Today we are going to introduce another popular application of the MCH heater used for oxygen senor, also called lambda sensor(O2 SENSOR).

LAMBDA SENSOR (O2 SENSOR)

The lambda sensor, also called lambda probe, measures the level of oxygen in exhaust gases and it’s placed on the engine exhaust. By analyzing the waveforms of operation of the lambda sensor in different modes of engine operation, functioning of the sensor itself can be assessed as well as the functioning of the engine management system on the whole. Sign of a malfunctioning lambda sensor is increased fuel consumption, vehicle dynamics reduction, loss of engine power, erratic idling or incorrect idle speed.

What is an oxygen sensor and how it works

Petrol engines require an exact air-fuel mixture proportion for a proper operation. The proportion, in which the fuel burns completely and effectively, is called a stoichiometric and is exactly 14.7:1. This means that one part of fuel must be mixed with 14.7 parts of air. In practice, this air-fuel proportion varies depending on the engine operation mode and the mixture formation. Thus the engine is uneconomic.

The excess air coefficient – L (lambda) characterizes how far is the actual fuel-air mixture from the stoichiometric (14.7:1). This mixture is considered optimal and in this case L = 1. If L < 1, we have a lack of air and the mixture is enriched. When L = 0.85 – 0.95 engine power is increased. If L > 1, there is an excess of air and the mixture is leaned. Engine power drops down when L = 1.05 – 1.3, but the economy rises. At L > 1.3 mixture becomes impossible to ignite and engine misfire occurs. Petrol engines reach their maximum power when a lack of air 5-15% (L = 0.85 – 0.95) is present, and a minimum fuel consumption is achieved with an excess air of 10 – 20% (L = 1.1 – 1.2).

Thereby when the engine is working, the proportion L is constantly varying in the range 0.9 – 1.1 and this is the lambda regulation operating range. When the engine warms up to its operating temperature and it’s not loaded (i.e. idling), keeping the equality L = 1 is essential in order the catalytic converter to completely fulfill its purpose and reduce the vehicle’s emissions to a minimum.

Oxygen sensor is mounted on the exhaust manifold so that exhaust gases can be on the streamline of its working surface. In essence the oxygen sensor is a galvanic current source, which changes its output voltage according to the temperature and the environment oxygen content. Depending on the exhaust gases oxygen concentration, a different output signal appears. Shape of this signal depends on the type of material the sensor is made from. Thus the oxygen sensor reports the onboard controller the amount of oxygen in exhaust gases. Clock edge of the signal between its “high” and “low” state, is negligible and can be ignored. The onboard controller receives signal from the oxygen sensor, compares it with a value stored in its memory and if the signal differs from the optimal for the current mode, it adjusts the fuel injection duration in both directions. Thus, by the implementation of a feedback and a correct operation mode, a maximum fuel economy and minimum harmful gases, is achieved.

Types of oxygen sensors
According to the substance used in their sensitive element, are:
Zirconium (zirconium oxide)
Titanium (titanium oxide)
Wideband

According to their design:
Single-wire lambda sensor
Two-wire lambda sensor
Three-wire lambda sensor
Four-wire lambda sensor

Single-wire lambda sensor was used in the early injection systems with a feedback (lambda regulation). It has only one terminal, which is the signal terminal. Sensor ground is its housing and it connects to the engine ground through the exhaust pipes.

Two-wire lambda sensor has a separate grounding cable. It was used in the early injection systems with a feedback (lambda regulation) also.

Disadvantage of the single-wire and the two-wire sensors is that their operating temperature range starts at 300 ºC. Sensor will not work and will not produce a signal until this temperature is reached. It was necessary for the sensor to be mounted as close to the engine cylinders as possible in order to heat and wrap from the hottest exhaust gases stream. Process of heating the sensor slows down the regulation process of the onboard controller because of the feedback. In addition, using the exhaust pipe as a signal ground requires sensor’s thread to be coated with a special electrically conductive paste, which increases the possibility of a bad contact in the feedback circuit.

In the three-wire lambda sensors, is a special heating element inside which is constantly turned on when the engine is working and thus it’s reducing the heating time of the sensor to the working temperature. This allows installation of the sensor on the exhaust manifold, near the catalytic converter. Disadvantage is the need of electrically conductive grease.

In the four-wire oxygen sensors – two of the terminals are the heater terminals and the other two, the signal terminals.

The structure of the ceramic heater in the oxygen sensor

The picture of MCH ceramic heater for oxygen sensor

Why use MCH heater?
-Quick Heating
-Temperature Stability
-Energy Efficiency:
-Uniform Heating
-Compact Design

The properties of MCH heater

Blow is the Temperature curve and TCR value for MCH heater

More application for MCH heater
E-cig, 3D printer, soldering iron, smart bide/Instant water heating, new energy vehicle, small home appliances such as kettles, hair straighteners, curlers, hair dryer etc.

Conclusion
MCH heaters have great performance for the oxygen sensor by offering rapid heating, precise temperature control, and energy efficiency. These advanced heating elements enable oxygen sensor to work with greater accuracy and effectiveness.

If you have any question about the MCH heater, welcome to contact us at sales@innovacera.com.

今天，我们将介绍 MCH 加热器用于氧传感器的另一种常见应用，也称为氧传感器 (O2 SENSOR)。

氧传感器 (O2 SENSOR)

氧传感器，也称为氧探头，用于测量废气中的氧含量，放置在发动机排气管上。通过分析氧传感器在不同发动机运行模式下的运行波形，可以评估传感器本身的功能以及整个发动机管理系统的功能。氧传感器故障的迹象是油耗增加、车辆动力下降、发动机功率损失、怠速不稳或怠速不正确。

什么是氧传感器及其工作原理

汽油发动机需要精确的空气-燃料混合比例才能正常运行。燃料完全有效燃烧的比例称为化学计量，精确为 14.7:1。这意味着一份燃料必须与 14.7 份空气混合。实际上，这种空气-燃料比例会根据发动机运行模式和混合气形成情况而变化。因此，发动机是不经济的。

过量空气系数 – L（lambda）表示实际燃料-空气混合物与化学计量（14.7:1）的距离。这种混合物被认为是最佳的，在这种情况下 L = 1。如果 L < 1，则空气不足，混合物变浓。当 L = 0.85 – 0.95 时，发动机功率增加。如果 L > 1，则空气过量，混合物变稀。当 L = 1.05 – 1.3 时，发动机功率下降，但经济性上升。当 L > 1.3 时，混合物无法点燃，发动机失火。当空气不足 5-15%（L = 0.85 – 0.95）时，汽油发动机达到最大功率，而当空气过量 10 – 20%（L = 1.1 – 1.2）时，燃油消耗最小。

因此，当发动机工作时，比例 L 不断在 0.9 – 1.1 范围内变化，这是 lambda 调节工作范围。当发动机升温至工作温度且未加载（即怠速）时，保持 L = 1 的相等性对于催化转化器完全实现其目的并将车辆的排放量降至最低至关重要。

氧传感器安装在排气歧管上，这样废气就可以流经其工作表面。本质上，氧传感器是一个电流源，它会根据温度和环境氧含量改变其输出电压。根据废气中的氧浓度，会出现不同的输出信号。该信号的形状取决于传感器的材质类型。因此，氧传感器会向车载控制器报告废气中的氧气含量。信号在其“高”和“低”状态之间的时钟边缘可以忽略不计。车载控制器接收来自氧气传感器的信号，将其与存储在其内存中的值进行比较，如果信号与当前模式的最佳值不同，则在两个方向上调整燃油喷射持续时间。因此，通过实施反馈和正确的操作模式，可以实现最大的燃油经济性和最小的有害气体。

氧气传感器的类型
根据其敏感元件中使用的物质，有：
锆（氧化锆）
钛（氧化钛）
宽带

根据其设计：
单线氧传感器
双线氧传感器
三线氧传感器
四线氧传感器

单线氧传感器用于具有反馈（氧调节）的早期喷射系统。它只有一个端子，即信号端子。传感器接地是其外壳，它通过排气管连接到发动机接地。

双线 氧传感器有单独的接地电缆。它也用于早期的带有反馈（氧调节）的喷射系统。

单线和双线传感器的缺点是它们的工作温度范围从 300 ºC 开始。在达到此温度之前，传感器不会工作，也不会产生信号。必须将传感器安装在尽可能靠近发动机气缸的位置，以便加热并包裹最热的废气流。由于反馈，传感器加热过程会减慢车载控制器的调节过程。此外，使用排气管作为信号接地需要在传感器的螺纹上涂上特殊的导电膏，这增加了反馈电路接触不良的可能性。

在三线氧传感器中，内部有一个特殊的加热元件，当发动机工作时，加热元件会持续打开，从而缩短传感器加热到工作温度的时间。这样可以将传感器安装在排气歧管上，靠近催化转换器。缺点是需要导电油脂。

在四线氧传感器中 – 其中两个端子是加热器端子，另外两个是信号端子。

氧传感器中陶瓷加热器的结构

氧传感器的 MCH 陶瓷加热器 图片

为什么使用 MCH 加热器？
-快速加热
-温度稳定性
-能源效率：
-均匀加热
-紧凑设计

MCH加热器性能

下图为 MCH 加热器的温度曲线和 TCR 值

MCH加热器更多应用
电子烟、3D打印机、烙铁、智能坐浴盆/即热式热水器、新能源汽车、水壶、直发器、卷发器、吹风机等小家电

结论
MCH 加热器通过提供快速加热、精确温度控制和能源效率，为氧气传感器提供了出色的性能。这些先进的加热元件使氧气传感器能够以更高的精度和效率工作。

如果您对 MCH 加热器有任何疑问，欢迎通过 sales@innovacera.com 与我们联系。