Zero friction hydraulic cylinder

Abstract

The present application relates to the technical field of hydraulic cylinders, and in particular to a zero-friction hydraulic cylinder, comprising a cylinder barrel, a cylinder bottom, a plunger inserted in the cylinder barrel and forming an annular gap between the inner wall of the cylinder barrel; a sealing ring embedded on the inner wall of the cylinder barrel, and the sealing ring and the plunger can float relatively; at least two groups of static pressure bearings are arranged in the cylinder barrel; an oil inlet A for injecting oil between the cylinder bottom and the plunger is arranged on the cylinder bottom, an oil hole B is arranged on the side wall of the cylinder barrel, and the oil pressure P at the oil hole B is B The oil pressure in the annular gap acts on the sealing ring. An oil injection hole C is provided on the side wall of the cylinder. The oil injection hole C is located on the side of the oil hole B away from the oil inlet A. The oil pressure P C Less than the oil pressure P acting on the plunger at the oil inlet A A The present application supports the plunger through a hydrostatic bearing, and the pressure oil P C and P B The pressure drop, clearance and eccentricity of the annular gap are controlled collaboratively to replace the traditional sealing ring and achieve zero friction of the plunger.

Description

Technical Field

[0001] The present application relates to the technical field of hydraulic cylinders, and in particular to a zero-friction hydraulic cylinder. Background Art

[0002] In the hydraulic cylinders in the existing hydraulic technology, a sealing ring is generally used to seal between the inner wall of the cylinder body and the outer cylindrical surface of the piston, and a sealing ring is used to seal between the cylinder head hole wall and the outer surface of the piston rod. This hydraulic cylinder mainly relies on the elasticity of the material and adopts the method of reserving material to implement non-pressure sealing. The degree of sealing is affected by the following conditions: first, the size of the reserved material amount; second, the elasticity of the material is affected by the erosion of the flowing medium and aging over time; third, the tolerance and shape and position tolerance deformation of the inner wall of the cylinder body, etc. In addition, the leakage problem of the flowing medium has not been well solved.

[0003] In the prior art, the reciprocating motion of the piston is guided by the lining material on the piston surface and the bushing in the cylinder head hole wall, which will inevitably cause friction, energy consumption, wear, piston rod shaking or swaying and other inevitable disadvantages. Summary of the invention

[0004] The present invention aims to solve one of the problems existing in the background technology.

[0005] To this end, the present invention provides a zero-friction hydraulic cylinder.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] A zero-friction hydraulic cylinder, comprising:

[0008] A cylinder barrel, the bottom of which is connected to a cylinder bottom;

[0009] A plunger, the plunger is inserted into the cylinder and forms an annular gap with the inner wall of the cylinder;

[0010] A sealing ring, wherein the sealing ring is embedded in the inner wall of the cylinder barrel and can float relative to the plunger;

[0011] An oil inlet hole and an oil drain hole are arranged on the side wall of the cylinder, an oil pad is arranged in the cylinder, and the oil inlet hole, the oil drain hole and the oil pad form at least two groups of static pressure bearings for supporting the plunger to float in the cylinder; an oil inlet A for injecting oil between the cylinder bottom and the plunger is arranged on the cylinder bottom, an oil hole B for acting on the sealing ring to resist the oil pressure in the annular gap is arranged on the side wall of the cylinder, and an oil injection hole C is arranged on the side of the oil hole B away from the oil inlet A, and the oil pressure P of the oil injection hole C is C Less than the oil pressure P acting on the plunger at the oil inlet A A .

[0012] Furthermore, the oil filling hole C is arranged close to the sealing ring.

[0013] Furthermore, a plurality of oil inlet holes are arranged along the circumference of the cylinder.

[0014] Furthermore, a sealing groove is provided on the inner wall of one end of the bottom of the cylinder barrel near the bottom of the cylinder, the sealing groove is arranged in an annular shape, the sealing ring is floatingly arranged in the sealing groove, and the sealing ring is arranged on one side close to the axis of the cylinder barrel, and an adjusting oil chamber connected to the oil hole B is formed between the sealing ring and the bottom of the sealing groove and the bottom of the cylinder barrel.

[0015] Furthermore, a working oil chamber is formed between the cylinder bottom and the plunger, and an oil channel is provided on the cylinder bottom, and the oil channel connects the working oil chamber and the oil inlet A.

[0016] Furthermore, one end of the oil passage communicating with the working oil chamber is opposite to the axis of the cylinder barrel.

[0017] Furthermore, the distance between the oil filling hole C and the bottom surface of the plunger is l, and the single-side gap of the annular gap formed between the plunger and the sealing ring is h. h0 is the initial clearance after dimension processing and assembly when there is no pressure in the hydraulic cylinder, i.e., when the hydraulic cylinder is not working. δ is the expansion of the sealing ring (4). The relationship between l, h and the leakage q of the hydraulic cylinder satisfies Where d is the inner diameter of the sealing ring, Δp = p A -p C , μ is the liquid dynamic viscosity of the hydraulic oil in the cylinder, and ε is the eccentricity of the plunger.

[0018] Furthermore, the oil pressure at the oil hole B is P B , the maximum expansion of the sealing ring δ max With P B , P A Satisfaction between Among them, ν is the Poisson's ratio of the plunger, and E is the elastic modulus of the plunger.

[0019] Furthermore, the minimum expansion amount δ of the sealing ring is min With P B , P C Satisfaction between Wherein, D is the outer diameter of the sealing ring, ν is the Poisson's ratio of the plunger, and E is the elastic modulus of the plunger.

[0020] The beneficial effect of the present invention is that the present invention supports the plunger through multiple groups of hydrostatic bearings, replacing the traditional support ring, ensuring the floating of the plunger, controlling the leakage of the working chamber, and maintaining the pressure P A , so that the hydraulic cylinder can output force stably. And through the pressure oil P C and PB The pressure drop, clearance and eccentricity of the annular gap are controlled in coordination to replace the traditional sealing ring. The plunger of the hydraulic cylinder and other parts such as the cylinder barrel have no contact, thereby achieving zero friction of the plunger, increasing the service life of the hydraulic cylinder and reducing the risk of hydraulic oil leakage in the hydraulic cylinder. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0022] Figure 1 It is a structural schematic diagram of the zero-friction hydraulic cylinder in the present invention.

[0023] Figure 2 It is a schematic diagram of the axial pressure distribution of the plunger in the present invention.

[0024] Figure 3 It is used to reflect Figure 2 MM section view of the circumferential pressure distribution of the plunger at the hydrostatic bearing position at the oil inlet hole E when the middle plunger is not eccentric.

[0025] Figure 4 It is used to reflect Figure 2 NN-axis cross-sectional view of the circumferential pressure distribution of the plunger at the hydrostatic bearing position at the oil inlet hole D when the middle plunger is not eccentric.

[0026] Figure 5 It is a schematic diagram of the hydraulic cylinder when the plunger is deflected by external side load or bending moment in the present invention.

[0027] Figure 6 It is used to reflect Figure 4 The JJ-axis cross-sectional view of the circumferential pressure distribution of the plunger at the static pressure bearing position at the oil inlet hole E when the plunger is deflected by external side load or bending moment.

[0028] Figure 7 It is used to reflect Figure 4 The KK-direction cross-sectional diagram of the circumferential pressure distribution of the plunger at the static pressure bearing position at the oil inlet hole D when the plunger is deflected by external side load or bending moment.

[0029] Figure 8 It is a schematic diagram of the force of the sealing ring in the present invention.

[0030] Fig. 9 It is a schematic diagram of the force on the sealing ring when the plunger is eccentric in the present invention.

[0031] In the figure: 1. Cylinder barrel; 2. Cylinder bottom; 3. Plunger; 4. Sealing ring; 5. Working oil chamber; 6. Adjusting oil chamber; 7. Oil channel; 8. Oil pad. DETAILED DESCRIPTION

[0032] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0033] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0034] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] Reference Figure 1-9 A zero-friction hydraulic cylinder comprises a cylinder barrel 1, a cylinder bottom 2, a plunger 3 and a sealing ring 4. The cylinder barrel 1 and the cylinder bottom 2 are fixedly connected together by fasteners. The plunger 3 is inserted into the cylinder barrel 1 from one end of the cylinder barrel 1 away from the cylinder bottom 2 and can be suspended in the cylinder barrel 1. An annular gap is formed between the plunger 3 and the sealing ring 4, and a working oil chamber 5 is formed between the plunger 3 and the cylinder bottom 2.

[0036] A sealing groove is arranged on the inner wall of one end of the bottom of the cylinder barrel 1 close to the cylinder bottom 2. The sealing groove is arranged in an annular shape. A sealing ring 4 is floatingly arranged in the sealing groove. The sealing ring 4 is arranged close to one side of the axis of the cylinder barrel 1. The sealing ring 4 is sealed against the inner wall of the sealing groove and the cylinder bottom 2. An adjusting oil chamber 6 is formed between the sealing ring 4 and the bottom of the sealing groove and the cylinder bottom 2.

[0037] A plurality of oil holes are arranged on the inner wall of the cylinder barrel 1 along the axial direction of the cylinder barrel 1. Specifically, the plurality of oil holes are arranged along the direction from the cylinder bottom 2 to the open end of the cylinder barrel 1, namely: oil hole B, oil hole C, oil hole L1, oil hole D, oil hole L2, oil hole E, and oil hole L3. Among them, a plurality of oil holes E and oil holes D are arranged along the circumference of the cylinder barrel 1. In this embodiment, four oil holes E and oil holes D are arranged along the axial direction of the cylinder barrel 1, namely, oil hole E1, oil hole E2, oil hole E3, oil hole E4, oil hole D1, oil hole D2, oil hole D3, and oil hole D4. Among them, a plurality of annular grooves are arranged on the inner wall of the cylinder barrel 1, respectively, which are opposite to the oil hole C, oil hole L1, oil hole D, oil hole L2, oil hole E, and oil hole L3.

[0038] Among them, oil holes L1, L2, and L3 are all oil drain holes, oil holes D and E are oil inlet holes, and an oil pad 8 is arranged in the cylinder 1. The oil inlet hole, the oil drain hole and the oil pad 8 together form a hydrostatic bearing. In this embodiment, the oil pad 8 is arranged opposite to the oil inlet hole and the oil drain hole. The oil entering the cylinder 1 through the oil hole D is drained from the oil holes L1 and L2 via the oil pad 8, and the oil entering the cylinder 1 through the oil hole E is drained from the oil holes L2 and L3 via the oil pad 8, thereby forming two groups of hydrostatic bearings. In a natural state, the gap between the plunger 3 and the cylinder 1 is equal everywhere, and the pressure in the hydrostatic chamber is balanced, so that the plunger 3 floats in the cylinder 1. When the plunger 3 is subjected to external lateral loads or bending moments, the gaps between the plunger 3 and the cylinder 1 are not equal everywhere. The unequal gaps change the pressure in the hydrostatic chamber, generating a liquid pressure to resist the external lateral loads and bending moments, and still making the plunger 3 float in the middle of the cylinder 1.

[0039] Oil hole C is the oil filling hole. Add oil pressure P to oil hole C. C , the pressure oil in the oil hole C finally flows to the oil hole L1 to leak out, and the oil hole C is located on the side of the sealing ring 4 away from the cylinder bottom 2. An oil inlet A is provided on the side wall of the cylinder bottom 2, and an oil channel 7 is provided in the cylinder bottom 2. The oil channel 7 connects the oil inlet A with the working oil chamber 5. The end of the oil channel 7 connected with the working oil chamber 5 is opposite to the axis of the cylinder barrel 1. The hydraulic oil enters the working oil chamber 5 from the oil inlet A and acts on the end of the plunger 3, so that the plunger 3 outputs thrust. The oil pressure acting on the end of the plunger 3 is P A .P C Slightly lower than P A , a gradient pressure is formed from bottom to top inside the sealing ring 4, which is P A Gradually reduce to P C , but the pressure drop is very low, the pressure difference Δp=p A -p C , so that the leakage of the working chamber is also very low.

[0040] It should be noted that the leakage of the annular gap is related to the pressure drop, oil viscosity, pore size, gap, hole length, eccentricity, etc. The leakage calculation formula is Among them, d is the inner diameter of the sealing ring 4, D is the outer diameter of the sealing ring 4, and h is the single-sided gap between the plunger 3 and the sealing ring 4 to form an annular gap. The gap is calculated according to the formula h0 is the initial clearance after dimension processing and equipment when there is no pressure in the cylinder 1, i.e. when the hydraulic cylinder is not working. l is the clearance length, i.e. the length between the end of the plunger 3 close to the working oil chamber 5 and the oil hole C along the axial direction of the cylinder 1. μ is the liquid dynamic viscosity of the hydraulic oil in the cylinder 1. ε is the eccentricity of the plunger 3. e is the eccentricity.

[0041] The oil hole B is connected to the regulating oil chamber 6, and the oil pressure P is added to the regulating oil chamber 6 through the oil hole B. B , P B Apply uniform external pressure to the sealing ring 4 to limit the expansion of the sealing ring 4 due to the internal pressure, control the small gap between the plunger 3 and the sealing ring 4, and control the leakage of the working chamber. The maximum expansion amount of the sealing ring 4 is, The minimum expansion is ν is the Poisson's ratio of the sealing ring 4 , and E is the elastic modulus of the sealing ring 4 .

[0042] Example 1

[0043] There is a hydraulic cylinder, whose inner diameter d of the cylinder 1 is 400mm, the outer diameter D is 500mm, the initial gap h0 of the annular gap between the plunger 3 and the inner wall of the cylinder 1 is 0.05mm, the elastic modulus of the steel used to make the sealing ring 4 is E=206GPa, the Poisson's ratio is ν=0.3, the hydraulic cylinder uses 46# mineral oil, its dynamic viscosity μ=0.04Pa.s at 50℃, and the distance l=300mm between the oil hole C and the bottom of the plunger 3. Set the oil inlet pressure P A =30MPa, oil outlet pressure Pc=29MPa.

[0044] If the external pressure P B =26.22MPa, the maximum expansion Minimum expansion One-side clearance Pressure difference Δp=p A -p C =1MPa.

[0045] Assuming that the plunger 3 is in a non-eccentric state and the eccentricity ε = 0, the leakage

[0046]

[0047] Comparative Example 1

[0048] Assuming that the plunger 3 is completely eccentric and the eccentricity ε = 1, the leakage

[0049]

[0050] The leakage of the plunger 3 in the eccentric state is only 2.5 times that in the non-eccentric state, so the floating sealing ring 4 is designed to reduce the eccentricity, which can reduce leakage to a certain extent and avoid contact between the sealing ring 4 and the plunger 3 to generate friction.

[0051] Comparative Example 2

[0052] Assuming the oil outlet pressure Pc = 0, and other parameters are the same as those in Example 1, the minimum expansion amount is

[0053]

[0054] One-side clearance That is, the sealing ring 4 shrinks excessively and locks the plunger 3, and the plunger 3 loses the function of sliding up and down. Therefore, the difference between the oil outlet pressure and the oil inlet pressure cannot be too large, and a certain gap needs to be maintained between the sealing ring 4 and the plunger 3.

[0055] And even if we assume that the gap can remain unchanged, the oil outlet pressure is Pc = 0, that is, Δp = p A -p C =30MPa, since the leakage amount is proportional to the pressure difference, the leakage amount will be 30 times that of Example 1.

[0056] Comparative Example 3

[0057] Assuming the external pressure P B = 0, that is, the expansion of the sealing ring 4 is uncontrolled, and other parameters are the same as those in Example 1, then the maximum expansion amount Minimum expansion One-side clearance Leakage

[0058]

[0059] The result is 52 to 75 times the leakage amount in Example 1. This is because without control, the expansion amount δ reaches several times the initial single-sided gap h0, which causes the final single-sided gap h to increase exponentially, and the leakage amount q is exponentially related to h, making the leakage amount uncontrollable. Therefore, controlling the expansion amount δ is the most critical, and increasing the external pressure is a very effective way to control external expansion.

[0060] In summary, the present application supports the plunger 3 through two sets of hydrostatic bearings, replacing the traditional support ring, resisting the external lateral force or bending moment, ensuring the floating of the plunger 3, and maintaining the pressure P A , so that the hydraulic cylinder can output force stably.

[0061] And through the pressure oil P C and P BThe pressure drop, clearance and eccentricity of the annular gap are controlled in a coordinated manner to replace the traditional sealing ring. The plunger 3 of the hydraulic cylinder and other parts such as the cylinder barrel 1 have no contact, thus achieving zero friction.

[0062] When the sealing ring 4 is deformed, the pressure oil P C and P B Cooperate with each other, because P A With P C The pressure gradient between the sealing ring 4 is compressed and deformed to form a cone, and the hydraulic oil exerts axial and radial forces on the sealing ring 4. Figure 7 The sealing ring 4 can be controlled to float with the plunger 3 without causing eccentricity, thereby controlling leakage of the working chamber.

[0063] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A zero-friction hydraulic cylinder, characterized in that: include, A cylinder barrel (1), wherein the bottom of the cylinder barrel (1) is connected to a cylinder bottom (2); A plunger (3), the plunger (3) being inserted into the cylinder (1) and forming an annular gap with the inner wall of the cylinder (1); A sealing ring (4), wherein the sealing ring (4) is embedded in the inner wall of the cylinder (1), and the sealing ring (4) and the plunger (3) are capable of floating relative to each other; An oil inlet hole and an oil drain hole are provided on the side wall of the cylinder barrel (1); an oil pad (8) is provided in the cylinder barrel (1); the oil inlet hole, the oil drain hole and the oil pad (8) form at least two groups of static pressure bearings for supporting the plunger (3) to float in the cylinder barrel (1); an oil inlet A for injecting oil between the cylinder bottom (2) and the plunger (3) is provided on the cylinder bottom (2); an oil hole B for acting on the sealing ring (4) to resist the oil pressure in the annular gap is provided on the side wall of the cylinder barrel (1); an oil injection hole C is provided on the side wall of the cylinder barrel (1); the oil injection hole C is located on the side of the oil hole B away from the oil inlet A; the oil pressure P of the oil injection hole C is 0.0447 W. C Less than the oil pressure P acting on the plunger (3) at the oil inlet A A .

2. The zero-friction hydraulic cylinder according to claim 1, characterized in that: The oil filling hole C is arranged close to the sealing ring (4).

3. The zero-friction hydraulic cylinder according to claim 1, characterized in that: A plurality of oil inlet holes are arranged along the circumference of the cylinder barrel (1).

4. The zero-friction hydraulic cylinder according to claim 1, characterized in that: A sealing groove is provided on the inner side wall of one end of the bottom of the cylinder barrel (1) close to the cylinder bottom (2); the sealing groove is arranged in an annular shape; the sealing ring (4) is floatingly arranged in the sealing groove, and the sealing ring (4) is arranged close to one side of the axis of the cylinder barrel (1); and an adjusting oil chamber (6) connected to the oil hole B is formed between the sealing ring (4), the bottom of the sealing groove, and the cylinder bottom (2).

5. The zero-friction hydraulic cylinder according to claim 1, characterized in that: A working oil chamber (5) is formed between the cylinder bottom (2) and the plunger (3), and an oil passage (7) is provided on the cylinder bottom (2), wherein the oil passage (7) connects the working oil chamber (5) with the oil inlet A.

6. The zero-friction hydraulic cylinder according to claim 5, characterized in that: One end of the oil passage (7) communicating with the working oil chamber (5) is opposite to the axis of the cylinder barrel (1).

7. The zero-friction hydraulic cylinder according to claim 1, characterized in that: The distance between the oil filling hole C and the bottom surface of the plunger (3) is l, and the single-side gap of the annular gap formed between the plunger (3) and the sealing ring (4) is h. h0 is the initial clearance after dimension processing and assembly when there is no pressure in the hydraulic cylinder, i.e., when the hydraulic cylinder is not working. δ is the expansion of the sealing ring (4). The relationship between l, h and the leakage q of the hydraulic cylinder satisfies Where d is the inner diameter of the sealing ring (4), Δp = p A -p C , μ is the liquid dynamic viscosity of the hydraulic oil in the cylinder (1), and ε is the eccentricity of the plunger (3).

8. The zero-friction hydraulic cylinder according to claim 1, characterized in that: The oil pressure at the oil hole B is P B , the maximum expansion amount δ of the sealing ring (4) max With P B , P A Satisfaction between Wherein, D is the outer diameter of the sealing ring (4), ν is the Poisson's ratio of the sealing ring (4), and E is the elastic modulus of the sealing ring (4).

9. The zero-friction hydraulic cylinder according to claim 8, characterized in that: The minimum expansion amount δ of the sealing ring (4) min With P B , P C Satisfaction between Wherein, ν is the Poisson's ratio of the sealing ring (4), and E is the elastic modulus of the sealing ring (4).

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