Types of Car Transmission (Part 2)

( Continued from previous articles )

Automatic Gearbox Transmission

In the previous article we have discussed about the gearbox transmission system (gearbox) manual, where the operation of the removal of the teeth ratio is done manually by the rider. The next gearbox transmission system that we will discuss is the automatic gearbox transmission system. Switching between gear ratios in this gearbox system occurs automatically without the initiation process of the rider. The driver simply chooses the D ( Drive ) transmission to go forward, R ( Reverse ) to back off, P ( Parking ) for parking position, and N for neutral position. Once the rider chooses a D transmission, the transmission system will automatically shift the transmission to various ratios according to the speed of the vehicle and the field encountered.



Currently the development of automation technology gearbox transmission system is very advanced rapidly. Almost all leading car brand manufacturers are developing automated transmission system technology with different technologies and have become its own trademark.

Automatic Hydraulic Transmission System

Before I mention and explain about the various technologies of automatic transmission systems that have been developed by various car brands, I will explain one basic technology of automatic transmission gearbox system that is automatic hydraulic transmission system. Hydraulic transmission system is the development of hydraulic system in the form of fluid coupling which is combined with the use of gear transmission system in it. The main components of the automatic hydraulic transmission system are as follows:

  • Torque Converter. Torque converter is the development of hydraulic coupling (fluid coupling) which serves to connect between axis drive from the engine with automatic transmission gearbox system shaft. Converter torque replaces the friction clutch function in the manual transmission system. It is intended that the engine can always work even when the vehicle is in rest.

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    Components Torque Converter

    In contrast to fluid coupling, the torque characteristics of the converter is to increase the torque of rotation when the rotation speed of the shaft shaft is different from the speed of the transmission shaft spin. This is due to the presence of a single component in the form of a stator blade located halfway between the pump and the hydraulic turbine.

  • Hydraulic Pumps. An automatic hydraulic transmission system definitely requires a gear pump type hydraulic pump mounted on a central axle between the converter torque and the gear system. This pump serves to generate pressure on hydraulic oil which is then used for other system components.

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    Gear Pump In Automatic Transmission

    Sources of propulsion and pressure generation of this pump is the torque converter, so the faster the engine speed the faster the flow of flowing hydraulic oil flow. While the pressure is raised, also depends on the load conditions (road terrain) facing the vehicle. If the field is heavy, the hydraulic oil pressure will also be high. This concept will be used later in the selection of transmission gear ratios automatically.

  • Planetary Gear System . The most important component of an automatic transmission system is a series of planetary gear systems. This gearbox system consists of three parts of the gear of the sun gear, planetary gear, and the outer gear. Only by adjusting the rotation distribution configuration on the gearbox gear system, we will get 4 kinds of transmission system that is 3 forward transmission (direct rotation) and 1 reverse transmission (reverse rotation).

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    Planet Gear

    Three of the planet’s gear components, each of which can be a driving gear, a moving gear, or a silent gear. Determination of the gear configuration will result in varying ratio ratios. Notice if we determine the number of teeth on the outer gear is 72, and the sun gear is 30, then we will get some kind of gearbox ratio by adjusting the gear configuration. Notice the following table.

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    Planetary Gear Ratio

    In addition, if two of the three gears are in the lock-stationer position, a 1: 1 gear ratio is obtained. So overall there are 4 different gear ratios with only one planetary gear system, which is 3.4: 1 (forward), 1: 1 (advanced), 0.71: 1 (forward overdrive ), and -2.4: 1 (backwards).

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    Mechanism of Planetary Gear

  • Hydraulic Control System. The automatic transmission system requires an automatic control system to adjust gear shifting on planetary gear. This control system serves to set the locking and unlocking planetary gears against driven shafts or driven shafts. Each gear in the planetary gear system should be either coupling or uncoupling from the drive shaft or the driven shaft .

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    Hydraulic Control System In Automatic Transmission Mitsubishi Pajero th. 2001

    An automatic transmission hydraulic control system has components such as clutch clutches, steel bands, hydraulic pistons, spring-loaded valve, Machine load sensors, and shift valve. Here are the functions of each of these components:

    • The frictional clutch becomes the link between the drive shaft and the shaft driven with planetary gear gears. This friction coupling is designed in a complex way so that each gear can be connected to the shaft driven and the drive shaft.

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      Automatic Transmission Clutch



      One automatic transmission system that uses planetary gear uses 4 clutch friction to adjust the performance of its gears. One clutch friction is precipitated by a spring-loaded piston. This piston works based on hydraulic oil pressure, if the pressure is sufficient then the piston will be irradiated, and if the pressure is low then the piston will return to the starting position with the help of the spring in it.

    • The steel band serves to lock the planetary gear gear at stationary position (stationary). Like a clutch, this steel band is precipitated by a piston which also operates under the hydraulic oil pressure supplied to it. If the piston is in motion, the steel band located around the gear will lock the gear and connect it to the transmission system body so that the gear is in a stationary position.

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      Automatic Transmission Steel Band

    • Spring-loaded valve acts as a rotational speed sensor for output shaft rotation. Faster rotation of the shaft, greater valve opening so that the supply of hydraulic oil pressure to the system is greater. If the pivot turns more slowly, then the valve will be closing which is assisted with the spring in it.

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      Spring-loaded valve is located withingovernor

    • The automatic transmission system must know how heavy the machine is working, so that the transmission ratio transmission can match the load of the machine at hand. So we use the machine load sensor as one main component. This sensor can use two ways, the first way is to use a cable that is connected between the position of the gas pedal with the transmission system. If the accelerator is deeper pressed, then the pressure on the cable also increases. The second way is to use a vacuum modulator, by connecting the intake manifold with the transmission system (shift valve). The larger the machine load, then the vacuum modulator will read the condition of the system is getting vacuum.
    • Shift valve is a component in charge of adjusting hydraulic oil supply that will lead to actuator pistons in clutch and steel tape. Each transmission ratio shift requires one shift valve, for ratios 1 and 2 for example required one shift valve, as well as other switching ratios (2-3; 3- 4). Each shift valve has different working pressures, the higher the shift valve position, the higher the working pressure of the hydraulics. Thus, the transmission ratio transmission depends on the hydraulic working pressure controlled by spring-loaded valve according to the rotational speed of the wheel axle, which will then terminate the shift valve at a particular pressure point.

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      Shift Valve System

      Shift valve and the machine load sensor works opposite. The goal is that if the machine load is high, then the shift valve will not be too hasty to move to the next ratio until the working pressures corresponding to the specifications are met.

( Continued to next article )