by Steve Garrett for operating tools and appliances.

Transcription

1 The Shock of SPEAKER Your Life, PART 1 by Steve Garrett As we re all aware, changes in the automotive industry are occurring at an alarming rate. The pressure on OEMs to meet changes in the federal fuel economy and emissions standards and consumer demands for products with improved fuel economy, ride, and handling have led us into a decade of great change and advanced technology. One area that continues to raise a lot of questions is hybrid technology. During the 2004 ATRA seminars, we introduced the first GM hybrid to you: the PHT Parallel Hybrid Truck (RPO HP2). During the seminar we looked at the transmission changes, but we didn t have time to discuss the rest of the system. The PHTs are great sellers that offer improved fuel economy and added versatility. Hybrid systems vary greatly in operation and service procedures, so let s take an in-depth look at how the PHT works and how to service the system. The PHT was introduced in the 2004 model year in ½-ton 2WD and 4WD applications. Equipped with a 5.3L V-8 and a modified 4L60E transmission (RPO M33), the PHT improves fuel economy by as much as 10% overall. The major fuel economy increase is accomplished primarily by shutting off the engine during most idle conditions. To restart the engine the driver simply steps on the accelerator pedal; the auto start function allows the vehicle simply to drive away. In addition PHT equipped trucks offer the following changes: Elimination of the conventional starter. Elimination of the conventional alternator. Elimination of the engine-driven hydraulic power steering pump. Addition of four, 120-volt outlets for operating tools and appliances. The PHT system includes these components and systems (figure 1): Starter/Generator Assembly SGCM (Starter Generator Control HCM (Hybrid ESCM (Energy Storage Control ESB (Energy Storage Box) PCM (Powertrain ATCM (Active Transfer Case EBCM (Electronic Brake Control EHPS (Electro-Hydraulic Power Steering) BCO (Battery Cut-Off Switch) APO (Auxiliary Power Outlet) CSS (Crankshaft Sensor) IAT (Intake Air Temperature Sensor) TFP (Transmission Fluid Pressure ESCM (Energy Storage Figure 1A 36 GEARS October 2006

2 Regenerative Braking Function The starter/generator assembly also provides regenerative charging during closed throttle. The downshift assist feature downshifts the transmission while the engine remains in fuel cut-off or enleanment modes. This function improves fuel economy while maintaining about 950 RPM engine speed during the forced closed throttle 4-3 or 3-2 downshift. Downshifting the transmission increases the amount of electricity generated while reducing noise and vibrations. While in regenerative mode, the system stops capturing deceleration energy once a 4-3 or 3-2 downshift begins. The system maintains engine speed while the transmission clutches/ band complete the downshift process. The system then resumes generating electricity once the downshift is complete. [PSM]) EOP (Engine Oil Pressure Sensor) A/C Pressure Sensor ATS (Outside Air Temperature Sensor) Inside Air Temperature Sensor TRS (Transmission Range Sensor) VSS (Vehicle Speed Sensor) TFT (Transmission Fluid Temperature Sensor) Tow Haul Switch Brake Switch Hand (Steering) Wheel Sensor Cruise Control Switch TACM (Throttle Actuator Control APO (Auxiliary Power Output Switch) Transmission Secondary Fluid Pump Auxiliary Coolant Pump SGCM Coolant Pump Door Switches Hood Ajar Switch Fuel Level Sensor Three, 12-Volt Batteries; connected in series 125-Amp Fuse, 175-Amp Fuse, 400-Amp Fuse 42-Volt System Disconnect Switch Figure 1B: Inverter As you can see this system is going to be fairly complicated, so let s start with the main components first. Starter/Generator Assembly The starter/generator assembly sits in the transmission bellhousing; it consists of a stator and rotor (figure 2). The stator is mounted stationary and uses a wye wound design. Each leg of the stator is connected to the SGCM (Starter Generator. Treat the legs of the stator and its wiring carefully; damage or improper diagnostic procedures can cause system failure or personal injury. The rotor is attached to the engine crankshaft and rotates at crank speed. The starter generator assembly provides these functions: Alternator Function Creates 3- phase AC output. As the rotor turns, the windings cut through magnetic field created by the stator, inducing current. The output voltage and frequency depend on the speed of the crankshaft (maximum 50 volts AC, figure 3). Starter Function To act as a starter, the starter/generator assembly receives volts to energize the windings. The HCM (Hybrid Control commands the SGCM (Starter Generator to send voltage to each leg of the starter/generator stator during both key start and auto start operation. During key start, the ignition switch provides input to the PCM. It relays the ignition switch signal to the HCM (Hybrid, which operates the starter. For the auto start to function, the TACM (Throttle Actuator relays the commanded throttle position to the PCM, which it relays to the HCM (Hybrid Control through the data bus. As you step on the accelerator pedal, the engine starts, allowing the vehicle to drive away as if the engine had been running all along. SGCM (Starter Generator The SGCM (Starter Generator is mounted on the passenger side inner fender. The SGCM performs these functions: Receives raw 3-phase voltage from the starter/generator assembly. Converts (rectifies) the 3-phase AC to DC to charge the batteries in the GEARS October

3 The Shock of Your Life, Part and 12-volt systems. Uses energy from the 42-volt system to drive the starter/generator for engine starting. Activates, controls and monitors the 120-volt APO (Auxiliary Power Outlet) circuits. Controls the 42-volt system to operate the EHPS (Electro-Hydraulic Power Steering). If the vehicle requires a jump start, the SGCM (Starter Generator will convert the 12-volt jump start voltage to 42- volts to energize the starter/generator assembly. Controls the SGCM (Starter Generator coolant pump and cooling fan. HCM (Hybrid The HCM (Hybrid is mounted on the left side of the fan shroud (figure 4). Here are the functions the HCM provides: Monitors communications over the Class 2 and GM LAN data buses to control each module s function. Commands the SGCM (Starter Generator to activate/deactivate the 120-volt APO Ready to Shift to a Better Insurance Program? Get into Gear with Heffernan Insurance Brokers. Offering property, liability, workers comp and more for your transmission business. Contact us today Brant Watson BrantW@heffgroup.com License # ATRA program facilitated by Heffernan Insurance Brokers and Brant Watson. (Auxiliary Power Outlet) circuit or supply power to the 42-volt system. Controls electrical current flow/ direction and output voltage via a bidirectional inverter. Monitors several inputs to control system operation. When requested by the HVAC (Heating Ventilation Air Conditioning) controller, the HCM (Hybrid energizes the auxiliary coolant pump. Energizes the auxiliary transmission pump when the vehicle is stopped. Diagnoses faults in the APO (Auxiliary Power Outlet) circuits. Controls transmission downshift assist functions via the PCM and the starter/alternator assembly. Enables or disables the driveshaft vibration/surge program. Commands the ESCM (Energy Storage to disable the 42-volt system during airbag deployment. Targets the engine speed for the SGCM (Starter Generator Control. Specifies minimum and maximum starter/generator torque values to make sure starter/generator operation doesn t interfere with transmission operation. Controls regenerative braking operation. Enables or disables the auto start and auto stop engine functions. To enable the auto stop function, these conditions must occur: 1. The HCM commands the PCM (Powertrain to unlock the torque converter clutch. 2. Issues the automatic engine stop fuel cut-off command to the PCM. 3. Commands the SGCM (Starter Generator to slow the engine speed. 4. Closes the auxiliary transmission pump relay to activate the auxiliary transmission pump. 5. Monitors hood ajar switch status. 6. Energizes the auxiliary coolant pump. To enable the auto start feature, the HCM: 1. Makes sure the doors are closed via the door jamb switches and the 38 GEARS October 2006

4 BCM (Body. 2. Make sure there s enough fuel available via the fuel level sensor and the PCM (Powertrain. 3. Makes sure the hood is closed via the hood ajar switch. 4. Monitors throttle position and movement via the PCM (Powertrain and TACM (Throttle Actuator. ESCM (Energy Storage The ESCM (Energy Storage Control is mounted in the ESB (Energy Storage Box). The ESCM: Commands BCO (Battery Cut-Off Switch) to open/shut off the 42- volt battery circuit. This occurs during airbag deployment, vehicle side impact, if the ignition switch is in ACCESSORY, RUN, or CRANK position, or when vehicle speed is <3 MPH (4.8 KPH). Controls the BCO (Battery Cut-Off Switch) in service mode (via a scan tool). Communicates 42-volt system status to the IPC (Instrument Panel Cluster). Controls the speed of ESB (Energy Storage Box) 12-volt ventilation fan. ESCM (Energy Storage Control monitors the amount of current flowing through the 42- volt batteries. Monitors individual battery temperature, voltage and state of charge. An inductive current pickup located on negative lead (battery #1) monitors current flow within the system. The ESCM (Energy Storage monitors all major 42-volt system loads, including the starter/generator when functioning as a starter motor, the EHPS (Electro-Hydraulic Power Steering) pump motor, and the APO (Auxiliary Power Outlet) circuits. Communicates data to the HCM (Hybrid over the GM LAN data bus. ESB (Energy Storage Box) The Energy Storage Box is mounted under the rear seat (X cab) and houses the three, 12-volt batteries that make up the 42-volt electrical system. The BCO (Battery Cut-Off Switch) and a manual disconnect switch are also housed within the ESB. PCM (Powertrain The PCM (Powertrain Control is mounted on the driver side of the engine compartment. The PCM monitors: Transmission and engine operation and parameters. Cruise control, fuel level sending unit, TACM (Throttle Actuator and brake switch data. Ignition switch position. [ ] G a s kets designed and manufactured with p e r fo rmance in mind. Build to last and to meet sealing specs you demand as a client. Strong but flexible Gasket coated on all sides Eliminates oil migration through the material Conformable Seals as cast surfaces Developed specifically for transmission fluid Controlled swell to enhance the seal on the inner edge of the flange Improved tensile strength No additional adhesives or sealants required Foldable Re-usable Distributed by: Performance Gasket Concepts Figure 2 GEARS October

5 The Shock of Your Life, Part 1 The PCM also: Controls engine operating outputs, such as the fuel system, transmission, emission system and the ignition system. Interacts with ABS and HVAC controller when the A/C compressor is operating. Communicates and stores diagnostic codes for the HCM, SGCM, EHPS and ESCM Monitors the commands from the HCM (Hybrid regarding the auto start/stop functions. Works to control (in conjunction with the HCM) the automatic engine start/stop functions under these conditions: 1. Brake pedal depressed while in D3 or D4 range. 2. Accelerator pedal is released. 3. Vehicle speed less than 15 MPH. 4. PRNDL switch and PSM/PSA indicate D3, D4 or Park. 5. Transmission temperature is within proper operating range. 6. The SGCM (Starter Generator can generate enough power to restart the engine. 7. The hood is closed. 8. All doors are closed when in Park. 9. Transfer case isn t in four wheel low range. 10. Tow/haul mode hasn t been selected. 11. No system faults have occurred that may jeopardize system s ability to perform the autostart function (no DTCs). ATCM (Active Transfer Case The ATCM is located under the instrument panel and is used to communicate transfer case range position to the HCM (Hybrid. If the transfer case is in low range, the auto start/stop feature won t be allowed to operate. EBCM (Electronic Brake The EBCM is located in the left frame rail and controls the antilock brake system (ABS). The EBCM: Monitors each wheel's rotation rate. Prevents wheel lockup during aggressive braking. Optimizes wheel traction in conjunction with the vehicle's regeneration and energy management systems. EHPS (Electro-Hydraulic Power Steering The EHPS is mounted in the EHPS pump assembly. The EHPS monitors: Brake pedal position. Manual shift lever position. Steering wheel sensor rate of change. Ignition switch. Vehicle speed. Figure 3 Figure 4: HCM (Hybrid From this information, the EHPS: Controls the hydraulic pump output. Provides hydraulic output for power brake boost and the power steering system. Communicates with the other modules. As you can see, hybrid systems are complicated units requiring a lot of system integration. We covered the controllers and their functions. Next time we ll look at how the controllers use the information they receive accomplish their jobs. Until then, remember: there s fire in those wires. 40 GEARS October 2006

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