Parabola pressure characteristic adjustable parameter energy accumulator

Abstract

The invention discloses a parameter-adjustable energy accumulator with parabola pressure characteristics, and aims to solve the technical problems that the pressure of a traditional hydraulic energy accumulator is monotonically increased, oil filling is difficult, and oil pressure cannot be adjusted. According to the technical scheme, an oil cavity piston and an air cavity piston are arranged on the two sides in a shell, an oil inlet is formed in the side wall of an oil cavity, and the side wall of the oil cavity is externally connected with a hydraulic pipeline; the side wall of the air cavity is provided with an air inlet externally connected with a nitrogen source, the rack is connected with an oil cavity piston, the gear is arranged on the shell through a rotating shaft and a bearing and meshed with the rack, the crank is fixedly arranged on the gear, a cylinder body of the first differential cylinder is connected with the crank, the end of a piston rod is hinged to the connecting rod, the connecting rod is hinged to the connecting block, and the connecting block is connected with a cylinder body of the second differential cylinder. The pressure of the liquid cavity is adjusted through the parabola characteristic of the crank sliding block mechanism along with the oil charging and discharging process, the parabola pressure characteristic is achieved in the oil charging and discharging process, namely, the pressure of the oil cavity is increased firstly and then decreased, and the problem that oil is difficult to enter in the later period of oil charging is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydraulic accumulators, and particularly relates to an adjustable-parameter accumulator with a parabolic pressure characteristic. Background Art

[0002] At present, construction machinery has long suffered from the problems of low energy efficiency and high emissions. With the proposal of the "dual carbon" goal, energy conservation and emission reduction are the current development trend in the field of construction machinery. Green, low-carbon, and high-efficiency construction machinery products are the focus of research. For construction machinery with high-frequency operations, there is often a large amount of energy waste in the hydraulic system.

[0003] Hydraulic accumulators play an important role in energy recovery. Currently, the widely used hydraulic accumulators mainly utilize the compression and expansion principles of the gas in the gas chamber to achieve energy charging and discharging. Hydraulic accumulators have the disadvantage of low energy storage density. During the oil filling process, the pressure monotonically increases, resulting in difficult oil filling, inability to fully recover the kinetic and potential energy of construction machinery, and causing energy waste. In addition, for current conventional accumulators, once the gas filling is completed, the pressure characteristics during oil charging and discharging cannot be adjusted and controlled. Summary of the Invention

[0004] The purpose of the present invention is to solve the above problems and provide an adjustable-parameter accumulator with a parabolic pressure characteristic.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: An adjustable-parameter accumulator with a parabolic pressure characteristic, comprising a housing, an oil chamber piston, a rack, a gear, a crank-slider mechanism, a limiting mechanism, a gas chamber piston, a two-position four-way valve, and a stroke feedback closed-loop control system; The oil chamber piston and the gas chamber piston are respectively slidably arranged on the left and right sides inside the housing. An oil chamber is formed between the oil chamber piston and the housing. An oil inlet is provided on the side wall of the oil chamber, and the oil inlet is externally connected to a pressure pipeline. A gas chamber is formed between the gas chamber piston and the housing. An air inlet is provided on the side wall of the gas chamber, and the air inlet fills nitrogen into the gas chamber through a nitrogen source. One end of the rack is horizontally and fixedly connected to the middle of the oil chamber piston, and the other end is suspended. The gear is arranged on the housing through a rotating shaft and bearings, and the gear meshes with the rack; The limiting mechanism includes a limiting block and a limiting device. One end of the limiting device is horizontally and fixedly arranged on the rod extending from the gas chamber piston. A protrusion is provided on the top surface of the limiting device. The limiting block is vertically and fixedly arranged on the top surface inside the housing; The crank-slider mechanism includes a crank, a first differential cylinder, a connecting rod, a connecting block, and a second differential cylinder. The crank is radially fixed on the gear. The bottom surface of the cylinder block of the first differential cylinder is fixedly connected to the free end of the crank. The end of the piston rod of the first differential cylinder is hinged to one end of the connecting rod. The other end of the connecting rod is hinged to one end of the connecting block. The other end of the connecting block is fixedly connected to the bottom surface of the cylinder block of the second differential cylinder. The end of the piston rod of the second differential cylinder is fixedly connected to the limiting device. The stroke feedback closed-loop control system includes a two-position four-way valve, a controller, a three-position four-way proportional direction valve, a hydraulic pump, and a differential cylinder displacement sensor. The two liquid chambers of the second differential cylinder are connected to the two-position four-way valve through pipelines. The two-position four-way valve is electrically connected to the controller. The two liquid chambers of the first differential cylinder are connected to the three-position four-way proportional direction valve through pipelines. The three-position four-way proportional direction valve is electrically connected to the controller and connected to the hydraulic pump through an oil circuit. An overflow valve is provided on the oil circuit between the hydraulic pump and the three-position four-way proportional direction valve. The differential cylinder displacement sensor is arranged on the piston rod of the first differential cylinder and is electrically connected to the controller. The controller uses the PID method for feedback control.

[0006] Further, a plurality of grooves are uniformly provided on the contact surfaces of the oil chamber piston, the air chamber piston and the housing. Sealing rings are provided in the grooves.

[0007] Further, the limiting block is located between the limiting device and the air chamber piston. When the air chamber piston and the protrusion on the limiting device move to contact the limiting block respectively, the rotation angle of the crank is 0° < α < 180°.

[0008] The beneficial effects of the present invention are as follows: 1. The present invention consists of three components, namely a crank-slider mechanism, an air chamber piston and an oil chamber piston, which form an integral piston. Along with the process of charging and discharging oil, the thickness of the integral piston can be freely changed, thereby adjusting the air chamber pressure and realizing the parabolic pressure characteristic during the charging and discharging process, that is, the oil chamber pressure first rises and then falls, which is different from the monotonically rising pressure of the conventional accumulator, and avoids the problem of difficult oil inlet in the later stage of oil charging. 2. The length of the crank of the present invention can be adjusted by the telescopic movement of the first differential cylinder, so that the charging and discharging pressure characteristics of the accumulator can be adjusted. By using the stroke feedback closed-loop control system, without changing the air chamber pressure, the magnitude of the highest pressure during the charging and discharging process can be changed. Different energy storage pressure characteristics can be selected according to the dynamic potential energy of the working mechanism of the construction machinery, effectively storing energy, with stronger applicability and a wider application range. 3. The charging and discharging process of the present invention includes two stages of rising and falling of the oil chamber pressure. Compared with the pressure characteristic of the monotonically rising oil chamber pressure of the conventional accumulator, when the oil inlet volume of the oil chamber is the same, the pressure change range of the oil chamber of the present invention is smaller than that of the conventional accumulator, so its energy storage density is higher. 4. The present invention is applicable to the process of recovering the potential energy of the boom of an excavator. As the boom descends, the oil chamber pressure of the excavator decreases. For a conventional accumulator where the pressure monotonically increases, it is impossible to fully store the potential energy relying solely on the self-weight of the boom. The present invention has the characteristic that the oil chamber pressure decreases in the later stage of oil filling, is applicable to the process of recovering the potential energy of the excavator boom, and can fully recover the potential energy of the boom without additional work, improving the energy storage efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a schematic structural diagram of the present invention; Figure 2 is a schematic diagram of the principle of the parabolic pressure characteristic of the present invention; Figure 3 is a schematic diagram of the working range of the crank rotation angle of the present invention; Figure 4 is a dynamic simulation model diagram of the present invention; Figure 5 is a simulation result diagram of the influence of different crank lengths on the pressure characteristic of the accumulator of the present invention; In the figures: 1 - oil chamber, 2 - housing, 3 - oil chamber piston, 4 - rack, 5 - gear, 6 - crank, 7 - first differential cylinder, 8 - connecting rod, 9 - connecting block, 10 - second differential cylinder, 11 - limit block, 12 - limiting device, 13 - air chamber piston, 14 - air inlet, 15 - air chamber, 16 - two-position four-way valve, 17 - controller, 18 - three-position four-way proportional direction valve, 19 - hydraulic pump, 20 - differential cylinder displacement sensor, 21 - overflow valve. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0010] The present invention will be further described in detail below with reference to the embodiments.

[0011] As Figures 1 - 3 shown, an adjustable-parameter accumulator with a parabolic pressure characteristic includes a housing 2, an oil chamber piston 3, a rack 4, a gear 5, a crank-slider mechanism, a limiting mechanism, an air chamber piston 13, a two-position four-way valve 15, and a stroke feedback closed-loop control system; The oil chamber piston 3 and the air chamber piston 13 are respectively slidably arranged on the left and right sides inside the housing 2. An oil chamber 1 is formed between the oil chamber piston 3 and the housing 2. An oil inlet is provided on the side wall of the oil chamber 1, and the oil inlet is externally connected to a fuel tank. An air chamber 15 is formed between the air chamber piston 13 and the housing 2. An air inlet 14 is provided on the side wall of the air chamber 15, and the air inlet 14 is used to fill the air chamber 15 with pressure. After filling with nitrogen at a set pressure, it is closed. A plurality of grooves are evenly provided on the contact surfaces of the oil chamber piston 3, the air chamber piston 13 and the housing 2, and sealing rings are provided in the grooves. One end of the rack 4 is horizontally fixedly connected to the middle of the oil chamber piston 3, and the other end is suspended. The gear 5 is arranged on the housing 2 through a rotating shaft and bearings, and the gear 5 meshes with the rack 4; The limiting mechanism includes a limiting block 11 and a limiting device 12. One end of the limiting device 12 is horizontally and fixedly arranged in the middle of the air chamber piston 13. There is a protrusion on the top surface of the limiting device 12. The limiting block 11 is vertically and fixedly arranged on the top surface inside the housing 2, located between the limiting device 12 and the air chamber piston 13. When the air chamber piston 13 and the protrusion on the limiting device 12 move to contact the limiting block 11 respectively, the rotation angle α of the crank 6 satisfies 0° < α < 180°, preventing it from rotating to the dead center position and avoiding the discontinuity of motion caused by the dead center; The crank-slider mechanism includes a crank 6, a first differential cylinder 7, a connecting rod 8, a connecting block 9, and a second differential cylinder 10. The crank 6 is radially fixedly arranged on the gear 5. The bottom surface of the cylinder block of the first differential cylinder 7 is fixedly connected to the free end of the crank 6. The end of the piston rod of the first differential cylinder 7 is hinged to one end of the connecting rod 8. The other end of the connecting rod 8 is hinged to one end of the connecting block 9. The other end of the connecting block 9 is fixedly connected to the bottom surface of the cylinder block of the second differential cylinder 10. The end of the piston rod of the second differential cylinder 10 is fixedly connected to the limiting device 12. The second differential cylinder 10 is in a floating state when energized and in a locked state when de-energized; The stroke feedback closed-loop control system includes a two-position four-way valve 16, a controller 17, a three-position four-way proportional direction valve 18, a hydraulic pump 19, and a differential cylinder displacement sensor 20. The two liquid chambers of the second differential cylinder 10 are connected to the two-position four-way valve 16 through pipelines. The two-position four-way valve 16 is electrically connected to the controller 17. The two liquid chambers of the first differential cylinder 7 are connected to the three-position four-way proportional direction valve 18 through pipelines. The three-position four-way proportional direction valve 18 is electrically connected to the controller 17 and is connected to the hydraulic pump 19 through an oil circuit. There is an overflow valve 21 on the oil circuit between the hydraulic pump 19 and the three-position four-way proportional direction valve 18. The differential cylinder displacement sensor 20 is arranged on the piston rod of the first differential cylinder 7 and is electrically connected to the controller 17. The controller 17 uses the PID method to perform feedback control on the telescopic length of the differential cylinder. Without changing the air chamber pressure, the maximum pressure during the oil filling and discharging process can be changed, and different energy storage pressure characteristics can be selected according to the kinetic and potential energy of the working mechanism of the construction machinery.

[0012] As Figure 4 shown, to verify the parabolic pressure characteristic of the present invention, a dynamic simulation model was established using the dynamic simulation software Simulation X. A new type of accumulator simulation model was established using the cylinder, oil cylinder, crank-slider mechanism, and gear-rack models in the component library. The specific parameter settings are as follows: the inner diameter of the cylinder is 100 mm, the inner diameter of the oil cylinder is 100 mm, the initial inflation pressure of the air chamber is 10 Mpa, the length of the connecting rod is 300 mm, the module of the gear is 3 mm, the number of teeth is 50, the pump flow rate for oil chamber filling is 100 l / min, and the crank movement angle is from 0° to 180°; As Figure 5As shown in the figure, to compare the influence of different lengths of the crank 6 on the pressure characteristics of the accumulator, the lengths of the crank 6 were set to 50 mm and 70 mm respectively for simulation, and the variation curves of the oil chamber pressure with different crank lengths were obtained. The simulation results show that: during the oil filling process of the present invention, the pressure in the oil chamber satisfies the parabolic variation trend, that is, "first increases and then decreases"; the pressure in the oil chamber with a 70-mm crank is higher than that in the oil chamber with a 50-mm crank, that is, the longer the crank 6, the greater the pressure in the oil chamber 1.

[0013] The working process of the present invention is as follows: When the accumulator stores energy, the external pipeline injects oil into the oil inlet, the pressure in the oil chamber 1 increases, the high-pressure oil pushes the oil chamber piston 3 to move leftward, drives the rack 4 to make a linear motion to the left, the rack 4 drives the gear 5 to rotate clockwise, the gear 5 drives the crank 6 to rotate, the crank 6 drives the connecting rod 8 to rotate through the first differential cylinder 7, and the connecting rod 8 pushes the connecting block 9 and the second differential cylinder 10 to move linearly to the left, and then drives the air chamber piston 13 to move leftward through the limiting device 12, compressing the nitrogen in the air chamber 15 to store energy; When the accumulator releases energy, the high-pressure nitrogen in the air chamber 15 pushes the air chamber piston 13 to move rightward, pushes the limiting device 12, the second differential cylinder 10, and the connecting block 9 to move rightward, and then drives the crank 6 and the gear 5 to rotate counterclockwise through the connecting rod 8, driving the rack 4 and the gear 5 to move rightward, so as to release energy; The present invention is composed of a crank-slider mechanism, an air chamber piston 13, and an oil chamber piston 3, which together form an integral piston. Along with the charging and discharging process, by utilizing the "parabolic" characteristic of the crank torque of the crank-slider mechanism, the oil chamber pressure is adjusted to achieve the parabolic pressure characteristic during the charging and discharging process, that is, the oil chamber pressure first rises and then falls, which is different from the monotonically increasing pressure of a conventional accumulator, avoiding the problem of difficult oil inlet in the later stage of oil filling.

[0014] During the charging and discharging process of the accumulator, by extending and retracting the piston rod of the first differential cylinder 7, the length of the crank can be adjusted, and further the pressure in the oil chamber of the accumulator can be adjusted. When the volume of the stored oil is certain, the greater the extension length of the piston rod of the first differential cylinder 7, the greater the pressure peak in the oil chamber 1. When the piston rod of the first differential cylinder 7 extends, the controller 17 controls the two-position four-way valve 16 to make the second differential cylinder 10 energized and in a floating state.

[0015] When the preset elongation length L1 of the piston rod of the first differential cylinder 7 is input into the controller 17, the controller 17 drives the elongation of the first differential cylinder 7 by controlling the three-position four-way proportional direction valve 18. The differential cylinder displacement sensor 20 real-time monitors the actual elongation length L2 of the first differential cylinder 7. When L2≠L1, the differential cylinder displacement sensor 20 transmits the collected actual elongation length L2 to the controller 17. The controller 17 analyzes the data and controls the operation of the hydraulic pump 19 to supply oil to the three-position four-way proportional direction valve 18. The excess oil is discharged from the relief valve 21. After the three-position four-way proportional direction valve 18 is compensated for oil supply by the hydraulic pump 19, it further controls the piston rod of the first differential cylinder 7 to elongate or shorten, so that L2 continuously approaches L1. Through the PID method of the stroke feedback closed-loop control system, the deviation is detected and corrected until L2 = L1, realizing the compensation of the telescopic length of the crank 6 and making the operation process of the present invention more accurate.

[0016] During the operation process, through the limitation of the limit mechanism, the rotation angle of the crank 6 is 0°<α<180°, preventing it from rotating to the dead point position and avoiding the discontinuity of motion caused by the dead point.

Claims

1. A parabolic pressure characteristic adjustable parameter accumulator, characterized in that: It comprises a housing (2), an oil chamber piston (3), a rack (4), a gear (5), a crank slider mechanism, a limit mechanism, an air chamber piston (13), a two-position four-way valve (15) and a stroke feedback closed-loop control system; The oil chamber piston (3) and the air chamber piston (13) are slidably arranged on the left and right sides of the housing (2), respectively; an oil chamber (1) is formed between the oil chamber piston (3) and the housing (2); an oil inlet is provided on the side wall of the oil chamber (1), and the oil inlet is externally connected to a pressure pipeline; an air chamber (15) is formed between the air chamber piston (13) and the housing (2); an air inlet (14) is provided on the side wall of the air chamber (15), and nitrogen is filled into the air chamber (15) through a nitrogen source through the air inlet (14); one end of the rack (4) is horizontally fixedly connected to the middle of the oil chamber piston (3), and the other end is suspended; the gear (5) is arranged on the housing (2) through a rotating shaft and a bearing, and the gear (5) is meshed with the rack (4); The limiting mechanism comprises a limiting block (11) and a limiting device (12); one end of the limiting device (12) is horizontally fixed on a rod extending from the air cavity piston (13); a protrusion is provided on the top surface of the limiting device (12); and the limiting block (11) is vertically fixed on the top surface of the housing (2); The crank slider mechanism comprises a crank (6), a first differential cylinder (7), a connecting rod (8), a connecting block (9) and a second differential cylinder (10); the crank (6) is fixedly arranged on the gear (5) in a radial direction; the bottom surface of the cylinder body of the first differential cylinder (7) is fixedly connected to the free end of the crank (6); the end of the piston rod of the first differential cylinder (7) is hinged to one end of the connecting rod (8); the other end of the connecting rod (8) is hinged to one end of the connecting block (9); the other end of the connecting block (9) is fixedly connected to the bottom surface of the cylinder body of the second differential cylinder (10); and the end of the piston rod of the second differential cylinder (10) is fixedly connected to a limiting device (12); The stroke feedback closed-loop control system comprises a two-position four-way valve (16), a controller (17), a three-position four-way proportional directional control valve (18), a hydraulic pump (19) and a differential oil cylinder displacement sensor (20); the two liquid chambers of the second differential cylinder (10) are connected to the two-position four-way valve (16) via a pipeline; the two-position four-way valve (16) is electrically connected to the controller (17); the two liquid chambers of the first differential cylinder (7) are connected to the three-position four-way proportional directional control valve (18) via a pipeline; the three-position four-way proportional directional control valve (18) is electrically connected to the controller (17) and connected to the hydraulic pump (19) via an oil circuit; a relief valve (21) is provided on the oil circuit between the hydraulic pump (19) and the three-position four-way proportional directional control valve (18); the differential oil cylinder displacement sensor (20) is arranged on the piston rod of the first differential cylinder (7) and is electrically connected to the controller (17); the controller (17) adopts a PID method for feedback control.

2. The parabolic pressure characteristic adjustable parameter accumulator according to claim 1, characterized in that: A plurality of grooves are evenly arranged on the contact surfaces of the oil chamber piston (3), the air chamber piston (13) and the housing (2), and sealing rings are arranged in the grooves.

3. The parabolic pressure characteristic adjustable parameter accumulator according to claim 1, characterized in that: The limit block (11) is located between the limit device (12) and the air chamber piston (13), and when the protrusions on the air chamber piston (13) and the limit device (12) respectively move to contact the limit block (11), the rotation angle of the crank (6) is 0°<α<180°.

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