1、 Characteristics of crawler bulldozer walking device
The driving system of crawler bulldozer includes frame (or frame), walking device and suspension. The frame is the framework of the whole vehicle, which is used to install all the assemblies and components to make the whole vehicle a whole. The walking device is used to support the body, which transforms the driving torque and rotary motion transmitted by the power device to the driving wheel into the driving force and speed required by vehicle operation and driving. Suspension is a connecting device between the frame and the walking device to transmit force to each other.
Compared with wheel driving system, crawler bulldozer has the following characteristics: first, the bearing area is large and the grounding pressure is small. Therefore, tracked vehicles are suitable for operation in soft or muddy ground, with small subsidence, small rolling resistance and good trafficability. Second, there are shoe teeth on the track bearing surface, which is not easy to slip and has good traction and adhesion performance, which is conducive to play a greater traction force. Third, the structure is complex, the weight is large, the motion inertia is big, the cushioning performance is poor, "four wheels and one belt" wear is serious, the cost is high, and the service life is short. Therefore, the speed of tracked vehicles can not be too high, and the mobility is poor. Fourth, crawler vehicles can also work in high temperature field, and its outstanding advantages of "low specific pressure" and "large traction force" are irreplaceable by wheeled vehicles.
2、 Composition and function of crawler bulldozer walking device
The walking device of crawler bulldozer is composed of walking frame, guide wheel, track tensioning device, carrier roller, support roller, track assembly and driving wheel. The left and right tracks are wrapped outside the above four wheels and are tensioned by the tensioning device and directly contact with the ground. The driving wheel drives the crawler to rotate around four kinds of wheels and does not roll directly on the ground. The guide wheel is to tension the track and guide it to wind correctly. Several rollers roll on the track surface to transfer vertical load to the track. The carrier roller supports the upper half of the track so that it does not sag and reduces its vibration. The four wheels and tensioning devices mentioned above are all assembled on a wheel frame (i.e. trolley frame, also known as crawler frame) except the driving wheel, so as to form a trolley. Each tracked vehicle has a left and a right trolley. The weight of the whole vehicle is transmitted to the lower track through the trolley frame and roller, so that the lower track is pressed tightly on the ground. When the driving wheel is driven by the driving gear (driven gear), the gear teeth pull the track, and the ground immediately produces the reaction force acting on the track, which makes the frame move forward or backward relative to the ground, and the whole vehicle moves with it.
1. Track assembly. The track assembly includes track shoe, chain rail link, track pin and pin sleeve. Each track is connected by dozens of track assemblies. Because it is in direct contact with the ground and bears all the weight and driving force of the body, it should have enough strength, rigidity and wear resistance. The track shoes used in the track assembly are generally equipped with shoe spines, which is to increase the adhesion of the track and prevent it from slipping. There are three types of sole, double and three tendons. Double reinforcement is often used in loaders.
2. Roller. Roller is a kind of component with poor working condition in crawler walking device. Therefore, it is necessary to have reliable sealing device and lubricating device. There are many types of roller structure, the commonly used roller structure is composed of shaft, wheel body, iron sleeve and floating oil seal. The center shoulder type is adopted for the support wheel shaft, and the rest parts are symmetrically arranged on both sides of the shoulder. Although the structure is more complex than that of the straight shaft type, and its processability is poor, it can withstand large axial force and impact load. In particular, the use of floating oil seal and bimetallic sleeve greatly improves the service life and simplifies the workload of maintenance.
3. Guide wheel. The function of the guide wheel is to guide the running direction of the crawler walking device, so as to alleviate the impact of the track moving forward. The guide wheel, like the roller, also adopts the middle shoulder type shaft, bimetallic sleeve and floating oil seal.
4. Carrier wheel. The carrier roller is used to prevent the upper part of the track from sagging and falling off when the track is walking. The carrier roller of loader is generally cantilever mounted on the track frame. The structure of carrier roller is composed of shaft, end cover, floating oil seal, roller body and rolling bearing. The carrier roller is located on the upper part of the track frame, bears less load than the roller, is not easy to be invaded by dirt and has less wear.
5. Driving wheel. The function of the driving wheel is winding the track to make the loader walk. The driving wheel is installed at the rear of the track frame, so the working condition is heavy. There are many types of driving wheel, such as integral type, ring gear insert type and gear block type. In order to make the worn driving wheel exchange as much as possible and save raw materials, the ring gear type is generally suitable. The number of teeth is odd, which can improve the service life.
6. Track tensioning device. For example, when the crawler loader is walking and working, the pitch of each link of the track will be lengthened due to wear, which will reduce the tension, the upper part of the track will sag and increase, the running will jump, and even the track will fall off. Therefore, the crawler tensioning device is required to tension. However, if the track tension is too tight, the pin shaft and the pin sleeve will be worn quickly due to excessive stress. Therefore, it is necessary to adjust a proper tension. The track tensioning device is connected with the guide wheel and moves forward and backward on the guide device of the guide wheel. There are many types of crawler tensioning device, and adjusting screw type and hydraulic type are widely used.
The hydraulic crawler tensioning device is composed of a guide bracket, a guide fork head, a piston and a buffer mechanism. The device is installed on the track frame behind the guide wheel. The grease gun is used to inject grease into the hydraulic cylinder at the oil nozzle. The piston is pushed to move so that the guide wheel is in the