Vacuum switch
Encyclopedia
Prior to effective engine control unit
computers, engine vacuum was used for many functions in an automobile
. Vacuum switches were employed to regulate this flow, and were commonly controlled by temperature, solenoid
s, mechanically, or directly. They operated vacuum motors, other vacuum switches and other devices.
The internal combustion engine
in a common automobile produces almost 20 inches (51 cm) of vacuum, and this pressure differential may be harnessed for many uses. Engine vacuum is also the best direct source of information on the engine's load. Most delay valves have a one-way function, where there is either no restriction or no movement in one direction.
is a valve with a small orifice, which delays a vacuum signal. These are commonly used in automobiles to alter the behavior of a vacuum signal. Delay valves are usually color-coded to their function.
at high engine temperatures to promote cooler idling. As emissions controls expanded, it gained many other uses.
They commonly have between two and five vacuum ports.
that ultimately selects cool or preheated air. This valve is usually open on one side to the air space within the air filter, and is both temperature controlled, and bleed style. Its function is to keep the air going in to the carburetor above a certain temperature to prevent icing.
system.
.
(PCV) is a one-way valve that ensures continual refreshment of the air inside the engine's crankcase.
They are commonly found as window and HVAC controls.
Engine control unit
An engine control unit is a type of electronic control unit that determines the amount of fuel, ignition timing and other parameters an internal combustion engine needs to keep running...
computers, engine vacuum was used for many functions in an automobile
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
. Vacuum switches were employed to regulate this flow, and were commonly controlled by temperature, solenoid
Solenoid
A solenoid is a coil wound into a tightly packed helix. In physics, the term solenoid refers to a long, thin loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electric current is passed through it. Solenoids are important because they can create...
s, mechanically, or directly. They operated vacuum motors, other vacuum switches and other devices.
The internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
in a common automobile produces almost 20 inches (51 cm) of vacuum, and this pressure differential may be harnessed for many uses. Engine vacuum is also the best direct source of information on the engine's load. Most delay valves have a one-way function, where there is either no restriction or no movement in one direction.
Types
There are several common types of vacuum switches. Many are completely useless outside of their exact designed role.Check valve
A valve that only allows the vacuum signal to move in one direction. Often used with vacuum reservoirs.Delay valve
A vacuum delay valveVacuum delay valve
A vacuum delay valve is a valve with a small orifice, which delays a vacuum signal. These are commonly used in automobiles to alter the behavior of vacuum switches, vacuum motors, and other vacuum devices....
is a valve with a small orifice, which delays a vacuum signal. These are commonly used in automobiles to alter the behavior of a vacuum signal. Delay valves are usually color-coded to their function.
Coolant temperature override
Also referred to as a Temperature Vacuum Switch (TVS) or Thermal Vacuum Valve (TVV). The CTO switch measures coolant temperature, usually from a passage in the intake manifold. It was commonly used starting in the 1960s for switching the vacuum advance from ported vacuum to manifold vacuumManifold vacuum
Manifold vacuum, or engine vacuum in an internal combustion engine is the difference in air pressure between the engine's intake manifold and Earth's atmosphere....
at high engine temperatures to promote cooler idling. As emissions controls expanded, it gained many other uses.
They commonly have between two and five vacuum ports.
Thermostatically-controlled air cleaner system
The factory air cleaner on carbureted vehicles has a switch controlled by a bi-metallic stripBi-metallic strip
A bimetallic strip is used to convert a temperature change into mechanical displacement. The strip consists of two strips of different metals which expand at different rates as they are heated, usually steel and copper, or in some cases brass instead of copper. The strips are joined together...
that ultimately selects cool or preheated air. This valve is usually open on one side to the air space within the air filter, and is both temperature controlled, and bleed style. Its function is to keep the air going in to the carburetor above a certain temperature to prevent icing.
Non-linear vacuum regulator
A NLVR regulates vacuum signal so it is between two vacuum source levels. As one signal increases the other regulator valve switches to another vacuum source.Bleed valve
A bleed valve controls a metered orifice that adjusts to allow air into the line to weaken a vacuum signal. They are commonly controlled by coolant temperature or under hood air temperature, but may be part of the HVACHVAC
HVAC refers to technology of indoor or automotive environmental comfort. HVAC system design is a major subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer...
system.
Vacuum booster
A vacuum booster uses one vacuum signal, usually ported, to control another signal, usually manifold, that is stronger. It may also use a venturi effectVenturi effect
The Venturi effect is the reduction in fluid pressure that results when a fluid flows through a constricted section of pipe. The Venturi effect is named after Giovanni Battista Venturi , an Italian physicist.-Background:...
.
Positive crankcase ventilation valve
The positive crankcase ventilationPCV valve
A crankcase ventilation system is a way for gases to escape in a controlled manner from the crankcase of an internal combustion engine. A common type of such system is a positive crankcase ventilation system, the heart of which is a PCV valve—a variable-restriction valve that can react to changing...
(PCV) is a one-way valve that ensures continual refreshment of the air inside the engine's crankcase.
Vacuum electrical switch
A vacuum switch that turns an electrical connection on or off. Used for early electronic control modules to determine engine load or function.Manual vacuum switch
Operator controlled switches were often used to control vacuum powered devices before the advent of robust automotive electrical systems or reliable mechanical linkages. They consisted of a variety of shapes, sizes, and configurations much like electrical switches.They are commonly found as window and HVAC controls.
Electrical Switches
The term "vacuum switch" can also refer to a specialized type of electrical switch in which the contacts are enclosed in a vacuum envelope. This allows the switching of very high voltages with a compact switch, while preventing arcing across the contacts.See also
- Manifold vacuumManifold vacuumManifold vacuum, or engine vacuum in an internal combustion engine is the difference in air pressure between the engine's intake manifold and Earth's atmosphere....
- List of automotive vacuum devices
- Automobile accessory power