Continuous Variable Transmission (CVT) Working Principle

 We already know that the job of the transmission is to change the speed ratio between the engine and the wheels of an automobile. The transmission use two gears with different diameters. So that the rotation from the crankshaft, can be change to make it has more torque with lower speed.

But how about automatic transmission ? did this thing using several gears or not ?

In this article, we will learn about CVT transmission. Which is this transmission, widely use in automatic motorcycles.

Basic of Automatic Transmission

Unlike traditional automatic transmissions, continuously variable transmissions don't have a gearbox with a set number of gears, which means they don't have interlocking toothed wheels. The most common type of CVT operates on an ingenious pulley system that allows an infinite variability between highest and lowest gears with no discrete steps or shifts.

To change the speed ratio, CVT use variable diameter pulley. This pulley has ability to change the diameter, according to the engine speed.

To make it easier, I will dissemble every part of continuous variable transmission on motorcycles.

You can see, this component called drive pulley. While the other one, is driven pulley. Drive pulley is installed on the crankshaft section. So that, this pulley will rotate when the engine run, and the speed is influenced by crankshaft rotational speed.

While the driven pulley, located In the back. Attached with the wheel, and the speed is same as wheel rotation.

Both of the pulley, connected by a V belt.

As I tell before, that this transmission using variable diameter pulley. It refer to drive pulley, and driven pulley. Both of them has ability to change their diameter, but in opposite way.

It mean, when drive pulley increase the diameter, the diameter of driven pulley will shrink.

The basic of CVT to change the speed ratio

The basic is very simple. In low RPM, the drive pulley always on the smallest diameter. While the driven pulley, in maximum diameter. In this position, the drive pulley has smaller diameter than the driven pulley.

So, it will decrease the output speed. And the torque, is increase.

When we pull the throttle, engine RPM raise. The faster the engine RPM, the bigger the drive pulley’s diameter. So, this RPM increase will rise the diameter of drive pulley. When the drive pulley’s diameter is raising, the driven pulley will decrease it’s diameter automatically.

It make, both of the pulley have same diameter. So the engine speed is continued to the wheel in same speed.

In high RPM, the drive pulley’s diameter keep increase. It make the drive pulley has bigger diameter than the driven pulley. So the wheel rotation, will be faster than the engine RPM.

But how the drive pulley change the diameter ?

The drive pulley, use centrifugal force to change the diameter. To be more understand, let’s dissemble the drive pulley.

The drive pulley consist of three main part. The frame. This is a static component, that directly connected to the engine crankshaft. The slide plate. This is a moving component, that has function to make the diameter bigger, or shrink.

While this cylinder components, called roller. It’s like a ballast to control the movement of slider part. The roller are installed around the shaft. When it rotate, the centrifugal force will rise. Centrifugal force is an outflow force from the rotational movement.

In simple way, the centrifugal force will make the roller stay away from the axis. But, due to roller have crooked path, the roller movement will push the slider plate.

Each plate is made of two 20 degree cones facing each other. A belt rides in the groove between the two cones. When the two cones of the plate are far apart, the belt rides lower in the groove. and the radius of the belt loop going around the pulley, gets smaller. When the cones are close together, the belt rides higher in the groove. and the radius of the belt loop going around the pulley gets larger.

To keep the belt tight, the rear pulley will adapt the front pulley diameter. This pulley, has a spring that always push the plate in close position.

Another main component on automatic transmission, is centrifugal clutch.

This clutch will make the wheel stay quite, while the engine run on idle RPM. This clutch located in the driven pulley, at the wheel axis.

It use a series of component like a brake shoe. This shoe, connected to the driven pulley. In idle RPM, we can see the gap between the shoe and the drum where the drum connected to the wheel. But if the speed increase, the shoes will move outway. It will lose the gap, so the wheel will rotate according to the pulley rotational speed.

That’s how CVT works. It is very simple right ? what do you think ? type in comment below.

Popular posts from this blog

Fungsi Relay 4 kaki & 5 kaki (Plus Gambar Rangkaiannya)

Image
Cara Kerja Relay – Pada rangkaian kelistrikan mobil kita sangat familiar dengan yang namanya relay, lantas apa anda sudah sepenuhnya mengerti apa itu fungsi relay bagaimana cara kerja relay ? diartikel ini akan kita bahas sedetail mungkin mengenai cara kerja relay 4 kaki dan relay 5 kaki. Fungsi relay adalah sebagai jembatan penghubung antara arus dari baterai langsung ke masa. Penggunaan relay akan memotong alur arus listrik yang melewati rangkaiaan untuk mencapai beban. Artinya, relay akan membuat aliran arus lebih sederhana dan lebih ringkas. Hasilnya, hambatan yang terjadi pada rangkaian kelistrikan tersebut akan lebih kecil sehingga penggunan listrik bisa lebih hemat dan beban kelistrikan bisa lebih maksimal kinerjanya. Relay bekerja seperti saklar biasa namun saklar ini akan digeraka  oleh skema elektromagnetik yang diatur oleh saklar utama. Dalam hal ini saklar didalam relay akan menghubungkan arus langsung dari baterai ke beban kelistrikan, sehingga arus besar dari b
Read more

Lampu Indikator Mesin Vixion Menyala/Berkedip, Apa Penyebabnya ?

Image
Bagi pemilik Vixion kedipan lampu indikator menjadi sesuatu yang bikin jantung berdebar kencang. Betapa tidak, lampu indikator ini menyiratkan bahwa ada kerusakan pada sistem injeksi motor. Sementara itu, kita tahu bengkel di pinggir jalan saja suka nyerah kalau berhubungan dengan masalah injeksi. Ini karena kerusakan pada sektor injeksi mesin, hanya bisa dideteksi oleh alat scan yang hanya dimiliki oleh Yamaha. Lantas, apa yang harus dilakukan kalau lampu indkator ini berkedip atau bahkan nyala terus ? Bagi mekanik, lampu indikator berwarna kuning ini disebut dengan MIL (malfunction indicator light) atau beberapa menyebutnya lampu check engine. Lampu indikator ini berfungsi layaknya notifikator yang akan memberitahukan bahwa ada fault atau ada yang tidak beres pada kelistrikan mesin. Dalam kondisi normal, lampu ini akan hidup beberapa detik saat kunci kontak ON lalu akan mati dan tidak hidup lagi. Namun, kalau lampu tidak mau mati atau bahkan kedap-kedip, maka terdeteks
Read more

Rangkaian dan Cara Kerja Sistem Klakson Dengan Relay

Image
Rangkaian Klakson Kendaraan – Klakson atau horn menjadi perangkat wajib pada kendaraan karena perangkat ini akan mencegah terjadinya kecelakaan dengan cara memberi signal berupa suara. Tak jarang kerusakan sistem klakson juga dapat menjadi awal sebuah kecelakaan lalu lintas. Kali ini kita akan membahas seluk beluk mengenai cara kerja dan rangkaian sistem klakson pada mobil sertamotor. Mengapa anda harus mempelajari cara kerja perangkat ini ? tujuanya adalah agar ketika klakson mobil atau motor anda bermasalah, anda tidak panik dan tahu cara memperbaikinya. Lantas seperti apa cara kerja sistem klakson ini ? simak ulasanya dibawah Pengertian Klakson Klakson adalah berupa komponen yang dapat mengeluarkan suara ketika terdapat trigger berupa energi listrik atau energi angin. Klakson terbagi menjadi dua jenis, Electric Horn , komponen ini akan mengeluarkan suara ketika dialiri listrik. Prinsip kerjanya, baja spiral akan bergerak karena adanya gaya elektromagnet. Ketika baja s
Read more