Pressure vessel, pressure increasing device, finishing device, and method for increasing the pressure of hydraulic operating oil

Abstract

The pressure increasing container includes a first straight segment (11) with a length-to-diameter ratio greater than 5, which is arranged in order from upstream to downstream, a second arc segment (12) that is a 1 / 4 arc and is a concave arc, and a third straight segment (13) with a length-to-diameter ratio less than 3. Among them, the first straight segment (11) and the third straight segment (13) are coaxial and parallel, and the downstream end of the third straight segment (13) is the discharge end of the pressure increasing container. The ratio of the cross-sectional areas of the first straight segment (11) and the third straight segment (13) is 2.5 to 3. Due to the synergistic effect of each segment configuration of the pressure increasing container, it is ensured that the output pressure is large and stable. Furthermore, a pressure increasing device, a finishing device, and a method for increasing the pressure of hydraulic operating oil are provided.

Description

Technical Field

[0001] The present invention relates to the field of precision machining of internal flow paths, and particularly to a pressure increasing container, a pressure increasing device, a finishing device, and a method for increasing the pressure of hydraulic working oil.

Background Art

[0002] Parts having a fine and complex internal flow path structure are extremely widely applied in industrial fields such as aerospace, shipbuilding, nuclear, automotive, and mold. In particular, parts related to fluid power systems often have complex internal cavity structures such as fine flow paths, small-diameter deep holes, and communication between fine flow paths and small-diameter deep holes. For example, fuel nozzles of various engines in aviation / aerospace / shipbuilding / automotive, heat exchangers, hydraulic modules, oil passage control throttles, etc., perform functions such as fluid transportation, exchange, or application of hydraulic pressure.

[0003] Process technologies capable of machining fine and complex internal flow paths include precision machining, femtosecond / water jet guided / long pulse laser machining, spark machining, and additive manufacturing (3D printing), etc. Except for additive manufacturing technology, the fine and complex internal flow path structures machined by other single processes are relatively simple, with a small ratio of length to diameter, and it is necessary to combine with other combined processes such as welding to machine fine and complex internal flow paths. For fine and complex internal flow paths by precision machining, problems such as burrs, sharp corners at the corners, and steps at the machining joints occur. On the surface of the internal flow path by femtosecond laser machining, attached residue particles and the "step" effect on the surface occur. On the surface of the internal flow path by water jet guided / long pulse laser and spark machining, a remelted layer occurs. Additive manufacturing (3D printing) is a technology that separates the component model with a complex three-dimensional structure into two-dimensional structures and stacks and forms them layer by layer, enabling the integrated forming of complex and fine and complex internal flow path components, so its applications in industrial fields such as aerospace, automotive, and molds are increasing more and more. However, due to its own process characteristics such as temperature gradient and layer-by-layer forming during the component forming process, additive manufacturing technology generates semi-sintered or adhered powder particles on the surface of the internal flow path of the component and the "step" effect on the surface.

[0004] Burrs during machining, particles adhering and sintering in internal channels during femtosecond laser machining, and adhering powder on the surface of internal channels during additive manufacturing, etc., affect the performance and safety of parts. When burrs, adhering residue particles or adhering powder fall off due to the high-speed friction between the fluid flowing into the internal channel and the surface layer, they become extra and diffuse with the fluid, block the oil channel, or cause mechanical wear failure, leading to serious safety accidents. An inner surface with a large roughness is likely to become a fatigue crack source during long-term use, and in a high-temperature oil channel system, carbon accumulation is also likely to occur. The blade tip marks on the surface of the channel during machining, the sharp corners of the corners or the steps at the machining joints, and the "step" phenomenon on the surface of the internal channel during femtosecond laser and additive manufacturing are likely to cause turbulence, eddy currents and a sharp increase in fluid frictional drag during the fluid movement process, further leading to fluid runaway, vibration, and reducing the service life of the parts. The rough surface may generate a large number of cavitation bubbles in the fluid, affecting combustion and hydraulics, and may also cause cavitation corrosion. For the internal channels and communicating small holes of parts made of specific materials such as hollow blades, fine cracks are likely to occur on the surface of the remelting layer, and the parts fail early. Therefore, it is required to reduce the thickness of the remelting layer or not allow the appearance of the remelting layer.

[0005] Therefore, when machining the surface of the internal channels of fluid power parts by technologies such as precision machining, femtosecond / water jet guided / long pulse laser machining, spark machining, additive manufacturing (3D printing), etc., it brings adverse problems such as burrs, adhering powder, residues such as sintered particles, rough surfaces, remelting layers, etc. It is necessary to use appropriate surface finishing technologies to remove these adverse effects and meet the performance requirements of the products.

[0006] However, currently, there is no technology that can effectively finish the surface of a fine and complex internal flow path. Therefore, for a fine and complex internal flow path workpiece manufactured by additive manufacturing, its inner surface roughness generally only has the original average roughness Ra of 6.3 μm or more after additive manufacturing. There are no products with a surface optimum roughness Ra of the internal flow path of 1.6 μm or less. For fine and complex internal flow path workpieces by laser processing and spark processing, there are no products with a surface optimum roughness Ra of the internal flow path of 0.8 μm or less. Also, for fine and complex internal flow path workpieces by machining, there are no products with a surface optimum roughness Ra of the internal flow path of 0.4 μm or less. Currently, when a fine and complex internal flow path has complex deformed channels such as S-shaped bending, L-shaped bending, U-shaped bending, and O-shaped bending, it cannot be achieved by machining that can only perform linear feed, and can only be achieved by methods such as additive manufacturing. Therefore, currently, there are no products with a surface optimum roughness Ra of 1.6 μm or less for the fine, deformed, and complex internal flow path surface by additive manufacturing.

Summary of the Invention

[0007] An object of the present application is to provide a pressure increasing container, a pressure increasing device, a finishing device, and a method for increasing the pressure of a hydraulic operating oil.

[0008] In a first aspect, the present application provides a pressure increasing container used in a pressure increasing device. The pressure increasing container includes a first straight segment with a ratio of length to diameter greater than 5, a second arc segment that is a 1 / 4 arc and is a concave arc, and a third straight segment with a ratio of length to diameter less than 3, which are arranged in order from upstream to downstream. The first straight segment and the third straight segment are coaxial and parallel. The downstream end of the third straight segment is the discharge end of the pressure increasing container. The ratio of the cross-sectional area of the first straight segment to the third straight segment is 2.5 to 3.

[0009] In the technical solution of the embodiment of the present application, the pressure increasing container adopts a configuration of a first straight line segment, a second arc segment that is a 1 / 4 arc and is a concave arc, and a third straight line segment. Due to the synergistic effect of the three, after the hydraulic operating oil passes through the pressure increasing device, a large and stable pressure is output. The principle is described as follows. The function of the configuration of the first straight line segment is as follows. Under high hydraulic pressure, when the hydraulic operating oil becomes a compressible fluid, there will be a volume loss, but the long movement stroke of the piston can compensate for the volume loss of the hydraulic operating oil. The second arc segment, due to its concave arc configuration, realizes a larger surface area and disperses the hydraulic pressure, so that the hydraulic pressure does not generate a high concentrated pressure on the wall surface due to the rolling force, and the forces and angle changes received by the mass elements of the fluid also have a long movement stroke and are stably consistent. Furthermore, it realizes a guiding effect on the hydraulic operating oil, laminar-flow moves the fluid to the throat at a low speed, and the concave arc provides a pressing force to the fluid, contributing to the fluid being pressed and densified, and increasing a larger and more stable hydraulic force. Also, by providing the third straight line segment and making the ratio of the length to the diameter greater than 3, it is possible to avoid the final output hydraulic force becoming unstable due to the too long movement stroke of the fluid and the increase in turbulent flow in the boundary layer. The relatively short stroke of the third segment is beneficial to the laminar flow state of the fluid, the outflowing hydraulic operating oil is stable, and the accuracy and stability of the final hydraulic pressure adjustment are improved. And, by the configuration that the first straight line segment and the third straight line segment are coaxial and parallel, and the ratio of the cross-sectional areas of the first straight line segment and the third straight line segment is 2.5 to 3, it is possible to further ensure that the hydraulic operating oil flows stably and is pressure increased in the pressure increasing container. Due to the synergistic effect of the above means, the output pressure of the pressure increasing device becomes 2.5 MPa to 45 MPa, the adjustment accuracy becomes 0.01 MPa to 0.1 MPa, the deviation of the output pressure is less than 0.1%, and it can be ensured that the output pressure is large and stable.

[0010] In some embodiments, the ratio of the length of the first straight line segment, the radius of the second arc segment, and the length of the third straight line segment is 11:5:4.

[0011] In some embodiments, the fillet radius at the connection of the first straight segment and the second arc segment is 0.1 mm to 0.5 mm.

[0012] In some embodiments, the material of the pressure increasing container is steel.

[0013] In some embodiments, the material of the pressure increasing container is 45# steel.

[0014] In some embodiments, the inner wall of the pressure increasing container has a roughness Ra of 0.1 μm to 0.4 μm, a roundness of 100 μm or less, and a cylindricity of 200 μm or less.

[0015] In a second aspect, the present application provides a pressure increasing device, comprising the pressure increasing container described in the first aspect. The pressure increasing container has hydraulic operating oil inside. The piston is provided in the pressure increasing container and is used to receive a driving force on one side. The piston is movable along the container wall of the first straight segment so as to push the hydraulic operating oil on the other side of the piston and discharge it from the downstream end of the third straight segment.

[0016] In some embodiments, the driving force received by the piston is 1 MPa to 15 MPa, and the output pressure is 2.5 MPa to 45 MPa.

[0017] In a third aspect, the present application provides a finishing device. In the finishing device comprising a thrust system, a sealed system for accommodating a finishing medium for performing finishing, and a transport pipeline system connected to the sealed system, the thrust system can push the finishing medium accommodated in the sealed system by applying a thrust to the sealed system so that it passes through the transport pipeline system and is sent to a workpiece to be finished. Among them, the thrust system comprises a hydraulic pump and the pressure increasing device described in the second aspect. The hydraulic pump provides the driving force to the piston of the pressure increasing device, and the hydraulic operating oil is pressurized and discharged by the pressure increasing device.

[0018] In some embodiments, the thrust system further comprises a motor and a vertical plunger pump. The hydraulic pump driven by the motor pushes the piston, and the hydraulic working oil is pressurized by the pressure increasing device and discharged into the vertical plunger pump. The vertical plunger pump is connected to the sealed system to apply pressure to the finishing medium contained in the sealed system.

[0019] In some embodiments, the pressure provided to the sealed system by the thrust system is greater than 50 MPa, the adjustment accuracy is 0.01 MPa to 0.1 MPa, and the deviation of the output pressure is less than 0.1%.

[0020] In a fourth aspect, the present application provides a method for increasing the pressure of hydraulic working oil, which includes pushing the hydraulic working oil so that the hydraulic working oil is pressurized and discharged through a first straight segment, a second arc segment, and a third straight segment in sequence. Among them, the ratio of the length to the diameter of the first straight segment is greater than 5, the second arc segment is a 1 / 4 circular arc and is a concave arc, the ratio of the length to the diameter of the third straight segment is less than 3, the first straight segment and the third straight segment are coaxial and parallel, and the ratio of the cross-sectional areas of the first straight segment and the third straight segment is 2.5 to 3.

Brief Description of the Drawings

[0021] The above and other features, properties, and advantages of the present invention will become more apparent from the following description of the related attached drawings and embodiments. It should be noted that the attached drawings are all illustrative and are not drawn under equal ratio conditions, and should not be regarded as limiting the actual protection scope claimed by the present invention.

[0022]

Figure 1

Figure 2

Figure 3

Best Mode for Carrying Out the Invention

[0023] The following discloses various embodiments or examples for implementing the above-described theme technical solution. For the sake of simplifying the disclosure, specific examples of each element and arrangement are described below, but these are merely examples and do not limit the protection scope of the present invention. "One embodiment", "an embodiment", and / or "some embodiments" mean features, structures, or special points related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "an embodiment" or "one embodiment" or "alternative embodiment" mentioned two or more times at different positions in this specification does not necessarily refer to the same embodiment. Furthermore, some features, structures, or special points in the expressions such as some embodiments, other embodiments, still other embodiments, etc. of the present application may be appropriately combined.

[0024] In the present application, flowcharts are used to explain the operations performed by the system according to the embodiments of the present application. It should be understood that the previous or subsequent operations are not necessarily precisely executed in order. Other operations can also be added to these processes, or the operations of one step or multiple steps can be removed from these processes.

[0025] Also, the average roughness described below is the case where a plurality of regions are selected and measured on the surface to be measured, and the average value is taken to obtain the average roughness of the measured surface. The optimum roughness described below is the case where a plurality of regions are selected and measured on the surface to be measured, and the minimum value is taken to obtain the optimum roughness of the measured surface. For example, when performing roughness measurement, for example, a certain region for roughness measurement is a pipeline segment with a length of 8 mm. In the pipeline to be measured, a plurality of pipeline segments with a length of 8 mm can be selected and measured to obtain the minimum value.

[0026] Parts with fine and complex internal flow path structures are extremely widely applied in industrial fields such as aerospace, ships, nuclear, automobiles, and molds. However, when processing the surface of the internal flow path of fluid power parts by current processing processes, such as precision machining, femtosecond / water jet guided / long pulse laser processing, spark processing, additive manufacturing (3D printing), etc., it brings adverse problems such as burrs, residues such as adhered powder and sintered particles, rough surfaces, and remelted layers. It is necessary to remove these adverse effects by appropriate surface finishing techniques to meet the performance requirements of the products.

[0027] Currently, for fine internal flow path work by additive manufacturing, products with an optimal surface roughness Ra of the internal flow path of 1.6 μm or less do not appear. For fine internal flow path work by laser processing and spark processing, products with an optimal surface roughness Ra of the internal flow path of 0.8 μm or less do not appear. Also, for fine internal flow path work by machining, products with an optimal surface roughness Ra of the internal flow path of 0.4 μm or less do not appear. However, if the fine internal flow path has a special-shaped flow path structure such as S-shaped bending, L-shaped bending, U-shaped bending, or O-shaped bending, it cannot be achieved by linear feed machining and can only be achieved by additive manufacturing, etc. Therefore, currently, products with an optimal surface roughness Ra of the internal flow path of 1.6 μm or less by additive manufacturing do not appear.

[0028] The inventor conducted in-depth research, tried and compared various finishing methods for different internal flow path surfaces, and discovered the following. When the internal flow path diameter of the part is large (>3 mm), the ratio of length to diameter is small (<50:1), and it extends in a substantially straight line, finishing can be performed by general methods such as manual polishing, chemical, electrochemical, plasma, magnetic force, magnetorheology, abrasive flow, water jet, and ultrasonic. However, for fine internal flow paths with a small internal flow path diameter (3 mm or less) and a large ratio of length to diameter (50:1 or more), (1) The abrasive flow technology was adopted, and the inner cavity was finished by a pressing and grinding mechanism using a finishing medium of a semi-solid ointment with high rigidity. However, the inventor found that for a creep fluid in a state where the Reynolds number is extremely small, it is difficult to achieve uniform processing through a complex long-distance micro-channel, and it is easy to be blocked at bends and dead ends. If forced to pass through, the channel may be deformed or cracked. Even if it barely passes through an internal channel with a length-to-diameter ratio of 50:1 or more, the pressure and flow velocity rapidly decay as the fluid travel increases. The port of the internal channel becomes "excessive grinding and polishing", while the inside has too much pressure and flow velocity loss and becomes "ungrinded and unpolished". In addition, a colloidal abrasive medium insoluble in water tends to remain at the curves and dead ends of the internal channel and is difficult or impossible to be completely removed after processing. (2) The abrasive water jet technology, also called fine abrasive slurry jet, high-speed flow · high-speed water particle finishing, was adopted. By applying hydraulic pressure to the water jet nozzle, a water jet with abrasives is ejected from the nozzle, and the surface material of the workpiece is washed away by its impact kinetic energy. However, due to the short distance between the water jet nozzle and the part surface, the abrasive water jet technology is not suitable for acting on a fine internal channel with a small inner diameter (3 mm or less) and a large length-to-diameter ratio (50:1 or more) of the internal channel. (3) Although magnetic finishing technology is adopted, only slight surface finishing can be performed on the surface of the internal flow path with a diameter larger than 3 mm and extending in a substantially straight line. It is impossible to perform effective surface finishing on the fine and complex internal flow paths of S-shaped bending, L-shaped bending, U-shaped bending, O-shaped bending, and spiral bending with a diameter of 3 mm or less and extending three-dimensionally. The reasons are as follows. Magnetic finishing is a flexible process that uses relatively large-sized magnetic needle abrasives and is based on the principle that the convex and concave points on the surface are processed simultaneously under the action of the applied magnetic field. Therefore, only slight surface finishing improvement can be performed on the surface by these flexible processing means. Even if the material removal amount is large, the "step" effect on the surface cannot be significantly improved, the surface roughness cannot be reduced, the powder and particles adhering to the surface cannot be significantly peeled off, and the burrs cannot be improved. Also, since this method is restricted by the movement of the magnetic field, it cannot handle the finishing of complex internal flow paths extending three-dimensionally in parts. (4) Although the chemical finishing method is adopted, when the diameter of the internal flow path is small, the amount of corrosive solution that can be accommodated is small, the efficiency of the chemical finishing method is extremely low, and local reaction bubbles may accumulate and even prevent finishing. (5) Although electrochemical, plasma finishing, and ultrasonic methods are adopted, it is difficult to arrange the imitation electrodes in the narrow and three-dimensionally extending flow paths including S-shaped bending, L-shaped bending, U-shaped bending, O-shaped bending, and spiral bending. Therefore, it is impossible to finish the fine and complex internal flow paths.

[0029] Also, regarding (4) and (5), methods such as chemical, electrochemical, and plasma finishing may cause various types of corrosion and alteration layer defects to the fine structure of the flow path substrate. The corrosive liquid and reaction gas also have an adverse impact on the environment and equipment. At the same time, (4) and (5) are also flexible processing means and have similar drawbacks to (3). Only slight surface finishing improvement can be performed on the surface. Even if the material removal amount is large, the "step" effect on the surface cannot be significantly improved, the surface roughness cannot be reduced, and the powder, particles, and burrs adhering to the surface cannot be significantly peeled off.

[0030] As described above, as a result of intensive research, the inventor has found that in the above processing method, it is difficult to finish the deep part of the fine internal flow path structure, and / or the finished quality is not ideal for the fine internal flow path structure. Therefore, the inventor has discovered that it is difficult to apply it to the finishing process of the fine internal flow path.

[0031] Based on the above, the inventor further studied deeply and invented a surface finishing method for the fine internal flow path. A two-phase flow finishing medium with a liquid phase viscosity of less than 1000 cP is adopted. The flow velocity of the two-phase flow finishing medium in the fine internal flow path is increased to be greater than 5 m / s, and the flow rate flowing into the inside at one end of the fine internal flow path reaches the saturation value of the flow rate that can be accommodated by the diameter of the fine internal flow path. By making the liquid pressure inside the internal flow path in a state where the pressure accumulates, a means for the liquid to reach the saturation flow rate with respect to the fine internal flow path is formed. That is, by the synergistic effect of the low-viscosity liquid phase, the fluid flow velocity of the finishing medium, and the saturation flow rate, the problem of the finishing process of the fine internal flow path is solved. The principle is described as follows. First, due to the synergistic effect of the low-viscosity liquid phase, the fluid flow velocity, and the saturation flow rate, the finishing medium can smoothly enter the fine and complex internal flow path and form a state similar to a non-Newtonian fluid in the fine and complex internal flow path. The fluid boundary layer is parallel to the surface of the internal flow path. The abrasive grains in the "knife-like" hard non-Newtonian fluid realize the targeted processing of the surface convex points by shear friction. In addition, due to the synergistic effect of the above three factors, a micro-cutting force due to friction is obtained between the abrasive grains in the finishing medium and the surface of the fine and complex internal flow path. Therefore, without being limited by the material of the fine and complex internal flow path, the surface optimum roughness can be made to coincide with the range of the average contact length of the abrasive grain cutting edge, and even a super mirror surface quality with a surface optimum roughness Ra of 0.05 μm can be realized, breaking through the limitations of the principles of abrasive flow and water jet technology. The principle is described as follows. Since the cutting mechanism of the abrasive flow technology lies in the volume force generated by the pressing of the abrasive grains against the surface, when processing metals with low hardness and polymer flexible materials, dents and pits are likely to occur (Ra > 0.8 μm). The cutting force in the abrasive water jet technology is the erosion force caused by the impact of the abrasive grains against the surface. When processing soft metals, the surface is likely to be roughened (Ra > 0.8 μm).

[0032] Since the inventor needs to perform finishing on the workpiece in a high-speed and high-pressure state for the finishing medium, it is discovered that it is necessary to provide a large and stable pressure to the finishing medium by the thrust system of the finishing device. However, the conventional pressure boosting device that boosts pressure by a piston has difficulty in outputting a stable and large hydraulic pressure.

[0033] Based on this, the inventor conducted in-depth research and designed the pressure-boosting container of the pressure-boosting device, adopting a configuration consisting of a first straight segment, a second arc segment which is a 1 / 4 circular arc and a concave arc, and a third straight segment. Through the synergistic effect of these three components, it is realized that after the hydraulic operating oil passes through the pressure-boosting device, a large and stable pressure is output. The principle is described as follows. The function of the first straight segment configuration is as follows. Under high hydraulic pressure, when the hydraulic operating oil becomes a compressible fluid, volume loss occurs, but the long movement stroke of the piston can compensate for the volume loss of the hydraulic operating oil. The second arc segment, due to its concave arc configuration, realizes a larger surface area and disperses the hydraulic pressure, so that the hydraulic pressure does not generate a high concentrated pressure on the wall surface due to the rolling force, and the forces and angle changes received by the mass elements of the fluid also have a long movement stroke and are stably consistent. Furthermore, it realizes the guiding effect on the hydraulic operating oil, makes the fluid flow in a laminar motion to the throat at a low speed, and provides a pressing force on the fluid by the concave arc, contributing to the pressing and densification of the fluid and raising a larger and more stable hydraulic force. Also, by providing the third straight segment and making the ratio of the length to the diameter less than 3, it is possible to avoid the instability of the finally output hydraulic force caused by the over-long movement stroke of the fluid and the increase of turbulent flow in the boundary layer. The relatively short stroke of the third segment is beneficial to the laminar flow state of the fluid, the outflowing hydraulic operating oil is stable, and the accuracy and stability of the final hydraulic pressure adjustment are improved. And the first straight segment and the third straight segment are coaxial and parallel, and with the ratio of the cross-sectional areas of the first straight segment and the third straight segment being 2.5 to 3, it can be further ensured that the hydraulic operating oil flows stably and is pressure-boosted in the pressure-boosting container. Through the synergistic effect of the above means, the output pressure of the pressure-boosting device reaches 2.5 MPa to 45 MPa, the adjustment accuracy reaches 0.01 MPa to 0.1 MPa, the deviation of the output pressure is less than 0.1%, and it can be ensured that the output pressure is large and stable. The finishing medium ensures the stability of the flow rate and flow volume during the finishing process, and ensures the effect of the finishing process.

[0034] The pressure vessel of the pressure boosting device disclosed in the embodiments of the present application realizes providing a large and stable pressure to the finishing medium when the finishing device operates. Thereby, the corresponding finishing medium has a high-speed movement greater than 5 m / s during processing, and stably provides shear friction by a hard non-Newtonian fluid like a blade to the workpiece, realizes the targeted processing of surface convex points, and further generates a high fine cutting force on the abrasive grains. It should be understood that, however, what is disclosed in the embodiments of the present application can be applied not only to the described finishing method and finishing device to provide a large and stable pressure, but also to the pressure boosting of hydraulic operating oil in other devices.

[0035] First, to understand the effect of the pressure boosting device of the present application, a surface finishing method and a finishing device for a fine internal flow path to which the pressure boosting device can be applied will be described.

[0036] Referring to FIG. 1, the present application provides a surface finishing method for an internal flow path, and the method includes using a liquid-solid two-phase flow finishing medium with a liquid-phase viscosity less than 1000 cP and a solid phase being abrasive grains, applying a predetermined pressure to the finishing medium so that the finishing medium flows in the fine internal flow path at a flow rate greater than 5 m / s, and the flow rate of the finishing medium flowing into the fine internal flow path from one end of the fine internal flow path reaches the saturation value of the flow rate that can be accommodated by the diameter of the fine internal flow path, and the hydraulic pressure inside the internal flow path is in a state where the pressure accumulates.

[0037] The liquid here has the property that its viscosity is less than 1000 cP. In this application, all descriptions regarding viscosity values refer to the Ubbelohde viscosity at normal temperature (around 25°C). The optimal value of the viscosity of the liquid phase corresponding to the finishing methods for fine internal flow paths with different materials, dimensions, and initial average roughness can be obtained by continuously increasing the viscosity based on the lower limit value. Currently, the lower limit value of the viscosity in the examples is about 50 cP. Through a large amount of test data, the inventor has obtained that for fine internal flow paths of general materials such as titanium alloys, superalloys, steels, ceramics, aluminum alloys, and polymer materials, in order to reach the target roughness value after finishing, the viscosity of the liquid phase needs to be at least 50 cP. The critical value of 1000 cP here is not generally the optimal value either, but rather the limit value for the finishing medium to flow continuously, smoothly, and stably through the fine internal flow path.

[0038] Taking the aqueous liquid phase as an example for the liquid phase described in the examples, a certain thickening agent is added to deionized water so that the aqueous liquid has a certain viscosity. The beneficial effects of using an aqueous liquid are that it is low-cost, easily available, environmentally friendly, and the finishing medium is easy to clean after the finishing is completed. However, it is understood that the liquid phase here is not limited to aqueous liquids as long as the viscosity μ is less than 1000 cP.

[0039] The material of the solid-phase abrasive grains may be common abrasive grain materials such as carbide ceramics including silicon carbide, tungsten carbide, etc., oxide ceramics including aluminum oxide, zirconium oxide, cerium oxide, etc., nitride ceramics including boron nitride, chromium nitride, etc., and natural minerals including diamond / sand, mica, quartz, kunlunite, etc. Preferably, it may be one or more combinations of diamond / sand and oxide ceramics.

[0040] When selecting the particle size and mass concentration of abrasive grains, it is common to gradually increase them based on the lower limit to obtain the range of optimal values. If the particle size and mass concentration of the abrasive grains are below the lower limit, the expected finishing effect cannot be achieved, that is, the fine internal flow path cannot achieve the target value of surface roughness. The principle is that if the particle size is too small, the mass of the abrasive grains themselves is too low to generate sufficient kinetic energy for effective polishing and grinding. If the mass concentration is too small, the probability that the processing points on the surface are ground decreases, and effective polishing and grinding cannot be achieved. The selection of the lower limit is generally conservative. For example, it is possible to conservatively select any lower limit on the premise that it does not exceed the upper limit of the particle size. The lower limit of the ratio of the internal flow path diameter to the particle size of the abrasive grains is usually 20, that is, it is necessary to ensure that the internal flow path diameter does not become clogged when at least 20 abrasive grains pass in parallel. That is, the upper limit of the particle size of the abrasive grains is usually 1 / 20 of the internal flow path diameter, and the lower limit of the abrasive grains is generally 1 / 5 of the upper limit. The lower limit of the mass concentration of the abrasive grains is generally 10 g / L, and the selection of the lower limit is generally relatively conservative because, due to the relatively high pressure of the system, if abrasive grain clogging occurs, it may cause the waste of the workpiece and the system, or cracking and explosion. Therefore, until a significant flow resistance is generated due to the particle size of the abrasive grains being too large or the mass concentration being too high, causing a decrease in the flow velocity and flow rate, and the mutual collision between the abrasive grain particles affects the flow velocity, reducing the flow velocity, flow rate, and grinding effect, based on a predetermined lower limit, gradually increase the particle size and mass concentration of the abrasive grains. That is, the optimal value can be obtained through tests based on the lower limit.

[0041] Apply a predetermined pressure to the finishing medium so that the finishing medium flows through the fine internal flow path at a flow velocity greater than 5 m / s. The predetermined pressure here means the pressure that enables the finishing medium to flow through the inside of the fine internal flow path at a flow velocity greater than 5 m / s even in the initial state of the finishing process. As the finishing progresses, the surface roughness of the internal flow path decreases, and under the same pressure conditions, the flow velocity of the finishing medium in the fine internal flow path becomes faster and faster. It can be understood that since the realized flow velocity is within a certain range, the predetermined pressure here is a concept of range, rather than being able to apply only a specific value to the finishing medium. To measure the flow velocity of the finishing medium inside the fine internal flow path, immersion measurement cannot be adopted, otherwise, there is a risk that the abrasive grains will damage the sensor probe. The method of ultrasonic velocity measurement can be adopted, and indirect measurement can also be carried out by using the Hagen-Poiseuille's law (the following formula) of viscous fluids. In the formula, D is the internal flow path diameter, l is the length of the fine internal flow path, p is the pressure difference acting on both ends of the fine internal flow path, that is, the hydraulic pressure p, Re is the Reynolds number, um is the flow velocity of the liquid phase in the aqueous two-phase flow, ρl is the density of the liquid phase, and the flow velocity of the liquid phase is approximately equal to the flow velocity of the finishing medium.

Number

[0042] The flow velocity of the finishing medium is greater than 5 m / s and is based on the critical conditions for forming a non-Newtonian fluid theoretically and the critical value obtained by the inventor through long-term practice. According to the engineering fluid mechanics materials (for example, the book materials: Yang Shuren, Wang Zhiming, He Guangyu, etc., Engineering Fluid Mechanics [M]. Petroleum Industry Press, 2006), when the viscosity of pure water is 1 cP, it reaches the critical flow velocity of a non-Newtonian fluid greater than 16.6 m / s. However, the lower limit value of the viscosity of the liquid phase in this embodiment is 50 cP, which is greater than 1 cP, so the critical flow velocity of the non-Newtonian fluid is less than 16.6 m / s. At the same time, combining the practical results, the inventor found that an ideal processing effect cannot be obtained when it is less than 5 m / s, so the critical value is set to 5 m / s.

[0043] The flow rate at which the finishing medium flows into the interior at one end of the fine internal flow path reaches the saturation value of the flow rate that can be accommodated by the diameter of the fine internal flow path, and the hydraulic pressure inside the internal flow path is in a state where pressure accumulates, that is, in a state of so-called saturated flow rate in this field.

[0044] The saturation value of the accommodation flow rate and the state of saturated flow rate here mean that when the fluid flows into the pipe, the pipe cross-section is filled and the pipe cross-section accommodates the fluid molecules in parallel to the maximum extent.

[0045] It can be understood that the beneficial effects of the finishing method of the above embodiments are as follows.

[0046] Adopt a liquid with a viscosity of less than 1000 cP in the liquid phase of the finishing medium, increase the flow velocity in the fine internal flow path of the two-phase flow finishing medium to be greater than 5 m / s, and make the flow rate flowing into the inside at one end of the fine internal flow path reach the saturation value of the flow rate that can be accommodated by the diameter of the fine internal flow path, and make the liquid pressure inside the internal flow path in a state where pressure accumulates, forming a means for the liquid to reach the saturation flow rate with respect to the fine internal flow path. That is, through the synergistic effect of the low-viscosity liquid phase, fluid flow velocity, and saturation flow rate, the problem of difficult finishing of the fine internal flow path is solved. Describe its principle. First, due to the synergistic effect of the low-viscosity liquid phase, fluid flow velocity, and saturation flow rate, the finishing medium is in a state of low viscosity and high flow velocity, so it can smoothly enter the fine internal flow path and form a non-Newtonian fluid state inside the fine internal flow path. The fluid boundary layer is parallel to the surface of the internal flow path. The abrasive grains in the hard liquid phase like a "blade" can realize the target processing of surface convex points through shear friction, and in principle overcome the problem that only slight surface finishing can be achieved when the convex and concave points on the surface are processed simultaneously during flexible processing. At the same time, due to the micro-cutting force caused by the friction between the abrasive grains of the finishing medium and the surface of the fine internal flow path, without being limited by the material of the fine internal flow path, the optimal surface roughness that matches the average contact length range of the abrasive grain cutting edge can be obtained, breaking through the limitations of the principles of abrasive flow and water jet technology. Describe its principle. Since the cutting mechanism of abrasive flow technology lies in the volumetric force generated by the pressing of abrasive grains against the surface, when processing metals with low hardness and polymer flexible materials, dents and pits are likely to occur (Ra > 0.8 μm). The cutting force in abrasive water jet technology is the erosion force caused by the impact of abrasive grains on the surface. When processing soft metals, the surface is likely to be roughened (Ra > 0.8 μm). Also, in the low-viscosity high-flow-velocity hydrodynamic shape-adaptive (conformal) processing method, positions that do not conform to fluid engineering such as steps, sharp corners, and geometric contour curvatures on the surface of the internal flow path are more polished. Corners, sharp edges, the contour curvature of the internal flow path, and hole shapes achieve geometric streamline shaping, further improving the fluid motion performance of the internal flow path. Also, the above embodiment proposed that the critical flow velocity for realizing a hard non-Newtonian fluid like a blade by utilizing the flow velocity of the finishing medium and realizing the target processing of surface convex points through the shear friction of abrasive grains is 5 m / s.

[0047] Regarding the processing time in the fine internal flow path of the finishing medium, the finishing medium may finish the fine internal flow path within a reference period until the surface optimum roughness of the fine internal flow path reaches the target value. The reference period here may be a predetermined continuous period, or may be a plurality of intermittent periods, or after a non-predetermined continuous period after the start, when it is detected that the flow velocity and flow rate of the finishing medium reach the flow velocity and flow rate at which the surface optimum roughness of the fine internal flow path reaches the target value, the finishing process may automatically stop. For example, as described above, in some embodiments, after starting the processing, by measuring the flow velocity or flow rate of the finishing medium in the fine internal flow path, the surface optimum roughness is indirectly obtained in terms of characterization, and when the flow velocity or flow rate value reaches a predetermined value, the corresponding surface optimum roughness reaches the target value. At this time, the finishing process is stopped manually or automatically. The meaning of the surface optimum roughness reaching the target value here does not necessarily require directly measuring the surface optimum roughness, and it may be characterized indirectly. For example, as introduced above, it may be a method of characterizing the flow velocity, flow rate, etc. of the finishing medium inside the fine internal flow path. The above target value refers to the set surface optimum roughness value, generally referring to the requirement for the final surface optimum roughness of the fine internal flow path. However, it is not excluded that further finishing continues after the above finishing step. What is set at this time is not the requirement for the final surface optimum roughness.

[0048] In short, the finishing method introduced in the above embodiments constructs a hydraulic system at both ends of the internal flow path to be processed, combines means such as the use of a low-viscosity, high-speed solid-liquid two-phase fluid, reaching the saturated flow rate of the internal flow path to be processed, and the fine cutting mechanism generated by the abrasive grains in the two-phase flow rubbing the internal flow path surface at high speed, so as to solve the long-existing problem in the industry of finishing fine internal flow paths with a diameter of 3 mm or less and a length-to-diameter ratio of 50:1 or more.

[0049] Referring to what is shown in FIG. 2, in some embodiments, the present application provides a finishing device 100 including a thrust system 101, a plurality of sealed systems 102, and a plurality of transport pipeline systems 103.

[0050] Each closed system 102 includes a piston 21 and a cylinder block 18 that fits onto the piston 21 for accommodating a finishing medium 8 for performing finishing. The thrust system 101 communicates with one end of the piston 21, provides a driving force to the piston 21, and pushes the finishing medium 8 to discharge it from the outlet end of the cylinder block 18.

[0051] Each transport pipeline system 103 transports the finishing medium 8 accommodated in the corresponding closed system 102 to different ports of the internal flow path workpiece 34 where finishing is performed. For example, one group of closed systems 102 and transport pipeline systems 103 shown in FIG. 2 corresponds to the inlet of the workpiece 34, and the other group corresponds to the outlet, so that the plurality of closed systems are communicated by the workpiece 34. The upstream end of the transport pipeline system 103 is connected to the outlet end 190 of the closed system 102, and the downstream end is used to discharge the finishing medium 8 into the internal flow path workpiece 34 where finishing is performed.

[0052] The thrust system 101 may be a hydraulic system. As shown in FIG. 2, it includes a motor 1, a hydraulic working oil tank 2, a hydraulic pump 3, a pressure intensifying device 6, a vertical plunger pump 5, and an oil pipe 4. The motor 1 drives the hydraulic pump 2 to extract hydraulic working oil at a certain pressure from the oil tank 2, and the pressure oil pressurized by the pressure intensifying device 6 is transported to the vertical plunger pump 5. The vertical plunger pump 5 is connected to the piston 21 via a ball head so as to drive the piston 21 to push the finishing medium 8 to discharge it from the cylinder block 18. By adopting a hydraulic system driven by a motor, not only is the thrust large, but the accuracy is also high.

[0053] The finishing device introduced above provides a finishing medium and makes it flow under high pressure and high speed. During the finishing process, the pressure transported from the vertical plunger pump 5 to the piston 21 needs to reach 50 MPa or more and the pressure needs to be stable. For the pressure boosting device 6, the output from the vertical plunger pump 5 needs to reach 2.5 MPa to 45 MPa, and the adjustment accuracy needs to be 0.01 MPa to 0.1 MPa, the deviation of the output pressure needs to be less than 0.1%, and it is necessary to ensure that the output pressure is high and stable.

[0054] Referring to what is shown in Fig. 3, the pressure boosting device 6 includes a pressure boosting container 61, a piston 62 and a hydraulic operating oil 63. The piston 62 and the hydraulic operating oil 63 are respectively located inside the pressure boosting container 61. The piston 62 can move along the container wall of the pressure boosting container 61 so that on one side it receives a driving force and on the other side it presses the hydraulic operating oil 63 to discharge the boosted pressure from the pressure boosting device.

[0055] For example, as shown in Fig. 2, a hydraulic pump is driven by a motor to provide a driving force to the piston 62. The range of the driving force received is 1 MPa to 15 MPa. By adopting a driving configuration in which the hydraulic pump is driven by a motor, a large driving force can be provided and the accuracy is high.

[0056] Here, the pressure boosting device 6 refers to a device that boosts the fed hydraulic fluid. The piston 62 refers to a member that can reciprocate along the pressure boosting container 61.

[0057] Referring to what is shown in Fig. 3, in some embodiments, the pressure boosting container 61 includes a first straight segment 11, a second arc segment 12 and a third straight segment 13 arranged in order from upstream to downstream. Here, the upstream and downstream are based on the flow direction of the hydraulic operating oil in the pressure boosting container 61, that is, the fluid flows from upstream to downstream. Among them, the inner wall of the first straight segment 11 is such that the piston 62 moves along the wall surface to press the hydraulic operating oil 63.

[0058] The expressions of straight line segments, arc segments, straight lines, and arcs here are all for visualizing and explaining the cross-sectional structure of the pressure increasing container 61. The actual structure of the pressure increasing container 61 is a cavity structure formed by the above-mentioned straight lines and arcs rotating 360° around the axis of the pressure increasing device. For example, it is understood that when a straight line rotates 360° around the axis, a cylindrical cavity structure is formed.

[0059] The ratio of the length to the diameter of the first straight line segment 11 is greater than 5. If the length of the corresponding piston 62 is 40 mm, the length Ls1 of the first straight line segment 11 is usually greater than 120 mm. The reason is as follows. Regarding the length of the first straight line segment 11, it is necessary to consider the volume loss of the compressible fluid. Under high hydraulic pressure, when the hydraulic operating oil 63 becomes a compressible fluid, volume loss occurs. However, the long movement stroke of the piston can compensate for the volume loss of the hydraulic operating oil 63.

[0060] The second arc segment 12 is a 1 / 4 circular arc and is a concave arc. The function of the throat after contraction is to confine the fluid and increase the hydraulic force. The "concave arc" here means that this arc structure faces the inside rather than the outside of the pressure increasing container 61, that is, the center of the circle of the arc is located outside the pressure increasing container 61. The 1 / 4 circular arc refers to 1 / 4 of the circumference, that is, the corresponding central angle is 90°. Since the first straight line segment 11 and the third straight line segment 13 with different diameters are coaxial and parallel, only the 1 / 4 circular arc can smoothly connect their structures. The concave arc structure has a larger surface area, so it does not generate a high concentrated pressure on the wall surface due to the rolling force, and the forces and angle changes received by the mass elements of the fluid also become stable and consistent with a long movement stroke. Another function of a part of the arc is to realize the guiding function for the hydraulic operating oil and make the fluid flow in a laminar motion to the throat at a low speed. Also, the concave circular arc provides a pressing force to the fluid, contributing to the pressing and densification of the fluid and raising a larger and more stable hydraulic force.

[0061] The third linear segment 13 is the final movement stroke after the hydraulic operating oil is pressurized. The downstream end of the third linear segment 13 is the discharge end of the pressure increasing container 61. The ratio of the cross-sectional area S1 of the first linear segment 11 to the cross-sectional area S3 of the third linear segment 13 is 2.5 to 3, that is, the pressure increasing ratio is 2.5 to 3. The length Ls3 of the third linear segment 13 is usually less than 50 mm. The inventor believes that if the movement stroke of the hydraulic operating oil in the third linear segment 13 is too long, it will cause turbulent flow due to the increase of the boundary layer, and finally the hydraulic force output will become unstable. By making the length of the third linear segment 13 shorter, the fluid stroke becomes shorter, which is beneficial to the laminar flow state of the fluid. The flow velocity of the discharged hydraulic operating oil is stable, and the accuracy of the final hydraulic pressure adjustment is improved. In addition, when the ratio of the cross-sectional areas of the first linear segment 11 and the third linear segment 13 is 2.5 to 3, the maximum pressure increasing thrust can be provided, which is discovered by the inventor in practice. The following can be understood. According to the thrust calculation formula: F = πR2×p, if the radius value R corresponding to the diameter of the third linear segment is too small, the acceleration effect of the hydraulic operating oil is good, and the pressure p after pressurization becomes large, but the flow rate is insufficient and the thrust is insufficient. On the contrary, if the radius R of the port is too large, the flow rate becomes large, but the acceleration effect of the hydraulic operating oil is not good, and even if the pressure p after pressurization is too small, the thrust is insufficient. In practice, the optimal thrust is not as simple as the thrust calculation formula and is a complex problem affected by various factors. The inventor discovered that there is an optimal range of 2.5 to 3 for the proportionality of the diameters of the first linear segment 11 and the third linear segment 13, at which the corresponding thrust is maximized.

[0062] The beneficial effects when adopting the above embodiments are as follows. The pressure increasing container adopts the configuration of the first linear segment, the second arc segment which is a 1 / 4 arc and a concave arc, and the third linear segment. Due to the synergistic effect of the three, after the hydraulic operating oil passes through the pressure increasing device, a large and stable pressure is output.

[0063] In some embodiments, the ratio of the length Ls1 of the first straight segment 11, the radius rs of the second arc segment 12, and the length Ls3 of the third straight segment 13 is 11:5:4. By adopting this ratio, the hydraulic working oil can maintain pressure stability, and the flow of the hydraulic working oil in each segment is less likely to generate turbulent flow. Furthermore, during the process of converging and contracting, the forces and directions received by each mass element of the hydraulic working oil are stably converged and consistent. It is understood that the above ratio of 11:5:4 is not strictly restricted and is acceptable within a certain error range, for example, within an error range of 5%.

[0064] In some embodiments, the chamfer radius Rs at the connection between the first straight segment 11 and the second arc segment 12 is set to be 0.1 mm to 0.5 mm. Since the second arc segment 12 is a concave arc and a quarter circle arc, the second arc segment 12 is in contact with and connected to the third straight segment 13, so there is no need to chamfer the connection. Chamfering can remove the stress concentration generated at the step / sharp edge during the process of fluid movement at the connection, and avoid the fluid from being disturbed and turbulent flow being formed due to the step / sharp edge.

[0065] In some embodiments, the material of the pressure increasing container 61 is steel. For example, 45# steel, which is commonly used, may be sufficient. This can reduce the cost of the material of the pressure increasing container 61 and make processing easier.

[0066] The inner wall of the pressure increasing container 61 has a roughness Ra of 0.1 μm to 0.4 μm, a roundness of 100 μm or less, and a cylindricity of 200 μm or less. This can ensure the stability of the flow state of the hydraulic working oil, avoid the generation of partial turbulent flow and cavitation due to poor surface quality, and improve the stability of the increased thrust. The above size parameters may also be realized by the honing process.

[0067] As described above, by combining the pressure boosting device 6 introduced above with the motor and hydraulic pump at its front end, the thrust of the piston 62 of the pressure boosting device 6 is provided. Also, by combining it with the vertical plunger pump at its rear end, that is, the hydraulic operating oil boosted from the pressure boosting device 6 is discharged, the configured thrust system satisfies that the pressure on the sealed system 102 of the finishing device is greater than 50 MPa, and the adjustment accuracy is 0.01 MPa to 0.1 MPa, and the pressure deviation is less than 0.1%. This ensures that the finishing medium can stably perform finishing processing on the workpiece with an internal flow path in a high-speed and high-pressure state.

[0068] As described above, the present application provides a method for boosting the pressure of hydraulic operating oil, and the hydraulic operating oil is pushed so as to be discharged through the first straight segment 11, the second arc segment 12, and the third straight segment 13 in sequence. Among them, the ratio of the length to the diameter of the first straight segment 11 is greater than 5, the second arc segment 12 is a 1 / 4 circular arc and is a concave arc, and the ratio of the length to the diameter of the third straight segment 13 is less than 3. The first straight segment 11 and the third straight segment 13 are coaxial and parallel, and the ratio of the cross-sectional areas of the first straight segment 11 and the third straight segment 13 is 2.5 to 3. Thereby, the pressure of the hydraulic operating oil can be stably and reliably boosted, and the output pressure is large and stable.

[0069] The present invention is disclosed in the embodiments as described above, but it is not intended to limit the present invention by the embodiments. Those skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the content that does not deviate from the technical solution of the present invention and any modifications, equivalent changes, and decorations made to the above embodiments based on the technical essence of the present invention fall within the protection scope defined by the claims of the present invention.

Claims

1. A pressure increasing container used in a pressure increasing device, which is arranged in order from upstream to downstream, a first straight segment with a ratio of length to diameter greater than 5, a second arc segment which is a 1 / 4 arc and is a concave arc, and a third straight segment with a ratio of length to diameter less than 3, and is provided with the first straight segment and the third straight segment are coaxial and parallel, the downstream end of the third straight segment is the discharge end of the pressure increasing container, and the ratio of the cross-sectional area of the first straight segment to the third straight segment is 2.5 to 3. A pressure increasing container characterized by this.

2. The pressure increasing container according to claim 1, characterized in that the ratio of the length of the first straight segment, the radius of the second arc segment, and the length of the third straight segment is 11:5:

4.

3. The pressure increasing container according to claim 1, characterized in that the chamfer radius at the connection position between the first straight segment and the second arc segment is 0.1 mm to 0.5 mm.

4. The pressure increasing container according to claim 1, characterized in that the material of the pressure increasing container is steel.

5. The pressure increasing container according to claim 4, characterized in that the material of the pressure increasing container is 45# steel.

6. The pressure increasing container according to claim 4, characterized in that the inner wall of the pressure increasing container has a roughness Ra of 0.1 μm to 0.4 μm, a roundness of 100 μm or less, and a cylindricity of 200 μm or less.

7. A pressure increasing device comprising the pressure increasing container according to any one of claims 1 to 6, the pressure increasing container has hydraulic operating oil inside, the piston is provided in the pressure increasing container and is used to receive a driving force on one side, and the piston moves along the container wall of the first straight segment so as to push the hydraulic operating oil on the other side of the piston and discharge it from the downstream end of the third straight segment.

8. The pressure increasing device according to claim 7, characterized in that the driving force received by the piston is 1 MPa to 15 MPa, and the output pressure is 2.5 MPa to 45 MPa.

9. A thrust system, a sealing system for accommodating a finishing medium for performing finishing, and a transport pipeline system connected to the sealing system, and is provided with the thrust system can push the finishing medium accommodated in the sealing system by applying a thrust to the sealing system, so that the finishing medium passes through the transport pipeline system and is sent to the workpiece to be finished. The thrust system includes a hydraulic pump and a pressure boosting device according to claim 7 or 8. The hydraulic pump provides the driving force to the piston of the pressure boosting device, and the hydraulic working oil is boosted by the pressure boosting device and discharged. A finishing device is characterized by this.

10. The thrust system further includes a motor and a vertical plunger pump. The hydraulic pump driven by the motor pushes the piston, and the hydraulic working oil is boosted by the pressure boosting device and discharged to the vertical plunger pump. The vertical plunger pump is connected to the closed system and applies pressure to the finishing medium contained in the closed system. The finishing device according to claim 9 is characterized by this.

11. The pressure provided to the closed system by the thrust system is greater than 50 MPa, the adjustment accuracy is 0.01 MPa to 0.1 MPa, and the deviation of the output pressure is less than 0.1%. The finishing device according to claim 10 is characterized by this.

12. Including pushing the hydraulic working oil so that the hydraulic working oil is boosted and discharged through a first straight segment, a second arc segment, and a third straight segment in sequence. The ratio of the length to the diameter of the first straight segment is greater than 5, the second arc segment is a 1 / 4 circular arc and is a concave arc, and the ratio of the length to the diameter of the third straight segment is less than 3. The first straight segment and the third straight segment are coaxially parallel, and the ratio of the cross-sectional areas of the first straight segment and the third straight segment is 2.5 to 3. A method for boosting the pressure of hydraulic working oil is characterized by this.

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