Automotive starting system structure principle

I. Definition and Working Principle of Automobile Starting System

To transition an engine from a stationary state to a running state, an external force must first rotate the engine crankshaft, causing the pistons to reciprocate. The combustible mixture in the cylinders burns and expands, doing work and pushing the pistons downwards, thus rotating the crankshaft. Only then can the engine run automatically, and the working cycle can proceed automatically. Therefore, the entire process from the crankshaft starting to rotate under external force to the engine automatically idling is called engine starting. The device required to complete the starting process is called the engine starting system.

1. Function: To start a stationary engine.
2. Composition: Consists of a starter motor and auxiliary devices.

II. Component Composition

The starting system is a starter equipped with a small high-speed motor with a drive gear, which starts the stationary engine and puts it into automatic operation. It includes the starter, starter relay, and anti-theft system.

The automotive starting system mainly consists of a starter motor and a starting control circuit.

The starter motor is used to start the engine. It mainly consists of three parts: the motor, the transmission mechanism (or meshing mechanism), and the starter switch.

1. Engine Starting Principle To transition the engine from a stationary state to a working state, an external force must be used to rotate the engine crankshaft, causing the cylinder to draw in (or form) a combustible mixture, which then burns and expands, allowing the working cycle to proceed automatically. The entire process from the crankshaft starting to rotate under external force until the engine automatically idles is called engine starting. There are many methods for starting an engine. The commonly used electric motor starting method for automotive engines uses an electric motor as mechanical power. When the gear on the motor shaft meshes with the gear ring around the engine flywheel, power is transmitted to the flywheel and crankshaft, causing them to rotate. The electric motor itself uses a battery as its energy source. Currently, the vast majority of automotive engines use electric motor starting.
2. Starter Motor Composition A starter motor generally consists of three parts: (1) A DC series-wound electric motor, whose function is to generate torque. (2) The transmission mechanism (or engagement mechanism) functions to: during engine starting, engage the starter drive gear with the flywheel ring gear to transmit starter torque to the engine crankshaft; and after engine starting, allow the drive gear to slip and automatically disengage from the flywheel ring gear. (3) The control device (i.e., switch) is used to connect and disconnect the circuit between the starter and the battery. In some cars, it also connects and disconnects the additional resistance of the ignition coil.
3. Function of the starter: The function of the starter is to convert the electrical energy of the battery into mechanical energy, and then use the transmission mechanism to start the engine.
4. Classification of starters: Among the three components of various starters, the electric motor generally has no essential difference, but the control method and the engagement method of the transmission mechanism differ greatly. Therefore, starters are classified according to the different control methods and the engagement methods of the transmission mechanism. 5. According to the different control methods, starters can be divided into: (1) mechanical control type (2) electromagnetic control type. According to the meshing method of the transmission mechanism, starters can be divided into: a. inertial meshing type b. forced meshing type c. armature moving type d. gear moving type e. coaxial starter type. In addition to the above, there are permanent magnet starters with permanent magnet poles, and deceleration starters with internal reduction gears, etc. The model of the starter is: (1) QDJ indicates deceleration starter; QDY indicates permanent magnet starter (including permanent magnet deceleration starter), J and Y respectively indicate “deceleration” and “permanent”. (2) Voltage level: 1-12V; 2-24V (3) Power level (4) Variation code (5) Design serial number

The control device of the automobile starter includes components such as electromagnetic switch, starter relay and ignition starter switch, among which the electromagnetic switch is made together with the starter.

I. Electromagnetic switch 1. Structural characteristics of electromagnetic switch: The electromagnetic switch is mainly composed of two parts: electromagnet mechanism and motor switch. The electromagnet mechanism consists of a fixed iron core, a movable iron core, an attraction coil, and a holding coil. The fixed iron core remains stationary, while the movable iron core can move axially within a copper sleeve. A push rod is fixed to the front end of the movable iron core, and a switch contact plate is mounted at the front end of the push rod. The rear section of the movable iron core is connected to a shift fork using an adjusting screw and a connecting pin. A return spring is installed outside the copper sleeve to reset the movable iron core and other movable parts. The terminal arrangement of the electromagnetic switch wiring is shown in Figure 2. Electromagnetic switch working principle: When the magnetic flux generated by the attraction coil and the holding coil is in the same direction, their electromagnetic attraction forces are superimposed, attracting the movable iron core forward until the contact plate at the front end of the push rod connects the electric switch contacts, thus activating the motor’s main circuit. When the magnetic flux generated by the attraction coil and the holding coil is in opposite directions, their electromagnetic attraction forces cancel each other out. Under the action of the return spring, the movable iron core and other movable parts automatically reset, the contact plate disconnects from the contacts, and the motor’s main circuit is disconnected.

II. Starting Relay The simplified structure of the starting relay is shown in the upper left corner of the figure. It consists of an electromagnet mechanism and a contact assembly. The coil is connected to the ignition switch terminal and the ground terminal “E” on the housing. The fixed contact is connected to the starter terminal “S”, and the movable contact is connected to the battery terminal “BAT” via a contact arm and bracket. The starting relay contacts are normally open. When the coil is energized, the relay core generates electromagnetic force, causing the contacts to close, thereby connecting the relay-controlled attracting coil and holding coil circuits.

III. Starting Circuit of Dongfeng EQ1090 Vehicle The Dongfeng EQ1090 vehicle uses the QD124 starter motor, an electromagnetically controlled strong-meshing starter motor with a rolling one-way clutch, an 11-tooth drive gear, and a rated power of 1.5kW. Its starting circuit, as shown in the figure, includes a control circuit and a starter motor main circuit. 1. Control Circuit The control circuit includes the starting relay control circuit and the starter motor electromagnetic switch control circuit. The starter relay control circuit is controlled by the ignition switch, and the controlled object is the relay coil circuit. When the ignition switch is turned on to the start position, current flows from the battery positive terminal through the starter power terminal to the ammeter, then from the ammeter through the ignition switch, and back to the battery negative terminal via the relay coil. This generates a strong electromagnetic force in the relay core, causing the relay contacts to close and activating the starter solenoid switch control circuit. 2. The main circuit is: Battery positive terminal → Starter power terminal → Solenoid switch → Excitation winding → Armature winding → Ground → Battery negative terminal. This generates electromagnetic torque in the starter motor, starting the engine.

III. Engine Starting Methods

(1) Engine Starting: The engine needs external force to rotate the crankshaft until a combustible mixture is formed in the cylinder and ignites, so that it can automatically start the working cycle and enter the working state.
(2) Starting Process: The entire process from when the engine is stationary to when it enters the working state.
(3) Starting Time: The time required from starting to running on its own. Electric start <5s, interval 15s, manual start <30s.
(4) Starting Speed: The minimum speed required for starting under certain environmental conditions. Diesel engine 100~300r/min, gasoline engine 50~70r/min.
(5) Starting Methods:

• Manual start: Crank the flywheel by hand. Used for small-power engines.
• Electric start: Battery as power source, series-wound DC motor.
• Diesel engine starting with gasoline engine: Used for starting high-power diesel engines.
• Compressed air starting: High-pressure air is sent into the cylinder in the working order to push the piston and drive the crankshaft to rotate.

IV. Starting Process

1) Starter Switch On ① Starter Relay Function: The coil is energized, the contacts close, connecting the attraction coil and protection coil circuits. Current Path: Battery positive terminal → Ignition switch → Starter relay coil → Ground → Battery negative terminal ② Attraction Coil and Protection Coil Attraction Coil Current Path: Battery positive terminal → Starter relay contact → Starter motor terminal → Attraction coil → Attraction coil terminal → Starter motor switch terminal → Starter motor field winding → Starter motor armature winding → Ground → Battery negative terminal Protection Coil Current Path: Battery positive terminal → Starter relay contact → Starter motor terminal → Protection coil → Ground → Battery negative terminal ③ Drive Gear Meets Flywheel The attraction coil and protection coil generate magnetic fields in the same direction. The movable iron core moves to the left, driving the drive gear to the right via the shift fork, and the drive gear meshes with the flywheel. ④ Start Engine The movable iron core moves to the left, causing the contact plate to connect the motor switch terminal, connecting the starter motor main current circuit, starting the starter motor, and starting the engine. 1) Starter motor main current path: Battery positive terminal → Starter motor switch terminal 1 → Main contact plate → Starter motor switch terminal 2 → Starter motor field winding → Starter motor armature winding → Ground → Battery negative terminal

2) Starter switch open:

• Starter relay: Coil de-energized, contacts open.
• Attraction coil and protection coil: Circuit connected by motor switch, generating magnetic fields in opposite directions that weaken each other, moving iron core returns to its original position.
• Drive gear separates from flywheel: Moving iron core to the left drives drive gear to the right via shift fork.
• Contact plate disconnects motor switch: Cuts off starter motor circuit.

V. Common Faults in Automotive Starting Systems

Automotive starting systems mainly consist of a starter motor and starting control circuit. Faults can be mechanical or electrical. Common fault phenomena include starter motor not turning, starter motor operating weakly, starter motor spinning without engine starting, starter motor running continuously after engine start, drive gear and flywheel ring gear not meshing and abnormal noise, etc. I. Starter Motor Not Turning A starter motor not turning generally has the following causes: 1. The battery is severely depleted, resulting in insufficient power and preventing it from turning. 2. Poor contact at the wiring connections; vehicle bumps can cause loose connections or oxidation and contamination at the connections. 3. A damaged starter switch. 4. A faulty relay. If the starting circuit contains a starter relay or combination relay, a faulty relay will cause the starter motor not to turn. Oxidation and contamination of the relay contacts prevent the electromagnetic switch circuit from connecting; excessively large contact gaps or short circuits/open circuits in the relay coil can also prevent the relay contacts from closing, thus breaking the electromagnetic switch circuit. 5. Starter motor faults include electromagnetic switch failure, commutator oxidation, poor brush contact, and open or short circuits in the armature winding and field winding.

Electromagnetic switch failures are mainly due to oxidation of the contacts caused by strong current, resulting in poor contact.

Motor failures prevent the motor from forming a complete internal circuit, thus preventing the starter motor from turning.

II. Weak Starter Motor Operation A weak starter motor operation is likely due to the following reasons: 1. Insufficient battery power. 2. Poor contact at wiring connections. 3. Starter motor malfunction, primarily a DC motor malfunction.

A short circuit between turns in the armature winding or field winding weakens the armature current and magnetic field strength, resulting in a weak starter motor operation.

Commutator contamination, insufficient brush spring force, or excessive brush wear increases circuit resistance and reduces motor torque. Overly tight bearings increase mechanical losses, all of which can lead to a weak starter motor operation.

III. Continuous Starter Motor Operation After Engine Startup Continuous starter motor operation indicates that the solenoid switch contact plate is constantly in contact with the two main terminals. There are three possibilities: 1. The solenoid switch contact plate is fused to the contacts. 2. The drive fork spring is too soft or broken, preventing the moving iron core from resetting to its original position. 3. The starting relay or combination relay contacts are fused, keeping the two main terminals of the solenoid switch constantly connected.

IV. The starter motor spins freely, and the engine cannot start. The cause of the fault is slippage of the one-way clutch.

V. The drive gear and flywheel ring gear cannot mesh and there is abnormal noise. The fault is at the meshing point of the two teeth, and there are three possibilities: 1. The drive gear of the one-way clutch is damaged. 2. The flywheel ring gear is damaged. 3. The starter motor mounting bolts are loose, preventing the two teeth from meshing properly.

VI. A brief discussion on the current status and development trend of automotive starter/generator integration technology

Automotive starters and generators are two independent electrical devices used for starting and generating electricity. Starter/generator integration combines the functions of starting and generating electricity into one, and has the advantages of large starting torque under low battery current, large generator power, high efficiency, small size, and suitability for installation within the engine speed range. 1 System structure composition and control principle (1) The starter/generator integration system is mainly composed of a motor, a controller, and other compatible components. Electric motors are used for starting and generating electricity. Currently available electric motors include asynchronous motors, permanent magnet motors, switched reluctance motors, and claw pole motors, with asynchronous motors with squirrel-cage armatures being the most ideal. The controller regulates and controls the motor’s function switching and reliable operation. Due to the large variations in vehicle operating conditions, starting requirements…

Automotive starters are developing towards miniaturization and lightweighting, information-based design and manufacturing, and automated performance testing. This article introduces the development direction of starters and the basic principles of reduction gear starters. It also elaborates on the latest progress in the research and development of automotive starters using computer-aided technology, both domestically and internationally. Based on the current situation of Chinese enterprises, new research topics are proposed.

The starter motor (starter motor) drives the engine to operate using the current from the battery.

The generator generates current through the engine’s operation to charge the battery and supply power to the entire vehicle.