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.
骨料的輸送和計量，采用了石子和砂疊加計量輸送的皮帶秤裝置。骨料在卸料進入皮帶秤的過程中，因空間的落差存在，使得卸料門接收信號關閉后，有多余骨料進入到皮帶秤中。通過軟件、電氣控制，使其具備能夠自動補償骨料的落差量，準確達到計量的目標值。皮帶秤使用裙邊皮帶進行骨料輸送，皮帶側邊的裙邊結構能防止砂、石子向側邊漏料，保障計量準確。砂計量皮帶采用變頻控制，能根據計量的需要調節輸送的速度，進一步提高計量精度。
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，為達到精確的計量，需要采用更嚴格的措施。攪拌車在進行粉料的配料工作時，粉料通過帶有變頻功能的螺旋輸送機進行輸送后，進入匹配的粉料秤中計量。通過變頻控制對螺旋輸送速度進行調節，初始計量時快速送料，節省時間；計量接近目標值時慢速送料，把控精度。以此在兼顧效率的情況下，實現了粉料的粗、精計量效果。與皮帶秤類似，螺旋輸送機與粉秤之間也存在高度落差，為提升計量精度，粉料計量系統(如圖4)采用了“一增一減”控制算法。其過程如下：當粉秤在輸送、存料階段時，采用增量控制算法，進行落差量的自動補秤；當粉秤在卸料階段時，系統檢測粉秤內存儲量，如重量超出目標值時，系統執行減量控制算法，截留超出的重量供下批次配料使用。由于粉料自身的細微顆粒、容易結塊的特性，粉秤的出料口處的軟連接容易出現積灰、積料的現象，將對計量精度造成不利的影響。對此使用專為粉料卸料設計的異形軟連接，能防止粉料積料產生的拉秤現象，不良影響。通過變頻輸送、“一增一減”、防拉連接這些措施，保障攪拌車中粉料計量準確進行。
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、箱體振動不可避免的情況下，為了保證水和液體外加劑準確計量，采用傳統的單吊點式、以拉式傳感器計量的方式不是選擇。采用拉式傳感器作為計量元件的液體秤，其原理是通過感應計量重量產生的重力應變，轉換為電信號得到重量值，在混凝土攪拌站中應用廣泛。
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.
然而由于其感應靈敏的特性，在進行微小目標值計量時，設備框架的振動、外力微小的擾動等都可能導致計量值的偏離，在結構緊湊、計量要求精確、工況復雜、拌合質量要求高的自密實混凝土攪拌車中，應當有更好的設計。
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.
通過多次試驗驗證，水、液體外加劑使用流量計進行原材料計量，很好的克服了拉式傳感器的缺點。在液體計量系統中采用的流量計，其工作原理是根據電磁感應原理進行流量測量。當水、外加劑這類導體在磁場中做切割磁力線運動時，在管道兩端的電極上產生感應電勢。
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.
通過測量感應電勢，結合其他已知參數換算為水或外加劑的計量重量。在流量計中，感應電壓信號與平均流速呈線性關系，測量精度高；測量電極內置，抗干擾能力強；計量過程不受到振動因素影響，計量過程穩定平穩。
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.
