Korea University of Technology and Education School of Mechanical Engineering Prof. Dongho Shin

Basic Operation Basic parts of the Starting System. Battery - Supplies the energy Switch - Activates Circuit Solenoid - Engages starter motor to flywheel. Starting motor - Drives the flywheel to crank the engine.

Basic Operation When the starter switch is activated a small amount of current flows from the battery to the solenoid. The solenoid performs two functions. Engage the pinion gear with the flywheel. Close the contacts between the battery and the starter motor.

Basic Operation The starter motor takes the electrical energy from the battery and converts it into rotational energy to crank the engine.

Starter motor Remember, if a conductor has current passing through it there will be a magnetic field formed. A permanent magnet has field lines between the two poles When a current carrying conductor is placed in the permanent magnet field, there will be a force exerted on the conductor. Since the current flow is in opposite directions in the coil one side will be forced up and the other side will be forced down producing torque.

Field Frame Pole Pieces The pole pieces in the field frame assembly can be compared to the ends of the magnet. The space between the poles is the magnetic field.

Field Winding If a wire, called a field winding, is wrapped around the pole pieces and current is passed through it, the strength of the magnetic field between the pole pieces increases.

Armature If we feed current through a loop of wire, a magnetic field is also formed around the wire.

Principles If the loop of wire is placed in the magnetic field between the two pole pieces and current is passed through the loop, a simple armature is created. The magnetic field around the loop and the field between the pole pieces repel each other causing the loop to turn. We can add more loops to make the motor more powerful.

Commutator and Brushes A commutator and brushes are used to keep the motor spinning by controlling the current passing through the wire loop. The commutator acts as the sliding electrical connection between the wire loop and the brushes. The commutator has several segments that are insulated from each other.

Basic Operation The brushes ride on top of the commutator and carry current to the spinning wire loops As the loops rotate away from the pole shoes, the commutator segments change the electrical poles between the brushes and wire loops. This reverses the magnetic field around the wire loop so that it may again be pulled by the other pole piece. This constant changing electrical connection keeps the motor spinning.

Basic Operation Several loops of wire and a segmented commutator increase motor power and smoothness. Each wire loop is connected to its own segment on the commutator. As the motor spins,many wire loops contribute to the motion to produce a constant and smooth turning force.

Armature Commutator windings Pinion Bearing A starter must produce a tremendous amount of torque, therefore a system to support and strengthen the magnetic field is needed. The armature consists of the armature shaft, armature core, commutator, and windings.

Field Windings The field winding is stationary wire wrapped in a circular shape, which creates a strong magnetic field around the armature. When current flows through the field winding, the magnetic field between the pole pieces becomes very strong. (5-10 times more than a permanent magnet) This field acts against the field developed by the armature thus the motor spins with great power.

Motor Circuit The field windings and the armature are usually wired together so that all of the current passes through both the field and the armature. The brushes are a means of carrying the current from the external circuit (field) to the internal circuit (windings). The brushes are contained in brush holders and normally half are case ground.

Motor Drives The electrical work created by the motor is transformed to mechanical work by motor drives. Motor drives must transfer the motor torque, engage the flywheel, and disengage from the flywheel. Some motors do not produce enough torque to directly crank the engine. It is often necessary to use gears ratios from 15:1 up to 20:1 to increase torque at the flywheel.

Motor Drive Mechanisms Motor drive mechanisms must engage the flywheel during cranking and disengage after engine start. The gear that engages the flywheel is called the pinion gear and the gear on the flywheel is called the ring gear. How the pinion gear engages with the ring gear depends on the drive used.

Motor Drive Mechanisms Motor drives come in two types inertia drive overrunning clutch Inertia drives are actuated by rotational force by the armature. The drive sleeve has very course threads cut into it. The pinion moves up these threads until it engages the ring gear.

Motor Drive Mechanisms The overrunning clutch requires a lever to move the pinion to mesh with the ring gear. When the solenoid is energized the plunger is pulled, pulling in the lever. The lever rotates on the pivot, pushing out the forks. The forks in turn push the pinion and clutch, engaging the pinion with the ring gear.

Overrunning clutch The overrunning clutch locks in one direction and releases in the other. This allows the pinion to turn during starting but also allows the pinion to “freewheel” after start-up. The overrunning clutch consists of rollers held in position by springs against a roller clutch. The roller clutch has tapered ramps that allow the roller to lock the pinion to the shaft during cranking.

Overrunning clutch The torque travels through the clutch and is transferred by the rollers to the pinion gear. The engine starts and the speed of the pinion exceeds the speed of the armature shaft, the rollers are pushed down the ramps and permit the pinion to rotate independently of the armature shaft.

Circuit Controls The starting circuit contains control and protection devices to allow the intermittent operation of the starter and to prevent operation during some machine modes for safety reasons. The circuit consists of a battery, cables and wires, key switch, neutral/clutch safety switch, starter relay, starter solenoid.

Circuit Controls Battery Cables and wires Starter relay Supplies all of the energy during start-up. Must be fully charged to operate properly. Cables and wires High current flows to the starter thus the cables are very large. Starter relay An electrical switch between the key switch and the solenoid. Starter relay

System operation When the ignition switch is closed, battery current flows in tow directions. Current flows from the battery to the start switch and then through the pull-in winding, field winding, armature, brushes, and to ground. The activation of the pull-in winding and the hold-in winding produces magnetic force. This force pulls the plunger, engaging the overrunning clutch and pinion toward the flywheel.

System operation When the plunger is pulled in it also closes the solenoid contacts. At this point the pinion is engaged with the ring gear and current is allowed to flow through the solenoid and to the field windings, armature, brushes, and to ground. The starter motor is energized, the pinion is engaged, the armature begins to turn and the engine begins to crank.

System operation As soon as the engine starts, the ring gear rotates faster that the starter. The overrunning clutch breaks the mechanical link between the engine and the starter. When the ignition switch is release current stops flowing, a spring pushes the solenoid plunger back in place disengaging the pinion and the solenoid contacts.

STARTER MOTOR의 구조 종류 : 습동식 모터(전자석 클러치에 의해 피니언 기어 습동) Reduction 식 모터(감속 기어를 통해 피니언 기어에 전달) 구조(기초 Fig 그림(a) p .171) 아마추어(정류자+아마추어 코일+코어) + 필드코일(영구자석대용) Magnetic Switch(접점+홀딩코일+풀링코일+플런저) ` + 드라이브장치(피니언기어+드라이브 레버+릴리스 베어링)

1. Magnetic Switch의 코일역할(기초 p.172~3 그림 a,b) 역할 : 시동 모터에 대 전류 코일   접점 ON   시동 Motor 전원 인가 전류도통   Plunger 전자석화 코일의 역할 Coil = 풀링코일(O.5옴 24A)+홀딩코일(1옴 24A) ->초기 접점 ON 시 대전류 필요 시동 모터가 회전시 -> 작은전류 From H.C

시동 모터의 내부 회로 작동(기초 P174. 그림 a,b,c) Battery(+) 0----0M.S(B) 연결 Start Switch 0----0M.S(S) 연결 작동순서 Start switch on  B단자에 공급되어 있던 12V전원 S단자에 공급 H.C&P.C 전류 흐름  Plunger 전자석화  M.S 접점 ON  M단자&S단자 전위동일  홀딩코일에만 전류 흐름 *스타트 스위치 OFF 시 M단자를 통해 홀딩, 풀링코일에 전원인가 하지만 둘 사이의 권선방향 반대로 인해 자력선 상쇄M.S OFF

시동회로 배터리 E48 0---0시동모터 E46단자 연결 시동모터로 대전류 흐름 M.S의 코일(스타트 솔레노이드)단자 E45는 Start relay의 접점을 거쳐 스타팅 시 배터리의 전원 공급 Where 스타트 릴레이 접점의 전원공급 A/T차량 경우 시동시위치를 거쳐 A/T의 시프트 레 버스위치(Inhibitor Switch)를 거쳐 전원 공급 Start relay 사용 목적 시동스위치 ON시 풀링코일을 거쳐 아마추어로 흐르는 전류와 홀딩코일로 흐르는 전류는 20~50A정도 시동 스위치 OFF시 큰 역기전력에 의한 시동스위치의 접점 손상을 중간에서 맡음