Aerial work platform and hydraulic control system and control method thereof

Abstract

The present invention discloses an aerial work platform and its hydraulic control system and control method. The hydraulic control system includes a hydraulic oil tank, a driving motor for driving a gear pump, a gear pump, an electromagnetic reversing valve, a two-way balancing valve, an unloading valve and a throttling device; the inlet of the gear pump is connected to the hydraulic oil tank, and the outlet of the gear pump is connected to the first port of the electromagnetic reversing valve and the first port of the unloading valve; the second port of the unloading valve is connected to the throttling device, and the throttling device is connected to the second port of the electromagnetic reversing valve and the hydraulic oil tank; the third port and the fourth port of the electromagnetic reversing valve are respectively connected to the first port and the second port of the two-way balancing valve, and the third port and the fourth port of the two-way balancing valve are respectively connected to the load cylinder. The present invention avoids the frequent abnormal wear failure of the gear pump caused by the low speed of the gear pump; the influence of the load start-stop working condition of the gear pump is improved by controlling the power gain and loss timing of the motor, the electromagnetic reversing valve and the unloading valve.

Description

Technical Field

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

[0002] The hydraulic control systems of existing millet-segment (usually 10 to 16 meters) electric articulated boom aerial work platforms generally use a DC motor + gear pump connection method or an AC motor + gear pump connection method, and use pump control or valve control, or a combination of pump control and valve control, to achieve the arm movement and steering movement of the entire vehicle.

[0003] When some pump control actions of the Xiaomi electric articulated boom crane meet the flow demand, the gear pump speed is low, basically close to the minimum speed of the gear pump, resulting in frequent abnormal wear and failure of the gear pump; while ensuring that the rest of the machine's movement speed is not affected, it becomes particularly important to increase the motor speed without reducing the gear pump displacement, and due to the influence of the gear pump's load start and stop caused by the power-on timing of the motor, reversing valve and unloading valve, the gear pump wears, the system does not build up pressure, and the boom moves slowly or does not move.

[0004] Take the hydraulic system of the AB14 / 16EJ articulated boom aerial work platform as an example. When the flying boom moves, the actual required flow rate Q A When the flow rate is 2.6L / min, assuming that the displacement D of the main power-gear pump is 4.5ml / r, the theoretical output flow of the hydraulic pump (i.e., gear pump) when the flying arm moves is:

[0005] Q T =Q A / η (1)

[0006] Among them, Q T Indicates the theoretical output flow of the hydraulic pump; Q A represents the actual required flow rate of the flying arm action; η represents the volumetric efficiency, and the gear pump volumetric efficiency is generally 92%. According to formula (1), the theoretical output flow rate of the hydraulic pump can be calculated to be 2.83L / min. The relationship between the theoretical output flow rate of the hydraulic pump and its speed is:

[0007] Q T =Dn (2)

[0008] Where D is the displacement of the gear pump, and n is the speed of the gear pump. According to formula (2), the gear pump speed can be calculated to be 629 r / min, which is close to the minimum speed of the gear pump, 600 r / min, and is likely to cause frequent abnormal wear failures of the gear pump. Summary of the invention

[0009] The object of the present invention is to provide an aerial work platform and its hydraulic control system and control method to solve at least one of the problems of frequent abnormal wear failures of the gear pump due to the low speed of the gear pump, wear of the gear pump due to the power-on timing, no pressure buildup in the system, slow movement of the boom or even no movement.

[0010] The present invention solves the above technical problems through the following technical solutions: a hydraulic control system for an aerial work platform, comprising a hydraulic oil tank, a driving motor for driving a gear pump, a gear pump, an electromagnetic reversing valve, a two-way balancing valve, an unloading valve and a throttling device; the inlet of the gear pump is connected to the hydraulic oil tank, and the outlet of the gear pump is connected to the first port of the electromagnetic reversing valve and the first port of the unloading valve; the second port of the unloading valve is connected to the throttling device, and the throttling device is connected to the second port of the electromagnetic reversing valve and the hydraulic oil tank; the third port and the fourth port of the electromagnetic reversing valve are respectively connected to the first port and the second port of the two-way balancing valve, and the third port and the fourth port of the two-way balancing valve are respectively connected to the load cylinder;

[0011] When the system starts to move, the electromagnetic reversing valve and the driving motor are first controlled to be energized at the same time, and after a delay time t1, the unloading valve is controlled to be energized; when the system stops moving, the unloading valve is first controlled to be de-energized, and after a delay time t2, the electromagnetic reversing valve and the driving motor are controlled to be de-energized at the same time.

[0012] Furthermore, a first filter is provided on the outlet pipeline of the gear pump, and a second filter is provided on the pipeline between the throttling element and the hydraulic oil tank.

[0013] Furthermore, a one-way valve is provided on the outlet pipeline of the gear pump.

[0014] Furthermore, overflow valves are connected in parallel at both ends of the unloading valve and the throttling element.

[0015] Furthermore, the throttling element is one of a damper, a throttle hole and a throttle valve.

[0016] Further, the bidirectional balancing valve comprises a first damper and a second damper, wherein the first damper and the second damper are arranged between the first port and the second port of the bidirectional balancing valve;

[0017] According to the action speed requirement, the first damping and the second damping in the bidirectional balancing valve are selected so that the magnitudes of the first damping and the second damping in the bidirectional balancing valve are adapted to the action speed.

[0018] Based on the same concept, the present invention also provides a control method for a hydraulic control system of an aerial work platform, the hydraulic control system comprising a hydraulic oil tank, a drive motor for driving a gear pump, a gear pump, an electromagnetic reversing valve, a two-way balancing valve, an unloading valve and a throttling device; the inlet of the gear pump is connected to the hydraulic oil tank, and the outlet of the gear pump is connected to the first port of the electromagnetic reversing valve and the first port of the unloading valve; the second port of the unloading valve is connected to the throttling device, and the throttling device is connected to the second port of the electromagnetic reversing valve and the hydraulic oil tank; the third port and the fourth port of the electromagnetic reversing valve are respectively connected to the first port and the second port of the two-way balancing valve, and the third port and the fourth port of the two-way balancing valve are respectively connected to the load cylinder; the control method comprises:

[0019] When the system starts to work, the control electromagnetic reversing valve and the drive motor are energized at the same time, and the gear pump is in the unloading rotation state driven by the drive motor. After the delay time t1, the control unloading valve is energized, and the gear pump is in the loading action state;

[0020] When the system stops working, the unloading valve is first controlled to lose power, and after the delay time t2, the electromagnetic reversing valve and the drive motor are controlled to lose power at the same time.

[0021] Furthermore, when the system stops operating, before the unloading valve is controlled to lose power, the control method further includes:

[0022] The driving motor is controlled to decelerate, and when the speed of the driving motor drops to a speed threshold, the unloading valve is controlled to lose power.

[0023] Furthermore, the time t1 and the time t2 are 200 ms to 250 ms.

[0024] Based on the same concept, the present invention also provides an aerial work platform, which includes the hydraulic control system as described above.

[0025] Beneficial Effects

[0026] Compared with the prior art, the advantages of the present invention are:

[0027] The present invention introduces a two-way balancing valve, which increases the speed of the gear pump for operations with a low speed, thereby avoiding frequent abnormal wear failures of the gear pump caused by the low speed of the gear pump; optimizes the system action impact by means of a unloading valve + throttling device; and improves the problems of gear pump wear, system pressure failure, slow arm movement or even no movement caused by load start and stop conditions of the gear pump through power-on timing control of the electromagnetic reversing valve, the drive motor and the unloading valve, thereby optimizing the operation of the gear pump and solving the gear pump wear problem.

[0028] The present invention reduces product failure rate and return repair rate, reduces after-sales maintenance costs, and improves product performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] 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.

[0030] Figure 1 It is a schematic diagram of a hydraulic control system in an embodiment of the present invention.

[0031] Explanation of the reference numerals: 1-hydraulic oil tank, 2-driving motor, 3-gear pump, 4-check valve, 5-first filter, 6-overflow valve, 7-unloading valve, 8-electromagnetic reversing valve, 9-two-way balancing valve, 10-load cylinder, 11-damping, 12-second filter. DETAILED DESCRIPTION

[0032] 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.

[0033] 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.

[0034] Example 1

[0035] like Figure 1 As shown, a hydraulic control system for an aerial work platform provided in an embodiment of the present invention includes a hydraulic oil tank 1, a driving motor 2 for driving a gear pump 3, a gear pump 3, an electromagnetic reversing valve 8, a two-way balancing valve 9, an unloading valve 7 and a throttling device; the inlet of the gear pump 3 is connected to the hydraulic oil tank 1, and the outlet of the gear pump 3 is connected to the first port of the electromagnetic reversing valve 8 and the first port of the unloading valve 7; the second port of the unloading valve 7 is connected to the throttling device, and the throttling device is connected to the second port of the electromagnetic reversing valve 8 and the hydraulic oil tank 1; the third port of the electromagnetic reversing valve 8 is connected to the first port of the two-way balancing valve 9, the fourth port of the electromagnetic reversing valve 8 is connected to the second port of the two-way balancing valve 9, and the third port and the fourth port of the two-way balancing valve 9 are respectively connected to the load cylinder 10.

[0036] Take the flying boom action as an example. According to formula (2), when the displacement of the gear pump 3 remains unchanged, the speed of the gear pump 3 increases during the flying boom action, and the output flow of the gear pump 3 increases synchronously. Due to the introduction of the two-way balancing valve 9, the flow at the outlet of the gear pump 3 has two paths: one path passes through the first and third ports of the electromagnetic reversing valve 8 and the one-way valve in the two-way balancing valve 9 in turn, reaches the rodless chamber of the load cylinder 10, pushes the load cylinder 10 to extend, and completes the flying boom action; the other path passes through the first and third ports of the electromagnetic reversing valve 8, the first and second damping in the two-way balancing valve 9 in turn, and then passes through the fourth and second ports of the electromagnetic reversing valve 8 to reach the hydraulic oil tank 1. The flow is divided into two parts by the two-way balancing valve 9, one part is provided to the load cylinder 10 to complete the flying arm action, and the other part flows back to the hydraulic oil tank 1 through the pressure-dividing bridge formed by the two damping and pilot oil channels of the two-way balancing valve 9, thereby increasing the outlet flow of the gear pump 3, thereby increasing the speed of the gear pump 3, so that the speed of the gear pump 3 corresponding to each action in the system is within the required range, avoiding the problem of frequent abnormal wear and failure of the gear pump 3 caused by the low speed and high friction of the gear pump 3; while increasing the speed of the drive motor 2, the flying arm action speed will not be affected.

[0037] In a specific embodiment of the present invention, the two-way balancing valve 9 includes a first damper and a second damper, and the first damper and the second damper are arranged between the first port and the second port of the two-way balancing valve 9. The first damper and the second damper of the two-way balancing valve 9 form a pressure-dividing bridge with the pilot oil passage of the two-way balancing valve 9, thereby reducing the pilot ratio of the entire two-way balancing valve 9. The first damper and the second damper in the two-way balancing valve 9 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 two-way balancing valve 9 is changed by dampers of different sizes to adapt to actions with different speed requirements, such as swinging of the working fence, rotation of the turntable, flying arm action, walking and turning, and the like.

[0038] When the action starts, the electromagnetic reversing valve 8 and the drive motor 2 are controlled to be energized at the same time. At this time, the drive motor 2 is idling, and the outlet flow of the gear pump 3 flows back to the hydraulic oil tank 1 through the unloading valve 7 and the throttle, that is, the drive motor 2 is in an unloading rotation state. The unloading valve 7 loses power and opens. Since a throttle is provided after the unloading valve 7, a certain pressure is established between the outlet of the gear pump 3 and the load cylinder 10. Although it cannot push the load cylinder 10 to move, it plays a certain buffering role. It takes time t1 to establish a certain pressure between the outlet of the gear pump 3 and the load cylinder 10. Therefore, after the electromagnetic reversing valve 8 and the drive motor 2 are energized, the unloading valve 7 is controlled to be energized and the unloading valve 7 is closed. When the unloading valve 7 is energized, a high pressure is established at the outlet of the gear pump 3, which pushes the load cylinder 10 to move, and the gear pump 3 is in a loading action state. Since there is a certain pressure between the outlet of the gear pump 3 and the load cylinder 10, it plays a buffering role in pressure building, so the starting action becomes relatively smooth, avoiding the pressure shock caused by the electromagnetic reversing valve 8 being energized.

[0039] When stopping the action, first control the unloading valve 7 to lose power and open. If there is no throttling device after the unloading valve 7, the outlet pressure of the gear pump 3 will drop to 0 immediately, and the action will stop immediately from the moving state, which will have a large impact and a poor experience. Since a throttling device is provided after the unloading valve 7 of the present invention, when the unloading valve 7 loses power, the outlet pressure of the gear pump 3 will not drop to 0 immediately, but the pressure will be slowly reduced through the throttling device, and the action speed will gradually slow down. After a delay time t2 after the unloading valve 7 loses power, the electromagnetic reversing valve 8 and the drive motor 2 are controlled to lose power at the same time, and the action stops.

[0040] The actions in the present invention include all actions controlled by the gear pump 3, such as swinging of the working fence, rotation of the turntable, flying arm action, walking and turning, etc. In this embodiment, the time t1 and the time t2 are 200ms to 250ms.

[0041] In a specific embodiment of the present invention, before controlling the unloading valve 7 to lose power, the driving motor 2 is first controlled to decelerate, and when the speed of the driving motor 2 drops to a speed threshold, the unloading valve 7 is controlled to lose power. In this embodiment, the speed threshold is set to 450-550r / min, preferably 500r / min.

[0042] By controlling the power gain and loss timing of the drive motor 2, the electromagnetic reversing valve 8 and the unloading valve 7, it is ensured that during the starting action, the outlet of the gear pump 3 is always connected to the hydraulic oil tank 1, that is, it is ensured that the high pressure is not accumulated at the outlet of the gear pump 3 when the gear pump 3 is started; when the action stops, when the drive motor 2 reduces the speed and the action speed slows down, the gear pump 3 starts to unload, that is, the outlet of the gear pump 3 starts to connect to the hydraulic oil tank 1, to ensure that the outlet of the gear pump 3 is not accumulated at the outlet when the action stops, avoiding the gear pump 3 to start and stop with load, thereby protecting the internal structure of the gear pump 3, and preventing excessive load from causing the meshing gears of the gear pump 3 to be subjected to radial force, resulting in wear of the floating sleeves on both sides of the meshing gears, reduced volumetric efficiency of the gear pump 3, shortened service life and other adverse effects.

[0043] In a specific embodiment of the present invention, a first filter 5 is provided on the outlet pipeline of the gear pump 3, and a second filter 12 is provided on the pipeline between the throttle and the hydraulic oil tank 1. Impurities in the oil circuit are filtered out by the first filter 5 and the second filter 12 to protect the normal operation of the system.

[0044] In a specific embodiment of the present invention, a one-way valve 4 is provided on the outlet pipeline of the gear pump 3 .

[0045] In the hydraulic system, the one-way valve 4 and the electromagnetic reversing valve 8 are usually integrated on a main valve body to achieve a connection mode of the gear pump 3-pipeline-first filter 5-pipeline-one-way valve 4. After the driving motor 2 stops running, the pressure in the pipeline between the gear pump 3 and the one-way valve 4 will push the gear pump 3 to rotate in the opposite direction, causing the gear pump 3 to suck air and dry grind. The present invention sets a one-way valve 4 at the outlet of the gear pump 3, and the pressure in the pipeline between the gear pump 3 and the one-way valve 4 cannot push the gear pump 3 to rotate in the opposite direction, thereby avoiding the high pressure at the outlet of the gear pump 3 pushing the gear pump 3 to rotate in the opposite direction when the driving motor 2 stops running, thereby causing the gear pump 3 to suck air and wear in the opposite direction, and improving the wear failure of the gear pump 3. At the same time, the one-way valve 4 also plays a role in stabilizing the system flow, preventing the influence of system pressure fluctuations on the gear pump 3, and reducing the vibration and noise of the gear pump 3.

[0046] In a specific embodiment of the present invention, an overflow valve 6 is connected in parallel at both ends of the unloading valve 7 and the throttling member to play a safety protection role.

[0047] In a specific embodiment of the present invention, the throttling element is one of a damper 11, a throttle hole and a throttle valve.

[0048] In a specific embodiment of the present invention, the driving motor 2 is a DC motor or an AC motor.

[0049] In a specific embodiment of the present invention, the electromagnetic reversing valve 8 is a three-position four-way electromagnetic reversing valve 8 .

[0050] Example 2

[0051] A control method for a hydraulic control system of an aerial work platform provided in an embodiment of the present invention, wherein the hydraulic control system includes a hydraulic oil tank 1, a drive motor 2 for driving a gear pump 3, a gear pump 3, an electromagnetic reversing valve 8, a two-way balancing valve 9, an unloading valve 7 and a throttling device; the inlet of the gear pump 3 is connected to the hydraulic oil tank 1, and the outlet of the gear pump 3 is connected to the first port of the electromagnetic reversing valve 8 and the first port of the unloading valve 7; the second port of the unloading valve 7 is connected to the throttling device, and the throttling device is connected to the second port of the electromagnetic reversing valve 8 and the hydraulic oil tank 1; the third port and the fourth port of the electromagnetic reversing valve 8 are respectively connected to the first port and the second port of the two-way balancing valve 9, and the third port and the fourth port of the two-way balancing valve 9 are respectively connected to the load cylinder 10. The control method of the present invention includes:

[0052] When the action starts, the electromagnetic reversing valve 8 and the drive motor 2 are energized at the same time. At this time, the drive motor 2 is idling, and the outlet flow of the gear pump 3 flows back to the hydraulic oil tank 1 through the unloading valve 7 and the throttle, that is, the drive motor 2 is in an unloaded rotation state; after the electromagnetic reversing valve 8 and the drive motor 2 are energized for a delay time t1, the unloading valve 7 is controlled to be energized, and a high pressure is established at the outlet of the gear pump 3 to push the load cylinder 10 to move, and the gear pump 3 is in a loaded action state.

[0053] When stopping the action, first control the unloading valve 7 to lose power, and the outlet pressure of the gear pump 3 slowly reduces the pressure through the throttling device, and the action speed gradually slows down; after the unloading valve 7 loses power for a delay time t2, the electromagnetic reversing valve 8 and the drive motor 2 are controlled to lose power at the same time, the gear pump 3 stops, and the aerial work platform stops.

[0054] In this embodiment, time t1 and time t2 are 200ms to 250ms. During time t1, a certain pressure is established between the outlet of the gear pump 3 and the load oil cylinder 10; during time t2, the outlet pressure of the gear pump 3 is slowly reduced through the throttling element, and the action speed is gradually slowed down until the action stops without causing impact.

[0055] When the action is stopped, before the unloading valve 7 is controlled to lose power, the control method further includes: controlling the drive motor 2 to decelerate, and when the speed of the drive motor 2 drops to a speed threshold, controlling the unloading valve 7 to lose power. In this embodiment, the speed threshold is set to 450-550r / min, preferably 500r / min.

[0056] 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 control system for an aerial work platform, characterized in that: The hydraulic control system includes a hydraulic oil tank, a driving motor for driving a gear pump, a gear pump, an electromagnetic reversing valve, a two-way balancing valve, an unloading valve and a throttling device; the inlet of the gear pump is connected to the hydraulic oil tank, and the outlet of the gear pump is connected to the first port of the electromagnetic reversing valve and the first port of the unloading valve; the second port of the unloading valve is connected to the throttling device, and the throttling device is connected to the second port of the electromagnetic reversing valve and the hydraulic oil tank; the third port and the fourth port of the electromagnetic reversing valve are respectively connected to the first port and the second port of the two-way balancing valve, and the third port and the fourth port of the two-way balancing valve are respectively connected to the load cylinder; When the system starts to move, the electromagnetic reversing valve and the driving motor are first controlled to be energized at the same time, and after a delay time t1, the unloading valve is controlled to be energized; when the system stops moving, the unloading valve is first controlled to be de-energized, and after a delay time t2, the electromagnetic reversing valve and the driving motor are controlled to be de-energized at the same time.

2. The hydraulic control system of the aerial work platform according to claim 1, characterized in that: A first filter is arranged on the outlet pipeline of the gear pump, and a second filter is arranged on the pipeline between the throttling element and the hydraulic oil tank.

3. The hydraulic control system of the aerial work platform according to claim 1, characterized in that: A one-way valve is arranged on the outlet pipeline of the gear pump.

4. The hydraulic control system of the aerial work platform according to claim 1, characterized in that: An overflow valve is connected in parallel at both ends of the unloading valve and the throttling element.

5. The hydraulic control system for an aerial work platform according to claim 1, characterized in that: The throttling element is one of a damper, a throttle hole and a throttle valve.

6. The hydraulic control system for an aerial work platform according to any one of claims 1 to 5, characterized in that: The two-way balancing valve comprises a first damper and a second damper, wherein the first damper and the second damper are arranged between a first port and a second port of the two-way balancing valve; According to the action speed requirement, the first damping and the second damping in the bidirectional balancing valve are selected so that the magnitudes of the first damping and the second damping in the bidirectional balancing valve are adapted to the action speed.

7. A control method for a hydraulic control system of an aerial work platform, characterized in that: The hydraulic control system includes a hydraulic oil tank, a driving motor for driving a gear pump, a gear pump, an electromagnetic reversing valve, a two-way balancing valve, an unloading valve and a throttling device; the inlet of the gear pump is connected to the hydraulic oil tank, and the outlet of the gear pump is connected to the first port of the electromagnetic reversing valve and the first port of the unloading valve; the second port of the unloading valve is connected to the throttling device, and the throttling device is connected to the second port of the electromagnetic reversing valve and the hydraulic oil tank; the third port and the fourth port of the electromagnetic reversing valve are respectively connected to the first port and the second port of the two-way balancing valve, and the third port and the fourth port of the two-way balancing valve are respectively connected to the load cylinder; the control method includes: When the system starts to work, the control electromagnetic reversing valve and the drive motor are energized at the same time, and the gear pump is in the unloading rotation state driven by the drive motor. After the delay time t1, the control unloading valve is energized, and the gear pump is in the loading action state; When the system stops working, the unloading valve is first controlled to lose power, and after the delay time t2, the electromagnetic reversing valve and the drive motor are controlled to lose power at the same time.

8. The control method of the hydraulic control system of the aerial work platform according to claim 7, characterized in that: When the system stops operating, before the control unloading valve loses power, the control method further includes: The driving motor is controlled to decelerate, and when the speed of the driving motor drops to a speed threshold, the unloading valve is controlled to lose power.

9. The control method of the hydraulic control system of the aerial work platform according to claim 7 or 8, characterized in that: The time t1 and the time t2 are 200 ms to 250 ms.

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

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