Hydraulic system of variable-amplitude tower crane and control method

Abstract

The invention discloses a luffing tower crane hydraulic system and a control method. The luffing tower crane hydraulic system comprises an oil tank, a system controller, a motor, a load-sensitive pump, an oil cylinder control valve group, a load-sensitive multi-way valve and a hydraulic cylinder. The oil cylinder control valve group comprises a pressure type balance valve; an oil outlet of the load-sensitive pump is connected with an oil inlet of the load-sensitive multi-way valve through a first oil way, the load-sensitive multi-way valve is connected with a rod cavity and a rodless cavity of the hydraulic cylinder through a second oil way and a third oil way respectively, and the second oil way is connected with the rod cavity through the pressure type balance valve. A pressure type balance valve is arranged, so that the hydraulic cylinder is effectively prevented from shaking and crawling, and the service life of the hydraulic cylinder is effectively prolonged; by arranging the load-sensitive multi-way valve, cavitation and burning of a piston main seal in the hydraulic cylinder are effectively avoided, the service life of the hydraulic cylinder is effectively prolonged, meanwhile, the telescopic speed of the hydraulic cylinder can be effectively increased, and therefore the working efficiency of the whole machine is improved.

Description

Technical Field

[0001] The invention relates to the technical field of hydraulic cylinders, and in particular to a hydraulic system and a control method for a variable-luff tower crane. Background Art

[0002] At present, the tower crane hydraulic system on the market is generally a vertical jacking tower crane system. The hydraulic principle is relatively simple, mainly including a metering pump, a relief valve, a reversing valve, a hydraulic cylinder rodless chamber pressure-type balancing valve, and a rod chamber pressure-type balancing valve to realize the vertical lifting, lowering, and stopping of the hydraulic cylinder.

[0003] For the working conditions of luffing tower cranes, the hydraulic systems of conventional tower cranes are difficult to meet the actual working conditions and the main problems are as follows: 1. During the luffing process of the boom of the luffing tower crane, the pressure on the large chamber of the hydraulic cylinder changes drastically, and the lateral force on the hydraulic cylinder is relatively large, which makes it easier for the hydraulic cylinder to shake and creep, resulting in abnormal wear of the main seal of the hydraulic cylinder piston and reducing the life of the hydraulic cylinder; 2. Under loaded conditions, due to the rapid full-stroke recovery of the hydraulic cylinder and the lack of automatic deceleration function, the boom exerts a huge impact force on the mounting seat and the base structural parts at the moment it falls to the mounting seat, thereby reducing the service life of the mounting seat and the base structural parts; 3. The luffing tower crane has high-speed working conditions when it is unloaded and low-speed working conditions when it is heavily loaded, which are used to improve the working efficiency of the entire machine. The hydraulic system of the conventional tower crane does not have the function of automatically or manually realizing the speed change and extension of the hydraulic cylinder according to different loads. Summary of the invention

[0004] In view of this, the present invention provides a hydraulic system for a luffing tower crane, which can effectively extend the service life of the hydraulic cylinder, the mounting seat and the base structure, and at the same time, can also increase the extension and retraction speed of the hydraulic cylinder, thereby improving the working efficiency of the whole machine.

[0005] To achieve the above object, the present invention provides the following technical solutions: A hydraulic system of a luffing tower crane comprises an oil tank, a system controller, a motor, a load-sensitive pump, an oil cylinder control valve group, a load-sensitive multi-way valve and a hydraulic cylinder.

[0006] Among them, the oil tank is connected to the oil inlet of the load-sensitive pump, and the motor is electrically connected to the load-sensitive pump to drive the load-sensitive pump to operate; the cylinder control valve group includes a pressure-type balancing valve; the motor, the pressure-type balancing valve and the load-sensitive multi-way valve are all electrically connected to the system controller; the oil outlet of the load-sensitive pump is connected to the oil inlet of the load-sensitive multi-way valve through the first oil circuit, the load-sensitive multi-way valve is respectively connected to the rod chamber and the rodless chamber of the hydraulic cylinder through the second oil circuit and the third oil circuit, and the second oil circuit is connected to the rod chamber through the pressure-type balancing valve.

[0007] Preferably, the cylinder control valve group also includes a rod chamber safety valve and a rodless chamber safety valve, and the rod chamber safety valve and the rodless chamber safety valve are respectively arranged in parallel on the second oil circuit and the third oil circuit, and the second oil circuit and the third oil circuit are respectively connected to the oil tank through the rod chamber safety valve and the rodless chamber safety valve.

[0008] Preferably, the cylinder control valve group also includes a rod chamber pressure sensor and a rodless chamber pressure sensor, and the rod chamber pressure sensor and the rodless chamber pressure sensor are respectively arranged in the second oil circuit and the third oil circuit, and the rod chamber pressure sensor and the rodless chamber pressure sensor are both electrically connected to the system controller.

[0009] Preferably, the luffing tower crane hydraulic system also includes an electric proportional pilot balancing valve, which is arranged on the third oil circuit and located between the load-sensitive multi-way valve and the cylinder control valve group, and is electrically connected to the system controller.

[0010] Preferably, the hydraulic system of the luffing tower crane also includes a pilot control valve group, which includes a speed regulating valve, a pressure reducing valve and a relief valve. The oil outlet of the load-sensitive pump is also connected to the electric proportional pilot balancing valve through a fourth oil circuit. In the direction from the load-sensitive pump to the electric proportional pilot balancing valve, the speed regulating valve and the pressure reducing valve are sequentially arranged on the fourth oil circuit, and the relief valve is arranged in parallel on the fourth oil circuit. The pressure reducing valve and the relief valve are both connected to the oil tank, and the speed regulating valve, the pressure reducing valve and the relief valve are all electrically connected to the system controller.

[0011] Preferably, the luffing tower crane hydraulic system further includes a high-pressure filter, and the pilot control valve group further includes a one-way valve, and in the direction from the load-sensitive pump to the load-sensitive multi-way valve, the high-pressure filter and the one-way valve are sequentially arranged in the first oil circuit.

[0012] A control method for a hydraulic system of a luffing tower crane is applied to the hydraulic system of the luffing tower crane, and specifically includes the following contents: When the piston rod of the hydraulic cylinder extends, the system controller controls the load-sensitive pump to pump oil toward the rodless chamber of the hydraulic cylinder by driving the motor to move the hydraulic cylinder; when the piston rod of the hydraulic cylinder retracts, the system controller controls the load-sensitive pump to pump oil toward the rod chamber of the hydraulic cylinder by driving the motor to move the hydraulic cylinder.

[0013] Preferably, the control method of the hydraulic system of the luffing tower crane also includes the following content: when the crane is in a no-load condition and the piston rod of the hydraulic cylinder is extended, the system controller reduces the opening of the pressure-type balancing valve to generate a certain amount of back pressure in the rod chamber of the hydraulic cylinder, thereby increasing the driving pressure in the rodless chamber when the piston rod of the hydraulic cylinder is extended and the hydraulic stiffness in the third oil circuit.

[0014] Preferably, the control method of the hydraulic system of the luffing tower crane also includes the following contents: when the crane is in a loaded condition and the piston rod of the hydraulic cylinder is retracted, the system controller calculates the current pressure value in the rod chamber based on the pressure data fed back in real time by the rod chamber pressure sensor; if the pressure value is less than or equal to the pressure value preset in the system controller, the system controller increases the opening of the working oil port of the load-sensitive multi-way valve corresponding to the second oil circuit to replenish oil to the rod chamber of the hydraulic cylinder to prevent the rod chamber of the hydraulic cylinder from being sucked in or cavitated; at the same time, the system controller can also calculate the current angle or spacing between the boom and the mounting seat based on the angle data fed back in real time by the inclination sensor on the boom; when the angle or spacing reaches the angle or spacing preset in the system controller, the system controller can gradually reduce the opening of the electric proportional pilot balancing valve to achieve multi-stage speed reduction during hydraulic cylinder recovery, thereby enabling the hydraulic cylinder to be recovered according to a preset speed curve.

[0015] Preferably, the control method of the hydraulic system of the luffing tower crane also includes the following contents: when the crane is in a heavy-load condition, under the premise that the actual motor power is not overloaded, the system controller can calculate the maximum flow rate that the current load-sensitive pump can pump out based on the pressure data fed back in real time by the rod chamber pressure sensor and the rodless chamber pressure sensor; when the piston rod of the hydraulic cylinder extends, the system controller increases the opening of the working oil port of the load-sensitive multi-way valve corresponding to the third oil circuit according to the maximum flow rate to increase the extension speed of the piston rod; when the piston rod of the hydraulic cylinder retracts, the system controller increases the opening of the working oil port of the load-sensitive multi-way valve corresponding to the second oil circuit according to the maximum flow rate to increase the retraction speed of the piston rod.

[0016] Compared with the prior art, the hydraulic system of a luffing tower crane disclosed in the present application effectively avoids the shaking and creeping of the hydraulic cylinder and effectively prolongs the service life of the hydraulic cylinder by setting a pressure-type balancing valve; effectively avoids the cavitation and burning of the main seal of the piston in the hydraulic cylinder and effectively prolongs the service life of the hydraulic cylinder, and at the same time, can effectively improve the extension and retraction speed of the hydraulic cylinder, thereby improving the working efficiency of the whole machine; by setting an electric proportional pilot balancing valve to perform multi-stage deceleration on the recovery speed of the hydraulic cylinder, it avoids the huge impact of the boom on the mounting seat and the base structure at the moment of falling to the mounting seat, effectively protecting the safety of the mounting seat and the base structure and prolonging the service life.

[0017] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the hydraulic system of the luffing tower crane disclosed in the embodiment of the present application; Figure 2 This is the crane installation structure diagram.

[0019] Reference numerals: 1. Oil tank; 2. Motor; 3. Load-sensing pump; 4. Hydraulic cylinder; 5. Oil cylinder control valve group; 51. Pressure type balancing valve; 52. Safety valve for rod chamber; 53. Safety valve for rodless chamber; 54. Pressure sensor for rod chamber; 55. Pressure sensor for rodless chamber; 6. Pilot control valve group; 61. Speed ​​regulating valve; 62. Pressure reducing valve; 63. Overflow valve; 64. Check valve; 7. Load-sensitive multi-way valve; 8. Electric proportional pilot balance valve; 9. High-pressure filter; 10. First oil circuit; 20. Second oil circuit; 30. Third oil circuit; 40. Fourth oil circuit; 50. Lifting arm; 60. Inclination sensor; 70. Mounting seat; 80. Base structure. DETAILED DESCRIPTION

[0020] The present invention discloses a luffing tower crane hydraulic system, which can effectively extend the service life of a hydraulic cylinder 4, a mounting seat 70 and a base structure 80, and at the same time, can also increase the extension and retraction speed of the hydraulic cylinder 4, thereby improving the working efficiency of the whole machine.

[0021] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0022] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0023] Reference below Figure 1 and Figure 2The hydraulic system of a luffing tower crane in an embodiment of the present invention is described.

[0024] The embodiment of the present application discloses a hydraulic system for a luffing tower crane, comprising: an oil tank 1, a system controller, a motor 2, a load-sensitive pump 3, an oil cylinder control valve group 5, a load-sensitive multi-way valve 7 and a hydraulic cylinder 4.

[0025] Among them, the oil tank 1 is connected to the oil inlet of the load-sensitive pump 3, and the motor 2 is electrically connected to the load-sensitive pump 3 to drive the load-sensitive pump 3 to operate; the cylinder control valve group 5 includes a pressure-type balancing valve 51; the motor 2, the pressure-type balancing valve 51 and the load-sensitive multi-way valve 7 are all electrically connected to the system controller, and the system controller can control the operation of the motor 2 and the opening of the valve.

[0026] The oil outlet of the load-sensing pump 3 is connected to the oil inlet of the load-sensing multi-way valve 7 through the first oil circuit 10. The load-sensing multi-way valve 7 is connected to the rod chamber and the rodless chamber of the hydraulic cylinder 4 through the second oil circuit 20 and the third oil circuit 30 respectively. The second oil circuit 20 is connected to the rod chamber through the pressure-type balancing valve 51.

[0027] By setting the pressure-type balancing valve 51, the shaking and creeping of the hydraulic cylinder 4 are effectively avoided, and the service life of the hydraulic cylinder 4 is effectively extended; by setting the load-sensitive multi-way valve 7, the cavitation and burning of the main seal of the piston in the hydraulic cylinder 4 are effectively avoided, and the service life of the hydraulic cylinder 4 is effectively extended.

[0028] In this embodiment, when the crane is in a no-load condition and the piston rod of the hydraulic cylinder 4 is extended, the system controller can reduce the opening of the pressure-type balancing valve 51 to generate a certain amount of back pressure in the rod chamber of the hydraulic cylinder 4, thereby slightly increasing the driving pressure of the rodless chamber when the piston rod of the hydraulic cylinder 4 is extended. At the same time, the hydraulic stiffness of the oil circuit from the load-sensitive pump 3 to the rodless chamber of the hydraulic cylinder 4 is also increased. In this way, the problem of shaking and creeping of the hydraulic cylinder 4 under no-load conditions caused by the cylinder processing and manufacturing or structural parts manufacturing can be effectively solved, which in turn causes abnormal wear of the main piston seal of the hydraulic cylinder 4 and reduces the service life of the hydraulic cylinder 4.

[0029] In this embodiment, when the piston rod of the hydraulic cylinder 4 retracts, the system controller can increase the opening of the working oil port of the load-sensitive multi-way valve 7 corresponding to the second oil circuit 20 to increase the hydraulic oil flow rate entering the rod chamber through the second oil circuit 20, so as to avoid the problem that the oil in the rodless chamber of the hydraulic cylinder 4 flows back too quickly, resulting in the failure to replenish the oil in the rod chamber of the hydraulic cylinder 4 in time, which in turn causes cavitation and burning of the main seal of the piston of the hydraulic cylinder 4, thereby reducing the service life of the hydraulic cylinder 4.

[0030] In this embodiment, a pilot proportional pressure reducing valve 62 is integrated in the load-sensitive multi-way valve 7, and the system controller controls the opening of the two working oil ports of the load-sensitive multi-way valve 7 corresponding to the second oil circuit 20 and the third oil circuit 30 respectively by controlling the opening of the pilot proportional pressure reducing valve 62.

[0031] In some embodiments, for example Figure 1 As shown, the cylinder control valve group 5 also includes a rod chamber safety valve 52 and a rodless chamber safety valve 53. The rod chamber safety valve 52 and the rodless chamber safety valve 53 are respectively arranged in parallel on the second oil circuit 20 and the third oil circuit 30. The second oil circuit 20 and the third oil circuit 30 are respectively connected to the oil tank 1 through the rod chamber safety valve 52 and the rodless chamber safety valve 53.

[0032] In this embodiment, the rod chamber safety valve 52 and the rodless chamber safety valve 53 can respectively provide pressure overload protection for the rod chamber and the rodless chamber of the hydraulic cylinder 4. For example, when the pressure in the rod chamber is overloaded, the hydraulic oil in the rod chamber can flow back to the oil tank 1 through the rod chamber safety valve 52, thereby preventing the rod chamber from being damaged by excessive pressure.

[0033] In some embodiments, for example Figure 1 As shown, the cylinder control valve group 5 also includes a rod chamber pressure sensor 54 and a rodless chamber pressure sensor 55. The rod chamber pressure sensor 54 and the rodless chamber pressure sensor 55 are respectively arranged on the second oil circuit 20 and the third oil circuit 30. The rod chamber pressure sensor 54 and the rodless chamber pressure sensor 55 are both electrically connected to the system controller.

[0034] In this embodiment, the rod chamber pressure sensor 54 is used to detect the oil pressure in the rod chamber in real time, and feed back the acquired pressure data to the system controller. The rodless chamber pressure sensor 55 is used to detect the oil pressure in the rodless chamber in real time, and feed back the acquired pressure data to the system controller. The system controller can calculate the current pressure values ​​in the rod chamber and the rodless chamber according to the received rod chamber pressure data and the rodless chamber pressure data, and regulate the hydraulic system as a whole according to the pressure values ​​in the rod chamber and the rodless chamber. For example, when the piston rod of the hydraulic cylinder 4 retracts, if the pressure value of the rod chamber calculated by the system controller according to the received rod chamber pressure data is lower than the preset pressure value in the system controller, indicating that the current recovery speed of the hydraulic cylinder 4 is too fast, the system controller will increase the opening of the working oil port of the load-sensitive multi-way valve 7 corresponding to the second oil circuit 20 to increase the hydraulic oil flow entering the rod chamber through the second oil circuit 20, so as to replenish oil to the rod chamber and avoid cavitation and burning of the piston main seal of the hydraulic cylinder 4.

[0035] In some embodiments, for example Figure 1As shown, the hydraulic system of the luffing tower crane also includes an electric proportional pilot balancing valve 8, which is arranged on the third oil circuit 30 and located between the load-sensitive multi-way valve 7 and the cylinder control valve group 5. The electric proportional pilot balancing valve 8 is electrically connected to the system controller.

[0036] In this embodiment, when the pressure value of the rod chamber calculated by the system controller according to the received pressure data of the rod chamber is lower than the pressure value preset in the system controller, it means that the current recovery speed of the hydraulic cylinder 4 is too fast. If it is allowed to recover at the current recovery speed, the crane arm 50 will cause a huge impact force on the mounting seat 70 and the base structure 80 at the moment of falling on the mounting seat 70. In the long run, the service life of the mounting seat 70 and the base structure 80 will be seriously shortened; therefore, by arranging the electric proportional pilot balance valve 8 on the third oil circuit 30, the recovery speed of the hydraulic cylinder 4 can be decelerated. The specific process is as follows: The system controller calculates the current angle or distance between the crane arm 50 and the mounting seat 70 based on the angle data fed back in real time by the inclination sensor 60 on the crane arm 50. When the angle or distance reaches the angle or distance preset in the system controller, the system controller can reduce the opening of the electric proportional pilot balance valve 8 step by step to perform multi-stage deceleration on the recovery of the hydraulic cylinder 4, thereby enabling the hydraulic cylinder 4 to be recovered according to a preset speed curve, thereby avoiding a huge impact on the mounting seat 70 and the base structure 80 caused by the crane arm 50 at the moment of falling onto the mounting seat 70, thereby effectively protecting the safety of the mounting seat 70 and the base structure 80 and extending their service life.

[0037] In this embodiment, when the crane is in a heavy-load condition, under the premise that the actual power of the motor 2 is not overloaded, the system controller can calculate the maximum flow rate of hydraulic oil that can be pumped out by the current load-sensitive pump 3 based on the pressure data of the rod chamber and the rodless chamber fed back in real time by the rod chamber sensor and the rodless chamber sensor. Then, when the piston rod of the hydraulic cylinder 4 is extended or retracted, the system controller increases the opening of the working oil port of the load-sensitive multi-way valve 7 corresponding to the third oil circuit 30, or increases the opening of the working oil port of the load-sensitive multi-way valve 7 corresponding to the second oil circuit 20, according to the maximum flow rate, to increase the extension and retraction speed of the piston rod of the hydraulic cylinder 4, thereby improving the working efficiency of the entire machine.

[0038] In some embodiments, for example Figure 1As shown, the hydraulic system of the luffing tower crane also includes a pilot control valve group 6, which includes a speed regulating valve 61, a pressure reducing valve 62 and a relief valve 63. The oil outlet of the load-sensitive pump 3 is also connected to the electric proportional pilot balancing valve 8 through the fourth oil circuit 40. In the direction from the load-sensitive pump 3 to the electric proportional pilot balancing valve 8, the speed regulating valve 61 and the pressure reducing valve 62 are sequentially arranged on the fourth oil circuit 40, and the relief valve 63 is arranged in parallel on the fourth oil circuit 40. The pressure reducing valve 62 and the relief valve 63 are both connected to the oil tank 1, and the speed regulating valve 61, the pressure reducing valve 62 and the relief valve 63 are all electrically connected to the system controller.

[0039] In this embodiment, the pilot control valve group 6 is used to provide the electric proportional pilot balancing valve 8 with controllable pilot control oil with flow and pressure. Specifically, the system controller sets and limits the pilot control oil flow by controlling the speed regulating valve 61; the system controller sets the oil inlet pressure of the pilot port of the electric proportional pilot balancing valve 8 by controlling the pressure reducing valve 62. When the oil inlet pressure of the pilot port of the electric proportional pilot balancing valve 8 exceeds the set oil inlet pressure, the hydraulic oil can flow back to the oil tank 1 through the pressure reducing valve 62 to prevent excessive pressure from causing damage to the electric proportional pilot balancing valve 8; the overflow valve 63 can play a safety protection role when the pressure reducing valve 62 fails, to prevent the oil inlet pressure of the pilot port of the electric proportional pilot balancing valve 8 from being too high and causing damage to the electric proportional pilot balancing valve 8 itself.

[0040] In this embodiment, the hydraulic system of the luffing tower crane further includes a high-pressure filter 9, and the pilot control valve group 6 further includes a one-way valve 64. In the direction from the load-sensing pump 3 to the load-sensing multi-way valve 7, the high-pressure filter 9 and the one-way valve 64 are sequentially arranged on the first oil circuit 10. The high-pressure filter 9 can filter the hydraulic oil and remove impurities in the hydraulic oil, thereby ensuring the cleanliness and safety of the hydraulic oil; the setting of the one-way valve 64 can prevent the hydraulic oil in the first oil circuit 10 from flowing back.

[0041] In addition, the present application also discloses a control method for a hydraulic system of a luffing tower crane, which is applied to the hydraulic system of a luffing tower crane disclosed in the above embodiment, and specifically includes the following contents: When the piston rod of the hydraulic cylinder 4 extends outward, the system controller controls the load-sensitive pump 3 to pump oil toward the rodless chamber of the hydraulic cylinder 4 by driving the motor 2, so that the hydraulic cylinder 4 moves; when the piston rod of the hydraulic cylinder 4 retracts, the system controller controls the load-sensitive pump 3 to pump oil toward the rod chamber of the hydraulic cylinder 4 by driving the motor 2, so that the hydraulic cylinder 4 moves.

[0042] In some embodiments, when the crane is in a no-load condition and the piston rod of the hydraulic cylinder 4 is extended, the system controller reduces the opening of the pressure-type balancing valve 51 to generate a certain amount of back pressure in the rod chamber of the hydraulic cylinder 4, thereby increasing the driving pressure in the rodless chamber when the piston rod of the hydraulic cylinder 4 is extended and the hydraulic stiffness in the third oil circuit 30. In this way, the problem of shaking and creeping of the hydraulic cylinder 4 caused by cylinder processing and manufacturing or structural parts manufacturing under no-load conditions can be effectively solved, which in turn causes abnormal wear of the main piston seal of the hydraulic cylinder 4 and reduces the service life of the hydraulic cylinder 4.

[0043] In some embodiments, when the crane is in a loaded working condition and the piston rod of the hydraulic cylinder 4 is retracted, the system controller calculates the current pressure value in the rod cavity according to the pressure data fed back in real time by the rod cavity pressure sensor 54. If the pressure value is less than or equal to the pressure value preset in the system controller, the system controller increases the opening of the working oil port of the load-sensitive multi-way valve 7 corresponding to the second oil circuit 20 to replenish oil to the rod cavity of the hydraulic cylinder 4 to prevent the rod cavity of the hydraulic cylinder 4 from being sucked in and cavitated. At the same time, the system controller can also calculate the pressure value in the rod cavity according to the inclination sensor 60 on the crane arm 50. The angle data fed back during operation is used to calculate the current angle or distance between the lifting arm 50 and the mounting seat 70. When the angle or distance reaches the angle or distance preset in the system controller, the system controller can gradually reduce the opening of the electric proportional pilot balance valve 8 to achieve multi-stage speed reduction when the hydraulic cylinder 4 is recovered, thereby enabling the hydraulic cylinder 4 to be recovered according to a preset speed curve, thereby preventing the lifting arm 50 from causing a huge impact on the mounting seat 70 and the base structure 80 at the moment of falling onto the mounting seat 70, thereby effectively protecting the safety of the mounting seat 70 and the base structure 80 and extending their service life.

[0044] In some embodiments, when the crane is in a heavy-load condition, under the premise that the actual power of the motor 2 is not overloaded, the system controller can calculate the maximum flow rate that the current load-sensitive pump 3 can pump out based on the pressure data fed back in real time by the rod chamber pressure sensor 54 and the rodless chamber pressure sensor 55; when the piston rod of the hydraulic cylinder 4 extends, the system controller increases the opening of the working oil port of the load-sensitive multi-way valve 7 corresponding to the third oil circuit 30 according to the maximum flow rate to increase the extension speed of the piston rod; when the piston rod of the hydraulic cylinder 4 retracts, the system controller increases the opening of the working oil port of the load-sensitive multi-way valve 7 corresponding to the second oil circuit 20 according to the maximum flow rate to increase the retraction speed of the piston rod.

[0045] In this embodiment, when the crane is in a heavy-load condition, the hydraulic system is adjusted by using the above control method, so that the extension and retraction speed of the hydraulic cylinder 4 can be effectively improved, thereby effectively improving the working efficiency of the whole machine.

[0046] Other structures and operations of the hydraulic system and control method of the luffing tower crane according to the embodiment of the present invention are well known to those skilled in the art and will not be described in detail here.

[0047] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0048] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A hydraulic system for a luffing tower crane, characterized in that: include: Fuel tank, system controller, motor, load sensing pump, cylinder control valve group, load sensing multi-way valve and hydraulic cylinder; The oil tank is connected to the oil inlet of the load-sensitive pump, and the motor is electrically connected to the load-sensitive pump to drive the load-sensitive pump to operate; the oil cylinder control valve group includes a pressure-type balancing valve; the motor, the pressure-type balancing valve and the load-sensitive multi-way valve are all electrically connected to the system controller; The oil outlet of the load-sensitive pump is connected to the oil inlet of the load-sensitive multi-way valve through the first oil circuit. The load-sensitive multi-way valve is connected to the rod chamber and the rodless chamber of the hydraulic cylinder through the second oil circuit and the third oil circuit respectively. The second oil circuit is connected to the rod chamber through the pressure-type balancing valve.

2. The hydraulic system of a luffing tower crane according to claim 1, characterized in that: The cylinder control valve group also includes a rod chamber safety valve and a rodless chamber safety valve, and the rod chamber safety valve and the rodless chamber safety valve are respectively arranged in parallel in the second oil circuit and the third oil circuit, and the second oil circuit and the third oil circuit are respectively connected to the oil tank through the rod chamber safety valve and the rodless chamber safety valve.

3. The hydraulic system of a luffing tower crane according to claim 1, characterized in that: The cylinder control valve group also includes a rod chamber pressure sensor and a rodless chamber pressure sensor, which are respectively arranged in the second oil circuit and the third oil circuit, and the rod chamber pressure sensor and the rodless chamber pressure sensor are both electrically connected to the system controller.

4. The hydraulic system of a luffing tower crane according to claim 1, characterized in that: It also includes an electric proportional pilot balancing valve, which is arranged on the third oil circuit and located between the load-sensitive multi-way valve and the cylinder control valve group. The electric proportional pilot balancing valve is electrically connected to the system controller.

5. The hydraulic system of a luffing tower crane according to claim 4, characterized in that: It also includes a pilot control valve group, which includes a speed regulating valve, a pressure reducing valve and a relief valve. The oil outlet of the load sensitive pump is also connected to the electric proportional pilot balancing valve through a fourth oil circuit. In the direction from the load sensitive pump to the electric proportional pilot balancing valve, the speed regulating valve and the pressure reducing valve are sequentially arranged on the fourth oil circuit, and the relief valve is arranged in parallel on the fourth oil circuit. The pressure reducing valve and the relief valve are both connected to the oil tank, and the speed regulating valve, the pressure reducing valve and the relief valve are all electrically connected to the system controller.

6. The hydraulic system of a luffing tower crane according to claim 5, characterized in that: It also includes a high-pressure filter, and the pilot control valve group also includes a one-way valve. In the direction from the load-sensitive pump to the load-sensitive multi-way valve, the high-pressure filter and the one-way valve are sequentially arranged on the first oil circuit.

7. A control method for a hydraulic system of a luffing tower crane, characterized in that: The hydraulic system applied to the above-mentioned luffing tower crane specifically includes the following contents: When the piston rod of the hydraulic cylinder extends outward, the system controller controls the load-sensing pump to pump oil toward the rodless cavity of the hydraulic cylinder through the drive motor to make the hydraulic cylinder move; When the piston rod of the hydraulic cylinder retracts, the system controller controls the load sensing pump to pump oil toward the rod chamber of the hydraulic cylinder by driving the motor to activate the hydraulic cylinder.

8. The control method of the hydraulic system of a luffing tower crane according to claim 7, characterized in that: Also includes the following: When the crane is in a no-load condition and the piston rod of the hydraulic cylinder is extended, the system controller reduces the opening of the pressure-type balancing valve to generate a certain amount of back pressure in the rod chamber of the hydraulic cylinder, thereby increasing the driving pressure in the rodless chamber when the piston rod of the hydraulic cylinder is extended and the hydraulic stiffness in the third oil circuit.

9. The control method of the hydraulic system of a luffing tower crane according to claim 7, characterized in that: Also includes the following: When the crane is in a loaded working condition and the piston rod of the hydraulic cylinder is retracted, the system controller calculates the current pressure value in the rod cavity based on the pressure data fed back by the rod cavity pressure sensor in real time. If the pressure value is less than or equal to the preset pressure value in the system controller, the system controller increases the opening of the working oil port of the load-sensitive multi-way valve corresponding to the second oil circuit to replenish oil to the rod cavity of the hydraulic cylinder to prevent the rod cavity of the hydraulic cylinder from sucking air and cavitation. At the same time, the system controller can also calculate the current angle or distance between the boom and the mounting base based on the angle data fed back in real time by the inclination sensor on the boom. When the angle or distance reaches the angle or distance preset in the system controller, the system controller can gradually reduce the opening of the electric proportional pilot balancing valve to achieve multi-stage speed reduction during hydraulic cylinder recovery, thereby enabling the hydraulic cylinder to be recovered according to a preset speed curve.

10. The control method of the hydraulic system of a luffing tower crane according to claim 7, characterized in that: Also includes the following: When the crane is in a heavy-load condition, under the premise that the actual motor power is not overloaded, the system controller can calculate the maximum flow rate that the current load-sensitive pump can pump out based on the pressure data fed back in real time by the rod cavity pressure sensor and the rodless cavity pressure sensor; When the piston rod of the hydraulic cylinder extends outward, the system controller increases the opening of the working oil port of the load-sensitive multi-way valve corresponding to the third oil circuit according to the maximum flow rate to increase the extension speed of the piston rod; When the piston rod of the hydraulic cylinder retracts, the system controller increases the opening of the working oil port of the load-sensitive multi-way valve corresponding to the second oil circuit according to the maximum flow rate to increase the retraction speed of the piston rod.

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