Research On The Piston Pumps Using High-speed On-off Valve With Phase Shift Of PWM Control Method

Problems about slow response speed and chattering phenomenon existing in common piston pumps using high-speed on-off valve makes them unable to adapt the requirements of high power density and large flow rate for hydraulic components development.So this paper presents a piston pump using high-speed on-off valve with phase shift of PWM control method.The main contents includes the optimization of the structure of high-speed on-off valve and its control method and the structure of piston pump.This paper derives from the Great Project supported by Fujian Provincial Department of Science and Technology of China and the Innovative Platform Construction Project of Fujian Province.This paper selects one type of axial piston pump of 21t hydraulic excavator as the research object.Firstly,introduce the overview and current research of piston pumps controlled by high-speed on-off valve.By investigating the home and abroad research findings on piston pumps controlled by high-speed on-off valve,the research ideas of this paper and content of the research is determined and the difficulty of this paper is also pointed out.Secondly,base on the existing chattering phenomenon of the digital control variable-displacement structure,one improved PWM control strategy and its mech-anism is provided.By controlling the phases of the energizing of the valves,chattering caused by high-speed on-off valves is weaken effectively.And the reverse spring ensures the stability of variable-displacement mechanism.Thirdly,the performance parameters of existing high-speed on-off valves are compared.According to the result of comparison analysis,a structure of large flow rate high-speed on-off valve is presented and analyzed to improve the response speed of piston pump controlled by high-speed on-off valve.Fourthly,to further promote the competitive advantages of digital variable-displacement pump,a high power density piston pump and a new type of valve plate with three-level gain are put forward.And its feasibility is demonstrated by calculating the mathematical model and fluid simulation.Finally,by quantitative analysis and experimental verification,the respective characteristics of the digital control type of variable-displacement and proportional control type are drawn.The innovation of this paper is that it provides a new idea for the design of a large flow servo-control variable displacement axial piston pump with high precision,power denstiy and efficiency.A new type of variable-displacement mechanism and its control method is presented and it not only successfully reduces the amplitude of chattering,but it also ensures the stability of variable-displacement mechanism.Then a self-compensation high-speed on-off valve is proposed for the first time which makes sure the valve is well sealed.And the influence factors on the density of axial piston pump are derived from the basic structure pump model.In addition a new structure of cylinder block with bidirectional inclined cylinder block hole is presented which turns the self-priming property from differential pressure to differential pressure adding centrifugal force so that the self-priming ability increases significantly.Finally,the respective characteristics of the digital control type of variable-displacement and proportional control type are drawn by quantitative analysis and experimental verification.The major achievements of this paper include 4 articles and 3 invention patents which are in examination as to substance.