception from mechanical or step automatic transmission.

CVTs can be expensive to repair or replace when compared to a conventional automatic transmission. Some of the common problems that owners run into include overheating, slipping, and sudden loss of acceleration. Shuddering is also a common problem. Since CVTs depend on the belts to operate, if these suffer from excessive stretching or too much wear, the transmission can completely fail.

According to Mister Transmission , while there are some advantages to having a CVT, traditional automatic transmissions also offer some benefits. Like a CVT, an automatic transmission also has some downsides. Some of these include:. How Stuff Works explains that an automatic transmission uses gear sets, a hydraulic system, and a torque converter.

The hydraulic system regulates the bands and clutches that control the gear sets, and a pump pushes the transmission fluid through. The fluid pressure forces the shift valves to open and close, which opens different gear circuits.

Now you know the difference between a CVT transmission and an automatic transmission. Which one works for you? New Cars. Buyer's Guide. Type keyword s to search. Today's Top Stories.