In the process of producing concrete, the self compacting concrete mixer needs to accurately measure the raw materials such as aggregate, powder, liquid admixture and water. For the mixer truck without fixed outdoor workplace and requiring on-site mixing and pouring, the high-quality raw material metering process can be guaranteed by maintaining the stability and stability of equipment and frame in the metering process. The design is conducive to improve the measurement accuracy and is applied to all aspects of the mixer structure.
骨料的输送和计量，采用了石子和砂叠加计量输送的皮带秤装置。骨料在卸料进入皮带秤的过程中，因空间的落差存在，使得卸料门接收信号关闭后，有多余骨料进入到皮带秤中。通过软件、电气控制，使其具备能够自动补偿骨料的落差量，准确达到计量的目标值。皮带秤使用裙边皮带进行骨料输送，皮带侧边的裙边结构能防止砂、石子向侧边漏料，保障计量准确。砂计量皮带采用变频控制，能根据计量的需要调节输送的速度，进一步提高计量精度。
The belt scale device of superposition metering and conveying of stone and sand is adopted for the transportation and metering of aggregate. In the process of aggregate unloading into the belt scale, due to the drop of space, after the receiving signal of the unloading door is closed, excess aggregate enters the belt scale. Through software and electrical control, it can automatically compensate the drop of aggregate and accurately achieve the measurement target value. The belt scale uses skirt belt for aggregate conveying. The skirt structure on the side of the belt can prevent sand and gravel from leaking to the side and ensure accurate measurement. The sand metering belt adopts frequency conversion control, which can adjust the conveying speed according to the metering needs and further improve the metering accuracy.
粉料的使用量小于骨料的使用量，为达到精确的计量，需要采用更严格的措施。搅拌车在进行粉料的配料工作时，粉料通过带有变频功能的螺旋输送机进行输送后，进入匹配的粉料秤中计量。通过变频控制对螺旋输送速度进行调节，初始计量时快速送料，节省时间；计量接近目标值时慢速送料，把控精度。以此在兼顾效率的情况下，实现了粉料的粗、精计量效果。与皮带秤类似，螺旋输送机与粉秤之间也存在高度落差，为提升计量精度，粉料计量系统(如图4)采用了“一增一减”控制算法。其过程如下：当粉秤在输送、存料阶段时，采用增量控制算法，进行落差量的自动补秤；当粉秤在卸料阶段时，系统检测粉秤内存储量，如重量超出目标值时，系统执行减量控制算法，截留超出的重量供下批次配料使用。由于粉料自身的细微颗粒、容易结块的特性，粉秤的出料口处的软连接容易出现积灰、积料的现象，将对计量精度造成不利的影响。对此使用专为粉料卸料设计的异形软连接，能防止粉料积料产生的拉秤现象，不良影响。通过变频输送、“一增一减”、防拉连接这些措施，保障搅拌车中粉料计量准确进行。
The use of powder is less than that of aggregate. In order to achieve accurate measurement, more stringent measures need to be taken. When the mixer truck is carrying out the mixing of powder, the powder is transported through the screw conveyor with frequency conversion function and then enters the matched powder scale for measurement. The screw conveying speed is adjusted through frequency conversion control, and the material is fed quickly during initial metering to save time; When the metering is close to the target value, feed slowly to control the accuracy. In this way, the coarse and fine metering effect of powder is realized under the condition of considering efficiency. Similar to the belt scale, there is also a height drop between the screw conveyor and the powder scale. In order to improve the metering accuracy, the powder metering system (as shown in Figure 4) adopts the "one increase and one decrease" control algorithm. The process is as follows: when the powder scale is in the conveying and storage stage, the incremental control algorithm is adopted to automatically replenish the drop; When the powder scale is in the unloading stage, the system detects the memory reserves of the powder scale. If the weight exceeds the target value, the system executes the reduction control algorithm to intercept the excess weight for the next batch of batching. Due to the characteristics of fine particles and easy caking of powder, the soft connection at the discharge port of powder scale is prone to ash and material accumulation, which will have an adverse impact on the measurement accuracy. In this regard, the special-shaped soft connection specially designed for powder unloading can prevent the scale pulling phenomenon caused by powder accumulation and eliminate adverse effects. Through frequency conversion transportation, "one increase and one decrease" and anti pull connection, the accurate measurement of powder in the mixer is guaranteed.
在框架、箱体振动不可避免的情况下，为了保证水和液体外加剂准确计量，采用传统的单吊点式、以拉式传感器计量的方式不是选择。采用拉式传感器作为计量元件的液体秤，其原理是通过感应计量重量产生的重力应变，转换为电信号得到重量值，在混凝土搅拌站中应用广泛。
When the vibration of frame and box is inevitable, in order to ensure the accurate measurement of water and liquid admixture, the traditional single hanging point and pull sensor measurement is not the best choice. The principle of liquid scale using pull sensor as metering element is to convert the gravity strain generated by metering weight into electrical signal to obtain the weight value, which is widely used in concrete mixing plant.
然而由于其感应灵敏的特性，在进行微小目标值计量时，设备框架的振动、外力微小的扰动等都可能导致计量值的偏离，在结构紧凑、计量要求精确、工况复杂、拌合质量要求高的自密实混凝土搅拌车中，应当有更好的设计。
However, due to its sensitive sensing characteristics, the vibration of the equipment frame and small disturbance of external force may lead to the deviation of the measured value when measuring the small target value. In the self compacting concrete mixer with compact structure, accurate measurement requirements, complex working conditions and high mixing quality requirements, there should be a better design.
通过多次试验验证，水、液体外加剂使用流量计进行原材料计量，很好的克服了拉式传感器的缺点。在液体计量系统中采用的流量计，其工作原理是根据电磁感应原理进行流量测量。当水、外加剂这类导体在磁场中做切割磁力线运动时，在管道两端的电极上产生感应电势。
Through many tests, it is verified that the flowmeter is used for raw material measurement of water and liquid admixtures, which overcomes the shortcomings of pull sensor. The working principle of the flowmeter used in the liquid metering system is to measure the flow according to the principle of electromagnetic induction. When conductors such as water and additives move to cut magnetic lines of force in a magnetic field, an induced potential is generated on the electrodes at both ends of the pipeline.
通过测量感应电势，结合其他已知参数换算为水或外加剂的计量重量。在流量计中，感应电压信号与平均流速呈线性关系，测量精度高；测量电极内置，抗干扰能力强；计量过程不受到振动因素影响，计量过程稳定平稳。
By measuring the induced potential, combined with other known parameters, it is converted to the measured weight of water or admixture. In the flowmeter, the induced voltage signal has a linear relationship with the average flow rate, and the measurement accuracy is high; Built in measuring electrode, strong anti-interference ability; The metering process is not affected by vibration factors, and the metering process is stable.
