Aerial work platform and hydraulic leveling system and method thereof

Abstract

The invention discloses an aerial work platform and a hydraulic leveling system and method thereof, and relates to the technical field of hydraulic control. The system comprises a variable-amplitude loop, a leveling loop and a pressurizing loop, the pressurizing loop comprises a reversing valve and a safety valve, a first port of the reversing valve is connected with the safety valve, a second port of the reversing valve is connected to a pipeline between a second port of a second bidirectional balance valve and a rodless cavity of a first leveling oil cylinder, and a third port of the reversing valve is connected to a pipeline between a second port of a second bidirectional balance valve and a rodless cavity of a second leveling oil cylinder. A third port of the reversing valve is connected to a pipeline between a third port of the second bidirectional balance valve and a rod cavity of the first leveling oil cylinder, and the safety valve is further connected to a pipeline between the first electromagnetic reversing valve and an arm support oil way. According to the invention, the leveling loop is pressurized at one side, so that the problem of leveling lag is solved, the oil return back pressure is prevented from rising in the leveling process of the aerial work platform, and the energy loss of the system is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of hydraulic control, and in particular relates to an aerial work platform and a hydraulic leveling system and method thereof. Background Art

[0002] When the boom of the aerial work platform is luffing, the pressurized oil flows from the boom oil circuit through the electromagnetic reversing valve and the luffing rodless chamber balancing valve into the rodless chamber of the luffing cylinder, causing the luffing cylinder to extend and push the boom upward, and the boom pulls the lower leveling cylinder to extend. At this time, the oil pressure in the rod chamber of the lower leveling cylinder increases and enters the rod chamber of the upper leveling cylinder. When the oil pressure in the rod chamber of the lower leveling cylinder increases to the preset pilot pressure value of the rodless chamber balancing valve of the upper leveling cylinder, the rodless chamber balancing valve of the upper leveling cylinder opens, and the upper leveling cylinder retracts to keep the aerial work platform always level. During the process of the oil pressure in the rod chamber of the lower leveling cylinder increasing to the preset pilot pressure value of the rodless chamber balancing valve of the upper leveling cylinder, the upper leveling cylinder is in a stationary state, resulting in a delay in the leveling of the aerial work platform during the luffing process.

[0003] When the boom of the aerial work platform is luffing down, the pressurized oil flows from the boom oil circuit through the electromagnetic reversing valve and the luffing rod chamber balancing valve into the rod chamber of the luffing cylinder, causing the luffing cylinder to retract and pull the boom downward, and the boom pushes the lower leveling cylinder to retract. At this time, the oil pressure in the rodless chamber of the lower leveling cylinder increases and enters the rodless chamber of the upper leveling cylinder. When the oil pressure in the rodless chamber of the lower leveling cylinder increases to the preset pilot pressure value of the rod chamber balancing valve of the upper leveling cylinder, the rod chamber balancing valve of the upper leveling cylinder opens, and the upper leveling cylinder extends out to keep the aerial work platform always level. During the process of the oil pressure in the rodless chamber of the lower leveling cylinder increasing to the preset pilot pressure value of the rod chamber balancing valve of the upper leveling cylinder, the upper leveling cylinder is in a stationary state, resulting in a delay in the leveling of the aerial work platform during the luffing process of the boom.

[0004] At the same time, the changes in oil pressure in the rodless chamber and the rod chamber of the leveling circuit caused by the up and down movements of the boom will cause changes in the oil compression inside the cylinder and the oil pipe. The change in oil compression will cause the volume of the leveling circuit to change. Coupled with the volume change caused by the volume expansion of the oil pipe itself and other factors, they together lead to leveling lag during the boom movement of the aerial work platform.

[0005] At present, the technical solutions to solve the problem of leveling lag of aerial work platforms are: using sensors and separate leveling controllers to solve the problem of leveling lag, adding a flow control valve before the reversing valve of the leveling circuit, or simultaneously charging both ends of the rodless chamber and the rod chamber of the leveling cylinder to solve the problem of leveling lag. These solutions have the following defects: (1) Not energy-efficient and economical: The use of sensors and a separate leveling controller increases the difficulty of program control, and also increases production and maintenance costs. The scheme of simultaneously charging both ends of the rodless chamber and the rod chamber of the leveling cylinder will increase the return oil back pressure during the platform leveling process, and the leveling circuit is always in a pressurized state when the main circuit is working, which increases the energy loss of the system. (2) Not universal: Pressurizing both ends of the rodless and rod chambers of the leveling cylinder at the same time can only be used in the leveling circuit of the atmospheric balance valve or the single oil return balance valve. If the oil return balance valve is used, the return oil back pressure will increase due to the simultaneous pressurization of both ends of the rodless and rod chambers of the leveling cylinder, which will cause the leveling balance valve to fail to open normally. When the leveling balance valve fails to open normally, the hysteresis will be more serious, resulting in greater safety risks; (3) The existing technology has certain limitations in solving the leveling lag problem. It does not take into account the impact of factors such as the compression of hydraulic oil and the volume change caused by pipeline expansion during the leveling process on the leveling lag. Summary of the invention

[0006] The object of the present invention is to provide an aerial work platform and its hydraulic leveling system and method to solve at least one of the problems of simultaneously pressurizing both ends of the rodless chamber and the rod chamber of the leveling cylinder, resulting in increased return oil back pressure, increased system energy loss, and failure to consider the impact of hydraulic oil compression and pipeline volume changes.

[0007] The present invention solves the above technical problems through the following technical solutions: A hydraulic leveling system for an aerial work platform, comprising a luffing circuit, a leveling circuit and a charging circuit; the luffing circuit comprises a first electromagnetic reversing valve, a first two-way balancing valve and a luffing oil cylinder, the first port and the fourth port of the first electromagnetic reversing valve are respectively connected to the boom oil circuit, the second port and the third port of the first electromagnetic reversing valve are respectively connected to the first port and the fourth port of the first two-way balancing valve, the second port and the third port of the first two-way balancing valve are respectively connected to the rodless chamber and the rod chamber of the luffing oil cylinder; the leveling circuit comprises a second two-way balancing valve, a third two-way balancing valve, a first leveling oil cylinder and a second leveling oil cylinder, the first port and the fourth port of the second two-way balancing valve are respectively connected to the boom oil circuit, the second port of the second two-way balancing valve is connected to the rodless chamber of the first leveling oil cylinder and the first port of the third two-way balancing valve, the third port of the second two-way balancing valve is connected to the rod chamber of the first leveling oil cylinder and the fourth port of the third two-way balancing valve, the second port and the third port of the third two-way balancing valve are respectively connected to the rodless chamber and the rod chamber of the second leveling oil cylinder; The charging circuit includes a reversing valve and a safety valve, the first port of the reversing valve is connected to the safety valve, the second port of the reversing valve is connected to the pipeline between the second port of the second two-way balancing valve and the rodless chamber of the first leveling cylinder, the third port of the reversing valve is connected to the pipeline between the third port of the second two-way balancing valve and the rod chamber of the first leveling cylinder, and the safety valve is also connected to the pipeline between the first electromagnetic reversing valve and the arm oil circuit.

[0008] Furthermore, the reversing valve is a hydraulically controlled reversing valve or a second electromagnetic reversing valve; When the reversing valve is a hydraulically controlled reversing valve, the first control port of the hydraulically controlled reversing valve is also connected to the pipeline between the second port of the first electromagnetic reversing valve and the first port of the first two-way balancing valve, and the second control port of the hydraulically controlled reversing valve is also connected to the pipeline between the third port of the first electromagnetic reversing valve and the fourth port of the first two-way balancing valve.

[0009] Further, the safety valve is a pressure cut-off valve, a pressure reducing valve or a pressure reducing relief valve; When the safety valve is a pressure cut-off valve or a pressure reducing valve, the second port of the pressure cut-off valve or the pressure reducing valve is connected to the pipeline between the first port of the first electromagnetic reversing valve and the boom oil circuit; When the safety valve is a pressure reducing relief valve, the second port of the pressure reducing relief valve is connected to the pipeline between the first port of the first electromagnetic reversing valve and the arm oil circuit, and the third port of the pressure reducing relief valve is connected to the pipeline between the fourth port of the first electromagnetic reversing valve and the arm oil circuit.

[0010] Further, the first two-way balancing valve includes a first damper and a second damper, and the first damper and the second damper are arranged between the first port and the fourth port of the first two-way balancing valve.

[0011] Furthermore, a filter is provided on the pipeline between the first electromagnetic reversing valve and the boom oil circuit.

[0012] Based on the same concept, the present invention also provides an aerial work platform, which includes the hydraulic leveling system as described above.

[0013] Based on the same concept, the present invention also provides a hydraulic leveling method, which is applied to the hydraulic leveling system as described above, and the hydraulic leveling method comprises: When the boom is luffed, the hydraulic oil enters the rodless chamber of the luffing cylinder from the boom oil circuit through the first electromagnetic reversing valve and the first two-way balancing valve, so that the luffing cylinder extends to push the boom upward, and the boom pulls the first leveling cylinder to extend. At this time, the oil pressure in the rod chamber of the first leveling cylinder increases and enters the rod chamber of the second leveling cylinder; at the same time, after the hydraulic oil is reduced to a preset pressure through the safety valve from the boom oil circuit, it is pressurized into the rod chamber of the first leveling cylinder through the reversing valve, so that the oil pressure in the rod chamber of the first leveling cylinder quickly reaches the preset pilot pressure of the third two-way balancing valve; when the oil pressure in the rod chamber of the first leveling cylinder reaches the preset pilot pressure of the third two-way balancing valve, the second leveling cylinder retracts, so that the aerial work platform always remains level; When the boom is luffed down, the hydraulic oil enters the rod chamber of the luffing cylinder from the boom oil circuit through the first electromagnetic reversing valve and the first two-way balancing valve, so that the luffing cylinder retracts and pulls the boom downward, and the boom pushes the first leveling cylinder to retract. At this time, the oil pressure in the rodless chamber of the first leveling cylinder increases and enters the rodless chamber of the second leveling cylinder; at the same time, the hydraulic oil is reduced to a preset pressure from the boom oil circuit through the safety valve, and then pressurized into the rodless chamber of the first leveling cylinder through the reversing valve, so that the oil pressure in the rodless chamber of the first leveling cylinder quickly reaches the preset pilot pressure of the third two-way balancing valve; when the oil pressure in the rodless chamber of the first leveling cylinder reaches the preset pilot pressure of the third two-way balancing valve, the second leveling cylinder extends to keep the aerial work platform always level.

[0014] Furthermore, the theoretical calculation formula for the preset pressure of the safety valve is: ; , ; in, Indicates the theoretical value of the preset pressure of the safety valve. represents the bulk modulus of the oil, Indicates the amount of oil compression, Indicates the volume change of the pipeline between the first leveling cylinder and the second leveling cylinder. It represents the initial oil volume in the first leveling cylinder, the second leveling cylinder and the pipeline between the first leveling cylinder and the second leveling cylinder. Indicates the pressure change value in the leveling circuit. Indicates the volume expansion value of the pipeline between the first leveling cylinder and the second leveling cylinder. Indicates the length of the pipeline between the first leveling cylinder and the second leveling cylinder. Beneficial effects:

[0015] Compared with the prior art, the advantages of the present invention are: The present invention takes hydraulic oil from the boom length variation circuit through a pressure charging circuit to charge one side of the first leveling cylinder. When the first leveling cylinder extends (or the second leveling cylinder retracts), the rod chamber of the first leveling cylinder is pressurized; when the first leveling cylinder retracts (or the second leveling cylinder extends), the rodless chamber of the first leveling cylinder is pressurized, thereby improving the leveling lag problem and avoiding the increase in return oil back pressure during the leveling process of the aerial work platform. The leveling cylinder pressure charging and boom length variation are linked, so that the pressure charging circuit only works when the boom length varies, thereby reducing system energy loss.

[0016] The present invention designs the preset pressure of the safety valve by calculating the volume change caused by the compression of the hydraulic oil and the expansion of the pipeline during the leveling process, realizes the correction of the charging pressure, improves the accuracy of the leveling charging, avoids the influence of factors such as the compression of the hydraulic oil and the volume change caused by the expansion of the pipeline during the leveling process on the leveling lag, and further improves the leveling lag problem.

[0017] In order to solve the problem that the abnormal increase of leveling pressure in the traditional system causes damage to the oil cylinder, mounting platform, boom and other structural parts, the existing technology (publication number CN119568968A) uses a pressure sensor to detect the high pressure situation, and controls the amplitude change action and the electromagnetic unloading valve to be energized, and timely unloads the pressure to avoid damage to the oil cylinder, mounting platform, boom and other structural parts. Compared with the existing technology, the present invention is used to solve the problem of lag in the traditional hydraulic leveling system. The present invention adds a charging circuit between the amplitude change circuit and the leveling circuit, and takes hydraulic oil from the amplitude change circuit through the charging circuit to charge the first leveling oil cylinder, thereby improving the leveling lag problem. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only one embodiment of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 is a schematic diagram of a hydraulic leveling system in Embodiment 1 of the present invention; Figure 2 It is a schematic diagram of the hydraulic leveling system in the second embodiment of the present invention.

[0020] Explanation of the reference numerals: 1-amplitude-changing circuit, 11-first electromagnetic reversing valve, 12-first two-way balancing valve, 13-amplitude-changing cylinder, 2-leveling circuit, 21-second two-way balancing valve, 22-first leveling cylinder, 23-third two-way balancing valve, 24-second leveling cylinder, 3-charging circuit, 31-hydraulic-controlled reversing valve, 32-safety valve, 33-second electromagnetic reversing valve. DETAILED DESCRIPTION

[0021] The following is a clear and complete description of the technical solutions in the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] The technical solution of the present application is described in detail with specific embodiments below. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0023] Embodiment 1 In order to solve the problem of delayed leveling of the aerial work platform, the existing technology usually adopts the method of simultaneously charging the rodless chamber and the rod chamber of the leveling cylinder to speed up the oil pressure of the lower leveling cylinder (i.e., the first leveling cylinder 22) to the preset pilot pressure value of the upper leveling cylinder balance valve (i.e., the third two-way balance valve 23). This method will cause the return oil back pressure to increase and the system energy loss to increase.

[0024] In order to solve the above technical problems, an embodiment of the present invention provides a hydraulic leveling system. Figure 1 As shown, the hydraulic leveling system includes a luffing circuit 1, a leveling circuit 2 and a charging circuit 3; the luffing circuit 1 includes a first electromagnetic reversing valve 11, a first two-way balancing valve 12 and a luffing oil cylinder 13, the first port and the fourth port of the first electromagnetic reversing valve 11 are respectively connected to the boom oil circuit, the second port and the third port of the first electromagnetic reversing valve 11 are respectively connected to the first port and the fourth port of the first two-way balancing valve 12, and the second port and the third port of the first two-way balancing valve 12 are respectively connected to the rodless chamber and the rod chamber of the luffing oil cylinder 13; The leveling circuit 2 includes a second two-way balancing valve 21, a third two-way balancing valve 23, a first leveling oil cylinder 22 and a second leveling oil cylinder 24 (i.e., an upper leveling oil cylinder). The first port and the fourth port of the second two-way balancing valve 21 are respectively connected to the boom oil circuit, the second port of the second two-way balancing valve 21 is connected to the rodless chamber of the first leveling oil cylinder 22 and the first port of the third two-way balancing valve 23, the third port of the second two-way balancing valve 21 is connected to the rod chamber of the first leveling oil cylinder 22 and the fourth port of the third two-way balancing valve 23, and the second port and the third port of the third two-way balancing valve 23 are respectively connected to the rodless chamber and the rod chamber of the second leveling oil cylinder 24; The charging circuit 3 includes a hydraulically controlled reversing valve 31 and a safety valve 32. The first port of the hydraulically controlled reversing valve 31 is connected to the first port of the safety valve 32. The second port of the hydraulically controlled reversing valve 31 is connected to the pipeline between the second port of the second two-way balancing valve 21 and the rodless chamber of the first leveling cylinder 22. The third port of the hydraulically controlled reversing valve 31 is connected to the pipeline between the third port of the second two-way balancing valve 21 and the rod chamber of the first leveling cylinder 22. The first control port of the hydraulically controlled reversing valve 31 is also connected to the pipeline between the second port of the first solenoid reversing valve 11 and the first port of the first two-way balancing valve 12. The second control port of the hydraulically controlled reversing valve 31 is also connected to the pipeline between the third port of the first solenoid reversing valve 11 and the fourth port of the first two-way balancing valve 12. The safety valve 32 is also connected to the pipeline between the first solenoid reversing valve 11 and the arm oil circuit.

[0025] The hydraulic leveling process of the hydraulic leveling system of the present invention includes: When the boom of the aerial work platform is luffed, the hydraulic oil enters the rodless chamber of the luffing cylinder 13 from the oil outlet C of the boom oil circuit through the first electromagnetic reversing valve 11 (coil DT1 is energized) and the first two-way balancing valve 12, so that the luffing cylinder 13 extends to push the boom upward, and the boom pulls the first leveling cylinder 22 (i.e., the lower leveling cylinder) to extend. At this time, the oil pressure in the rod chamber of the first leveling cylinder 22 increases and enters the rod chamber of the second leveling cylinder 24 (i.e., the upper leveling cylinder); at the same time, the control oil is taken from the luffing circuit 1 to the first control port of the hydraulic control reversing valve 31, so that the hydraulic control reversing valve 31 is switched from the middle position to Y1. After the hydraulic oil is reduced to a preset pressure through the safety valve 32 from the outlet C of the boom oil circuit, the rod chamber of the first leveling cylinder 22 is pressurized through the hydraulically controlled reversing valve 31, so that the oil pressure in the rod chamber of the first leveling cylinder 22 quickly reaches the preset pilot pressure of the third two-way balancing valve 23 (that is, the balancing valve in the third two-way balancing valve 23 corresponding to the rodless chamber of the second leveling cylinder 24), thereby solving the problem of leveling lag; when the oil pressure in the rod chamber of the first leveling cylinder 22 reaches the preset pilot pressure of the third two-way balancing valve 23, the second leveling cylinder 24 retracts, so that the aerial work platform always remains level.

[0026] When the boom of the aerial work platform is luffed down, the hydraulic oil enters the rod chamber of the luffing cylinder 13 from the oil outlet D of the boom oil circuit through the first electromagnetic reversing valve 11 (coil DT2 is energized) and the first two-way balancing valve 12, so that the luffing cylinder 13 retracts and pulls the boom downward, and the boom pushes the first leveling cylinder 22 to retract. At this time, the oil pressure in the rodless chamber of the first leveling cylinder 22 increases and enters the rodless chamber of the second leveling cylinder 24; at the same time, the control oil is taken from the luffing circuit 1 to the second control port of the hydraulic control reversing valve 31, so that the hydraulic control reversing valve 31 is switched from the middle position to the Y2 position, and the hydraulic oil is discharged from the boom. After the oil outlet C of the oil circuit is reduced in pressure to a preset pressure through the safety valve 32, the rodless chamber of the first leveling cylinder 22 is pressurized through the hydraulically controlled reversing valve 31, so that the oil pressure in the rodless chamber of the first leveling cylinder 22 quickly reaches the preset pilot pressure of the third two-way balancing valve 23 (that is, the balancing valve in the third two-way balancing valve 23 corresponding to the rod chamber of the second leveling cylinder 24), thereby solving the problem of leveling lag; when the oil pressure in the rodless chamber of the first leveling cylinder 22 reaches the preset pilot pressure of the third two-way balancing valve 23, the second leveling cylinder 24 extends out, so that the aerial work platform always remains level.

[0027] The present invention draws hydraulic oil from the luffing circuit 1 through the charging circuit 3 to perform unilateral pressurization on the first leveling cylinder 22, thereby avoiding the problem of increased return oil back pressure during the leveling process; then the control oil is drawn from the luffing circuit 1 to the hydraulically controlled reversing valve 31, and when the boom is luffed up, the rod chamber of the leveling circuit 2 is pressurized; when the boom is luffed down, the rodless chamber of the leveling circuit 2 is pressurized, thereby realizing the linkage between the charging of the leveling circuit 2 and the luffing of the boom, and the charging circuit 3 only works when the boom is luffed, thereby reducing the energy loss of the system.

[0028] In a specific embodiment of the present invention, the safety valve 32 is a pressure cut-off valve, a pressure reducing valve or a pressure reducing relief valve, which avoids the problem that the pressure after the overflow affects the amplitude adjustment pressure due to the traditional pressure charging circuit being a relief valve.

[0029] When the safety valve 32 is a pressure cut-off valve or a pressure reducing valve, the second port of the pressure cut-off valve or the pressure reducing valve is connected to the pipeline between the first port of the first electromagnetic reversing valve 11 and the boom oil circuit, such as Figure 1 As shown; when the safety valve 32 is a pressure reducing relief valve, the second port of the pressure reducing relief valve is connected to the pipeline between the first port of the first electromagnetic reversing valve 11 and the boom oil circuit, and the third port of the pressure reducing relief valve is connected to the pipeline between the fourth port of the first electromagnetic reversing valve 11 and the boom oil circuit, as shown Figure 2 shown.

[0030] The changes in oil pressure in the rodless chamber and rod chamber of the leveling circuit 2 caused by the up and down movement of the boom will cause changes in the oil compression in the leveling cylinder and the pipeline. The changes in oil compression will cause the volume of the leveling circuit 2 to change. In addition, the volume changes caused by the volume expansion of the pipeline itself will cause leveling lag during the boom of the aerial work platform. In order to solve the problem of leveling lag caused by the volume changes caused by the changes in oil compression and the volume expansion of the pipeline, the present invention designs the preset pressure of the safety valve 32 by calculating the volume changes caused by the hydraulic oil compression and the expansion of the pipeline during the leveling process. The specific calculation formula is: (1) (2) (3) in, Indicates the preset pressure theoretical value of the safety valve 32, represents the bulk modulus of the oil, Indicates the amount of oil compression, represents the volume change of the pipeline between the first leveling cylinder 22 and the second leveling cylinder 24, represents the initial oil volume in the first leveling cylinder 22, the second leveling cylinder 24, and the pipeline between the first leveling cylinder 22 and the second leveling cylinder 24, Indicates the pressure change value in leveling circuit 2 (i.e. the pressure difference before and after charging). Indicates the volume expansion value of the pipeline between the first leveling cylinder 22 and the second leveling cylinder 24, Indicates the length of the pipeline between the first leveling cylinder 22 and the second leveling cylinder 24.

[0031] The actual value of the preset pressure of the safety valve 32 can be obtained by verifying and fine-tuning the preset pressure theoretical value of the safety valve 32. The preset pressure of the safety valve 32 is less than the preset pilot pressure of the third two-way balancing valve 23. When the amplitude variation pressure exceeds the preset pressure of the safety valve 32, the safety valve 32 is reversed, that is, the charging pressure entering the leveling circuit 2 is always less than the preset pilot pressure of the third two-way balancing valve 23, which solves the influence of the amplitude variation pressure on the leveling circuit 2 during the normal amplitude variation process.

[0032] In a specific embodiment of the present invention, the first two-way balancing valve 12 includes a first damper and a second damper, and the first damper and the second damper are arranged between the first port and the fourth port of the first two-way balancing valve 12. The first damper and the second damper of the first two-way balancing valve 12 form a pressure-dividing bridge with the pilot oil passage of the first two-way balancing valve 12, thereby reducing the pilot ratio of the entire first two-way balancing valve 12. The first damper and the second damper in the first two-way balancing valve 12 can be replaced with dampers of different sizes, such as 0.5mm, 0.6mm, and 0.7mm. The flow rate of the pressure-dividing bypass oil passage of the first two-way balancing valve 12 is changed by dampers of different sizes to adapt to actions with different speed requirements.

[0033] In a specific embodiment of the present invention, a filter is provided on the pipeline between the first electromagnetic reversing valve 11 and the boom oil circuit to filter out impurities in the hydraulic oil.

[0034] The hydraulic leveling system of the present invention has a wide range of applications and low overall cost. By calculating the volume change of the volume chamber of the leveling circuit 2, the charging is more accurate and more effective, and the leveling lag problem is effectively solved, so that the aerial work platform always remains level during the amplitude change process; the charging circuit 3 is linked with the amplitude change circuit 1 to perform unilateral pressurization of the leveling circuit 2, avoiding the safety hazard caused by the increase of back pressure on the return oil side during the leveling process, and enhancing the safety of the aerial work platform operator. Compared with the traditional leveling system, the present invention realizes energy saving of the hydraulic system and can effectively improve the endurance time of the whole machine.

[0035] Embodiment 2 like Figure 2 As shown, the hydraulic leveling system includes a luffing circuit 1, a leveling circuit 2 and a charging circuit 3; the luffing circuit 1 includes a first electromagnetic reversing valve 11, a first two-way balancing valve 12 and a luffing oil cylinder 13, the first port and the fourth port of the first electromagnetic reversing valve 11 are respectively connected to the boom oil circuit, the second port and the third port of the first electromagnetic reversing valve 11 are respectively connected to the first port and the fourth port of the first two-way balancing valve 12, and the second port and the third port of the first two-way balancing valve 12 are respectively connected to the rodless chamber and the rod chamber of the luffing oil cylinder 13; The leveling circuit 2 includes a second two-way balancing valve 21, a third two-way balancing valve 23, a first leveling oil cylinder 22 and a second leveling oil cylinder 24. The first port and the fourth port of the second two-way balancing valve 21 are respectively connected to the boom oil circuit, the second port of the second two-way balancing valve 21 is connected to the rodless chamber of the first leveling oil cylinder 22 and the first port of the third two-way balancing valve 23, the third port of the second two-way balancing valve 21 is connected to the rod chamber of the first leveling oil cylinder 22 and the fourth port of the third two-way balancing valve 23, and the second port and the third port of the third two-way balancing valve 23 are respectively connected to the rodless chamber and the rod chamber of the second leveling oil cylinder 24; The charging circuit 3 includes a second solenoid reversing valve 33 and a safety valve 32. The first port of the second solenoid reversing valve 33 is connected to the first port of the safety valve 32. The second port of the second solenoid reversing valve 33 is connected to the pipeline between the second port of the second two-way balancing valve 21 and the rodless chamber of the first leveling cylinder 22. The third port of the second solenoid reversing valve 33 is connected to the pipeline between the third port of the second two-way balancing valve 21 and the rod chamber of the first leveling cylinder 22. The safety valve 32 is also connected to the pipeline between the first solenoid reversing valve 11 and the arm oil circuit.

[0036] The hydraulic leveling process of the hydraulic leveling system of the present invention includes: When the boom of the aerial work platform is luffed, the hydraulic oil enters the rodless chamber of the luffing cylinder 13 from the oil outlet C of the boom oil circuit through the first electromagnetic reversing valve 11 (coil DT1 is energized) and the first two-way balancing valve 12, so that the luffing cylinder 13 extends to push the boom upward, and the boom pulls the first leveling cylinder 22 (i.e., the lower leveling cylinder) to extend. At this time, the oil pressure in the rod chamber of the first leveling cylinder 22 increases and enters the rod chamber of the second leveling cylinder 24 (i.e., the upper leveling cylinder); at the same time, the coil DT3 of the second electromagnetic reversing valve 33 is energized, and the hydraulic oil enters the rod chamber of the second leveling cylinder 24 (i.e., the upper leveling cylinder) from the oil outlet C of the boom oil circuit. After port C is decompressed to a preset pressure through the safety valve 32, the rod chamber of the first leveling cylinder 22 is pressurized through the second solenoid reversing valve 33, so that the oil pressure in the rod chamber of the first leveling cylinder 22 quickly reaches the preset pilot pressure of the third two-way balancing valve 23 (that is, the balancing valve in the third two-way balancing valve 23 corresponding to the rodless chamber of the second leveling cylinder 24), thereby solving the problem of leveling lag; when the oil pressure in the rod chamber of the first leveling cylinder 22 reaches the preset pilot pressure of the third two-way balancing valve 23, the second leveling cylinder 24 retracts, so that the aerial work platform always remains level.

[0037] When the boom of the aerial work platform is luffed down, the hydraulic oil enters the rod chamber of the luffing cylinder 13 from the oil outlet D of the boom oil circuit through the first electromagnetic reversing valve 11 (coil DT2 is energized) and the first two-way balancing valve 12, so that the luffing cylinder 13 retracts and pulls the boom downward, and the boom pushes the first leveling cylinder 22 to retract. At this time, the oil pressure in the rodless chamber of the first leveling cylinder 22 increases and enters the rodless chamber of the second leveling cylinder 24; at the same time, the coil DT4 of the second electromagnetic reversing valve 33 is energized, and the hydraulic oil enters the rodless chamber of the second leveling cylinder 24 from the oil outlet C of the boom oil circuit through the safety valve 32. After reducing the pressure to a preset pressure, the rodless chamber of the first leveling cylinder 22 is pressurized through the second electromagnetic reversing valve 33, so that the oil pressure in the rodless chamber of the first leveling cylinder 22 quickly reaches the preset pilot pressure of the third two-way balancing valve 23 (that is, the balancing valve in the third two-way balancing valve 23 corresponding to the rod chamber of the second leveling cylinder 24), thereby solving the problem of leveling lag; when the oil pressure in the rodless chamber of the first leveling cylinder 22 reaches the preset pilot pressure of the third two-way balancing valve 23, the second leveling cylinder 24 extends out, so that the aerial work platform always remains level.

[0038] The present invention draws hydraulic oil from the luffing circuit 1 through the charging circuit 3 to perform unilateral pressurization on the first leveling cylinder 22, thereby avoiding the problem of increased return oil back pressure during the leveling process; when the boom is luffed up, the rod chamber of the leveling circuit 2 is pressurized; when the boom is luffed down, the rodless chamber of the leveling circuit 2 is pressurized, thereby realizing the linkage between the charging of the leveling circuit 2 and the luffing of the boom, and the charging circuit 3 only works when the boom is luffed, thereby reducing the energy loss of the system.

[0039] In a specific embodiment of the present invention, the safety valve 32 is a pressure cut-off valve, a pressure reducing valve or a pressure reducing relief valve, which avoids the problem that the pressure after the overflow affects the amplitude adjustment pressure due to the traditional pressure charging circuit being a relief valve.

[0040] When the safety valve 32 is a pressure cut-off valve or a pressure reducing valve, the second port of the pressure cut-off valve or the pressure reducing valve is connected to the pipeline between the first port of the first electromagnetic reversing valve 11 and the boom oil circuit, such as Figure 1 As shown; when the safety valve 32 is a pressure reducing relief valve, the second port of the pressure reducing relief valve is connected to the pipeline between the first port of the first electromagnetic reversing valve 11 and the boom oil circuit, and the third port of the pressure reducing relief valve is connected to the pipeline between the fourth port of the first electromagnetic reversing valve 11 and the boom oil circuit, as shown Figure 2 shown.

[0041] In order to solve the leveling lag problem caused by the volume change caused by the change in oil compression and the expansion of the pipeline volume, the present invention designs the preset pressure of the safety valve 32 by calculating the volume change caused by the compression of the hydraulic oil and the expansion of the pipeline during the leveling process. The specific calculation formula is shown in formulas (1) to (3) in the first embodiment of the present invention. The actual value of the preset pressure of the safety valve 32 can be obtained by verifying and fine-tuning the theoretical value of the preset pressure of the safety valve 32. The preset pressure of the safety valve 32 is less than the preset pilot pressure of the third two-way balancing valve 23. When the amplitude variation pressure exceeds the preset pressure of the safety valve 32, the safety valve 32 reverses, that is, the charging pressure entering the leveling circuit 2 is always less than the preset pilot pressure of the third two-way balancing valve 23, which solves the influence of the amplitude variation pressure on the leveling circuit 2 during the normal amplitude variation process.

[0042] What is disclosed above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or modifications within the technical scope disclosed in the present invention, which should be covered within the protection scope of the present invention.

Claims

1. A hydraulic leveling system for an aerial work platform, comprising a variable amplitude circuit, a leveling circuit and a charging circuit; the variable amplitude circuit comprises a first electromagnetic reversing valve, a first two-way balancing valve and a variable amplitude oil cylinder, the first port and the fourth port of the first electromagnetic reversing valve are respectively connected to the boom oil circuit, the second port and the third port of the first electromagnetic reversing valve are respectively connected to the first port and the fourth port of the first two-way balancing valve, the second port and the third port of the first two-way balancing valve are respectively connected to the rodless chamber and the rod chamber of the variable amplitude oil cylinder; the leveling circuit comprises a second two-way balancing valve, a third two-way balancing valve, a first leveling oil cylinder and a second leveling oil cylinder, the first port and the fourth port of the second two-way balancing valve are respectively connected to the boom oil circuit, the second port of the second two-way balancing valve is connected to the rodless chamber of the first leveling oil cylinder and the first port of the third two-way balancing valve, the third port of the second two-way balancing valve is connected to the rod chamber of the first leveling oil cylinder and the fourth port of the third two-way balancing valve, the second port and the third port of the third two-way balancing valve are respectively connected to the rodless chamber and the rod chamber of the second leveling oil cylinder; characterized in that: The charging circuit includes a reversing valve and a safety valve, the first port of the reversing valve is connected to the safety valve, the second port of the reversing valve is connected to the pipeline between the second port of the second two-way balancing valve and the rodless chamber of the first leveling cylinder, the third port of the reversing valve is connected to the pipeline between the third port of the second two-way balancing valve and the rod chamber of the first leveling cylinder, and the safety valve is also connected to the pipeline between the first electromagnetic reversing valve and the arm oil circuit.

2. The hydraulic leveling system according to claim 1, characterized in that: The reversing valve is a hydraulically controlled reversing valve or a second electromagnetic reversing valve; When the reversing valve is a hydraulically controlled reversing valve, the first control port of the hydraulically controlled reversing valve is also connected to the pipeline between the second port of the first electromagnetic reversing valve and the first port of the first two-way balancing valve, and the second control port of the hydraulically controlled reversing valve is also connected to the pipeline between the third port of the first electromagnetic reversing valve and the fourth port of the first two-way balancing valve.

3. The hydraulic leveling system according to claim 1, characterized in that: The safety valve is a pressure cut-off valve, a pressure reducing valve or a pressure reducing relief valve; When the safety valve is a pressure cut-off valve or a pressure reducing valve, the second port of the pressure cut-off valve or the pressure reducing valve is connected to the pipeline between the first port of the first electromagnetic reversing valve and the boom oil circuit; When the safety valve is a pressure reducing relief valve, the second port of the pressure reducing relief valve is connected to the pipeline between the first port of the first electromagnetic reversing valve and the arm oil circuit, and the third port of the pressure reducing relief valve is connected to the pipeline between the fourth port of the first electromagnetic reversing valve and the arm oil circuit.

4. The hydraulic leveling system according to claim 1, characterized in that: The first two-way balancing valve includes a first damper and a second damper, and the first damper and the second damper are arranged between the first port and the fourth port of the first two-way balancing valve.

5. The hydraulic leveling system according to any one of claims 1 to 4, characterized in that: A filter is provided on the pipeline between the first electromagnetic reversing valve and the boom oil circuit.

6. An aerial work platform, characterized in that: The aerial work platform comprises a hydraulic leveling system as described in any one of claims 1 to 5.

7. A hydraulic leveling method, characterized in that: Applied to the hydraulic leveling system according to any one of claims 1 to 5, the hydraulic leveling method comprises: When the boom is luffed, the hydraulic oil enters the rodless chamber of the luffing cylinder from the boom oil circuit through the first electromagnetic reversing valve and the first two-way balancing valve, so that the luffing cylinder extends to push the boom upward, and the boom pulls the first leveling cylinder to extend. At this time, the oil pressure in the rod chamber of the first leveling cylinder increases and enters the rod chamber of the second leveling cylinder; at the same time, after the hydraulic oil is reduced to a preset pressure through the safety valve from the boom oil circuit, it is pressurized into the rod chamber of the first leveling cylinder through the reversing valve, so that the oil pressure in the rod chamber of the first leveling cylinder quickly reaches the preset pilot pressure of the third two-way balancing valve; when the oil pressure in the rod chamber of the first leveling cylinder reaches the preset pilot pressure of the third two-way balancing valve, the second leveling cylinder retracts, so that the aerial work platform always remains level; When the boom is luffed down, the hydraulic oil enters the rod chamber of the luffing cylinder from the boom oil circuit through the first electromagnetic reversing valve and the first two-way balancing valve, so that the luffing cylinder retracts and pulls the boom downward, and the boom pushes the first leveling cylinder to retract. At this time, the oil pressure in the rodless chamber of the first leveling cylinder increases and enters the rodless chamber of the second leveling cylinder; at the same time, the hydraulic oil is reduced to a preset pressure from the boom oil circuit through the safety valve, and then pressurized into the rodless chamber of the first leveling cylinder through the reversing valve, so that the oil pressure in the rodless chamber of the first leveling cylinder quickly reaches the preset pilot pressure of the third two-way balancing valve; when the oil pressure in the rodless chamber of the first leveling cylinder reaches the preset pilot pressure of the third two-way balancing valve, the second leveling cylinder extends to keep the aerial work platform always level.

8. The hydraulic leveling method according to claim 7, characterized in that: The theoretical calculation formula for the preset pressure of the safety valve is: ； ， ； in, Indicates the theoretical value of the preset pressure of the safety valve. represents the bulk modulus of the oil, Indicates the amount of oil compression, Indicates the volume change of the pipeline between the first leveling cylinder and the second leveling cylinder. It represents the initial oil volume in the first leveling cylinder, the second leveling cylinder and the pipeline between the first leveling cylinder and the second leveling cylinder. Indicates the pressure change value in the leveling circuit. Indicates the volume expansion value of the pipeline between the first leveling cylinder and the second leveling cylinder. Indicates the length of the pipeline between the first leveling cylinder and the second leveling cylinder.

Images