CN114294273B - Hydraulic control system, tractor and hydraulic control method - Google Patents

Hydraulic control system, tractor and hydraulic control method Download PDF

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Publication number
CN114294273B
CN114294273B CN202111675837.2A CN202111675837A CN114294273B CN 114294273 B CN114294273 B CN 114294273B CN 202111675837 A CN202111675837 A CN 202111675837A CN 114294273 B CN114294273 B CN 114294273B
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valve
current
hydraulic
electrically controlled
current value
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CN114294273A (en
Inventor
张笑
秦浩良
张露云
李思辰
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Xuzhou Xcmg Agricultural Equipment Technology Co ltd
Jiangsu XCMG Construction Machinery Institute Co Ltd
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Xuzhou Xcmg Agricultural Equipment Technology Co ltd
Jiangsu XCMG Construction Machinery Institute Co Ltd
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Priority to CN202111675837.2A priority Critical patent/CN114294273B/en
Priority to PCT/CN2022/071820 priority patent/WO2022252628A1/en
Priority to BR112022026901A priority patent/BR112022026901A2/en
Publication of CN114294273A publication Critical patent/CN114294273A/en
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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

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Fluid Mechanics (AREA)
  • General Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Zoology (AREA)
  • Soil Sciences (AREA)
  • Environmental Sciences (AREA)
  • Fluid-Pressure Circuits (AREA)

Abstract

The invention relates to a hydraulic control system, a tractor and a hydraulic control method, wherein the hydraulic control system comprises a hydraulic pump, a hydraulic cylinder, an actuating element, a first electric control valve and a control device, the hydraulic cylinder is in fluid communication with the hydraulic pump, the actuating element is connected with a cylinder rod of the hydraulic cylinder, the first electric control valve is arranged on a connecting pipeline between the hydraulic pump and the hydraulic cylinder, the first electric control valve is configured to adjust the flow rate of the connecting pipeline, the control device is in signal connection with the first electric control valve, the control device is configured to control the maximum input current of the first electric control valve to be a first current value in the ascending process of the actuating element, and the first current value is the minimum current required by the first electric control valve when the output flow rate of the hydraulic pump reaches the maximum value.

Description

Hydraulic control system, tractor and hydraulic control method
Technical Field
The invention relates to the technical field of agricultural machinery, in particular to a hydraulic control system, a tractor and a hydraulic control method.
Background
The tractor operates under different field conditions by means of different machines. For the lifting control of the machine tool, two control systems are mainly used at present, one is a mechanical lifting system, and the other is an electro-hydraulic suspension system.
For a mechanical lifting system, the transmission structure is complex, the friction loss between mechanisms is large, the rod piece transmission process and the reaction action of an elastic element are delayed, and the on-off control of a control valve has more limitations, so that the fine control of farming cannot be realized, the operation of an operator is complex, and the labor intensity is large.
Although the electro-hydraulic suspension system realizes various electric control fusion, when the suspension cylinder is provided with a tool to rise, the suspension cylinder stops suddenly due to speed and has no buffer, so that the problem of stopping impact exists, and particularly when the engine has high rotating speed and the output flow of the driving hydraulic pump is large, larger impact can be formed.
It is noted that the information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information constitutes prior art already known to a person skilled in the art.
Disclosure of Invention
The embodiment of the invention provides a hydraulic control system, a tractor and a hydraulic control method, which can effectively improve the stability of the action of a hydraulic cylinder.
According to a first aspect of the present invention, there is provided a hydraulic control system comprising:
a hydraulic pump;
a hydraulic cylinder in fluid communication with the hydraulic pump;
the actuating element is connected with a cylinder rod of the hydraulic cylinder;
the first electric control valve is arranged on a connecting pipeline between the hydraulic pump and the hydraulic cylinder and is configured to adjust the flow of the connecting pipeline; and
and the control device is in signal connection with the first electric control valve and is configured to control the maximum input current of the first electric control valve to be a first current value in the ascending process of the executing element, and 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.
In some embodiments, the hydraulic control system further comprises:
the engine is in driving connection with the hydraulic pump; and
the control device is also configured to set the size of the deceleration distance and control the input current of the first electric control valve to be kept at a second current value when the actual distance is larger than the deceleration distance as a first detection result of the detection device; and when the actual distance is reduced to be equal to a deceleration distance, controlling the input current of the first electric control valve to start to reduce, wherein the deceleration distance is the distance of the movement of the actuating element from the beginning of deceleration to the stop of movement, and the second current value is equal to or smaller than the first current value.
In some embodiments, the control device is further configured to control the input current of the first electrically controlled valve to be adjusted to a third current value and then decreased from the third current value when the first detection result of the detection device is that the actual distance is smaller than or equal to the deceleration distance, 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 the distance and the current within the deceleration distance.
In some embodiments, the control device is further configured to, when the actuator starts decelerating, first decrease the input current of the first electrically controlled valve from a current fourth current value to a fifth current value, and then decrease the input current of the first electrically controlled valve from the fifth current value, wherein the flow rate of the hydraulic pump when the input current of the first electrically controlled valve is the fourth current value is equal to the flow rate of the hydraulic pump when the input current of the first electrically controlled valve is the fifth current value.
In some embodiments, the control device is further configured to increase the input current of the first electrically controlled valve to a maximum value within an allowable range of the operating current of the first electrically controlled valve within a first preset time after the first electrically controlled valve is actuated, then decrease the input current of the first electrically controlled valve to a minimum value within an allowable range of the operating current of the first electrically controlled valve within a second preset time, and then gradually increase the input current of the first electrically controlled valve according to a preset functional relationship.
In some embodiments, the hydraulic control system further comprises a directional valve disposed between the first electrically controlled valve and the hydraulic cylinder, an inlet of the directional valve being in communication with the first electrically controlled valve, and two working ports of the directional valve being in communication with the rod chamber and the rodless chamber of the hydraulic cylinder, respectively.
In some embodiments, the hydraulic control system further comprises a first relief valve in communication with the rod chamber of the hydraulic cylinder, and the first relief valve has an adjustable cracking pressure.
In some embodiments, the hydraulic control system further comprises a pressure setting device for setting a pressure value of the pressure to which the actuator is subjected during the descent, the control device being in signal connection with the pressure setting device, the control device being configured to adjust the opening pressure of the first spill valve in accordance with the pressure value set by the pressure setting device.
In some embodiments, the hydraulic control system further includes an unloader valve in communication with a connecting flow path between the outlet of the hydraulic pump and the first electrically controlled valve, a first damper is disposed between the inlet of the unloader valve and the pressure end of the unloader valve, the first electrically controlled valve is in communication with the spring end of the unloader valve, and a second damper is disposed between the first electrically controlled valve and the spring end of the unloader valve.
In some embodiments, the first electrically controlled valve comprises a two-position, three-way control valve, the first working port of the first electrically controlled valve is in communication with the hydraulic cylinder, the second working port of the first electrically controlled valve is in communication with the outlet of the hydraulic pump, the third working port of the first electrically controlled valve is in communication with the hydraulic fluid tank, the second working port is closed when the first electrically controlled valve is in the first working position, and the first working port is in communication with the third working port; when the first electric control valve is at the second working position, the third working port is closed, and the first working port is communicated with the second working port.
In some embodiments, the hydraulic control system further comprises a second electrically-controlled valve connected between the rodless chamber of the hydraulic cylinder and the hydraulic fluid tank.
According to a second aspect of the present invention there is provided a tractor comprising a hydraulic control system as described above.
According to a third aspect of the present invention, there is provided a hydraulic control method based on the hydraulic control system described above, including:
and controlling the maximum input current of the first electric control valve to be a first current value in the ascending process of the executing element, wherein 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.
In some embodiments, the hydraulic control method further comprises:
providing an engine in driving connection with the hydraulic pump;
setting the size of a deceleration distance, wherein the deceleration distance is the distance for the actuator to move from the beginning of deceleration to the stop of movement;
detecting the actual distance between the actuator and the target position in the process of ascending the actuator; and
comparing the actual distance with the deceleration distance, and controlling the input current of the first electric control valve to be kept at a second current value when the first detection result shows that the actual distance is greater than the deceleration distance, wherein the second current value is equal to or less than the first current value; and controlling the input current of the first electrically controlled valve to start to decrease when the actual distance decreases to be equal to the deceleration distance.
In some embodiments, the hydraulic control method further comprises:
and when the first detection result is that the actual distance is smaller than the deceleration distance, controlling the input current of the first electric control valve to be adjusted to a third current value, and then reducing from the third current value, wherein the third current value is smaller than the first current value, and the size of the third current value is determined according to the size of the actual distance and the corresponding relation between the distance and the current in the deceleration distance.
In some embodiments, the hydraulic control method further comprises:
when the executive component starts to decelerate, the input current of the first electric control valve is firstly reduced from the current fourth current value to the fifth current value, then the input current of the first electric control valve is reduced from the fifth current value, wherein when the input current of the first electric control valve is the fourth current value, the flow of the hydraulic pump is equal to the flow of the hydraulic pump when the input current of the first electric control valve is the fifth current value.
In some embodiments, the hydraulic control method further comprises:
after the first electric control valve is started, the input current of the first electric control valve is increased to the maximum value within the allowable range of the working current of the first electric control valve within a first preset time, then the input current of the first electric control valve is reduced to the minimum value within the allowable range of the working current of the first electric control valve within a second preset time, and then the input current of the first electric control valve is gradually increased according to a preset functional relation.
In some embodiments, the first predetermined time is 8 to 15 milliseconds, and the second predetermined time is 10 to 15 milliseconds.
In some embodiments, the hydraulic control method further comprises:
providing a first overflow valve which is communicated with a rod cavity of the hydraulic cylinder and has adjustable opening pressure;
when the actuating element drills into the preset object under the combined action of gravity and the driving force of the hydraulic cylinder, the pressure value of the pressure applied to the actuating element in the descending process is set, and then the opening pressure of the first overflow valve is adjusted according to the set pressure value.
Based on the technical scheme, in the ascending process of the executing element, 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, and therefore the advantage that the problem of extra heat generation of the electromagnetic valve caused by continuously increasing the input current of the first electric control valve after the flow of the hydraulic pump reaches saturation can be avoided.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:
fig. 1 is a schematic diagram of hysteresis of an electrically controlled valve.
FIG. 2 is a schematic representation of the changing relationship between the input current to the electrically controlled valve and the fluid flow to the electrically controlled valve at flow saturation.
FIG. 3 is a hydraulic control schematic of some embodiments of the hydraulic control system of the present invention.
Fig. 4 is a graph showing the variation relationship between the input current and the valve core flow rate of the first electrically controlled valve in some embodiments of the hydraulic control system of the present invention.
Fig. 5 is a schematic diagram of the hydraulic control method according to some embodiments of the present invention for controlling the input current to the first electrically controlled valve as a function of the actual distance.
Fig. 6 is a schematic diagram of the input current control to the first electrically controlled valve after opening the first electrically controlled valve in some embodiments of the hydraulic control method of the present invention.
Fig. 7 is a schematic diagram of the input current control of the first spill valve in some embodiments of the hydraulic control method of the present invention.
In the figure:
1. an engine; 2. a hydraulic pump; 3. an unloading valve; 4. a first damping; 5. a second damping; 6. a first electrically controlled valve; 7. a second electrically controlled valve; 8. a diverter valve; 9. a second overflow valve; 10. a first overflow valve; 11. a hydraulic cylinder; 12. a control device; 13. a detection device; 14. a force sensor; 15. a target position setting knob; 16. a raising knob; 17. a lowering knob; 18. triggering by strong pressure; 19. a pressure setting device; 20. a height limit setting knob; 21. a rotation speed detector; 22. a first check valve; 23. a second one-way valve; 30. and an execution element.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments. It should be apparent that the described embodiments are only some of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it is to be understood that the terms "central," "lateral," "longitudinal," "front," "rear," "left," "right," "upper," "lower," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in the orientation or positional relationship indicated in the drawings for convenience in describing the invention and for simplicity in description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the scope of the invention.
In view of the problems of the mechanical lifting system and the electro-hydraulic suspension system in the related art, the inventors have conducted a great deal of research and found that a hysteresis phenomenon occurs during the current increase of the electric control valve.
As shown in fig. 1, in the case of the electronic control valve, as the current increases, the opening degree of the valve port of the electronic control valve gradually increases, and the through-flow rate of the corresponding valve element also gradually increases. However, when the current starts to decrease, the flow rate does not decrease directly, but after the current decreases to a certain value, the flow rate starts to decrease, that is, for the same flow rate, there is a difference between the currents corresponding to the increasing process and the decreasing process, and the difference is the hysteresis size of the electrically controlled valve.
In the embodiment shown in fig. 1, during the current increasing and decreasing processes, the through-flow of the electrically controlled valve changes linearly with the input current, and the slope absolute values of the flow changing with the input current are equal, so the difference between a2 and a1 is the hysteresis value. In other embodiments, the change of the through-flow with the input current may be in a non-linear relationship during the increase and decrease of the current, and the absolute value of the slope of the change of the through-flow with the input current of the electrically controlled valve may not be equal, so that the hysteresis value of the electrically controlled valve may be changed.
In addition, the inventor also noted that, for control valves, the through-flow rate of the valve element was
Figure BDA0003451934700000071
Under the condition that the opening degree A of the valve core and the pressure difference delta P between the front and the back of the valve port are not changed, the through-flow is not changed for a fixed flow coefficient alpha and a fixed mass density rho. However, when the output flow rate of the hydraulic pump is small, there is a problem of flow saturation in which the opening degree of the spool gradually increases as the current of the control valve increases, but the flow rate of the fluid to the electrically controlled valve does not change any more, and at this time, the moving speed of the actuator does not change any more.
As shown in fig. 2, as the current of the electric control valve increases, the valve port gradually increases, and the flow rate to the electric control valve also continuously increases. However, when the opening degree of the valve element continues to increase due to the fact that the current continues to increase, the flow rate of the hydraulic pump is not changed, and the through-flow requirement of the electric control valve cannot be met, and the flow rate of the electric control valve does not increase along with the increase of the current. The process of increasing the current from a1 to a2 is a flow saturation process, in which the movement speed of the actuator is not changed although the magnitude of the control current is changed.
Based on the above studies, the inventors have made improvements to the hydraulic control system.
As shown in fig. 3, in some embodiments of the hydraulic control system provided by the present invention, the hydraulic control system includes a hydraulic pump 2, a hydraulic cylinder 11, an actuator 30, a first electronic control valve 6, and a control device 12, the hydraulic cylinder 11 is in fluid communication with the hydraulic pump 2, the actuator 30 is connected to a cylinder rod of the hydraulic cylinder 11, the first electronic control valve 6 is disposed on a connection line between the hydraulic pump 2 and the hydraulic cylinder 11, the first electronic control valve 6 is configured to regulate a flow rate of the connection line, the control device 12 is in signal connection with the first electronic control valve 6, and the control device 12 is configured to control a maximum input current of the first electronic control valve 6 to be a first current value during a rise of the actuator 30, the first current value being a minimum current required by the first electronic control valve 6 when an output flow rate of the hydraulic pump 2 reaches a maximum value.
According to the flow saturation phenomenon, when the flow of the hydraulic pump 2 reaches the maximum, and when the maximum through-current capacity of the first electric control valve 6 is not reached, even if the input current of the first electric control valve 6 is increased, the through-current flow of the first electric control valve 6 can not change any more, therefore, the first current value is set to be the minimum input current of the first electric control valve 6 corresponding to the time when the flow of the hydraulic pump 2 reaches the maximum, the energy can be effectively saved, and meanwhile, the problem of additional heat generation of the electromagnetic valve caused by continuously increasing the input current of the first electric control valve 6 after the flow of the hydraulic pump 2 reaches the saturation is avoided.
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 without hysteresis after the current of the first electrically controlled valve 6 is reduced, which is beneficial to improving the smoothness of the stop of the actuator 30 when the actuator rises.
In some embodiments, the hydraulic control system further comprises an engine 1 and a detection device 13, the engine 1 is in driving connection with the hydraulic pump 2, the detection device 13 is configured to detect an actual distance between the actuator 30 and a target position during the process of lifting the actuator 30, the control device 12 is further configured to set the magnitude of the deceleration distance, and control the input current of the first electrically-controlled valve 6 to be kept at a second current value when the actual distance is greater than the deceleration distance as a first detection result of the detection device 13; and controls the input current of the first electrically controlled valve 6 to start to decrease when the actual distance decreases to be equal to a deceleration distance, which is a distance moved by the actuator 30 from the start of deceleration to the stop of movement, and the second current value is equal to or less than the first current value.
The target position is a target position to be reached by the actuator 30, and when the actuator 30 reaches the target position, the actuator 30 stops 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 test refers to the first test after activation of the detection means 13.
By setting the deceleration distance, the input current of the first electric control valve 6 can be controlled according to the actual distance and the deceleration distance, so that the output flow of the first electric control valve 6 is effectively controlled, the speed of the hydraulic cylinder 11 is further controlled, the impact caused by sudden stop when the hydraulic cylinder 11 reaches a target position is reduced, and the stability of the hydraulic cylinder 11 is effectively improved.
For example, in some embodiments, when the rod of the hydraulic cylinder 11 extends and drives the actuator 30 to perform the vertical lifting motion, the control device 12 needs to control the input current of the first electrically-controlled valve 6 to start to decrease when the actuator 30 is about to reach the height-limiting position, so as to stop extending the rod and stop the actuator 30 when the actuator 30 reaches the height-limiting position. By adopting the embodiment of the hydraulic control system provided by the invention, the deceleration distance can be set according to the rotating speed of the engine 1, when the actual distance is longer than the length of the deceleration distance, the input current of the first electronic control valve 6 can be kept at the second current value, and along with the movement of the cylinder rod, when the actual distance is gradually reduced and reduced to be equal to the length of the deceleration distance, the input current of the first electronic control valve 6 is controlled to start to be reduced until the actual distance is zero. By presetting the deceleration distance and correspondingly controlling the input current of the first electric control valve 6, the actuating element 30 can stably stop moving when reaching the target position according to a plan, and the phenomenon of sudden stop and impact on the hydraulic cylinder 11 are avoided.
In the above embodiment, the magnitude of the second current value may be determined according to actual needs. When the magnitude of the actual distance is gradually reduced and reduced to a length equal to the deceleration distance, the input current to the first electrically controlled valve 6 may be reduced from the second current value, or may be reduced from other current values. The decreasing gradient of the input current to the first electrically controlled valve 6 may be a fixed gradient or a varying gradient.
Moreover, when the second current value is equal to the first current value, that is, when the actual distance detected by the detecting device 13 for the first time is greater than the deceleration distance, the input current of the first electronic control valve 6 is kept at the minimum input current of the corresponding first electronic control valve 6 when the flow rate of the hydraulic pump 2 reaches the maximum, so that when the current starts to decrease, the first electronic control valve 6 can omit the stage that the through-flow rate does not change along with the decrease of the current, and directly enter the stage that the through-flow rate decreases along with the decrease of the current, for example, the through-flow rate and the input current are in a linear relation, thereby improving the controllability of the control process.
In some embodiments, the control device 12 may set the magnitude of the deceleration distance according to the rotation speed of the engine 1. The magnitude of the output flow of the hydraulic pump 2 is affected by the magnitude of the rotation speed of the engine 1. The output flow rate of the hydraulic pump 2 can be calculated according to the rotation speed of the engine 1, and the magnitude of the deceleration distance can be determined according to the output flow rate of the hydraulic pump 2.
In some embodiments, control device 12 may set the magnitude of the deceleration distance based on the target position. For example, when the target position is 90% of the maximum stroke of the actuator 30, the deceleration distance may be set to 30% of the required movement stroke of the actuator 30.
In some embodiments, control 12 may set the magnitude of the deceleration distance to a fixed value.
In some of the above embodiments, the hydraulic control system includes a control mode of the control device 12 for the input current when the actual distance is detected to be greater than the deceleration distance, and also includes a control mode when the actual distance is reduced to be equal to the deceleration distance after the corresponding control measure is taken, and as will be described below, if the actual distance is detected by the detection device 13 for the first time, that is, the actual distance is found to be less than the deceleration distance, the control mode of the control device 12 for the input current is also included.
In some embodiments, the control device 12 is further configured to control the input current of the first electrically controlled valve 6 to be adjusted to a third current value and then decreased from the third current value when the first detection result of the detection device 13 is that the actual distance is smaller than or equal to the deceleration distance, 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 the distance and the current within the deceleration distance.
When the detection means 13 first detects the magnitude of the actual distance, i.e. detects that the actual distance is smaller than the result of the deceleration distance, the input current of the first electrically controlled valve 6 may be directly adjusted to the third current value and decreased from the third current value. The arrangement can control the input current as early as possible before the actual distance is reduced to zero, and the purpose that the actuator can stop moving smoothly when reaching the target position is achieved.
Wherein the third current value is less than the first current value. The magnitude of the third current value may be determined according to the magnitude of the actual distance and a preset correspondence relationship between the distance between the actuator 30 and the target position in the deceleration distance range and the input current of the first electronically controlled valve 6. That is, if the first detection result is that the actual distance is less than the deceleration distance, the input current of the first electrically controlled valve 6 is directly adjusted to the preset third current value, so as to achieve the same deceleration effect as when the deceleration is started from the position where the actual distance is equal to the deceleration distance, so that the actuator 30 can smoothly stop moving.
After the deceleration distance is set, tables can be established in advance according to the input current values corresponding to different positions in the deceleration distance, and the third current value can be obtained by looking up the tables directly. Alternatively, the third current value may be obtained by calculation.
As shown in fig. 4, the deceleration distance is c, and when the actual distance is d1, d1> c may be controlled to be maintained at the second current value, and then, when the actual distance is decreased to a value equal to the deceleration distance, the decrease may be started. When the actual distance is d2, d2< c, a control manner may be adopted in which the input current of the first electrically controlled valve 6 is adjusted to a third current value and decreased from the third current value. The smaller the value of the actual distance d2, the smaller the magnitude of the third current value.
In the above embodiments, the hysteresis described above may be considered when setting the magnitudes of the second current value and the third current value, or may not be considered.
In some embodiments, the control device 12 is further configured to reduce the input current of the first electrically controlled valve 6 from a current fourth current value to a fifth current value when the actuator 30 starts to decelerate, and then reduce the input current of the first electrically controlled valve 6 from the fifth current value, wherein the flow rate of the hydraulic pump 2 when the input current of the first electrically controlled valve 6 is the fourth current value is equal to the flow rate of the hydraulic pump 2 when the input current of the first electrically controlled valve 6 is the fifth current value.
The difference between the fourth current value and the fifth current value is the hysteresis average value of the first electronic control valve 6.
As can be seen from the hysteresis shown in fig. 1, when the input current to the first electrically controlled valve 6 starts to decrease, there is a period in which the through-flow rate remains constant even if the input current decreases. In the above embodiment, by reducing the input current of the first electronic control valve 6 from the fourth current value a2 to the fifth current value a1, and then reducing the input current of the first electronic control valve 6 from the fifth current value a1, the stage of the first electronic control valve 6 in which the through-flow rate remains unchanged even if the input current is reduced can be omitted, and the stage in which the through-flow rate is reduced along with the reduction of the input current can be directly entered, for example, the through-flow rate and the input current are in a linear relationship, so that the convenience and the sensitivity of the operation can be effectively improved.
As shown in fig. 5, the first electrically controlled valve 6 has an allowable range of operating current, which is a min To A max Wherein A is lim The minimum input current of the corresponding first electrically controlled valve 6 when the flow rate of the hydraulic pump 2 reaches the maximum.
As shown in fig. 6, in some embodiments, the control device 12 is further configured to increase the input current of the first electrically-controlled valve 6 to the maximum value within the allowable operating current range of the first electrically-controlled valve 6 within a first preset time after the first electrically-controlled valve 6 is started, then decrease the input current of the first electrically-controlled valve 6 to the minimum value within the allowable operating current range of the first electrically-controlled valve 6 within a second preset time, and then gradually increase the input current of the first electrically-controlled valve 6 according to a preset functional relationship.
The advantage of setting up like this is, can make pneumatic cylinder 11 establish pressure fast through the quick increase and the quick reduction of electric current, solves pneumatic cylinder 11 and responds slow problem under the heavily loaded operating mode speed control.
In some embodiments, the hydraulic control system further comprises a directional valve 8 disposed between the first electrically controlled valve 6 and the hydraulic cylinder 11, an inlet of the directional valve 8 is in communication with the first electrically controlled valve 6, and two working ports of the directional valve 8 are in communication with the rod chamber and the rodless chamber of the hydraulic cylinder 11, respectively. The outlet of the reversing valve 8 communicates with a hydraulic fluid tank.
In some embodiments, the control device 12 is in signal connection with the control end of the directional valve 8, and the control device 12 controls the direction change of the directional valve 8.
The reversing valve 8 is a two-position four-way electromagnetic valve, and when the reversing valve is at a first working position, an inlet of the reversing valve 8 is communicated with the first working port, and an outlet of the reversing valve 8 is communicated with the second working port; and in the second working position, the inlet of the reversing valve 8 is communicated with the second working port, and the outlet of the reversing valve 8 is communicated with the first working port. The first working port of the directional valve 8 is communicated with the rodless cavity of the hydraulic cylinder 11, and the second working port of the directional valve 8 is communicated with the rod cavity of the hydraulic cylinder 11.
In some embodiments, the hydraulic control system further includes a first relief valve 10 in communication with the rod chamber of the hydraulic cylinder 11, and the opening pressure of the first relief valve 10 is adjustable in magnitude.
The opening pressure of the first overflow valve 10 is set to be adjustable, so that the opening pressure of the first overflow valve 10 can be adjusted as required, and the purpose of controlling the extension length of the actuating element 30 in the descending process is achieved.
By adjusting the magnitude of the opening pressure of the first relief valve 10, the farthest moved position of the actuator 30 can be adjusted. For example, when the actuating element 30 is a seeding machine of a tractor, the seeding depth of the machine can be adjusted by adjusting the opening pressure of the first overflow valve 10, the consistency of the seeding depth is ensured, and the influence on the seeding quality due to the influence on the seeding depth caused by the weight change of seeds in the machine during the seeding process is avoided.
As shown in fig. 7, the larger the current input to the control end of the first relief valve 10 by the control device 12, the smaller the cracking pressure of the first relief valve 10.
In some embodiments, the control device 12 is in signal connection with a control end of the first relief valve 10, and the control device 12 is used for adjusting the opening pressure of the first relief valve 10.
In some embodiments, the inlet of the first excess flow valve 10 communicates with the connecting flow path between the rod chamber of the hydraulic cylinder 11 and the second working port of the directional control valve 8, and the outlet of the first excess flow valve 10 communicates with the hydraulic fluid tank.
In some embodiments, in order to achieve the adjustable opening pressure of the first relief valve 10, the first relief valve 10 may be configured as an electrical proportional relief valve, and the opening pressure of the first relief valve 10 may be adjusted by adjusting a given current magnitude.
In other embodiments, the first relief valve 10 may also be configured to be manually adjustable in opening pressure, and the opening pressure may be adjusted through manual operation.
In some embodiments, the hydraulic control system further comprises a pressure setting device 19, the pressure setting device 19 is used for setting a pressure value of the pressure applied to the actuator 30 during the descending process, the control device 12 is in signal connection with the pressure setting device 19, and the control device 12 is configured to adjust the opening pressure of the first relief valve 10 according to the pressure value set by the pressure setting device 19.
By providing the pressure setting device 19, a user can set the pressure according to the geological formation of the ground into which the actuating element 30 is to be drilled, for example, when drilling into a hard land (for example, a ground with more rocks), a larger pressure value can be set, so that the actuating element 30 can drill under enough pressure to avoid the failure of drilling or the failure of drilling depth due to too small pressure; when the drill bit drills into the ground with soft geology, a smaller pressure value can be set, the actuator 30 can be guaranteed to be capable of drilling to the preset depth, and energy waste is avoided.
Furthermore, by providing the pressure setting device 19, the magnitude of the pressure can be set according to the preset penetration depth of the actuator 30, and the penetration depth of the actuator 30 can be made to reach the preset value by adjusting the opening pressure of the first relief valve 10, thereby ensuring the consistency of the penetration depth of the actuator 30.
In some embodiments, the hydraulic control system further comprises an unloading valve 3 in communication with a connecting flow path between the outlet of the hydraulic pump 2 and the first electrically controlled valve 6. By arranging the unloading valve 3, constant pressure unloading can be realized.
In some embodiments, the inlet of the unloader valve 3 communicates with a connecting flow path between the outlet of the hydraulic pump 2 and the first electrically controlled valve 6, and the outlet of the unloader valve 3 communicates with a hydraulic fluid tank.
In some embodiments, a first damper 4 is provided between the inlet of the unloader valve 3 and the pressure end of the unloader valve 3. By arranging the first damper 4, stable unloading can be realized, and the micro-opening action is stable.
In some embodiments, the first electrically controlled valve 6 communicates with the spring end of the unloader valve 3. By communicating the first electrically controlled valve 6 with the spring end of the unloader valve 3, the load pressure can be fed back to the unloader valve 3.
In some embodiments, a second damper 5 is provided between the first electrically controlled valve 6 and the spring end of the unloader valve 3. Through the arrangement of the second damper 5, a connecting flow path between the first electronic control valve 6 and the spring end of the unloading valve 3 can be limited, and a pressure stabilizing effect is achieved.
In some embodiments, the first electronic control valve 6 comprises a two-position three-way control valve, the first working port of the first electronic control valve 6 is communicated with the hydraulic cylinder 11, the second working port of the first electronic control valve 6 is communicated with the outlet of the hydraulic pump 2, the third working port of the first electronic control valve 6 is communicated with the hydraulic fluid tank, when the first electronic control valve 6 is in the first working position, the second working port is closed, and the first working port is communicated with the third working port; when the first electric control valve 6 is at the second working position, the third working port is closed, and the first working port is communicated with the second working port.
In some embodiments, the first working port of the first electrically controlled valve 6 communicates with the first working port of the directional valve 8, and the first working port of the directional valve 8 communicates with the rodless chamber of the hydraulic cylinder 11.
In some embodiments, the control device 12 is in signal communication with the control end of the first electrically controlled valve 6, the control device 12 controlling the reversal between the different operating positions of the first electrically controlled valve 6.
In some embodiments, the first electrically controlled valve 6 is an electro-proportional control valve.
In some embodiments the hydraulic control system further comprises a second electrically controlled valve 7, the second electrically controlled valve 7 being connected between the rodless chamber of the hydraulic cylinder 11 and the hydraulic fluid tank. By providing the second electrically controlled valve 7, the retraction of the rod of the hydraulic cylinder 11 can be controlled.
In some embodiments, the control device 12 is in signal communication with the control end of the second electrically controlled valve 7, the control device 12 controlling the commutation between the different operating positions of the second electrically controlled valve 7.
In some embodiments, the second electrically controlled valve 7 comprises a two-position, two-way solenoid valve, the first working port of the second electrically controlled valve 7 being in communication with the rodless chamber of the hydraulic cylinder 11, the second working port of the second electrically controlled valve 7 being in communication with a hydraulic fluid tank, the second working port of the second electrically controlled valve 7 being in communication with the third working port of the first electrically controlled valve 6, the second working port of the second electrically controlled valve 7 being in communication with the outlet of the unloader valve 3.
In some embodiments, when the second electronic control valve 7 is in the first working position, a second check valve 23 is arranged between the first working port and the second working port, an inlet of the second check valve 23 is communicated with the hydraulic fluid tank, and an outlet of the second check valve 23 is communicated with the rodless cavity of the hydraulic cylinder 11; when the second electric control valve 7 is at the second working position, the first working port is communicated with the second working port.
In some embodiments, the second electrically controlled valve 7 is an electrically proportional control valve.
In some embodiments, the hydraulic control system further comprises a second excess flow valve 9, the second excess flow valve 9 being connected between the reversing valve 8 and the hydraulic fluid tank.
In some embodiments, the inlet of the second excess flow valve 9 communicates with the first working port of the reversing valve 8, and the outlet of the second excess flow valve 9 communicates with the third working port of the first electrically controlled valve 6 and the connection flow path of the hydraulic fluid tank.
In some embodiments, the hydraulic control system further comprises a first check valve 22 arranged between the rodless chamber of the hydraulic cylinder 11 and the hydraulic pump 2.
The inlet of the first check valve 22 is communicated with the first working port of the reversing valve 8 and the inlet of the second overflow valve 9 respectively, and the outlet of the first check valve 22 is communicated with the rodless cavity of the hydraulic cylinder 11 and the first working port of the second electric control valve 7.
In some embodiments, the detecting device 13 may include an angle sensor, and the magnitude of the actual distance is converted from the angle measured by the angle sensor; alternatively, the detection device 13 includes a length sensor, and the size of the actual distance is directly measured by the length sensor.
In some embodiments, the hydraulic control system further includes a force sensor 14 in signal communication with the control device 12, and the control device 12 may obtain the magnitude of the force measured by the force sensor 14. When the hydraulic control system is applied to a tractor, the force sensor 14 may be used to obtain tension information during the tilling process; in the non-operating state, force sensor 14 may be used to obtain implement weight information.
In some embodiments, the hydraulic control system further comprises a rotational speed detector 21 for detecting the magnitude of the rotational speed of the engine 1. The control device 12 is in signal connection with a rotation speed detector 21 to obtain the magnitude of the rotation speed of the engine 1.
Based on the hydraulic control system in each embodiment, the invention further provides a tractor comprising the hydraulic control system.
In some embodiments, the tractor further comprises a suspension device connected to the cylinder rod of the hydraulic cylinder 11, the suspension device being for connection to a work implement. According to different operation types, different operation machines can be selected. In this embodiment, a suspension device is used as the actuator 30.
In some embodiments, the tractor further includes a work implement coupled to the hitch. In this embodiment, the suspension device and the work implement together serve as an implement 30.
In some embodiments, the control device 12 is further in signal communication with a target position setting knob 15, a raise knob 16, a lower knob 17, a high pressure trigger 18, a pressure setting device 19, and a limit setting knob 20 to obtain input data for these knobs and control the hydraulic control system based on these data. These knobs may also be replaced with buttons or display screen inputs.
Based on the hydraulic control system in each of the above embodiments, the present invention further provides a hydraulic control method, including:
during the raising of the actuator 30, the maximum input current of the first electronic control valve 6 is controlled to be a first current value, which is the minimum current required by the first electronic control valve 6 when the output flow rate of the hydraulic pump 2 reaches the maximum value.
According to the flow saturation phenomenon, when the flow of the hydraulic pump 2 reaches the maximum, and when the maximum through-current capacity of the first electric control valve 6 is not reached, even if the input current of the first electric control valve 6 is increased, the through-current flow of the first electric control valve 6 can not change any more, therefore, the first current value is set to be the minimum input current of the first electric control valve 6 corresponding to the time when the flow of the hydraulic pump 2 reaches the maximum, energy can be effectively saved, meanwhile, the problem of heat generation of an electromagnetic valve caused by the fact that the input current of the first electric control valve 6 is continuously increased after the flow of the hydraulic pump 2 reaches the saturation is avoided, and the linear relation between the output flow of the hydraulic pump 2 and the input current of the first electric control valve 6 can also be avoided being damaged.
In some embodiments, the hydraulic control method further comprises:
providing an engine 1 in driving connection with a hydraulic pump 2;
setting the size of a deceleration distance, wherein the deceleration distance is the distance moved by the actuator 30 from the beginning of deceleration to the stop of movement;
detecting the actual distance between the actuator 30 and the target position during the process of ascending the actuator 30; and
comparing the actual distance with the deceleration distance, and controlling the input current of the first electric control valve 6 to be kept at a second current value when the first detection result shows that the actual distance is greater than the deceleration distance, wherein the second current value is equal to or less than the first current value; and controls the input current to the first electrically controlled valve 6 to start decreasing when the actual distance decreases to be equal to the deceleration distance.
In the above embodiment, by setting the deceleration distance, the magnitude of the input current of the first electronic control valve 6 can be controlled according to the magnitude of the actual distance and the deceleration distance, so as to effectively control the output flow of the first electronic control valve 6, further control the speed of the hydraulic cylinder 11, reduce the impact caused by sudden stop when the hydraulic cylinder 11 reaches the target position, and effectively improve the stability of the hydraulic cylinder 11.
In some embodiments, the hydraulic control method further comprises:
and when the first detection result is that the actual distance is smaller than the deceleration distance, controlling the input current of the first electric control valve 6 to be adjusted to a third current value, and then reducing from the third current value, wherein the third current value is smaller than the first current value, and the size of the third current value is determined according to the size of the actual distance and the corresponding relation between the distance and the current in the deceleration distance.
When the magnitude of the actual distance is detected for the first time, i.e. when it is detected that the actual distance is smaller than the deceleration distance, the input current to the first electrically controlled valve 6 may be directly adjusted to the third current value and decreased from the third current value. The arrangement can control the input current as early as possible before the actual distance is reduced to zero, and the purpose that the actuator can stop moving smoothly when reaching the target position is achieved.
In some embodiments, the hydraulic control method further comprises:
when the actuator 30 starts to decelerate, the input current of the first electrically controlled valve 6 is first reduced from the current fourth current value to the fifth current value, and then the input current of the first electrically controlled valve 6 is reduced from the fifth current value, wherein the flow rate of the hydraulic pump 2 when the input current of the first electrically controlled valve 6 is the fourth current value is equal to the flow rate of the hydraulic pump 2 when the input current of the first electrically controlled valve 6 is the fifth current value.
As shown in fig. 6, in some embodiments, the hydraulic control method further comprises:
after the first electronic control valve 6 is started, the input current of the first electronic control valve 6 is increased to the maximum value within the allowable range of the working current of the first electronic control valve 6 within a first preset time, then the input current of the first electronic control valve 6 is reduced to the minimum value within the allowable range of the working current of the first electronic control valve 6 within a second preset time, and then the input current of the first electronic control valve 6 is gradually increased according to a preset functional relationship.
The advantage of setting up like this is, can make pneumatic cylinder 11 set up pressure fast through the quick increase and the quick reduction of electric current, solves the slow problem of pneumatic cylinder 11 response speed.
In some embodiments, the first predetermined time is 8 to 15 milliseconds, and the second predetermined time is 10 to 15 milliseconds.
In some embodiments, the hydraulic control method further comprises:
providing a first overflow valve 10 which is communicated with a rod cavity of a hydraulic cylinder 11 and has adjustable opening pressure;
when the actuator 30 is driven by the combined action of gravity and the driving force of the hydraulic cylinder 11 to be inserted into the predetermined object, a pressure value of the pressure applied to the actuator 30 during the lowering process is set, and then the opening pressure of the first relief valve 10 is adjusted according to the set pressure value.
The following describes a control process of a tractor to which an embodiment of the hydraulic control system of the present invention is applied:
as shown in fig. 3, the hydraulic cylinder 11 is a rear suspension cylinder of a tractor, and a cylinder rod of the cylinder is connected to a work implement.
The detection device 13 is used to acquire actual position information of the work implement. The force sensor 14 can acquire tension information during tillage and implement weight information during non-operating conditions. The rotation speed detector 21 is used to detect the rotation speed of the engine 1 or is acquired from a CAN bus of the engine control device 12 through a CAN protocol. The height limit setting knob 20 is used to set the highest position limit information of the work implement. The target position setting knob 15 is used to set depth information of the target position. The pressure setting device 19 is used for setting the pressure in the high pressure mode, and the control device 12 correspondingly controls the overflow value of the first overflow valve 10 according to the high pressure. The ascending knob 16, the descending knob 17 and the strong pressure trigger 18 are switch signals and are all 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 overflow valve 10. The hydraulic pump 2 is a fixed displacement pump, the output hydraulic oil of the hydraulic pump 2 is connected with the inlet of the unloading valve 3, the action end of the unloading valve 3 is provided with a first damper 4, meanwhile, the hydraulic pump 2 is connected with the inlet of the first electric control valve 6, the outlet pressure oil of the first electric control valve 6 is connected with the spring end of the unloading valve 3, and the spring ends of the first electric control valve 6 and the unloading valve 3 are provided with a second damper 5 for buffering the load pressure. The outlet of the first electric control valve 6 is connected with the inlet of the second overflow valve 9 after passing through the reversing valve 8, and is communicated with the rodless cavity of the hydraulic cylinder 11 through the first check valve 22. The rodless cavity of the hydraulic cylinder 11 is simultaneously connected with the inlet of the second electric control valve 7, and the rod cavity of the hydraulic cylinder 11 is connected with the inlet of the first overflow valve 10.
The working mode of the hydraulic control system is as follows:
control during raising of the work implement:
when the lifting knob 16 is actuated, a lifting actuation trigger signal is transmitted to the control device 12, the control device 12 acquires information set by the limit-height setting knob 20 to determine a target position of the highest lifting, and at the same time acquires information on the engine speed, and inputs the engine speed 1 representing the rotational speed of the hydraulic pump 2 into the control device 12 to determine the oil supply flow rate of the hydraulic pump 2, and at the same time, the control device 12 acquires information on the current actual position of the actuator 30 by means of the detection device 13 to determine the distance between the current actual position of the working implement and the limit-height position. Meanwhile, the different voltage signals of the force sensor 14 represent the load of the working machine, and the load of the machine can be judged.
The integral ascending process:
when the hydraulic cylinder 11 is in a non-working state, hydraulic oil output by the hydraulic pump 2 is directly unloaded through the unloading valve 3. When the hydraulic cylinder 11 drives the working implement to start to ascend, the control device 12 controls the left position of the first electric control valve 6 to move, hydraulic oil output by the hydraulic pump 2 passes through the left position of the first electric control valve 6, then leads to the right position of the reversing valve 8, passes through the first check valve 22, and enters the rodless cavity of the hydraulic cylinder 11, and the implement ascends.
The detailed control process comprises the following steps:
first, the control device 12 acquires load information of the work implement by means of the force sensor 14 and determines, on the basis of the load information, a slope for controlling the first electrically controlled valve 6 during the current rise, the slope being smaller the greater the load. To ensure smooth start-up, the rate of change of current is reduced during the current increase, however, the greater the implement load, the greater the hydraulic pressure that needs to be built up to drive the implement up. To solve the problem of slow response, as shown in fig. 6, during the current rise, first, the control device 12 gives the maximum current a for a short time max To make it respond quickly; then, the current is reduced to the initial opening current A of the first electric control valve 6 in a relatively quick time min So that the micro-aperture is rapidly formed; then, the current increasing slope of the ascending process is further determined according to the machine load relation, and the current is gradually increased according to the slope. The control process can ensure the stability of the rising starting process.
As shown in fig. 5, for the hydraulic pump system, the control device 12 can determine the current output flow rate of the hydraulic pump 2 according to the engine speed information, and when the hydraulic system for controlling the suspension cylinder in the tractor is a load-sensitive system, the through-flow rate is related to the opening degree of the valve port, that is, the through-flow rate is linearly proportional to the current, and the output flow rate of the hydraulic pump 2 is different for different engine speeds. The maximum limiting current A corresponding to the maximum limiting current can be obtained by looking up a table lim . The control device 12 does not always give the maximum current a during the rise of the given current max Therefore, the electromagnetic coil can not always work under the maximum current, the heat production of the electromagnetic coil is reduced, the electromagnetic valve can be protected, and the flow saturation phenomenon is avoided. Moreover, the entire speed increase process is a linear process.
For the current dropping process, if the current is from A max Begins to decrease due to flow saturation at A max To A lim Meanwhile, the machine is not actually decelerated, if the current rotating speed of the engine 1 can enable the output flow of the hydraulic pump 2 to reach the limiting current A lim The corresponding flow rate is the flow rate of the hydraulic pump 2 from A lim The corresponding flow rate begins to drop. Moreover, the corresponding flow control is changed linearly in the whole current reduction process.
Further, the control device 12 sets the deceleration distance based on the engine speed information. The higher the engine speed is, the larger the output flow of the hydraulic pump 2 is, and the maximum current A corresponding to the engine speed is given lim In this case, the faster the operating speed of the hydraulic cylinder 11 is, the larger the deceleration distance is required to ensure smooth stopping.
As shown in FIG. 4, the control device 12 determines the actual distance d between the current actual position and the height-limiting 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-limiting setting knob 20, and when the actual distance d is d1 and d1 is greater than the deceleration distance c, the control device presses A lim The current is given to the first electric control valve 6, and when the actual distance d reaches the set deceleration distance c, the deceleration is started; and if the actual distance d is d2 during the first detection and d2 is smaller than the speed interval c, directly giving the corresponding limiting current in the deceleration distance and starting deceleration.
Still further, considering the current increase to decrease, there is a hysteresis for the first electrically controlled valve 6, if from a, when the deceleration distance is reached lim When the current starts to decrease at a certain slope, the speed is not changed in the initial current decreasing process because of the existence of the hysteresis loop, and the current still approaches the height limit position at a faster speed. The hydraulic control system provided by the invention adopts a hysteresis compensation measure, namely, a hysteresis average value e is determined according to a variation curve of a first electric control valve 6 tested in advance, and after a deceleration distance is reached, a control device 12 directly adjusts the current to A lim E, then starting to decelerate at a certain slope, the speed is easy to control, the deceleration distance is sufficient, and the efficiency and stability relation are considered.
Strong pressure control of the working tool in the descending process:
when the descending knob 17 is pressed down, the control device 12 controls the second electronic control valve 7 to act, so that the left position of the second electronic control valve 7 acts, hydraulic oil in the rodless cavity of the hydraulic cylinder 11 directly flows to the hydraulic fluid tank from the left position of the second electronic control valve 7, and the working machine descends. When the control device 12 acquires the signal of the strong pressure trigger 18, the control device 12 adjusts the opening 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. 7. Therefore, when strong pressure is triggered, on the basis that the control device 12 controls the left position action of the second electronic control valve 7, the control device 12 simultaneously controls the left position actions of the first electronic control valve 6 and the reversing valve 8, hydraulic oil output by the hydraulic pump 2 enters a rod cavity of the hydraulic cylinder 11, the pushing machine is driven to descend dynamically under the action of the hydraulic oil, and the pushing machine enters the soil under the set overflow pressure, and different overflow pressures can be set in different terrains. When the ground is hardened or the ground is hard, a small current is set to ensure that the machine can enter the soil under a larger pressure. For the plough tool, after the set depth of the knob 15 is set at the target position, the strong pressure mode is released, but for some seeding machines, the self-buried depth of the seeding machine basically depends on the dead weight, and the consistency of the plough depth can be ensured by means of different set pressures in order to ensure the required depth of seeding.
The tractor provided by the embodiment of the invention at least has the following advantages:
1. in the process of starting the machine tool in a rising way, the current is firstly increased rapidly with a larger slope, so that the first electric control valve can carry out rapid response, and then the current is reduced to the opening point of the first electric control valve, so that the pressure of a rodless cavity of a hydraulic cylinder of the machine tool is rapidly built, different slopes are set according to different machine tool loads to carry out speed change, and the stability of starting in the rising way is determined;
2. determining corresponding flow according to different engine rotating speeds, looking up a table to correspond to a corresponding current value of a given control valve, and setting corresponding limiting current, so that the whole speed increasing and reducing process is approximately linear, the flow saturation phenomenon at medium and low speeds is overcome, unnecessary electromagnetic valve current is limited, and heat generation of the electromagnetic valve is reduced;
3. setting different deceleration distances according to the rotating speed of the engine, limiting different currents according to the distance from the target position, ensuring the efficiency of the ascending process, and simultaneously enabling the machine tool to stably ascend and stop;
4. in the process of reducing the speed, hysteresis compensation is implemented, and the hysteresis value is directly crossed, so that the speed reduction response is fast, the speed reduction is linear, the problem that the speed cannot be stably stopped due to constant speed caused by hysteresis is solved, and the stable stopping at the set speed reduction distance is ensured;
5. the hydraulic cylinder has the export in pole chamber to set up the first overflow valve of cracking pressure adjustable, can carry out the high pressure function according to different soil property and topography at control process and trigger, through the settlement pressure of adjusting first overflow valve, can realize different machines and tools depth control to different machines and topography, overcomes the problem that the degree of depth differs because machines dead weight constantly changes and arouse.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention and not to limit it; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art will understand that: modifications to the specific embodiments of the invention or equivalent substitutions for parts of the technical features may be made without departing from the principles of the invention, and these modifications and equivalents are intended to be included within the scope of the claims.

Claims (19)

1. A hydraulic control system, comprising:
a hydraulic pump (2);
a hydraulic cylinder (11) in fluid communication with the hydraulic pump (2);
an actuator (30) connected to a rod of the hydraulic cylinder (11);
a first electrically controlled valve (6) arranged on a connection line between the hydraulic pump (2) and the hydraulic cylinder (11), the first electrically controlled valve (6) being configured to regulate the flow of the connection line; and
a control device (12) in signal connection with the first electrically controlled valve (6), the control device (12) being configured to control the maximum input current of the first electrically controlled valve (6) during the raising of the actuator (30) to a first current value, the first current value being the minimum current required by the first electrically controlled valve (6) when the output flow of the hydraulic pump (2) reaches a maximum value.
2. The hydraulic control system of claim 1, further comprising:
the engine (1) is in driving connection with the hydraulic pump (2); and
the control device (12) is further configured to set the size of a deceleration distance, and control the input current of the first electrically-controlled valve (6) to be kept at a second current value when the actual distance is larger than the deceleration distance as a first detection result of the detection device (13); and when the actual distance is reduced to be equal to the deceleration distance, controlling the input current of the first electric control valve (6) to start to reduce, wherein the deceleration distance is the distance of the actuator (30) moving from the beginning of deceleration to the stop of movement, and the second current value is equal to or less than the first current value.
3. The hydraulic control system according to claim 2, characterized in that the control device (12) is further configured to control the input current of the first electrically controlled valve (6) to be adjusted to a third current value and then to be decreased from the third current value when the actual distance is less than or equal to the deceleration distance as a result of the first detection by the detection device (13), wherein the third current value is less 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 the actual distance and the current within the deceleration distance.
4. The hydraulic control system according to claim 1, wherein the control device (12) is further configured to reduce the input current of the first electrically controlled valve (6) from a present fourth current value to a fifth current value and then reduce the input current of the first electrically controlled valve (6) from the fifth current value when the actuator (30) starts decelerating, wherein the flow rate of the hydraulic pump (2) when the input current of the first electrically controlled valve (6) is the fourth current value is equal to the flow rate of the hydraulic pump (2) when the input current of the first electrically controlled valve (6) is the fifth current value.
5. The hydraulic control system according to claim 1, characterized in that the control device (12) is further configured to increase the input current of the first electrically controlled valve (6) to a maximum value within the allowable range of operating current of the first electrically controlled valve (6) within a first preset time after activating the first electrically controlled valve (6), then to decrease the input current of the first electrically controlled valve (6) to a minimum value within the allowable range of operating current of the first electrically controlled valve (6) within a second preset time, and then to gradually increase the input current of the first electrically controlled valve (6) according to a preset functional relationship.
6. The hydraulic control system according to claim 1, further comprising a directional control valve (8) disposed between the first electrically controlled valve (6) and the hydraulic cylinder (11), wherein an inlet of the directional control valve (8) communicates with the first electrically controlled valve (6), and wherein two working ports of the directional control valve (8) communicate with the rod chamber and the rodless chamber of the hydraulic cylinder (11), respectively.
7. The hydraulic control system according to claim 1, characterized by further comprising a first relief valve (10) that communicates with the rod chamber of the hydraulic cylinder (11), and the magnitude of the opening pressure of the first relief valve (10) is adjustable.
8. The hydraulic control system according to claim 7, characterized by further comprising a pressure setting device (19), the pressure setting device (19) being adapted to set a pressure value at which the actuator (30) is subjected to pressure during lowering, the control device (12) being in signal connection with the pressure setting device (19), the control device (12) being configured to adjust the opening pressure of the first spill valve (10) in accordance with the pressure value set by the pressure setting device (19).
9. The hydraulic control system according to claim 1, further comprising an unloading valve (3) communicating with a connection flow path between an outlet of the hydraulic pump (2) and the first electronic control valve (6), a first damper (4) being provided between an inlet of the unloading valve (3) and a pressure end of the unloading valve (3), the first electronic control valve (6) communicating with a spring end of the unloading valve (3), and a second damper (5) being provided between the first electronic control valve (6) and the spring end of the unloading valve (3).
10. The hydraulic control system according to claim 1, wherein the first electrically controlled valve (6) comprises a two-position three-way control valve, a first working port of the first electrically controlled valve (6) is in communication with the hydraulic cylinder (11), a second working port of the first electrically controlled valve (6) is in communication with an outlet of the hydraulic pump (2), a third working port of the first electrically controlled valve (6) is in communication with a hydraulic fluid tank, the second working port is closed when the first electrically controlled valve (6) is in the first working position, and the first working port is in communication with the third working port; when the first electric control valve (6) is at a second working position, the third working port is closed, and the first working port is communicated with the second working port.
11. A hydraulic control system according to claim 1, further comprising a second electrically controlled valve (7), the second electrically controlled valve (7) being connected between the rodless chamber of the hydraulic cylinder (11) and the hydraulic fluid tank.
12. A tractor comprising a hydraulic control system as claimed in any one of claims 1 to 11.
13. A hydraulic control method based on the hydraulic control system according to any one of claims 1 to 11, characterized by comprising:
and controlling the maximum input current of the first electronic control valve (6) to be a first current value during the ascending process of the actuating element (30), wherein the first current value is the minimum current required by the first electronic control valve (6) when the output flow of the hydraulic pump (2) reaches the maximum value.
14. The hydraulic control method according to claim 13, characterized by further comprising:
providing an engine (1) in driving connection with the hydraulic pump (2);
setting the size of a deceleration distance, wherein the deceleration distance is the distance moved by the actuator (30) from the beginning of deceleration to the stop of movement;
detecting an actual distance between the actuator (30) and a target position during the raising of the actuator (30); and
comparing the actual distance with the deceleration distance, and controlling the input current of the first electronic control valve (6) to be kept at a second current value when the first detection result is that the actual distance is greater than the deceleration distance, wherein the second current value is equal to or less than the first current value; and controlling the input current of the first electrically controlled valve (6) to start decreasing when the actual distance decreases to equal the deceleration distance.
15. The hydraulic control method according to claim 14, characterized by further comprising:
and when the first detection result shows that the actual distance is smaller than the deceleration distance, controlling the input current of the first electric control valve (6) to be adjusted to a third current value, and then reducing the input current from the third current value, wherein 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 relation between the distance and the current in the deceleration distance.
16. The hydraulic control method according to claim 13, characterized by further comprising:
when the actuator (30) starts to decelerate, firstly reducing the input current of the first electronic control valve (6) from the current fourth current value to a fifth current value, and then reducing the input current of the first electronic control valve (6) from the fifth current value, wherein when the input current of the first electronic control valve (6) is the fourth current value, the flow rate of the hydraulic pump (2) is equal to the flow rate of the hydraulic pump (2) when the input current of the first electronic control valve (6) is the fifth current value.
17. The hydraulic control method according to claim 13, characterized by further comprising:
after the first electronic control valve (6) is started, the input current of the first electronic control valve (6) is increased to the maximum value within the allowable range of the working current of the first electronic control valve (6) within a first preset time, then the input current of the first electronic control valve (6) is reduced to the minimum value within the allowable range of the working current of the first electronic control valve (6) within a second preset time, and then the input current of the first electronic control valve (6) is gradually increased according to a preset functional relation.
18. The hydraulic control method according to claim 17, characterized in that the first preset time is 8 to 15 milliseconds, and the second preset time is 10 to 15 milliseconds.
19. The hydraulic control method according to claim 13, characterized by further comprising:
providing a first overflow valve (10) which is communicated with a rod cavity of the hydraulic cylinder (11) and has adjustable opening pressure;
when the actuating element (30) drills into a preset object under the combined action of gravity and the driving force of the hydraulic cylinder (11), the pressure value of the pressure applied to the actuating element (30) in the descending process is set, and then the opening pressure of the first overflow valve (10) is adjusted according to the set pressure value.
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