Top technologies of the year

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December 2002
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Toyota adds two hybrids

The main THS-M components for the Crown are a motor/generator, inverter, and a 36-V lead-acid battery.

From the middle of last year, hybrid-electric technology pioneer Toyota has added two new hybrid vehicles—the Estima Hybrid minivan and Crown mild-hybrid sedan. They follow the series-hybrid Coaster minibus that preceded the Prius four-door sedan in 1997. More than 60,000 Priuses have been delivered, mostly in Japan but also in the U.S. and Europe.

The main components of the Crown's THS-M (Toyota Hybrid System-Mild) are a motor/generator, an inverter, and a 36-V lead-acid battery package. The Crown is primarily motivated by a gasoline-direct-injection 3.0-L inline six driving the rear wheels via a four-speed automatic. A 36-V, 3-kW, three-phase ac motor/alternator-generator is mounted alongside the engine and driven via a ribbed belt. A 36-V battery feeds electricity to the motor/generator and is recharged by the motor/generator when driven by the engine. The THS-M assists the vehicle in moving off from standstill while the engine is stopped to reduce emissions and conserve fuel. When the brake pedal is released, the motor cranks the engine to near idle speed to move off. Braking energy is recovered by the motor/generator and fed to the battery.

The Estima Hybrid THS-C includes these front- and rear-wheel drivetrains along with a NiMH battery pack.

The Estima Hybrid is the most sophisticated of Toyota's hybrids and features the "world's first" electric on-demand four-wheel-drive system, called E-Four. The Estima's parallel-hybrid THS-C front powertrain comprises an internal combustion (IC) engine; a double-pinion, planetary-gear, power-switching device and twin clutches; and a 216-V, 13-kW motor/generator producing 110 N•m (81 lb•ft). Denso Corp. co-developed the "world's first" belt-driven integrated starter generator (ISG) for the Estima. The rear-wheel drivetrain has its own 216-V motor/generator rated at 18 kW and 108 N•m (80 lb•ft). The IC engine can assist the twin motors to drive all four wheels for short bursts of acceleration.

The THS-C chooses, alternates, and combines the three power sources, employing either or both of the twin motor/generators to replenish the compact NiMH battery pack placed under the third-row seat. The Estima Hybrid's brake system is as advanced as the powertrain; an electronically controlled, hydraulically assisted system controls the four brakes independently for optimum retardation and stability.

For more information from Denso, circle 50

Delphi improves Cadillac's ride

In mid MY2002, the Cadillac Seville STS traded in its continuously variable road-sensing suspension (CVRSS) struts for Delphi Corp.'s next-generation variable damping system called MagneRide. According to Fred Wood, Development Engineer for the Seville, MagneRide reacts at least five times faster than the current damper, enabling improved handling, ride quality, and road isolation, as well as safety.

The MagneRide semi-active suspension system has no electromechanical valves or small moving parts for quieter operation—an industry first, according to Delphi. The system uses magnetorheological (MR) fluid-based monotube struts and shock absorbers. Its sensor set consists of a relative position sensor between each suspension control arm and the vehicle body, as well as a lateral accelerometer and steering-wheel angle sensor from Cadillac's Stabilitrak system. Other components are an onboard controller and an optional leveling compressor module.

Delphi and Lord Corp. co-developed the MR fluid, which consists of suspended iron particles in a base fluid of synthetic hydrocarbon specifically for the shock-absorber application. In its "off" state, the MR fluid is not magnetized, and the iron particles are dispersed randomly; however, in the "on" state, the applied magnetic field aligns the metal particles into fibrous structures, changing the fluid rheology and thus regulating the damping properties. According to Delphi, the MR fluid can change from a mineral-oil-like consistency for low damping forces to a jelly-like one for high damping within 1 ms. Among the benefits are better control of vehicle body motions and reduced wheel bounce, improved road-holding on uneven surfaces and during braking, and a reduction in high-frequency road disturbances transferred through the dampers.

For more information from Delphi, circle 51; from Lord, circle 52

Bosch electrohydraulic brakes for SL

The Mercedes-Benz SL has an impressive package of dynamic handling control systems that includes a new electrohydraulic brake system Mercedes-Benz calls Sensotronic Brake Control (SBC). The system was co-developed with Robert Bosch GmbH, which labels it the electrohydraulic brake (EHB). Among its most important performance features are the dynamic building up of brake pressure and the precise monitoring of driver and vehicle behavior using sensors. In anticipation of emergency situations, SBC increases brake-line pressure and readies the brakes so that they can grip instantly with full force when the brake pedal is pressed. In addition, variable brake proportioning offers enhanced safety when braking on bends.

The EHB provides the brakes with a fluid supply from a hydraulic high-pressure reservoir sufficient for several braking events. A piston pump driven by an electric motor enables a controlled brake fluid pressure of 14 to 16 MPa (2030 to 2320 psi) from a gas diaphragm reservoir. When the brakes are activated, the EHB control unit calculates the desired target brake pressures at the individual wheels. Braking pressure for each of the four wheels is regulated individually via a wheel pressure modulator, which consists of one inlet and one outlet valve controlled electronically.

"The crucial performance feature of the EHB is that it raises braking comfort," according to Gunther Plapp, Executive Vice President, Development, ABS and Brakes Division of Robert Bosch GmbH. A controller intervenes early and stabilizes the vehicle without the typical ABS feedback; this allows for such functions as stability and adaptive cruise control to be designed in a less intrusive way. Additional features include a dry-brake function with regular, short, and weak brake impulses to eliminate the brake-disc water film, which typically occurs in wet conditions, and to ensure immediate braking.

For more information from Bosch, circle 53

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