A chassis structure of a pure electric tractor and a tractor

Abstract

The present invention relates to the technical field of tractor chassis, and specifically to a pure electric tractor chassis structure and a tractor, including a frame and cross beams. It further includes a horizontal adjustment component, a vertical adjustment component, a battery pack, a push switch, and a reinforcement plate. The horizontal adjustment component is installed between two cross beams, the vertical adjustment component is connected to the horizontal adjustment component, the battery pack is installed between the inner side of the vertical adjustment component and the surface of the cross beam, the reinforcement plate is installed between two cross beams, and the push switch is installed on one side of the reinforcement plate close to the battery pack. When the horizontal adjustment component drives the vertical adjustment component to move horizontally. The present invention solves the problems of insufficient friction and steering failure and insufficient driving caused by the center of gravity of the existing tractor being biased backward when the towing carriage climbs slopes and turns by lowering the center of gravity and moving the center of gravity forward when climbing steep slopes to ensure the grip of the front wheels of the tractor.

Description

Technical Field

[0001] The present invention relates to the technical field of tractor chassis, and specifically to a pure electric tractor chassis structure and a tractor. Background Art

[0002] A tractor is a commercial vehicle specifically used for towing trailers, mainly for transporting goods. It forms a complete transportation unit by connecting with a semi-trailer or a full trailer. Tractors are widely used in fields such as logistics transportation and long-distance freight transportation, and are an essential and important tool in modern road transportation. With the development of new energy technologies, pure electric tractors have gradually been put into market use. Due to the limited electrical energy that can be stored, pure electric tractors have limitations in terms of driving range. When traveling a certain distance, pure electric tractors need to be charged. Therefore, pure electric tractors are mainly suitable for short-distance transportation and the enclosed areas of logistics workshops.

[0003] In regions such as Yunnan, Guizhou, and Sichuan in China, when a pure electric tractor is towing a cargo compartment loaded with foam boxes for short-distance transportation, the electric motor providing power input can quickly output high torque at low speeds, ensuring the performance of the electric tractor during starting, acceleration, and climbing slopes. To ensure the stability of the pure electric tractor and the compartment during normal driving and prevent the tractor from tipping forward during braking while driving, the center of gravity of the tractor is usually set at the middle position of the tractor. However, when a pure electric tractor is climbing some steep slopes with relatively large gradients, due to the increase in the longitudinal inclination angle of the tractor and the compartment, the center of gravity will move backward along the longitudinal axis of the tractor and the compartment. The backward movement of the center of gravity will cause a reduction in the vertical load on the front wheels, thereby reducing the grip of the front wheels, and further affecting the traction and stability of the tractor, resulting in the tractor being unable to pull the trailer to complete the uphill operation. Moreover, at the turning points of the slope, the front wheels are prone to lose their guiding function due to lifting, and safety accidents are extremely likely to occur.

[0004] Therefore, a pure electric tractor chassis structure and a tractor are proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a pure electric tractor chassis structure and a tractor. By reducing the center of gravity and moving the center of gravity forward when climbing a steep slope to ensure the grip of the front wheels of the tractor, the problems of insufficient friction and steering failure and insufficient driving caused by the center of gravity shifting backward during climbing and turning of the existing tractor towing a compartment are solved. It has the effect of being able to flexibly adjust the overall center of gravity and ensuring the turning effect and climbing ability of the tractor and the compartment.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A chassis structure of a pure electric tractor, including a frame and cross beams, further comprising a horizontal adjustment assembly, a vertical adjustment assembly, a battery pack, a push switch and a reinforcement plate. The horizontal adjustment assembly is installed between two cross beams. The vertical adjustment assembly is connected to the horizontal adjustment assembly. The battery pack is installed between the inner side of the vertical adjustment assembly and the surface of the cross beam. The reinforcement plate is installed between two cross beams. The push switch is installed on one side of the reinforcement plate close to the battery pack. When the horizontal adjustment assembly drives the vertical adjustment assembly to move horizontally, when the battery pack moves to the limit position along with the vertical adjustment assembly, it presses the push switch. At the same time, the push switch disconnects the power supply of the horizontal adjustment assembly and starts the vertical adjustment assembly. The vertical adjustment assembly changes the height of the battery pack in the vertical direction.

[0008] When climbing a slope, since the center of gravity of the tractor and the carriage is located at a relatively far position behind the front of the vehicle head, at this time, the friction force between the front wheels and the ground is small, and the driving wheels cannot have sufficient friction force due to insufficient pressure. As a result, the front wheels will simultaneously experience steering failure and the driving wheels will slip. In this case, by moving the battery pack forward and lowering its height through the horizontal adjustment assembly and the vertical adjustment assembly, the center of gravity of the tractor and the carriage is moved forward and the center of gravity height is reduced, thereby ensuring the friction force between the front wheels and the driving wheels and the ground. Furthermore, when towing a carriage with a relatively small towing mass, the climbing effect and turning effect of the tractor are ensured.

[0009] Preferably, a limiting groove is formed on the surface of the cross beam, and the axis of the limiting groove is parallel to the axis of the cross beam.

[0010] Preferably, the horizontal adjustment assembly includes a horizontal frame, a lead screw, a slider and a driving motor. Two horizontal frames are respectively fitted and installed on the inner walls of two cross beams. Two lead screws are respectively rotatably connected to the two horizontal frames, and one end of the lead screw extends to the outside of the horizontal frame. The slider is slidably arranged between the inner walls of the horizontal frame, and the slider is threadedly connected to the lead screw. The driving motor is installed on one side of the reinforcement plate away from the battery pack, and the output shaft of the driving motor is respectively connected to the ends of the two lead screws through belt pulleys and belts. A clamping groove is formed on the side wall of the slider.

[0011] Preferably, the vertical adjustment assembly includes a fixed frame, a lifting rod and an electric rod. The fixed frame is installed between a plurality of clamping grooves. Notches are formed on both sides of the inner wall of the fixed frame. The side wall of the lifting rod is slidably fitted with the notches. The electric rod is installed between the side wall of the lifting rod and the surface of the fixed frame.

[0012] Preferably, the battery pack includes a main battery and a secondary battery. The main battery is installed on the surface of the fixed frame. The secondary battery is slidably fitted on the surface of the cross beam. U-shaped bars are installed at both ends of the main battery. Insert bars adapted to the U-shaped bars are installed on both sides of the secondary battery. When the main battery descends, the U-shaped bars are separated from the insert bars.

[0013] Preferably, a limiting block is installed at the bottom of the secondary battery, and the limiting block is slidably fitted in the limiting groove.

[0014] Preferably, the number of the vertical adjustment components is set to be multiple groups, and the number of the vertical adjustment components is the same as the number of the battery packs.

[0015] A tractor includes a pure electric tractor chassis structure, and also includes an inclination sensor, tires and a cab. The inclination sensor is installed at the bottom of one side cross beam. The tires are distributed in a rectangular array and are installed and connected to the vehicle frame. The cab is installed on the surface of the cross beam.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] 1. When the present invention performs a short-distance operation by towing a carriage loaded with foam boxes and needs to climb a ramp with a certain slope and a turn, the position and height of the battery pack with a relatively large weight ratio can be adjusted in time, thereby greatly adjusting the center of gravity position and center of gravity height of the tractor and the carriage, providing sufficient friction for the front wheels and driving wheels, and thus ensuring that the tractor climbs the slope smoothly and safely.

[0018] 2. Through the provided horizontal adjustment component and the pressing switch, when the horizontal adjustment component moves the battery pack to a position close enough to the cab, the battery pack presses the pressing switch, thereby switching the working states of the horizontal adjustment component and the vertical adjustment component, and the center of gravity of the tractor and the carriage can be quickly adjusted and changed. The operation is relatively simple, and the effect of one-step adjustment can be achieved.

[0019] 3. Through the provided cross beam and battery pack, during the movement of the battery pack along with the horizontal adjustment component, the main battery and the secondary battery move horizontally at the same time. However, when the vertical adjustment component works, the main battery moves down along with the fixing frame, while the secondary battery is limited on the cross beam. Therefore, when the width of the tractor chassis is limited, the center of gravity of the tractor and the carriage can be changed to the greatest extent as much as possible, thereby ensuring the turning effect and driving effect when the tractor climbs the slope. Description of the Drawings

[0020] Figure 1 is the overall structure schematic diagram of the present invention;

[0021] Figure 2 is the structure schematic diagram of the cross beam and the reinforcing plate of the present invention;

[0022] Figure 3 is the structure schematic diagram of the vertical adjustment component of the present invention;

[0023] Figure 4 is the structure schematic diagram of the horizontal adjustment component of the present invention;

[0024] Figure 5Schematic structural diagram of the battery pack of the present invention;

[0025] Figure 6 Explosion diagram of the battery pack of the present invention;

[0026] Figure 7 Schematic structural diagram of the vertical adjustment assembly and the main battery of the present invention;

[0027] Figure 8 Schematic structural diagram of the slider of the present invention.

[0028] In the figure: 1, vehicle frame; 2, cross beam; 21, limit groove; 3, horizontal adjustment assembly; 31, horizontal frame; 32, lead screw; 33, slider; 331, card slot; 34, drive motor; 4, vertical adjustment assembly; 41, fixing frame; 42, lifting rod; 43, electric rod; 5, battery pack; 51, main battery; 511, U-shaped strip; 52, secondary battery; 521, limit block; 522, insertion strip; 6, push switch; 7, reinforcement plate; 8, tilt sensor; 9, tire; 10, vehicle head. Specific embodiments

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] Please refer to Figures 1 to 8 , the present invention provides a pure electric tractor chassis structure and a tractor, and the technical solutions are as follows:

[0031] Refer to Figure 1 and Figure 2, A chassis structure of a pure electric tractor, including a frame 1 and cross beams 2. Two cross beams 2 are installed in parallel on the top of the frame 1. The area between the cross beams 2 can be used as a space for center of gravity adjustment. It also includes a horizontal adjustment component 3, a vertical adjustment component 4, a battery pack 5, a push switch 6 and a reinforcement plate 7. The horizontal adjustment component 3 is installed between the two cross beams 2. The vertical adjustment component 4 is connected to the horizontal adjustment component 3. The horizontal adjustment component 3 and the vertical adjustment component can also play a certain reinforcement effect between the two cross beams 2, thereby improving the stability of the cross beam 2. The battery pack 5 is installed between the inner side of the vertical adjustment component 4 and the surface of the cross beam 2. When the center of gravity position needs to be adjusted, the horizontal adjustment component 3 first drives the vertical adjustment component to move horizontally, thereby changing the horizontal position of the battery pack 5. Subsequently, the vertical adjustment component changes the height of some components in the battery pack 5, thereby changing the center of gravity height of the tractor. The reinforcement plate 7 is installed between the two cross beams 2. The reinforcement plate 7 plays a role of limiting and reinforcement. The push switch 6 is installed on one side of the reinforcement plate 7 close to the battery pack 5. When the horizontal adjustment component 3 drives the battery pack 5 to move to the horizontal limit position through the vertical adjustment component 4, the side wall of the battery pack 5 contacts the push switch 6 and exerts pressure on the push switch 6. When the horizontal adjustment component 3 drives the vertical adjustment component 4 to move horizontally, when the battery pack 5 moves to the limit position with the vertical adjustment component 4, it exerts pressure on the push switch 6. The position where the battery pack 5 closest to the reinforcement plate 7 cannot move further towards the reinforcement plate 7 side is the limit position. At the same time, the push switch 6 disconnects the power supply of the horizontal adjustment component 3 and starts the vertical adjustment component 4. The vertical adjustment component 4 changes the height of the battery pack 5 in the vertical direction. Under normal circumstances, it is necessary to ensure that the battery pack 5 is located above the cross beam 2 to avoid the battery pack 5 being bumped when passing through rough roads. Considering the limitation of the cruising range, under the condition of permission, as many battery packs 5 as possible need to be installed. This can not only effectively improve the cruising range of the pure electric tractor, but also increase the weight ratio of the battery pack 5 in the tractor. Subsequently, by changing the position of the battery pack 5, it has a better effect on adjusting the center of gravity of the tractor.

[0032] Referring to Figure 3 , As an implementation manner of the present invention, specifically, a limiting groove 21 is formed on the surface of the cross beam 2, and the axis of the limiting groove 21 is parallel to the axis of the cross beam 2. When the battery pack 5 moves horizontally, the contacting part between the battery pack 5 and the cross beam 2 can move horizontally along the limiting groove 21.

[0033] Referring to Figure 4 and Figure 7, as an embodiment of the present invention, specifically, the horizontal adjustment component 3 includes a horizontal frame 31, a lead screw 32, a slider 33, and a driving motor 34. The two horizontal frames 31 are respectively fitted and installed on the inner walls of the two cross beams 2. The two horizontal frames 31 are respectively fitted on the adjacent sides of the two cross beams 2. The two lead screws 32 are respectively rotatably connected to the two horizontal frames 31, and one end of the lead screw 32 extends to the outside of the horizontal frame 31. The external threads of the two lead screws 32 have the same helix direction. The slider 33 is slidably arranged between the inner walls of the horizontal frame 31, and the slider 33 is threadedly connected to the lead screw 32. The driving motor 34 is installed on the side of the reinforcing plate 7 away from the battery pack 5, and the output shaft of the driving motor 34 is respectively connected to the ends of the two lead screws 32 through pulleys and belts. Pulleys are installed on the ends of the lead screws 32 and the output shaft of the driving motor 34, and the pulley on the end of the output shaft of the driving motor 34 is connected to the pulley on the end of the lead screw 32 through a belt. The driving motor 34 drives the two lead screws 32 to rotate simultaneously. Since the helix directions of the external threads on the outer circumferences of the two lead screws 32 are the same, when the driving motor 34 is started, the two lead screws 32 rotate in the same direction, so that the sliders 33 on the two lead screws 32 move in the same direction. A card slot 331 is formed on the side wall of the slider 33. The design of the card slot 331 facilitates the installation and connection of the vertical adjustment component 4 and the slider 33.

[0034] Referring to Figure 3 , as an embodiment of the present invention, specifically, the vertical adjustment component 4 includes a fixed frame 41, a lifting rod 42, and an electric rod 43. The fixed frame 41 is installed between multiple card slots 331, and the fixed frame 41 and the slider 33 are reinforced through appropriate fasteners. Notches are formed on both sides of the inner wall of the fixed frame 41. The top view cross section of the formed notch is U-shaped. The side wall of the lifting rod 42 is slidably fitted with the notch. The lifting rod 42 has a large contact area with the fixed frame 41 through the notch, which can effectively improve the stability of the lifting rod 42 when it undergoes vertical displacement. The top view cross section of the lifting rod 42 is H-shaped. The electric rod 43 is installed between the side wall of the lifting rod 42 and the surface of the fixed frame 41. When the electric rod 43 contracts, the lifting rod 42 moves downward along the notch, thereby reducing the height of the main battery 51. When the electric rod 43 extends, the lifting rod 42 moves upward along the notch, and then the main battery 51 is restored to the initial height, thereby ensuring that the main battery 51 has a certain ground clearance during the driving process of the tractor and ensuring the passing performance of the tractor.

[0035] Referring to Figure 5 and Figure 6, as an implementation manner of the present invention, specifically, the battery pack 5 includes a main battery 51 and a secondary battery 52. The main battery 51 is installed on the surface of the fixing frame 41, and the secondary battery 52 is slidably attached to the surface of the cross beam 2. U-shaped bars 511 are installed at both ends of the main battery 51, and insertion bars 522 adapted to the U-shaped bars 511 are installed on both sides of the secondary battery 52. When the main battery 51 descends, the U-shaped bars 511 are separated from the insertion bars 522. With the design of the insertion bars 522 and the U-shaped bars 511, when the main battery 51 and the secondary battery 52 are at the same height, the main battery 51 and the secondary battery 52 can form an integrated structure, and thus synchronous horizontal movement can be realized. When the height of the main battery 51 decreases, the main battery 51 is automatically separated from the secondary battery 52. The main battery 51 and the secondary battery 52 are connected to the circuit control board through independent wires. And because there is a certain displacement of both the main battery 51 and the secondary battery 52, to prevent the wires from being worn due to falling on the ground after the displacement of the main battery 51 and the secondary battery 52, wire winders are provided for the wires connecting the main battery 51 and the secondary battery 52 to the circuit control board. When the wires are loose, the extra-length wires are timely wound up to prevent the wires from falling on the ground.

[0036] Referring to Figure 6 , as an implementation manner of the present invention, specifically, a limiting block 521 is installed at the bottom of the secondary battery 52, and the limiting block 521 is slidably attached to the limiting groove 21. When the secondary battery 52 moves horizontally, through the cooperation of the limiting groove 21 and the limiting block 521, not only can the horizontal movement of the secondary battery 52 be ensured, but also when the secondary battery 52 is separated from the main battery 51 subsequently, the secondary battery 52 can be prevented from falling off the surface of the cross beam 2. The limiting block 521 is connected to the secondary battery 52 through a spring. When the limiting block 521 moves to the edge of the limiting groove 21, the depth of the edge of the limiting groove 21 is greater, and under the action of the spring, the limiting block 521 is inserted into the edge of the limiting groove 21. At this time, the secondary battery 52 can be prevented from sliding randomly along the surface of the cross beam 2. And the bottom of the limiting block 521 is designed in a V shape. Subsequently, when the main battery 51 moves horizontally, the main battery 51 drives the limiting block 521 at the bottom of the secondary battery 52 to withdraw from the edge of the limiting groove 21.

[0037] Referring to Figure 1 , as an implementation manner of the present invention, specifically, the number of the vertical adjustment assemblies 4 is set to multiple groups, and the number of the vertical adjustment assemblies 4 is the same as the number of the battery packs 5. In the design, other components of the tractor are designed with lightweight, and by correspondingly adjusting the number of the battery packs 5, the effect of adjusting the center of gravity of the battery pack 5 is enhanced. And because the foam boxes loaded on the carriage have a small density and there are large gaps inside, the total weight of the carriage is close to the total weight of the tractor. In this case, when the position of the battery pack 5, which accounts for a certain ratio of the total weight of the tractor, changes, it can play a better role in adjusting the center of gravity of the tractor and the carriage.

[0038] Referring to Figure 1, A tractor, including a pure electric tractor chassis structure, further including an inclination sensor 8, tires 9 and a cab 10. The inclination sensor 8 is installed at the bottom of one side beam 2. The tires 9 are distributed in a rectangular array and are installed and connected to the vehicle frame 1. The cab 10 is installed on the surface of the beam 2. The inclination sensor 8 is connected to the vehicle control system. Through the feedback of the slope value, the horizontal adjustment component 3 is correspondingly activated by the control system after calculation and analysis to adjust the battery pack 5 to a suitable position.

[0039] Working principle: When the tractor towing the carriage loaded with foam boxes needs to climb a turning ramp, the inclination sensor 8 feeds back the slope value of the ramp to the control system of the tractor. Subsequently, the control system calculates the optimal center of gravity position, turns on the power supply of the horizontal adjustment component 3 through the corresponding circuit system, and then moves the vertical adjustment component 4 and the battery pack 5 to a suitable horizontal position to ensure a reasonable center of gravity distribution of the tractor and the carriage, thereby ensuring the turning effect and climbing effect of the tractor.

[0040] Specifically, the output shaft of the drive motor 34 drives two lead screws 32 with the same external thread rotation direction through a pulley and a belt. A plurality of sliders 33 all move in the same direction along the inner wall of the horizontal frame 31, thereby driving the fixed frame 41, the lifting rod 42, and the electric rod 43 to move together toward the cab 10 side. During this process, the horizontal positions of the main battery 51 and the secondary battery 52 are jointly changed until the center of gravity of the tractor and the carriage is adjusted to a suitable position, and then the climbing operation can be carried out.

[0041] When it is necessary to adjust the center of gravity of the tractor and the carriage to the extreme position, the main battery 51 moves together with the slider 33 toward the reinforcement plate 7 side until the main battery 51 presses on the pressure switch 6. Subsequently, the power supply of the electric rod 43 is turned on, and the electric rod 43 contracts to reduce the height of the lifting rod 42 and the main battery 51. The U-shaped strips 511 at both ends of the main battery 51 are separated from the insertion strips 522 and then freely descend, further reducing the center of gravity of the tractor and the carriage.

[0042] After the climbing operation is completed, the control system of the tractor first moves the battery pack 5 upward to reset, the insertion strips 522 are inserted into the U-shaped strips 511, and then controls the drive motor 34 to reverse to restore the main battery 51 and the secondary battery 52 to the initial position to ensure the stability of the tractor during high-speed travel.

[0043] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A pure electric tractor chassis structure, comprising a frame (1) and a crossbeam (2), characterized in that: The invention also comprises a horizontal adjustment component (3), a vertical adjustment component (4), a battery pack (5), a push switch (6) and a reinforcement plate (7), wherein the horizontal adjustment component (3) is installed between the two cross beams (2), the vertical adjustment component (4) is connected to the horizontal adjustment component (3), the battery pack (5) is installed between the inner side of the vertical adjustment component (4) and the surface of the cross beam (2), the reinforcement plate (7) is installed between the two cross beams (2), and the push switch (6) is installed on a side of the reinforcement plate (7) close to the battery pack (5). When the horizontal adjustment component (3) drives the vertical adjustment component (4) to move horizontally, the battery pack (5) applies pressure to the push switch (6) when it moves to the extreme position along with the vertical adjustment component (4), and at the same time, the push switch (6) disconnects the power supply of the horizontal adjustment component (3) and starts the vertical adjustment component (4), and the vertical adjustment component (4) changes the height of the battery pack (5) in the vertical direction; The battery pack (5) comprises a main battery (51) and a secondary battery (52); the main battery (51) is mounted on the surface of a fixing frame (41); the secondary battery (52) is slidably fitted on the surface of a crossbeam (2); both ends of the main battery (51) are mounted with U-shaped bars (511); both sides of the secondary battery (52) are mounted with inserting bars (522) adapted to the U-shaped bars (511); when the main battery (51) is lowered, the U-shaped bars (511) are separated from the inserting bars (522); a limiting block (521) is mounted on the bottom of the secondary battery (52); and the limiting block (521) is slidably fitted in a limiting groove (21).

2. A pure electric tractor chassis structure according to claim 1, characterized in that: A limiting groove (21) is provided on the surface of the cross beam (2), and the axis of the limiting groove (21) is arranged parallel to the axis of the cross beam (2).

3. The pure electric tractor chassis structure according to claim 1, characterized in that: The horizontal adjustment component (3) comprises a horizontal frame (31), a screw rod (32), a slider (33), and a drive motor (34); the two horizontal frames (31) are respectively mounted on the inner walls of the two beams (2); the two screw rods (32) are respectively rotatably connected to the two horizontal frames (31), and one end of the screw rod (32) extends to the outside of the horizontal frame (31); the slider (33) is slidably arranged between the inner walls of the horizontal frame (31), and the slider (33) is threadedly connected to the screw rod (32); the drive motor (34) is mounted on a side of the reinforcement plate (7) away from the battery pack (5), and the output shaft of the drive motor (34) is respectively connected to the ends of the two screw rods (32) through a pulley and a belt; and a slot (331) is configured on the side wall of the slider (33).

4. A pure electric tractor chassis structure according to claim 3, characterized in that: The vertical adjustment assembly (4) comprises a fixing frame (41), a lifting rod (42) and an electric rod (43); the fixing frame (41) is installed between a plurality of slots (331); both sides of the inner wall of the fixing frame (41) are provided with notches; the side wall of the lifting rod (42) is slidably fitted with the notches; and the electric rod (43) is installed between the side wall of the lifting rod (42) and the surface of the fixing frame (41).

5. The pure electric tractor chassis structure according to claim 4, characterized in that: The number of the vertical adjustment components (4) is set to be multiple groups, and the number of the vertical adjustment components (4) is consistent with the number of the battery groups (5).

6. A tractor, comprising the pure electric tractor chassis structure according to any one of claims 1 to 5, characterized in that: It also includes a tilt sensor (8), a tire (9) and a front vehicle (10), wherein the tilt sensor (8) is mounted on the bottom of one side of the cross beam (2), the tires (9) are distributed in a rectangular array and are mounted and connected to the frame (1), and the front vehicle (10) is mounted on the surface of the cross beam (2).

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