- It controls fuel delivery at all engine speeds and varying load conditions. The quantity of fuel for idling and maximum speed is controlled and correct fuel delivery is ensured for all conditions in between these two extremes.
- It ensures that adequate fuel is delivered to the engine when idling to avoid stalling and also to limit the maximum amount of fuel that can be supplied to the injectors to prevent excessive engine speed, but allowing the accelerator pedal to piston the control rod for all other speeds.
In a gasoline engine, the governor is usually placed between the carburetor and the intake manifold. A centrifugal governor is attached to the camshaft by a gear drive. The movement o the flywheel attached to the pivot arms of centrifugal governors is used to control the flow of gasoline m the carburetor, thus controlling the engine speed.
Types of Governors
The governor-used automobile vehicles are of the following three types-
- Mechanical or Centrifugal governor.
- Pneumatic governor.
- Hydraulic governor.
1. Mechanical Governor-
|Simms-type GMV mechanical governor.
Mechanical governors are fitted to large engines on an extension of the pump camshaft. Fig. shows a mechanical governor. It works as follows-
When the engine starts, the weights take up a position to maintain a stable idling speed. As the accelerator pedal is depressed against the spring, the weights move inwards, and since the weights are linked to the control rod, the fuel delivery is increased, and hence the engine speed also increases. The increased engine speed causes the pump camshaft to rotate faster, which moves the weights outward against the action of the control springs, so reducing the fuel delivery until the correct balance has arrived at for a particular engine operating condition. Thus the accelerator does not increase delivery directly but delays the action of the governor. The relative position of governor-weight and control-rod positions, when the engine is at idling and full load position, as shown in this Fig.
|Operation of the mechanical governor.
2. Pneumatic Governor-
|C.A.V pneumatic governor.
Pneumatic governors are most successfully used in small and medium-sized engines. They are sensitive to variations in torque loading and ensure stable idling control. As shown in Fig. With pneumatic induction pipe control, the air supply at light loads is made by a butterfly valve placed in a choke. This valve is directly operated by the accelerator pedal. The throttle unit is placed between the air cleaner and the entry to the inlet manifold, which results in reduced air pressure at the end of induction. Injection then takes place into less dense air than with unrestricted induction and the control thus becomes quantity rather than quality control. The fuel injection is controlled by the depression at the choke to a diaphragm chamber mounted on the end of the injection pump. The diaphragm plate is mounted on the end of the control rack of the pump. It is pushed to the full load position (to the right) by the main control spring. Again the increased depression at the throttle, arising when the accelerator pedal is released, will pull the diaphragm and control rod to the left, thus reducing the fuel supply.
|Pneumatic governor with venturi control.
An auxiliary spring is also used to balance the height depression at idling speed. It is brought into action progressively by the action of a cam.
3. Hydraulic Governor-
Hydraulic governors eliminate the high mechanical forces bearing loads and possible torsional vibrations in the drive and hence they are preferred over mechanical governors. In a mechanical governor, the operative agent is the centrifugal force that governs the speed. In a hydraulic governor, it is the pressure difference across an orifice required to pass the oil flow from a positive oil pump driven by the engine.
The pressure difference varies as the square of the engine speed, and it is determined at equilibrium by the pressure of the driver’s foot on the accelerator pedal.
A hydraulic governor, like a mechanical governor, is an all-speed governor, i.e., the governor is in control throughout the whole speed range from idling to the maximum. The injection pump control rack is operated by the governor and not directly by the accelerator pedal. The governor automatically makes the necessary adjustments to the supply to maintain the speed, no matter what the power requirements may be from moment to moment.
What is Governor in the engine?
An engine governor is a device that regulates the speed of an engine. It is an essential component in engines that require precise control over their speed to maintain proper operation. The governor works by monitoring the engine speed and making adjustments to the fuel and air supply as needed to maintain a consistent speed.
In simple terms, a governor is like cruise control in a car. It helps maintain a constant speed, so the engine can operate efficiently without overworking or underworking. The governor helps to protect the engine from damage due to high or low speeds, and it ensures that the engine runs smoothly and reliably.
Governors have been used in engines for many years. The first governors were mechanical devices that used flyweights and springs to regulate the engine speed. These early governors were simple and effective, but they had some limitations. They were sensitive to changes in load, and they could be affected by changes in the environment, such as changes in temperature or altitude.