A hydraulic seal and lubrication structure for a low-viscosity liquid plunger pump

Abstract

A hydraulic sealing and lubrication structure for a low-viscosity liquid plunger pump includes a pump body, a plunger, a pump chamber, a free piston, a piston chamber, a sealing liquid chamber, a pump sub-chamber, a liquid inlet check valve, a liquid outlet check valve, a sealing liquid inlet channel, and an annular sealing liquid groove, wherein the piston chamber is arranged in the plunger, and the free piston is installed in the piston chamber. The free piston divides the piston chamber into a pump sub-chamber at one end of the free piston and a sealing liquid chamber at the other end of the free piston, the pump sub-chamber is connected to the pump chamber, and the sealing liquid chamber is connected to the annular sealing liquid groove; the free piston maintains a dynamic balance between the sealing liquid pressure in the annular sealing liquid groove and the liquid pressure in the pump chamber. The sealing of the plunger pump when pumping ultra-high-pressure low-viscosity liquid is achieved; the lubrication of the plunger is ensured; the direct contact between the plunger and the working cylinder channel is avoided; the problem of plunger wear when the pressure of pumping low-viscosity liquid reaches more than 250MPa is solved, and the working reliability of the plunger pump is effectively improved.

Description

Technical Field

[0001] The invention relates to a low-viscosity liquid plunger pump, in particular to a hydraulic seal and lubrication structure of a low-viscosity plunger pump, belonging to the technical field of plunger pumps. Background Art

[0002] The plunger pump has the advantages of high rated pressure, compact structure and high efficiency. It is widely used in equipment that outputs high-pressure liquids, such as ultra-high-pressure water jet cutting, ultra-high-pressure water jet rust removal, high-pressure water jet cleaning, and diesel engine high-pressure fuel pumps.

[0003] The diesel pumped by the diesel engine's high-pressure plunger pump has a high viscosity. When the plunger pump is pumping oil, the tiny gap between the plunger and the inner wall of the plunger hole has a throttling effect (i.e., resistance along the way) on the leaked diesel, maintaining the oil pressure in the plunger pump chamber. At the same time, the leaked diesel has a high viscosity, which has a good lubricating effect on the plunger, so the plunger oil pump generally uses gap sealing.

[0004] When the plunger pump pumps low-viscosity liquids such as water, methanol, gasoline, etc., if the gap sealing method is used, not only will there be a large leakage and difficulty in establishing a high pumping pressure, but also because the viscosity of the leaked liquid is low, the plunger will not be well lubricated and will quickly wear out and fail. Plunger pumps that pump low-viscosity liquids at home and abroad all use mechanical packing seals; the disadvantage of mechanical packing seals is that the sliding friction between the packing and the plunger surface causes heat and wear, which not only limits the pump speed, but also reduces the working reliability and durability. The seal life of a low-viscosity liquid plunger pump with a working pressure of more than 200MPa is only about 200 hours, and the life of the packing seal is shorter as the working pressure increases. In order to increase the working pressure of a low-viscosity liquid high-pressure plunger pump and extend its service life, it is necessary to solve the sealing and lubrication problems of the low-viscosity liquid high-pressure plunger pump.

[0005] In order to solve the problem that the plunger and working cylinder bore of the high-pressure plunger pump wear and fail to meet the use requirements when the diesel engine uses low-viscosity methanol fuel, the inventor has continued to study the sealing and lubrication of the plunger pump plunger, from the 2006 patent "Multi-Fuel Diesel Engine Injection Pump" (ZL200620127615.1) to the 2019 "A Sealing and Lubrication Structure of a Low-Viscosity Liquid Plunger Pump" (ZL201920084275.6), after many trial productions and tests, there are problems such as complex processing technology, difficult to ensure processing accuracy, and cumbersome pipeline sealing to varying degrees. Summary of the invention

[0006] The purpose of the present invention is to provide a hydraulic seal and lubrication structure for a low-viscosity liquid plunger pump which has a simpler structure, is easier to manufacture (easy to ensure processing accuracy and low manufacturing cost), can pump low-viscosity liquids such as methanol and water at a pressure of more than 250 MPa, has good working reliability and a long plunger working life; the structure can be used for internal combustion engines to pump a variety of fuels, and can also be widely used in high-pressure plunger pumps for ultra-high-pressure water jet cutting, ultra-high-pressure pure water jet rust removal, high-pressure water jet cleaning, seawater pumps, chemical pumps and other equipment, or other reciprocating plunger pair high-pressure sealing and lubrication devices.

[0007] In order to achieve the above-mentioned purpose of the present invention, the inventor further innovated the patent "A sealing and lubricating structure of a low-viscosity liquid plunger pump" (ZL201920084275.6) by "omission of elements" and "change of element relationship", and proposed the invention "A hydraulic sealing and lubricating structure of a low-viscosity liquid plunger pump". This application adopts the following technical solutions:

[0008] A hydraulic sealing and lubrication structure for a low-viscosity liquid plunger pump, comprising a plunger (1), a piston chamber (1.1), a pump body (2), a working cylinder channel (3), a pump chamber (3.1), a free piston (4), a sealing liquid chamber (4.1), a pump sub-chamber (4.2), a piston channel (4.3), an annular sealing liquid groove (6), a sealing liquid inlet channel (8), a liquid inlet check valve (11), and a liquid outlet check valve (13); the working cylinder channel (3) is arranged in the pump body (2); the plunger (1) is installed in the working cylinder channel (3) and is in contact with the working cylinder channel The sealing liquid inlet channel (8) is arranged on the pump body (2), and the liquid inlet check valve (11) and the liquid outlet check valve (13) are communicated with the pump chamber (3.1); a piston chamber (1.1) and a piston channel (4.3) are arranged in the plunger (1); the free piston (4) and the piston channel (4.3) are precisely slidably matched, and the free piston (4) divides the piston chamber (1.1) into a pump sub-chamber (4.2) communicated with the pump chamber (3.1) and a sealing liquid chamber (4.1) communicated with the annular sealing liquid groove (6).

[0009] An annular sealing liquid groove (6) provided on the outer cylinder of the plunger (1) separates the annular micro-gap between the plunger (1) and the working cylinder channel (3) into: an upper plunger annular micro-gap (9) extending upward from the annular sealing liquid groove (6) to the pump chamber (3.1), and a lower plunger annular micro-gap (10) extending downward from the annular sealing liquid groove (6) to the lower end of the working cylinder channel (3).

[0010] When the plunger (1) pumps liquid upward, the high-pressure liquid pressure in the pump chamber (3.1) is transmitted to the annular sealing liquid groove (6) through the pump sub-chamber (4.2), the free piston (4) and the sealing liquid chamber (4.1), thereby maintaining the sealing liquid pressure P of the annular sealing liquid groove (6) at the lower end of the annular micro-gap (9) of the upper plunger. R1The liquid pressure P in the pump chamber (3.1) K1 Equal, that is, P R1 =P K1 , effectively preventing the high-pressure liquid from entering the annular micro-gap (9) of the upper plunger during the pumping process and causing the leakage of low-viscosity liquid; the viscosity of the sealing liquid in the annular sealing liquid groove (6) increases with the increase of pressure. Due to the throttling effect of the annular micro-gap (10) of the lower plunger on the high-viscosity sealing liquid, only a small amount of sealing liquid flows back from the annular sealing liquid groove (6) through the annular micro-gap (10) of the lower plunger to the sealing liquid tank. The annular sealing liquid film formed in the annular micro-gap (10) of the lower plunger prevents the direct contact between the plunger (1) and the wall surface of the working cylinder channel (3), and plays a lubricating role on the outer surface of the plunger (1). At the same time, the pressure of the pump chamber (3.1) increases, the free piston (4) moves downward, and the sealing liquid in the sealing liquid chamber (4.1) enters the annular sealing liquid groove (6) to replenish the sealing liquid leaking from the annular micro-gap (10) of the lower plunger.

[0011] During the upward pumping process of the plunger (1), the pressure at the upper and lower ends of the upper plunger annular micro-gap (9) is dynamically balanced, effectively preventing the ultra-high pressure liquid in the pump chamber (3.1) from entering the upper plunger annular micro-gap (9), thereby achieving sealing of the ultra-high pressure low viscosity liquid in the pump chamber (3.1). This ensures that the plunger pump generates an ultra-high pressure liquid pressure of more than 250 MPa; the high viscosity sealing liquid film in the lower plunger annular micro-gap (10) suspends the plunger (1) in the working cylinder channel (3), avoiding contact between the outer surface of the plunger (1) and the mating surface of the working cylinder channel (3), achieving lubrication of the plunger (1), and ensuring the working reliability of the plunger (1).

[0012] Similarly, when the plunger moves downward to absorb liquid, before reaching the bottom dead center, the pressure P in the annular sealing liquid groove (6) at the lower end of the annular micro-gap (9) of the upper plunger is R1 The liquid pressure P in the upper pump chamber (3.1) K1 Equal, that is, P R1 =P K1 , preventing the liquid in the pump chamber (3.1) and the annular sealing liquid groove (6) from entering the annular micro-gap (9) of the upper plunger, thereby achieving sealing of the high-pressure liquid.

[0013] When the plunger (1) moves downward to the lower dead point, the sealing liquid inlet channel (8) is connected to the annular sealing liquid groove (6), and the sealing liquid enters the annular sealing liquid groove (6) and the sealing liquid chamber (4.1) through the sealing liquid inlet channel (8), completing the replenishment of the sealing liquid. At this time, the sealing liquid pressure P in the annular sealing liquid groove (6) is R2 Less than or equal to the sealing liquid input pump end pressure P S0 , P R2 ≤P S0At the same time, when the plunger (1) moves downward, the pressure from the working fluid delivery pump is P F0 (Assume P F0 ≤P S0 ) of the working fluid, opens the inlet check valve (11) and flows into the pump chamber (3.1). The liquid pressure P in the pump chamber (3.1) K2 , P F0 ≥P K2 ≥0bar;

[0014] The pressure P in the annular sealing liquid groove (6) at the lower end of the annular micro-gap (9) of the upper plunger is R2 The liquid pressure P in the upper pump chamber (3.1) K2 The pressure difference is: P S0 ≥|P R2 -P K2 ∣≥0. Experiments have shown that when the pressure difference of the liquid at both ends of the annular micro-gap is less than 10 bar, there is no liquid flow in the annular micro-gap, which can ensure the sealing of the plunger (1) during the downward liquid suction process.

[0015] The downward movement of the plunger (1) is a round trip of the upward pumping distance of the plunger (1). The high-viscosity sealing liquid formed in the annular micro-gap (10) of the lower plunger during the upward pumping process of the plunger (1) adheres to the sealing liquid film formed on the surface of the working cylinder channel (3), providing good lubrication for the downward movement of the plunger (1).

[0016] Beneficial effects of the present invention:

[0017] 1. The inventor further innovated the patent entitled "A Sealing and Lubricating Structure of a Low-Viscosity Liquid Plunger Pump" (ZL201920084275.6) by "omitting elements" and "changing the relationship between elements": the "free piston (4)" originally arranged in the pressure transmission cylinder channel (5) was arranged in the piston chamber (1.1), and the invention "A Hydraulic Sealing and Lubricating Structure of a Low-Viscosity Liquid Plunger Pump" was invented, which reduced the oil channel (6.1), the plug (17), and the plug (18), reduced the high-pressure leakage link, and made the structure simpler and easier to manufacture; all the original functions of the inventor's original utility model entitled "A Sealing and Lubricating Structure of a Low-Viscosity Liquid Plunger Pump" (ZL201920084275.6) were still maintained:

[0018] <1> No fuel or water leakage is achieved, and the pressure of low-viscosity liquids such as methanol or water can reach more than 250MPa;

[0019] <2> The seal between the plunger (1) and the working cylinder hole (3) is effectively achieved, while direct contact between the plunger (1) and the working cylinder hole (3) is avoided, the wear problem between the plunger (1) and the working cylinder hole (3) is overcome, and the reliability of the plunger pump is effectively improved;

[0020] <3> The structure is simpler and the manufacturing cost is greatly reduced.

[0021] 2. The present invention "A hydraulic seal and lubrication structure for a low-viscosity liquid plunger pump" can be used for various fuel pumps of internal combustion engines to pump low-viscosity fuels such as gasoline, methanol, ethanol, etc., and can be used for ultra-high-pressure water cutting, ultra-high-pressure pure water jet rust removal, high-pressure water jet cleaning, seawater pumps, chemical pumps and other equipment's high-pressure plunger pumps, reciprocating pair high-pressure seals and lubrication structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of the hydraulic seal and lubrication structure of the low-viscosity liquid plunger pump of the present invention;

[0023] Figure 2 A schematic diagram of the structure of the hydraulic seal and lubrication structure of the low-viscosity liquid plunger pump of the present invention when the plunger is pumping liquid upward;

[0024] Figure 3 A schematic diagram of the structure of the hydraulic seal and lubrication structure of the low-viscosity liquid plunger pump of the present invention when the plunger moves downward to absorb the liquid;

[0025] The markings in the figure are as follows: 1 plunger; 1.1 piston chamber; 2 pump body; 3 working cylinder channel; 3.1 pump chamber; 4 free piston; 4.1 sealing liquid chamber; 4.2 pump sub-chamber; 4.3 piston channel; 6 annular sealing liquid groove; 8 sealing liquid inlet channel; 9 upper plunger annular micro-gap; 10 lower plunger annular micro-gap; 11 liquid inlet check valve; 12 liquid inlet pipe interface; 13 liquid outlet check valve; 14 high-pressure liquid outlet pipe interface. DETAILED DESCRIPTION

[0026] The specific implementation modes of the present invention will be further described below in conjunction with the accompanying drawings.

[0027] As attached Figure 1The hydraulic sealing and lubrication structure of a low-viscosity liquid plunger pump of the present invention comprises a plunger (1), a piston chamber (1.1), a pump body (2), a working cylinder channel (3), a pump chamber (3.1), a free piston (4), a sealing liquid chamber (4.1), a pump sub-chamber (4.2), a piston channel (4.3), an annular sealing liquid groove (6), a sealing liquid inlet channel (8), a liquid inlet check valve (11), and a liquid outlet check valve (13), wherein the working cylinder channel (3) is arranged in the pump body (2); the plunger (1) is installed in the working cylinder channel (3); The cylinder bore (3) and the working cylinder bore (3) are precisely slidably matched, and the annular clearance of the sliding match is 0.0015 to 0.0025 mm; the sealing liquid inlet channel (8) is arranged on the pump body (2) and is connected to the annular sealing liquid groove (6) when the plunger (1) is at the bottom dead center position; the free piston (4) is installed in the piston chamber (1.1), and the free piston (4) and the piston bore (4.3) are precisely slidably matched, and the annular micro clearance of the sliding match is 0.0015 to 0.0025 mm; as shown in the attached Figure 1 As shown, the inlet check valve (11) and the outlet check valve (13) are arranged on the pump body (2) and are both connected to the pump chamber (3.1); the free piston (4) is installed in the piston chamber (1.1), and the piston chamber (1.1) is divided into a pump sub-chamber (4.2) at one end of the free piston (4) and a sealing liquid chamber (4.1) at the other end of the free piston (4); the sealing liquid chamber (4.1) is connected to the annular sealing liquid groove (6), and the pump sub-chamber (4.2) is connected to the pump chamber (3.1); as shown in the attached Figure 1 , Attachment Figure 2 , Attachment Figure 3 As shown, an annular sealing liquid groove (6) provided on the plunger (1) separates the annular micro-gap between the plunger (1) and the working cylinder channel (3) into: an upper plunger annular micro-gap (9) extending upward from the annular sealing liquid groove (6) to the pump chamber (3.1), and a lower plunger annular micro-gap (10) extending downward from the annular sealing liquid groove (6) to the lower end of the working cylinder channel (3).

[0028] The process of the plunger (1) pumping liquid upward:

[0029] As attached Figure 2 As shown, the plunger (1) moves from the lower dead point to the upper dead point, the liquid inlet check valve (11) closes, the volume of the pump chamber (3.1) decreases, and the pressure increases. When the pressure of the pump chamber (3.1) reaches the opening pressure of the liquid outlet check valve (13), the high-pressure liquid opens the liquid outlet check valve (13) and enters the high-pressure liquid pipeline through the high-pressure liquid pipe interface (14); when the plunger (1) moves upward to the upper dead point, the liquid outlet check valve (13) closes, and the liquid pumping process ends.

[0030] 1> Plunger seal in pumping process

[0031] When the plunger (1) is at the bottom dead center, the annular sealing liquid groove (6) is connected to the sealing liquid inlet channel (8), the sealing liquid enters the sealing liquid chamber (4.1) through the sealing liquid inlet channel (8) and the annular sealing liquid groove (6), the free piston (4) moves upward, and the sealing liquid chamber (4.1) is filled with sealing liquid; as the plunger (1) moves upward, the liquid pressure in the pump chamber (3.1) increases, and the pressure of the pump chamber (3.1) is transmitted to the annular sealing liquid groove (6) through the pump sub-chamber (4.2), the free piston (4), and the sealing liquid chamber (4.1), so as to maintain the pressure P in the annular sealing liquid groove (6) at the lower end of the annular micro-gap (9) of the upper plunger. R1 The liquid pressure P in the upper pump chamber (3.1) K1 Equal, that is, P R1 =P K1 Therefore, during the upward pumping process of the plunger (1), the high-pressure liquid in the pump chamber (3.1) is effectively prevented from entering the upper plunger annular micro-gap (9), thereby achieving sealing of the high-pressure liquid; the pressure balance between the pump chamber (3.1) and the annular sealing liquid groove (6) at the upper and lower ends of the upper plunger annular micro-gap (9) achieves sealing of the ultra-high-pressure low-viscosity liquid in the pump chamber (3.1), overcomes the problem of ultra-high-pressure liquid leakage, and ensures that the pressure of the low-viscosity liquid pumped by the plunger pump reaches more than 250 MPa.

[0032] 2> Plunger lubrication during pumping

[0033] The viscosity of the sealing liquid in the annular sealing liquid groove (6) increases with the increase of pressure. Due to the throttling effect of the annular micro-gap (10) of the lower plunger on the high-viscosity lubricating oil, only a small amount of sealing liquid leaks out from the annular sealing liquid groove (6) through the annular micro-gap (10) of the lower plunger and flows back to the sealing liquid tank. At the same time, the high-pressure liquid in the pump chamber (3.1) pushes the free piston (4) downward through the pressure of the pump sub-chamber (4.2), and the sealing liquid in the sealing liquid chamber (4.1) enters the annular sealing liquid groove (6) to supplement the sealing liquid leaked from the annular micro-gap (10) of the lower plunger.

[0034] The high-viscosity sealing liquid in the annular micro-gap (10) of the lower plunger suspends the plunger (1) in the working cylinder channel (3), thereby avoiding direct contact between the surface of the plunger (1) and the matching surface of the working cylinder channel (3), achieving lubrication of the plunger (1), and ensuring the working reliability and durability of the plunger (1).

[0035] The process of the plunger (1) moving downward to absorb liquid:

[0036] As attached Figure 3 As shown in the figure, the plunger (1) moves from the top dead center to the bottom dead center, the volume of the pump chamber (3.1) increases, the pressure decreases, and the liquid outlet check valve (13) closes; when the pumping pressure P of the working fluid delivery pump is F0When the pressure is 2 bar, the 2 bar working fluid enters the pump chamber (3.1) through the liquid inlet pipe interface (12) and opens the liquid inlet check valve (11). During the downward suction process, the liquid pressure P in the pump chamber (3.1) is K2 , 2bar≥P K2 ≥0bar; when the plunger (1) moves downward to the lower dead point, the liquid inlet check valve (11) closes, and the downward liquid suction process of the plunger (1) ends.

[0037] 3> Plunger seal during aspiration

[0038] The same principle as the upward pump liquid seal, the plunger (1) moves downward to absorb liquid. Before reaching the bottom dead center, the pressure P in the annular sealing liquid groove (6) at the lower end of the upper plunger annular micro-gap (9) is R1 The liquid pressure P in the upper pump chamber (3.1) K1 Equal, that is, P R1 =P K1 , preventing the liquid in the pump chamber (3.1) and the annular sealing liquid groove (6) from entering the annular micro-gap (9) of the upper plunger, thereby achieving sealing of the high-pressure liquid.

[0039] When the plunger (1) moves downward to the lower dead point, the sealing liquid inlet passage (8) is connected to the annular sealing liquid groove (6), and the low-pressure sealing liquid with a pressure of 4 bar in the sealing liquid external pipeline enters the annular sealing liquid groove (6) and the sealing liquid chamber (4.1) through the sealing liquid inlet passage (8), thereby completing the replenishment of the sealing liquid. At this time, the sealing liquid pressure P in the annular sealing liquid groove (6) is R2 ≤4bar; Pressure P in the annular sealing liquid groove (6) at the lower end of the annular micro-gap (9) of the upper plunger R2 (P R2 ≤4bar) and the liquid pressure P in the upper pump chamber (3.1) K2 (2bar≥P K2 ≥0bar) the pressure difference is less than 4bar. Experiments have shown that when the pressure difference of the liquid at both ends of the annular micro-gap is less than 10bar, there is no liquid flow in the annular micro-gap, and the leakage of the pumped liquid is effectively prevented during the process of the plunger (1) descending to absorb the working fluid.

[0040] 4> Plunger lubrication during the aspiration process

[0041] During the upward pumping process of the plunger (1), the high-viscosity sealing liquid in the annular micro-gap (10) of the lower plunger adheres to the surface of the working cylinder channel (3) to form a sealing liquid film, which provides good lubrication for the downward movement of the plunger (1).

[0042] From the sealing and lubrication of the pumping and suction processes, it can be seen that the hydraulic sealing and lubrication structure of the low-viscosity liquid plunger pump can prevent the low-viscosity liquid in the pump chamber (3.1) from entering the upper plunger annular micro-gap (9) during the upward pumping and downward suction processes of the plunger (1), thereby achieving a hydraulic sealing and lubrication structure of the plunger pump that can pump low-viscosity liquid at a pressure of more than 250 MPa without leakage of the low-viscosity liquid; the sealing liquid film in the lower plunger annular micro-gap (10) allows the plunger (1) to float in the working cylinder channel (3), thereby avoiding direct contact between the plunger (1) and the working cylinder channel (3), overcoming the wear and failure problem of the plunger (1) and the working cylinder channel (3), completing the lubrication between the plunger (1) and the working cylinder channel (3), and improving the working reliability and durability.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A hydraulic sealing and lubrication structure for a low-viscosity liquid plunger pump, comprising a plunger (1), a piston chamber (1.1), a pump body (2), a working cylinder channel (3), a pump chamber (3.1), a free piston (4), a sealing liquid chamber (4.1), a pump sub-chamber (4.2), an annular sealing liquid groove (6), a sealing liquid inlet channel (8), a liquid inlet check valve (11) and a liquid outlet check valve (13), wherein: The working cylinder channel (3) is arranged in the pump body (2), the plunger (1) is installed in the working cylinder channel (3), the plunger (1) and the working cylinder channel (3) are precisely slidably matched, the sealing liquid inlet channel (8) is arranged on the pump body (2), and is communicated with the annular sealing liquid groove (6) when the plunger (1) is at the bottom dead center position, the liquid inlet check valve (11) and the liquid outlet check valve (13) are arranged on the pump body (2), and are both communicated with the pump chamber (3.1); a piston chamber (1.1) is arranged in the plunger (1), and a free piston (4) is installed in the piston chamber (1.1), and the free piston (4) divides the piston chamber (1.1) into a pump sub-chamber (4.2) at one end of the free piston (4) and a sealing liquid chamber (4.1) at the other end of the free piston (4), the pump sub-chamber (4.2) is in communication with the pump chamber (3.1), and the sealing liquid chamber (4.1) is in communication with the annular sealing liquid groove (6); the annular sealing liquid groove (6) provided on the plunger (1) separates the annular micro-gap between the plunger (1) and the working cylinder channel (3) into: an upper plunger annular micro-gap (9) extending from the annular sealing liquid groove (6) upward to the pump chamber (3.1), and a lower plunger annular micro-gap (10) extending from the annular sealing liquid groove (6) downward to the lower end of the working cylinder channel (3).

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