WO2022252628A1 - 液压控制系统、拖拉机和液压控制方法 - Google Patents

液压控制系统、拖拉机和液压控制方法 Download PDF

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Publication number
WO2022252628A1
WO2022252628A1 PCT/CN2022/071820 CN2022071820W WO2022252628A1 WO 2022252628 A1 WO2022252628 A1 WO 2022252628A1 CN 2022071820 W CN2022071820 W CN 2022071820W WO 2022252628 A1 WO2022252628 A1 WO 2022252628A1
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WIPO (PCT)
Prior art keywords
control valve
electric control
hydraulic
current
valve
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PCT/CN2022/071820
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English (en)
French (fr)
Inventor
张笑
秦浩良
张露云
李思辰
Original Assignee
江苏徐工工程机械研究院有限公司
徐州徐工农业装备科技有限公司
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Application filed by 江苏徐工工程机械研究院有限公司, 徐州徐工农业装备科技有限公司 filed Critical 江苏徐工工程机械研究院有限公司
Priority to BR112022026901A priority Critical patent/BR112022026901A2/pt
Publication of WO2022252628A1 publication Critical patent/WO2022252628A1/zh

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    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01B—SOIL WORKING IN AGRICULTURE OR FORESTRY; PARTS, DETAILS, OR ACCESSORIES OF AGRICULTURAL MACHINES OR IMPLEMENTS, IN GENERAL
    • A01B3/00—Ploughs with fixed plough-shares
    • A01B3/04—Animal-drawn ploughs
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
    • F15B11/04—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed
    • F15B11/046—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed depending on the position of the working member
    • F15B11/048—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed depending on the position of the working member with deceleration control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/08—Servomotor systems without provision for follow-up action; Circuits therefor with only one servomotor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B13/00—Details of servomotor systems ; Valves for servomotor systems
    • F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
    • F15B13/04—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B19/00—Testing; Calibrating; Fault detection or monitoring; Simulation or modelling of fluid-pressure systems or apparatus not otherwise provided for
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D7/00—Control of flow
    • G05D7/06—Control of flow characterised by the use of electric means

Definitions

  • the present disclosure relates to the technical field of agricultural machinery, in particular to a hydraulic control system, a tractor and a hydraulic control method.
  • the pulling machine performs different field operations with the help of different implements.
  • For the lifting control of the implement there are mainly two control systems at present, one is a mechanical lifting system, and the other is an electro-hydraulic suspension system.
  • the electro-hydraulic suspension system has realized the integration of various electronic controls, when the suspension cylinder is lifted with the implement, because the speed suddenly stops, there is no buffer, and there is a problem of stop impact, especially when the engine speed is high and the hydraulic pump is driven. When the output flow is large, a greater impact will be formed.
  • Embodiments of the present disclosure provide a hydraulic control system, a tractor and a hydraulic control method, which can effectively improve the stability of hydraulic cylinder movements.
  • a hydraulic control system comprising:
  • the actuator is connected with the cylinder rod of the hydraulic cylinder;
  • the first electric control valve is arranged on the connection pipeline between the hydraulic pump and the hydraulic cylinder, and the first electric control valve is configured to adjust the flow rate of the connection pipeline;
  • the control device is connected with the signal of the first electric control valve, and the control device is configured to control the maximum input current of the first electric control valve to be a first current value during the rising process of the actuator, and the first current value is at the output flow rate of the hydraulic pump The minimum current required by the first electrically controlled valve to reach the maximum value.
  • the hydraulic control system further includes:
  • the detection device is configured to detect the actual distance between the actuator and the target position during the rising process of the actuator, and the control device is also configured to set the size of the deceleration distance, and the first detection result of the detection device is that the actual distance is greater than the deceleration distance distance, the input current to control the first electronically controlled valve remains at the second current value; and when the actual distance decreases to equal to the deceleration distance, the input current to control the first electronically controlled valve begins to decrease, wherein the deceleration distance is The second current value is equal to or less than the first current value for the moving distance of the element from the start of deceleration to the stop motion.
  • control device is further configured such that when the first detection result of the detection device is that the actual distance is less than or equal to the deceleration distance, the input current for controlling the first electric control valve is first adjusted to the third current value, and then from the first The third current value starts to decrease, the third current value is smaller than the first current value, and the magnitude of the third current value is determined according to the actual distance and the corresponding relationship between distance and current within the deceleration distance.
  • control device is further configured to first reduce the input current of the first electric control valve from the current fourth current value to the fifth current value when the actuator starts to decelerate, and then reduce the first electric current The input current of the control valve starts to decrease from the fifth current value, wherein, when the input current of the first electric control valve is the fourth current value, the flow rate of the hydraulic pump is the same as when the input current of the first electric control valve is the fifth current value When the flow rate of the hydraulic pump is equal.
  • control device is further configured to increase the input current of the first electric control valve to the allowable operating current range of the first electric control valve within a first preset time after starting the first electric control valve within the maximum value, and then reduce the input current of the first electric control valve to the minimum value within the allowable range of the operating current of the first electric control valve within the second preset time, and then make the input current of the first electric control valve The current gradually increases according to the preset function relationship.
  • the hydraulic control system further includes a reversing valve arranged between the first electric control valve and the hydraulic cylinder, the inlet of the reversing valve communicates with the first electric control valve, and the two working ports of the reversing valve are respectively It communicates with the rod cavity and the rodless cavity of the hydraulic cylinder.
  • the hydraulic control system further includes a first relief valve communicated with the rod chamber of the hydraulic cylinder, and the opening pressure of the first relief valve is adjustable.
  • the hydraulic control system further includes a pressure setting device, the pressure setting device is used to set the pressure value of the pressure on the actuator during the descending process, the control device is connected to the pressure setting device with a signal, and the control device is controlled by It is configured to adjust the opening pressure of the first overflow valve according to the pressure value set by the pressure setting device.
  • the hydraulic control system further includes an unloading valve communicated with the connection flow path between the outlet of the hydraulic pump and the first electric control valve, and an unloading valve is provided between the inlet of the unloading valve and the pressure end of the unloading valve
  • the first electric control valve communicates with the spring end of the unloading valve
  • the second damping is provided between the first electric control valve and the spring end of the unloading valve.
  • the first electric control valve includes a two-position three-way control valve, the first working port of the first electric control valve communicates with the hydraulic cylinder, and the second working port of the first electric control valve communicates with the outlet of the hydraulic pump , the third working port of the first electric control valve communicates with the hydraulic fluid tank, when the first electric control valve is in the first working position, the second working port is closed, and the first working port communicates with the third working port; the first electric control valve When the valve is at the second working position, the third working port is closed, and the first working port communicates with the second working port.
  • the hydraulic control system further includes a second electric control valve connected between the rodless chamber of the hydraulic cylinder and the hydraulic fluid tank.
  • a tractor including the hydraulic control system described above.
  • a hydraulic control method based on the above-mentioned hydraulic control system including:
  • the maximum input current for controlling the first electric control valve is the first current value
  • the first current value is the minimum current required by the first electric control valve when the output flow of the hydraulic pump reaches the maximum value.
  • the hydraulic control method further includes:
  • the deceleration distance is the distance traveled by the actuator from the start of deceleration to the stop of motion
  • the hydraulic control method further includes:
  • the input current to control the first electric control valve is first adjusted to the third current value, and then decreases from the third current value, the third current value is smaller than the first current value, And the magnitude of the third current value is determined according to the magnitude of the actual distance and the corresponding relationship between distance and current within the deceleration distance.
  • the hydraulic control method further includes:
  • the hydraulic control method further includes:
  • the input current of the first electric control valve After starting the first electric control valve, increase the input current of the first electric control valve to the maximum value within the allowable range of the operating current of the first electric control valve within the first preset time, and then within the second preset time The input current of the first electronically controlled valve is reduced to the minimum value within the allowable range of the operating current of the first electronically controlled valve, and then the input current of the first electronically controlled valve is gradually increased according to a preset function relationship.
  • the first preset time is 8 milliseconds to 15 milliseconds
  • the second preset time is 10 milliseconds to 15 milliseconds.
  • the hydraulic control method further includes:
  • the control device controls the maximum input current of the first electric control valve to be the minimum current required by the first electric control valve when the output flow of the hydraulic pump reaches the maximum value, thus
  • the advantage of setting is that it can avoid the problem of extra heat generated by the solenoid valve caused by continuing to increase the input current of the first electric control valve after the flow rate of the hydraulic pump reaches saturation.
  • Figure 1 is a schematic diagram of the hysteresis phenomenon of the electronically controlled valve.
  • Fig. 2 is a schematic diagram of the relationship between the input current of the electric control valve and the fluid flow leading to the electric control valve when the flow rate is saturated.
  • Fig. 3 is a hydraulic control schematic diagram of some embodiments of the hydraulic control system of the present disclosure.
  • Fig. 4 is a graph showing the variation relationship between the input current of the first electric control valve and the flow rate of the valve core in some embodiments of the hydraulic control system of the present disclosure.
  • Fig. 5 is a schematic diagram of controlling the input current of the first electric control valve according to the change of the actual distance in some embodiments of the hydraulic control method of the present disclosure.
  • Fig. 6 is a schematic diagram of the input current control of the first electric control valve after the first electric control valve is turned on in some embodiments of the hydraulic control method of the present disclosure.
  • Fig. 7 is a schematic diagram of the input current control of the first relief valve in some embodiments of the hydraulic control method of the present disclosure.
  • the flow rate of the electric control valve changes linearly with the input current, and the absolute value of the slope of the change of the flow rate with the input current is equal, so a2 and a1
  • the difference is the hysteresis value.
  • the change of the flow rate with the input current may have a nonlinear relationship, and the absolute value of the slope of the flow rate of the electronically controlled valve with the change of the input current may also be unequal. Therefore, the hysteresis value of the electronically controlled valve may vary.
  • the inventor also noticed that for control valves, the flow rate of the spool is In the case that the opening degree A of the spool and the pressure difference ⁇ P before and after the valve port remain unchanged, for a fixed flow coefficient ⁇ and mass density ⁇ , the flow rate remains unchanged.
  • the output flow of the hydraulic pump is small, there will be a problem of flow saturation, that is, as the current of the control valve increases, the opening of the spool gradually increases, but the fluid flow to the electric control valve does not change anymore , at this time, the movement speed of the actuator will no longer change.
  • the hydraulic control system includes a hydraulic pump 2, a hydraulic cylinder 11, an actuator 30, a first electric control valve 6 and a control device 12, and the hydraulic cylinder 11 is in fluid communication with the hydraulic pump 2, the actuator 30 is connected to the cylinder rod of the hydraulic cylinder 11, the first electric control valve 6 is arranged on the connecting pipeline between the hydraulic pump 2 and the hydraulic cylinder 11, and the first electric control valve 6 is configured
  • the control device 12 is signal-connected with the first electric control valve 6, and the control device 12 is configured to control the maximum input current of the first electric control valve 6 to be the first current during the rising process of the actuator 30.
  • the first current value is the minimum current required by the first electric control valve 6 when the output flow of the hydraulic pump 2 reaches the maximum value.
  • Another advantage of the above embodiment is that when the actuator 30 starts to decelerate, the output flow of the hydraulic pump 2 can be reduced accordingly after reducing the current of the first electric control valve 6 without hysteresis, which is beneficial to Improve the smoothness of the stop of the actuator 30 when it is raised.
  • the hydraulic control system further includes an engine 1 and a detection device 13, the engine 1 is drivingly connected to the hydraulic pump 2, and the detection device 13 is configured to detect the distance between the actuator 30 and the target position during the rising process of the actuator 30.
  • the actual distance the control device 12 is also configured to set the size of the deceleration distance, and when the first detection result of the detection device 13 is that the actual distance is greater than the deceleration distance, control the input current of the first electric control valve 6 to maintain the second current value ; and when the actual distance decreases to equal the deceleration distance, the input current to control the first electric control valve 6 begins to decrease, wherein the deceleration distance is the distance that the actuator 30 moves from deceleration to stop motion, and the second current value equal to or less than the first current value.
  • the target position is the target position to be reached by the actuator 30, and when the actuator 30 reaches the target position, the actuator 30 will stop moving.
  • the actual distance is the distance between the current position of the actuator 30 and the target position at the time of detection.
  • the first detection refers to the first detection after the detection device 13 is started.
  • the magnitude of the input current of the first electric control valve 6 can be controlled according to the actual distance and the deceleration distance, thereby effectively controlling the output flow of the first electric control valve 6 and further controlling the action speed of the hydraulic cylinder 11.
  • the impact caused by the emergency stop of the hydraulic cylinder 11 when reaching the target position is reduced, and the stability of the hydraulic cylinder 11 is effectively improved.
  • the control device 12 needs to control the first The input current of the electric control valve 6 starts to decrease, so that the cylinder rod stops extending, so that the actuator 30 can stop moving when it reaches the height limit position.
  • the deceleration distance can be set according to the rotational speed of the engine 1, and when the actual distance is greater than the length of the deceleration distance, the input current of the first electric control valve 6 can be maintained at the second current value, With the movement of the cylinder rod, when the actual distance gradually decreases to a length equal to the deceleration distance, the input current for controlling the first electric control valve 6 starts to decrease until it is zero.
  • the actuator 30 can be smoothly stopped when it reaches the target position according to the plan, avoiding the phenomenon of emergency stop and causing damage to the hydraulic cylinder 11. shock.
  • the magnitude of the second current value can be determined according to actual needs.
  • the input current of the first electric control valve 6 may decrease from the second current value, or from other current values.
  • the decreasing gradient of the input current of the first electric control valve 6 can be a fixed gradient or a changing gradient.
  • the input current of the first electric control valve 6 is kept at the maximum flow rate of the hydraulic pump 2
  • the first electronically controlled valve 6 can omit the stage where the flow rate does not change with the decrease of the current, and directly enter the stage where the flow rate does not change with the decrease of the current.
  • the stage where the current decreases and decreases such as making the flow rate and input current linear, improving the controllability of the control process.
  • control device 12 can set the deceleration distance according to the rotation speed of the engine 1 .
  • the rotational speed of the engine 1 will affect the output flow of the hydraulic pump 2 .
  • the output flow of the hydraulic pump 2 can be calculated, and the deceleration distance can be determined according to the output flow of the hydraulic pump 2.
  • control device 12 can set the deceleration distance according to the target position. For example, when the target position is 90% of the maximum stroke of the actuator 30 , the deceleration distance can be set to be 30% of the required motion stroke of the actuator 30 .
  • control device 12 can set the deceleration distance as a fixed value.
  • the hydraulic control system includes the control method of the control device 12 on the input current when it first detects that the actual distance is greater than the deceleration distance, and also includes that the actual distance is reduced to equal to the deceleration distance after the corresponding control measures are adopted.
  • the control method when the size of the control device 12 will be introduced below is, if the detection device 13 detects the actual distance for the first time and finds that the actual distance is less than the deceleration distance, the control device 12 controls the input current.
  • control device 12 is further configured such that when the first detection result of the detection device 13 is that the actual distance is less than or equal to the deceleration distance, the input current for controlling the first electric control valve 6 is first adjusted to the third current value, and then Then decrease from the third current value, the third current value is smaller than the first current value, and the magnitude of the third current value is determined according to the actual distance and the corresponding relationship between distance and current within the deceleration distance.
  • the input current of the first electric control valve 6 can be directly adjusted to the third current value and decreased from the third current value .
  • This setting can control the input current as early as possible before the actual distance decreases to zero, so that the actuator can stop moving smoothly when it reaches the target position.
  • the third current value is smaller than the first current value.
  • the magnitude of the third current value can be determined according to the actual distance and the preset correspondence between the distance between the actuator 30 and the target position within the deceleration distance range and the input current of the first electric control valve 6 . That is to say, if the first detection result shows that the actual distance is less than the deceleration distance, the input current of the first electric control valve 6 is directly adjusted to the preset third current value, which is the same as when the deceleration starts from the position where the actual distance is equal to the deceleration distance. The same deceleration effect enables the actuator 30 to stop moving smoothly.
  • a table can be established in advance for the input current corresponding to different positions within the deceleration distance, and the third current value can be directly obtained by looking up the table. Alternatively, the third current value may also be obtained by calculation.
  • the deceleration distance is c.
  • the actual distance is d1, d1>c, it can be maintained at the second current value first, and then wait until the actual distance is reduced to equal to the deceleration distance. Then start to reduce the control mode.
  • the actual distance is d2, d2 ⁇ c, a control method of adjusting the input current of the first electric control valve 6 to the third current value and decreasing from the third current value can be adopted. The smaller the actual distance d2 is, the smaller the third current value is.
  • the aforementioned hysteresis phenomenon may or may not be considered when setting the magnitudes of the second current value and the third current value.
  • control device 12 is further configured to first reduce the input current of the first electric control valve 6 from the current fourth current value to the fifth current value when the actuator 30 starts to decelerate, and then make the The input current of the first electric control valve 6 starts to decrease from the fifth current value, wherein, when the input current of the first electric control valve 6 is the fourth current value, the flow rate of the hydraulic pump 2 is different from that of the first electric control valve 6 When the input current is the fifth current value, the flow rates of the hydraulic pumps 2 are equal.
  • the difference between the fourth current value and the fifth current value is the hysteresis average value of the first electric control valve 6 .
  • the first electric control valve 6 has an allowable range of operating current, which ranges from A min to A max , where A lim is the corresponding first electric control valve 6 when the flow rate of the hydraulic pump 2 reaches the maximum. minimum input current.
  • control device 12 is further configured to increase the input current of the first electric control valve 6 to the first preset time after the first electric control valve 6 is activated.
  • the advantage of this setting is that the hydraulic cylinder 11 can quickly build up pressure through the rapid increase and decrease of the current, which solves the problem of slow response of the speed control of the hydraulic cylinder 11 under heavy load conditions.
  • the hydraulic control system further includes a reversing valve 8 arranged between the first electric control valve 6 and the hydraulic cylinder 11, the inlet of the reversing valve 8 communicates with the first electric control valve 6, and the reversing valve 8
  • the two working ports of the hydraulic cylinder communicate with the rod cavity and the rodless cavity of the hydraulic cylinder 11 respectively.
  • the outlet of the reversing valve 8 communicates with the hydraulic fluid tank.
  • control device 12 is connected with the control terminal of the reversing valve 8 for signal, and the control device 12 controls the reversing of the reversing valve 8 .
  • the reversing valve 8 is a two-position four-way solenoid valve. When it is in the first working position, the inlet of the reversing valve 8 is connected with the first working port, and the outlet of the reversing valve 8 is connected with the second working port; , the inlet of the reversing valve 8 communicates with the second working port, and the outlet of the reversing valve 8 communicates with the first working port.
  • the first working port of the reversing valve 8 communicates with the rodless chamber of the hydraulic cylinder 11 , and the second working port of the reversing valve 8 communicates with the rodd chamber of the hydraulic cylinder 11 .
  • the hydraulic control system further includes a first overflow valve 10 communicating with the rod cavity of the hydraulic cylinder 11 , and the opening pressure of the first overflow valve 10 is adjustable.
  • the opening pressure of the first relief valve 10 By setting the opening pressure of the first relief valve 10 to be adjustable, the opening pressure of the first relief valve 10 can be adjusted as required, so as to achieve the purpose of controlling the protruding length of the actuator 30 during the descending process.
  • the farthest movement position of the actuator 30 can be adjusted.
  • the sowing depth of the implement can be adjusted to ensure the consistency of the sowing depth, and avoid due to the weight of seeds in the implement during sowing. Changes affect the depth of sowing and affect the quality of sowing.
  • control device 12 is connected with the control terminal of the first overflow valve 10 for signal, and the control device 12 is used to adjust the cracking pressure of the first overflow valve 10 .
  • the inlet of the first overflow valve 10 is in communication with the connection flow path between the rod cavity of the hydraulic cylinder 11 and the second working port of the reversing valve 8, and the outlet of the first overflow valve 10 is in communication with the hydraulic pressure Fluid tank connected.
  • the first relief valve 10 in order to realize the adjustable opening pressure of the first relief valve 10, can be set as an electric proportional relief valve, and the first relief valve can be adjusted by adjusting a given current. 10 cracking pressure.
  • the first relief valve 10 may also be configured as a structure with a manually adjustable cracking pressure, and the cracking pressure may be adjusted through manual operation.
  • the hydraulic control system further includes a pressure setting device 19.
  • the pressure setting device 19 is used to set the pressure value of the pressure on the actuator 30 during the descent process.
  • the control device 12 and the pressure setting device 19 signal connected, the control device 12 is configured to adjust the cracking pressure of the first relief valve 10 according to the pressure value set by the pressure setting device 19 .
  • the user can set the size of the pressure according to the geological layer structure of the ground that the actuator 30 will drill into. For example, when drilling into a hard block (such as a ground with more rocks), the user can Set a larger pressure value so that the actuator 30 can drill under sufficient pressure to avoid drilling failure or drilling depth not meeting the requirements due to too little pressure; while drilling into soft ground, then A smaller pressure value can be set to ensure that the actuator 30 can be drilled to a preset depth, so as to avoid energy waste.
  • a hard block such as a ground with more rocks
  • the pressure setting device 19 the pressure can be set according to the preset drilling depth of the actuator 30, and then the drilling depth of the actuator 30 can be realized by adjusting the opening pressure of the first relief valve 10. Reaching the preset value ensures the consistency of the drilling depth of the actuator 30 .
  • the hydraulic control system further includes an unloading valve 3 in communication with the connection flow path between the outlet of the hydraulic pump 2 and the first electric control valve 6 .
  • an unloading valve 3 By setting the unloading valve 3, constant pressure unloading can be realized.
  • the inlet of the unloading valve 3 communicates with the connection flow path between the outlet of the hydraulic pump 2 and the first electric control valve 6 , and the outlet of the unloading valve 3 communicates with the hydraulic fluid tank.
  • a first damper 4 is provided between the inlet of the unloading valve 3 and the pressure end of the unloading valve 3 .
  • the first electrically controlled valve 6 communicates with the spring end of the unloading valve 3 .
  • the load pressure can be fed back to the unloading valve 3 .
  • a second damper 5 is provided between the first electric control valve 6 and the spring end of the unloading valve 3 .
  • the flow path connected between the first electric control valve 6 and the spring end of the unloading valve 3 can be restricted to stabilize the pressure.
  • the first electric control valve 6 includes a two-position three-way control valve, the first working port of the first electric control valve 6 communicates with the hydraulic cylinder 11, and the second working port of the first electric control valve 6 communicates with the hydraulic cylinder 11.
  • the outlet of the pump 2 is connected, and the third working port of the first electric control valve 6 is connected with the hydraulic fluid tank.
  • the first working port of the first electric control valve 6 communicates with the first working port of the reversing valve 8
  • the first working port of the reversing valve 8 communicates with the rodless chamber of the hydraulic cylinder 11 .
  • control device 12 is in signal communication with the control terminal of the first electric control valve 6 , and the control device 12 controls the switching between different working positions of the first electric control valve 6 .
  • the first electric control valve 6 is an electric proportional control valve.
  • the hydraulic control system further includes a second electric control valve 7 connected between the rodless chamber of the hydraulic cylinder 11 and the hydraulic fluid tank. By setting the second electric control valve 7, the retracting action of the cylinder rod of the hydraulic cylinder 11 can be controlled.
  • control device 12 is in signal communication with the control terminal of the second electric control valve 7 , and the control device 12 controls the switching between different working positions of the second electric control valve 7 .
  • the second electric control valve 7 includes a two-position two-way solenoid valve, the first working port of the second electric control valve 7 communicates with the rodless cavity of the hydraulic cylinder 11, and the second working port of the second electric control valve 7 The working port communicates with the hydraulic fluid tank, the second working port of the second electric control valve 7 also communicates with the third working port of the first electric control valve 6, and the second working port of the second electric control valve 7 also communicates with the unloading valve 3's exit is connected.
  • a second one-way valve 23 is provided between the first working port and the second working port, and the inlet of the second one-way valve 23 is connected to the hydraulic fluid.
  • the tank is connected, and the outlet of the second one-way valve 23 is connected with the rodless chamber of the hydraulic cylinder 11; when the second electric control valve 7 is in the second working position, the first working port is connected with the second working port.
  • the second electric control valve 7 is an electric proportional control valve.
  • the hydraulic control system further includes a second relief valve 9 connected between the reversing valve 8 and the hydraulic fluid tank.
  • the inlet of the second relief valve 9 communicates with the first working port of the reversing valve 8, and the outlet of the second relief valve 9 communicates with the third working port of the first electric control valve 6 and the hydraulic fluid tank.
  • the connection flow path is connected.
  • the hydraulic control system further includes a first one-way valve 22 disposed between the rodless chamber of the hydraulic cylinder 11 and the hydraulic pump 2 .
  • the inlet of the first check valve 22 communicates with the first working port of the reversing valve 8 and the inlet of the second relief valve 9 respectively, and the outlet of the first check valve 22 communicates with the rodless chamber of the hydraulic cylinder 11 and the second electric valve.
  • the first working port of the control valve 7 is connected.
  • the detection device 13 may include an angle sensor, and the angle measured by the angle sensor may be used to convert the actual distance; or, the detection device 13 may include a length sensor, and the actual distance may be directly measured by the length sensor.
  • the hydraulic control system further includes a force sensor 14 in signal connection with the control device 12 , and the control device 12 can obtain the magnitude of the force measured by the force sensor 14 .
  • the force sensor 14 can be used to obtain pulling force information during tillage; in the non-working state, the force sensor 14 can be used to obtain implement weight information.
  • the hydraulic control system further includes a rotational speed detector 21 for detecting the rotational speed of the engine 1 .
  • the control device 12 is signal-connected with the rotational speed detector 21 to obtain the rotational speed of the engine 1 .
  • the present disclosure also provides a tractor, including the above hydraulic control system.
  • the tractor further includes a suspension device connected to the cylinder rod of the hydraulic cylinder 11, and the suspension device is used to connect the work tool.
  • a suspension is used as the actuator 30 .
  • the tractor also includes a work implement connected to the hitch.
  • the suspension device and the work tool together serve as the actuator 30 .
  • control device 12 is also signally connected with the target position setting knob 15, the ascending knob 16, the descending knob 17, the strong pressure trigger 18, the pressure setting device 19 and the height limit setting knob 20, so as to obtain the input data of these knobs , and control the hydraulic control system according to these data.
  • These knobs can also be replaced by buttons or display inputs.
  • the present disclosure also provides a hydraulic control method, including:
  • the maximum input current to control the first electric control valve 6 is the first current value, which is required by the first electric control valve 6 when the output flow of the hydraulic pump 2 reaches the maximum value minimum current.
  • the first electric control valve 6 According to the phenomenon of flow saturation, when the flow rate of the hydraulic pump 2 reaches the maximum and has not reached the maximum flow capacity of the first electric control valve 6, even if the input current of the first electric control valve 6 is increased, the first electric control valve 6 The flow rate will not change anymore, so setting the first current value as the minimum input current of the first electric control valve 6 corresponding to the maximum flow rate of the hydraulic pump 2 can effectively save energy and avoid After the flow rate of 2 reaches saturation, the heat generation problem of the solenoid valve caused by continuing to increase the input current of the first electronically controlled valve 6 can also avoid destroying the relationship between the output flow of the hydraulic pump 2 and the input current of the first electronically controlled valve 6 linear relationship between.
  • the hydraulic control method further includes:
  • the deceleration distance is the distance traveled by the actuator 30 from the start of deceleration to the stop motion
  • the input current of the first electric control valve 6 is controlled to remain at the second current value, and the second current value is equal to or less than the first current value; And when the actual distance decreases to equal to the deceleration distance, the input current for controlling the first electric control valve 6 starts to decrease.
  • the input current of the first electric control valve 6 can be controlled according to the actual distance and the deceleration distance, so as to effectively control the output flow of the first electric control valve 6 and further control the hydraulic pressure.
  • the speed of the action of the cylinder 11 reduces the impact caused by the sudden stop of the hydraulic cylinder 11 when it reaches the target position, and effectively improves the stability of the action of the hydraulic cylinder 11 .
  • the hydraulic control method further includes:
  • the input current to control the first electric control valve 6 is first adjusted to the third current value, and then decreases from the third current value, and the third current value is smaller than the first current value , and the magnitude of the third current value is determined according to the magnitude of the actual distance and the corresponding relationship between distance and current within the deceleration distance.
  • the input current of the first electric control valve 6 can be directly adjusted to the third current value and decreased from the third current value. This setting can control the input current as early as possible before the actual distance decreases to zero, so that the actuator can stop moving smoothly when it reaches the target position.
  • the hydraulic control method further includes:
  • the input current of the first electric control valve 6 is reduced from the current fourth current value to the fifth current value, and then the input current of the first electric control valve 6 is reduced from the fifth current value to the fifth current value.
  • the value begins to decrease, wherein the flow rate of the hydraulic pump 2 when the input current of the first electronically controlled valve 6 is the fourth current value is different from the flow rate of the hydraulic pump 2 when the input current of the first electronically controlled valve 6 is the fifth current value equal.
  • the hydraulic control method further includes:
  • the first electric control valve 6 After starting the first electric control valve 6, increase the input current of the first electric control valve 6 to the maximum value within the allowable range of the operating current of the first electric control valve 6 within the first preset time, and then in the second Reduce the input current of the first electric control valve 6 to the minimum value within the allowable range of the operating current of the first electric control valve 6 within a preset time, and then make the input current of the first electric control valve 6 follow the preset function relationship Gradually increase.
  • the advantage of such setting is that the hydraulic cylinder 11 can quickly build up the pressure through the rapid increase and decrease of the current, so as to solve the problem of the slow response speed of the hydraulic cylinder 11 .
  • the first preset time is 8 milliseconds to 15 milliseconds
  • the second preset time is 10 milliseconds to 15 milliseconds.
  • the hydraulic control method further includes:
  • first overflow valve 10 that communicates with the rod chamber of the hydraulic cylinder 11 and has an adjustable opening pressure
  • the hydraulic cylinder 11 is a rear suspension oil cylinder of the tractor, and the cylinder rod of the oil cylinder is connected with the work tool.
  • the detection device 13 is used to obtain the actual position information of the work tool.
  • the force sensor 14 can obtain pulling force information in the tillage process, and can obtain implement weight information in non-working state.
  • the rotational speed detector 21 is used to detect the rotational speed of the engine 1 , or obtain it from the CAN bus of the engine control device 12 through the CAN protocol.
  • the height limit setting knob 20 is used to set the maximum position limit information of the work tool.
  • the target position setting knob 15 is used to set the depth information of the target position.
  • the pressure setting device 19 is used to set the pressure in the strong pressure mode, and the control device 12 correspondingly controls the relief value of the first relief valve 10 according to the strong pressure.
  • the rising knob 16 , the falling knob 17 and the strong pressure trigger 18 are switch signals, all of which are in signal communication with the control device 12 .
  • the output end of the control device 12 is connected with the control ends of the first electric control valve 6 , the second electric control valve 7 , the reversing valve 8 and the first relief valve 10 .
  • the hydraulic pump 2 is a quantitative pump, the output hydraulic oil of the hydraulic pump 2 is connected to the inlet of the unloading valve 3, the first damper 4 is set at the action end of the unloading valve 3, and the hydraulic pump 2 is connected to the inlet of the first electric control valve 6 Connected, the outlet pressure oil of the first electric control valve 6 is connected with the spring end of the unloading valve 3, and the second damper 5 for buffering the load pressure is set on the first electric control valve 6 and the spring end of the unloading valve 3.
  • the outlet of the first electric control valve 6 is connected to the inlet of the second relief valve 9 after passing through the reversing valve 8 , and at the same time leads to the rodless chamber of the hydraulic cylinder 11 through the first one-way valve 22 .
  • the rodless chamber of the hydraulic cylinder 11 is connected with the inlet of the second electric control valve 7 at the same time, and the rod chamber of the hydraulic cylinder 11 is connected with the inlet of the first overflow valve 10 .
  • the hydraulic control system works as follows:
  • the rising action trigger signal is transmitted to the control device 12, and the control device 12 obtains the information set by the height limit setting knob 20 to determine the highest rising target position, and simultaneously obtains the engine speed information, and represents the speed of the engine 1
  • the rotational speed of the hydraulic pump 2 is input to the control device 12 to determine the oil supply flow rate of the hydraulic pump 2.
  • the control device 12 obtains the current actual position information of the actuator 30 by means of the detection device 13, and determines the difference between the current actual position of the work tool and the height limit position. spacing between.
  • the different voltage signals of the force sensor 14 represent the load of the working tool, and the load of the working tool can be determined.
  • the hydraulic oil output by the hydraulic pump 2 is directly unloaded through the unloading valve 3 .
  • the control device 12 controls the left position of the first electric control valve 6, and the hydraulic pump 2 outputs hydraulic oil through the left position of the first electric control valve 6, and then leads to the reversing valve. 8, and through the first one-way valve 22, enter the rodless chamber of the hydraulic cylinder 11 to realize the rise of the implement.
  • the control device 12 obtains the load information of the working tool by means of the force sensor 14, and determines the slope for controlling the first electric control valve 6 during the current rising process according to the load information.
  • the greater the load the smaller the slope.
  • the rate of change of the current will decrease during the process of increasing the current.
  • the greater the load of the implement the greater the hydraulic pressure required to drive the implement to rise.
  • the control device 12 sets the maximum current A max in a short period of time to make it respond quickly; Decrease the current to the initial opening current A min of the first electronically controlled valve 6, so that it quickly has a small opening; then, further determine the current increase slope in the rising process according to the load relationship of the implement, so that the current gradually increases according to the slope.
  • This control process can ensure the stability of the rising and opening process.
  • the control device 12 can determine the current output flow of the hydraulic pump 2 according to the engine speed information.
  • the opening of the valve port is related, that is, the flow rate and the current are linearly proportional, and the output flow rate of the hydraulic pump 2 is different for different engine speeds.
  • the corresponding maximum limit current A lim can be obtained by looking up the table.
  • the control device 12 will not always set the maximum current A max during the rising process of the given current, so that the electromagnetic coil will not always work at the maximum current, the heat production of the electromagnetic coil will be reduced, and the protection of the electromagnetic valve can be realized. Avoid traffic saturation. Moreover, the entire speed increase process is a linear process.
  • the implement does not actually decelerate. If the current speed of the engine 1 can make the output flow of the hydraulic pump 2 reach the limit The flow rate corresponding to the current A lim , the flow rate of the hydraulic pump 2 starts to decrease from the flow rate corresponding to the A lim . Moreover, the entire current drop process is linearly changed corresponding to the flow control.
  • control device 12 sets the deceleration distance according to the engine speed information. The higher the engine speed, the greater the output flow of the hydraulic pump 2. When the maximum current A lim corresponding to the speed is given, the hydraulic cylinder 11 will move faster, and a longer deceleration distance is required to ensure a smooth stop.
  • the control device 12 determines the actual actual distance between the current actual position and the height limit position according to the actual position of the hydraulic cylinder 11 detected by the detection device 13 and the value of the target position set by the height limit setting knob 20 d.
  • the first electric control valve 6 is set according to the A lim current, and when the actual distance d reaches the set deceleration distance c, the deceleration starts; If the actual distance d is d2 during the first detection, and d2 is smaller than the size of the speed range c, the corresponding limit current within the deceleration distance is directly given, and deceleration starts.
  • the hydraulic control system provided by this disclosure adopts hysteresis compensation measures, that is, according to the change curve of the first electric control valve 6 tested in advance, the hysteresis average value e is determined, and after the deceleration distance is reached, the control device 12 directly adjusts the current to A lim -e, and then start to decelerate according to a certain slope, the speed is easy to control, the deceleration distance is sufficient, and the relationship between efficiency and stability is taken into account.
  • the control device 12 controls the second electric control valve 7 to move to the left position, and the hydraulic oil in the rodless chamber of the hydraulic cylinder 11 directly flows from the left position of the second electric control valve 7 to the The hydraulic fluid tank allows the work tool to be lowered.
  • the control device 12 acquires the signal of the strong pressure trigger 18, the control device 12 controls the cracking pressure of the first relief valve 10 according to the set value of the pressure setting device 19 and the corresponding curve of pressure and current as shown in FIG. adjust.
  • the control device 12 controls the left position action of the second electric control valve 7, the control device 12 simultaneously controls the left position action of the first electric control valve 6 and the reversing valve 8, and the hydraulic pump 2 outputs
  • the hydraulic oil enters the rod cavity of the hydraulic cylinder 11, and the implement is driven down under the action of the hydraulic oil, and enters the soil under the set overflow pressure.
  • Different overflow pressures can be set for different terrains. When the ground panel is hard or the ground is hard, set a small current to ensure that the machine will enter the soil under a large pressure.
  • the strong pressure mode is released.
  • the depth of their own soil penetration basically depends on their own weight. In order to ensure the required depth of sowing, with the help of different set pressures, you can Ensure the consistency of plowing depth.
  • the current first increases rapidly with a relatively large slope, so that the first electric control valve responds quickly, and then the current drops to the opening point of the first electric control valve, so that the pressure in the rodless chamber of the hydraulic cylinder of the implement is quickly established. And according to different machine loads, set different slopes to change the speed, so as to ensure that the rising start is stable;
  • the outlet of the rod chamber of the hydraulic cylinder is equipped with a first relief valve with adjustable opening pressure.
  • the strong pressure function can be triggered according to different soil properties and terrains.
  • By adjusting the set pressure of the first relief valve it can be used for different Different implements and terrains can be used to control the depth of different implements, and overcome the problem of different depths caused by the constant change of the weight of the implements.

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Abstract

本公开涉及一种液压控制系统、拖拉机和液压控制方法，其中液压控制系统包括液压泵、液压缸、执行元件、第一电控阀和控制装置，液压缸与液压泵流体连通，执行元件与液压缸的缸杆连接，第一电控阀设置于液压泵和液压缸之间的连接管路上，第一电控阀被配置为调节连接管路的通流量，控制装置与第一电控阀信号连接，控制装置被配置为在执行元件上升过程中控制第一电控阀的最大输入电流为第一电流值，第一电流值为在液压泵的输出流量达到最大值时第一电控阀所需要的最小电流。

Description

液压控制系统、拖拉机和液压控制方法
本申请是以中国申请号为202111675837.2，申请日为2021年12月31日的申请为基础，并主张其优先权，该中国申请的公开内容在此作为整体引入本申请中。
技术领域
本公开涉及农业机械技术领域，尤其涉及一种液压控制系统、拖拉机和液压控制方法。
背景技术
拉机借助于不同机具进行不同的田间工况作业。对于机具的提升控制，目前主要有两种控制系统，一种是机械式提升系统，另一种是电液悬挂系统。
对于机械式提升系统来说，其传递结构复杂，机构间的摩擦损耗较大，杆件传递过程和弹性元件的反应动作迟滞，控制阀的开关控制存在较多限制，使其不能实现对耕作的精细控制，操作者操作复杂，劳动强度大。
而电液悬挂系统虽然实现了各种电控化融合，但是悬挂油缸在带有机具上升时，由于速度突然停止，没有缓冲，存在停止冲击问题，尤其在发动机转速较高，并驱动液压泵的输出流量较大时，会形成更大冲击。
需要说明的是，公开于本公开背景技术部分的信息仅仅旨在增加对本公开的总体背景的理解，而不应当被视为承认或以任何形式暗示该信息构成已为本领域技术人员所公知的现有技术。
发明内容
本公开实施例提供一种液压控制系统、拖拉机和液压控制方法，可以有效提高液压缸动作的平稳性。
根据本公开的第一个方面，提供一种液压控制系统，包括：
液压泵；
液压缸，与液压泵流体连通；
执行元件，与液压缸的缸杆连接；
第一电控阀，设置于液压泵和液压缸之间的连接管路上，第一电控阀被配置为调 节连接管路的通流量；和
控制装置，与第一电控阀信号连接，控制装置被配置为在执行元件上升过程中控制第一电控阀的最大输入电流为第一电流值，第一电流值为在液压泵的输出流量达到最大值时第一电控阀所需要的最小电流。
在一些实施例中，液压控制系统还包括：
发动机，与液压泵驱动连接；和
检测装置，被配置为在执行元件上升过程中检测执行元件与目标位置之间的实际距离，控制装置还被配置为设定减速距离的大小，并在检测装置的首次检测结果为实际距离大于减速距离时，控制第一电控阀的输入电流保持在第二电流值；且在实际距离减小至等于减速距离时，控制第一电控阀的输入电流开始减小，其中，减速距离为执行元件从开始减速到停止运动所运动的距离，第二电流值等于或小于第一电流值。
在一些实施例中，控制装置还被配置为在检测装置的首次检测结果为实际距离小于或等于减速距离时，控制第一电控阀的输入电流先调节至第三电流值，然后再从第三电流值开始减小，第三电流值小于第一电流值，且第三电流值的大小根据实际距离的大小和在减速距离内距离与电流的对应关系确定。
在一些实施例中，控制装置还被配置为在执行元件开始减速时，先将第一电控阀的输入电流从当前的第四电流值减小至第五电流值，然后再使第一电控阀的输入电流从第五电流值开始减小，其中，在第一电控阀的输入电流为第四电流值时液压泵的流量与在第一电控阀的输入电流为第五电流值时液压泵的流量相等。
在一些实施例中，控制装置还被配置为在启动第一电控阀后，在第一预设时间内将第一电控阀的输入电流增大至第一电控阀的工作电流允许范围内的最大值，然后在第二预设时间内将第一电控阀的输入电流减小至第一电控阀的工作电流允许范围内的最小值，然后再使第一电控阀的输入电流按照预设函数关系逐渐增大。
在一些实施例中，液压控制系统还包括设置于第一电控阀和液压缸之间的换向阀，换向阀的进口与第一电控阀连通，换向阀的两个工作口分别与液压缸的有杆腔和无杆腔连通。
在一些实施例中，液压控制系统还包括与液压缸的有杆腔连通的第一溢流阀，且第一溢流阀的开启压力大小可调。
在一些实施例中，液压控制系统还包括压力设定装置，压力设定装置用于设定执行元件在下降过程中所受到压力的压力值，控制装置与压力设定装置信号连接，控制 装置被配置为根据压力设定装置所设定的压力值调节第一溢流阀的开启压力。
在一些实施例中，液压控制系统还包括与液压泵的出口和第一电控阀之间的连接流路连通的卸荷阀，卸荷阀的进口和卸荷阀的压力端之间设有第一阻尼，第一电控阀与卸荷阀的弹簧端连通，且第一电控阀与卸荷阀的弹簧端之间设有第二阻尼。
在一些实施例中，第一电控阀包括二位三通控制阀，第一电控阀的第一工作口与液压缸连通，第一电控阀的第二工作口与液压泵的出口连通，第一电控阀的第三工作口与液压流体箱连通，第一电控阀在第一工作位时，第二工作口关闭，第一工作口与第三工作口连通；第一电控阀在第二工作位时，第三工作口关闭，第一工作口与第二工作口连通。
在一些实施例中，液压控制系统还包括第二电控阀，第二电控阀连接于液压缸的无杆腔和液压流体箱之间。
根据本公开的第二个方面，提供一种拖拉机，包括上述的液压控制系统。
根据本公开的第三个方面，提供一种基于上述的液压控制系统的液压控制方法，包括：
在执行元件上升过程中，控制第一电控阀的最大输入电流为第一电流值，第一电流值为在液压泵的输出流量达到最大值时第一电控阀所需要的最小电流。
在一些实施例中，液压控制方法还包括：
提供与液压泵驱动连接的发动机；
设定减速距离的大小，减速距离为执行元件从开始减速到停止运动所运动的距离；
在执行元件上升过程中，检测执行元件与目标位置之间的实际距离；和
比较实际距离和减速距离的大小，在首次检测结果为实际距离大于减速距离时，控制第一电控阀的输入电流保持在第二电流值，第二电流值等于或小于第一电流值；并在实际距离减小至等于减速距离时，控制第一电控阀的输入电流开始减小。
在一些实施例中，液压控制方法还包括：
在首次检测结果为实际距离小于减速距离时，控制第一电控阀的输入电流先调节至第三电流值，然后再从第三电流值开始减小，第三电流值小于第一电流值，且第三电流值的大小根据实际距离的大小和在减速距离内距离与电流的对应关系确定。
在一些实施例中，液压控制方法还包括：
在执行元件开始减速时，先将第一电控阀的输入电流从当前的第四电流值减小至 第五电流值，然后再使第一电控阀的输入电流从第五电流值开始减小，其中，在第一电控阀的输入电流为第四电流值时液压泵的流量与在第一电控阀的输入电流为第五电流值时液压泵的流量相等。
在一些实施例中，液压控制方法还包括：
在启动第一电控阀后，在第一预设时间内将第一电控阀的输入电流增大至第一电控阀的工作电流允许范围内的最大值，然后在第二预设时间内将第一电控阀的输入电流减小至第一电控阀的工作电流允许范围内的最小值，然后再使第一电控阀的输入电流按照预设函数关系逐渐增大。
在一些实施例中，第一预设时间为8毫秒至15毫秒，第二预设时间为10毫秒至15毫秒。
在一些实施例中，液压控制方法还包括：
提供与液压缸的有杆腔连通且开启压力大小可调的第一溢流阀；
在执行元件在重力和液压缸的驱动力共同作用下钻入预设物体内部时，先设定执行元件在下降过程中所受到压力的压力值，然后根据所设定的压力值调节第一溢流阀的开启压力的大小。
基于上述技术方案，本公开实施例在执行元件上升过程中，控制装置控制第一电控阀的最大输入电流为液压泵的输出流量达到最大值时第一电控阀所需要的最小电流，这样设置的好处是，可以避免在液压泵的流量达到饱和后由于继续增大第一电控阀的输入电流而带来的电磁阀额外产热问题。
通过以下参照附图对本公开的示例性实施例的详细描述，本公开的其它特征及其优点将会变得清楚。
附图说明
为了更清楚地说明本公开实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本公开的实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据提供的附图获得其他的附图。
图1为电控阀的滞环现象示意图。
图2为流量饱和时电控阀的输入电流和通往电控阀的流体流量之间的变化关系示意图。
图3为本公开液压控制系统一些实施例的液压控制原理图。
图4为本公开液压控制系统一些实施例中第一电控阀的输入电流和其阀芯通流流量之间的变化关系图。
图5为本公开液压控制方法一些实施例中随实际距离的大小变化对第一电控阀的输入电流进行控制的原理图。
图6为本公开液压控制方法一些实施例中开启第一电控阀后对第一电控阀的输入电流控制原理图。
图7为本公开液压控制方法一些实施例中第一溢流阀的输入电流控制原理图。
具体实施方式
下面将结合本公开实施例中的附图，对实施例中的技术方案进行清楚、完整地描述。显然，所描述的实施例仅仅是本公开的一部分实施例，而不是全部的实施例。基于本公开的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本公开保护的范围。
在本公开的描述中，需要理解的是，术语“中心”、“横向”、“纵向”、“前”、“后”、“左”、“右”、“上”、“下”、“竖直”、“水平”、“顶”、“底”、“内”、“外”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本公开和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本公开保护范围的限制。
针对相关技术中机械式提升系统和电液悬挂系统存在的问题，发明人进行了大量的研究，并且发现在电控阀的电流增大过程中，会存在滞环现象。
如图1所示，对于电控阀来说，随着电流的增大，电控阀的阀口开度逐渐增大，对应的阀芯通流流量也会逐渐增大。但是，当电流开始减小时，流量并未直接减小，而是在电流减小到一定值之后，流量才开始减小，即对于相同的流量下，增大过程和减小过程对应的电流会存在一个差值，该差值即是该电控阀的滞环大小。
在图1所示的实施例中，在电流增大和减小过程中，电控阀的通流流量随输入电流呈线性变化，且流量随输入电流变化的斜率绝对值相等，因此a2与a1的差值即为滞环值。而在其他实施例中，在电流增大和减小过程中，通流流量随输入电流的变化可能为非线性关系，电控阀的通流流量随输入电流变化的斜率绝对值也可能不相等，因此电控阀的滞环值可能是变化的。
另外，发明人还注意到，对于控制阀类，阀芯的通流流量为
Figure PCTCN2022071820-appb-000001
在阀芯的开口度A及阀口的前后压差ΔP均保持不变的情况下，对于固定的流量系数α及质量密度ρ，通流流量不变。但是，当液压泵的输出流量较小时，则会出现流量饱和的问题，即随着控制阀的电流增大，阀芯的开口度逐渐增大，但通往电控阀的流体流量不再变化，此时，执行元件的运动速度也不再变化。
如图2所示，随着电控阀的电流增大，阀口逐渐增大，通往电控阀的流量也不断增大。但是，当电流继续增大导致阀芯的开口度继续增大时，由于液压泵的输入流量不变，不能满足电控阀的通流需求，则随着电流增大，通过电控阀的流量不再增加。电流从a1增大到a2的过程即是流量饱和过程，在该过程中，虽然控制电流的大小还在变化，但是执行元件的运动速度不再变化。
基于以上研究，发明人对液压控制系统进行了改进。
如图3所示，在本公开提供的液压控制系统的一些实施例中，该液压控制系统包括液压泵2、液压缸11、执行元件30、第一电控阀6和控制装置12，液压缸11与液压泵2流体连通，执行元件30与液压缸11的缸杆连接，第一电控阀6设置于液压泵2和液压缸11之间的连接管路上，第一电控阀6被配置为调节连接管路的通流量，控制装置12与第一电控阀6信号连接，控制装置12被配置为在执行元件30上升过程中控制第一电控阀6的最大输入电流为第一电流值，第一电流值为在液压泵2的输出流量达到最大值时第一电控阀6所需要的最小电流。
根据流量饱和现象，在液压泵2的流量达到最大时，且未达到第一电控阀6的最大通流能力时，即使增大第一电控阀6的输入电流，第一电控阀6的通流流量也不会再发生变化，因此将第一电流值设置为液压泵2的流量达到最大时对应的第一电控阀6的最小输入电流，可以有效节约能源，同时避免在液压泵2的流量达到饱和后由于继续增大第一电控阀6的输入电流而带来的电磁阀额外产热问题。
上述实施例的另一好处是，在执行元件30开始减速时，在减小第一电控阀6的电流后可以使液压泵2的输出流量随之减小，而不会出现滞后，有利于提高执行元件30在上升时停止的平稳性。
在一些实施例中，液压控制系统还包括发动机1和检测装置13，发动机1与液压泵2驱动连接，检测装置13被配置为在执行元件30上升过程中检测执行元件30与目标位置之间的实际距离，控制装置12还被配置为设定减速距离的大小，并在检测 装置13的首次检测结果为实际距离大于减速距离时，控制第一电控阀6的输入电流保持在第二电流值；且在实际距离减小至等于减速距离时，控制第一电控阀6的输入电流开始减小，其中，减速距离为执行元件30从开始减速到停止运动所运动的距离，第二电流值等于或小于第一电流值。
其中，目标位置为执行元件30所要到达的目的位置，执行元件30到达目标位置时，执行元件30便会停止运动。实际距离为检测时执行元件30的当前位置与目标位置之间的距离。首次检测指的是检测装置13启动后的第一次检测。
通过设定减速距离，可以根据实际距离与减速距离的大小控制第一电控阀6的输入电流的大小，从而有效控制第一电控阀6的输出流量，进而控制液压缸11动作的速度，减少液压缸11在到达目标位置时出现急停而造成的冲击，有效提高液压缸11动作的平稳性。
比如，在一些实施例中，在液压缸11的缸杆伸出并带动执行元件30做沿竖直方向的上升运动时，在执行元件30即将到达限高位置时，控制装置12需要控制第一电控阀6的输入电流开始减小，以便使缸杆停止伸出，使执行元件30在到达限高位置时能够停止运动。采用本公开提供的液压控制系统实施例，则可以根据发动机1的转速设置减速距离，在实际距离大于减速距离的长度时，可以使第一电控阀6的输入电流保持在第二电流值，而随着缸杆的运动，在实际距离的大小逐渐减小并且减小至等于减速距离的长度时，控制第一电控阀6的输入电流开始减小，直至为零。通过预先设置减速距离，并对第一电控阀6的输入电流进行相应控制，可以使执行元件30能够按照计划在到达目标位置时平稳地停止运动，避免出现急停现象，对液压缸11造成冲击。
在上述实施例中，第二电流值的大小可以根据实际需要来确定。当实际距离的大小逐渐减小并且减小至等于减速距离的长度时，第一电控阀6的输入电流可以从第二电流值开始减小，也可以从其他电流值开始减小。第一电控阀6的输入电流的减小梯度可以为固定梯度，也可以为变化的梯度。
而且，在第二电流值等于第一电流值时，即，在检测装置13首次检测到的实际距离大于减速距离时，将第一电控阀6的输入电流保持在液压泵2的流量达到最大时对应的第一电控阀6的最小输入电流，那么在电流开始减小时，可以使第一电控阀6省略通流流量随电流减小不发生变化的阶段，而直接进入通流流量随电流减小而减小的阶段，比如使通流流量和输入电流呈线性关系，改善控制过程的可操控性。
在一些实施例中，控制装置12可以根据发动机1的转速设定减速距离的大小。发动机1的转速大小会影响液压泵2的输出流量的大小。根据发动机1的转速，可以计算液压泵2的输出流量，并根据液压泵2的输出流量确定减速距离的大小。
在一些实施例中，控制装置12可以根据目标位置设定减速距离的大小。比如，目标位置为执行元件30的最大行程的90％时，可以设定减速距离为执行元件30所需运动行程的30％。
在一些实施例中，控制装置12可以将减速距离的大小设置为固定值。
在上述一些实施例中，液压控制系统包含了先检测到实际距离大于减速距离时控制装置12对输入电流的控制方式，也包含了在采用了相应的控制措施后实际距离减小至等于减速距离的大小时的控制方式，下面将要介绍的是，如果检测装置13首次检测实际距离时即发现实际距离小于减速距离时，控制装置12对输入电流的控制方式。
在一些实施例中，控制装置12还被配置为在检测装置13的首次检测结果为实际距离小于或等于减速距离时，控制第一电控阀6的输入电流先调节至第三电流值，然后再从第三电流值开始减小，第三电流值小于第一电流值，且第三电流值的大小根据实际距离的大小和在减速距离内距离与电流的对应关系确定。
在检测装置13首次检测实际距离的大小时即检测到实际距离小于减速距离的结果时，可以直接将第一电控阀6的输入电流调节至第三电流值并从第三电流值开始减小。这样设置可以在实际距离减小为零之前尽可能早地对输入电流进行控制，实现执行元件在到达目标位置时能够平稳停止运动的目的。
其中，第三电流值小于第一电流值。第三电流值的大小可以根据实际距离的大小和预先设定的在减速距离范围内执行元件30与目标位置之间的距离和第一电控阀6的输入电流之间的对应关系来确定。也就是说，如果首次检测结果为实际距离小于减速距离，则直接将第一电控阀6的输入电流调节至预设的第三电流值，达到与从实际距离等于减速距离的位置开始减速时相同的减速效果，使得执行元件30能够平稳停止运动。
设定减速距离后，在减速距离内不同位置对应的输入电流大小可以预先建立表格，第三电流值可以直接通过查表获得。或者，第三电流值也可以通过计算方式获得。
如图4所示，减速距离的大小为c，当实际距离为d1时，d1>c，可以采用先保持在第二电流值，然后等到实际距离的大小减小至等于减速距离的大小时，再开始减小 的控制方式。当实际距离为d2时，d2<c，可以采用将第一电控阀6的输入电流调节至第三电流值并从第三电流值开始减小的控制方式。实际距离d2的值越小，第三电流值的大小越小。
在上述各个实施例中，在设定第二电流值和第三电流值的大小时可以考虑上述的滞环现象，也可以不考虑上述的滞环现象。
在一些实施例中，控制装置12还被配置为在执行元件30开始减速时，先将第一电控阀6的输入电流从当前的第四电流值减小至第五电流值，然后再使第一电控阀6的输入电流从第五电流值开始减小，其中，在第一电控阀6的输入电流为第四电流值时液压泵2的流量与在第一电控阀6的输入电流为第五电流值时液压泵2的流量相等。
第四电流值和第五电流值的差值为第一电控阀6的滞环平均值。
根据如图1所示的滞环现象可以看出，在第一电控阀6的输入电流开始减小时，会有一段即使输入电流减小，通流流量也仍保持不变的阶段。在上述实施例中，通过先将第一电控阀6的输入电流从第四电流值a2减小至第五电流值a1，然后再使第一电控阀6的输入电流从第五电流值a1开始减小，可以使第一电控阀6省略即使输入电流减小，通流流量也仍保持不变的阶段，并直接进入通流流量随输入电流的减小而减小的阶段，比如使通流流量和输入电流呈线性关系，有效提高操作的方便性和灵敏性。
如图5所示，第一电控阀6具有工作电流的允许范围，该范围为A min至A max，其中，A lim为在液压泵2的流量达到最大时对应的第一电控阀6的最小输入电流。
如图6所示，在一些实施例中，控制装置12还被配置为在启动第一电控阀6后，在第一预设时间内将第一电控阀6的输入电流增大至第一电控阀6的工作电流允许范围内的最大值，然后在第二预设时间内将第一电控阀6的输入电流减小至第一电控阀6的工作电流允许范围内的最小值，然后再使第一电控阀6的输入电流按照预设函数关系逐渐增大。
这样设置的好处是，可以通过电流的快速增大和快速减小使液压缸11快速建立起压力，解决液压缸11在重载工况下速度控制响应慢的问题。
在一些实施例中，液压控制系统还包括设置于第一电控阀6和液压缸11之间的换向阀8，换向阀8的进口与第一电控阀6连通，换向阀8的两个工作口分别与液压缸11的有杆腔和无杆腔连通。换向阀8的出口与液压流体箱连通。
在一些实施例中，控制装置12与换向阀8的控制端信号连接，控制装置12控制 换向阀8的换向。
换向阀8为二位四通电磁阀，在第一工作位时，换向阀8的进口与第一工作口连通，换向阀8的出口与第二工作口连通；在第二工作位时，换向阀8的进口与第二工作口连通，换向阀8的出口与第一工作口连通。换向阀8的第一工作口与液压缸11的无杆腔连通，换向阀8的第二工作口与液压缸11的有杆腔连通。
在一些实施例中，液压控制系统还包括与液压缸11的有杆腔连通的第一溢流阀10，且第一溢流阀10的开启压力大小可调。
通过将第一溢流阀10的开启压力大小设置为可调，可以根据需要调节第一溢流阀10的开启压力的大小，从而实现控制执行元件30在下降过程中伸出长度的目的。
通过调节第一溢流阀10的开启压力的大小，可以调节执行元件30的最远运动位置。比如，执行元件30为拖拉机的播种机具时，通过调节第一溢流阀10的开启压力的大小，可以调节机具的播种深度，保证播种深度的一致性，避免由于播种过程中机具内种子的重量变化而影响播种的深度，影响播种质量。
如图7所示，控制装置12输入给第一溢流阀10的控制端的电流越大，第一溢流阀10的开启压力越小。
在一些实施例中，控制装置12与第一溢流阀10的控制端信号连接，控制装置12用于调节第一溢流阀10的开启压力的大小。
在一些实施例中，第一溢流阀10的进口与液压缸11的有杆腔和换向阀8的第二工作口之间的连接流路连通，第一溢流阀10的出口与液压流体箱连通。
在一些实施例中，为了实现第一溢流阀10的开启压力可调，可以将第一溢流阀10设置为电比例溢流阀，通过调节给定的电流大小来调节第一溢流阀10的开启压力。
在另一些实施例中，也可以将第一溢流阀10设置为手动可调开启压力的结构，通过手动操作实现对开启压力的调节。
在一些实施例中，液压控制系统还包括压力设定装置19，压力设定装置19用于设定执行元件30在下降过程中所受到压力的压力值，控制装置12与压力设定装置19信号连接，控制装置12被配置为根据压力设定装置19所设定的压力值调节第一溢流阀10的开启压力。
通过设置压力设定装置19，使用者可以根据执行元件30所要钻入的地面的地质层结构来设定压力的大小，比如在钻入硬质地块(比如岩石较多的地面)时，可以设定较大的压力值，使得执行元件30在足够的压力下钻入，避免因压力太小而钻入失 败或者钻入深度达不到要求；而在钻入地质较软的土地时，则可以设定较小的压力值，保证执行元件30能够钻入至预设深度即可，避免能量浪费。
而且，通过设置压力设定装置19，可以根据预先设定的执行元件30的钻入深度来设定压力的大小，再通过调节第一溢流阀10的开启压力实现执行元件30的钻入深度达到预先设定值，保证执行元件30钻入深度的一致性。
在一些实施例中，液压控制系统还包括与液压泵2的出口和第一电控阀6之间的连接流路连通的卸荷阀3。通过设置卸荷阀3，可以实现定压卸荷。
在一些实施例中，卸荷阀3的进口与液压泵2的出口和第一电控阀6之间的连接流路连通，卸荷阀3的出口与液压流体箱连通。
在一些实施例中，卸荷阀3的进口和卸荷阀3的压力端之间设有第一阻尼4。通过设置第一阻尼4，可以实现稳定卸荷，微开口动作平稳。
在一些实施例中，第一电控阀6与卸荷阀3的弹簧端连通。通过将第一电控阀6与卸荷阀3的弹簧端连通，可以将负载压力反馈至卸荷阀3。
在一些实施例中，第一电控阀6与卸荷阀3的弹簧端之间设有第二阻尼5。通过设置第二阻尼5，可以对第一电控阀6与卸荷阀3的弹簧端之间的连接流路进行限流，起到稳压作用。
在一些实施例中，第一电控阀6包括二位三通控制阀，第一电控阀6的第一工作口与液压缸11连通，第一电控阀6的第二工作口与液压泵2的出口连通，第一电控阀6的第三工作口与液压流体箱连通，第一电控阀6在第一工作位时，第二工作口关闭，第一工作口与第三工作口连通；第一电控阀6在第二工作位时，第三工作口关闭，第一工作口与第二工作口连通。
在一些实施例中，第一电控阀6的第一工作口与换向阀8的第一工作口连通，换向阀8的第一工作口与液压缸11的无杆腔连通。
在一些实施例中，控制装置12与第一电控阀6的控制端信号连通，控制装置12控制第一电控阀6的不同工作位之间的换向。
在一些实施例中，第一电控阀6为电比例控制阀。
在一些实施例中，液压控制系统还包括第二电控阀7，第二电控阀7连接于液压缸11的无杆腔和液压流体箱之间。通过设置第二电控阀7，可以对液压缸11缸杆的收回动作进行控制。
在一些实施例中，控制装置12与第二电控阀7的控制端信号连通，控制装置12 控制第二电控阀7的不同工作位之间的换向。
在一些实施例中，第二电控阀7包括二位二通电磁阀，第二电控阀7的第一工作口与液压缸11的无杆腔连通，第二电控阀7的第二工作口与液压流体箱连通，第二电控阀7的第二工作口还与第一电控阀6的第三工作口连通，第二电控阀7的第二工作口还与卸荷阀3的出口连通。
在一些实施例中，第二电控阀7在第一工作位时，第一工作口和第二工作口之间设有第二单向阀23，第二单向阀23的进口与液压流体箱连通，第二单向阀23的出口与液压缸11的无杆腔连通；第二电控阀7在第二工作位时，第一工作口和第二工作口连通。
在一些实施例中，第二电控阀7为电比例控制阀。
在一些实施例中，液压控制系统还包括第二溢流阀9，第二溢流阀9连接于换向阀8和液压流体箱之间。
在一些实施例中，第二溢流阀9的进口与换向阀8的第一工作口连通，第二溢流阀9的出口与第一电控阀6的第三工作口和液压流体箱的连接流路连通。
在一些实施例中，液压控制系统还包括设置于液压缸11的无杆腔和液压泵2之间的第一单向阀22。
第一单向阀22的进口与换向阀8的第一工作口和第二溢流阀9的进口分别连通，第一单向阀22的出口与液压缸11的无杆腔和第二电控阀7的第一工作口连通。
在一些实施例中，检测装置13可以包括角度传感器，并通过角度传感器所测量的角度换算出实际距离的大小；或者，检测装置13包括长度传感器，并通过长度传感器直接测量出实际距离的大小。
在一些实施例中，液压控制系统还包括与控制装置12信号连接的力传感器14，控制装置12可以获取力传感器14所测量的力的大小。在液压控制系统应用于拖拉机时，在耕作过程中，力传感器14可以用于获取拉力信息；在非作业状态，力传感器14可以用于获取机具重量信息。
在一些实施例中，液压控制系统还包括用于检测发动机1的转速大小的转速检测器21。控制装置12与转速检测器21信号连接，以获得发动机1的转速大小。
基于上述各个实施例中的液压控制系统，本公开还提供了一种拖拉机，包括上述的液压控制系统。
在一些实施例中，拖拉机还包括悬挂装置，悬挂装置与液压缸11的缸杆连接， 悬挂装置用于连接作业机具。根据作业种类的不同，可以选用不同的作业机具。在该实施例中，悬挂装置作为执行元件30。
在一些实施例中，拖拉机还包括作业机具，作业机具与悬挂装置连接。在该实施例中，悬挂装置和作业机具一起作为执行元件30。
在一些实施例中，控制装置12还与目标位置设置旋钮15、上升旋钮16、下降旋钮17、强压触发18、压力设定装置19和限高设置旋钮20信号连接，以获取这些旋钮的输入数据，并根据这些数据对液压控制系统进行控制。这些旋钮也可以替换为按钮或者显示屏输入。
基于上述各个实施例中的液压控制系统，本公开还提供了一种液压控制方法，包括：
在执行元件30上升过程中，控制第一电控阀6的最大输入电流为第一电流值，第一电流值为在液压泵2的输出流量达到最大值时第一电控阀6所需要的最小电流。
根据流量饱和现象，在液压泵2的流量达到最大时，且未达到第一电控阀6的最大通流能力时，即使增大第一电控阀6的输入电流，第一电控阀6的通流流量也不会再发生变化，因此将第一电流值设置为液压泵2的流量达到最大时对应的第一电控阀6的最小输入电流，可以有效节约能源，同时避免在液压泵2的流量达到饱和后由于继续增大第一电控阀6的输入电流而带来的电磁阀产热问题，也可以避免破坏液压泵2的输出流量与第一电控阀6的输入电流之间的线性关系。
在一些实施例中，液压控制方法还包括：
提供与液压泵2驱动连接的发动机1；
设定减速距离的大小，减速距离为执行元件30从开始减速到停止运动所运动的距离；
在执行元件30上升过程中，检测执行元件30与目标位置之间的实际距离；和
比较实际距离和减速距离的大小，在首次检测结果为实际距离大于减速距离时，控制第一电控阀6的输入电流保持在第二电流值，第二电流值等于或小于第一电流值；并在实际距离减小至等于减速距离时，控制第一电控阀6的输入电流开始减小。
在上述实施例中，通过设定减速距离，可以根据实际距离与减速距离的大小控制第一电控阀6的输入电流的大小，从而有效控制第一电控阀6的输出流量，进而控制液压缸11动作的速度，减少液压缸11在到达目标位置时出现急停而造成的冲击，有效提高液压缸11动作的平稳性。
在一些实施例中，液压控制方法还包括：
在首次检测结果为实际距离小于减速距离时，控制第一电控阀6的输入电流先调节至第三电流值，然后再从第三电流值开始减小，第三电流值小于第一电流值，且第三电流值的大小根据实际距离的大小和在减速距离内距离与电流的对应关系确定。
在首次检测实际距离的大小时即检测到实际距离小于减速距离的结果时，可以直接将第一电控阀6的输入电流调节至第三电流值并从第三电流值开始减小。这样设置可以在实际距离减小为零之前尽可能早地对输入电流进行控制，实现执行元件在到达目标位置时能够平稳停止运动的目的。
在一些实施例中，液压控制方法还包括：
在执行元件30开始减速时，先将第一电控阀6的输入电流从当前的第四电流值减小至第五电流值，然后再使第一电控阀6的输入电流从第五电流值开始减小，其中，在第一电控阀6的输入电流为第四电流值时液压泵2的流量与在第一电控阀6的输入电流为第五电流值时液压泵2的流量相等。
如图6所示，在一些实施例中，液压控制方法还包括：
在启动第一电控阀6后，在第一预设时间内将第一电控阀6的输入电流增大至第一电控阀6的工作电流允许范围内的最大值，然后在第二预设时间内将第一电控阀6的输入电流减小至第一电控阀6的工作电流允许范围内的最小值，然后再使第一电控阀6的输入电流按照预设函数关系逐渐增大。
这样设置的好处是，可以通过电流的快速增大和快速减小使液压缸11快速建立起压力，解决液压缸11响应速度慢的问题。
在一些实施例中，第一预设时间为8毫秒至15毫秒，第二预设时间为10毫秒至15毫秒。
在一些实施例中，液压控制方法还包括：
提供与液压缸11的有杆腔连通且开启压力大小可调的第一溢流阀10；
在执行元件30在重力和液压缸11的驱动力共同作用下钻入预设物体内部时，先设定执行元件30在下降过程中所受到压力的压力值，然后根据所设定的压力值调节第一溢流阀10的开启压力的大小。
下面对应用本公开液压控制系统一个实施例的拖拉机的控制过程进行说明：
如图3所示，液压缸11为拖拉机的后悬挂油缸，该油缸的缸杆与作业机具连接。
检测装置13用于获取作业机具的实际位置信息。力传感器14在耕作过程中可以 获取拉力信息，在非作业状态可以获取机具重量信息。转速检测器21用于检测发动机1的转速，或者通过CAN协议从发动机控制装置12的CAN总线获取。限高设置旋钮20用于设定作业机具的最高位置限制信息。目标位置设置旋钮15用于设定目标位置的深度信息。压力设定装置19用于设定强压模式时的压力大小，控制装置12根据强压压力大小对应控制第一溢流阀10的溢流值。上升旋钮16、下降旋钮17及强压触发18为开关信号，均与控制装置12信号连通。控制装置12的输出端与第一电控阀6、第二电控阀7、换向阀8和第一溢流阀10的控制端相连。液压泵2为定量泵，液压泵2的输出液压油与卸荷阀3的入口相连，在卸荷阀3的作用端设置第一阻尼4，同时液压泵2与第一电控阀6的入口相连，第一电控阀6的出口压力油与卸荷阀3的弹簧端相连，并在第一电控阀6和卸荷阀3的弹簧端设置用于缓冲负载压力的第二阻尼5。第一电控阀6的出口通过换向阀8后与第二溢流阀9的入口相连，同时通过第一单向阀22通往液压缸11的无杆腔。液压缸11的无杆腔同时与第二电控阀7的入口相连，液压缸11的有杆腔与第一溢流阀10的入口相连。
液压控制系统的工作方式为：
在作业机具上升过程中的控制：
当上升旋钮16动作时，上升动作触发信号传递到控制装置12，控制装置12获取限高设置旋钮20设置的信息以确定最高上升的目标位置，同时获取发动机转速信息，并将发动机1的转速代表液压泵2的转速输入到控制装置12中，确定液压泵2的供油流量，同时控制装置12借助检测装置13获取执行元件30当前的实际位置信息，确定作业机具当前实际位置与限高位置之间的间距。同时，力传感器14的不同电压信号代表作业机具的载荷，可以判定机具的载荷大小。
整体上升过程：
液压缸11在未工作状态，液压泵2输出的液压油直接通过卸荷阀3卸荷。当液压缸11驱动作业机具开始上升动作时，控制装置12控制第一电控阀6的左位动作，液压泵2输出液压油经过第一电控阀6的左位，然后通往换向阀8的右位，并经过第一单向阀22，进入液压缸11的无杆腔，实现机具上升。
详细控制过程：
首先，控制装置12借助于力传感器14获取作业机具的载荷信息，并根据载荷信息确定控制第一电控阀6在电流上升过程的斜率，载荷越大，斜率越小。为保证平稳启动，在电流增大过程中，电流的变化率会减小，但是，机具载荷越大，驱动机具上 升所需建立的液压压力越大。为了解决响应过程慢的问题，如图6所示，在电流上升过程中，首先，控制装置12在较短时间内给定最大电流A max，使其快速响应；然后，再以较快的时间使电流下降到第一电控阀6的初开口电流A min，使其迅速具有微小开口度；然后，根据机具载荷关系进一步确定上升过程的电流增大斜率，使电流按照该斜率逐渐增大。该控制过程可以保证上升开启过程的平稳。
如图5所示，对于液压泵系统，控制装置12根据发动机转速信息，可以确定当前液压泵2的输出流量，当拖拉机中用于控制悬挂油缸的液压系统为负载敏感系统时，通流流量与阀口开度相关，也即通流流量与电流呈线性比例，则针对不同发动机转速，液压泵2的输出流量不同。通过查表可以获得与之相对应的最大限制电流A lim。控制装置12在给定电流上升过程中，不会总给定到最大电流A max，以使电磁线圈不会总在最大电流下工作，电磁线圈产热减小，可以实现对电磁阀的保护，避免出现流量饱和现象。而且，整个速度增加过程为线性过程。
对于电流下降过程，如果电流从A max开始下降，则因为流量饱和现象，在A max到A lim之间，机具实际没有减速，如果目前发动机1的转速大小能够使液压泵2的输出流量达到限制电流A lim对应的流量，则液压泵2的流量从A lim对应的流量开始下降。而且，整个电流下降过程，对应流量控制呈线性变化。
进一步地，控制装置12根据发动机转速信息设置减速距离。发动机转速越高，液压泵2的输出流量越大，给定对应转速的最大电流A lim时，则液压缸11的动作速度越快，进而需要更大的减速距离来确保停止平稳。
如图4所示，控制装置12根据检测装置13检测的液压缸11的实际位置和限高设置旋钮20所设定的目标位置的值，确定当前实际位置与限高位置之间实际的实际距离d，当实际距离d为d1，且d1大于减速距离c的大小时，则按A lim电流给定第一电控阀6，等实际距离d达到设定的减速距离c时，则开始减速；如果第一次检测时实际距离d为d2，且d2小于速区间c的大小，则直接给定减速距离内对应的限制电流，并开始减速。
再进一步地，考虑到电流从增大到减小过程，对于第一电控阀6具有滞环现象，在到达减速距离时，如果从A lim开始按一定斜率开始降低电流，则因为有滞环的存在，在初始电流降低过程，速度没有改变，仍旧以较快速度接近限高位置。本公开提供的液压控制系统采用了滞环补偿措施，即根据事先测试的第一电控阀6的变化曲线，确定滞环平均值e，在达到减速距离后，控制装置12将电流直接调节至A lim-e，然后按 某一斜率开始减速，则速度容易控制，减速距离充足，兼顾效率和稳定关系。
作业机具在下降过程中的强压控制：
当按下下降旋钮17时，控制装置12控制第二电控阀7动作，使其左位动作，液压缸11的无杆腔内的液压油直接从第二电控阀7的左位通往液压流体箱，使得作业机具下降。当控制装置12获取强压触发18的信号时，控制装置12根据压力设定装置19的设定值和如图7所示的压力与电流的对应曲线，对第一溢流阀10的开启压力进行调节。因此，当强压触发时，控制装置12控制第二电控阀7的左位动作的基础上，控制装置12同时控制第一电控阀6及换向阀8的左位动作，液压泵2输出液压油进入液压缸11的有杆腔，推动机具在液压油作用下动力式下降，并在设定的溢流压力下入土，不同地形，可以设定不同的溢流压力。当地面板结或地面较硬时，设置小电流，保证较大压力下机具入土。对于犁具，当达到目标位置设置旋钮15的设定深度后，强压模式解除，但对一些播种机具，其本身入土深度基本靠自重，为保证播种所需深度，借助于不同设定压力，可以保证耕深的一致性。
本公开提供的拖拉机实施例至少具有以下优点：
1、机具上升启动过程，电流首先以较大斜率快速增，使第一电控阀进行快速响应，然后电流下降到第一电控阀的开启点，使机具液压缸无杆腔快速建立压力，并根据不同机具载荷设定不同斜率进行速度变化，确定上升启动平稳；
2、根据不同发动机转速，确定相应流量，查表对应给定控制阀相应的电流值，设定相应的限制电流，使整个速度增加及降低过程近似线性，克服中低速下的流量饱和现象，同时限制不必要的电磁阀电流，减小电磁阀产热；
3、根据发动机转速，设定不同的减速距离，并根据距离目标位置的距离限制不同电流，保证上升过程的效率，同时使机具上升停止过程平稳；
4、减速降低过程中，实施滞环补偿，直接越过滞环值，使减速响应快，速度降低呈线性，克服因滞环引起速度不变导致不能稳定停止的问题，确保在设定减速距离停止平稳；
5、液压缸有杆腔的出口设置开启压力可调的第一溢流阀，在控制过程可以根据不同土质及地形进行强压功能触发，通过调节第一溢流阀的设定压力，可以针对不同的机具及地形实现不同的机具深度控制，克服由于机具自重不断变化而引起的深度不一的问题。
最后应当说明的是：以上实施例仅用以说明本公开的技术方案而非对其限制；尽 管参照较佳实施例对本公开进行了详细的说明，所属领域的普通技术人员应当理解：在不脱离本公开原理的前提下，依然可以对本公开的具体实施方式进行修改或者对部分技术特征进行等同替换，这些修改和等同替换均应涵盖在本公开请求保护的技术方案范围当中。

Claims (19)

  1. 一种液压控制系统，包括：
    液压泵(2)；
    液压缸(11)，与所述液压泵(2)流体连通；
    执行元件(30)，与所述液压缸(11)的缸杆连接；
    第一电控阀(6)，设置于所述液压泵(2)和所述液压缸(11)之间的连接管路上，所述第一电控阀(6)被配置为调节所述连接管路的通流量；和
    控制装置(12)，与所述第一电控阀(6)信号连接，所述控制装置(12)被配置为在所述执行元件(30)上升过程中控制所述第一电控阀(6)的最大输入电流为第一电流值，所述第一电流值为在所述液压泵(2)的输出流量达到最大值时所述第一电控阀(6)所需要的最小电流。
  2. 根据权利要求1所述的液压控制系统，还包括：
    发动机(1)，与所述液压泵(2)驱动连接；和
    检测装置(13)，被配置为在所述执行元件(30)上升过程中检测所述执行元件(30)与目标位置之间的实际距离，所述控制装置(12)还被配置为设定减速距离的大小，并在所述检测装置(13)的首次检测结果为所述实际距离大于所述减速距离时，控制所述第一电控阀(6)的输入电流保持在第二电流值；且在所述实际距离减小至等于所述减速距离时，控制所述第一电控阀(6)的输入电流开始减小，其中，所述减速距离为所述执行元件(30)从开始减速到停止运动所运动的距离，所述第二电流值等于或小于所述第一电流值。
  3. 根据权利要求2所述的液压控制系统，其中，所述控制装置(12)还被配置为在所述检测装置(13)的首次检测结果为所述实际距离小于或等于所述减速距离时，控制所述第一电控阀(6)的输入电流先调节至第三电流值，然后再从所述第三电流值开始减小，所述第三电流值小于所述第一电流值，且所述第三电流值的大小根据所述实际距离的大小和在所述减速距离内距离与电流的对应关系确定。
  4. 根据权利要求1至3任一项所述的液压控制系统，其中，所述控制装置(12) 还被配置为在所述执行元件(30)开始减速时，先将所述第一电控阀(6)的输入电流从当前的第四电流值减小至第五电流值，然后再使所述第一电控阀(6)的输入电流从所述第五电流值开始减小，其中，在所述第一电控阀(6)的输入电流为所述第四电流值时所述液压泵(2)的流量与在所述第一电控阀(6)的输入电流为所述第五电流值时所述液压泵(2)的流量相等。
  5. 根据权利要求1至4任一项所述的液压控制系统，其中，所述控制装置(12)还被配置为在启动所述第一电控阀(6)后，在第一预设时间内将所述第一电控阀(6)的输入电流增大至所述第一电控阀(6)的工作电流允许范围内的最大值，然后在第二预设时间内将所述第一电控阀(6)的输入电流减小至所述第一电控阀(6)的工作电流允许范围内的最小值，然后再使所述第一电控阀(6)的输入电流按照预设函数关系逐渐增大。
  6. 根据权利要求1至5任一项所述的液压控制系统，还包括设置于所述第一电控阀(6)和所述液压缸(11)之间的换向阀(8)，所述换向阀(8)的进口与所述第一电控阀(6)连通，所述换向阀(8)的两个工作口分别与所述液压缸(11)的有杆腔和无杆腔连通。
  7. 根据权利要求1至6任一项所述的液压控制系统，还包括与所述液压缸(11)的有杆腔连通的第一溢流阀(10)，且所述第一溢流阀(10)的开启压力大小可调。
  8. 根据权利要求7所述的液压控制系统，还包括压力设定装置(19)，所述压力设定装置(19)用于设定所述执行元件(30)在下降过程中所受到压力的压力值，所述控制装置(12)与所述压力设定装置(19)信号连接，所述控制装置(12)被配置为根据所述压力设定装置(19)所设定的压力值调节所述第一溢流阀(10)的开启压力。
  9. 根据权利要求1至8任一项所述的液压控制系统，还包括与所述液压泵(2)的出口和所述第一电控阀(6)之间的连接流路连通的卸荷阀(3)，所述卸荷阀(3)的进口和所述卸荷阀(3)的压力端之间设有第一阻尼(4)，所述第一电控阀(6) 与所述卸荷阀(3)的弹簧端连通，且所述第一电控阀(6)与所述卸荷阀(3)的弹簧端之间设有第二阻尼(5)。
  10. 根据权利要求1至9任一项所述的液压控制系统，其中，所述第一电控阀(6)包括二位三通控制阀，所述第一电控阀(6)的第一工作口与所述液压缸(11)连通，所述第一电控阀(6)的第二工作口与所述液压泵(2)的出口连通，所述第一电控阀(6)的第三工作口与液压流体箱连通，所述第一电控阀(6)在第一工作位时，所述第二工作口关闭，所述第一工作口与所述第三工作口连通；所述第一电控阀(6)在第二工作位时，所述第三工作口关闭，所述第一工作口与所述第二工作口连通。
  11. 根据权利要求1至10任一项所述的液压控制系统，还包括第二电控阀(7)，所述第二电控阀(7)连接于所述液压缸(11)的无杆腔和液压流体箱之间。
  12. 一种拖拉机，包括如权利要求1至11任一项所述的液压控制系统。
  13. 一种基于如权利要求1至11任一项所述的液压控制系统的液压控制方法，包括：
    在执行元件(30)上升过程中，控制第一电控阀(6)的最大输入电流为第一电流值，所述第一电流值为在液压泵(2)的输出流量达到最大值时所述第一电控阀(6)所需要的最小电流。
  14. 根据权利要求13所述的液压控制方法，还包括：
    提供与所述液压泵(2)驱动连接的发动机(1)；
    设定减速距离的大小，所述减速距离为执行元件(30)从开始减速到停止运动所运动的距离；
    在所述执行元件(30)上升过程中，检测所述执行元件(30)与目标位置之间的实际距离；和
    比较所述实际距离和所述减速距离的大小，在首次检测结果为所述实际距离大于所述减速距离时，控制第一电控阀(6)的输入电流保持在第二电流值，所述第二电流值等于或小于所述第一电流值；并在所述实际距离减小至等于所述减速距离时，控 制所述第一电控阀(6)的输入电流开始减小。
  15. 根据权利要求14所述的液压控制方法，还包括：
    在首次检测结果为所述实际距离小于所述减速距离时，控制所述第一电控阀(6)的输入电流先调节至第三电流值，然后再从第三电流值开始减小，所述第三电流值小于所述第一电流值，且所述第三电流值的大小根据所述实际距离的大小和在所述减速距离内距离与电流的对应关系确定。
  16. 根据权利要求13至15任一项所述的液压控制方法，还包括：
    在所述执行元件(30)开始减速时，先将所述第一电控阀(6)的输入电流从当前的第四电流值减小至第五电流值，然后再使所述第一电控阀(6)的输入电流从所述第五电流值开始减小，其中，在所述第一电控阀(6)的输入电流为所述第四电流值时所述液压泵(2)的流量与在所述第一电控阀(6)的输入电流为所述第五电流值时所述液压泵(2)的流量相等。
  17. 根据权利要求13至16任一项所述的液压控制方法，还包括：
    在启动所述第一电控阀(6)后，在第一预设时间内将所述第一电控阀(6)的输入电流增大至所述第一电控阀(6)的工作电流允许范围内的最大值，然后在第二预设时间内将所述第一电控阀(6)的输入电流减小至所述第一电控阀(6)的工作电流允许范围内的最小值，然后再使所述第一电控阀(6)的输入电流按照预设函数关系逐渐增大。
  18. 根据权利要求17所述的液压控制方法，其中，所述第一预设时间为8毫秒至15毫秒，所述第二预设时间为10毫秒至15毫秒。
  19. 根据权利要求13至18任一项所述的液压控制方法，还包括：
    提供与所述液压缸(11)的有杆腔连通且开启压力大小可调的第一溢流阀(10)；
    在所述执行元件(30)在重力和所述液压缸(11)的驱动力共同作用下钻入预设物体内部时，先设定所述执行元件(30)在下降过程中所受到压力的压力值，然后根据所设定的压力值调节所述第一溢流阀(10)的开启压力的大小。
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