原文传递
STOPPING POWER
| 题名： | STOPPING POWER |
| 正文语种： | eng |
| 摘要： | The first stop on a discovery mission around secondary braking systems starts with head of product at Volvo Trucks, John Comer. He states: "There are three types of auxiliary retardation: engine brakes, gearbox retarders and there was a Voith system many years ago called a PriTarder, which was an impeller inside the cooling system to slow down the crank."Volvo chose to go with an engine brake as its primary option, the current version of which is VEB+. "It was the change in engine design in the early '90s that allowed us to do that," Comer says. "When we designed the D12 engine for FH originally, forthe launch in 1993, we went to a single-piece head with an overhead cam," he says. Two additional lobes were then added to that overhead cam which, when engaged, opened and closed the exhaust valves as the engine brake was switched on and off. "You're basically closing the cylinder and creating a compressor, which slows or stalls the engine," he explains.The next step on from this came in 2001, when disc brakes with EBS were introduced to Volvo's FH and FM Version 2 truck range. "Originally VEB was switched on the dashboard, but from Version 2 FH it has been a stalk function, which means it can have several graduations," Comer continues. "With the launch of the I-Shift gearbox and the integrated CAN-Bus, you've got the gearbox, engine and engine brake all speaking to each other." That opened the door to blended braking, where service and secondary brakes work in conjunction. "So, for example, if you press the B Mode button at the end of the stalk, the engine will look to drop gears, because the engine brake is most efficient at high revs."Today's VEB+ is simply a reworking of that original engine brake, but with an additional hydraulic circuit to engage the cam, making it much more powerful. |
| 出版年： | 2023 |
| 期刊名称： | Transport engineer |
| 期： | Oct. |
| 页码： | 28-30 |
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