The synchromesh gearbox is similar to the constant-mesh gearbox, but the synchromesh gearbox is provided with a synchronizer, the device by which two gears to be engaged are first brought into frictional contact which equalizes their speed, afterward they are engaged smoothly.
To engage, when the gear lever is moved the synchronizer cone meets with a similar cone on the pinion. Due to friction, the rotating pinion is made to rotate at the same speed as the synchromesh unit. To give a positive drive further, movement of the gear lever enables the coupling to override several spring load balls and the coupling engages with the dogs on the side of the pinion. Since both pinions and synchromesh units are moving at the same speed, this engagement is done without noise or damage to the dogs.
A slight delay is necessary before engaging the dog teeth so that the cones have a chance to bring the synchronizer and pinion to the same speed. An epicyclic gear train also known as planetary gear consists of two gears so that the center of one gear rotates around the center of the other. A carrier connects the centers of two gears and rotates to carry one gear, called planet gear or planet pinion, around the other, called sun gear or sun wheel.
The rays of the planet and the sun form traps so that their pitch circles are rolled without slip. A point on the pitch circle of the planetary gear traces an epicyclic curve. In this simplified case, the sun gear is fixed and there is planetary gear rolled around the sun gear. An epicyclic gear train can be assembled so the planetary gear is rolled onto a fixed, external gear ring or inside the pitch circle of the ring gear, sometimes called the annular gear.
In this case, the curve detected by a point on the planet pitch circle is a hypocycloid. The combination of epicyclic gear trains with a planet engaging both a sun gear and a ring gear is called planetary gear train. In this case, the ring gear is usually fixed and the sun gear is operated. Various speeds are obtained automatically in gearboxes known as automatic gearboxes.
Generally, the driver selects the car condition such as neutral, forward or reverse. The gear selection, timing, and engagement of gear for the required gear speed select automatically when the accelerator press or depress..
The Automatic gearbox does not require a gear change lever and a clutch pedal. Since, both clutch and transmission are a combined unit which works automatically. The automatic gearbox operates in two ways namely. Hydramatic transmission, and2.
Torque converter transmission. Nowadays, automatic transmissions are popular with various names prescribe by the manufacturers. They may differ in construction slightly. Somebody employs only fluid coupling with the planetary transmission. But others may include a torque converter with fluid coupling and planetary transmission as per their requirements. In the case of a dramatic transmission gearbox, the planetary gear sets connect in such a way that power may transmit through them.
A centrifugal governor in the transmission chooses the proper gear according to the speed and throttle position. The gear shifting from one gear to another gear is done through hydraulically operated pistons by actuating springs.
These springs control the brake bands on the planetary gear sets and clutches within the planetary unit. The various shifts achieves by the throttle and centrifugal governor. A torque converter is a type of fluid coupling that transmits rotational power from a prime mover, such as an internal combustion engine, to a rotating driven load. In a vehicle with an automatic transmission, the torque converter connects to the power source to the load. The manual transmission will have an equal space mechanical clutch.
The main feature of a torque converter is its ability to increase torque when the output rotational speed is so low that it allows the fluid from the winding vanes of the turbine to separate from the stator while it close against its one-way clutch, thus providing the equivalent of a reduction gear.
This is a feature beyond simple fluid coupling, which can match rotational speed, but does not multiply torque, thus reducing power. Torque converter transmission system employs fluid coupling, torque converter and epicyclic gear arrangement. Gears are required to keep the engine at rotational speeds where it creates a desirable amount of power across a wide range of road speeds.
Generally, the faster an engine turns, the more fuel it consumes, and the more power it makes. Engines are also only capable of rotating to a maximum speed redline. Gears are designed for a given limited range of road speed. First gear allows the engine to provide a large amount of power at very low speed. Once a reasonable road speed is achieved and the engine reaches the upper portion of it's usable range, a higher gear is selected. This positions the engine speed down toward the lower end of it's range for the same given road speed.
The process is repeated until the vehicle reaches the point where the gearing provides the highest possible vehicle speed matched with the highest possible engine power. Sign up to join this community.
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Learn more. Why do you need to change gears in car? Ask Question. Asked 8 years, 3 months ago. Active 3 years, 4 months ago. Viewed 9k times. Improve this question. This question appears to be off-topic because it is about maintenance or repair — Gabriel Mongeon. This makes the engine run faster, anything up to around RPM or more. We have the low gears 1st gear for lowest road wheel speed but the greatest torque , going up to the highest gear 5th gear for highest road wheel speed but the least torque.
Cars are very heavy, so if the spinning main shaft coming from the engine was connected directly to the road wheels, it would be very difficult to move the car away from a stationary position and the engine would almost certainly stall. In fact, if the main shaft from the engine was connected directly to the road wheels, this would be the equivalent of a permanent 4th gear which would make moving off very difficult.
To help prevent engine stall, we need two things; a clutch which we wont get into now and low gears which allows us to convert the high speed of the engine to a low speed at the road wheels. Inside the gearbox are cogs connected to other cogs which make up gear ratios.
When different sized gears connect together, they spin at different speeds and deliver different amounts of power. A small input gear that's connected to a large output gear creates a lot of power, but very little speed and this is called a low gear 1st gear ideal for moving the car off from a stationary position.
Low gears are essential for letting us move off from a stationary position and is one of the main reasons why gears are used in cars. Conversely, a large input gear connected to a small output gear creates little power, but a lot of speed and is called a high gear 5th gear , ideal for high road speeds.
A car that is moving has momentum, therefore it doesn't require a gear that has much power. High gears such as 5th or 6th allow the car to move at a faster speed than what the engine would be capable of if it didn't have gears. Ultimately the reason why gears are used in cars is so that we can combine engine speed RPM with the correct amount of power torque to complete an objective such as moving off or traveling at high speeds.
Why Are Gears Used in Cars? The Car Engine. Fuel is ignited and pushes the pistons in the engine down. This spins the crankshaft which produces kinetic energy.
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