1987 Acura Legend Coupe ALB/ SRS
ANTI-LOCK BRAKING (ALB) SYSTEM
The Land LS versions of the Legend Coupe are equipped with an Anti-Lock Braking (ALB) system that prevents lock-up at any wheel. It was designed by Honda Research and Development Co., Ltd. This in-house approach was chosen to permit more efficient integration of the ALB system into the Coupe's design and to assure that the latest appropriate technology could be utilized. It has been designated ALB to distinguish it from systems made by Bosch, Teves, Lucas and others that are being used by a number of auto makers.
The ALB system is substantially different from the others in both principle and design. Honda holds numerous patents on new technology created during the ALB system's development.
Unlike other systems, Honda's ALB has two hydraulic circuits linked by an electronic control circuit. The primary hydraulic system functions in the conventional manner, using a master cylinder and power assist to operate the brake calipers. Under normal conditions, this system provides all the braking.
Sensors monitor velocity at each wheel, constantly relaying this information to the Electronic Control Unit (ECU). It analyzes the data, and if it determines that lock-up is imminent, the ALB system is activated. The system has its own hydraulic reservoir, pump and a modulator unit which contains three pairs of solenoids (one pair for each front wheel, and one pair for the rear wheels) and four control pistons (one for each brake caliper). The solenoids direct the pistons, cycling them up to ten times a second The two hydraulic systems intersect at each control piston.
In actual use, this is what happens: Impending lock-up is sensed at any wheel. The computer actuates the solenoid valves, which modulate the control pistons. The action of these pistons causes the pressure of the fluid in the primary line to fluctuate, or cycle, applying and releasing the brake caliper up to ten times a second. This allows the wheel to continue to rotate so the driver can maintain steering control even under maximum braking.
A key feature of the Honda ALB design lies in the independence of the two hydraulic circuits. It is a "fail safe" system. Should a failure occur in the ALB hydraulic circuit, normal braking will be provided by the primary hydraulic circuit. If the ALB system computer detects failure, an instrument panel warning light goes on.
Also, continuous pressure in the ALB circuit makes failure detection a constant function. (The ALB pump maintains this pressure by operating intermittently.) Thus, any system leak is readily apparent.
SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
The driver's side of the Acura Legend LS Coupe is fitted with an air bag and knee bolster that are designed to supplement the car's three-point seat belt. This system was designed specifically for the Legend Coupe by Honda Research and Development Co., Ltd. and incorporates numerous patented innovations which help assure the system's integrity and reliability.
The air bag is housed in the steering wheel hub. In the event of a frontal crash that exceeds the force of a ten mph barrier impact, the bag is inflated within 30-40 milliseconds to cushion the driver's head and upper torso, and then quickly deflates.
The system uses four sensors to detect an impact. Two are located at the forward right and left corners of the car; two are beneath the dashboard in the passenger compartment. These sensors detect an impact within ten milliseconds and activate a propellant that inflates the air bag. Before the air bag can be deployed a signal must be received from both a front and a passenger compartment sensor. This is to prevent inadvertent deployment should one of the front sensors be struck by a localized impact; significant sudden motion at the passenger compartment must also be detected before the bag can be triggered.
To assure durability, the front sensors are epoxy potted and hermetically sealed. And, in case the electrical system fails in a crash, the CPU contains a back-up capacitor which stores electricity for 10-15 seconds, long enough to deploy the air bag. However, for service the system is disarmed simply by disconnecting the battery.
The SRS system is designed to be maintenance-free for a minimum of ten years. Special components have been developed to assure its integrity and longevity. They include coiled-wire reel on the steering column which permits steering wheel operation without the use of slip ring or sliding contacts; a double-sealed, thick-walled metal capsule to contain the solid propellant which inflates the bag; and eight multi-pin connectors in the main wiring system with gold-plated pins for better conductivity and corrosion resistance.