Boom anti-tilt system, crawler crane and control method

Abstract

The present invention discloses a boom anti-tilt system, a crawler crane and a control method, which relate to the field of engineering machinery and are used to improve the stability of the boom anti-tilt system when switching between different pressure working conditions. The boom anti-tilt system includes a hydraulic pump, a stop valve, an oil cylinder, a first overflow valve and a pilot control valve. The hydraulic pump includes an oil outlet. The stop valve is fluidically connected to the oil outlet. The oil cylinder includes a rod chamber oil port and a rodless chamber oil port; the rod chamber oil port and the rodless chamber oil port are both fluidically connected to the stop valve. The first overflow valve is fluidically connected to the rodless chamber of the oil cylinder; the pilot control valve is also unidirectionally fluidically connected to the pilot end of the first overflow valve. The above technical solution greatly reduces the fatigue impact of the step impact of the reaction force of the oil cylinder on the mechanical structure, while making the system run more smoothly.

Description

Technical Field

[0001] The present invention relates to the field of engineering machinery, and in particular to a boom anti-tilt system, a crawler crane and a control method. Background Art

[0002] Crawler cranes, also known as crawler cranes, are a type of mobile crane. Crawler cranes must be self-balancing during lifting operations. The center of gravity of the entire structure (including the load) must always be within the support range of the crawler tracks to ensure safe lifting. Any situation that causes the center of gravity to exceed the support range of the crawler tracks could result in a crawler crane rollover.

[0003] When the boom exceeds a certain angle, if the tension on the mast is too low, the boom may tip backward. The boom anti-tip system effectively eliminates this risk. When the tension on the mast falls below a certain limit, the anti-tip system provides a certain amount of reverse thrust to ensure the boom and the entire machine remain in a safe state.

[0004] In the related art, there are the following two types of boom anti-tilt systems.

[0005] Spring-loaded telescopic pushrods: A compression spring provides a pre-thrust to the telescopic mechanical pushrod. As the boom angle increases (raises), the spring force increases, thereby increasing the boom's reverse thrust. When the boom reaches its maximum angle, the pushrod provides maximum thrust. Due to the compression and size limitations of the spring, this design is typically used for smaller crane systems.

[0006] Hydraulic Cylinder Type: When a larger thrust or a longer telescopic stroke is required, the design of a spring telescopic push rod will be limited. In this case, using a hydraulic cylinder instead of a spring telescopic push rod can provide a larger telescopic stroke and, at the same time, can provide greater thrust within a limited size.

[0007] To meet the demand, the system adopts two-stage pressure control. When the boom requires less thrust, the cylinder only needs to maintain a smaller thrust; when the boom requires more thrust, the cylinder only needs to provide a larger thrust.

[0008] The inventors have discovered that there are at least the following problems in the prior art: When the boom anti-tilt system switches from low pressure to high pressure, the system pressure will change in a step-like manner in a short period of time, which has a relatively large impact on the entire system. When the boom anti-tilt system switches from high pressure to low pressure, the rapid drop in system pressure will cause the system to generate rapid overflow vibration in a short period of time. During operation, the system will often switch back and forth between high pressure and low pressure, and the reverse thrust of the cylinder on the boom will change in a step-like manner. The cylinder will generate repeated step-like reaction forces on the boom control winch and the boom, affecting the fatigue life and working stability of the system. Summary of the Invention

[0009] The present invention provides a boom anti-tilt system, a crawler crane and a control method, which are used to improve the stability of the boom anti-tilt system when switching between different pressure working conditions.

[0010] An embodiment of the present invention provides a boom anti-tilt system, comprising:

[0011] a hydraulic pump, including an oil outlet;

[0012] a pilot control valve, mounted on the control end of the hydraulic pump;

[0013] A stop valve in fluid communication with the oil outlet

[0014] An oil cylinder comprising a rod chamber oil port and a rodless chamber oil port; both the rod chamber oil port and the rodless chamber oil port are in fluid communication with the stop valve; and

[0015] The first relief valve is in fluid communication with the rodless chamber of the oil cylinder; the pilot control valve is also in one-way fluid communication with the pilot end of the first relief valve.

[0016] In some embodiments, the boom anti-tilt system further comprises:

[0017] The second relief valve is arranged in the oil path between the pilot end of the first relief valve and the pilot control valve.

[0018] In some embodiments, the boom anti-tilt system further comprises:

[0019] The solenoid valve is arranged on the oil circuit between the pilot end of the first relief valve and the second relief valve to control the opening and closing of the oil circuit.

[0020] In some embodiments, the number of the oil cylinders is two, and the two oil cylinders are arranged in parallel.

[0021] In some embodiments, each of the oil cylinders is correspondingly provided with a first overflow valve.

[0022] In some embodiments, all of the first relief valves are in fluid communication with the same second relief valve.

[0023] In some embodiments, the first relief valve comprises a pilot-operated relief valve.

[0024] In some embodiments, the spring force of the first relief valve is set to the maximum working pressure of the oil cylinder.

[0025] In some embodiments, the hydraulic pump is configured such that when the cylinder does not perform any extension or retraction action, the hydraulic pump is in a zero displacement position.

[0026] An embodiment of the present invention further provides a crawler crane, comprising the boom anti-tilt system provided by any technical solution of the present invention.

[0027] The embodiment of the present invention further provides a boom anti-tilt system control method, comprising the following steps:

[0028] Calculate the first set pressure of the pilot control valve of the boom anti-tilt system based on the boom position of the crawler crane and the pulling force generated by the boom on the mast;

[0029] The hydraulic pump is used to supply hydraulic oil to the oil cylinder until the pressure of the oil cylinder reaches a second set pressure; the second set pressure is greater than the first set pressure;

[0030] The oil circuit where the first overflow valve is located is opened to maintain the pressure of the oil cylinder stable.

[0031] In some embodiments, the boom anti-tilt system control method further includes the following steps:

[0032] In an abnormal situation, the oil circuit where the first relief valve is located is disconnected; the abnormal situation includes at least one of the following: loss of pressure in the oil cylinder, overpressure in the oil cylinder, excessive pressure difference in the oil cylinder, alarm, and emergency stop.

[0033] The boom anti-tilt system provided by the above technical solution realizes synchronous control of the system pressures on the cylinder side and the hydraulic pump side by controlling the outlet pressure of the hydraulic pump and the overflow pressure of the first overflow valve through the pilot overflow valve, thereby realizing stepless pressure regulation of the system and adjusting the system pressure according to a smooth curve. This greatly reduces the fatigue impact of the step impact of the cylinder reaction force on the mechanical structure and makes the system run more smoothly. In addition, the above-mentioned boom anti-tilt system adopts a stepless pressure regulation function, which can arbitrarily adjust the pressure value of the boom anti-tilt system within the boom angle adjustment control range according to the working conditions, and then adjust the thrust value applied to the boom by the cylinder. If necessary later, under any working conditions, the system pressure of the boom anti-tilt system can be flexibly controlled and steplessly adjusted by optimizing the control program. Moreover, even if the pulling force of the boom on the mast changes, during the process of switching between low pressure and high pressure, the system pressure will not change in a step within a short period of time because the pressure change rate can be controlled by the pilot control valve. The overall impact on the system is small, and no short-term rapid overflow vibration will occur, thereby improving the fatigue life and working stability of the system. In addition, the number of solenoid valves involved in the control in the system is small, the system is relatively sophisticated, and the probability of system failure is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0035] Figure 1 This is a schematic structural diagram of the boom anti-tilt system provided in an embodiment of the present invention.

[0036] Reference numerals:

[0037] 1. Hydraulic pump; 2. Stop valve; 3. Cylinder; 4. First relief valve; 5. Second relief valve; 6. Solenoid valve; 7. Pilot control valve; 11. Oil outlet; 12. Pump built-in control valve; 31. Rod chamber oil port; 32. Rodless chamber oil port. DETAILED DESCRIPTION

[0038] The following combination Figure 1 The technical solution provided by the present invention is described in more detail.

[0039] A crawler crane is a device used for lifting heavy objects. It consists of a boom for lifting heavy objects and a hydraulic cylinder to protect the boom. The hydraulic cylinder assists the boom of a crawler crane, preventing it from tipping backward during lifting. The hydraulic cylinder is part of the boom's anti-tip system, which supplies hydraulic oil to the cylinder to maintain the required pressure. This system prevents the boom from tipping backward, potentially leading to crane overturning accidents or eliminating potential overturning hazards.

[0040] See also Figure 1 An embodiment of the present invention provides a boom anti-tilt system, comprising a hydraulic pump 1, a stop valve 2, an oil cylinder 3, a first relief valve 4, and a pilot control valve 7. The hydraulic pump 1 includes an oil outlet 11. The stop valve 2 is in fluid communication with the oil outlet 11. The oil cylinder 3 includes a rod chamber oil port 31 and a rodless chamber oil port 32; both the rod chamber oil port 31 and the rodless chamber oil port 32 are in fluid communication with the stop valve 2. The first relief valve 4 is in fluid communication with the rodless chamber of the oil cylinder 3; the pilot control valve 7 is also in one-way fluid communication with the pilot end of the first relief valve 4.

[0041] The hydraulic pump 1 adopts a remote pressure-controlled variable pump. The oil outlet pressure of the hydraulic pump 1 is controlled by the pilot control valve 7. After the pressure at the outlet 11 of the hydraulic pump 1 reaches the limit of the pilot control valve (valve RF4) 7, the pilot control valve 7 remains in an overflow state, and its overflow volume is very small, which is referred to as a small-flow overflow. When the outlet oil pressure of the hydraulic pump 1 is lower than the set value of the pilot control valve 7, the hydraulic pump 1 will continue to supply oil until the outlet oil pressure of the hydraulic pump 1 is equal to the set value of the pilot control valve 7. When the oil cylinder 3 has no extension and contraction action, the variable pump controls the built-in hydraulic variable mechanism of the hydraulic pump 1 according to the external control pressure to control the hydraulic pump 1 to be in the zero-displacement position, thereby achieving an energy-saving effect.

[0042] Pilot control valve 7 (Y430) uses a powered, step-down, solenoid-operated proportional relief valve. In the event of a system failure or emergency stop, pilot control valve 7 is de-energized, allowing the remote control circuit to reach the maximum pressure setting of pilot control valve 7, ensuring system safety. Pilot control valve 7 (i.e., valve RF4) simultaneously controls the output pressure of hydraulic pump 1 and the pressure of first relief valve 4 of cylinder 3. Furthermore, by adjusting the input signal to pilot control valve 7 (i.e., valve RF4), the pump output pressure and the relief valve setting of anti-tilt cylinder 3 can be adjusted synchronously.

[0043] A shutoff valve 2 is installed downstream of the hydraulic pump 1. This valve 2 includes a first port, a second port, a third port, and a fourth port. The first port is fluidically connected to the hydraulic pump 1's oil outlet 11, while the third port is connected to the oil tank. The second and fourth ports serve as working oil ports. The second port is fluidically connected to the rod chamber port 31 of the cylinder 3, while the fourth port is fluidically connected to the rodless chamber port 32 of the cylinder 3.

[0044] For example, there are two cylinders 3, arranged in parallel. Both cylinders 3 are fluidically connected to the same shutoff valve 2 in the same manner. The second port of shutoff valve 2 is connected to the rod chamber ports 31 of both cylinders 3 via two hydraulic branches. The fourth port of shutoff valve 2 is connected to the rodless chamber ports 32 of both cylinders 3 via two hydraulic branches.

[0045] The connection mode and working mechanism of the two oil cylinders 3 are the same, and the following is a detailed description of one of the oil cylinders 3 as an example. Figure 1 The description is made taking the oil cylinder 3 on the left in the middle as an example.

[0046] See also Figure 1 The rodless chamber oil port 32 of the oil cylinder 3 is also connected to a first relief valve 4. Each rodless chamber oil port 32 of the oil cylinder 3 is connected to a first relief valve 4. The first relief valve 4 is used to control the real-time pressure of the oil cylinder 3, so that the thrust of the oil cylinder 3 on the boom is maintained at the set value.

[0047] First relief valves 4, RF1 and RF2, are installed directly or via steel pipes on the rodless chamber oil port 32 of cylinder 3. One cylinder 3 is equipped with valve RF1, while the other is equipped with valve RF2 to meet the safety requirements of relevant regulations for load-holding function control. The first relief valves 4 are pilot-operated, low-leakage relief valves. The spring force of both first relief valves 4 is set to the maximum operating pressure of cylinder 3 in the boom anti-tilt system, thereby limiting the maximum thrust limit of cylinder 3. This maximum thrust limit is calculated based on the performance parameters of the crawler crane in which the boom anti-tilt system is installed.

[0048] During the operation of the crawler crane, there are two pressure changes in the boom anti-tilt system: one is switching from a high-pressure state to a low-pressure state, and the other is switching from a low-pressure state to a high-pressure state.

[0049] The following details the specific operating conditions corresponding to low-pressure and high-pressure states. The required thrust is calculated based on the boom angle and the pullback force exerted by the boom on the mast. This can be fed back to the control system via a pullback sensor. Pullback force is the reaction to the pullback.

[0050] When the boom (not shown) is at a low angle, the center of gravity of the boom and the load is forward and away from the crane's center of gravity. There is no risk of the boom tipping over. At this point, cylinder 3 only needs to maintain a relatively small thrust to ensure the crawler crane meets safety requirements for lifting. This operating condition is considered low-pressure.

[0051] When the boom angle exceeds a certain value and the tension exerted by the boom on the mast exceeds a certain limit, the boom remains in a low-overturning risk zone despite being heavily loaded. Cylinder 3 only needs to maintain a relatively low thrust to ensure the crawler crane meets safety requirements for lifting. This operating condition is considered low-pressure.

[0052] When the boom angle exceeds the set value and the tension exerted by the boom on the mast falls below the specified value, the risk of the boom tipping over increases. The oil pressure in cylinder 3 of the system is maintained at the high-pressure level to provide sufficient forward thrust for the boom. Cylinder 3 must maintain a relatively high thrust to ensure system safety and that the crawler crane still meets safety requirements for lifting. This operating condition is considered a high-pressure condition.

[0053] Regardless of high-pressure or low-pressure conditions, the pressure value set by the pilot control valve 7 can be gradually changed, for example, gradually increased at a certain rate, so that the system pressure changes smoothly without sudden pressure changes.

[0054] The pressure setting for cylinder 3 (set by pilot control valve 7) is calculated by the control system using the boom angle and the force exerted by the boom on the mast. Under all circumstances, regardless of whether the crawler crane switches from low-pressure to high-pressure or vice versa, the pressure in cylinder 3 remains at this calculated value.

[0055] When the crawler crane switches from a low-pressure working condition to a high-pressure working condition, such as when the boom is raised, the cylinder 3 is in a passive push-back state, and the hydraulic oil in the cylinder 3 is further compressed, causing the pressure in the rodless chamber of the cylinder 3 to increase. Since the rodless chamber oil port 32 of the cylinder 3 is connected to the first relief valve 4, and the first relief valve 4 is in fluid communication with the pilot control valve 7. On the one hand, the pilot control valve 7 controls the output pressure of the hydraulic pump 1, so that the displacement of the hydraulic pump 1 returns to zero and the hydraulic pump 1 does not output hydraulic oil; on the other hand, the pilot control valve 7 causes the two first relief valves 4 (valve RF1 and valve RF2) to be conductive and overflow, and the two first relief valves 4 will overflow excess hydraulic oil, so that the pressure in the cylinder 3 is maintained at the pressure value set by the pilot control valve 7.

[0056] When a crawler crane switches from a high-pressure to a low-pressure operating condition, such as when lowering the boom, the pressure in cylinder 3 decreases, causing it to extend. The displacement of hydraulic pump 1 automatically adjusts to ensure the output flow meets the required extension of cylinder 3, thereby maintaining the pressure in cylinder 3 at the system's set value. After the hydraulic system's pressure drops, the variable displacement pump increases synchronously, outputting high-pressure oil to replenish the system's oil pressure, as the pressure set by pilot control valve 7 varies according to the system's settings. This maintains the flow of oil into cylinder 3, increasing its pressure. The oil pressure in cylinder 3 continues to increase until it reaches the set value, where it is then steadily maintained.

[0057] If the boom is retracted, the hydraulic cylinder 3 is compressed by the boom, and the pressure overflows through the first relief valve 4, maintaining the pressure in the hydraulic cylinder 3 at the system set value. During this process, the second relief valve 5 generates a pressure differential to adjust the opening and closing sequence, and the displacement of the hydraulic pump 1 returns to zero position in advance, and no oil is output. In other words, the hydraulic pump 1 does not need to supply oil during this process.

[0058] The above technical solution of the embodiment of the present invention realizes the synchronous control of the oil outlet pressure of the hydraulic pump 1 and the oil pressure in the cylinder 3 by setting the first overflow valve 4 at the rodless chamber oil port 32 of the cylinder 3 and adopting the pilot control valve 7 to simultaneously control the pilot pressure of the hydraulic pump 1 and the overflow pressure of the first overflow valve 4. In addition, the number of components is small and no additional components need to be set. The control accuracy is high, error accumulation is not easy to occur, the system failure rate is low, the hydraulic system is responsive, and the system pressure is stable and not easy to fluctuate.

[0059] Continue to see Figure 1 In some embodiments, the boom anti-tilt system further includes a second relief valve 5, which is disposed in the oil path between the pilot end of the first relief valve 4 and the pilot control valve 7. The second relief valve 5 is one-way oil-passing and closed in the reverse direction.

[0060] The opening sequence of the first and second relief valves 4 and 5 is controlled by establishing a pressure differential. Specifically, the pump displacement is adjusted to zero before the first relief valve 4 opens. The pressure applied by the second relief valve 5 ensures that the opening pressure of the first relief valve 4 is slightly higher than the control pressure required to return the pump displacement to zero.

[0061] The second relief valve 5 can offset the pressure difference between the built-in pressure of the variable pump and the set pressure of the pilot control valve 7, so that when the pressure in the cylinder 3 reaches the set value of the first relief valve 4, the displacement of the variable pump can be changed in advance. The relief pressure of the two first relief valves 4 is the same, both equal to the sum of the relief pressure of the pilot control valve 7 and the relief pressure of the second relief valve 5. When the boom is raised and the cylinder 3 is compressed, the pressure cut-off setting value of the variable pump is equal to the relief pressure of the pilot control valve 7. This pressure cut-off setting value is always lower than the actual control value of the two first relief valves 4 (RF1 and RF2). The variable pump has switched to zero displacement before the two first relief valves 4 are opened. This makes the system less prone to high-flow overflow heating, achieving energy-saving effects.

[0062] In some embodiments, all first relief valves 4 are in fluid communication with the same second relief valve 5. Synchronous control of the two oil cylinders 3 and the hydraulic pump 1 is achieved through one second relief valve 5 and one pilot control valve 7.

[0063] Continue to see Figure 1 In some embodiments, the boom anti-tilt system further includes a solenoid valve 6, which is disposed in the oil circuit between the pilot end of the first relief valve 4 and the second relief valve 5 to control the on and off of the oil circuit.

[0064] The solenoid valve 6 is specifically a two-way solenoid valve. The first relief valve 4 and solenoid valve 6 of one cylinder 3 are integrated into the same hydraulic integrated block, while the first relief valve 4 and solenoid valve 6 of the other cylinder 3 are integrated into another hydraulic integrated block. In the event of system failure or abnormal pressure, the pilot oil circuit of the first relief valve 4 can be directly shut off, so that the actual control pressure of the first relief valve 4 reaches the setting of its own spring, thereby meeting the fail-safe requirements of the system design. In addition, under normal circumstances, the solenoid valve 6 is in the on state; in abnormal circumstances, the solenoid valve 6 is disconnected, and the cylinder 3 maintains a high pressure, which plays a protective role.

[0065] When the first relief valve 4 is needed to control the pressure of the oil cylinder 3, the solenoid valve 6 is turned on so that the oil circuit between the pilot end of the first relief valve 4 and the second relief valve 5 and the pilot control valve 7 is connected, and the oil cylinder 3 can be controlled by the pilot control valve 7. If the crawler crane has any failure, alarm, emergency stop or other phenomena, the solenoid valve 6 (Y410 and Y420) will be powered off and closed. When the oil cylinder 3 is continuously reversed, the pressure is maintained at the set value of the first relief valve 4 to ensure that the boom has sufficient anti-tilt thrust. At the same time, other actions of the boom anti-tilt system are stopped synchronously. All actions except the boom anti-tilt system are stopped in the event of failure, alarm and emergency stop.

[0066] An embodiment of the present invention further provides a crawler crane, comprising the boom anti-tilt system provided by any technical solution of the present invention.

[0067] The boom anti-tilt system is a hydraulic system that converts mechanical energy into hydraulic energy through a hydraulic pump 1 to drive the actuator (hydraulic motor or cylinder 3) to work.

[0068] After the boom anti-tilt system is activated, the relief pressure of pilot control valve 7 (Y430) is determined based on the boom position and the tension exerted by the boom on the mast. This pressure is then adjusted to the first set pressure. During this pressure adjustment process, the control program limits the pressure change rate of the pilot relief valve to ensure smooth overall system pressure changes.

[0069] When the pilot control valve 7 controls the system pressure to rise, the pressure in the oil cylinder 3 will rise synchronously.

[0070] When the pressure in cylinder 3 reaches the designed pressure value, solenoid valve 6 (Y410 and Y420) is energized. The boom anti-tilt system can enter the working state and maintain the system pressure stable.

[0071] During the boom lowering process, the pressure in cylinder 3 decreases and cylinder 3 extends. When the system pressure drops, the displacement of the variable pump increases synchronously, outputting high-pressure oil to replenish the pressure in cylinder 3 and stabilize it at the set value.

[0072] During boom raising, cylinder 3 is passively pushed back, further compressing the hydraulic oil within it and causing the pressure to rise. Combined with pressure control by pilot control valve 7, hydraulic pump 1 returns to zero displacement and stops outputting. First relief valve 4 (RF1 and RF2) releases excess hydraulic oil, maintaining the pressure in cylinder 3 at the value set by the remote control valve.

[0073] The above technical solution allows for stepless adjustment of the pressure in cylinder 3. By controlling the rate of change of pressure in the pilot valve, the pressure in cylinder 3 is adjusted smoothly, minimizing the impact of the boom anti-tilt system on the boom system and boom winch, significantly extending the fatigue life of the system and ensuring system operational stability.

[0074] When the system switches from high-pressure state to pressure relief shutdown, the pressure is slowly reduced by the pilot control valve 7 (RF4), ensuring the smooth operation of the system.

[0075] The embodiment of the present invention further provides a boom anti-tilt system control method, which can be implemented using the boom anti-tilt system provided by any of the above technical solutions. The boom anti-tilt system control method includes the following steps:

[0076] First, according to the boom position of the crawler crane and the pulling force generated by the boom on the mast, the first set pressure of the pilot control valve 7 of the boom anti-backward tilt system is calculated. The first set pressure can be adjusted in real time as needed.

[0077] Next, hydraulic pump 1 supplies hydraulic oil to cylinder 3 until the pressure in cylinder 3 reaches a second set pressure, which is greater than the first set pressure. The second set pressure is equal to the sum of the first set pressure and the pressure differential across pump-internal control valve 12. The pressure differential across pump-internal control valve 12 is between 7 and 20 bar. Pump-internal control valve 12 is a control valve built into the pump. The pressure differential across pump-internal control valve 12 is set by its spring.

[0078] Finally, the oil circuit where the first relief valve 4 is located is opened to keep the pressure of the oil cylinder 3 stable.

[0079] In some embodiments, the boom anti-tilt system control method also includes the following steps: in an abnormal situation, disconnecting the oil circuit where the first overflow valve 4 is located; the abnormal situation includes at least one of the following: the cylinder loses pressure, the cylinder is over-pressured, the pressure difference of the cylinder is too large, component failure, alarm, and emergency stop.

[0080] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the protection content of the present invention.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A boom anti-tilt system, characterized in that: include: A hydraulic pump (1), including an oil outlet (11); A pilot control valve (7) installed at the control end of the hydraulic pump (1); a stop valve (2) in fluid communication with the oil outlet (11); The oil cylinder (3) comprises a rod chamber oil port (31) and a rodless chamber oil port (32); the rod chamber oil port (31) and the rodless chamber oil port (32) are both in fluid communication with the stop valve (2); and The first relief valve (4) is in fluid communication with the rodless chamber of the oil cylinder (3); the pilot control valve (7) is also in one-way fluid communication with the pilot end of the first relief valve (4); Wherein, the boom anti-tilt system also includes: a second relief valve (5) provided in the oil path between the pilot end of the first relief valve (4) and the pilot control valve (7); The second overflow valve (5) is configured to offset the pressure difference between the built-in pressure of the hydraulic pump (1) and the set pressure of the pilot control valve (7), so that when the pressure of the oil cylinder (3) reaches the set value of the first overflow valve (4), the displacement of the hydraulic pump (1) changes in advance.

2. The boom anti-tilt system according to claim 1, characterized in that: Also includes: The solenoid valve (6) is arranged on the oil circuit between the pilot end of the first relief valve (4) and the second relief valve (5) to control the opening and closing of the oil circuit.

3. The boom anti-tilt system according to claim 1, characterized in that: The number of the oil cylinders (3) is two, and the two oil cylinders (3) are arranged in parallel.

4. The boom anti-tilt system according to claim 3, characterized in that: Each oil cylinder (3) is correspondingly provided with a first overflow valve (4).

5. The boom anti-tilt system according to claim 4, characterized in that: All of the first relief valves (4) are in fluid communication with the same second relief valve (5).

6. The boom anti-tilt system according to claim 1, characterized in that: The first overflow valve (4) comprises a pilot-operated overflow valve.

7. The boom anti-tilt system according to claim 1, characterized in that: The spring force of the first overflow valve (4) is set to the maximum working pressure of the oil cylinder (3).

8. The boom anti-tilt system according to claim 1, characterized in that: The hydraulic pump (1) is configured such that when the oil cylinder (3) has no extension or retraction action, the hydraulic pump (1) is in a zero-displacement position.

9. A crawler crane, characterized in that: The invention comprises the boom anti-tilt system according to any one of claims 1 to 8.

10. A method for controlling a boom anti-tilt system, characterized in that: The boom anti-tilt system according to any one of claims 1 to 8 is used to implement the method, and the method comprises the following steps: Calculating a first set pressure of a pilot control valve (7) of a boom anti-tilt system according to a boom position of the crawler crane and a pulling force value generated by the boom on the mast; The hydraulic pump (1) is used to supply hydraulic oil to the oil cylinder (3) until the pressure of the oil cylinder (3) reaches a second set pressure; the second set pressure is greater than the first set pressure; The oil circuit where the first overflow valve (4) is located is opened so that the pressure of the oil cylinder (3) is maintained stable.

11. The boom anti-backward tilt system control method according to claim 10, characterized in that: The following steps are also included: In an abnormal situation, the oil circuit where the first overflow valve (4) is located is disconnected; the abnormal situation includes at least one of the following: loss of pressure in the oil cylinder, overpressure in the oil cylinder, excessive pressure difference in the oil cylinder, component failure, alarm, and emergency stop.

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