An automobile electric starter is a collector electric motor with auxiliary elements designed to start an internal combustion engine. The electric starting system was invented over 100 years ago and has not changed dramatically since then. Almost all equipment with internal combustion engines is equipped with starters - cars, tractors, walk-behind tractors, trucks, motorcycles, garden lawn mowers, mobile generators. This material is devoted to the design and operational features of the electric starter.
The history of the invention of the electric starter
The first cars with an internal combustion engine were not equipped with electric starters. To start them, a lever was provided that had to be inserted into the crankshaft, turned with force, and after starting the engine, pulled it out in a timely manner. Such a "system" was extremely inconvenient, unbearable for many, and traumatic. In 1910, a crooked starter killed a close friend of Henry Martin Leland, the founder of the Cadillac automobile brand.
The death of a friend motivated a talented engineer, and he set out to make starting a car engine more convenient, easier and, most importantly, safe. But he did almost nothing. Together with his engineers, he created something similar to a starter. But it was a very bulky device that was not suitable for practical use.
Then he turned to Charles Kettering, who was an inventor, engineer, entrepreneur and owner of 186 patents. Already in 1912, the first starters appeared on Cadillac cars. Later, the invention migrated to many other cars and is still indispensable.
Typical starter design
The electric engine start system is a set of equipment that allows you to start the engine from the driver's seat using the energy stored in the battery. It exists in different configurations, differing in the design features of individual components and mechanisms. Within the framework of this material, the most common ICE starting system is considered - a geared starter with a freewheel and a traction relay.
The system consists of the following components:
- Gear motor with freewheel.
- Traction relay.
- Signal chain.
- Power wires.
Signal circuit - serves for convenient control of the engine start system from the driver's seat. Consists of one signal wire, secondary relay and closing device. The latter can be an ignition switch or a button. During activation of the system, voltage is supplied from the battery to the traction relay through the signal wire. A secondary relay is needed so that the contacts in the ignition switch do not burn.
Battery is a starter-type storage acid battery (how it differs from traction batteries). The main parameter is the starting current. This is the main criterion for choosing a battery for a car. Contrary to popular belief, battery capacity is not the main characteristic of a starter battery. Although these two parameters depend equally on the size and type of battery.
Power wires - are used to supply starting current to the starter. Since its value reaches hundreds of amperes, these wires have a serious cross section. The minus power supply is fed to the starter through a common ground. This is usually a thick wire connected to the engine or car body. Plus power supply is supplied through a separate wire, which is connected to the corresponding output on the traction relay.
The main components of the electrical system for starting an internal combustion engine are an electric motor and a traction relay. We will consider their device and principle of operation in more detail.
The device of a geared electric motor with a freewheel
This part of the starter consists of the following elements:
- Armature (36) with windings and collector (32).
- Brush assembly (31) with four brushes that are constantly pressed against the collector by springs.
- Permanent magnets (34). Some starters use a stator - windings that create a magnetic field when an electric current flows.
- Motor power supply wire (enters the housing from terminal 23).
- Reducer (not shown in this image) - serves to reduce the speed of rotation of the starter shaft and a significant increase in torque.
- Bendix (7) - serves to transmit torque from the starter armature to the ICE flywheel. It is engaged with the flywheel crown by means of a gear (4). After starting, it allows the internal combustion engine and electric motor to rotate independently of each other.
- The body (30) is sealed, fastened to the engine through the flange with two or three bolts.
The armature and driven shaft of the electric motor rotate on bronze bushings (2, 26). Thanks to the plain bearings, the starter turns briskly (if it turns hard, sluggishly - read this material). Bendix can move on the shaft due to the worm gear (not shown in the figure, but there is a gear with spiral teeth). The movement of the bendix forward is limited by the retaining ring (3).
Traction relay device
Solenoid relay (how to check it) consists of the following main elements:
- Anchor (14) with spring (13).
- Stem (17).
- Retracting winding (17).
- Holding winding (16).
- Contact plate (21).
- Power contacts (23).
- Signal contact. It is not shown in the figure, but is usually located next to the power bolts on the back of the traction relay.
In most designs, the traction relay is attached to the starter housing and forms one assembly with it. The anchor of the retractor acts on the bendix by means of a lever (11).
The principle of the starter
The electric starter works according to the following principle:
- In the initial state, the plus from the battery is constantly supplied to the open contact of the ignition switch and one of the power contacts of the solenoid relay.
- When the driver turns the ignition key to the "start" position (or presses the engine start button), power comes from the battery through the ignition switch and a secondary relay to the retractor winding.
- The retracting winding generates a powerful electromagnetic field that acts on the armature of the traction relay. As a result, the armature moves inside the device, overcoming the force of the springs.
- Moving, the armature presses on the rod with the contact plate, due to which it closes the power contacts. Plus from the battery passes through this plate and enters the brushes of the electric motor. The latter starts to rotate.
- At the same time, the holding winding is activated, and the retracting winding is deactivated. This is implemented due to a cunning winding connection scheme. When the contact plate closes, electric current flows to the holding winding, bypassing the retracting one.
- At the same time, the anchor moves the bendix forward by means of a lever. Its gear is brought into engagement with the flywheel crown.
- The torque generated by the electric motor is transmitted to the crankshaft of the internal combustion engine.
- After several rotations, the engine starts and begins to rotate faster than the starter shaft.
- Overrunning clutch engages. The rollers inside it are displaced under the influence of centrifugal force and begin to slip. Now the engine flywheel and starter rotate independently of each other.
- Upon hearing the sound of a running engine, the driver releases the ignition key or button.
- The holding winding of the traction relay is de-energized (when it is not completely serviceable, the starter turns off spontaneously ahead of time).
- The armature of the traction relay, no longer held by the magnetic field, returns to its original position under the influence of a spring.
- The contact plate also returns to its original position by a spring (sometimes it is welded to the power contacts, which is why the starter does not turn off after the engine starts). The power contacts open, the starter motor is de-energized and stopped.
- At the same time, the traction relay armature pushes the bendix drive lever. The latter is disengaged from the flywheel and returns to its original position.
- All elements of the starting system return to their original position and remain in it until the next engine start.
If you still have questions about the device and the principle of operation of a car electric starter, ask them in the comments below. I will be happy to answer them personally.