LV19 electronic and electrical systems issue 1

Hệ thống điện và điện tử ô tô LV19 electronic and electrical systems issue 1 LV19 electronic and electrical systems issue 1 LV19 electronic and electrical systems issue 1 LV19 electronic and electrical systems issue 1 LV19 electronic and electrical systems issue 1 Hệ thống điện và điện tử ô tô LV19 electronic and electrical systems issue 1 LV19 electronic and electrical systems issue 1 LV19 electronic and electrical systems issue 1 LV19 electronic and electrical systems issue 1 LV19 electronic and electrical systems issue 1 Hệ thống điện và điện tử ô tô LV19 electronic and electrical systems issue 1 LV19 electronic and electrical systems issue 1 LV19 electronic and electrical systems issue 1 LV19 electronic and electrical systems issue 1 LV19 electronic and electrical systems issue 1 Hệ thống điện và điện tử ô tô LV19 electronic and electrical systems issue 1 LV19 electronic and electrical systems issue 1 LV19 electronic and electrical systems issue 1 LV19 electronic and electrical systems issue 1 LV19 electronic and electrical systems issue 1

kap all covers 6/9/03 9:50 am Page 37 Student Workbook LV19 Electrical and Electronic Systems (1) LV19/SWB Student Workbook for Technical Certificates in Light Vehicle Maintenance and Repair MODULE LV19 ELECTRICAL AND ELECTRONIC SYSTEMS (1) Contents … Page Page …… Introduction Battery: Cells Reaction Reaction process Battery capacity Vehicle charging systems 4 6 Principle of Electrical Generation: Fleming’s right hand rule Alternator Phase Electricity: Rectification to D.C Current flow 12 12 13 Alternator – The Real Thing: Voltage regulation 14 15 Principle of Integrated Circuit Regulator 16 Monolithic Integrated Circuit Regulator: Ignition on - engine not running Engine running - charge voltage less than target Target voltage reached Progress check 19 19 20 Starting Systems: Principle of the motor Flemings’ left hand rule Need for a commutator 21 21 22 23 A Series Wound D C Motor 24 Starter Circuit: Starter motor Basic outline Ignition/starter switch in the crank position Pinion and ring gears engaged Starter switch released Starter clutch Progress check 25 26 27 17 18 27 28 29 30 31 (Contd.) -1Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue P Page Page Electrical Wiring Diagrams: Japanese manufacturers Exercise European manufacturers Progress check 32 32 34 35 36 Auxiliary Systems: Interior light circuit Rear window demister Door locking Door mirrors Exercise Headlights and tail lights Direction indicators Power windows Exercise Sunroof Progress check 37 37 40 43 46 47 48 51 53 55 56 59 Bulbs 60 Maintenance: Hydrometer Specific gravity Alternator drive belts Progress check 62 63 63 64 65 -2Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue Introduction Vehicle electrical systems are becoming increasingly complex with the continued development of the motor vehicle This said, the same basic principles apply During this course of study we will be looking at a typical vehicle charging system, starting system and general auxiliary systems such as power windows Battery The battery is the heart of any vehicle electrical system It produces electrical energy through means of a chemical reaction (it converts chemical energy into electrical energy) The battery consists of a number of electrical cells – the term battery is actually a collective noun for cells, in much the same way that battery is a collective noun for chickens! It should be noted therefore that referring to a single cell as a battery is technically incorrect Each cell can produce a maximum of 2.2 volts and a typical vehicle battery consists of six cells (13.2 volts maximum) -3Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue Cells Each cell consists of negative plates - made from spongy lead – and positive plates – made from lead peroxide These dissimilar plates are suspended in an electrolyte (a solution that allows electrical current to flow within it) This electrolyte is diluted sulphuric acid Due to the use of these materials, a vehicle battery is often referred to as a ‘lead-acid battery’ The materials from which the plates are made and the electrolyte solution in which they are suspended react in such a way that a relatively large amount of electrical current is produced Reaction When a lead plate and a lead peroxide plate are suspended in dilute sulphuric acid, an electromotive force is generated between the two plates The lead plate becomes the negative plate and the lead peroxide plate becomes the positive Once an external circuit is connected to these plates, electrical current starts to flow from the plates within the battery The generation of electrical energy is through the chemical reaction that occurs in the battery and this reaction brings about a change in the state of the materials in each cell The following formulae represent the reaction: Charging: PbO2 (lead peroxide) + 2H2SO4 (Sulphuric acid) = Discharging: PbSO4 (lead sulphate)+ 2H2O (water) + PbSO4 -4Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue From the equation on the previous page, it can be seen that the discharging of the battery creates lead sulphate and water Consequently, the more discharged the battery becomes the more lead sulphate is formed on the plates and the more similar they become If the plates reach a point where they are virtually identical in their chemical make up, no electromotive force will be generated between the two (the battery is discharged, or flat) This is often described as a ‘sulphated’ battery However, it can also be seen from the equation that the act of charging a battery can indeed reverse this process This is what actually happens on a vehicle; the alternator charges the battery by supplying electrical current to it, and this has the reverse effect chemically This happens on a continual basis ensuring that the battery remains in a fully charged state normally (see figures A, B and C) Reaction process B A C -5Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue Battery capacity Battery capacity is a figure that reflects the battery’s ability to discharge a given amount of current for a given amount of time The unit that is used is ‘amperehours ‘ or amp-hours The system works as follows: If a battery is capable of producing amp continuously for hour, then it is a amp-hour battery If that battery is capable of producing 60 amps continuously for a period of hour, then it is a 60 amp-hour battery The same battery would by definition be able to produce 120 amps continuously for a period of 30 minutes The point at which the battery is deemed to be fully discharged is when its voltage drops to 10.5 v (1.75 v per cell) Vehicle charging systems We have seen that in order for a vehicle’s battery to maintain a good state of charge, electrical current has to flow to it so that the chemical changes undergone during discharging can be reversed A vehicle’s charging system does this and must have a sufficient capacity to ensure that current, in excess of that demanded from the battery, is supplied In this way, a high state of battery charge is maintained -6Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue Principle of Electrical Generation Electricity is generated when a magnetic field experiences a change in strength in the presence of a conductor – electricity will flow in that conductor (so long as that electrical current has a route to follow i.e a circuit) It can be seen that the magnetic lines of force that are being produced by the magnet are moving from the magnet’s north pole to the south As the conducting bar is moved through these magnetic lines of force (or flux) their strength is altered This generates electrical current flow in the conductor The circuit that is necessary in order for current to flow has been wired through an ammeter in order for the presence of current to be registered The greater the number of magnetic lines of flux that are ‘cut’ per unit time, the greater the amount of current that is produced The generator pictured would therefore produce very little current and it would probably take a galvanometer to register it (a very sensitive ammeter) So how can we increase the number of lines of magnetic force that are cut per unit time in order to generate more current? • move the conductor faster • use a more powerful magnet • use multiple magnets • use multiple conductors An alternator generates the current required to charge a vehicle’s battery and it uses all of the above methods in order to increase the current generated -7Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue Fleming’s right-hand rule Alexander Fleming was something of a pioneer in the area of electrical discovery He devised a rule that enables us to readily ascertain in which direction the current will flow in a conductor Using your right hand, point your index finger in the direction of the magnetic flux (north to south on the magnet) Point your thumb in the direction that you intend to move the conductor, and your third finger will now point in the direction of current flow -8Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue The alternator One of the easiest ways to increase the number of conductors moving in the magnetic flux; and also to enable a continuous movement to be easily achieved, is to rotate a looped conductor within the flux Apply Fleming’s right hand rule to the arrangement shown above You will see that as the loop passes through the 12 / o’clock position, the direction of current flow in the loop will effectively reverse and the direction of current flow alternates Alternating current has been generated The loop has to continually rotate but the circuits on the vehicle to which the current is required to flow are static, a rotary contact is required These are called slip rings and can be seen in the diagram above The slip rings rotate with the conducting loop and are in constant rubbing contact with the brushes These brushes eventually wear beyond repair, and the alternator will stop charging Most alternators have brush packs that are easily replaced -9Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue Direction indicators This circuit enables the driver to operate the directional indicators on the vehicle It also enables the driver to operate the hazard warning lights - 51 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue Circuit operation With the hazard switch in the ‘off’ position, battery voltage is applied from the ignition switch to the turn signal flasher at terminal via terminals 10 and of the hazard warning switch When the driver moves the turn signal switch to the ‘left’ position, the turn signal flasher alternates the supply of current to the left indicator lamps acting on an internal timer circuit The turn signal switch directs this control to the right indicator lamps if the driver moves the switch to this position If the driver turns on the hazard switch, battery voltage (not ignition controlled) is applied to terminal of the turn signal flasher via terminals and of the hazardwarning switch The turn signal flasher then sends its signal to terminal of the hazard warning switch From here, the signal is sent via terminals and of the hazard warning switch to all four indicator lamps - 52 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue Power windows This circuit enables the driver to operate the windows (all four) from the driver’s master switch and the passengers to operate their personal window from their own door-mounted switch - 53 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue Power windows – circuit diagram Circuit operation To understand this circuit, we will study the operation of the front passenger window from the front passenger window switch When the driver turns on the ignition, the power main relay is energised This then applies battery voltage to terminals and of the power window master switch (driver’s door) and terminals of the other window switches If the passenger now puts their switch in the down position, the position of the switch will enable current to flow from terminal to terminal of the passenger’s switch and via the loom to terminal of the power window motor through the circuit breaker and motor, back out of the assembly at terminal and back into the passenger’s switch at terminal - 54 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue The current now flows across the contact of the switch and out from the switch assembly via terminal 2, into the power window master switch at terminal 12 across the ‘Up’ contact, down through the window lock switch (which will be closed unless the driver has chosen to isolate the windows) and down to ground via terminals and of the master switch Exercise Map out current flow for the following operation: Driver moving the rear right passenger window to the up position - 55 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue Sunroof This circuit facilitates control of the sunroof This assembly is able to tilt up (and back down) and can also open fully (and close fully) This type of sunroof is often referred to as a ‘slide and tilt’ sunroof - 56 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue Circuit operation When the driver turns the ignition switch on, the power relay energises and applies battery voltage to terminal of the sunroof control relay (again, a simple ECM) When the sunroof switch is moved to the open position a ground is provided to terminal of the sunroof control relay via terminals and of the sunroof switch Upon receipt of this ground signal, the sunroof control relay connects terminal (relay supply) to terminal 4, which allows current to flow through the sunroof motor in a direction that opens the sunroof The ground route for this current is via terminal of the motor and terminals and 11 of the sunroof control relay - 57 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue The sunroof limit switch assembly breaks contact relative to sunroof position i.e fully open / fully closed and upon receipt of this signal, the motor will cut out regardless of continued operation of the sunroof switch The ‘Up’ and ‘Down’ contacts of the switch indicate to the sun roof control relay that the operation required is limited to tilt up and tilt down The motor is operated accordingly - 58 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue Progress check Answer the following questions: On page 38 of your work book you have the interior light circuit What will the voltage be at terminal of the room light assembly with the driver’s door open (serviceable circuit)? On page 46 of your handbook you have the remote control mirror circuit What will the voltage be at terminal of the left hand mirror with the driver selecting ‘Up’ on this mirror (serviceable circuit)? What is a grounded circuit? What is the function of a relay within an electrical circuit? - 59 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue Bulbs Semi-sealed type Handling There are many different types of bulb in use on a modern motor vehicle Generally, bulbs can be classified by their rating (wattage and voltage) and their fixing method i.e how the bulb is securely mounted to the lamp assembly There are exceptions to this rule, certain bulbs have specialist applications such as halogen bulbs which are used exclusively for headlights It is most important that the glass portion of halogen bulbs is not touched, as moisture from the surface of the skin can cause localised cool areas on the glass when the bulb is operating and this can cause the bulb to break - 60 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue A bayonet cap type design - it can be seen that the single filament bulb has bayonet pins that are on the same plane but the double filament bulb has offset pins Offsetting the pins ensures that the internal circuitry of the bulb connects to the correct terminals of the wiring loom Variations in bulb design - 61 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue Maintenance A typical vehicle battery Most batteries now are low maintenance or maintenance free A low maintenance battery has cell caps that can be removed to facilitate the topping up of the electrolyte with distilled water It is very important that only distilled water is used, as the impurities in tap water inhibit the ability of the electrolyte to conduct electricity and can form layers of impurity on the surface of the plates The electrolyte should be maintained at a level that ensures the plates are covered Most batteries have level marks on the casing Most maintenance free batteries have only breather holes in the cells (no removable caps), but this is not always the case Some manufacturers claim their product to be maintenance free, but still provide caps This is more to aid the diagnosis of the battery condition than to provide a means for maintenance to be carried out - 62 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue Hydrometer One of the most effective ways of checking the serviceability of a vehicle battery is through the use of a hydrometer (Specific Gravity) A hydrometer is a device that is able to measure the specific gravity of a fluid Specific gravity Specific gravity is a comparative unit that enables us to gauge the density of a fluid when compared to that of pure water - 63 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue 1 litre of pure water weights kg Therefore, if litre of a given fluid weighs kg then it is twice as dense and therefore has a specific gravity of (no units) Battery electrolyte is dilute sulphuric acid It is therefore a mix of sulphuric acid and distilled water Concentrated sulphuric acid is considerably more dense than water and therefore its presence increases the density (and specific gravity) of the electrolyte A fully charged battery in good order will have a specific.gravity of 1.27 to 1.28 We have seen that as a battery discharges more water is produced Therefore, the specific gravity will reduce as the batteries charge state reduces As the hydrometer is capable of drawing electrolyte up from each individual cell and allowing us to read the specific.gravity, it is most suited to the inspection of a battery It also enables us to view the electrolyte If it appears brown (muddy) then the plates are sulphated and the battery should be replaced Alternator drive belts Alternators are nearly always driven by belts from the crankshaft Magnetic fields of considerable strength are present when the alternator is under a heavy load and this will result in belt slippage if the belts are allowed to become excessively loose This is normally accompanied by a loud squealing sound when extra load is placed on the electrical system such as turning on the lights Belt tension should be measured using a suitable belt tension gauge but this is not always possible due to poor access If this is the case, a general rule of thumb is that you should be able to twist the belt approximately 90 degrees on its longest length It should be remembered that this is a very approximate method and should not be used if a manufacturer recommends a different technique - 64 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue Progress check Answer the following questions: In which part of an alternator is the battery charging current generated? Why are two coils required (pull-in and hold-in) during engagement of the starter pinion? What should the specific gravity of a fully charged battery be? In a maintenance free battery how are the gases vented? What does the term specific gravity refer to? Which part of a quartz halogen should you not touch? - 65 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue ... LV19: Electrical and Electronic Systems (1) Issue Door locking - circuit diagram - 44 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) ... Progress check 25 26 27 17 18 27 28 29 30 31 (Contd.) -1Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue P Page Page Electrical Wiring... slip rings and brushes can run in to hundreds of thousands of miles - 11 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV19: Electrical and Electronic Systems (1) Issue 3-Phase