Movable arm hydraulic control system and excavator

Abstract

The utility model discloses a movable arm hydraulic control system and an excavator, and belongs to the technical field of engineering machinery. The defects that in the prior art, a traditional movable arm hydraulic control system is slow in control response, large in pressure loss and poor in control precision are overcome. The main structure of the hydraulic system comprises a first main pump, a second main pump, a controller, a movable arm flow collecting valve and a pilot system, an oil outlet of the first main pump is connected with an oil inlet of the movable arm flow collecting valve, and an oil outlet of the second main pump is connected with an oil inlet A of a first movable arm reversing valve. A working oil port E of the first movable arm reversing valve and an oil outlet of the movable arm converging valve converge and then are connected with a rodless cavity of the movable arm oil cylinder through a balance maintaining valve, a working oil port F of the first movable arm reversing valve is connected with a rod cavity of the movable arm oil cylinder, and an oil outlet of the balance maintaining valve is further connected with the rod cavity of the movable arm oil cylinder through an electro-hydraulic proportional valve. The controller sends a control signal to the pilot system. The utility model is mainly applied to engineering machinery such as excavators and the like.

Description

Technical Field

[0001] This utility model belongs to the field of engineering machinery technology, and more specifically, it relates to a boom hydraulic control system and an excavator. Background Technology

[0002] When an excavator is working, the operation of the boom constitutes a large portion of the entire work cycle, significantly impacting the excavator's work efficiency, fuel consumption, and other performance characteristics. Therefore, a well-designed hydraulic control system for the excavator's boom is essential to meet the operational needs of the excavator under various working conditions. Especially in special working conditions such as leveling ground or deep excavation, the boom control system should improve work efficiency and reduce labor intensity; it should also reduce pressure shock and rationally control the descent speed during boom lowering.

[0003] The existing excavator boom control system includes a main pump, a main valve, a boom cylinder, and a logic valve. The main pump is connected to the inlet of the main valve, and the logic valve is located in the oil circuit between the main pump and the main valve inlet. The first working port of the main valve is connected to the rodless chamber (large boom chamber) of the boom cylinder, and the second working port of the main valve is connected to the rod chamber (small boom chamber) of the boom cylinder. The return port of the main valve is connected to the return oil circuit, the bypass port of the main valve is connected to the bypass oil circuit, the inlet of the main valve is connected to the main boom oil circuit, and the logic valve is located on the main boom oil circuit. Both the bypass oil circuit and the main boom oil circuit are connected to the outlet of the main pump. When the main valve is in the neutral position, the bypass oil circuit can pump the pressurized oil from the main pump to other positions. The working principle of boom hydraulic control is as follows: When the boom moves independently, the boom main valve receives a signal from the boom pilot oil circuit, the valve core switches its position, and connects the main pump oil circuit with the boom cylinder oil circuit. The boom's raising and lowering are achieved through the extension and retraction of the cylinder. The speed of the boom's independent movement can be controlled by the magnitude of the pilot signal. At this time, the boom's logic valve does not accept throttling commands and is at its maximum opening. However, the above solution has the following shortcomings:

[0004] 1. Existing boom hydraulic systems lack a floating function: The boom linkage valve core of existing excavator boom hydraulic systems only has three functional positions: boom lifting, neutral, and boom lowering. The entire boom hydraulic system cannot achieve boom floating, meaning that oil cannot return simultaneously when the boom rises or falls. This forces the operator to constantly control the breaker during excavator breaking operations, increasing workload and fatigue. Furthermore, the boom and other devices cannot automatically float to press the breaker's chisel rod, causing the breaker to strike empty and damage both the breaker and the excavator. Additionally, on level ground, the operator needs to constantly adjust the boom and stick angles according to uneven terrain, increasing the difficulty of operation. 2. Existing pilot control is hydraulically controlled, which increases the number of hydraulic lines, resulting in slow control response, pressure loss, and poor control accuracy. 3. Existing boom hydraulic systems have poor energy efficiency. Utility Model Content

[0005] The technical problem to be solved by this utility model is to overcome the shortcomings of the prior art and to provide a boom hydraulic control system and an excavator.

[0006] To achieve the above objectives, this utility model employs the following technical solution:

[0007] A boom hydraulic control system includes a main pump one, a main pump two, a boom one directional valve, a controller, a boom confluence valve, and a pilot system. The outlet of the main pump one is connected to the inlet of the boom confluence valve, and the outlet of the main pump two is connected to the inlet A of the boom one directional valve. The working port E of the boom one directional valve and the outlet of the boom confluence valve merge and are connected to the rodless chamber of the boom cylinder through a balance holding valve. The working port F of the boom one directional valve is connected to the rod chamber of the boom cylinder. The outlet of the balance holding valve is also connected to the rod chamber of the boom cylinder through an electro-hydraulic proportional valve. The controller sends control signals to the pilot system, which is connected to the left and right pilot ports of the boom one directional valve, the pilot port of the balance holding valve, and the pilot port of the boom confluence valve.

[0008] Preferably, the pilot system includes a pilot pump, a boom lowering proportional valve, a boom first lifting proportional valve, a boom second lifting proportional valve, and a proportional pressure reducing valve. The outlet of the pilot pump is connected to the inlet of the boom lowering proportional valve, the boom first lifting proportional valve, the boom second lifting proportional valve, and the proportional pressure reducing valve, respectively. The outlet of the boom lowering proportional valve is connected to the right pilot port of the boom first directional valve and the hydraulic control port of the electro-hydraulic proportional valve, respectively. The outlet of the boom first lifting proportional valve is connected to the left pilot port of the boom first directional valve. The outlet of the boom second lifting proportional valve is connected to the pilot port of the boom confluence valve. The outlet of the proportional pressure reducing valve is connected to the pilot port of the balance holding valve.

[0009] Preferably, the balance holding valve includes a control valve, a valve core, and an overload relief valve. The working oil port E of the boom reversing valve and the oil outlet of the boom confluence valve merge and are then connected to the control valve and the oil inlet of the valve core, respectively. The oil outlet of the valve core is connected to the rodless chamber of the boom cylinder, the overload relief valve, and the oil inlet a of the electro-hydraulic proportional valve, respectively.

[0010] Preferably, a regeneration valve is provided between the oil outlet of the valve core and the oil inlet a of the electro-hydraulic proportional valve.

[0011] Preferably, the oil outlet of the main pump is also connected back to the hydraulic oil tank through the main pump unloading valve.

[0012] Preferably, the oil outlet of the second main pump is also connected back to the hydraulic oil tank through the unloading valve of the second main pump.

[0013] Preferably, the oil outlet of the second main pump is also connected to the oil inlet B of the first boom reversing valve via a check valve.

[0014] An excavator, wherein the excavator is equipped with a boom hydraulic control system as described in any of the above claims.

[0015] Compared with the prior art, the beneficial effects of this utility model are:

[0016] 1. The regeneration valve and electro-hydraulic proportional valve enable flow regeneration during boom descent. Firstly, due to gravity, the pressure in the large chamber of the boom cylinder is higher than that in the small chamber during descent. Based on the hydraulic flow characteristics, the hydraulic oil, through the regeneration valve and electro-hydraulic proportional valve, can simultaneously supply a portion of the pressure oil from the large chamber of the boom cylinder, along with the pressure oil output from the pump, to the small chamber of the boom cylinder. This accelerates the boom descent speed and improves work efficiency. Secondly, when the boom's own weight and load accelerate the descent, to prevent excessive descent speed from causing cavitation due to insufficient oil supply from the main pump, regeneration control allows a portion of the oil from the large chamber of the boom cylinder to replenish the small chamber through the regeneration valve, preventing the boom cylinder from sucking in air during descent.

[0017] 2. By using an electro-hydraulic proportional valve for combined electronic and hydraulic control, the large and small chambers of the boom cylinder can be simultaneously connected back to the hydraulic oil tank under special working conditions, realizing the boom floating function. When the excavator is performing deep digging, leveling, or other working conditions, the boom can be freely adjusted according to the terrain, greatly freeing up the operator.

[0018] 3. This utility model is equipped with a main pump first unloading valve and a main pump second unloading valve. When the excavator is idling or the whole machine is not moving, both the main pump first unloading valve and the main pump second unloading valve receive the maximum control current, so that the main pump returns to the hydraulic oil tank through the unloading valve, which has the functions of saving energy and reducing pressure loss.

[0019] In summary, this utility model not only enables boom floating to meet the operational needs of flat ground and deep excavation, but also allows for controllable boom descent speed, flow regeneration, and dual-pump combined oil supply during boom lifting, thereby improving work efficiency. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the hydraulic system of this utility model;

[0021] Figure 2 This is a schematic diagram of the balance holding valve in this utility model;

[0022] Figure 3 This is a schematic diagram of the boom reversing valve in this utility model;

[0023] Figure 4 This is a schematic diagram of the electro-hydraulic proportional valve in this utility model.

[0024] In the diagram: 1. Hydraulic oil tank; 2. Engine; 3. Main pump one; 4. Main pump two; 5. Check valve; 6. Boom one directional valve; 7. Pilot pump; 8. Main pump two unloading valve; 9. Boom lowering proportional valve; 10. Boom one lifting proportional valve; 11. Boom two lifting proportional valve; 12. Proportional pressure reducing valve; 13. Controller; 14. Electric control handle; 15. Boom cylinder; 16. Electro-hydraulic proportional valve; 17. Regeneration valve; 18. Balance holding valve; 19. Boom confluence valve; 20. Main pump one unloading valve; 181. Control valve; 182. Valve core; 183. Overload relief valve. Detailed Implementation

[0025] The present invention will be further described below through specific embodiments and in conjunction with the accompanying drawings.

[0026] Example 1:

[0027] like Figure 1-4 As shown, a boom hydraulic control system includes a main pump 3, a second main pump 4, a boom directional valve 6, a controller 13, a boom confluence valve 19, and a pilot system. The outlet of the first main pump 3 is connected to the inlet of the boom confluence valve 19, and the outlet of the second main pump 4 is connected to the inlet A of the boom directional valve 6. The working port E of the boom directional valve 6 and the outlet of the boom confluence valve 19 merge and are connected to the rodless chamber of the boom cylinder 15 through a balance holding valve 18. The working port F of the directional valve 6 is connected to the rod chamber of the boom cylinder 15. The outlet of the balance holding valve 18 is also connected to the rod chamber of the boom cylinder 15 through the electro-hydraulic proportional valve 16. The controller 13 sends a control signal to the pilot system. The pilot system is connected to the left and right pilot ports of the boom directional valve 6, the pilot port of the balance holding valve 18, and the pilot port of the boom confluence valve 19, respectively. The outlet of the main pump 4 is also connected to the inlet B of the boom directional valve 6 through the check valve 5.

[0028] Example 2:

[0029] A boom hydraulic control system differs from Embodiment 1 in that the pilot system includes a pilot pump 7, a boom lowering proportional valve 9, a boom first lifting proportional valve 10, a boom second lifting proportional valve 11, and a proportional pressure reducing valve 12. The oil outlet of the pilot pump 7 is connected to the oil inlets of the boom lowering proportional valve 9, the boom first lifting proportional valve 10, the boom second lifting proportional valve 11, and the proportional pressure reducing valve 12, respectively. The oil outlet of the boom lowering proportional valve 9 is connected to the right pilot oil port of the boom first reversing valve 6 and the hydraulic control port of the electro-hydraulic proportional valve 16, respectively. The oil outlet of the boom first lifting proportional valve 10 is connected to the left pilot oil port of the boom first reversing valve 6. The oil outlet of the boom second lifting proportional valve 11 is connected to the pilot oil port of the boom confluence valve 19. The oil outlet of the proportional pressure reducing valve 12 is connected to the pilot oil port of the balance holding valve 18.

[0030] For example Figure 2 As shown, the balance holding valve 18 includes a control valve 181, a valve core 182, and an overload relief valve 183. The working oil port E of the boom reversing valve 6 and the oil outlet of the boom confluence valve 19 are merged and then connected to the oil inlets of the control valve 181 and the valve core 182, respectively. The oil outlet of the valve core 182 is connected to the rodless chamber of the boom cylinder 15, the overload relief valve 183, and the oil inlet a of the electro-hydraulic proportional valve 16, respectively.

[0031] Furthermore, a regeneration valve 17 is provided between the oil outlet of the valve core 182 and the oil inlet a of the electro-hydraulic proportional valve 16.

[0032] Furthermore, the oil outlet of main pump 3 is also connected back to hydraulic oil tank 1 through main pump 1 unloading valve 20, and the oil outlet of main pump 4 is also connected back to hydraulic oil tank 1 through main pump 2 unloading valve 8.

[0033] Specifically, engine 2 is coaxially connected to main pump 3, main pump 4, and pilot pump 7, providing them with power. This power drives the suction port of main pump 3 to draw oil from the hydraulic oil tank 1. The output pressure oil from the outlet of main pump 3 is divided into two paths: one path leads directly to the inlet of boom confluence valve 19, and the other path passes through the inlet of main pump 1 unloading valve 20 and connects back to the hydraulic oil tank 1 from the outlet of main pump 1 unloading valve 20. The suction port of main pump 4 draws oil from the hydraulic oil tank 1, and the output pressure oil from the outlet of main pump 2 is divided into three paths: one path leads directly to the inlet A of boom directional valve 6; the second path passes through check valve 5 and connects to the inlet B of boom directional valve 6; and the third path passes through the inlet of main pump 2 unloading valve 8 and connects back to the hydraulic oil tank 1 from the outlet of main pump 2 unloading valve 8. The working port E of the boom directional valve 6 merges with the outlet of the boom confluence valve 19 and is connected to the rodless chamber of the boom cylinder 15 via a hydraulic line through the balance holding valve 18. The working port F of the boom directional valve 6 is connected to the rod chamber of the boom cylinder 15 via a hydraulic line. The oil outlet of the balance holding valve 18 is divided into three paths: one path is connected to the rodless chamber of the boom cylinder 15; one path is connected back to the overload relief valve 183 inside the balance holding valve 18; and one path is connected to the inlet a of the electro-hydraulic proportional valve 16 via the regeneration valve 17. The outlet b of the electro-hydraulic proportional valve 16 is connected to the rod chamber of the boom cylinder 15. The ports c and d of the electro-hydraulic proportional valve 16 are connected to the hydraulic oil tank 1. The suction port of the pilot pump 7 is connected to the hydraulic oil tank 1. The outlet of the pilot pump 7 is connected to the inlet of the boom lowering proportional valve 9, the boom first lifting proportional valve 10, the boom second lifting proportional valve 11, and the proportional pressure reducing valve 12, respectively. The drain ports of the boom lowering proportional valve 9, the boom first lifting proportional valve 10, the boom second lifting proportional valve 11, and the proportional pressure reducing valve 12 are all connected to the hydraulic oil tank 1. The outlet of the boom lowering proportional valve 9 is divided into two paths: one path is connected to the right pilot port of the boom first reversing valve 6, and the other path is connected to the hydraulic control port of the electro-hydraulic proportional valve 16. The outlet of the boom first lifting proportional valve 10 is connected to the left pilot port of the boom first reversing valve 6. The outlet of the boom second lifting proportional valve 11 is connected to the pilot port of the boom confluence valve 19. The outlet of the proportional pressure reducing valve 12 is connected to the pilot port of the control valve 181 in the balance holding valve 18. The electric control handle 14 is electrically connected to the controller 13. The controller 13 sends control signals to the main pump second unloading valve 8, the boom lowering proportional valve 9, the boom first lifting proportional valve 10, the boom second lifting proportional valve 11, the proportional pressure reducing valve 12, the electro-hydraulic proportional valve 16, and the main pump first unloading valve 20.

[0034] Among them, the main pump second unloading valve 8 and the main pump first unloading valve 20 are three-position two-way electro-proportional valves, the boom confluence valve 19 is a two-position two-way valve, the electro-hydraulic proportional valve 16 is a three-position four-way valve, the control valve 181 is a three-position four-way valve, and the boom first reversing valve 6 is a three-position six-way valve.

[0035] Example 3:

[0036] An excavator is provided with a boom hydraulic control system as described in Embodiment 1 or Embodiment 2 above.

[0037] The working principle of this utility model is as follows:

[0038] Boom Holding: Boom 1 directional valve 6 has three positions: left, center, and right, corresponding to boom lifting, boom holding, and boom lowering, respectively. Boom 1 lifting proportional valve 10, Boom 2 lifting proportional valve 11, and proportional pressure reducing valve 12 are all de-energized. Boom 1 directional valve 6 is in the center position. At this time, controller 13 outputs maximum current to main pump 2 unloading valve 8 and main pump 1 unloading valve 20, causing main pump 2 unloading valve 8 to operate in the right position and main pump 1 unloading valve 20 to operate in the left position. Main pump 1 3 and main pump 2 4 are unloaded back to hydraulic oil tank 1 through the two unloading valves. The oil output from the main pumps no longer needs to return through the central bypass circuit, eliminating friction loss and throttling loss, thus achieving energy saving. When the boom is held in the holding position, the proportional pressure reducing valve 12 has no current, the control valve 181 in the balance holding valve 18 is in the right position, and the oil in the rodless chamber of the boom cylinder 15 will act on the upper chamber and bottom of the valve core 182. Since the area of ​​the upper chamber is larger than the area of ​​the bottom, and due to the action of the spring, the balance holding valve 18 is in the closed state, and the boom will remain in a certain position.

[0039] Boom lifting action: Pilot oil output from pilot pump 7 supplies pilot oil to boom lifting proportional valve 10. The operator pushes the electric control handle 14. The stroke displacement of the electric control handle 14 determines the current of boom lifting proportional valve 10 (the larger the stroke of the electric control handle 14, the larger the control current of boom lifting proportional valve 10), thereby controlling the pilot pressure for boom lifting. The pilot pressure oil output from boom lifting proportional valve 10 pushes the valve core of boom reversing valve 6 to the right, and boom reversing valve 6 operates in the left position. The hydraulic oil output from main pump 2 4 enters the rodless chamber of boom cylinder 15, and the oil in the rod chamber returns to the hydraulic oil tank 1, thus completing the boom lifting action.

[0040] Simultaneously, the boom-second lifting proportional valve 11 also receives a proportional current signal, outputting pilot pressure to the pilot port of the boom confluence valve 19, causing the boom confluence valve 19 to operate in the left position. Thus, the pressure oil output from the main pump 3 merges with the hydraulic oil output from the main pump 4 via the boom confluence valve 19, flowing together into the rodless chamber of the boom cylinder 15 for boom lifting. The boom lifting confluence is achieved through the boom-first reversing valve 6 and the boom confluence valve 19, increasing the flow rate and improving efficiency. At this time, the electromagnets of the main pump second unloading valve 8, the electro-hydraulic proportional valve 16, and the main pump first unloading valve 20 are all de-energized.

[0041] Boom lowering action: Pilot oil output from pilot pump 7 supplies boom lowering proportional valve 9. The operator pushes the electric control handle 14. The stroke displacement of the electric control handle 14 determines the current of boom lowering proportional valve 9 (the larger the stroke of the electric control handle 14, the larger the control current of boom lowering proportional valve 9), thereby controlling the pilot pressure for boom lifting. The pilot pressure oil output from boom lowering proportional valve 9 pushes the valve core of boom first reversing valve 6 to the left, and boom first reversing valve 6 operates in the right position. Hydraulic oil output from main pump 2 4 enters the rod chamber of boom cylinder 15, and the oil in the rodless chamber returns to the hydraulic oil tank 1 through the balance holding valve 18, thus completing the boom lowering action. At this time, the proportional pressure reducing valve 12 outputs continuously adjustable pressure to control the control valve 181 to move between the neutral and left positions, thereby adjusting the boom lowering speed. Furthermore, the electro-hydraulic proportional valve 16 electromagnets are all de-energized. However, since the oil outlet of the boom lowering proportional valve 9 outputs pressurized oil connected to the control oil port of the electro-hydraulic proportional valve 16, the pressurized oil will overcome the spring force of the reset spring of the electro-hydraulic proportional valve 16, causing the electro-hydraulic proportional valve 16 to work in the upper position. The oil in the rodless chamber of the boom cylinder 15 enters the rod chamber of the boom cylinder 15 through the regeneration valve 17 and the electro-hydraulic proportional valve 16, thus realizing the regeneration control of the boom lowering flow. On the one hand, when the boom descends, due to gravity, the pressure in the large chamber of the boom cylinder 15 is higher than that in the small chamber. According to the oil flow characteristics, the hydraulic oil can supply part of the pressure oil in the large chamber of the boom cylinder 15 and the pressure oil output by the pump to the small chamber of the boom cylinder 15 simultaneously through the regeneration valve 17 and the electro-hydraulic proportional valve 16, which can accelerate the boom descent speed and improve work efficiency. At the same time, when the boom's own weight and load accelerate the descent, in order to prevent the descent speed from being too fast and causing the pump to supply oil in time and resulting in cavitation, regeneration control is used to replenish the small chamber of the boom cylinder 15 with oil through the regeneration valve 17, preventing the cylinder from sucking in air when the boom descends.

[0042] The overload relief valve 183 is used to limit the maximum working pressure of the boom cylinder 15, and plays a safety protection role when the boom is lifted and held.

[0043] When performing leveling or deep excavation work, the boom is first raised or lowered to a suitable height. Once the boom reaches the appropriate floating position, the controller 13 sends an electrical signal to the electro-hydraulic proportional valve 16, energizing it. At this point, the electro-hydraulic proportional valve 16 operates in its lower position, allowing oil from both the rod-side and rodless-side chambers of the boom cylinder 15 to flow back to the hydraulic tank 1 via the regeneration valve 17 and the electro-hydraulic proportional valve 16, thus achieving the floating function. When both the rod-side and rodless-side chambers of the boom cylinder 15 are connected to the hydraulic tank 1, the boom can float freely according to changes in ground shape or its own weight load, reducing the need for dedicated operator control of the boom.

[0044] When the excavator is idling or not moving, both the main pump second unloading valve 8 and the main pump first unloading valve 20 receive the maximum control current, allowing the main pump to return to the hydraulic oil tank 1 through the unloading valve, which has the effect of saving energy and reducing pressure loss. When the boom starts to move, the unloading valve is in its original position, and all the oil from the main pump enters the system to work.

Claims

1. A boom hydraulic control system, characterized by: The hydraulic control system comprises a main pump one (3), a main pump two (4), a boom one directional valve (6), a controller (13), a boom merging valve (19) and a pilot system, an oil outlet of the main pump one (3) is connected with an oil inlet of the boom merging valve (19), an oil outlet of the main pump two (4) is connected with an oil inlet A of the boom one directional valve (6), a working oil port E of the boom one directional valve (6) and an oil outlet of the boom merging valve (19) are merged and then connected with a rodless cavity of a boom cylinder (15) through a balance maintaining valve (18), a working oil port F of the boom one directional valve (6) is connected with a rod cavity of the boom cylinder (15), the oil outlet of the balance maintaining valve (18) is further connected with the rod cavity of the boom cylinder (15) through an electro-hydraulic proportional valve (16), the controller (13) sends a control signal to the pilot system, and the pilot system is connected with left and right pilot oil ports of the boom one directional valve (6), a pilot oil port of the balance maintaining valve (18) and a pilot oil port of the boom merging valve (19) respectively.

2. The boom hydraulic control system according to claim 1, characterized by: The pilot system comprises a pilot pump (7), a boom lowering proportional valve (9), a boom one lifting proportional valve (10), a boom two lifting proportional valve (11) and a proportional pressure reducing valve (12), an oil outlet of the pilot pump (7) is connected with oil inlets of the boom lowering proportional valve (9), the boom one lifting proportional valve (10), the boom two lifting proportional valve (11) and the proportional pressure reducing valve (12) respectively, an oil outlet of the boom lowering proportional valve (9) is connected with a right pilot oil port of the boom one directional valve (6) and a hydraulic control port of the electro-hydraulic proportional valve (16) respectively, an oil outlet of the boom one lifting proportional valve (10) is connected with a left pilot oil port of the boom one directional valve (6), an oil outlet of the boom two lifting proportional valve (11) is connected with a pilot oil port of the boom merging valve (19), and an oil outlet of the proportional pressure reducing valve (12) is connected with a pilot oil port of the balance maintaining valve (18).

3. The boom hydraulic control system according to claim 1, characterized by: The balance maintaining valve (18) comprises a control valve (181), a valve core (182) and an overload relief valve (183), the working oil port E of the boom one directional valve (6) and the oil outlet of the boom merging valve (19) are merged and then connected with oil inlets of the control valve (181) and the valve core (182) respectively, and an oil outlet of the valve core (182) is connected with the rodless cavity of the boom cylinder (15), the overload relief valve (183) and an oil inlet a of the electro-hydraulic proportional valve (16).

4. The boom hydraulic control system according to claim 3, characterized by: A regenerative valve (17) is arranged between the oil outlet of the valve core (182) and the oil inlet a of the electro-hydraulic proportional valve (16).

5. The boom hydraulic control system according to any one of claims 1 to 4, characterized by: The oil outlet of the main pump one (3) is further connected back to a hydraulic oil tank (1) through a main pump one unloading valve (20).

6. The boom hydraulic control system according to any one of claims 1 to 4, characterized by: The oil outlet of the main pump two (4) is further connected back to the hydraulic oil tank (1) through a main pump two unloading valve (8).

7. The boom hydraulic control system according to any one of claims 1 to 4, characterized by: The oil outlet of the main pump two (4) is further connected with an oil inlet B of the boom one directional valve (6) through a one-way valve (5).

8. An excavator characterized by: The excavator is provided with the boom hydraulic control system according to any one of claims 1-4.

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