A hydraulic control method for cutting table profiling in agricultural harvesting equipment

Abstract

The present invention provides a hydraulic control system for cutting table profiling in agricultural harvesting equipment, comprising a hydraulic pump, an oil tank, an oil supply oil circuit, a lifting cylinder, an oil return oil circuit and a thrust regulating oil circuit; the lifting cylinder is used to control the rise or fall of the cutting table, and a connecting oil circuit is provided between the rod chamber and the rodless chamber of the lifting cylinder; the oil supply oil circuit is used to connect the hydraulic pump and the rodless chamber of the lifting cylinder; the oil return oil circuit is used to connect the oil tank and the rod chamber of the lifting cylinder; the thrust regulating oil circuit is used to connect the lifting cylinder and the hydraulic pump or the lifting cylinder and the oil tank. The present invention can implement active profiling control of the cutting table through the mutual cooperation of the hydraulic pump, the oil tank, the oil supply oil circuit, the lifting cylinder and the oil return oil circuit, and can also implement passive profiling control of the cutting table by controlling the connecting oil circuit to form a differential connection between the rod chamber and the rodless chamber of the lifting cylinder, thereby improving the operational flexibility of the system.

Description

Technical Field

[0001] The invention relates to the technical field of agricultural machinery, and in particular to a hydraulic control method for cutting table profiling in agricultural harvesting equipment. Background Art

[0002] With the development of modern agriculture, the pace of agricultural mechanization is getting faster and faster, and there are more and more various crop harvesting machines. In the existing agricultural harvesting machinery, the header is set into two types: turntable type and pick-up type. Among them: the turntable header is mainly used for harvesting immature crops, and the harvested straw is used as silage; the pick-up header is mainly used for harvesting mature crops. While collecting crops, the stems can be chopped up as silage.

[0003] When the turntable header is in use, the sensors around the header detect the height between the header and the ground, and feed back to the header control system to adjust the header height to achieve the purpose of profiling; when the pick-up header is in use, the height of the header is adjusted by the ups and downs of the profiling wheel under the header to achieve the purpose of profiling. At present, due to the different control methods of the two headers, different machines are required to control them, which leads to the following shortcomings: 1) The control method of the hydraulic control system for header profiling is single, and the same control system cannot adapt to the control of headers of different specifications and weights. Headers of different specifications cannot be interchanged, and the versatility is poor; 2) When the header is passively profiling, the auxiliary support cylinder cannot adjust the force on the profiling wheel according to the weight of the header. When the header weight is large, the profiling wheel is subjected to large force, and the profiling effect is poor. Summary of the invention

[0004] The object of the present invention is to provide a hydraulic control method for cutting table profiling in agricultural harvesting equipment in view of the deficiencies in the prior art.

[0005] To achieve the above-mentioned purpose, the present invention provides a hydraulic control system for cutting table profiling in agricultural harvesting equipment, comprising a hydraulic pump, an oil tank, an oil supply oil circuit, a lifting oil cylinder, an oil return oil circuit and a thrust regulating oil circuit; the lifting oil cylinder is used to control the rise or fall of the cutting table, and the lifting oil cylinder comprises a rod chamber and a rodless chamber, a connecting oil circuit is provided between the rod chamber and the rodless chamber, and a switch valve is provided on the connecting oil circuit; the oil supply oil circuit is used to connect the hydraulic pump and the rodless chamber of the lifting oil cylinder, and a first flow control mechanism and a one-way valve are provided on the oil supply oil circuit, and the oil is pumped by the hydraulic pump and delivered to the rodless chamber of the lifting oil cylinder via the first flow control mechanism and the one-way valve; the oil return oil circuit is used to connect the oil tank and the rod chamber of the lifting oil cylinder, and a second flow control mechanism is provided on the oil return oil circuit, and the oil flows back to the oil tank via the second flow control mechanism; the thrust regulating oil circuit connects the lifting oil cylinder, the hydraulic pump and the oil tank, and a pressure reducing overflow member is provided on the thrust regulating oil circuit.

[0006] Preferably, the oil supply circuit, the oil return circuit and the thrust adjustment circuit are all connected to the connecting oil circuit.

[0007] Preferably, the first flow control mechanism and the second flow control mechanism are both configured as proportional electromagnetic reversing valves with compensators.

[0008] Preferably, the first flow control mechanism and the second flow control mechanism are both configured as a combination structure of a proportional electromagnetic reversing valve and a pressure compensation valve.

[0009] Preferably, the switch valve is configured as a solenoid valve or a manual valve.

[0010] Preferably, the pressure reducing overflow component is configured as a combined structure of a pressure reducing valve and a relief valve, and is preferably an electric proportional pressure reducing relief valve.

[0011] As a further solution of the present invention, the hydraulic control system also includes a pressure sensor for detecting the hydraulic pressure in the lifting cylinder.

[0012] As a further solution of the present invention, the specific process of using the above-mentioned hydraulic control system to perform active profiling of the header is as follows:

[0013] When the height of the cutting platform from the ground is less than the preset height, the first proportional electromagnetic reversing valve and the hydraulic pump are started, and the hydraulic pump pumps the oil, and the oil enters the rodless chamber of the lifting cylinder through the first proportional electromagnetic reversing valve, the first pressure compensation valve and the one-way valve in turn, and the lifting cylinder is lifted. At the same time, the oil in the rod chamber of the lifting cylinder flows back to the oil tank through the electric proportional pressure reducing relief valve; when the sensors around the cutting platform detect that the cutting platform has risen to the preset height, the first proportional electromagnetic reversing valve loses power, and at the same time, the oil in the rodless chamber of the lifting cylinder is in a pressure-maintaining state under the action of the one-way valve, so that the cutting platform is stabilized at the preset height, thereby achieving the purpose of profiling;

[0014] When the height of the cutting platform from the ground is greater than the preset height, the second proportional solenoid reversing valve is energized, and the oil in the rodless chamber of the lifting cylinder flows back to the oil tank through the second proportional solenoid reversing valve and the second pressure compensation valve, and the lifting cylinder descends under the weight of the cutting platform. At this time, the oil required by the rod chamber of the lifting cylinder is pumped by the hydraulic pump and replenished through the electric proportional pressure reducing relief valve, and the cutting platform continues to descend; when the sensors around the cutting platform detect that the cutting platform has dropped to the preset height, the second proportional solenoid reversing valve loses power, and the oil in the rodless chamber of the lifting cylinder is in a pressure-maintaining state under the action of the one-way valve and the second proportional solenoid reversing valve, so that the cutting platform is stabilized at the preset height, thereby achieving the purpose of active profiling.

[0015] As a further solution of the present invention, the specific process of using the above-mentioned hydraulic control system to perform passive profiling of the header is as follows:

[0016] During the passive profiling process of the header, the first proportional electromagnetic reversing valve and the second proportional electromagnetic reversing valve lose power, and the electromagnetic valve is powered on and opened, so that the rod chamber and the rodless chamber of the lifting cylinder form a differential connection, and the hydraulic pump pumps oil and enters the rodless chamber of the lifting cylinder through the electric proportional pressure reducing relief valve. Under the weight of the header, the lifting cylinder does not extend and gives the header a stable supporting force, reducing the force of the header weight on the profiling wheel; at the same time, after the vehicle data processing system processes and analyzes the header height and the harvesting effect, the output current of the electric proportional pressure reducing relief valve is adjusted to change the pressure of the lifting cylinder, and then adjust the auxiliary supporting force of the lifting cylinder to the header, so that the header can achieve the best profiling effect under various terrains;

[0017] When the header is moving forward, the contoured wheels push the header up and down according to the ups and downs of the ground. When the header moves upward, the lifting cylinder is extended, and the oil pressure in the lifting cylinder is reduced. The hydraulic pump pumps the oil and replenishes it into the lifting cylinder through the electric proportional pressure reducing relief valve, so that the pressure in the lifting cylinder is stabilized at the set value.

[0018] When the header moves downward, the compression lifting cylinder descends, the oil pressure in the lifting cylinder increases, and part of the oil in the lifting cylinder overflows from the electric proportional pressure reducing relief valve back to the oil tank, so that the pressure in the lifting cylinder is stabilized at the set value, achieving the purpose of passive profiling.

[0019] Working principle of the present invention:

[0020] During active profiling, according to the height between the cutting platform and the ground detected by the sensors around the cutting platform, the first proportional electromagnetic reversing valve or the second proportional electromagnetic reversing valve is controlled to open or close, and the oil inlet or oil return of the rodless chamber of the lifting cylinder is performed, so as to adjust the lifting and lowering of the cutting platform in real time, so that the cutting platform is kept at a fixed height from the ground, so as to achieve the purpose of profiling;

[0021] During passive profiling, the electromagnetic valve is opened to form a differential connection between the rod chamber and the rodless chamber of the lifting cylinder, and the oil is pumped by the hydraulic pump and supplied to the lifting cylinder through the electric proportional pressure relief valve, so that the lifting cylinder does not extend under the weight of the header, but only provides a stable supporting force to the header. The output current of the electric proportional pressure relief valve can be adjusted according to the terrain, geology, and harvested crops, and the supporting force of the lifting cylinder to the header can be changed to reduce the force of the header weight on the profiling wheel, so as to achieve the best profiling effect during the profiling process of the header. By adding a pressure sensor to the rodless chamber of the oil cylinder, the current of the electric proportional pressure relief valve can be adjusted in real time through the pressure feedback of the pressure sensor to form a closed-loop control, and further realize the precise adjustment of the cylinder support force; avoiding the influence of proportional valve hysteresis or manufacturing differences that may occur in open-loop control.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The hydraulic control system provided by the present invention can implement active contour control of the harvesting platform through the mutual cooperation of the hydraulic pump, oil tank, oil supply circuit, lifting cylinder and oil return circuit, and can also implement passive contour control of the harvesting platform by controlling the connecting oil circuit to form a differential connection between the rod chamber and the rodless chamber of the lifting cylinder, thereby improving the operational flexibility of the system and reducing the production cost and economic burden of farmers when harvesting different crops.

[0024] (2) The present invention adopts a differential connection between the rod chamber and the rodless chamber of the lifting cylinder by using an electromagnetic valve during passive profiling, thereby making the extension and retraction speed of the lifting cylinder faster and reducing the dynamic change time of the lifting cylinder, so that the hydraulic control system is suitable for working under complex terrain conditions.

[0025] (3) The present invention provides a pressure compensation valve so that when the hydraulic control system controls the cutter to perform active profiling, the flow of oil entering the lifting cylinder is not affected by load changes under the action of the pressure compensation valve, thereby ensuring the stability of the cutter during the lifting / lowering process.

[0026] (4) In the present invention, an electric proportional pressure reducing relief valve is provided so that when the cutting platform is passively contoured, the contouring wheels push the cutting platform up and down according to the undulations of the ground, causing the pressure in the oil cylinder to increase or decrease. The electric proportional pressure reducing relief valve is used to replenish or overflow the oil in the lifting cylinder, so that the pressure in the lifting cylinder is maintained at a set value, and the auxiliary supporting force of the lifting cylinder to the cutting platform will not be affected by the change in the height of the cutting platform, thereby solving the problem that the contouring effect of the contouring wheels is poor due to the excessive weight of the cutting platform.

[0027] (5) In the present invention, a proportional electromagnetic reversing valve is provided to control the flow rate of oil entering / flowing out of the lifting cylinder, thereby controlling the speed of the lifting cylinder during lifting / lowering to ensure the stability of the header during the lifting / lowering process.

[0028] (6) In the present invention, an electric proportional pressure reducing relief valve is provided. During passive profiling, the output current can be remotely adjusted according to the profiling effect, thereby changing the lifting cylinder pressure to adapt to profiling under different complex terrain conditions, so as to achieve the best match of the force acting on the profiling wheel by the cutting platform under different terrains. The invention has the advantages of simple operation, adaptability to a wide range of working conditions, and high degree of intelligence.

[0029] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0031] Figure 1 Schematic diagram of the structural connection of the hydraulic control system in the embodiment of the present invention.

[0032] in:

[0033] 1. First proportional solenoid reversing valve, 2. First pressure compensating valve, 3. Check valve, 4. Second pressure compensating valve, 5. Second proportional solenoid reversing valve, 6. Solenoid valve, 7. Electric proportional pressure reducing relief valve, 8. Lifting cylinder, 9. Pressure sensor. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned purposes, features and advantages of the present invention more clear and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings. It should be noted that the drawings of the present invention are all simplified and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the implementation of the present invention; the "number" mentioned in the present invention is not limited to the specific number in the examples in the accompanying drawings; the directions or positional relationships indicated by "front", "middle", "back", "left", "right", "up", "down", "top", "bottom", "middle", etc. mentioned in the present invention are based on the directions or positional relationships shown in the drawings of the present invention, and do not indicate or imply that the devices or components referred to must have a specific direction, nor can they be understood as limitations on the present invention. Example

[0035] See also Figure 1As shown, the present invention provides a hydraulic control system for cutting table profiling in agricultural harvesting equipment, including a hydraulic pump, an oil tank, an oil supply circuit, a lifting cylinder 8, an oil return circuit and a thrust adjustment circuit; the lifting cylinder 8 includes a rod chamber and a rodless chamber, the rod chamber and the rodless chamber are connected by a connecting oil circuit, and the connecting oil circuit is provided with an electromagnetic valve 6 for controlling the connection or disconnection between the rod chamber and the rodless chamber; the oil supply circuit is used to connect the lifting cylinder 8 and the hydraulic pump, and the oil supply circuit is provided with a first proportional electromagnetic valve 1, a first pressure compensation valve 2 and a one-way valve 3 in sequence along the flow direction of the oil, and the oil is pumped by the hydraulic pump through The first proportional solenoid valve 1, the first pressure compensation valve 2 and the one-way valve 3 are transported to the rodless chamber of the lifting cylinder 8 to supply oil to the lifting cylinder 8; the return oil circuit is used to connect the lifting cylinder 8 and the oil tank, and the return oil circuit is provided with a second pressure compensation valve 4 and a second proportional solenoid reversing valve 5 in sequence along the oil flow direction. The oil in the rod chamber of the lifting cylinder 8 flows back to the oil tank via the second pressure compensation valve 4 and the second proportional solenoid reversing valve 5 to realize oil recovery; the thrust regulating oil circuit is used to connect the lifting cylinder 8 and the hydraulic pump or to connect the lifting cylinder 8 and the oil tank, and an electric proportional pressure reducing relief valve 7 is provided on the thrust regulating oil circuit.

[0036] Preferably, in order to monitor the hydraulic pressure in the lifting cylinder 8 in real time, the hydraulic control system further includes a pressure sensor 9 , which is connected to the lifting cylinder 8 .

[0037] Preferably, the control method for active profiling of the header using the hydraulic control system described above has the following specific working process:

[0038] When the height of the header from the ground is less than a preset height (the height of the header from the ground is detected by sensors arranged around the header, and the detected data is transmitted to the control system of the header and compared with the preset height in the control system of the header), the first proportional electromagnetic reversing valve 1 and the hydraulic pump are started, and the hydraulic pump pumps the oil, and the oil enters the rodless chamber of the lifting cylinder 8 through the first proportional electromagnetic reversing valve 1, the first pressure compensation valve 2 and the one-way valve 3 in sequence, and the lifting cylinder 8 is lifted. At the same time, the oil in the rod chamber of the lifting cylinder 8 flows back to the oil tank through the electric proportional pressure reducing relief valve 7;

[0039] When the sensors around the cutting platform detect that the cutting platform has risen to a preset height, the first proportional electromagnetic reversing valve 1 loses power, and at the same time, the oil in the rodless chamber of the lifting cylinder 8 is in a pressure-maintaining state under the action of the one-way valve 3, so that the cutting platform is stabilized at the preset height;

[0040] When the height of the header from the ground is greater than the preset height, the second proportional electromagnetic reversing valve 5 is energized, and the oil in the rodless chamber of the lifting cylinder 8 flows back to the oil tank through the second proportional electromagnetic reversing valve 5 and the second pressure compensation valve 4, and the lifting cylinder 8 descends under the weight of the header. At this time, the oil required by the rod chamber of the lifting cylinder 8 is pumped by the hydraulic pump and replenished through the electric proportional pressure reducing relief valve 7, and the header continues to descend;

[0041] When the sensors around the cutting platform detect that the cutting platform has dropped to a preset height, the second proportional electromagnetic reversing valve 5 loses power, and the oil in the rodless chamber of the lifting cylinder 8 is in a pressure-maintaining state under the action of the one-way valve 3 and the second proportional electromagnetic reversing valve 5, so that the cutting platform is stabilized at the preset height;

[0042] During the harvesting process, the header will adjust its position up and down according to the height from the ground detected by the sensor, so that the header remains at a fixed height from the ground to achieve the purpose of contour tracking.

[0043] Preferably, the control method for passive profiling of the header using the hydraulic control system described above has the following specific working process:

[0044] During the passive profiling process of the cutting platform, the first proportional electromagnetic reversing valve 1 and the second proportional electromagnetic reversing valve 5 lose power, and the electromagnetic valve 6 is powered on and opened, so that the rod chamber and the rodless chamber of the lifting cylinder 8 form a differential connection, and the hydraulic pump pumps oil and enters the rodless chamber of the lifting cylinder 8 through the electric proportional pressure reducing relief valve 7. Under the weight of the cutting platform, the lifting cylinder 8 does not extend and gives the cutting platform a stable supporting force, reducing the force of the cutting platform weight on the profiling wheel; at the same time, according to the vehicle data processing system (the sensor on the vehicle monitors the height and After processing and analyzing the height of the header and the harvesting effect, the output current of the electric proportional pressure relief valve is adjusted to change the pressure of the lifting cylinder, and then the auxiliary support force of the lifting cylinder to the header is adjusted, so that the header can achieve the best profiling effect under various terrains. The output current of the electric proportional pressure relief valve can also be manually adjusted, and the cylinder pressure can be observed through the pressure sensor 9 of the lifting cylinder to achieve manual change of the auxiliary support force;

[0045] During the harvesting process of the header, the contouring wheel pushes the header up and down according to the ups and downs of the ground. During the upward movement of the header, the lifting cylinder 8 is driven to extend, and the oil pressure in the lifting cylinder 8 is reduced. The hydraulic pump pumps the oil and replenishes it into the lifting cylinder 8 through the electric proportional pressure reducing relief valve 7, so that the pressure in the lifting cylinder 8 is stabilized at the set value.

[0046] When the cutting platform moves downward, the compression lifting cylinder 8 descends, the oil pressure in the lifting cylinder 8 increases, and part of the oil in the lifting cylinder 8 overflows from the electric proportional pressure reducing relief valve 7 and flows back to the oil tank, so that the pressure in the lifting cylinder 8 is stabilized at the set value (in this way, no matter how the cutting platform moves up and down according to the terrain, the hydraulic oil pressure in the lifting cylinder 8 remains unchanged, that is, the auxiliary supporting force of the lifting cylinder 8 to the cutting platform remains unchanged, and the auxiliary supporting force of the cylinder to the cutting platform will not be affected by the change of the cutting platform height, the force on the profiling wheel always remains unchanged, and the passive profiling effect of the cutting platform is better).

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A hydraulic control method for cutting table profiling in agricultural harvesting equipment, characterized in that: It includes a hydraulic pump, an oil tank, an oil supply circuit, a lifting cylinder, an oil return circuit and a thrust adjustment circuit; The lifting cylinder is used to control the rise or fall of the cutting platform, and the lifting cylinder includes a rod chamber and a rodless chamber, a connecting oil circuit is provided between the rod chamber and the rodless chamber, and a switch valve is provided on the connecting oil circuit; The oil supply circuit is used to connect the hydraulic pump and the rodless chamber of the lifting cylinder, and a first flow control mechanism and a one-way valve are provided on the oil supply circuit. The oil is pumped by the hydraulic pump and delivered to the rodless chamber of the lifting cylinder via the first flow control mechanism and the one-way valve. The oil return oil circuit is used to connect the oil tank and the rodless chamber of the lifting cylinder, and a second flow control mechanism is provided on the oil return oil circuit, and the oil returns to the oil tank via the second flow control mechanism; The thrust regulating oil circuit is connected to the lifting oil cylinder, the hydraulic pump and the oil tank, and a pressure reducing overflow part is provided on the thrust regulating oil circuit; During active profiling, when the height of the cutting platform from the ground is less than the preset height, the first proportional electromagnetic reversing valve and the hydraulic pump are started, and the hydraulic pump pumps the oil, which enters the rodless chamber of the lifting cylinder through the first proportional electromagnetic reversing valve, the first pressure compensation valve and the one-way valve in turn, and the lifting cylinder is lifted. At the same time, the oil in the rod chamber of the lifting cylinder flows back to the oil tank through the electric proportional pressure reducing relief valve; when the sensors around the cutting platform detect that the cutting platform has risen to the preset height, the first proportional electromagnetic reversing valve loses power, and at the same time, the oil in the rodless chamber of the lifting cylinder is in a pressure-maintaining state under the action of the one-way valve, so that the cutting platform is stabilized at the preset height, thereby achieving the purpose of profiling; when the cutting platform When the height from the ground is greater than the preset height, the second proportional electromagnetic reversing valve is energized, and the oil in the rodless chamber of the lifting cylinder flows back to the oil tank through the second proportional electromagnetic reversing valve and the second pressure compensation valve, and the lifting cylinder descends under the weight of the header. At this time, the oil required by the rod chamber of the lifting cylinder is pumped by the hydraulic pump and replenished through the electric proportional pressure reducing relief valve, and the header continues to descend; when the sensors around the header detect that the header has descended to the preset height, the second proportional electromagnetic reversing valve loses power, and the oil in the rodless chamber of the lifting cylinder is in a pressure-maintaining state under the action of the one-way valve and the second proportional electromagnetic reversing valve, so that the header is stabilized at the preset height, achieving the purpose of active profiling; During the passive profiling process of the header, the first proportional electromagnetic reversing valve and the second proportional electromagnetic reversing valve lose power, and the electromagnetic valve is powered on and opened, so that the rod chamber and the rodless chamber of the lifting cylinder form a differential connection, and the hydraulic pump pumps oil and enters the rodless chamber of the lifting cylinder through the electric proportional pressure reducing relief valve. Under the weight of the header, the lifting cylinder does not extend and gives the header a stable supporting force, reducing the force of the header weight on the profiling wheel; at the same time, after the vehicle data processing system processes and analyzes the header height and the harvesting effect, the output current of the electric proportional pressure reducing relief valve is adjusted to change the pressure of the lifting cylinder, and then adjust the auxiliary supporting force of the lifting cylinder to the header, so that the header can achieve the best profiling effect under various terrains; When the header is moving forward, the contoured wheels push the header up and down according to the ups and downs of the ground. When the header moves upward, the lifting cylinder is extended, and the oil pressure in the lifting cylinder is reduced. The hydraulic pump pumps the oil and replenishes it into the lifting cylinder through the electric proportional pressure reducing relief valve, so that the pressure in the lifting cylinder is stabilized at the set value. When the header moves downward, the compression lifting cylinder descends, the oil pressure in the lifting cylinder increases, and part of the oil in the lifting cylinder overflows from the electric proportional pressure reducing relief valve back to the oil tank, so that the pressure in the lifting cylinder is stabilized at the set value, achieving the purpose of passive profiling.

2. The hydraulic control method according to claim 1, characterized in that: The oil supply oil circuit, the oil return oil circuit and the thrust regulating oil circuit are all connected to the connecting oil circuit.

3. The hydraulic control method according to claim 1, characterized in that: The first flow control mechanism and the second flow control mechanism are both configured as proportional electromagnetic reversing valves with compensators.

4. The hydraulic control method according to claim 1, characterized in that: The first flow control mechanism and the second flow control mechanism are both configured as a combination structure of a proportional electromagnetic reversing valve and a pressure compensation valve.

5. The hydraulic control method according to claim 1, characterized in that: The switch valve is configured as a solenoid valve or a manual valve.

6. The hydraulic control method according to claim 1, characterized in that: The pressure reducing overflow component is configured as a combined structure of a pressure reducing valve and an overflow valve.

7. The hydraulic control method according to claim 1, characterized in that: The pressure reducing overflow component is configured as an electric proportional pressure reducing overflow valve.

8. The hydraulic control method according to any one of claims 1 to 7, characterized in that: Also included is a pressure sensor for detecting the hydraulic pressure in the lift cylinder.

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