1. Overall structure of single-bucket hydraulic excavator
　　The overall structure of single-bucket hydraulic excavator includes power unit, working device, slewing mechanism, operating mechanism, transmission system, traveling mechanism and auxiliary equipment, etc., as shown in the figure.
　　The commonly used full-slewing is that the power unit of the hydraulic excavator, the main part of the transmission system, the slewing mechanism, auxiliary equipment and the cab, etc. are all installed on a rotatable platform, usually called the upper turntable. Therefore, the single-bucket hydraulic excavator can be summarized into three parts: the working device, the upper turntable and the traveling mechanism.
　　The excavator converts the chemical energy of diesel into mechanical energy through the diesel engine, and the hydraulic plunger pump converts the mechanical energy into hydraulic energy, and distributes the hydraulic energy to each actuator through the hydraulic system (hydraulic cylinder, rotary motor + reducer, travel motor + Reducer), the hydraulic energy is converted into mechanical energy by each actuator, so as to realize the movement of the working device, the rotary movement of the rotary platform, and the walking movement of the whole machine.
　　2. Excavator power system
　　1. Excavator power transmission route as follows
　　1) Walking power transmission route: diesel engine—coupling—hydraulic pump (mechanical energy converted into hydraulic energy)—distribution valve—central rotary joint—walking Motor (hydraulic energy is converted into mechanical energy)—reduction gearbox—drive wheel—rail chain crawler—realize walking
　　2) Rotary motion transmission route: diesel engine—coupling—hydraulic pump (mechanical energy is converted into hydraulic energy)— —distribution valve—swing motor (convert hydraulic energy into mechanical energy)—gearbox—slewing bearing—realize rotation
　　3) Boom movement transmission route: diesel engine—coupling—hydraulic pump (convert mechanical energy )——distribution valve——boom cylinder (convert hydraulic energy into mechanical energy)—realize boom movement
　　4) stick movement transmission route: diesel engine—coupling—hydraulic pump (convert mechanical energy into hydraulic energy)—— Distribution valve—stick cylinder (convert hydraulic energy into mechanical energy)—realize stick movement
　　5) Bucket movement transmission route: diesel engine—coupling—hydraulic pump (convert mechanical energy into hydraulic energy)—distribution valve— ——Bucket cylinder (hydraulic energy is converted into mechanical energy)——to realize bucket movement
　　1. Guide wheel 2, center rotary joint 3, control valve 4, final drive 5, travel motor 6, hydraulic pump 7, engine 8, travel
　　speed solenoid valve 9, swing brake solenoid valve 10, swing motor 11, swing mechanism 12 , Slewing bearing
　　2. Power device
　　The power device of a single-bucket hydraulic excavator mostly adopts an upright multi-cylinder, water-cooled, one-hour power-calibrated diesel engine.
　　3. Transmission system
　　The single-bucket hydraulic excavator transmission system transmits the output power of the diesel engine to the working device, slewing device and walking mechanism. There are many types of hydraulic transmission systems for single-bucket hydraulic excavators, which are traditionally classified according to the number of main pumps, power adjustment methods and the number of circuits. Single-pump or double-pump single-circuit quantitative system, double-pump double-circuit quantitative system, multi-pump multi-circuit quantitative system, double-pump double-circuit divided power adjustable variable system, double-pump double-circuit full power adjustable variable system, multi-pump multi-circuit quantitative Or variable mixing system and other six. According to the oil circulation method, it is divided into open system and closed system. According to the oil supply mode, it is divided into series system and parallel system.
　　1. Drive plate 2, coil spring 3, stop pin 4, friction plate 5, shock absorber assembly 6, muffler
　　7, engine rear mount 8, engine front mount
　　where the flow output by the main pump is a fixed value The hydraulic system of the hydraulic system is a quantitative hydraulic system; on the contrary, the flow rate of the main pump can be changed through the adjustment system, which is called a variable system. In the quantitative system, each actuator works according to the fixed flow supplied by the oil pump under the condition of no overflow, and the power of the oil pump is determined according to the fixed flow and the maximum working pressure; in the variable system, the most common is the double pump double circuit constant power variable The system can be divided into partial power variable and full power variable. The split power variable regulation system is to install a constant power variable pump and constant power regulator on each circuit of the system, and the power of the engine is evenly distributed to each oil pump; the full power regulation system has a constant power regulator to simultaneously control The flow rate of all oil pumps in the system is changed, thus achieving a synchronized variable.
　　The return oil of the actuator in the open system directly flows back to the oil tank, which is characterized by simple system and good heat dissipation effect. However, the capacity of the fuel tank is large, and the low-pressure oil circuit has many chances of contact with air, and the air is easy to infiltrate into the pipeline to cause vibration. The operation of single-bucket hydraulic excavators is mainly the work of the oil cylinder, and the difference between the large and small oil chambers of the oil cylinder is large, the work is frequent, and the heat generation is large. Therefore, most single-bucket hydraulic excavators adopt an open system; The oil return line of the actuator does not directly return to the oil tank. Its characteristic structure is compact, the volume of the oil tank is small, there is a certain pressure in the oil return line, the air is not easy to enter the line, the operation is relatively stable, and the impact when changing direction is avoided. . However, the system is more complicated, and the heat dissipation condition is poor. In the local system such as the slewing device of the single-bucket hydraulic excavator, a closed-loop hydraulic system is used. In order to supplement the oil leakage due to the forward and reverse rotation of the hydraulic motor, a charge pump is often provided in the closed system.
　　4. Slewing mechanism
　　The slewing mechanism makes the working device and the upper turntable turn left or right for excavation and unloading. The slewing device of the single-bucket hydraulic excavator must be able to support the turntable on the frame without tilting and make the slewing light and flexible. For this reason, single-bucket hydraulic excavators are equipped with slewing support devices and slewing transmission devices, which are called slewing devices.
　　1. Brake 2, hydraulic motor 3, planetary gear reducer 4, slewing ring gear 5, lubricating oil cup, 6, central slewing joint The
　　transmission forms of the slewing device of the full-slewing hydraulic excavator include direct drive and indirect drive.
　　1) Direct drive. A drive pinion is installed on the output shaft of the low-speed high-torque hydraulic motor, which meshes with the rotary gear.
　　2) Indirect transmission. It is an indirect transmission structure in which the high-speed hydraulic motor drives the rotary ring gear through the gear reducer. It has a compact structure, a large transmission ratio, and the stress of the gears is better. The structure of the axial piston hydraulic motor is basically the same as that of the same type of hydraulic oil pump, and many parts can be used in common, which is convenient for manufacturing and maintenance, thereby reducing the cost. However, a brake must be installed in order to absorb a large moment of rotary inertia, shorten the cycle time of the excavator, and improve production efficiency.
　　5. Walking mechanism
　　The walking mechanism supports the overall quality of the excavator and completes the walking task, and mostly adopts crawler type and tire type.
　　6. Crawler walking mechanism
　　The basic structure of the crawler-type traveling mechanism of a single-bucket hydraulic excavator is roughly the same as other crawler-type mechanisms, but it uses two hydraulic motors to drive a crawler each. Similar to the transmission of the slewing device, a high-speed low-torque motor or a low-speed high-torque motor can be used. The excavator with two hydraulic motors rotating in the same direction will travel straight; if only one hydraulic motor is supplied with oil and the other hydraulic motor is braked, the excavator will turn around the track on the braking side. Reverse rotation, the excavator will turn in situ.
　　All parts of the walking mechanism are installed on the integral walking frame. The pressure oil input by the hydraulic pump enters the travel hydraulic motor through the multi-way reversing valve and the central rotary joint. walk.
　　Most single-bucket hydraulic excavators use combined structure crawler and flat track - no obvious thorns, although the adhesion performance is poor, but it is durable and less destructive to the road surface. It is suitable for operations on hard rocky ground or frequent transitions. There is also a three-spur type crawler, with a large ground area and a shallow depth of penetration into the soil, which is suitable for excavator quarrying operations. After the implementation of standardization, it is stipulated that the excavator adopts rolled track shoes with light weight, high strength, simple structure and low price. The triangular track shoes specially used in swampy land can reduce the grounding specific pressure and improve the passing ability of the excavator on loose soil.
　　1. Guide wheel 2, track frame 3, carrier sprocket wheel 4, final drive
　　5, support wheel 6, track shoe 7, center guard plate 8, tension spring 9, front guard
　　plate The whole casting is adopted, which can be correctly meshed with the track and the transmission is stable. When the excavator is
　　walking, the driving wheel should be located at the rear, and the tension section of the track is shorter to reduce the friction wear and power loss of the track.
　　Each crawler is equipped with a tensioning device to adjust the tension of the crawler to reduce vibration, noise, friction, wear and power loss. At present, single-bucket hydraulic excavators all adopt hydraulic tensioning structure. Its hydraulic cylinder and buffer spring internally reduce the structural size.
　　7. Wheeled walking mechanism
　　The walking mechanism of the tire excavator consists of two types: mechanical transmission and hydraulic transmission. Among them, the walking mechanism of the hydraulically driven tire excavator is mainly composed of a frame, a front axle, a rear axle, a transmission shaft and a hydraulic motor.
　　The walking hydraulic motor is installed on the fixed and frame gearbox, and the power is transmitted to the front and rear drive axles through the gearbox and the transmission shaft. Some excavators drive the wheels through the wheel reducer. The high-speed transmission mode of the hydraulic motor is reliable in use, and the vertical moving shaft of the upper and lower transmission boxes in the mechanical transmission is omitted, and the structure is simple and convenient to arrange. 　　1. Frame 2, slewing support 3, central slewing joint 4, outrigger 5, rear axle 6, transmission shaft 7, hydraulic motor and 　　gearbox
　　8, front axle There are many types (up to more than 100 types). At present, in engineering construction, backhoes and crushers are most widely used in engineering construction. 　　1. Backhoe structure 　　Articulated backhoe single-bucket hydraulic excavator is the most commonly used structural form. The main components such as the boom, arm and bucket are hinged to each other. Under the action of the hydraulic cylinder, each component swings around the hinge point to complete the excavation. Actions such as lifting and unloading soil. 　　Figure 5-25 Backhoe working device 　　1-stick cylinder; 2-boom; 3-hydraulic pipeline; 4-boom cylinder; 5-bucket; 6-bucket teeth; 7-side teeth 　　; ; 9-rocker; 10-bucket cylinder; 11-stick 　　1.1 Boom 　　The boom is the main part of the backhoe, and its structure is divided into two types: integral type and combined type. 　　1.1.1 Integral Boom










　　The advantages of integral boom are simple structure, light weight and high rigidity. The disadvantage is that there are few working devices to replace, and the versatility is poor, and it is mostly used on excavators with similar long-term operating conditions. The integral boom can be divided into two types: straight boom and curved boom. Among them, the straight arm is simple in structure, light in weight and easy to manufacture. It is mainly used for suspended excavators, but it cannot obtain a large digging depth for general-purpose excavators; the curved arm is currently the most widely used Compared with the straight arm of the same factory, it can make the excavator have a greater digging depth, but the height of unloading soil is reduced, which is in line with the requirements of the backhoe operation of the excavator.
　　1.1.2 Combined boom
　　The combined boom is connected by auxiliary connecting rods (or hydraulic cylinders) or bolts. The angle between the upper and lower booms can be adjusted by auxiliary links or hydraulic cylinders. Although the structure and operation are complicated, the angle between the upper and lower booms can be greatly adjusted at any time during the operation of the excavator, thereby improving the operating performance of the excavator , especially when digging a narrow and deep foundation pit with a backhoe or a grab bucket, it is easy to obtain a vertical excavation trajectory with a large distance, which improves the excavation quality and productivity. The advantage of the combined boom is that the working size and digging capacity of the excavator can be adjusted freely according to the working conditions, and the adjustment time is short. In addition, it has many interchangeable working devices, which can meet the needs of various operations, and is convenient for loading and transportation. Its disadvantages are high quality and high manufacturing cost, and it is used on small and medium excavators.
　　Combined boom
　　(a) bottom connecting rod (b) connecting rod top
　　1, lower boom 2, upper boom 3, connecting rod or hydraulic cylinder
　　2, bucket
　　1.2.1 Basic requirements
　　1) The longitudinal direction of the bucket The profile should adapt to the law of movement of various materials in the bucket during the excavation process, which is conducive to the flow of materials, minimizes the resistance of soil loading, and is conducive to filling the bucket.
　　2) Bucket teeth are installed to increase the linear pressure ratio of the bucket to the excavated materials. The bucket teeth and bucket shape parameters have a small unit cutting resistance, which is convenient for cutting and breaking the soil. Bucket teeth should be wear-resistant and easy to replace.
　　3) The material in the non-loading bucket is not easy to fall out, and the ratio of bucket width to diameter should be greater than 4:1.
　　4) The material is easy to unload, shortening the unloading time, and improving the volumetric efficiency of the bucket.
　　1.2.2 Structure The shape and size of the bucket used in the backhoe have a lot to do with its operating objects. In order to meet the needs of various excavator operations, various forms of buckets can be configured on the same excavator. Figure 2-3 and Figure 2-4 respectively show the basic form of the reverse bucket and the teeth of the commonly used bucket. It adopts assembly type, and its forms include rubber bayonet type and screw connection type.
　　The structural form of the connection between the bucket and the hydraulic cylinder includes a four-bar linkage and a six-bar linkage. Among them, the connection mode of the four-bar linkage mechanism is that the bucket is directly connected to the hydraulic cylinder, so that the bucket rotation angle is small and the working torque changes greatly; the characteristic of the six-bar linkage mechanism is that under the condition of the same piston stroke of the hydraulic cylinder, the bucket can After the larger corner, and improve the transmission characteristics of the mechanism.
　　Slewing device of the excavator
　　1. Slewing device
　　The upper turntable is one of the three major components of the hydraulic excavator. In addition to the engine, hydraulic system, driver's cab, balance weight, fuel tank, etc. on the turntable, there is also a very important part - the slewing device. The slewing device of the hydraulic excavator is composed of a turntable, a slewing support and a slewing mechanism. As shown in Figure 3-1, the outer race of the slewing device is connected to the turntable with bolts, and the inner race with teeth is connected to the chassis with bolts. There are rolling elements between them. The vertical load, horizontal load, and overturning moment of the excavator working device acting on the turntable are transmitted to the chassis through the outer race, rolling body and inner seat of the slewing support. The casing of the slewing mechanism is fixed on the turntable, and the pinion gear meshes with the ring gear on the inner race of the slewing support. The pinion can rotate around its own axis and revolve around the center line of the turntable. When the slewing mechanism works, it is like a pair of The chassis rotates.
　　The slewing device of the hydraulic excavator must be able to support the turntable on the fixed part (get off the car). It cannot be tipped over, and the rotation should be light and flexible. For this reason, hydraulic excavators are equipped with a slewing bearing device (supporting function) and a slewing transmission device (driving the turntable to rotate), and are collectively referred to as the slewing device of the hydraulic excavator. Second, the main structural form of the slewing bearing
　　1
　　. Rotary column type slewing bearing
　　The rotary column type bearing driven by the swing hydraulic motor is shown in Figure 3-2.
　　It consists of upper and lower support shafts 4 and 6 fixed on the revolving body 1, and upper and lower shaft seats 3 and 7. The bearing seat is fixed on the frame 5 with bolts. The rotating body and the supporting shaft form a rotating column, which is inserted into the bearing of the bearing housing. The output shaft of the swing hydraulic cylinder whose shell is fixed on the frame 5 is inserted into the lower support shaft 6 to drive the rotary body to rotate relative to the frame. The revolving body is often made into a "匚" shape to avoid collision with the revolving mechanism. The working device is hinged on the revolving body and rotates together with the revolving body.
　　2. Rolling bearing type slewing ring
　　The rolling bearing type slewing ring is actually a large diameter rolling bearing. The biggest difference between it and ordinary bearings is that its speed is very slow. The slewing speed of the excavator is between 5~11r/min. In addition, the center diameter and height ratio of the general bearing raceway is 4~5, while that of the slewing bearing is 10~15. Therefore, the rigidity of this kind of bearing is poor, and the work must be guaranteed by the supporting connection structure.
　　The typical structure of the rolling bearing slewing ring is shown in Figure 3-3. The inner race or the outer race can be processed into an inner gear ring or an outer gear ring. The seat ring with the ring gear is a fixed ring, which is fixed on the base with bolts 4 and 5 distributed along the circumference. The seat ring without teeth is a slewing ring, which is connected with the turntable of the excavator by bolts. When assembling, the seat rings 1, 3 and rolling elements 8 can be installed first to form a complete part, and then assembled with the excavator. In order to ensure flexible rotation and prevent jamming after thermal expansion, the slewing bearing should have a certain axial clearance. This clearance varies due to machining errors and wear of raceways and rolling elements. Therefore, an adjusting gasket 2 is provided between the two seat rings, and the gap can be adjusted during assembly and repair. The spacer 7 is used to prevent the extrusion between adjacent rolling bodies 8, reduce the wear of the rolling bodies, and play a guiding role. The rolling elements can be balls or rollers.
　　The rolling bearing type slewing support mechanism is widely used in full-slewing hydraulic excavators. It is developed on the basis of ordinary rolling bearings, and its structure is equivalent to enlarged rolling bearings. Compared with traditional rolling bearings, it has a series of advantages such as small size, compact structure, large carrying capacity, small rotational friction resistance, small gap between rolling elements and rails, convenient maintenance, long service life, and easy realization of three modernizations. Compared with ordinary rolling bearings, it has its own characteristics: the rigidity between the inner and outer races of ordinary rolling bearings is guaranteed by the assembly between the shaft and the bearing seat, while it is guaranteed by the turntable and the chassis; the slewing support The rotational speed is low and the axial load is usually carried, so the number of cycles of the contact point on the track is low.
　　Section 4 Arrangement of Excavator Turntable
　　1. Turntable Structure
　　The main load-bearing part of the turntable is a phase-shaped frame structure main beam 3 with high torsional and bending rigidity welded by steel plates, and the boom and its hydraulic cylinder are supported on the main beam. on the lug 1. The boom support of large excavators mostly uses double lugs, while small excavators mostly use single lugs. There are liners and support rings under the main girder, which are connected with the slewing ring, and small frames are welded on the left and right sides as additional load-bearing parts.
　　The support of the turntable should have sufficient rigidity to ensure the normal operation of the slewing support. as the picture shows.
　　(a) double-lug type (b) single-lug type
　　1, lug 2, support ring 3, longitudinal beam
　　2. Arrangement of the turntable
　　When the hydraulic excavator is working, the self-weight and load of the upper part of the turntable and the position of the resultant force are also constantly changing, and In terms of deflection load, in order to balance the load moment, each device on the turntable needs to be reasonably arranged and a counterweight is installed at the tail to improve the force bearing of the lower structure of the turntable, reduce the wear of the slewing support, and ensure the stability of the whole machine.
　　Figure 3-16 shows the layout of the turntable of the domestic WY160 full hydraulic excavator, the engine 1 is arranged horizontally at the tail of the turntable Figure 3-17 shows the layout of the turntable of the Nissan HC-300 semi-hydraulic excavator, the engine 1 is arranged longitudinally on the turntable Tail.
　　The layout principle of the hydraulic excavator is left and right symmetry, try to achieve a balanced quality, and the heavier assembly and parts are close to the tail of the turntable. In addition, the coordination of the work of each device and the convenience of maintenance should also be considered. Sometimes the layout of the turntable is limited by the size of the structure, and the center of gravity deviates from the axis, resulting in unequal grounding pressure of the left and right crawlers, which affects the structural strength of the walking frame and the driving performance of the excavator. At this time, it can be solved by adjusting the center of gravity of the counterweight, as shown in Figure 3-18 As shown in the figure, x and x' in the figure are respectively the axis values ​​of the center of gravity of the turntable and the center of the counterweight.
　　The layout principle for determining the position of the counterweight is to make the eccentricity e of the resultant force FR on the upper part of the turntable when the excavator is heavy-loaded and operating in a large range, roughly equal to the eccentricity e' of the resultant force FR' when the excavator is under no-load and small-range operation, as shown in Figure 3- 19.
　　When the excavator is running, the driving wheel generates a pulling force on the tight side of the track - the driving section and the ground section, trying to pull the track out from under the rollers, because there is sufficient adhesion between the track under the rollers and the ground. Stop the track from pulling out. The driving wheel is forced to roll the track, and the guide wheel is laying the track on the ground, so that the excavator moves forward along the track track with the help of the rollers.
　　The crawler belt traveling device with hydraulic transmission, when the excavator turns, there are two traveling motors installed on the crawler belt and supplied by two hydraulic pumps. Through the control of the oil circuit, it is very convenient to realize the steering and turning on the spot, so as to adapt to the excavator's various driving conditions. Kind of sports on the ground and on the field. The picture shows the turning situation of the hydraulic excavator. Picture (a) shows that the two travel motors rotate in opposite directions, and the excavator turns on the spot. Figure (b) shows that the hydraulic pump only supplies oil to one travel motor, and the excavator turns around one side of the track.
　　Figure (a) Steering on the spot (b) Steering around one side of the track
　　1.2 Structure
　　1.2.1 Walking structure
　　The walking frame is the load-bearing skeleton of the crawler-type walking device. The steel plate is welded into the connecting turntable of the underframe, which bears the upper load of the excavator and transmits it to the crawler frame through measurement.
　　Walking can be divided into combined type and integral type according to the structural form. The base frame of the combined walking frame is a frame structure, and the beam is I-beam or welded box beam, which is inserted into the hole of the track frame. The track frame usually adopts a "∏"-shaped section with the lower part open, and the two ends are forked to install the driving wheel. , guide wheels and rollers.
　　The advantage of the combined walking frame is when it is necessary to change the stability of the excavator and reduce the ground specific pressure. Widened beams and extended track frames can be installed without changing the structure of the underframe, so that tracks of different lengths and widths can be installed. His disadvantages are that the section of the track frame is weakened more, the rigidity is poor, and cracks are easy to occur at the weakened section.
　　In order to overcome the above shortcomings, more and more hydraulic excavators adopt integral walking frames, which have simple structure, light weight, high rigidity and low manufacturing cost. The diameter of the supporting rollers is small, and within the length of the walking device, 5 to 9 supporting rollers can be installed on each side, so that the upper part of the excavator can be evenly transmitted to the ground, which is convenient for use on the ground with low bearing capacity and improves walking. performance.
　　1.2.2 Four-wheel belt
　　The four-wheel belt consisting of track, wheel drive wheel, guide wheel, supporting wheel, and supporting wheel is directly related to the working performance and walking performance of the excavator, and its quality and manufacturing cost account for about 30% of the whole machine. a quarter.
　　1) Tracks. There are two types of crawlers for excavators: integral and combined.
　　The integral crawler track has meshing teeth on the track plate, which directly meshes with the driving wheel. The track shoe itself becomes the rolling track of the rollers and other wheels.
　　Combined crawler tracks are widely used on hydraulic excavators at present. It consists of track shoes, chain rail joints, track pins and pin sleeves. The left and right chain rails are tightly connected with the pin sleeves. There is a certain gap between the crawler pin shaft inserted into the pin sleeves, so as to rotate flexibly, and its two ends are matched with the other two rail joint holes. The locking track pin is in dynamic fit with the link hole of the chain rail, which facilitates the disassembly and assembly of the entire track. The combined track has a small pitch and good rotation, which makes the excavator travel faster, with higher pin shaft and hardness, wear resistance and long service life.
　　2) Track rollers. The rollers transmit the weight of the excavator to the ground. When the excavator is running on different grounds, the rollers often bear the impact of the ground, so the loads on the rollers are relatively large. In addition, the working conditions of the middle wheel are also relatively harsh, often in dust, and sometimes soaked in muddy water, so good sealing is required. Rollers are usually cast from 35Mn or 50Mn steel, and the quenching hardness of the wheel surface is HRC48-57 to obtain good wear resistance. . The supporting wheels are mostly supported by sliding bearings, and are dust-proof with floating oil seals.
　　The structure of the rollers is fixed on the track frame through the shafts at both ends as shown in the figure above. The wheel edge flange of the supporting wheel supports the function of the track to prevent the track from falling off laterally when walking. In order to arrange more rollers in a limited length, some of the rollers are often made without outer flanges, and the rollers with or without outer flanges are arranged alternately.
　　The lubricating grease for lubricating sliding bearings and oil seals is added from the screw plug hole in the middle of the roller body, usually only once during an overhaul period, which simplifies the usual maintenance work of the excavator.
　　The supporting wheel is basically the same as the supporting wheel.
　　3) Guide wheels. The guide wheel is used to guide the track to rotate correctly and prevent it from deviation and off-track. The guide wheels of most hydraulic excavators also function as supporting wheels, which can increase the contact area of ​​the track to the ground and reduce the grounding specific pressure. The wheel surface of the guide wheel is made smooth, and there is a shoulder ring in the middle as a guide, and the ring surfaces on both sides support the rail chain. The smaller the distance between the guide wheel and the nearest track roller, the better the guidance. 　　The guide wheels are usually cast
　　and quenched and tempered with 40, 45 steel or 35Mn steel, and the hardness is HB230~270 　　. Increase the pitch and elongate the entire track, resulting in friction of the track frame, derailment of the track, loud noise of the traveling device, etc., thus affecting the walking performance of the excavator. Therefore, each track must be equipped with a tensioning device to keep the track at a certain degree of tension. 　　Oil cylinder 3 and support 1 and shaft 2 of the guide wheel frame are connected together with bolts to push the guide wheel to expand and contract. Piston 4 is installed in the oil cylinder, and oil seal 15 seals the butter in the piston and cylinder cavity. When injecting pressure butter, then push piston to move to the right, piston pushes push rod 18, and push rod pushes spring front seat 6 again, and spring front seat then compresses spring 7 and 8, like this, just formed a The elastic body buffers the impact force applied by the track, eliminates the impact load, reduces the impact stress, and improves the service life. The screw plug 17 is used for putting butter. When the track tension is too large, slowly rotate the screw plug 17 to make the Squeeze out the butter slowly, do not unscrew too much at once, so as not to shoot out the butter and hurt people. When the pressure of injecting butter from the oil nozzle is too high, the movable bulldozer can be used as an auxiliary means to make the butter easy to inject.