Falling Amplitude Hydraulic Control Method, Falling Amplitude Hydraulic Control System and Construction Machinery

Abstract

The present invention relates to the field of hydraulic technology, and provides a falling amplitude hydraulic control method, a falling amplitude hydraulic control system and construction machinery. The above-mentioned falling amplitude hydraulic control method includes: obtaining the pressure value of the rodless cavity of the boom cylinder; when the pressure value is greater than or equal to a preset pressure value, establishing a first control mode for the input current of the electro-hydraulic proportional control valve, wherein the first control mode includes a plurality of first sub-control modes; based on the boom falling amplitude speed selected by the user, selecting the control current of the corresponding first sub-control mode as the input current of the electro-hydraulic proportional control valve. The above-mentioned falling amplitude hydraulic control method solves the problem that the boom falling amplitude speed is not easy to adjust. The falling amplitude hydraulic control method provided by the present invention can select different first sub-control modes according to the needs of the user, and further can adjust the input current of the electro-hydraulic proportional control valve, so that the falling amplitude speed of the boom can be automatically adjusted, realizing the boom falling at different speeds.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulics, and particularly to a falling amplitude hydraulic control method, a falling amplitude hydraulic control system and a construction machinery. Background Art

[0002] The construction machinery uses a hydraulic pilot handle and a hydraulic variable amplitude balance valve to control the boom falling amplitude action, and controls the opening size of the balance valve through the pilot oil provided by the pilot handle. The boom falling amplitude speed is directly reflected by the movement speed of the variable amplitude cylinder. The boom is supported by the variable amplitude cylinder, and the weight of the boom acts completely on the variable amplitude cylinder. Generally, the boom adopts the self-weight falling amplitude method, and the falling amplitude speed is single. During the actual operation process, the operator manipulates the pilot handle to control the falling amplitude speed of the boom. The adjustment of the falling amplitude speed is very challenging to the operator's operation skills. Improper operation is likely to cause problems such as the boom being unable to fall or falling too fast. Summary of the Invention

[0003] The present invention provides a falling amplitude hydraulic control method, a falling amplitude hydraulic control system and a construction machinery, so as to solve the defect that the boom falling amplitude speed is single and difficult to adjust in the prior art.

[0004] The present invention provides a falling amplitude hydraulic control method, including: obtaining the pressure value of the rodless cavity of the variable amplitude cylinder; when the pressure value is greater than or equal to a preset pressure value, establishing a first control mode for the input current of the electro-hydraulic proportional control valve, wherein the first control mode includes a plurality of first sub-control modes; based on the boom falling amplitude speed selected by the user, selecting the control current corresponding to the first sub-control mode as the input current of the electro-hydraulic proportional control valve.

[0005] According to the falling amplitude hydraulic control method provided by the present invention, in the first control mode, the input current of the electro-hydraulic proportional control valve is obtained according to a compensation coefficient, the pressure difference of the rodless cavity of the variable amplitude cylinder and the starting current of the electro-hydraulic proportional control valve.

[0006] According to the falling amplitude hydraulic control method provided by the present invention, the hydraulic control method further includes: when the pressure value is less than the preset pressure value, establishing a second control mode for the input current of the electro-hydraulic proportional control valve, and the maximum control current input to the electro-hydraulic proportional control valve in the second control mode is the starting current.

[0007] According to the falling amplitude hydraulic control method provided by the present invention, the hydraulic control method further includes: when the calculated control current is less than the minimum current during the boom falling amplitude, using the minimum current as the input current of the electro-hydraulic proportional control valve.

[0008] The present invention also provides a lowering hydraulic control system, comprising: a pilot valve, which is connected to a regulated oil source; a first reversing valve, the first pilot end of which is connected to the pilot valve through a first oil passage, an electro-hydraulic proportional control valve being provided on the first oil passage, one working oil port of the first reversing valve being connected to a balance valve, the oil return port of the first reversing valve being connected to a first oil tank, and the electro-hydraulic proportional control valve being used for controlling the spool opening of the balance valve; a luffing cylinder, the rodless cavity of which is connected to the balance valve, and the rod chamber of which is connected to a second oil tank; a pressure sensor, which is arranged in the rodless cavity of the luffing cylinder; and a controller, which controls the input current of the electro-hydraulic proportional control valve according to the pressure value detected by the pressure sensor and the boom lowering speed selected by a user.

[0009] A lowering hydraulic control system according to the present invention further comprises: a solenoid valve, which is arranged on a second oil passage connecting the second pilot end of the first reversing valve and the pilot valve, and the solenoid valve is used for controlling the on-off of the second oil passage.

[0010] A lowering hydraulic control system according to the present invention, the balance valve comprising: a second reversing valve, which is connected to the working oil port of the first reversing valve, the second reversing valve having different working positions to realize the oil inlet or oil return of the rodless cavity of the luffing cylinder; and a first check valve, which is connected in parallel with the second reversing valve.

[0011] A lowering hydraulic control system according to the present invention, the second reversing valve comprising: a second check valve, when the second reversing valve is in a first working position, the oil inlet of the second check valve is connected to the working oil port of the first reversing valve, and the oil outlet of the second check valve is connected to the rodless cavity of the luffing cylinder; and a throttle valve, when the second reversing valve is in a second working position, the oil inlet of the throttle valve is connected to the rodless cavity of the luffing cylinder, and the oil outlet of the throttle valve is connected to the working oil port of the first reversing valve, wherein the electro-hydraulic proportional control valve is used for controlling the spool opening of the throttle valve.

[0012] A lowering hydraulic control system according to the present invention further comprises: a pressure compensation valve, which is connected to the first reversing valve.

[0013] The present invention also provides a construction machinery, comprising the lowering hydraulic control system as described above.

[0014] The boom lowering hydraulic control method provided by the present invention can set the first sub-control mode corresponding to the boom lowering speed, and can select different first sub-control modes according to user needs, and then can adjust the input current of the electro-hydraulic proportional control valve, so that the boom lowering speed can be automatically adjusted, realizing that the boom lowers at different speeds. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0016] Figure 1 is the logic judgment diagram of the boom lowering hydraulic control method provided by the present invention;

[0017] Figure 2 is the schematic diagram of the boom lowering hydraulic control system provided by the present invention;

[0018] Figure 3 is Figure 1 the enlarged view of the balance valve shown in;

[0019] Figure 4 is Figure 1 the enlarged view of the solenoid valve, the first directional control valve and the electro-hydraulic proportional control valve shown in;

[0020] REFERENCE MARKS:

[0021] 10: pilot valve; 20: balance valve; 21: second check valve; 22: throttle valve; 23: first check valve; 30: luffing cylinder; 40: pressure sensor; 50: electro-hydraulic proportional control valve; 60: solenoid valve; 70: first directional control valve; 80: pressure compensation valve; 100: second oil tank; 101: first oil circuit; 102: second oil circuit. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] In order to make the purpose, technical solutions and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the present invention in conjunction with the drawings in the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0023] The terms "first" and "second" in the description and claims of the present invention may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0024] The following will describe Figures 1-4 the boom lowering hydraulic control method, the boom lowering hydraulic control system and the construction machinery of the present invention.

[0025] As Figure 1 shown, an embodiment of the present invention provides a boom lowering hydraulic control method, which specifically includes the following steps:

[0026] Step 01: Obtain the pressure value of the rodless cavity of the luffing cylinder; Step 02: When the pressure value is greater than or equal to the preset pressure value, establish a first control mode for the input current of the electro-hydraulic proportional valve, where the first control mode includes a plurality of first sub-control modes; Step 03: Select the control current of the corresponding first sub-control mode based on the boom lowering speed selected by the user as the input current of the electro-hydraulic proportional valve.

[0027] Specifically, the boom of the construction machinery is installed on the vehicle body, and the boom is driven to move by the movement of the vehicle body. For example, a pump truck folds multiple boom sections and places them on the top of the vehicle body. An aerial work platform shrinks by folding between boom sections and then lands on the vehicle body.

[0028] Taking a crane as an example in the present invention, the length of the crane boom can be changed by the telescoping between multiple boom sections. The base end of the boom is connected to the vehicle body by a pin shaft, and the luffing cylinder 30 is connected between the luffing cylinder hinge point under the boom and the luffing cylinder hinge point on the vehicle body. During the working process, the luffing of the boom is realized by the telescoping of the luffing cylinder 30. When the luffing cylinder 30 extends, the boom is raised; when the luffing cylinder 30 contracts, the boom is lowered.

[0029] During the boom lowering, the boom lowering speed is controlled by the flow rate of the hydraulic oil in the rodless cavity of the luffing cylinder 30. By controlling the opening degree of the spool of the balance valve 20 connected to the rodless cavity, the flow rate of the hydraulic oil in the rodless cavity can be controlled. Further, by controlling the current value input to the electro-hydraulic proportional valve 50, the opening degree of the spool of the balance valve 20 can be controlled. Based on this, in this embodiment, the boom lowering speed is controlled by controlling the current value input to the electro-hydraulic proportional valve 50.

[0030] Further, during the boom lowering process, when the pressure value in the rodless cavity of the luffing cylinder 30 exceeds the preset value, the boom lowering speed will become faster and faster. In response to this situation, a first control mode for the input current of the electro-hydraulic proportional control valve 50 is established, and the first control mode includes multiple first sub-control modes. Specifically, different boom lowering speeds correspond to a preset input current. For different boom lowering speeds, there are different input currents. The input current of the electro-hydraulic proportional control valve 50 corresponding to each boom lowering speed is used as a first sub-control mode. Then, the input current of the electro-hydraulic proportional control valve 50 is controlled according to the control current of the first sub-control mode corresponding to the boom lowering speed selected by the user.

[0031] For example, assume that the lowering angle of the boom is from 75° to 0°, and assume that the normal lowering speed is 1° / s. In this embodiment, each first sub-control mode corresponds to lowering speeds of 1.5° / s, 2° / s, 2.5° / s, 3° / s, etc. Each different lowering speed corresponds to an input current of the electro-hydraulic proportional control valve 50. When the user selects a lowering speed of 2° / s, the controller uses the control current of the preset first sub-control mode corresponding to 2° / s as the input current of the electro-hydraulic proportional control valve 50 to control the valve core opening of the balance valve 20 accordingly.

[0032] Optionally, in the embodiment of the present invention, the preset pressure value can be 30 bar.

[0033] The boom lowering hydraulic control method provided by the embodiment of the present invention can set the first sub-control mode corresponding to the boom lowering speed. It can select different first sub-control modes according to the user's needs, and then adjust the input current of the electro-hydraulic proportional control valve, so that the boom lowering speed can be automatically adjusted, realizing the boom lowering at different speeds.

[0034] Further, in an embodiment of the present invention, the calculation formula of the first control mode is: I x = -K×ΔP + B;

[0035] where, I x is the control current, K is the compensation coefficient, ΔP is the pressure difference in the rodless cavity of the luffing cylinder 30 during the lowering process, and B is the starting current of the electro-hydraulic proportional control valve 50 when the boom starts to lower. Among them, the values of K and B can be set manually. ΔP is a fixed value under the same load, that is, under the same load, regardless of the selected lowering speed, the value of ΔP is equal.

[0036] Specifically, during the boom lowering process, when the pressure P in the rodless cavity of the luffing cylinder 30 is greater than or equal to the preset value, according to the above formula, the control current I xThe value will be less than the starting current, thereby being able to reduce the falling speed of the boom and reduce the impact on the hydraulic system when the boom is falling. Further, in the above formula, △P is a fixed value. When different values are selected for the value of K or the value of B, the control current I x also has multiple values, that is, the first control mode includes multiple first sub-control modes. For example, when K takes K1, I x1 is obtained, and I x1 corresponds to a falling speed, which is a first sub-control mode; when K takes K2, I x2 is obtained, and I x2 corresponds to another falling speed, which is the second first sub-control mode. By setting in this way, multiple falling speeds can be obtained, and thus the stepped control of the boom falling speed is realized. During actual use, the I x value corresponding to each value of K or the value of B can be designed as a gear. During operation, selecting different gears can realize the automatic adjustment of the boom falling speed.

[0037] Optionally, multiple buttons can be set, and each button represents a gear; or a knob can be set, and each rotation position represents a gear; a touch screen can also be set, and the required gear is input on the touch screen. The controller calculates the control current I x according to the calculation formula of the first sub-control mode corresponding to the gear selected by the user, and takes the value of I x as the input current of the electro-hydraulic proportional valve 50, thereby controlling the opening of the balance valve 20.

[0038] Further, if the value of the control current I x calculated according to the above formula is less than the minimum current, at this time, to prevent the boom from not being able to fall, the control current I x input to the electro-hydraulic proportional valve 50 is set to the minimum current at which the boom can fall.

[0039] The falling hydraulic control method provided by the embodiment of the present invention, by setting the first control mode, when the pressure in the rodless cavity of the luffing cylinder gradually increases, the control current input to the electro-hydraulic proportional valve is less than the starting current, reducing the falling speed of the boom and avoiding the impact on the hydraulic control system when the boom is falling.

[0040] As Figure 1 shown, in an embodiment of the present invention, the falling hydraulic control method includes: when the pressure value is less than the preset pressure value, establishing a second control mode for the input current of the electro-hydraulic proportional valve. The calculation formula of the second control mode is:

[0041] I max = B;

[0042] wherein, I max$I_{max}$ is the maximum control current, and $B$ is the starting current.

[0043] Specifically, when the pressure value in the rodless cavity of the luffing cylinder 30 is less than the preset pressure value, the maximum control current input to the electro-hydraulic proportional control valve 50 is the starting current.

[0044] As Figure 2 shown, an embodiment of the present invention further provides a falling amplitude hydraulic control system, including: a pilot valve 10, a balance valve 20, a luffing cylinder 30, a pressure sensor 40, an electro-hydraulic proportional control valve 50, a first reversing valve 70, and a controller. The first pilot end of the first reversing valve 70 is connected to the pilot valve 10 through a first oil passage 101. The electro-hydraulic proportional control valve 50 is arranged on the first oil passage 101. One working oil port of the first reversing valve 70 is connected to the balance valve 20. The oil return port of the first reversing valve 70 is connected to a first oil tank (not shown in the figure). The electro-hydraulic proportional control valve 50 is used to control the valve core opening of the balance valve 20. The rodless cavity of the luffing cylinder 30 is connected to the balance valve 20, and the rod cavity of the luffing cylinder 30 is connected to the second oil tank 100. The pressure sensor 40 is arranged in the rodless cavity of the luffing cylinder 30. The controller controls the input current of the electro-hydraulic proportional control valve 50 according to the pressure value detected by the pressure sensor 40 and the boom falling amplitude speed selected by the user.

[0045] Specifically, the pilot valve 10 is connected to a regulated oil source. The pilot valve 10 and the pilot end of the first reversing valve 70 are connected through the first oil passage 101. The electro-hydraulic proportional control valve 50 is arranged on the first oil passage 101. When the pilot oil enters the pilot end of the first reversing valve 70 through the electro-hydraulic proportional control valve 50, it can cause the first reversing valve 70 to switch its working position, so that the hydraulic oil in the rodless cavity of the luffing cylinder 30 can flow into the first oil tank through the first reversing valve 70. The rodless cavity of the luffing cylinder 30 is connected to the balance valve 20, and the rod cavity of the luffing cylinder 30 is connected to the second oil tank 100.

[0046] During the boom falling amplitude, under the action of the pilot oil, the first reversing valve 70 switches its working position. The first reversing valve 70 is in the middle working position or the lower working position, so that the first oil tank is communicated with the balance valve 20. The rod cavity of the luffing cylinder 30 sucks oil from the second oil tank 100, and the hydraulic oil in the rodless cavity passes through the balance valve 20 and the first reversing valve 70 and enters the first oil tank, realizing the contraction of the hydraulic rod of the luffing cylinder 30, and further realizing the boom falling amplitude. Further, the controller controls the input current input to the electro-hydraulic proportional control valve 50 according to the pressure value detected by the pressure sensor and the boom falling amplitude speed selected by the user, so as to control the valve core opening of the balance valve 20, and further control the hydraulic oil flow rate in the rodless cavity of the luffing cylinder 30, thereby adjusting the boom falling amplitude speed.

[0047] Further, buttons, knobs or touchscreens can be set on the operation panel of the cab of the construction machinery. After the user inputs the lowering speed of the boom, the controller receives the signal and calculates the control current I corresponding to the lowering speed x as the input current of the electro-hydraulic proportional control valve, thereby controlling the spool opening of the balance valve 20.

[0048] Optionally, the electro-hydraulic proportional control valve 50 can be an electro-hydraulic proportional pressure reducing valve or an electro-hydraulic proportional relief valve. In this embodiment, an electro-hydraulic proportional pressure reducing valve is selected.

[0049] The lowering hydraulic control system provided by the embodiment of the present invention connects the electro-hydraulic proportional control valve with the balance valve. The controller controls the input current input to the electro-hydraulic proportional control valve according to the boom lowering speed selected by the user, thereby controlling the spool opening of the balance valve, realizing that the lowering speed can be freely adjusted when the boom is lowered, and realizing that the boom can be lowered at different speeds.

[0050] As Figure 2 shown, in an embodiment of the present invention, the lowering hydraulic control system further includes a solenoid valve 60. The solenoid valve 60 is arranged on the second oil circuit 102 connecting the second pilot end of the first directional control valve 70 and the pilot valve 10. The solenoid valve 60 is used to control the on-off of the second oil circuit 102.

[0051] Specifically, the pilot valve 10 is connected with a pilot handle. By operating the pilot handle left and right, or up and down, the pilot valve 10 can be communicated with the first pilot end of the first directional control valve 70, or with the second pilot end of the first directional control valve 70. In this embodiment, when the boom is lowered, the pilot valve 10 is communicated with the first pilot end of the first directional control valve 70; when the boom is raised, the pilot valve 10 is communicated with the second pilot end of the first directional control valve 70.

[0052] As Figure 4 shown, the solenoid valve 60 has two working positions. When it is in the right working position, the pilot valve 10 is communicated with the second pilot end of the first directional control valve 70, and the first directional control valve 70 switches to the middle working position. The hydraulic oil enters the first directional control valve 70 from the pilot valve 10 and the solenoid valve 60, and flows out from a working oil port of the first directional control valve 70. The hydraulic oil enters the rodless cavity of the luffing cylinder 30 through the balance valve 20, and the hydraulic oil in the rod cavity flows into the second oil tank 100, realizing the elongation of the luffing cylinder 30, and further realizing the raising of the boom.

[0053] Further, in this embodiment, the first directional control valve 70 is a three-position six-way hydraulically controlled directional control valve. The solenoid valve 60 is a two-position three-way solenoid valve.

[0054] As Figure 2As shown in the figure, in an embodiment of the present invention, the balance valve 20 includes: a second reversing valve and a first check valve 23. The first check valve 23 is connected in parallel with the second reversing valve. The second reversing valve is connected to the first reversing valve 70. The second reversing valve has different working positions to realize the oil inlet or oil return of the rodless cavity of the boom cylinder 30.

[0055] Specifically, as Figure 3 shown, the second reversing valve includes: a second check valve 21 and a throttle valve 22. When the second reversing valve is in the first working position, the oil inlet of the second check valve 21 is connected to the working oil port of the first reversing valve 70, and the oil outlet of the second check valve 21 is connected to the rodless cavity of the boom cylinder 30. When the second reversing valve is in the second working position, the oil inlet of the throttle valve 22 is connected to the rodless cavity of the boom cylinder 30, and the oil outlet of the throttle valve 22 is connected to the working oil port of the first reversing valve 70. Among them, the electro-hydraulic proportional control valve 50 is used to control the opening of the spool of the throttle valve 22.

[0056] When the boom is raised, the second reversing valve is in the first working position. At this time, the hydraulic oil flowing out of the working oil port of the first reversing valve 70 enters the rodless cavity of the boom cylinder 30 after passing through the second check valve 21 and the first check valve 23, and the oil in the rod cavity returns, and the boom cylinder 30 extends. When the boom is lowered, the hydraulic oil in the rodless cavity of the boom cylinder 30 passes through the throttle valve 22 and the working oil port of the first reversing valve 70 and enters the first reversing valve 70, and then flows to the first oil tank through the oil return port of the first reversing valve 70. Further, when the boom is lowered, by controlling the control current input to the electro-hydraulic proportional control valve 50, the opening of the spool of the throttle valve 22 can be controlled, so as to realize the adjustment of the boom lowering speed.

[0057] As Figure 2 shown, in an embodiment of the present invention, the hydraulic control system further includes a pressure compensation valve 80, and the pressure compensation valve 80 is connected to the first reversing valve 70.

[0058] The embodiment of the present invention also provides a construction machinery, including a lowering hydraulic control system.

[0059] Specifically, the construction machinery can be a pump truck, an aerial work platform, a crane, etc.

[0060] The construction machinery provided by the embodiment of the present invention realizes that the boom lowering speed can be freely adjusted and can lower the boom at different speeds by setting the lowering hydraulic control system.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. These modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A hydraulic control method for the falling amplitude, characterized in that, Comprising: Obtain the pressure value of the rodless cavity of the luffing cylinder; When the pressure value is greater than or equal to a preset pressure value, establish a first control mode for the input current of the electro-hydraulic proportional control valve, wherein the first control mode includes a plurality of first sub-control modes; Based on the boom lowering speed selected by the user, select the control current corresponding to the selected first sub-control mode as the input current of the electro-hydraulic proportional control valve; When the pressure value is less than the preset pressure value, establish a second control mode for the input current of the electro-hydraulic proportional control valve, and the maximum control current input to the electro-hydraulic proportional control valve in the second control mode is the starting current; In the first control mode, the input current of the electro-hydraulic proportional control valve is obtained according to the compensation coefficient, the pressure difference of the rodless cavity of the luffing cylinder, and the starting current of the electro-hydraulic proportional control valve, wherein, The calculation formula for the first control mode is: I x = -K × △P + B; Among them, I x is the control current, K is the compensation coefficient, △P is the pressure difference in the rodless cavity of the boom cylinder during the falling amplitude process, and B is the starting current of the electro-hydraulic proportional control valve when the boom starts to fall. Among them, the values of K and B can be set artificially, and △P is a fixed value under the same load.

2. The falling amplitude hydraulic control method according to claim 1, characterized in that The hydraulic control method further includes: When the calculated control current is less than the minimum current during boom lowering, use the minimum current as the input current of the electro-hydraulic proportional control valve.

3. The fall amplitude hydraulic control method according to claim 1, characterized in that, The boom lowering hydraulic control method is implemented based on a boom lowering hydraulic control system, wherein the boom lowering hydraulic control system includes: A pilot valve, which is connected to a constant-pressure oil source; A first directional control valve, the first pilot end of the first directional control valve is connected to the pilot valve through a first oil circuit, an electro-hydraulic proportional control valve is arranged on the first oil circuit, a balance valve is connected to one working oil port of the first directional control valve, the oil return port of the first directional control valve is connected to a first oil tank, and the electro-hydraulic proportional control valve is used to control the valve core opening of the balance valve; A luffing cylinder, the rodless cavity of the luffing cylinder is connected to the balance valve, and the rod end cavity of the luffing cylinder is connected to a second oil tank; A pressure sensor, which is arranged in the rodless cavity of the luffing cylinder; A controller, which controls the input current of the electro-hydraulic proportional control valve according to the pressure value detected by the pressure sensor and the boom lowering speed selected by the user.

4. The falling amplitude hydraulic control method according to claim 3, wherein The boom lowering hydraulic control system further includes: A solenoid valve, which is arranged on a second oil circuit connecting the second pilot end of the first directional control valve and the pilot valve, and the solenoid valve is used to control the on-off of the second oil circuit.

5. The falling amplitude hydraulic control method according to claim 3 or 4, characterized in that, The balance valve includes: A second directional control valve, which is connected to the working oil port of the first directional control valve, and the second directional control valve has different working positions to realize the oil inlet or oil return of the rodless cavity of the luffing cylinder; A first check valve, which is connected in parallel with the second directional control valve.

6. The fall amplitude hydraulic control method according to claim 5, characterized in that The second directional control valve includes: A second check valve, when the second directional control valve is in the first working position, the oil inlet of the second check valve is connected to the working oil port of the first directional control valve, and the oil outlet of the second check valve is connected to the rodless cavity of the luffing cylinder; A throttle valve, when the second directional control valve is in the second working position, the oil inlet of the throttle valve is connected to the rodless cavity of the luffing cylinder, and the oil outlet of the throttle valve is connected to the working oil port of the first directional control valve, wherein the electro-hydraulic proportional control valve is used to control the valve core opening of the throttle valve.

7. The falling amplitude hydraulic control method according to claim 3, characterized in that The boom lowering hydraulic control system further includes: A pressure compensation valve, the pressure compensation valve being connected to the first reversing valve.

Images