Crank Sensor IC for Stop-Start

由Eric Burdette和Mike Morris
亚博棋牌游戏Allegro MicroSystems，LLC

Stop-start functionality allows automobiles to conserve fuel by shutting off the engine and restarting it at short intervals, such as at traffic stops. This feature requires advanced sensing technology to be efficient. This article describes start-stop operation and enabling Hall-effect integrated circuits, in particular the Allegro MicroSystems ATS694 and the previous generation ATS658, which are used in this application.

介绍

汽车配备止动功能的汽车通过在静止时关闭燃烧发动机，例如在交通灯处。当驾驶员表示恢复驱动时，将发动机重新启动，例如按下离合器或释放制动踏板。止动系统的宣传燃料经济性改进截止最多5％或10％。此外，通过减少发动机空转时间减少燃料消耗量减少了释放的CO的量₂, a benefit that is propelling extensive implementation in Europe, as automakers strive to meet tightening emissions standards.

开始停止操作

开始停止概念不是一个新的想法;几种1980年代的车型以这种能力释放到生产。过去几十年的技术改进使得停止开始运行更可靠的功能。此外，现代车辆能够快速重启发动机的能力对于广泛的消费者接受这种功能来说至关重要。

Stop-start systems have a great cost-benefit when compared to hybrids that require parallel drive systems. The former rely heavily on existing components, requiring only a few equipment upgrades to achieve the fuel savings. Existing engine control units (ECUs) use inputs from sensors to dynamically adjust engine timing and fuel use to optimize performance. Additional ECU algorithms can be implemented to turn off the combustion engine when not needed. This requires inputs from already monitored systems, such as wheel speed, brake application, and battery status, which is necessary to ensure adequate power to restart the engine and to sustain electronics during the standstill period.

To achieve a restart of the engine, systems rely on a starter-generator or a heavier-duty starter motor (to withstand the increased usage). In addition, information from a crankshaft position sensor is utilized to reduce the time for a restart to just a fraction of a second. In a typical automotive combustion engine, an active sensor is used to monitor a special target on the crankshaft. In order for the ECU to determine the absolute crankshaft position, thereby providing piston position, the sensor must provide direction of target rotation. This direction detection capability enables the system to maintain synchronization throughout a standstill event, even in the presence of engine backlash. Without keeping synchronization, a restart event would likely take longer.

Sensing Technology

亚博棋牌游戏Allegro MicroSystems，LLCoffers several automotive-grade, geartooth, Hall-effect integrated circuits (IC), specifically designed to meets the requirements for crankshaft speed and direction sensing for start-stop systems. These devices are built upon proven Hall technology, which provides digital contactless sensing of a ferromagnetic target. The IC family includes the ATS658 and ATS694, both of which are incorporated into a user-friendly, over-molded IC that integrates the Hall effect circuit with a rare earth magnet. The small package size and integrated magnetic system can be easily assembled and used in conjunction with a variety of target gears and installation air gaps. The combination of the sensor circuit with the back-biasing magnet in Allegro’s manufacturing facility ensures consistent device performance as each IC can be optimized to match a known magnetic circuit.

尽管两个设备之间存在微妙的差异，但ATS658和ATS694都包含三个霍尔元件，用于基于由铁磁靶齿轮的旋转产生的磁刺激产生两个差分信号。然后使用两个信号的相对相位来确定目标旋转的方向。传感器IC提供数字电压输出信号，其中产生短脉冲作为设备面部通过每个目标齿的中心。两个不同的输出脉冲宽度区分目标是否沿前向或相反方向旋转。以这种方式，通过测量输出脉冲的宽度，通过查看连续脉冲之间的周期和目标旋转方向的时段，可以确定目标旋转的速度。

我nternal to these ICs, a number of patented analog and digital signal processing techniques are used. Advanced calibration techniques are used to provide optimal signal offset and amplitude. This calibration, combined with the digital tracking of the signal, results in accurate switching through the full range of installation air gap and target speed.

还实现了独特的信号跟踪方法以在长时间的静止期间维持信号完整性。数字方向检测算法确保在目标方向变化期间不会产生错误的输出脉冲，这可能发生在发动机停止事件期间。这些技术和算法的组合允许这些装置在发动机停止事件中跟踪曲柄目标的绝对位置，确保ECU知道曲轴（并且因此凸轮轴）的确切位置并能够快速重启。

图2.

296089-AN.