Automatic Transmissions Basics – Hydraulic Valves

Automatic transmissions system whether they are used to drive and power cars, trucks or tractor trailers use two different basic systems in their automatic transmission power transmission systems. The two basic different types of hydraulic valves that are used in automatic transmissions are first the pressure-regulator valve type and the balanced valve hydraulic setup. You can count on it that all of the valves found in 2010 / 2011 employed and used in your vehicle today is either one of these two family types. This article is part 1 of a two part article – dealing in this case with the first type of automatic transmission valve type – that being “pressure-regulator “valve types.

Simply put and explained the pressure regulator valve uses simple standard hydraulic action to prevent excessive pressure in any hydraulic system that it is used and employed in. The valve setup is that it is spring-loaded and has a small piston that can move back and forth in a cylinder bore. Valve movement produces a constant pressure from a variable pressure source. For example: suppose the pressure source is an oil pump driven by the engine. When the engine runs at high speed, this pump also runs and functions at high speed. Therefore if delivers a large volume of oil. This would produce excessively high pressure if it were not for the action and actions of the pressure- regulator valve and valves. On the other side of the road, when pump pressure is low, spring force will push the valve to the other side closing off the return line to its hydraulic reservoir.

As the pressure and pressures go up and thus increase overall. There is increasing force and power exerted onto the valve. When the preset valve (which is simply determined by the force of the spring) is reached, the oil pressure overcomes the spring force. The valve moves back into its cylinder bore. As the valve moves back, it uncovers an opening or port, which is connected to a return line to the oil reservoir. Now part of the oil from the pump can flow through the return line. This reduces the pressure so that valve starts forward again, moved by the force of the spring. However, as the valve moves forward, it partly shuts off the port to the return line. Since less oil can now escape, the oil pressure goes up and the valve is again moved back.

All in all it might be said. That the valve does not normally actually move back and forth in a real physical sense of motion. Instead it seeks and finds the very position at which oil pressure just basically balances spring force. Then, if the incoming oil volume changes because if a change in pump speed or speeds, the valve position will change. In operations, the valve maintains a constant pressure overall by bleeding off more or less oil from the pump itself. For example as the pump speed goes up – which means essentially that the pump delivers more oil and the pressure goes up – the valve is forced to open and “port” wider. This permits more oil to flow into the return line, preventing excessively high pressure and pressures.

The output-pressure and pump-pressure lines do not actually have to run the piston or any pistons in actuality in automatic transmissions. Pump pressure entering the output-pressure line is reduced essentially because the valve has positioning itself to allow excess oil to escape though the line. Just enough oil escapes to maintain the pressure in the output line at the value determined by the valve spring. In the actual transmission, the pressure-regulator valve is used with one or more “boost valves” in line with it. Under certain conditions, a boost valve will have oil pressure applied to it. This causes the boost valve to add to the forces of the spring in the pressure regulator valve. The result is that the output pressure is increased or “boosted”.

If you are driving your vehicle down the road or highway in 2010 / 2011 whether it is a truck, Sports Utility Vehicle, bus or even automatic transmission highways traffic trailer or even earth mover it is a bet that you have either type of hydraulic valve – either a pressure regulator valve or valves or the balanced type valve to thank for your reliable travels and transport down the road, street or highway.

Author Bio: Kirk I Inkster Edmonton Alberta 2011 Dodge Ram Mega Cab The Godzilla of Heavy Duty Chrysler Pickups Edmonton Fort McMurray 2011 Chrysler Sebring – Derrick Dodge Online

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