For over a century, the internal combustion engine has reigned supreme in the automotive world, and at the heart of its operation lies a seemingly simple yet crucial component: the ignition coil. While modern vehicles boast sophisticated electronic systems, the fundamental principle of ignition remains rooted in technology pioneered over 100 years ago. But What Do Car Coils Do exactly? In essence, they are the unsung heroes responsible for generating the high-voltage spark needed to ignite the air-fuel mixture in your engine, bringing your car to life. Let’s delve into the fascinating history and intricate workings of these vital automotive parts.
A Look Back: The History of Ignition Coils
The story of the ignition coil begins with Charles Kettering, an American inventor who, around 1910-1911, developed the first practical coil ignition system for mass-produced vehicles. Prior to Kettering’s innovation, ignition systems were less reliable and efficient. His groundbreaking system ingeniously combined the starter motor and ignition into a single electrical system. This system, powered by a battery, generator, and a more comprehensive vehicle electrical system, provided a stable and consistent power source for the ignition coil.
Figure 1: Diagram illustrating the key components of the original Kettering ignition system, highlighting the single coil, distributor, and spark plug wires.
The Kettering system, as depicted in Figure 1, utilized a single ignition coil to produce a high voltage. This voltage was then directed to a rotor arm within the distributor assembly. The rotor arm acted like a rotating switch, sequentially directing the high voltage to a series of electrical contacts – one for each engine cylinder. These contacts, in turn, were connected to the spark plugs via spark plug wires, ensuring that each spark plug received the high voltage in the correct firing order to ignite the fuel-air mixture at precisely the right moment.
The Kettering ignition system rapidly became the industry standard, dominating mass-produced gasoline cars for decades. It remained the primary ignition technology until the rise of electronically switched and controlled ignition systems in the 1970s and 1980s, marking a significant shift towards modern automotive electronics.
The Science Behind the Spark: How Car Coils Work
To understand what car coils do, we need to explore the fundamental principles of electromagnetism that govern their operation. Ignition coils leverage the relationship between electricity and magnetism to generate the extremely high voltages required for spark plugs to function.
Creating a Magnetic Field: The Foundation of Coil Function
When an electric current flows through a conductive wire, such as the windings within an ignition coil, it generates a magnetic field around the coil (Figure 2). This magnetic field is essentially stored energy, which can be converted back into electrical energy when needed.
Figure 2: Illustration demonstrating how an electric current passing through a wire coil generates a surrounding magnetic field, a core principle of ignition coil operation.
Initially, when the electric current is switched on, the current flow rapidly increases to its peak level. Simultaneously, the magnetic field expands and strengthens, reaching its maximum intensity when the electric current stabilizes. Conversely, when the electric current is switched off, the magnetic field collapses inwards towards the coil.
The strength of this magnetic field is influenced by two primary factors:
- Current Strength: Increasing the electrical current flowing through the coil strengthens the magnetic field.
- Number of Windings: A higher number of wire windings in the coil results in a stronger magnetic field.
Inducing Electric Current: Harnessing the Magnetic Field
A crucial principle at play is electromagnetic induction. If a coil of wire is exposed to a changing magnetic field, an electric current is induced within the coil. This phenomenon, known as ‘inductance’, is the key to voltage transformation in ignition coils.
This effect can be simply demonstrated by moving a permanent magnet near a coil of wire (Figure 3). The movement of the magnet, and thus the changing magnetic field, induces an electric current in the wire.
The magnitude of the induced voltage depends on:
- Rate of Change: The faster the magnetic field changes (or moves), and the greater the change in its strength, the higher the induced voltage.
- Number of Windings: Increasing the number of windings in the coil increases the induced voltage.
Mutual Inductance and Voltage Transformation: Stepping Up the Voltage
In ignition coils, a process called ‘mutual inductance’ is employed to achieve the dramatic voltage increase needed for spark plugs. This involves two coils of wire positioned close to each other: the primary winding and the secondary winding.
When an electric current is applied to the primary winding, it creates a magnetic field that also surrounds the secondary winding (Figure 5). When the current to the primary winding is abruptly switched off, the magnetic field collapses. This collapsing magnetic field induces a voltage in both the primary and secondary windings.
For ignition coils, the secondary winding is designed with significantly more windings than the primary winding. Consequently, when the magnetic field collapses, a much higher voltage is induced in the secondary winding compared to the primary winding (Figure 6). This voltage amplification is known as ‘transformer action’.
Figure 6: Diagram highlighting the difference in windings between primary and secondary coils, illustrating how a higher number of secondary windings leads to increased voltage output.
Typically, a primary winding in an ignition coil may have 150 to 300 turns of wire, while the secondary winding can contain 15,000 to 30,000 turns – approximately 100 times more.
When the vehicle’s electrical system (usually 12 volts) is applied to the primary winding, it creates the initial magnetic field. When a spark is needed, the ignition system cuts off the current to the primary winding, causing the magnetic field to collapse rapidly. This collapsing field induces a voltage of around 200 volts in the primary winding, but due to the much larger number of windings in the secondary coil, a voltage approximately 100 times greater – around 20,000 volts – is generated in the secondary winding.
Therefore, by leveraging mutual inductance and the difference in windings between the primary and secondary coils, ignition coils effectively transform a low voltage (12V) into the extremely high voltage (20,000V+) required to create a spark across the spark plug gap within the engine cylinder. To further enhance efficiency, the primary and secondary windings are typically wrapped around an iron core, which concentrates and strengthens the magnetic field.
Modern Ignition Coils: Continuing Innovation
Even in modern vehicles with advanced electronic ignition systems, the fundamental principle of what car coils do remains unchanged. While distributors have largely been replaced by coil-on-plug or coil-near-plug designs for increased efficiency and control, the core function of generating high voltage through electromagnetic induction persists. DENSO, a leader in direct ignition technology, continues to innovate in ignition coil design and manufacturing, providing high-quality aftermarket solutions. You can find out more about the types of DENSO Ignition Coils and their benefits to further explore the evolution of this essential automotive component.
In conclusion, car coils are indispensable components in gasoline engines. They act as voltage transformers, utilizing the principles of electromagnetism to convert low voltage into the high voltage sparks needed to ignite the air-fuel mixture, enabling combustion and ultimately, powering your vehicle. Understanding what car coils do provides valuable insight into the intricate workings of your car’s engine and the legacy of automotive innovation.
