Introduction to wheeled bulldozers
Tire bulldozers (hereinafter referred to as wheeled bulldozers) are a type of construction machinery that is modified from ordinary loader chassis and has strong adaptability to working conditions. Compared with crawler bulldozers, it can complete earthwork operations such as pushing, digging, leveling, and backfilling at a faster speed and higher efficiency; at the same time, it has very strong mobility and flexibility, and it is quite convenient to transfer to the construction site. Therefore, it is widely used in civil construction, road construction, airports, dams, mining, ports and docks, farmland transformation, and national defense engineering construction. Compared with loaders, its structure and manufacturing process are relatively simple. The biggest difference is the different structure and principle of the working device.
What are the characteristics of wheeled bulldozers
1. Structural composition:
The wheeled working device is front-mounted like the loader working device. Because its structural appearance and connection method vary greatly, the front frame of the wheeled bulldozer needs to be redesigned.
As can be seen from the above figure: the wheel push working device consists of a push shovel assembly, two push shovel connecting brackets, two large arms, a horizontal push rod assembly that can be adjusted left and right, a vertical support rod, a lifting cylinder and a tilting cylinder. The push shovel assembly is hinged to the front frame through the large arm and the lifting cylinder; it is fixedly connected to the large arm through the left and right horizontal push rod assemblies, the vertical support rod, and the tilting cylinder, so that the various components are connected into an organic whole, which can realize the two functions of lifting and lowering and tilting the push shovel left and right.
2. Structural features:
(1) The push shovel weldment adopts a straight shovel closed structure design, which greatly enhances the overall strength and rigidity of the push shovel. It is firm, reliable and durable, and is most suitable for the stripping operation of the original soil layer.
(2) The push shovel assembly and the five wear-resistant blades are fastened with countersunk bolts to facilitate the replacement of the blades after wear; at the same time, the blades are made of special wear-resistant materials that are resistant to low temperature and cold brittleness, which are suitable for rock-type operating environments in cold areas, effectively extending the service life of the push shovel assembly.
(3) The left and right arms are designed as a box-type structure, which is light in weight, strong in strength, and has good rigidity, and can well meet the working requirements.
(4) An adjustable horizontal push rod assembly and vertical support rod are used to change the blade’s top view and tilt angle. This ensures that the blade maintains a certain cutting angle and a certain spatial position, so that the wheel push shovel can operate normally in different soil types and sites.
(5) The “TT”-shaped assembly structure is adopted between the push shovel assembly and the left and right arms, so that the force on the push shovel is more uniform, which is conducive to protecting the push shovel; at the same time, it is easier to achieve the blade’s cutting angle.
(6) The entire working device has been optimized and designed with CAD technology, the structural parts are reasonably designed, the force condition of each part is good, the technical parameters and performance indicators are advanced, the rise, fall and tilt of the push shovel are flexible, stable and reliable, and the operating efficiency is high, reaching the first-class level of similar working devices in China.
Working principle of wheel bulldozer
The hydraulic system of the working device consists of system oil tank, working oil pump, multi-way reversing control valve (distribution valve), bulldozer lifting cylinder, bulldozer tilting cylinder, oil pipe joint and other components. When bulldozer is working, the working oil pump sucks oil from the oil tank, and then changes the flow direction of the oil through the multi-way reversing control valve, so as to control the movement direction of the lifting cylinder and the tilting cylinder to meet the requirements of various working actions.
When the lifting lever and the tilting lever in the cab are both in the middle position, the lifting slide valve and the tilting slide valve of the multi-way control valve are in the closed position, and the oil from the working oil pump returns directly to the oil tank through the multi-way valve, which is not working at this time.
When the lifting lever is operated in the lifting (lowering) position, the flexible shaft controls the lifting slide valve to move to the right (left) to the working position, and the oil of the oil pump opens the one-way valve and enters the small chamber (large chamber) of the lifting cylinder through the oil inlet of the multi-way valve, thereby pushing the reciprocating motion of the piston rod to achieve the lifting or lowering of the shovel. Finally, the hydraulic oil flows back to the oil tank from the large chamber (small chamber) of the lifting cylinder through the oil return port of the multi-way valve.
When the lifting lever is in the floating position, the lifting slide valve is at the leftmost end of the control valve. At this time, the oil inlet cavity and the oil return cavity are connected, so that the large and small chambers of the lifting cylinder are connected and are in a low-pressure state. The cylinder is in a free floating state due to the weight of the working device and the ground force.
Similarly: when the roll lever is operated to the left (right) tilt position, the roll slide valve moves to the left (right), the hydraulic oil pushes the one-way valve open and enters the large chamber (small chamber) of the roll cylinder through the oil inlet of the multi-way valve, pushing the piston rod to extend and retract, thereby realizing the left (right) tilt of the bulldozer. Finally, the hydraulic oil flows back to the oil tank from the small chamber (large chamber) of the roll cylinder through the oil return port of the multi-way valve.
The lifting and lowering of the bulldozer is achieved by the extension and retraction of the lifting cylinder, and the process is very clear.
When the roll lever is operated, the piston rod of the roll cylinder will extend and retract under the action of hydraulic oil. At this time, the resultant force of the cylinder on the bulldozer is Fa. Because the bulldozer is hinged on the boom, its horizontal force Fax will not cause the bulldozer to move forward and backward, and the vertical force Fay is one of the bulldozer’s upward forces. At the same time, the resultant force Fb of the cylinder on the boom support compresses the BD section of the boom CD, and its vertical force Fby has a tendency to cause the bulldozer to sink. According to the moment balance equation of the boom around point D, it can be known that: Fc = Fby × L2/L1, and from the principle of action and reaction force, it can be known that the vertical force Fc’ = Fc acting on the bulldozer at point c is vertically downward. Therefore, under the resultant force of the vertical force F = Fay-Fc’, the bulldozer rotates a certain angle in the plane perpendicular to the longitudinal axis of the wheel pusher, forming a roll angle, causing the bulldozer to roll.
By repeatedly extending and retracting the tilt cylinder, the dozer can successfully achieve the movement process of tilting clockwise or counterclockwise around the longitudinal axis of the wheel in the vertical plane.
