豐田威馳汽車電器實(shí)驗(yàn)臺的設(shè)計(jì)【含CAD圖紙+文檔資料】,含CAD圖紙+文檔資料,豐田,汽車電器,實(shí)驗(yàn),試驗(yàn),設(shè)計(jì),cad,圖紙,文檔,資料 附 錄1:英文文獻(xiàn) AUTO ELECTRIC APPLIANCES 1、Starting System Automobile engines are not self-starts. In order to start them, the engine crankshaft must be turned over. To do this, the starter motor receives electrical power form the storage battery. The starter motor then converts this energy into mechanical energy, which it transmits through the drive mechanism to the engine’s fly wheel. The starter motor draws a great deal of electrical current from the battery. A large starter motor might require 300 to 400 amperes of current. This current flows through the heavy gauge cables that connect the battery to the starter. The drive controls the flow of this current using the starting switch. However, if the cables were routed from the battery to the starting switch and then on to the starter motor, the voltage drop caused b resistance in the cables would be too great. To avoid this problem, the system is designed with two connected circuits: the starter circuit and the control circuit. 1.1 The starting safety switch The starting safety switch is also called a neutral start switch. It is a normally open switch that prevents the starting system from opening when the automobile’s transmission is in gear. If the car has no starting safety switch, it is possible to spin the engine with the transmission in gear. This will make the car lurch forward or backward which could be dangerous. Safety switches or interlock devices are used with all automatic transmissions and on many late-model cars with manual transmissions. The safety switch can be an electrical switch that opens the control circuit if the car is in gear. It can also be a mechanical interlock device that will not let the ignition switch turn to start if the car is in the gear. 1.2 Magnetic Switch (Relays and Solenoids) A magnetic switch in the starting system allows the control circuit to open and close the starter circuit. The switch can be a: (1)Relay which uses the electromagnetic field of a coil to attract an armature and close the contact points. (2)Solenoid which uses the electromagnetic field of a coil to pull a plunger into the coil and close the contact points. The plunger’s movement can also be used to do a mechanical job, such as shifting the starter motor gear in a solenoid-actuated drive. 1.3 Starter Motor The starter motor converts electrical energy from the battery into mechanical energy to turn the engine. It does this through the interaction of magnetic fields. When current flows through a conductor, a magnetic field is formed around the conductor. If the conductor is placed in another magnetic field, the two fields will be weakened at one side and strengthened at the other side. An automotive starter motor has many conductors and uses a lot of current to create enough rotational force to crank the engine. The armature is the collection of conductors that will spin to crank the engine. The starter drive gear is mounted on the armature shaft. The pole pieces are the stationary magnetic fields. The motor housing encloses the armature and pole pieces, holds the bearings that support the armature shaft, and provides the terminals for connecting the motor to the rest of the staring system. 2.I gniting System The ignition system on an internal combustion engine provides the spark that ignites the combustible air/fuel mixture in the combustion chamber. The spark consists of an electric are produced by applying a high voltage across the electrodes of a spark plug. This spark must occur near the end of the compression stroke, as the position approaches top dead center (TDC). The cylinders must fire in the proper order and at a precise instant, depending on engine speed, load and temperature conditions. A spark plug consists of a pair of electrodes called the center and ground electrodes, separated by a gap. A spark is produced by applying a high voltage (from approximately 6 KV to 40 KV) between the center electrode and ground. Once the arc is started, a much lower voltage is required to sustain the arc to ignite the air/fuel mixture. The ignition system is divided into two circuits: the primary and the secondary. The primary circuit is the low-voltage side of the system and controls the secondary circuit, which is the high-voltage side of the system. The following are the basic parts of the primary ignition circuit: (1)Battery and/or alternator. Supplies the low voltage (12V) used to operate the primary circuit. (2)Ignition switch. Key-operated switch used to feed battery voltage to the primary circuit. (3)Primary wires. Low voltage wires used to connect the electrical components of the primary circuit. (4)Ignition coil primary winding. Current flow through the coil produces an electromagnetic field, which is used to induce a high voltage in the secondary coil. (5)Electronic control unit. Contains a switching transistor controlled by a speed sensor and is used to open and close the primary circuit. (6)Speed sensor, or pickup. Produces a pulsating voltage that signals the generation of an ignition spark. The following are the basic parts of a secondary ignition circuit: (1)Ignition coil secondary winding. Has a high voltage (40,000 V or more) induced in it each time the primary magnetic field collapses. (2)Coil wire. Heavily insulated wire that feeds high voltage from the ignition coil to distributor cap. (3)Distributor rotor. Operates in conjunction with the distributor cap to distribute the high voltage from the ignition coil to the individual spark plug wires in the firing order. (4)Distributor cap. Insulated cap that transfers high voltage from the distributor rotor to spark plug wires. (5)Spark plug wire. Heavily insulated wire that carries high voltage from the distributor to the spark plugs. (6)Spark plug. Provides the air gap within the combustion chamber for the high voltage to arc across, thus igniting the air/fuel mixture. ３.Lighting Circuit The lighting system in a typical automobile includes the headlight, parking lights, direction-signal lights, side marker, stoplights, tail lights, and interior lights. 3.1 Main Lighting Switch The main lighting switch (sometimes called the headlight switch) is the heart of the lighting systems. It controls the headlights, parking lights, side marker lights, taillights, license plate light, instrument panel lights, and interior lights. Individual switches are provided for special purpose lights such as directional signals, hazard warning flashers, back up lights, and courtesy lights. The main lighting switch may be of either the “push-pull” or “push-pull with rotary contact” types. A typical switch will have three positions: off, parking, and headlamps. Some switches also contain a rheostat to control the brightness of the instrument panel lights. The rheostat is operated by rotating the control knob, separating it from the push-pull action of the main lighting switch. When the main lighting switch completes the circuit to the headlamps, the low beam lights the way for city driving and for use when meeting oncoming traffic on the highway. When the dimmer switch is actuated, the single filament headlamps go “on”, along with the high beam of the two filament headlamps. The next actuation of the dimmer switch returns the headlight system to low beams only on the two filament lamps. Some cars are equipped with and electronic headlight dimming device, which automatically switches the headlights from high beam to low in response to light from an approaching vehicle or light from the taillight of a vehicle being overtaken. The dimmer switch in the automatic headlamp dimming system is a special override type. It is located in the steering column as part of a combination dimmer, horn, and turn signal switch. The override action occurs when a slight pull toward the driver on the switch lever providers high beam headlights regardless of the amount of light on the sensor-amplifier. For some years there has been discussion about the advantages of a polarized headlight system. Such a system comprises headlights which produce polarized light in a particular plane. The windscreens of all cars would be fitted with polarizing glass, which would be oriented so that glare from an approaching vehicle would be essentially eliminated, while the forward vision would still be kept at the present levels. The advantages the system appear attractive, but the practical problems of making the transition are very great, since it would not be practical to convert all existing vehicles to this type of lighting. Also, any benefits would only be marginal because glare itself is not a frequent cause of accidents. However, many cars now have refracting or colored glass to cut down on glare. 3.2 Directional Signal Switch The directional signal switch is installed just below the hub of the steering wheel. A manually controlled lever projecting from the switch permits the driver to signal the direction in which he wants to turn. Moving the switch handle down will light the “turn signal” lamps on the left front and left rear of the car, signaling a left turn. Moving the switch upward will light the turn signal lamps on the right (front and rear), signaling a right turn. With the switch in a position to signal a turn, lights are alternately turned “on” and “off” by a turn signal flasher. Incorporated in the directional signal switch is a “l(fā)ane change switch mechanism”. This feature provides the driver the opportunity to signal a lane change by holding the turn lever against a dent, then releasing it so cancel the signal immediately after the maneuver is completed. 3.3 Stoplight Switch In order to signal a stop, a brake pedal operated “stoplight switch” is provided to operate the vehicle’s stop lamps. In addition to lighting the conventional rear lights, the switch also operates the center high-mounted stop lamp, which became mandatory on later models. Cruise control equipped vehicles may also utilize a vacuum release valve. In this case, both the vacuum release valve and the stoplight switch are actuated by movement of the brake pedal. 5