Hydraulic System & Control System Of Rear Loading Type Compression Garbage Truck

With the continuous increase of the urbanization rate, the urban population continues to increase, and the phenomenon of siege of domestic garbage is becoming more and more serious, and the garbage processing stations are getting more far from the city center. The cost saving of garbage transfer, efficiency improve, large-scale and intelligence will be increased. High-efficiency, tightness of compression garbage trucks will be the development trend in the future.

The rear compression type garbage truck is mainly composed of the second-class chassis, carriage components, loading mechanism, lifting mechanism, unloading mechanism, hydraulic system, control system and operating system. As shown in the figure, the garbage is loaded by the loading mechanism at the rear of the vehicle. The loading mechanism crushes the garbage, compresses it, squeezes it into an enclosed compartment. And after the carriage is full of garbage, the garbage will be transported to the waste disposal station for unloading. At this time, the loading compartment is lifted, and the rear of the compartment is open, and the unloading mechanism inside the compartment starts to push the compressed garbage and push it all out of the carriage.

The rodless cavity of the shoveling plate circuit is connected to the oil tank by a check valve, and the back pressure valve is connected to the rod chamber. The bidirectional compression of the discharge structure and the loading mechanism is achieved. Because of the back pressure valve connected, the shoveling plate will not retract after it is pushed out,(The directional valve is in neutral position) and garbage can be initially compressed during the filling process. Also different compression ratios can also be achieved by changing the pressure of the back pressure valve.

      And the shoveling plate gradually compress the garbage densely and evenly into the carriage by the continuous external load through replenishment via check valve of rodless cavity until the compartment is fully loaded. And in this case, circumstance like loose front end with compacted middle parts will not occur. 

The lifting circuit adopts a bidirectional hydraulic lock and an oil return throttle valve. The one-way throttle valve on the return circuit of the lifting cylinder is used as a back pressure valve to avoid the problem of shock and vibration when the loading mechanism falls. At the same time, it can precisely control the speed of falling loading mechanism.

In order to reduce the labor intensity of the operators and maintain the reliability of the control system, generally rear-loading type compression garbage trucks will adopt combination valves of manual and pneumatic solenoid valve. Since the chassis power supply is 24V DC, and the direct current directional valve has the disadvantages of small aerodynamic power and high energy consumption, it is not suitable for direct use.

The normal solution is to choose a combination directional valve with manual control handles at one end and small cylinders and solenoid valve integrated at the other end of the valve core.

The cylinder is controlled by a solenoid valve, and the directional valve core is pushed by the cylinder. The pneumatic solenoid valve has the advantages of low energy consumption and long life, and the cylinder can obtain a large operating force. The above advantages make up for the shortcomings of the DC solenoid valve. At present, air brakes are commonly adopted on medium and heavy trucks, which can easily obtain the air source. This combination valve has one valve and two controls, which greatly simplifies the hydraulic and electrical circuits and better adapts the needs of garbage trucks. When the garbage truck is refitted on the light truck chassis, because the chassis power system has no air compressor, if you want to achieve a variety of control methods, you need to choose another type electro & hydraulic controlled combination directional valve.

B: Actuator 

According to the analysis of the hydraulic principle and its action, the actuator can meet the requirements as long as the reciprocating motion is performed, so the actuator shall be a double-acting cylinder. And three-stage oil cylinders are used for general push plate cylinders, and the others are single-stage oil cylinders.

C: Hydraulic oil tank 

The oil tank is used to store oil to ensure that sufficient hydraulic oil is supplied to the hydraulic system. At the same time, it also has the functions of heat dissipation and sedimentation of dirt infiltrating into the oil. Therefore, the oil tank must have sufficient volume and heat dissipation area. 

Control system 

The loading compartment must be returned under a proper delay after being lifted, to ensure that all the garbage inside the carriage is dumped out. And when the shoveling plate is pushed out for discharging, the loading compartment must be lifted before proceeding, otherwise it won’t work. Therefore, according to the action requirements of the work flow, the program control flow is listed (as shown above). In the system, the position of each action is detected by using a proximity switch, which also controls the connection of actions.

  For example, in the loading cycle, the proximity switch is turned on after the scraper is in place, so the skate board slides down to achieve the filling cycle. If there are overloads of stones, metals, and other hard blocks in the garbage, it may affect the compression cycle. Therefore, you can set the conditional statement "set time " in the program and move to the next step instead of forcibly compressing which may cause damage to hydraulic components. Also the proximity switch is used to detect the lifting of the hopper when unloading garbage. If it is no lifted in place, the shoveling plate cannot push out the garbage. Only after the loading compartment is lifted in place, a compression cycle is performed again to remove any possible garbage in the loading chamber.

Though China's compression garbage trucks have developed rapidly in recent years, the level of manufacturing are uneven, and it is necessary to improve them in terms of reliability, safety and efficiency. 

Reliability is mainly to reduce the failure rate of the hydraulic system, which is to solve the problem of " valve sticking". The entire working cycle of the rear loading type compression garbage truck is mainly completed by four sets of oil cylinders, so four three-position four-way directional valves can be used to achieve the actions.  Due to poor working conditions of garbage trucks and the serious pollution, it is difficult to ensure that the " valve sticking " phenomenon will not occur. At this time, the "stuck sticking" can only be solved by increasing the reversing force of the valve spool, or once the "valve sticking occurs, choose manual operation. The Increase of manual operation function not only solves the failure caused by the valve itself, but also solves other problems caused by other reasons. It provides great convenience for installation, debugging and maintenance work, and also ensures high efficiency of compression garbage trucks. 

Safety mainly means that the rear loader needs to be lifted during the daily clear maintenance and repair when discharging the garbage. In order to avoid the sudden drop of the filler caused by accidental damage of the hydraulic oil circuit. Usually, hydraulically controlled check valve or balancing valve are generally adopted to achieve oil circuit protection. However, there is always a section of the oil circuit that is not protected. Especially on the rear-loading type compression garbage truck, this section of the pipeline often has to use a hose, which further exacerbates its danger. However, if the protective oil circuit can be placed at the bottom of the oil cylinder and integrated with the stroke of the oil cylinder, then all external oil pipes and components are protected, and any damage will not make the loader fall accidentally.

Working efficiency

The working cycle time of the loading mechanism determine the operating efficiency of the rear loading type compression garbage truck. Shortening the filling cycle is to improve work efficiency of the garbage trucks.