With the rapid development of concrete production and construction technology, some countries have gradually adopted the method of centralized mixing and commercial supply of concrete. The concrete is provided by a special concrete mixing plant and then transported by concrete mixer trucks to various construction sites. The structural principle and maintenance of the concrete mixer truck are briefly introduced.
â—† The composition and working principle of concrete mixer truck
The concrete mixer truck is composed of a special chassis for the vehicle chassis and concrete mixing and transportation. The chassis of the concrete mixer truck produced in China uses the second type of universal chassis provided by the vehicle manufacturer. Its specialized agencies mainly include power take-off devices, front and rear brackets for mixing drums, speed reducers, hydraulic systems, mixing drums, operating mechanisms, and cleaning systems. Its working principle: The power of the chassis of the vehicle is taken out through the power take-off device, and the variable pump of the hydraulic system is driven, the mechanical energy is converted into hydraulic energy and transmitted to the quantitative motor, the motor then drives the speed reducer, and the speed reducer drives the stirring device to perform the concrete Stir.
1. Power take-off device
The domestic concrete mixer truck uses the power of the main engine. The function of the power take-off device is to take out the engine power by operating the power take-off switch, and the hydraulic system drives the mixing drum to stir the shaking drum in a forward rotation during the feeding and transportation, so as to facilitate the feeding and stirring of the concrete, at the time of discharging Reverse rotation, cut off the power connection with the engine after the end of the work.
2ã€Hydraulic system
The engine power taken out by the power takeoff is converted into hydraulic energy (displacement and pressure), and then the motor output is mechanical energy (rotation speed and torque), which provides power for the rotation of the mixer drum.
3, reducer
The speed of the motor output in the hydraulic system is decelerated and transmitted to the mixing drum.
4, operating mechanism
a. The direction of rotation of the mixer drum is controlled so that it rotates in the forward direction during feeding and transportation, and rotates in reverse when discharging.
b. Control the speed of the mixer
5, stirring device
It consists of a mixing drum and its auxiliary support components. The mixing drum is a concrete loading container. It is made of high-quality wear-resistant steel sheet. In order to be able to automatically install and discharge concrete, special spiral blades are welded on the inner wall. As the concrete rotates, the concrete moves in the direction of the spiral of the blade and is mixed and stirred during continuous lifting and turning. During feeding and transportation, the mixing drum rotates forward and the concrete moves inward along the blades. When the material is discharged, the mixing drum is reversed and the concrete is discharged outward along the blades. The rotation of the mixer drum is ensured by a hydraulic drive. The loading capacity is 3 to 6 cubic meters. The concrete mixer truck is generally driven by the automobile engine to drive the hydraulic pump through the power output shaft, and then the hydraulic motor is used to drive the mixing drum by high-pressure oil. When the loading capacity is 9 to 12 cubic meters, the hydraulic pump driven hydraulic motor is driven by the vehicle-mounted auxiliary diesel engine. The blade is the main component in the stirring device. Damage or severe wear will cause uneven mixing of the concrete. In addition, if the angle of the blade is unreasonable, it will cause the concrete to segregate.
6, cleaning system
The main function of the cleaning system is to clean the mixing drum and sometimes it is also used for dry mixing during transportation. The cleaning system also cools the hydraulic system.
â—† Maintenance and repair of concrete mixer trucks
As a transport vehicle, a concrete mixer truck must comply with the regulations of the Ministry of Communications of the People's Republic of China on Decree No. 13 of 1990 issued by the Ministry of Communications for maintenance and repairs, and implement the maintenance and repair system of “regular testing, compulsory maintenance, and repair as requiredâ€. Under this premise, combined with the actual situation of the concrete mixer truck, do a good job of maintenance and repair. In terms of daily maintenance, in addition to the routine maintenance of automobile engines, chassis, etc., concrete mixer trucks must also perform the following maintenance work.
1, cleaning concrete tank (mixer) and inlet and outlet
Because the concrete will solidify into a hard block in a short time, and it is corrosive to the steel and paint, after every use of the concrete tank, the concrete adhered to the concrete tank and the inlet and outlet must be cleaned daily. Serious work. These include:
a. Rinse the feed inlet with water before each charge to keep the feed inlet moist while charging.
b. Fill the cleaning water tank that comes with the vehicle while filling;
c. After filling, wash the inlet and clean the remaining concrete near the inlet;
d. After unloading at the construction site, flush the discharge chute, and then add 30-40 L of cleaning water to the concrete tank; keep the concrete tank slowly turning at a slow speed while the vehicle is returning;
e. Remember to drain the concrete tank before loading the next time;
f. Clean the concrete tank and the surrounding of the inlet and outlet at the time of daily work to ensure that there is no cement and concrete agglomeration.
If these tasks are not carried out carefully once, they will cause great trouble for future work.
2, maintenance drive device
The function of the drive device is to drive the rotation of the concrete tank. It consists of a power take-off device, a cardan shaft, a hydraulic pump, a hydraulic motor, a control valve, a hydraulic oil tank and a cooling device. If this part is stopped due to a malfunction, the concrete tank will not be able to turn, which will lead to the scrapping of the concrete in the car, and even cause the concrete of the whole tank to condense in the tank, causing the concrete mixer truck to be scrapped. Therefore, whether the driving device is reliable is a problem that must be highly regarded in use. In order to ensure that the drive is sound and reliable, the following maintenance work should be done:
a. The universal rotating part is a part with frequent faults. Grease should be added on time, and the wear condition should be checked frequently and repaired and replaced in time. The team should have a spare universal shaft assembly to ensure that it can resume work within tens of minutes in the event of a failure.
b. Keep the hydraulic oil clean. The poor working environment of concrete mixer trucks must prevent dirt and cement from entering the hydraulic system. Hydraulic oil should be replaced regularly as required by the user manual. Once the hydraulic oil is found mixed with water or sand during inspection, the hydraulic system must be shut down immediately to replace the hydraulic oil.
c. Ensure that the hydraulic oil cooling device is effective. It is necessary to regularly clean up the hydraulic oil radiator to prevent the radiator from being blocked by the cement, check whether the radiator electric fan is running normally, and prevent the hydraulic oil temperature from exceeding the standard. Hydraulic pressure as long as the hydraulic oil to ensure that the general failure is not much; but different manufacturers, the service life is not the same.
3, pay attention to the tire repair
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