Cab turnover mechanism and commercial vehicle

Abstract

The invention belongs to the technical field of commercial vehicle manufacturing, and discloses a cab turnover mechanism and a commercial vehicle. A lower through ring is formed at the lower end of the hydraulic cylinder, a first shell and a third shell are installed on the two sides of the lower through ring, the first shell is communicated with the third shell through the lower through ring, a first positioning pin is installed in the first shell, a third positioning pin is installed in the third shell, and a second positioning pin is clamped between the first positioning pin and the third positioning pin. An oil inlet is formed in the side, away from the lower through ring, of the third shell and communicates with the hydraulic oil way, the first positioning pin abuts against the first shell through the positioning spring, the lower through ring is hinged to the buffer piston, and the buffer piston is installed in the buffer cavity through the buffer spring. The problem that in the prior art, a cab and a frame move mutually on a bumpy road, and consequently sealing of a hydraulic cylinder fails finally is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of commercial vehicle manufacturing, and particularly relates to a cab tilting mechanism and a commercial vehicle. Background Art

[0002] Trucks usually install the engine on the frame under the cab, and the cab is elastically connected to the frame. When repairing and maintaining the vehicle, the driver needs to tilt the cab to a certain angle to facilitate necessary operations. Usually, a cab tilting mechanism is used for processing. The cab tilting mechanism is a mechanical device that can tilt the cab forward, simplifying the vehicle repair and maintenance process and improving work efficiency and safety. Specifically, the cab tilting mechanism can easily tilt the cab when repair is needed, thus providing a larger working space and facilitating the repair and maintenance of components such as the engine and transmission.

[0003] Existing cab tilting mechanisms mostly raise the cab by relying on hydraulic power through hydraulic cylinders. The hydraulic tilting system has a large lifting force and can easily lift a relatively heavy cab. For the existing tilting cab structure (such as the publication number CN219544926U), one end of the cab main body is rotatably hinged to the frame, the fixed end of the lifting cylinder is connected to the frame, and the telescopic end of the lifting cylinder is connected to the cab main body. The cab is driven to tilt by the telescopic movement of the lifting cylinder, thus facilitating repair and reducing the labor intensity and repair cost of maintenance.

[0004] However, when the commercial vehicle is in a non-tilting state, the cab is generally elastically connected to the frame and is also connected through a hydraulic cylinder, which can reduce the impact of the road surface on the cab and the driver inside the cab. When the vehicle is driving and the road surface is bumpy, the frame will generate an impact in the direction perpendicular to the vehicle driving direction. Because the cab itself has a relatively large mass, a large impact will occur in the hydraulic cylinder of the hydraulic tilting structure connecting the cab and the frame. In a short time, the piston in the hydraulic cylinder will move a large distance, generating a large pressure in the hydraulic cylinder. Under the repeated action of this pressure, the seal of the hydraulic cylinder often fails, ultimately resulting in the problem that the hydraulic cylinder cannot work properly. Summary of the Invention

[0005] The purpose of the present invention is to provide a cab tilting mechanism and a commercial vehicle to solve the problem that the cab and the frame move relative to each other on a bumpy road surface in the prior art, resulting in the ultimate failure of the hydraulic cylinder seal.

[0006] To achieve this purpose, the present invention adopts the following technical solutions: The present invention provides a cab tilting mechanism, which includes a hydraulic cylinder. A lower through-ring is formed at the lower end of the hydraulic cylinder. A first housing and a third housing are installed on both sides of the lower through-ring. The first housing is communicated with the third housing through the lower through-ring. A first positioning pin is installed in the first housing, and a third positioning pin is installed in the third housing. A second positioning pin is clamped between the first positioning pin and the third positioning pin. An oil inlet is provided on one side of the third housing away from the lower through-ring, and the oil inlet is communicated with a hydraulic oil circuit. The first positioning pin abuts against the first housing through a positioning spring. The lower through-ring is hinged to a buffer piston, and the buffer piston is installed in a buffer cavity through a buffer spring. The length of the first positioning pin is less than the inner cavity length of the first housing. The length of the second positioning pin is the same as the axial length of the lower through-ring. The length of the third positioning pin is the same as the inner cavity length of the third housing.

[0007] Preferably, a connecting pipe is connected to the hydraulic cylinder, and the connecting pipe is communicated with the hydraulic oil circuit.

[0008] Preferably, the first positioning pin, the second positioning pin, and the third positioning pin are cylinders.

[0009] Preferably, a telescopic rod is slidably installed in the hydraulic cylinder. The telescopic rod reciprocates along its own axis, and an upper through-ring is formed at the upper end of the telescopic rod.

[0010] Preferably, a third groove is provided on one side of the third positioning pin close to the oil inlet.

[0011] Preferably, a first groove is formed in the first positioning pin, and the positioning spring is installed in the first groove.

[0012] Preferably, a ventilation hole is installed on the outer wall of the first housing, and the ventilation hole is communicated with the first groove.

[0013] Preferably, a first sealing ring and a second sealing ring are respectively installed at the end and the bottom of the telescopic rod. A first port and a second port are formed on the connecting pipe. The first port is arranged between the first sealing ring and the second sealing ring, and the second port is installed at the bottom of the second sealing ring.

[0014] Preferably, the upper through-ring and the lower through-ring are annular.

[0015] A commercial vehicle includes the cab tilting mechanism described above, and further includes a cab and a frame. The cab is rotatably connected to the upper through-ring. The buffer cavity is connected to the frame. The first housing and the third housing are fixed on the frame.

[0016] Beneficial effects: When the second positioning pin is completely inside the lower through-ring, the second positioning pin moves along the axis of the buffer spring following the lower through-ring. The buffer spring absorbs the vibration transmitted from the ground to the vehicle frame and the cab through compression and release, reducing the impact on the hydraulic cylinder through the buffer spring and extending the service life of the hydraulic cylinder seal. When the hydraulic oil circuit delivers oil to the oil inlet, it pushes the third positioning pin to move towards the first positioning pin, causing part of the second positioning pin to enter the first housing and part of the third positioning pin to enter the lower through-ring, restricting the movement of the lower through-ring on the second positioning pin along the axis of the buffer spring. At this time, when the cab is flipped, stable support is required on the lower side of the hydraulic cylinder. After the flipping is completed, the oil in the hydraulic oil circuit is drawn out, and the positioning spring pushes the first positioning pin to move, enabling the second positioning pin to return inside the lower through-ring. Brief Description of the Drawings

[0017] Figure 1 is the front view cross-sectional schematic diagram of the lifting state of the hydraulic cylinder of the present invention;

[0018] Figure 2 is the side view cross-sectional schematic diagram of the lifting state of the hydraulic cylinder of the present invention;

[0019] Figure 3 is the schematic diagram of the non-lifting state of the hydraulic cylinder of the present invention;

[0020] Figure 4 is the partial schematic diagram of the first positioning pin of the present invention;

[0021] Figure 5 is the partial enlarged view of the cross-section of the lower through-ring of the present invention.

[0022] In the figure: 1. First positioning pin; 11 - Support column; 2. Second positioning pin; 3. Third positioning pin; 4. Positioning spring; 5. First housing; 6. Third housing; 8. Vent hole; 9. First groove; 10. Third groove; 11. Hydraulic oil connector; 12. Telescopic rod; 13. Hydraulic cylinder; 14. First sealing ring; 15. Second sealing ring; 17. Connecting pipe; 19. Buffer cavity; 21. Buffer piston; 22. Buffer spring; 23. Lower through-ring; 24. Upper through-ring; 25. Chamfer. Detailed Description of the Embodiment

[0023] The present invention will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Additionally, it should be noted that for the sake of description, only parts related to the present invention are shown in the drawings rather than all the structures.

[0024] In the description of the present invention, unless otherwise clearly defined and limited, the terms "connected", "connected to", and "fixed" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal connection of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] In the present invention, unless otherwise clearly defined and limited, the first feature being "above" or "below" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features therebetween. Moreover, the first feature being "above", "over", and "on" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "below", "under", and "beneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely indicates that the horizontal height of the first feature is lower than that of the second feature.

[0026] In the description of this embodiment, the orientation or positional relationships such as "above", "below", "right", etc. are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of description and simplifying the operation, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for distinction in description and have no special meanings.

[0027] In the design and maintenance system of commercial vehicles, the cab tilting mechanism, as a key functional module, undertakes the dual missions of balancing the daily driving comfort and the maintenance convenience. Through special structural design, this mechanical device enables the cab to tilt forward around the frame hinge point, providing sufficient operating space for the maintenance operation of the engine compartment. Its core value lies in the innovation of the mechanical structure, effectively reducing the working intensity of maintenance personnel, improving the vehicle maintenance efficiency and enhancing the operation safety.

[0028] The current mainstream technology generally uses a hydraulic drive system to achieve the cab flipping function. The hydraulic actuator consists of a lifting cylinder, a hydraulic pump station and a control valve group, which generates a strong thrust through the pressure conduction of hydraulic oil. The fixed end of the lifting cylinder is anchored to the main body of the frame, and the telescopic end is rigidly connected to the cab structure. Under maintenance conditions, the hydraulic system drives the piston rod to extend, pushing the several-ton cab to rotate around the articulated axis until it reaches an engineering inclination angle of 50°-70°. The advantage of this hydraulic drive solution lies in its excellent power density characteristics. A single-cylinder system can output a lifting force of tens of kilonewtons, which can stably lift the all-steel cab assembly of a heavy truck.

[0029] When the vehicle is in normal operation, a composite connection mode is used between the cab and the frame: the elastic suspension system is responsible for absorbing the vibration energy of the road surface, while the hydraulic cylinder participates in the load distribution as an auxiliary support unit. The original intention of the design of this dual connection system is to build a graded vibration reduction mechanism - elastic elements such as rubber bushings filter high-frequency small vibrations, while hydraulic supports deal with low-frequency large shaking. In theory, this structure can maintain the dynamic stability between the cab and the frame, and reduce the impact of bumpy road conditions on the cockpit occupants.

[0030] However, this seemingly reasonable design architecture exposed significant technical defects in actual vehicle operation. When the vehicle is driving on unpaved roads or urban speed bumps, complex relative motion will occur between the frame and the cab. At this time, the hydraulic cylinder is in a passive working state, and its piston rod, which is the telescopic rod mentioned later, needs to perform high-frequency reciprocating motion following the vibration of the frame. Engineering practice has shown that this dynamic working condition will form violent pressure fluctuations inside the hydraulic system: when the frame impacts upward, the cylinder is instantly pressurized to form ultra-high pressure; when the cab lags due to inertia, the cylinder will produce a negative pressure cavity. The peak value of this alternating pressure can reach 2-3 times the rated working pressure of the system, and the vibration frequency often exceeds 10Hz.

[0031] This extreme working condition poses a severe test to the sealing components of the hydraulic system. Traditional polyurethane seals will undergo plastic deformation under continuous high-pressure impact, resulting in gaps on the microscopic sealing surface. Frequent negative pressure suction will accelerate the wear rate of the sealing lip. More seriously, the radial swing of the piston rod caused by vibration will destroy the oil film lubrication state and cause abrasive wear on the metal contact surface. The superposition effect of multiple failure mechanisms has greatly shortened the average trouble-free period of the hydraulic cylinder. Typical failures are abnormal operation such as inability to lift and self-sinking due to hydraulic internal leakage.

[0032] From the perspective of system dynamics analysis, the root cause of the problem lies in the conflicting functional positioning of the hydraulic actuator. In the maintenance condition, the hydraulic system needs to output a large thrust as an active actuator; while in the driving condition, it is passively transformed into a rigid element in the vibration transmission path. This dual role makes it difficult to optimize the system parameters: if the rigidity of the cylinder is increased to enhance the support stability, the vibration transmission effect will be aggravated; if the system stiffness is reduced to improve the vibration damping performance, the reliability of the lifting action will be weakened.

[0033] The existing technical system has not effectively solved this contradiction. Designers often make improvements through passive means such as strengthening the strength of structural components and using high-performance sealing materials. However, this improvement scheme essentially belongs to the delay treatment of the problem consequences and does not touch the core contradiction at the system architecture level. From the perspective of technological evolution, developing a composite drive mechanism with working condition adaptive ability, or realizing the modal separation of mechanical locking and hydraulic lifting, may become an effective path to break through the existing technical bottlenecks.

[0034] Embodiment 1

[0035] To solve the above problems, as Figures 1 to 3 shown, the present invention provides a cab tilting mechanism, including a hydraulic cylinder 13. A lower through-ring 23 is formed at the lower end of the hydraulic cylinder 13. A first housing 5 and a third housing 6 are installed on both sides of the lower through-ring 23. The first housing 5 is communicated with the third housing 6 through the lower through-ring 23. A first positioning pin 1 is installed in the first housing 5, and a third positioning pin 3 is installed in the third housing 6. A second positioning pin 2 is clamped between the first positioning pin 1 and the third positioning pin 3. An oil inlet is provided on one side of the third housing 6 away from the lower through-ring 23, and the oil inlet is communicated with the hydraulic oil circuit. The first positioning pin 1 abuts against the first housing 5 through a positioning spring 4. The lower through-ring 23 is hinged to a buffer piston 21, and the buffer piston 21 is installed in a buffer cavity 19 through a buffer spring 22. The length of the first positioning pin 1 is less than the inner cavity length of the first housing 5. The length of the second positioning pin 2 is the same as the axis length of the lower through-ring 23. The length of the third positioning pin 3 is the same as the inner cavity length of the third housing 6.

[0036] A buffer spring 22 is installed on the lower side of the hydraulic cylinder 13. The lower through-ring 23 is hinged to the buffer spring 22 in the buffer cavity 19. If the vehicle is traveling on a bumpy road, vibrations will be transmitted from the vehicle frame to the hydraulic cylinder 13 of the cab tilting mechanism. By setting the buffer spring 22, the vibrations transmitted to the hydraulic cylinder 13 can be reduced. Furthermore, the moving distance of the piston installed on the telescopic rod 12 in the hydraulic cylinder 13 can be decreased, the service life of the hydraulic cylinder 13 can be prolonged, and thus the service life of the cab tilting mechanism can be extended. During the process of the hydraulic cylinder 13 vibrating following the buffer spring 22, the second positioning pin 2 is arranged in the lower through-ring 23, and the second positioning pin 2 moves along the axis of the buffer spring 22 following the lower through-ring 23. If the cab needs to be tilted when the vehicle is stationary, the hydraulic oil in the hydraulic oil circuit will enter from the oil inlet. A hydraulic oil connector 11 is installed on the oil inlet, which can connect pipelines with different diameters, and push the third positioning pin 3 to move towards the first positioning pin 1. Since the length of the first positioning pin 1 is shorter than the length of the inner cavity of the first housing 5, the positioning spring 4 is gradually compressed, enabling a part of the second positioning pin 2 to enter the first housing 5 and a part of the third positioning pin 3 to enter the lower through-ring 23 to limit the lower through-ring 23, so that the lower through-ring 23 can be fixed between the first housing 5 and the third housing 6, and the buffer spring 22 no longer expands and contracts. Usually, the first housing 5 and the third housing 6 are directly rigidly connected to the vehicle frame, and the lower through-ring 23 can only rotate around the second positioning pin 2. At this time, the hydraulic cylinder 13 is in a stable state. By controlling the telescopic rod 12 in the hydraulic cylinder 13 to extend, the cab on the vehicle frame can be slowly tilted without shaking. If the contact tilting operation in the cab ends, the hydraulic oil in the hydraulic oil circuit will be drawn out from the third housing 6, and the positioning spring 4 returns to its initial state. At this time, the third positioning pin 3 will enter the third housing 6, and the second positioning pin 2 will return to the lower through-ring 23, releasing the locking relationship between the lower through-ring 23 and the first housing 5 and the second housing, and the buffer spring 22 can continue to drive the lower through-ring 23 to move and absorb the vibrations from the ground.

[0037] A connecting pipe 17 is connected to the hydraulic cylinder 13 of the present invention. The connecting pipe 17 is in communication with the hydraulic oil circuit, and the hydraulic cylinder 13 is in communication with the hydraulic oil circuit. Through the hydraulic oil in the hydraulic oil circuit, the telescopic rod 12 in the hydraulic cylinder 13 can be pushed to move. By sharing the same hydraulic pipeline, the complexity of the hydraulic pipeline layout can be reduced. When the hydraulic oil circuit is filled with hydraulic oil, at this time, the third housing 6 will also be filled with hydraulic oil. At the same time, the telescopic rod 12 in the hydraulic cylinder 13 extends under the action of the hydraulic oil, and the lower through-ring 23 at the bottom is also in a limited state, preventing it from moving on the buffer spring 22 while enabling the telescopic rod 12 to push the cab to tilt.

[0038] The first positioning pin 1, the second positioning pin 2, and the third positioning pin 3 are cylinders, which are convenient for maintenance and replacement, and also convenient for reciprocating sliding within the first housing 5, the lower through-ring 23, and the third housing 6. The arc-shaped surface is not prone to dirt accumulation, and can reduce the friction force of the first positioning pin 1, the second positioning pin 2, and the third positioning pin 3 during reciprocating movement.

[0039] A telescopic rod 12 is slidably installed within the hydraulic cylinder 13. The telescopic rod 12 reciprocates along its own axis. An upper through-ring 24 is formed at the upper end of the telescopic rod 12. The inner sides of the upper through-ring 24 and the lower through-ring 23 are cylindrical. Usually, the upper through-ring 24 is generally rotatably installed at the bottom of the cab. A fixed column is formed at the bottom of the cab. The upper through-ring 24 is sleeved on the fixed column, and the upper through-ring 24 can rotate around the fixed column.

[0040] A third groove 10 is provided on one side of the third positioning pin 3 close to the oil inlet, so that the oil fluid can directly rush into the third groove 10 after entering the third housing 6, and move the third positioning pin 3 by pushing. By providing the third groove 10, it is convenient to push the third positioning pin 3 to move, and thus the positioning spring 4 can be compressed, enabling the second positioning pin 2 to shift relative to the lower through-ring 23, and fixing the hydraulic cylinder 13.

[0041] A first groove 9 is formed within the first positioning pin 1. The positioning spring 4 is installed within the first groove 9. By providing the positioning spring 4 in the first groove 9, the first spring can be kept stable. During the movement of the first positioning pin 1, the positioning spring 4 will not shake and can always remain stable with the first positioning pin 1.

[0042] A vent hole 8 is installed on the outer wall of the first housing 5. The vent hole 8 is communicated with the first groove 9. During the movement of the first positioning pin 1 away from the third positioning pin 3, the gas within the first housing 5 will be compressed, causing the first housing 5 to be unable to move. By providing the vent hole 8, the cavity within the first housing 5 can be communicated with the outside, and the gas within the first housing 5 can freely enter and exit, thereby enabling the first positioning pin 1 to move freely under the push of the positioning spring 4 and the third positioning pin 3.

[0043] A first sealing ring 14 and a second sealing ring 15 are respectively installed at the end and bottom of the telescopic rod 12. A first port and a second port are formed on the connecting pipe 17. The first port is arranged between the first sealing ring 14 and the second sealing ring 15, and the second port is installed at the bottom of the second sealing ring 15. The second sealing ring 15 reciprocates with the telescopic rod 12 in the hydraulic cylinder 13. When the telescopic rod 12 is stored in the hydraulic cylinder 13 and the cab does not need to be flipped, the lower through-ring 23 vibrates on the buffer spring 22 to absorb part of the vibration energy, reduce the movement amplitude of the first sealing ring 14 and the second sealing ring 15 in the hydraulic cylinder 13, and extend the service life of the cab flipping mechanism.

[0044] The upper through-ring 24 and the lower through-ring 23 are annular, which can make the upper through-ring 24 rotate more smoothly on the fixed column and also reduce the friction between the second positioning pin 2 in the lower through-ring 23 and the lower through-ring 23.

[0045] The commercial vehicle includes a cab and a frame. The cab is rotatably connected to the upper through-ring 24, the buffer cavity 19 is connected to the frame, and the first housing 5 and the third housing 6 are fixed on the frame.

[0046] Embodiment 2

[0047] As Figure 4 shown, a support column 11 can be formed on one side of the first positioning pin 1 of the present invention close to the vent hole 8. The positioning spring 4 is sleeved on the support column 11. The length of the support column 11 is shorter than the natural length of the positioning spring 4. When the hydraulic pressure pushes the third positioning pin 3, the second positioning pin 2 and the first positioning pin 1 to move towards the vent hole 8, the positioning spring 4 is in a compressed state. As the positioning spring 4 is compressed, the support column 11 will abut against the first housing 5 to prevent the first positioning pin 1 from continuing to move and also avoid the positioning spring 4 from being over-compressed, protecting the positioning spring 4 to have a certain elasticity.

[0048] Embodiment 3

[0049] As Figure 5 shown, chamfers 25 are provided at the edges on both sides of the first positioning pin 1, the second positioning pin 2 and the third positioning pin 3 on the side where the first housing 5, the third housing 6 are in contact with the lower through-ring 23. This facilitates the installation of the first positioning pin 1, the second positioning pin 2 and the third positioning pin 3 in their corresponding positions. During the installation process, due to the presence of the chamfers 25, the difficulty of inserting the positioning pins can be reduced, and the phenomenon of hand scratches on the installer can also be avoided.

[0050] Obviously, the above-mentioned embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, various obvious changes, re-adjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to enumerate all implementation manners here. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A cab tilting mechanism, characterized in that, It includes a hydraulic cylinder (13). A lower through-ring (23) is formed at the lower end of the hydraulic cylinder (13). A first housing (5) and a third housing (6) are installed on both sides of the lower through-ring (23). The first housing (5) is communicated with the third housing (6) through the lower through-ring (23). A first positioning pin (1) is installed in the first housing (5). A third positioning pin (3) is installed in the third housing (6). A second positioning pin (2) is clamped between the first positioning pin (1) and the third positioning pin (3). An oil inlet is formed on one side of the third housing (6) away from the lower through-ring (23). The oil inlet is communicated with a hydraulic oil circuit. The first positioning pin (1) abuts against the first housing (5) through a positioning spring (4). The lower through-ring (23) is hinged to a buffer piston (21). The buffer piston (21) is installed in a buffer cavity (19) through a buffer spring (22). The length of the first positioning pin (1) is less than the inner cavity length of the first housing (5). The length of the second positioning pin (2) is the same as the axial length of the lower through-ring (23). The length of the third positioning pin (3) is the same as the inner cavity length of the third housing (6).

2. The cab tilting mechanism according to claim 1, characterized in that, A connecting pipe (17) is connected to the hydraulic cylinder (13). The connecting pipe (17) is communicated with the hydraulic oil circuit.

3. The cab tilting mechanism according to claim 1, characterized in that, The first positioning pin (1), the second positioning pin (2), and the third positioning pin (3) are cylinders.

4. The cab tilting mechanism according to claim 2, characterized in that, A telescopic rod (12) is slidably installed in the hydraulic cylinder (13). The telescopic rod (12) reciprocates along its own axis. An upper through-ring (24) is formed at the upper end of the telescopic rod (12).

5. The cab tilting mechanism according to claim 1, characterized in that, A third groove (10) is formed on one side of the third positioning pin (3) close to the oil inlet.

6. The cab tilting mechanism according to claim 1, wherein, A first groove (9) is formed in the first positioning pin (1). The positioning spring (4) is installed in the first groove (9).

7. The cab tilting mechanism according to claim 6, wherein A vent hole (8) is installed on the outer wall of the first housing (5). The vent hole (8) is communicated with the first groove (9).

8. The cab tilting mechanism according to claim 4, characterized in that, A first sealing ring (14) and a second sealing ring (15) are respectively installed at the end and the bottom of the telescopic rod (12). A first port and a second port are formed on the connecting pipe (17). The first port is arranged between the first sealing ring (14) and the second sealing ring (15). The second port is installed at the bottom of the second sealing ring (15).

9. The cab tilting mechanism according to claim 4, characterized in that, The upper through-ring (24) and the lower through-ring (23) are annular.

10. A commercial vehicle, characterized in that, It includes the cab overturning mechanism according to claim 9, and further includes a cab and a vehicle frame. The cab is rotatably connected to the upper through-ring (24). The buffer cavity (19) is connected to the vehicle frame. The first housing (5) and the third housing (6) are fixed on the vehicle frame.

Images