Manual Drivetrains and Axles Fourth Edition

Manual Drivetrains and Axles Fourth Edition

Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 OBJECTIVES After studying Chapter 6, the reader should be able to: 1. Describe the operation of DC and AC electric motors. 2. Explain how a brushless DC motor works. 3. Discuss the advantages and disadvantages of using electric motors in hybrid electric vehicles.

4. Explain how electric power steering works. 5. Describe how a DC-to-DC converter works. 6. Discuss how a DC-to-AC inverter works. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 FUNDAMENTALS OF MAGNETISM Magnetism is a form of energy that is generated by the

motion of electrons and alignment of atoms in some materials. A type of iron ore, called lodestone, exists as a magnet in nature. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 A Cracked Magnet Becomes Two Magnets

Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 Lines of Force In a bar magnet, the lines are concentrated at both ends of the bar and form closed, parallel loops in three dimensions around the magnet. They come out of one end, or pole, of the magnet and enter at the other end; they NEVER intersect.

Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 The opposite ends of a magnet are called its north and south poles. In reality, they should be called the "north seeking" and "south seeking" poles, because they seek the earth's North Pole and South Pole, respectively. The stronger the magnet, the more magnetic lines that

are formed. The magnetic lines of force, also called magnetic flux or flux lines, form a magnetic field. The terms magnetic field, lines of force, flux, and flux lines are used interchangeably. Flux density refers to the number of flux lines per unit of area. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

A magnetic field can also be observed by using a compass. A compass is simply a thin magnet or magnetized iron needle balanced on a pivot. The needle will rotate to point toward the opposite pole of a magnet. It can be very sensitive to small magnetic fields. Since it is a small magnet, a compass usually has one end marked N and the other marked S. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc.

Pearson Prentice Hall Upper Saddle River, NJ 07458 If like poles are placed close together, the curving flux lines meet head-on, forcing the magnets apart. Therefore, like poles of a magnet repel and the unlike poles attract. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall

Upper Saddle River, NJ 07458 Permeability Magnetic flux lines cannot be insulated. There is no known material through which magnetic force does not pass, if the force is strong enough. However, some materials allow the force to pass though more easily than others. This degree of passage is called permeability. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc.

Pearson Prentice Hall Upper Saddle River, NJ 07458 Reluctance While there is no absolute insulation for magnetism, certain materials resist the passage of magnetic force. Air does not allow easy passage, so air has a high reluctance. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall

Upper Saddle River, NJ 07458 ELECTROMAGNETISM Scientists discovered that current-carrying conductors are also surrounded by a magnetic field about 1820. The creation of a magnetic field by the use of an electrical current is called electromagnetism. As current increases, more flux lines are created and the magnetic field expands. As current decreases, the magnetic field contracts, or collapses. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin

2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 The magnetic field surrounding a straight, currentcarrying conductor exists along the entire length of the wire. The strength of the current determines how many flux lines there will be and how far out they extend from the surface of the wire. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc.

Pearson Prentice Hall Upper Saddle River, NJ 07458 Right-Hand Rule Magnetic flux cylinders have direction, just as the flux lines surrounding a bar magnet have direction. Most automotive circuits use the conventional theory of current flow (+ to -), and therefore the right-hand rule is used to determine the direction of the magnetic flux lines. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin

2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 Current-carrying conductors tend to move out of a strong field into a weak field, so the conductors move away from each other. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc.

Pearson Prentice Hall Upper Saddle River, NJ 07458 Electric motors, such as automobile starter motors, use this field interaction to change electrical energy into mechanical energy. These forces cause the center of the motor, where the conductors are mounted, to turn clockwise. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc.

Pearson Prentice Hall Upper Saddle River, NJ 07458 Coil Conductor If several loops of wire are made into a coil, the magnetic flux density is strengthened. Flux lines around a coil are the same as the flux lines around a bar magnet. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc.

Pearson Prentice Hall Upper Saddle River, NJ 07458 Electromagnets The magnetic field surrounding a current-carrying conductor can be strengthened by using a soft iron core. The concentration of force greatly increases the strength of the magnetic field inside the coil. Coils with an iron core are called electromagnets. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin

2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 ELECTROMAGNETIC INDUCTION Magnetic flux lines can create an electromotive force, or voltage, in a conductor if either the flux lines or the conductor is moving. This creation of a voltage in a conductor by a moving magnetic field is called electromagnetic induction. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin

2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 The highest voltage is generated when the motion is at right angles. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall

Upper Saddle River, NJ 07458 Voltage Strength There are four ways to increase induced voltage: Increase the strength of the magnetic field, so there are more flux lines. Increase the number of conductors that are breaking the flux lines. Increase the speed of the relative motion. Increase the angle between the flux lines and the conductor to a maximum of 90 degrees. Hybrid and Alternative Fuel Vehicles

By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

Maximum voltage is induced if the conductors break flux lines at 90 degrees and the voltage decreases when the flux lines are cut at angles between 0 and 90 degrees. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 An induced current moves so that its magnetic field opposes the motion that induced the current. This principle is called

Lenzs law. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 ELECTRIC MOTORS Electric motor power is expressed in kilowatts (kW). A kilowatt is equal to 1,000 watts. One hp is equal to 746 watts.

Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 Electric Motor Operation The torque of a starter is determined by the strength of the magnetic fields. Magnetic field strength is measured in ampere-turns. If the current or the number of turns of wire is increased, the magnetic field

strength is increased. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 A typical DC motor today uses four poles. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin

2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 The following are the basic principles of a typical DC motor: The speed of the motor is proportional to the applied voltage. The torque is proportional to the applied current. The speed is typically controlled by altering the voltage or current flow by using taps in the motor windings or by using a variable voltage supply. Hybrid and Alternative Fuel Vehicles

By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 The use of brushes in an electric motor has many disadvantges including: 1. Any arcing of the brushes also causes electrical noise. 2. The brushes eventually wear out and require replacement. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin

2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 What Is a Traction Motor and an Electric Machine? A traction motor is a motor used to propel a vehicle. The term traction comes from the engineering term that describes what must occur for a drive wheel to rotate and to transfer torque from the propulsion unit to the drive wheels. The term machine is commonly used to describe an electric motor because it is often more than a simple motor and requires controllers and other components to function.

Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 BRUSHLESS MOTORS There are two types of electric brushless motors: the AC induction motor and the AC synchronous motor. Hybrid and Alternative Fuel Vehicles

By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 AC Induction Motor An AC induction motor, as is used in the General Motors parallel hybrid truck (PHT). An AC induction motor is also known as an AC asynchronous motor, or AC induction motor (ACIM). The term asynchronous means that the speed of the motor is not necessarily related to the frequency of the current flowing

through the stator windings. ACIMs include squirrel-cage and wound-rotor induction designs. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 A squirrel-cage rotor. Hybrid and Alternative Fuel Vehicles

By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 An alternate design is called the wound rotor. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall

Upper Saddle River, NJ 07458 AC Synchronous Motor The AC synchronous motor rotates exactly at the supply frequency or a submultiple of the supply frequency. The speed is controlled by varying the frequency of the AC supply and the number of poles in the stator winding, according to the relation: RPM = 120F p where RPM = Synchronous speed F = AC power frequency p = Number of poles, usually an even number but always a

multiple of the number of phases Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 Permanent magnet rotors. Brushless permanent magnet motors use two designs of rotors:

The permanent magnets are part of the rotor in the core of the rotor. These are called a surface permanent magnets (SPMs). Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 In the other type, the permanent magnets are housed inside the outer shell of the rotor and are called interior permanent

magnets (IPMs). The Honda Accord, Ford hybrids, and Toyota hybrids use an IPM-type rotor assembly. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 In both types of motors, the stator coils are stationary and the permanent magnet assembly rotates. Alternating current (AC) is fed to the varous phases in

the stator in order to get the permanent magnets in the rotor to chase the changing magnetic field. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin

2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 There are ten electric motors, sometimes more, in most hybrid vehicles. These include: 1. One or two drive motor(s) 2. Motor to circulate the coolant during idle stop to keep the passengers warm (Toyotas/Honda Accord/Honda Civic) 3. Motor for electric power steering (EPS) (all) 4. Motor for A/C compressor (New Prius and Accord) 5. Motor for cooling CVT (Ford/Toyota/Lexus)

6. Motor for AT trans (hybrid Accord, GM PHT, and Saturn VUE) 7. Motor(s) for air cooling the HV batteries (all) 8. Motor for hydroelectric power steering (GM 42/36v) 9. Motor in CVT to engage park (2004+ Prius) 10. Rear differential (Lexus RX400h/Highlander 4WD) Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

Electric Motors Are Perfect for Vehicles An electric motor produces maximum torque at low speeds, making it the perfect power source to get a vehicle moving from a stop. Then, when the torque of an electric motor starts to drop off, the torque multiplied by the speed (RPM) results in power. Therefore, a typical electric motor used on a hybrid vehicle has the following characteristics: Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall

Upper Saddle River, NJ 07458 Delivers constant torque at low speed, typically from zero to 1,500 RPM Delivers constant power above 1,500 RPM Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

MOTOR CONTROL An example of traction motor control is the motor control module (MCM) used on Honda hybrid electric vehicles. The MCM has three inputs from three rotor position sensors, A, B, and C. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

The MCM has three outputs: U, V, and W. Each winding sends control information (digital high-low) to the power drive unit (PDU). Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 A typical Honda PDU schematic is shown.

Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 The current flow through the PDU is controlled by six insulated gate bipolar transistors (IGBTs). The IGBTs are current drivers that send current from the battery pack through the stator windings to energize the stator coils and move the rotor to power the drive wheels. Most motor controllers include Hall-effect current

sensors. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 The IGBTs process drive current to the electric drive motor. The diodes form a rectifier bridge to change the AC generated in the electric drive motor to pulsating DC to charge the battery pack.

Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 Toyota and Lexus use a speed sensor called a resolver to detect the rotor position. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin

2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 Cooling the Electronics

The current flow and the electronic devices in hybrid electric control units generate a lot of heat. Toyota, Ford, and GM hybrids use a liquid cooling method to control the temperature of the electronics. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 CAPACITORS IN HYBRID CONTROLLERS

A capacitor consists of two conductive plates with an insulating material between them. The insulating material is commonly called a dielectric. It may be air, mica, ceramic, glass, paper, plastic, or any similar nonconductive material. The higher the dielectric constant number of a material, the better it is as an insulator. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

When a capacitor is placed in a closed circuit, the voltage source, such as a battery, forces electrons around the circuit. Because electrons cannot flow through the dielectric of the capacitor, excess electrons collect on what becomes the negatively charged plate. At the same time the other plate loses electrons, and therefore becomes positively charged. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc.

Pearson Prentice Hall Upper Saddle River, NJ 07458 Current continues until the voltage charge across the capacitor plates becomes the same as the source voltage. At that time, the negative plate of the capacitor and the negative terminal of the battery are at the same negative potential. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc.

Pearson Prentice Hall Upper Saddle River, NJ 07458 An electrostatic field now exists between the capacitor plates because of their opposite charges. It is this field that stores energy. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

If the circuit is opened, the capacitor will hold its charge until it is connected into an external circuit through which it can discharge. When the charged capacitor is connected to an external circuit, it discharges. After discharging, both plates of the capacitor are neutral because all the energy from a circuit stored in a capacitor is returned when it is discharged. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin

2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 When the ignition of an HEV is turned off, vehicle manufacturers warn that you must wait 5 to 10 minutes

for the capacitors to discharge before servicing the high-voltage system. While these capacitors often discharge in less than five minutes, it is wise to wait the amount of time specified by the vehicle manufacturer. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

To avoid an electrical shock, any capacitor should be treated as if it were charged until it is proven to be discharged. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 Capacitors are also called condensers. This term developed because electric charges collect, or condense, on the plates of a capacitor much like water vapor collects and condenses on

a cold bottle or glass. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 Capacitance is measured in farads, which is named after Michael Faraday (1791-1867). The symbol for farads is F. If a charge of 1 coulomb is placed on the plates of a capacitor and the potential difference between them is 1 volt, the

capacitance is then defined to be 1 farad. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 Snubbers Snubbers are capacitors and resistors arranged in a circuit to control the high-voltages surges that can occur when circuits containing coils are switched on

and off. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc.

Pearson Prentice Hall Upper Saddle River, NJ 07458 CONVERTERS AND INVERTERS Converters DC-to-DC converters (usually written DC-DC converter) are electronic devices used to transform DC voltage from one level of DC voltage to another higher or lower level. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc.

Pearson Prentice Hall Upper Saddle River, NJ 07458 One example of a DC-DC converter circuit is the circuit the PCM uses to convert 14 V to 5 V. The 5 volts is called the reference voltage, abbreviated V-ref, and is used to power many sensors in a computer-controlled engine management system. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc.

Pearson Prentice Hall Upper Saddle River, NJ 07458 Hybrid electric vehicles use DC-DC converters to provide higher or lower DC voltage levels and current requirements. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

DC-DC Converter Circuit Testing 1. Always follow the manufacturers safety precautions when working with high-voltage circuits. These circuits are usually indicated by orange wiring. 2. Never tap into wires in a DC-DC converter circuit to access power for another circuit. 3. Never tap into wires in a DC-DC converter circuit to access a ground for another circuit. 4. Never block airflow to a DC-DC converter heat sink. 5. Never use a heat sink for a ground connection for a meter,

scope, or accessory connection. 6. Never connect or disconnect a DC-to-DC converter while the converter is powered up. 7. Never connect a DC-to-DC converter to a larger-voltage source than specified. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

Inverters An inverter is an electronic circuit that changes direct current (DC) into alternating current (AC). In most DC-AC inverters, the switching transistors usually metal oxide semiconductor field-effect transistors (MOSFETs) are turned on alternately for short pulses. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

The waveform produced by an inverter is not the perfect sine wave of household AC current, but is rather more like a pulsing DC current that reacts similar to sine wave AC in transformers and in induction motors. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

AC motors are powered by inverters. An inverter converts DC power to AC power at the required frequency and amplitude. The inverter consists of three half-bridge units and the output voltage is mostly created by a pulse width modulation (PWM) technique. The three-phase voltage waves are shifted 120 to each other to power each of the three phases. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

ELECTRIC POWER STEERING The electric power steering (EPS), also called electric power-assisted steering (EPAS), system includes the following components and inputs/outputs: A DC motor Reduction gear Torque sensor Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc.

Pearson Prentice Hall Upper Saddle River, NJ 07458 The electric power steering (EPS) is controlled by the EPS ECU, which calculates the amount of needed assist based on the input from the steering torque sensor. The steering torque sensor is a noncontact sensor that detects the movement and torque applied to the torsion bar. The torsion bar twists when the driver exerts torque to the steering wheel, and the more torque applied causes the bar to twist further. This generates a higher-voltage signal to the EPS ECU. Hybrid and Alternative Fuel Vehicles

By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

The Toyota Highlander and Lexus RX 400h use a different electric power steering unit due to the larger size of the vehicles. This unit uses a concentric brushless DC motor on the steering rack. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 Hybrid and Alternative Fuel Vehicles

By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 The Honda electric power steering uses an electric motor to provide steering assist and replaces the need for a hydraulic pump, hoses, and gear. A torque sensor is used to measure road resistance and the direction that the driver is turning the steering wheel. The torque sensor input and the vehicle speed is used by the EPS controller to supply the EPS motor with the specified current to help assist the steering effort.

Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall

Upper Saddle River, NJ 07458 Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 SUMMARY 1. Magnetic lines of force leave the north pole and enter the

south pole of a magnet. 2. Magnetic lines of force are called flux lines. 3. Any conductor carrying an electrical current generates a magnetic field around the conductor, and a moving magnetic field across a conductor creates electricity. 4. Like poles repel and unlike poles attract. 5. A brushless DC motor is also known as an AC synchronous motor. 6. Powerful permanent magnets are used in the rotors of both DC and AC brushless motors. 7. The operation of motors is performed by the controller, which is capable of switching the voltage and/or the frequency of the current flowing through the stationary windings of the

motor. 8. DC-DC converters are used in hybrid electric vehicles to convert the high-voltage battery current into a lower voltage used by the accessories and lighting systems. Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458 REVIEW QUESTIONS

1. How is an electrical current induced in a wire? 2. How does an AC synchronous motor work? 3. How does an AC induction motor work? 4. How is the operation of a brushless DC motor controlled? 5. What is a DC-DC converter, and why is it needed in a hybrid electric vehicle? Hybrid and Alternative Fuel Vehicles By James D Halderman and Tony Martin 2009 Pearson Education, Inc.

Pearson Prentice Hall Upper Saddle River, NJ 07458

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