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CN-121993442-A - Hydraulic system suitable for alternating positive and negative loads and control method thereof

CN121993442ACN 121993442 ACN121993442 ACN 121993442ACN-121993442-A

Abstract

The invention discloses a hydraulic system suitable for alternating positive and negative loads and a control method thereof, belonging to the technical field of hydraulic systems, wherein the system comprises an oil tank, a power source and a hydraulic cylinder, the power source is respectively connected with the hydraulic cylinder and a constant pressure reducing valve, the constant pressure reducing valve is connected with one end of a proportional throttle valve and outputs constant pressure to the proportional throttle valve, the other end of the proportional throttle valve is connected with the hydraulic cylinder, a variable throttle hole is arranged between the proportional throttle valve and the hydraulic cylinder, a pressure reducing valve is further connected on a hydraulic pipeline between the hydraulic cylinder and the variable throttle hole, the other end of the pressure reducing valve is connected with one end, far away from the fixed-value pressure reducing valve, of the proportional throttle valve, and the proportional throttle valve is further connected with the oil tank. The invention effectively solves the problem of speed runaway caused by the occurrence of large negative load under the working condition of the negative load of the hydraulic system.

Inventors

  • HE PENG
  • DU XIONG
  • ZHONG XIAOCUN

Assignees

  • 四川川润液压润滑设备有限公司

Dates

Publication Date
20260508
Application Date
20260403

Claims (10)

  1. 1. The utility model provides a hydraulic system suitable for positive and negative load is alternative, its characterized in that includes oil tank (1), power supply and pneumatic cylinder (20), the power supply respectively with pneumatic cylinder (20) and fixed value relief pressure valve (11) are connected, fixed value relief pressure valve (11) are connected with the one end of proportional throttle valve and are right the invariable pressure of proportional throttle valve output, the other end of proportional throttle valve with pneumatic cylinder (20) are connected, proportional throttle valve with be provided with variable orifice (14) between pneumatic cylinder (20), pneumatic cylinder (20) with still be connected with relief pressure valve (17) on the hydraulic line between variable orifice (14), the other end of relief pressure valve (17) with the one end that the proportional throttle valve kept away from fixed value relief pressure valve (11) is connected, proportional throttle valve still with oil tank (1).
  2. 2. A hydraulic system adapted for alternating positive and negative loads according to claim 1, characterized in that the power source is a high pressure accumulator (8) and the proportional throttle valve is a two-position two-way proportional throttle valve (12).
  3. 3. The hydraulic system suitable for alternating positive and negative loads according to claim 2, further comprising a hydraulic pump (2) and a proportional servo valve (16), wherein an oil suction port of the hydraulic pump (2) is connected with the oil tank (1), an oil outlet of the hydraulic pump (2) is connected with an inlet of a high-pressure filter (3), an outlet of the high-pressure filter (3) is connected with a first one-way valve (7), the first one-way valve (7) is respectively connected with a first normally open electromagnetic valve (9) and a first normally closed electromagnetic valve (10), the first normally closed electromagnetic valve (10) is connected with a P port of the proportional servo valve (16), an A port of the proportional servo valve (16) is connected with a third normally closed electromagnetic valve (18), the high-pressure accumulator (8) is connected with the first normally open electromagnetic valve (9), the first normally open electromagnetic valve (9) is respectively connected with a second one-way valve (15) and a constant pressure reducing valve (11), a rod cavity of the hydraulic cylinder (20) is respectively connected with a B port of the proportional servo valve (16), a proportional servo valve (16) is connected with a proportional servo valve (14), a normally open valve (14) is also connected with a proportional servo valve (14), the other end of the pressure reducing valve (17) is connected with the second normally open electromagnetic valve (19), the T port of the proportional servo valve (16) and the second normally open electromagnetic valve (19) are also respectively connected with the second normally closed electromagnetic valve (13), the oil outlet of the two-position two-way proportional throttle valve (12) is connected with the oil tank (1) through an oil return pipeline (21), the other end of the second normally closed electromagnetic valve (13) is connected with the oil return pipeline (21), and the constant pressure reducing valve (11), the two-position two-way proportional throttle valve (12) and the oil drain port of the pressure reducing valve (17) are connected with the oil tank (1).
  4. 4. A hydraulic system suitable for alternating positive and negative loads according to claim 3, characterized in that an oil return filter (4) is further arranged on an oil return pipeline (21) between the oil outlet of the two-position two-way proportional throttle valve (12) and the oil tank (1).
  5. 5. The hydraulic system suitable for alternating positive and negative loads according to claim 4, wherein the outlet of the high-pressure filter (3) is further connected with a first overflow valve (5) in parallel, the inlet end of the first overflow valve (5) is connected with a hydraulic pipeline between the high-pressure filter (3) and the first one-way valve (7), and the outlet end of the first overflow valve (5) is connected with the oil tank (1) through an oil return filter (4).
  6. 6. A hydraulic system adapted for alternating positive and negative loads according to claim 3, characterized in that the first non-return valve (7) is further connected with a second overflow valve (6), the other end of the second overflow valve (6) being connected with the return line (21).
  7. 7. A hydraulic system adapted for alternating positive and negative loads according to claim 1, characterized in that the relief valve (17) is a constant differential relief valve to maintain a constant inlet-outlet pressure difference.
  8. 8. A hydraulic system adapted for alternating positive and negative loads according to claim 1, characterized in that the relief valve (17) is a proportional relief valve.
  9. 9. The control method suitable for the hydraulic system with alternating positive and negative loads is based on the hydraulic system according to any one of claims 1 to 8, and is characterized in that when the system is in a power failure triggering negative load working condition, high-pressure oil of a power source enters a rodless cavity of a hydraulic cylinder (20), a piston rod of the hydraulic cylinder (20) is driven to extend stably, meanwhile, the high-pressure oil of the power source acts on a left cavity of a proportional throttle valve through a constant-value pressure reducing valve (11) to output constant pressure, the spring pretightening force at the right end of the proportional throttle valve and the outlet pressure of a pressure reducing valve (17) are overcome, the proportional throttle valve is fully opened, and oil return from the rod cavity of the hydraulic cylinder (20) returns to an oil tank (1) through a variable throttle hole (14) and the proportional throttle valve in a fully opened state.
  10. 10. The control method for a hydraulic system with alternating positive and negative loads according to claim 9, wherein when a large negative load condition occurs in a negative load condition, the front-rear pressure difference of the variable orifice (14) increases, the outlet pressure of the pressure reducing valve (17) increases with the increase of the inlet pressure, and acts on the right cavity of the proportional throttle valve to push the valve core of the proportional throttle valve to move left, so as to reduce the valve opening of the proportional throttle valve.

Description

Hydraulic system suitable for alternating positive and negative loads and control method thereof Technical Field The invention belongs to the technical field of hydraulic systems, and particularly relates to a hydraulic system suitable for alternating positive and negative loads and a control method thereof. Background When the hydraulic system works normally or loses power, if the external load is consistent with the output direction of the oil cylinder, a negative load working condition of the hydraulic system is formed, and when the load is suddenly or slowly converted into a driving source from the driving force of the system, the problem of speed runaway can occur, and the system and surrounding personnel are dangerous; In a hydraulic pitch system of a wind generating set, blades are driven by a hydraulic actuating mechanism (oil cylinder), so that high-precision real-time adjustment of a pitch angle during fan pitch opening, feathering and power generation is realized, and the hydraulic pitch system is a core subsystem for guaranteeing safe operation and energy capturing efficiency of the wind generating set; In the system, the load characteristic dynamically changes according to working conditions, namely, when the hydraulic cylinder actively outputs tension to overcome external resistance (such as opening a propeller), the hydraulic cylinder is defined as a positive load working condition, and when the external load is consistent with the output direction of the oil cylinder, the hydraulic cylinder forms a negative load working condition; The large negative load refers to an extreme scene that the emergency feathering is triggered by normal feathering or sudden power failure of a fan, under the extreme scene, the load of tens to hundreds of tons of blades is instantaneously converted into a driving source by a system driving force, namely, an oil cylinder instantaneously or slowly generates positive load and negative load in the process of driving the blades to feathere, during which the piston rod of the oil cylinder still keeps thrust output, so that the blades cannot be retracted at a stable speed, stall phenomenon occurs, and then the blades of the fan stall is caused, and the stall not only threatens the safety of equipment, but also brings serious personal risks to on-site and peripheral personnel; In the current engineering practice, two types of schemes are mainly adopted for hydraulic control under the working condition of large negative load: The applicant finds that the scheme has dynamic adjustment capability, but needs to add a high-frequency response servo valve, a load control system and a standby power supply, so that the cost and design complexity are remarkably increased, the engineering practicability and economy are difficult to meet the severe requirements of the wind power industry, in the high-speed feathering process, the rodless cavity or the rodless cavity is easily sucked empty (cavitation risk is generated) or the instant overpressure of the rodless cavity is easily caused (sealing failure is caused) due to flow matching unbalance; Secondly, the applicant finds that although the components have simple structures, the opening pressure threshold is fixed, the large-range load fluctuation cannot be self-adapted, and under the emergency working condition that the system is completely powered off, the active regulation capability is lacking, the constant back pressure is difficult to maintain due to response delay, and the speed step mutation is extremely easy to cause; In the emergency feathering process, how to enable the hydraulic system to still provide continuous, stable and self-adaptive damping control under the impact of large negative load, and ensure that the blades finish feathering at a safe and constant speed becomes a key bottleneck to be broken through in the prior art. Disclosure of Invention The invention aims to overcome the defects of the prior art, provides a hydraulic system suitable for alternating positive and negative loads and a control method thereof, and effectively solves the problem of speed runaway caused by large negative load under the negative load working condition of the hydraulic system. The aim of the invention is achieved by the following technical scheme: The utility model provides a hydraulic system suitable for positive and negative load is in turn, includes oil tank, power supply and pneumatic cylinder, the power supply respectively with pneumatic cylinder and definite value relief pressure valve are connected, definite value relief pressure valve is connected with the one end of proportional throttle valve and is right the invariable pressure of proportional throttle valve output, the other end of proportional throttle valve with the pneumatic cylinder is connected, proportional throttle valve with be provided with variable orifice between the pneumatic cylinder, the pneumatic cylinder with still be connected with the relief pressure