The starter motor, which is responsible forinitiating the engine starting process, connects to the starting battery and the engine usingvarious parts.. Minimum cranking speed of the en
Topic introduction
Introduction
This section introduces the starting systems that can be found in today’s passenger cars
Many components and systems derived from cars are also present in small commercial vehicles, as well as in larger derivatives used in heavy goods and public service vehicles This chapter aims to introduce the main types of starting systems and related technologies, though it can only provide a brief overview of the subject To facilitate further exploration, we include references to additional materials for those interested in delving deeper into specific topics.
The selection of starting units for a vehicle is primarily determined by the availability of existing production models Additionally, creating a specialized starting motor for a specific model is often unjustifiable, even for large vehicle manufacturers.
Recent advancements in technology, especially in electronic control systems, are increasingly merging traditional categories of starting systems This evolution not only enhances the engineering appeal of these systems but also introduces marketing opportunities for a vehicle component that is typically overlooked by consumers until issues arise.
Overall, our group would love to research the starting system based on the Toyota Vios
Definitions
The 2018 Toyota Vios features a sophisticated starting system that includes essential components like the starting battery, starter motor, starting control unit, and starting fuse, all working together for quick vehicle startup Additionally, critical elements such as the combustion chamber, fuel distribution system, air filter, and transmission system are vital for ensuring safe and efficient engine ignition.
The starting battery, a lead-acid type, delivers high current to the starter motor, which is essential for initiating the engine start process and is usually positioned close to the engine The starter motor connects the starting battery to the engine through various components An electronic module known as the starting control unit manages the operations of both the starting battery and the starter motor Additionally, the starting fuse serves as a safety feature, protecting the system from malfunctions, short circuits, and potential damage.
When starting a vehicle, the driver inserts the key and presses the engine start button, which signals the starting control unit to engage the starter motor The effectiveness of this process relies on the battery's charge, the starter motor's speed, and the engine's condition If any problems arise with the starting system, it is recommended that vehicle owners consult skilled technicians at an authorized Toyota service center for necessary repairs and maintenance.
Topic objective
Analyze the starting system of the Toyota Vios 2018
Build a simple starting system model with a key switch
Analyze some common failures and causes on the starting system.
Study method
Overview of starting system
Starting system requirement
An internal combustion engine requires the following criteria in order to start and continue running.
The minimum starting speed (about 100rev/min)
To achieve the initial three operational stages, a minimum starting speed is essential, which is facilitated by the electric starter This capability to reach the required speed is influenced by various factors.
Rated voltage of the starting system.
Lowest possible temperature at which it must still be possible to start the engine. This is known as the starting limit temperature.
Engine cranking resistance In other words, the torque required to crank the engine at its starting limit temperature (including the initial stalled torque).
Voltage drops between the battery and the starter.
Starter-to-ring gear ratio.
Minimum cranking speed of the engine at the starting limit temperature.
It is not possible to view the starter as an isolated component within the vehicle electrical system, as Figure 2.1 shows The battery in particular is of prime importance.
Figure 2 1: Starting system as part of the complete electrical system
When evaluating engine starting requirements, the starting limit temperature is crucial As temperatures drop, the torque produced by the starter diminishes, leading to an increased torque demand to reach the engine's minimum cranking speed.
Figure 2 2: Starter torque and engine cranking torque
Starting system design
The starting system of any vehicle must meet a number of criteria in excess of the eight listed above.
Long service life and maintenance free.
Robust, such as to withstand starting forces, vibration, corrosion and temperature cycles.
Lowest possible size and weight.
The general layout of the starting system is illustrated in Figure 2.3 Determining the minimum cranking speed is crucial, as it significantly varies based on the engine's design and type Typical cranking speed values for engines at a temperature of 20 °C are provided in Table 2.1.
Figure 2 3: Starter system general layout
Engine Minimum cranking speed (rev/min)
Table 2 1: Typical minimum cranking speeds
The standard rated voltage for passenger cars is typically 12 V, while trucks and buses operate on a 24 V system This higher voltage allows for a reduction in the current needed to generate the same power, resulting in less voltage drop across the wiring This is particularly advantageous in commercial vehicles, which often have longer wiring runs compared to passenger cars.
The rated output of a starter motor is assessed on a test bench using a fully charged battery, which experiences a 20% capacity reduction at 20°C, connected via a 1 mΩ resistance cable This setup ensures optimal performance even in challenging conditions The actual output is measured under standard operating scenarios, with the rated power reflecting the battery's power minus copper losses from circuit resistance, iron losses from induced eddy currents, and friction losses.
Figure 2.4 illustrates the equivalent circuit of a starter and battery, highlighting that the starter's output is significantly influenced by line resistance and the internal resistance of the battery A decrease in total resistance leads to an increase in the starter's output.
Figure 2 4: Equivalent circuit for a starter system
When designing a starting system, the positioning of the battery in relation to the starter is crucial, as a closer battery allows for shorter cables, reducing resistance If longer cables are necessary, they must have a larger cross-section to maintain low resistance Additionally, depending on the vehicle's intended use, particularly for off-road applications, specialized sealing arrangements may be required to protect the starter from contaminants Starters designed with these considerations are available, ensuring optimal performance in challenging environments.
To ensure optimal performance, the starter motor must fulfill all specified criteria By consulting figure 2.2, which illustrates the relationship between engine cranking torque and minimum cranking speed, one can ascertain the necessary torque output from the starter motor.
Starter motor manufacturers supply characteristic curves that detail key performance metrics such as torque, speed, power, and current consumption at 20°C The motor's power rating represents the maximum output achievable at this temperature with the recommended battery Additionally, Figure 2.5 illustrates the relationship between the necessary power output of the starter and the engine size.
As a very general guide the stalled (locked) starter torque required per liter of engine capacity at the starting limit temperature is as shown in Table 2.2.
Figure 2 5: Power output of the starter compared with engine size
Engine cylinders Torque per liter [Nm]
Table 2 2: Torque required for various engine sizes
Engines with fewer cylinders require higher torque due to increased piston displacement per cylinder, which significantly influences peak torque values Additionally, the compression ratio plays a crucial role in determining engine performance.
In a four-cylinder 2-litre engine at 20°C, overcoming static friction requires 480 Nm of torque, while maintaining a minimum cranking speed of 100 rev/min necessitates 160 Nm Given a starter pinion-to-ring gear ratio of 10:1, the engine must produce a maximum stalled torque of 48 Nm and a driving torque of 16 Nm, based on the principle that stalled torque is typically three to four times greater than cranking torque.
Torque is converted to power as follows:
P=T ω where P=power, T=torque and ω= angular velocity. ω=2π
At 1000 revolutions per minute, a torque of 16 Nm produces approximately 1680 W of power at the starter Based on the analysis in Figure 2.5, the optimal selection for this application is the starter labeled (e).
The recommended battery would be 55 Ah and 255 A cold start performance.
Starting system circuit
The 2018 Toyota Vios features a complex starting circuit essential for engine ignition, comprising key components such as the starting battery, starter motor, starting control unit, and starting fuse The starting battery, positioned near the engine, supplies the necessary power to the starter motor, which cranks the engine The starting control unit oversees the system's functionality by monitoring signals like battery voltage and engine status, while the starting fuse acts as a safety measure to prevent overloads and short circuits.
For light vehicle engines, the typical cranking current is around 150 A, but it can peak over 500 A to achieve the necessary initial stalled torque To ensure optimal performance, a maximum voltage drop of 0.5 V is recommended between the battery and the starter during operation According to Ohm’s law, this translates to a maximum allowable circuit resistance of 2.5 mΩ with a 12 V supply, although lower resistance values are preferred in most applications Consequently, selecting appropriate conductors is crucial for efficient engine starting.
Types of starter motor
In standard motor vehicle operations, the starter should only engage with the engine ring gear during the initial starting phase A continuous connection would subject the starter to excessive speeds from the engine, leading to immediate damage to the motor.
The inertia type starter motor, used for over 80 years, is gradually becoming obsolete, exemplified by the Lucas M35J starter This four-pole, four-brush model was designed for small to medium-sized gasoline-powered vehicles, drawing 350 A and generating 9.6 Nm of torque Featuring a face-type commutator with axially aligned brush gear, the M35J has its fields earthed to the starter yoke and employs wave coiling technology.
The starter utilizes a small pinion that engages with the flywheel ring gear When activated by a remote relay, the armature rotates the sleeve, which is splined to the armature shaft This rotation causes the pinion to shift and mesh with the ring gear, while the pinion remains stationary due to its inertia and the sleeve's movement.
When the engine starts, the pinion rotates faster than the armature shaft, allowing it to move forward independently Consequently, the pinion disengages from the flywheel and retracts along the sleeve The main spring acts as a buffer during both the initial engagement of the driving torque and the subsequent disengagement of the pinion from the mesh.
The engagement's forceful nature was a major concern for the starter, leading to premature wear of the ring gear and pinion In certain applications, the pinion often failed to mesh properly during cranking as the engine was nearly operational Additionally, contamination from clutch dust frequently caused the pinion to seize, a problem exacerbated by oil applied to the pinion mechanism that attracted more dust and hindered engagement.
Many modern vehicles utilize pre-engaged starters, which ensure full power is delivered only when the pinion is fully engaged with the ring gear, providing a reliable connection These starters prevent premature ejection through a solenoid that maintains the pinion's position, while a one-way clutch within the pinion stops the starter motor from being powered by the engine An example of a commonly used pre-engaged starter is the Bosch EF starter, as illustrated in Figure 2.8.
The pre-engaged starter operates by energizing two windings—hold-on and pull-in—when the key switch is activated, supplying power to terminal 50 on the solenoid The low-resistance pull-in winding allows high current flow, enabling the motor to rotate slowly for smooth engagement As the solenoid generates magnetism, it attracts the plunger, which pushes the pinion into mesh with the flywheel ring gear Once fully engaged, the plunger closes heavy-duty copper contacts, supplying full battery power to the starter motor's main circuit Subsequently, the pull-in winding is deactivated due to equal voltage at both ends, while the hold-on winding maintains the plunger's position as long as the key switch remains engaged.
Upon engine startup and key release, the main supply is cut off, allowing the plunger and pinion to return to their resting positions due to spring tension A lost motion spring on the plunger guarantees that the main contacts disengage before the pinion retracts from its engaged position.
During engagement, the pinion's teeth contact the flywheel's teeth, resulting in tooth-to-tooth abutment This interaction compresses the engagement spring, enabling the main contacts to close Consequently, the motor can rotate under power, allowing the pinion to smoothly slip into mesh.
Figure 2.10 illustrates a sectioned view of a one-way clutch assembly, which plays a crucial role in transmitting the starter's torque to the ring gear When the engine starts, the pinion remains engaged, allowing the free-wheeling gear to protect the starter from excessive speeds This clutch consists of two rollers positioned between a driving and a driven element, with spring-loaded rollers that can either free-wheel in the opposite direction or compress against the springs to lock the components together.
Figure 2 10: One-way roller clutch drive pinion
In the late 1980s, permanent magnet starters emerged in production cars, offering significant advantages such as reduced weight and size compared to traditional starters This makes them a preferred choice for automakers, especially as modern vehicles have limited space for electrical systems The weight reduction from these starters can contribute to improved fuel efficiency Currently, standard permanent magnet starters are suitable for spark ignition engines up to 2 liters in size, with a power rating of approximately 1 kW, exemplified by the Lucas Model M78R/M80R.
The operating principle of modern permanent magnet (PM) starters closely resembles that of traditional pre-engaged starting motors, with the key difference being the replacement of field windings and pole shoes with premium permanent magnets This innovation results in a 15% reduction in weight and a similar decrease in the yoke's diameter Permanent magnets ensure constant excitation, leading to expectations of stable speed and torque characteristics However, due to battery voltage drops under load and low armature winding resistance, the performance resembles that of series wound motors Some designs incorporate flux concentrating pieces or interpoles to enhance this similarity Additionally, advancements in brush construction feature a copper-graphite mix, with two-part brushes that optimize copper content in the power zone and graphite in the commutation zone, ultimately improving starter power and extending service life.
Figure 2 12: Modern permanent magnet starter (Source: Bosch Press)
Permanent magnet motors with intermediate transmission have been designed for applications requiring higher power, enabling the armature to rotate at increased efficiency while maintaining torque through gear reduction These motors, offering power outputs around 1.7 kW, are compatible with spark ignition engines up to 3 liters and compression ignition engines up to 1.6 liters, resulting in potential weight savings of up to 40% Operating similarly to conventional pre-engaged starters, the epicyclic intermediate transmission features a sun gear on the armature shaft, with the planet carrier driving the pinion, while the stationary ring gear functions as both an intermediate bearing and contributes to a reduction ratio of approximately 5:1.
Ratio=AS/S where A=number of teeth on the annulus, and S=number of teeth on the sun gear.
Heavy-duty applications utilize a variety of starter types, accommodating diverse operational needs In specific situations, voltages can reach up to 110 V, and for exceptionally high power and torque requirements, it is possible to operate two starters in parallel.
Large road vehicles typically operate on a 24 V system and utilize various starter types, including heavy-duty versions of pre-engaged starter motors A prime example is the DelcoRemy 42-MT starter, which features a thermal cut-out to protect against overheating from excessive cranking With a power rating of 8.5 kW, this starter can generate over 80 Nm of torque at 1000 revolutions per minute.
Toyota Vios 2018 circuit diagram and basic operation
2.5.1: Component of the Toyota Vios 2018 starting system
Figure 2 14: Toyota Vios 2018 starting system
1: Battery; 2: Electrical switch; 3: Starting relay; 4: Starting motor
The magnetic switch, or starter solenoid, operates on the principle of magnetism, energizing a coil of wire to create a magnetic field when an electrical signal is sent This field attracts a plunger, completing the circuit between the battery and the starter motor, which cranks the engine to start the vehicle Once the engine is running, the switch disconnects the starter motor from the battery to prevent damage In the Toyota Vios 2018, this critical component engages the starter motor when the driver turns the key or presses the engine start button, ensuring safety by preventing engagement while the engine is already running.
2.5.1.2: Armature shaft and rear bushing
Figure 2 16: Armature shaft and rear bushing
Armature shaft and rear bushing generates motor rotation and ball bearings support the core (armature) to rotate at high speed.
The brush is pressed against the armature's commutator by springs, enabling current to flow in a specific direction while maintaining stability Coal brushes, made from copper and carbon alloys (60-70% copper), offer excellent thermal conductivity and wear resistance The compressed springs in the carbon brush help halt the armature immediately after the starter is disengaged However, if the brush spring weakens or the brushes wear down, it can lead to inadequate electrical contact with the commutator, increasing resistance and reducing the current supplied to the motor, ultimately resulting in decreased torque.
Figure 2 17: Brushes and brushes mount
Starter field coils are essential components of an automobile's starter motor, consisting of magnetic wire windings that encircle the armature These coils act as electromagnets, generating magnetic fields that facilitate the rotation of the armature The rotation is initiated when electric current flows through the coil windings of both assemblies.
Starting field coils generate an electric current that produces a magnetic flux around the starter armature This interaction between the electric current and the magnetic field causes the movable armature to rotate.
The fixed field coil assembly plays a crucial role in generating the magnetic field essential for the armature assembly and shaft's rotation Its primary function is to produce the magnetic force required to initiate the armature's movement by magnetizing the core and creating a magnetic flux around the wire loops.
2.5.1.5: Bendix drive and Bendix gear
The Bendix gear, also known as the starting gear, utilizes a helical driving mechanism to deliver starting torque from the motor This gear, designed with a bevel for easy engagement with the flywheel ring, facilitates the smooth insertion and removal of the Bendix gear from joints The helical shaft effectively converts the electric motor's rotational force into gear thrust, ensuring efficient operation.
Figure 2 19: Bendix drive and Bendix gear
The starter and flywheel gear rings in an automobile engine typically have a gear ratio ranging from 9 to 18 To manage the size of the flywheel gear ring, some electric motors with high starting power incorporate an intermediate gear transmission, which may utilize helical or spur gears The transmission coupling is essential for transferring torque from the starter motor to the flywheel gear rim Due to the gear ratio, the starter must complete 10 to 20 rotations to turn the flywheel gear ring once When the electric motor operates, its rotor speed reaches approximately 2000 rpm, enabling the car engine's crankshaft to rotate at around 200 rpm, sufficient for engine startup.
The Bendix play an important role:
- Transfer the torque from the starter motor to the flywheel.
- Protect the starter motor by separate the Bendix gear with the flywheel when the engine start
2.5.2: Toyota Vios 2018 starting system circuit and operation
The starting system converts electrical energy from the battery into mechanical energy, which is utilized by the starting motor This motor transfers mechanical energy through gears to the engine's flywheel on the crankshaft As the flywheel rotates during cranking, it draws in the air-fuel mixture, compresses it, and ignites it to initiate engine start-up Typically, most engines require a cranking speed of approximately 200 rpm.
There are 2 model of the starting circuit: Model with automatic transmission (Figure 2.20) and model with manual transmission (Figure 2.21)
Figure 2 20: starting circuit configuration for automatic transmission
Figure 2 21: starting circuit configuration for manual transmission
- When ignition switch in “ST” Current flow from the battery through terminal
The current flows from the pull-in coil through terminal C to the field and armature coils, which limits the motor's speed due to the voltage drop across the pull-in coil This mechanism allows the solenoid plunger to pull the lever, engaging the pinion gear with the ring gear Additionally, the combination of the screw spline and low motor speed ensures a smooth meshing of the gears.
Figure 2 22: Current flow of the starter motor when ignition switch in ST
When the ignition switch is in the "ON" position, current flows to terminal 50 while the main switch stays closed, enabling current to pass from terminal C through both the pull-in coil and the hold-in coil This results in the cancellation of magnetic fields in the two coils, causing the plunger to retract due to the return spring Consequently, the high current supply to the motor is interrupted, leading to the disengagement of the pinion gear from the ring gear, and a spring-loaded brake effectively halts the armature.
Figure 2 23 : Current flow of the starter motor when ignition switch in ON
Most Toyota starting systems feature a one-way or over-running clutch designed to protect the starter motor after the engine starts This mechanism disengages the starter motor's housing from the inner race attached to the pinion gear, utilizing spring-loaded wedged rollers Without this over-running clutch, the starter motor could be severely damaged due to the engine's rotation being transmitted back through the pinion gear to the armature.
Figure 2 24: over-running clutch during engine starting and after engine started
2.5.2.2: Toyota Vios 2018 starting circuit analyze
When the ignition switch D8 is turned to the IG2 position, current flows from the battery to the D8 section, illuminating every light on the dashboard while the starter motor remains off.
Figure 2 25: Ignition switch at IG2 position
When the ignition switch is in the ST2 position, a positive current flows from the '30A ST' fuse to the ST relay, which then connects to the 50 terminals of the starter motor The C terminals of the motor are linked to the battery, allowing the starter motor to initiate operation.
Figure 2 26: Ignition switch at ST2 position
For manual transmission car, there a safety switch when the drive presses the clutch all the way in If not doing that the starting motor will not operate (Figure 2.27).
Automatic cars feature a Park and Neutral switch that functions similarly to a clutch start switch To start the vehicle, the driver must ensure the gear shift lever is positioned in either the Park (P) or Neutral (N) setting.
Figure 2 28: Park/Neutral position switch
Diagnostic, services of the Toyota Vios 2018 starting system
2.6.1: Diagnostic the Toyota Vios 2018 Starting system
The starting system requires minimal maintenance, as it only needs a fully charged battery and features hygienic, sealed, stainless steel electrical connections Diagnosing the booting system is straightforward due to its integrated mechanical and electrical components Common causes of starting issues typically stem from mechanical failures, like a broken flywheel tooth, or electrical problems, such as a damaged switch.
Common Failure symptom Possible caused
Starter noisy ● Starter pinion or flywheel ring gear loose.
● Discharged battery (starter may jump in and out).
● Battery terminals loose or corroded.
● Earth strap or starter supply loose or disconnected.
● High resistance in supply or earth circuit.
Engine does not rotate when trying to start
● Battery connection loose or corroded.
● Broken, lose or disconnected wiring in the starter or circuit.
● Defective starter switch or automatic gearbox inhibitor switch.
● Starter pinion or flywheel ring gear loose.
● Earth strap broken, lose or corroded.
Step 1: Check the starter before removing it from the car to see how the condition of the engine starts.
1 Ask the customer if there is anything unusual about starting the engine, such as a lengthy thread, difficulty starting the engine when it is cold or difficulty starting the engine when it is already warm, or any odd noises only routine maintenance, or neither).
2 Check the starter's operational status before starting the engine directly.
Step 2: Remove the starter from the engine.
1 Remove the battery's cool pole to ensure safety (avoid touching the positive pole to cause a fire or explosion).
2 Remove the starter anode protective pole cap, remove the nut and disconnect the anode (pole 30).
4 Remove the bolt and starter from the vehicle.
A Remove the nut and disconnect the lead from the magnetic switch terminal.
B Loosen the 2 nuts holding the switch assembly from the starter to the starter housing
C While pulling the magnetic switch assembly and lifting the front part of the switch, release the piston hook from the drive lever then remove the magnetic switch assembly.
D Remove the two through bolts and pull out the rotor and stator together
E Remove the 2 screws and the commutator head bracket and hold the wire while releasing the commutator head bracket.
F Use a screwdriver to secure the brush spring and remove the brush holder.
G Remove the drive lever and starter clutch with the damper from the starter housing.
H Using a screwdriver (or spanner 14), close the stopper towards the starter clutch.
Step 3: Things to do when maintaining the machine starts after removing the parts.
1 Clean the soot and dirt sold on the starter (Using gasoline and steam hose)
2 Check the length of the starter body brush to see if it is within the allowable standard (the spare part of coal to contact the commutator is at least 4mm).
3 Check the commutator for burns or wear beyond the allowable limit (if burned or dirty,clean it with P 400 sandpaper).
4 Check the rotor to see if there is a phenomenon of friction (remove it closely on the rotor body see if there is direct contact between the rotor and stator part).
5 Check the engagement gear for tooth wear.
6 Check the switch from the starter machine (elasticity of the spring, the poles are wobbly or loose, check the resistance between the terminals).
Figure 2 30: Starter motor inspection procedure
Step 4: Re-install and check the starter motor
Manufacture the starter system based on Toyota Vios 2018
Design a circuit diagram on “Circuit diagram web editor”
Figure 3 1: circuit model of the starting system
When the ignition switch is in the "IG" position, electrical current flows from the battery to the fuse and then to the ignition switch In this state, the starter motor remains inactive, and the dashboard lights illuminate.
When the driver turns the key switch to the ST position, current flows to the clutch switch or the Park and Neutral switch, activating the ST relay and energizing the pull-in winding relay, resulting in the vehicle's starting motor running.
- Using a DC voltage input so it easier to operate than AC input
- Hard to transport due to large compartment
- Easy to break when not careful
- Could be failure if not doing proper maintenances.
The Parameters of components of the model
The starting system consists of six essential components: the battery, ignition switch, starter relays, filament bulb, starter motor, and fuse These elements work together to initiate the engine's operation.
Key switch: provides a way of distributing the battery's current to the essential components of the beginning mechanism (figure 3.2) The key switch typically has the following 3 positions: OFF, IG, ST
Battery: this 12V battery supplies a current up to more than 250A to the starter system (figure 3.3)
A fuse is a safety device made of metal wire that melts when exposed to excessive current, effectively breaking the circuit and preventing energy flow to connected devices Commonly utilized in automobiles, fuses protect electrical systems from high voltage surges In this model, we will be using a 10A fuse.
In this system, we utilize two 4-pin relays, which are crucial for the car starting mechanism These relays effectively manage and control substantial currents exceeding 250A The operational principle of a relay involves using a small electrical input to regulate and control a much larger current.
Filament bulb (figure 3.6): We used 12V filament bulb as an indicator whether the model is on or off.
Starter motor: It is a four-pole, four-brush equipment that was used on small to medium-sized gasoline-powered automobiles (figure 3.7) It has a current draw of
Figure 3 7: Toyota Vios starter motor
Summary
The concept of using an electric motor to start car engines has remained largely unchanged over the past 80 years, although modern starters are now significantly more reliable and durable Remarkably, a contemporary starter is engaged approximately 2,000 times a year in typical city driving conditions, reflecting the extensive research and development that has gone into enhancing its dependability.
After acquiring specialized knowledge, our team successfully completed a project focused on the automotive electrical and electronic systems, specifically researching the starting system of the 2018 Toyota Vios.
- Design a basic circuit diagram of a starting system
- Analyze the Toyota Vios 2018 starting system circuit diagram
- Building a model of the starting system
- Analyze some common failure on the starting system
The graduation project successfully met its objectives, thanks to my determination and consistent efforts, along with the patient guidance and enthusiastic support from my instructor, Dr Pham Van Kien, and the valuable recommendations from faculty members.