Hydrostatic screw and method for controlling the same

Abstract

The application discloses a kind of static pressure screw rod and its control method.The static pressure screw rod includes screw rod, screw rod is provided with outer thread, first through hole and axle hole, outer thread is equipped with static pressure cavity, axle hole extends along the axial direction of screw rod, and the two ends of first through hole are communicated with static pressure cavity and axle hole respectively;Nut is sleeved on screw rod, and inner thread is provided in nut and engaged with outer thread;Oil supply shaft is worn in axle hole, and the outer surface of oil supply shaft is provided with spiral groove for communicating first through hole, spiral groove is spirally arranged along the length direction of oil supply shaft, and the axial direction of oil supply shaft is provided with oil supply hole, and the second through hole of oil supply shaft is provided with the second through hole for communicating spiral groove and oil supply hole.The static pressure screw rod and its control method of the application can solve the problem of difficulty in machining nut inner thread spiral surface oil cavity on static pressure nut in the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of precision transmission, in particular to a hydrostatic screw and a control method thereof. BACKGROUND

[0002] The hydrostatic screw is a structure for converting rotary motion into linear motion by using screw transmission principle, mainly including a screw rod and a nut. The nut of the hydrostatic screw is provided with a hydrostatic oil cavity on the side wall of the internal thread, and a hydrostatic oil film is located between the hydrostatic nut and the screw rod. The hydrostatic nut and the screw rod do not contact each other, so there is no wear between the hydrostatic nut and the screw rod, and the hydrostatic screw has the characteristics of high load capacity, high vibration resistance, no crawling at low speed, and high positioning accuracy.

[0003] Although the hydrostatic nut has many advantages, its application is not widespread. The main reason is that the hydrostatic oil cavity of the hydrostatic nut is located on the spiral surface of the internal thread of the hydrostatic nut, the operation space is small, and the machining is difficult. Moreover, due to the need to machine the spiral surface oil cavity of the internal thread of the nut, the inner diameter of the nut is affected by the machining tool, and the diameter of the nut is generally greater than 40 mm. The effective spiral surface that can be machined has at most 4-6 turns, and the effective load number is limited. SUMMARY

[0004] The main purpose of the present application is to provide a hydrostatic screw and a control method thereof, which at least solve the problem of difficulty in machining the spiral surface oil cavity of the internal thread of the hydrostatic nut in the prior art.

[0005] According to one aspect of the present application, a hydrostatic screw is provided, comprising:

[0006] a screw rod, the screw rod being provided with an external thread, a first through hole and a shaft hole, the external thread being provided with a hydrostatic cavity, the shaft hole extending along the axial direction of the screw rod, and the two ends of the first through hole being in communication with the hydrostatic cavity and the shaft hole, respectively;

[0007] a nut, the nut being sleeved on the screw rod, and the nut being provided with an internal thread engaged with the external thread;

[0008] a oil supply shaft, the oil supply shaft being arranged in the shaft hole, the outer surface of the oil supply shaft being provided with a spiral groove for communicating with the first through hole, the spiral groove being arranged spirally along the length direction of the oil supply shaft, the oil supply shaft being provided with an oil supply hole in the axial direction, and the oil supply shaft being provided with a second through hole for communicating the spiral groove with the oil supply hole.

[0009] Further, the external thread comprises a spiral tooth, and a plurality of hydrostatic cavities are arranged on one turn of the spiral tooth.

[0010] Further, the helical tooth comprises a first helical surface and a second helical surface, and the first helical surface and the second helical surface of the helical tooth are provided with a plurality of static pressure cavities.

[0011] Further, the static pressure cavities on the first helical surface and the second helical surface of the helical tooth are provided in one-to-one correspondence, and the corresponding static pressure cavities comprise a first static pressure cavity and a second static pressure cavity, and the first through hole communicating the first static pressure cavity and the shaft hole and the first through hole communicating the second static pressure cavity and the shaft hole are arranged in a V shape.

[0012] Further, a plurality of second through holes are arranged on the helical groove of the oil supply shaft.

[0013] Further, the rotation direction of the external thread is consistent with the rotation direction of the helical groove, the external thread comprises a helical tooth, the screw rod is provided with N turns of the helical tooth in the effective length L, the oil supply shaft and the screw rod are in the same effective length L, and the helical groove has X turns of the helical groove, wherein X satisfies the relationship: N-1≤X≤N+1.

[0014] Further, the oil supply hole is arranged through the oil supply shaft, both ends of the oil supply hole are provided with plugs, the oil supply shaft is provided with an oil inlet channel, the oil inlet channel extends along the radial direction of the oil supply shaft and communicates with the oil supply hole, and the oil inlet channel is located between the two plugs.

[0015] Further, the shaft hole is provided with an oil sealing end cover at both ends, respectively, the oil sealing end cover is sleeved on the oil supply shaft to seal the gap between the shaft hole and the oil supply shaft.

[0016] Further, the screw rod or the nut is provided with an oil return channel.

[0017] On the other hand, the application also provides a control method of the static pressure screw, which is used for controlling the static pressure screw, and the control method of the static pressure screw comprises:

[0018] The nut is controlled to rotate at a speed n1 and move relative to the screw rod at a speed v1, the oil supply shaft is controlled to rotate at a speed n2 and move relative to the screw rod at a speed v 1 . 1 ;

[0019] Wherein, n1, v1, n 1 , v 1 and n2 satisfy the relationship:

[0020] v 1= v1= n 1 P2= n1P1;

[0021] n 1 = n1P1 / P2= n1X / N;

[0022] n2= n1+n 1 = n 1 *(X+N) / N;

[0023] Wherein, P1 is the lead of the nut and the screw rod, P2 is the helical groove pitch of the oil supply shaft, N is the number of turns of the external thread helical tooth within the effective length L, and X is the number of helical grooves on the outside of the oil supply shaft within the effective length L.

[0024] In the present application, by providing an external thread on the screw rod and a static pressure cavity on the external thread, the difficulty of providing a static pressure cavity on the nut in the prior art can be reduced, and the tool is no longer limited by the size of the space, and the machining process is simpler. The nut is sleeved on the screw rod, and the nut is internally provided with an internal thread engaged with the external thread, the threads of the nut and the screw rod are engaged, the overlapping area of the nut and the screw rod is increased, the effective bearing turns of the nut are not limited, and the nut can bear more turns of threads, and the bearing capacity is higher. There is an axial hole in the screw rod, the axial hole extends along the axial direction of the screw rod, the oil supply shaft is arranged in the axial hole, the two ends of the first through hole are respectively communicated with the static pressure cavity and the axial hole, the oil supply shaft is arranged in the axial hole, and the outer surface of the oil supply shaft is provided with a helical groove for communicating the first through hole, and the helical groove is spirally arranged along the length direction of the oil supply shaft. In addition, the oil supply hole is arranged in the axial direction of the oil supply shaft, and the second through hole is arranged on the oil supply shaft and communicates the helical groove and the oil supply hole, so that the oil passage is communicated, and it is beneficial to form a static pressure oil film between the screw rod and the nut, and better transmission can be realized. In addition, by providing the static pressure cavity on the screw rod, the screw rod and the nut can also adopt a smaller nominal diameter, and the application range is wider. BRIEF DESCRIPTION OF DRAWINGS

[0025] The drawings described herein are used to provide a further understanding of the present application, and form a part of the present application. The illustrative embodiments of the present application and their description serve to explain the present application without forming an improper limitation on the present application. In the drawings:

[0026] Figure 1 The overall structure schematic view of the static pressure lead screw disclosed in the embodiments of the present application;

[0027] Figure 2 The partial cross-sectional view of the static pressure lead screw disclosed in the embodiments of the present application when viewed from a first perspective;

[0028] Figure 3 The cross-sectional view of the static pressure lead screw disclosed in the embodiments of the present application;

[0029] Figure 4 is a local enlarged view of the A area in Figure 3

[0030] Figure 5 is a structural schematic view of a single-side support structure of an oil supply shaft of a static pressure screw disclosed by an embodiment of the present application;

[0031] Figure 6 is a structural schematic view of a double-side support structure of an oil supply shaft of a static pressure screw disclosed by an embodiment of the present application;

[0032] Figure 7 is a sectional view of a static pressure screw disclosed by an embodiment of the present application, in which an oil return channel is formed on a screw rod;

[0033] Figure 8 is a sectional view of a static pressure screw disclosed by an embodiment of the present application, in which an oil return channel is formed on a nut.

[0034] In the above drawings, the following reference signs are used:

[0035] 10, screw rod; 11, shaft hole; 12, first through hole; 13, static pressure cavity; 131, first static pressure cavity; 132, second static pressure cavity; 14, oil sealing edge; 15, external thread; 16, internal thread; 17, tooth crest; 18, tooth root; 20, nut; 30, oil supply shaft; 31, helical groove; 32, oil supply hole; 33, second through hole; 34, oil sealing end cover; 40, overlapping area; 50, rotary joint; 60, shaft coupling; 70, motor; 80, bearing; 90, plug; 100, transmission structure; 101, oil return channel; 102, oil inlet channel; 103, first helical surface; 104, second helical surface. DETAILED DESCRIPTION

[0036] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0037] It should be noted that the terms used herein are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form, unless the context clearly indicates otherwise, and it should also be understood that, when the terms "comprise" and / or "include" are used in the specification, there is a presence of a feature, step, operation, device, component and / or combination thereof.

[0038] ​The foregoing merely illustrates the principles of the application. It will thus be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the application and are thus within its spirit and scope. Furthermore, all examples and conditional language recited herein are principally intended to be only for pedagogical purposes to aid the reader in understanding the principles of the application and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the application, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. It is intended that such equivalents include both currently known equivalents and equivalents developed in the future, i.e., any elements developed that perform the same function regardless of structure. The scope of the present application, therefore, is not intended to be limited to the

[0039] As mentioned in the technical background, in the prior art, the static pressure nut is provided with a static pressure oil cavity on the inner thread side wall, and a static pressure oil film is located between the static pressure nut and the screw rod. The static pressure nut and the screw rod do not contact each other, so there is no wear, and the static pressure nut has the characteristics of high load capacity, high vibration resistance, no crawling at low speed, and high positioning accuracy. Although the static pressure nut has many advantages, its application is not widespread. The main reason is that the static pressure oil cavity of the static pressure nut is located on the spiral surface of the inner thread of the static pressure nut, the operation space is small, and the machining is difficult. In addition, due to the need to machine the inner thread spiral surface oil cavity of the nut, the inner diameter of the nut is affected by the machining tool, and the diameter of the nut is generally greater than 40 mm. The effective spiral surface that can be machined is at most 4-6 turns, and the effective load number is limited. Therefore, the present application provides a static pressure screw rod, which sets the static pressure oil cavity on the screw rod, and through the principle that the difference between the two equal spiral turns is less than 1, at most only one intersection point, and through the differential rotation of the oil supply shaft and the screw rod, a movable continuous oil supply cavity area is formed, and a stable static pressure oil film is formed between the screw rod and the movable nut. The static pressure screw rod of the present application will be described in detail below with reference to the accompanying drawings.

[0040] As Figures 1 to 8 shown, according to an embodiment of the present application, a static pressure screw rod is provided. The static pressure screw rod comprises a screw rod 10, a nut 20, and an oil supply shaft 30.

[0041] In the embodiment, the screw rod 10 is provided with an external thread 15, a first through hole 12 and an axial hole 11, wherein the external thread 15 is provided with a static pressure cavity 13, the axial hole 11 extends along the axial direction of the screw rod 10, and the two ends of the first through hole 12 are respectively communicated with the static pressure cavity 13 and the axial hole 11; a nut 20 is sleeved on the screw rod 10, and the nut 20 is internally provided with an internal thread 16 engaged with the external thread 15; an oil supply shaft 30 is arranged in the axial hole 11, and the outer surface of the oil supply shaft 30 is provided with a spiral groove 31 for communicating the first through hole 12, and the spiral groove 31 is arranged in a spiral manner along the length direction of the oil supply shaft 30; the axial direction of the oil supply shaft 30 is provided with an oil supply hole 32, and the oil supply shaft 30 is provided with a second through hole 33 communicating the spiral groove 31 and the oil supply hole 32.

[0042] In the application, by arranging the external thread 15 on the screw rod 10 and arranging the static pressure cavity 13 on the external thread 15, the difficulty of arranging the static pressure cavity 13 on the nut 20 in the prior art can be reduced, and the tool is no longer limited by the space size, and the machining process is simpler. The nut 20 is sleeved on the screw rod 10, and the nut 20 is internally provided with an internal thread 16 engaged with the external thread 15, and the threads between the nut 20 and the screw rod 10 are engaged, which can improve the formation of the static pressure oil film between the screw rod 10 and the nut 20 during work. The axial hole 11 is arranged in the screw rod 10, and the axial hole 11 extends along the axial direction of the screw rod 10, the oil supply shaft 30 is arranged in the axial hole 11, the two ends of the first through hole 12 are respectively communicated with the static pressure cavity 13 and the axial hole 11, the oil supply shaft 30 is arranged in the axial hole 11, the outer surface of the oil supply shaft 30 is provided with a spiral groove 31 for communicating the first through hole 12, and the spiral groove 31 is arranged in a spiral manner along the length direction of the oil supply shaft 30. In addition, the axial direction of the oil supply shaft 30 is provided with an oil supply hole 32, and the oil supply shaft 30 is provided with a second through hole 33 communicating the spiral groove 31 and the oil supply hole 32. In this way, the oil passage can be communicated during actual work, which is conducive to the formation of the static pressure oil film between the screw rod 10 and the nut 20, and better transmission can be achieved.

[0043] That is to say, by arranging the static pressure cavity 13 on the external thread 15 of the screw rod 10 and arranging the oil supply shaft 30 in the axial hole 11 in the screw rod 10. By such arrangement, the difficulty of arranging the static pressure cavity 13 on the internal thread 16 of the nut 20 in the prior art is reduced, the tool is not limited by the space, and the machining of the static pressure cavity 13 becomes simple. The screw rod 10 and the nut 20 can also adopt a smaller nominal diameter, and the application range is more extensive. In addition, during actual work, the static pressure cavity 13 is arranged on the external thread 15 of the screw rod 10, so that the overlapping area 40 of the nut 20 and the screw rod 10 becomes larger, the effective load number on the nut 20 is not limited, and the nut 20 can adopt more thread numbers for load bearing, and the load bearing capacity is higher.

[0044] In the embodiment, the external thread 15 comprises helical teeth, which can be understood as one circle of the external thread 15 of the screw rod 10 protruding in the helical direction, and a plurality of static pressure cavities 13 are arranged on the helical teeth. Exemplarily, the shape of the external thread 15 can be one of triangular thread, rectangular thread, trapezoidal thread, zigzag thread and other special-shaped thread. In the embodiment, the tooth profile of the external thread 15 is preferably trapezoidal thread, which can improve the adhesion of metal and the anti-skid performance. Alternatively, the shape of the static pressure cavity 13 can be one of fan-shaped static pressure cavity 13 and rectangular static pressure cavity 13. In the embodiment, the static pressure cavity 13 is preferably fan-shaped static pressure cavity 13, because the bearing area of the fan-shaped static pressure cavity 13 is larger.

[0045] Further, a plurality of static pressure cavities 13 are arranged on the first helical surface 103 and the second helical surface 104 (which can be understood as the two side surfaces of one circle of the external thread 15) arranged oppositely on the helical teeth of the external thread 15. Exemplarily, the number of static pressure cavities 13 on the helical teeth can be 1, 2, 3, 4, etc. In the embodiment, 3 or 4 fan-shaped static pressure cavities 13 are arranged on the two sides of each circle of thread, which can ensure that the stress of the static pressure cavity is more stable in each direction.

[0046] Further, the static pressure cavities 13 are one-to-one corresponding on the first helical surface 103 and the second helical surface 104 on one circle of helical teeth of the external thread 15. Such arrangement can realize smooth oil supply in actual work. The corresponding static pressure cavities 13 comprise a first static pressure cavity 131 and a second static pressure cavity 132, and the first through hole 12 communicating the first static pressure cavity 131 and the shaft hole 11 and the first through hole 12 communicating the second static pressure cavity 132 and the shaft hole 11 are arranged in a V shape. The first through hole 12 of the corresponding static pressure cavities 13 on the two side surfaces arranged oppositely is arranged in a V shape, which can supply oil to both sides at one time and improve the oil supply efficiency.

[0047] In the application, a plurality of second through holes 33 are arranged on one circle of helical grooves 31 on the oil supply shaft 30. Exemplarily, the number of second through holes 33 can be 1, 2, 3, 4, etc. The outer diameter of the oil supply shaft 30 is matched with the inner diameter of the shaft hole 11 of the screw rod 10, the outer surface of the oil supply shaft 30 is provided with a helical groove 31, and the second through holes 33 are uniformly distributed along the helical groove 31 to communicate the oil supply holes 32 in the oil supply shaft 30. In the embodiment, the number of second through holes 33 on each circle of helical grooves 31 is the same as the number of single-side fan-shaped static pressure cavities 13 of the trapezoidal external thread 15 of the screw rod 10 (3 or 4 second through holes 33 per circle). Corresponding the number of second through holes 33 to the number of static pressure cavities 13, it is beneficial to realize oil supply in actual work, to ensure that the hydraulic oil in the oil supply shaft 30 can smoothly enter the gap between the screw rod 10 and the nut 20 to form a static pressure oil film, which is beneficial to transmission.

[0048] Referring to Figures 1 to 3 As shown, the rotation direction of the external thread 15 is consistent with the rotation direction of the helical groove 31. In this way, during actual operation, the oil supply shaft 30 can rotate relative to the screw 10, so that the nut 20 and the screw 10 have a larger overlapping area; at this time, the effective load number of the nut 20 is not limited, and the nut 20 can use more thread turns for load bearing, and the load bearing capacity is higher. The external thread 15 of the screw 10 includes helical teeth (which can be understood as the protruding part of the external thread 15 that rotates one turn along the rotation direction of the external thread 15 of the screw 10), and the screw 10 is provided with N turns of helical teeth in the effective length L, and the oil supply shaft 30 and the screw 10 are in the same effective length L (which can be understood as the part of the helical groove 31 that is in communication with the first through hole 12 of the screw 10 under working conditions), and the helical groove 31 has X turns of helical grooves. Among them, X needs to satisfy the relationship: N-1≤X≤N+1. When X satisfies the relationship N-1≤X≤N+1, the difference between the two equal-length helical turns is less than 1, and according to the principle that there is at most one intersection point, through the differential rotation of the oil supply shaft 30 and the screw 10, a movable continuous oil supply cavity area is formed, and a stable hydrostatic oil film is formed between the screw 10 and the movable nut 20.

[0049] Specifically, since the external thread 15 of the screw 10 is uniformly distributed with fan-shaped static pressure cavities 13 on the helical surface, and each static pressure cavity 13 is provided with a first through hole 12 that is communicated to the internal shaft hole 11 of the screw 10, therefore the first through hole 12 inside the internal shaft hole 11 of the screw 10 is also distributed according to the helical line, and the pitch is also the same as the pitch of the external thread 15 of the screw 10. In addition, when the number of helical turns of the external helical groove 31 of the oil supply shaft 30 in the same length is less than or equal to one turn from the number of helical turns of the first through hole 12 distributed in the internal shaft hole 11 of the screw 10, the helical line distributed in the external helical groove 31 of the oil supply shaft 30 and the helical line distributed in the first through hole 12 has at most one intersection point. Since both helical lines have a certain width (the diameter of the first through hole 12 and the width of the helical groove 31), therefore in at most one area, the helical groove 31 of the oil supply shaft 30 and the first through hole 12 inside the screw 10 are overlapping and communicated. When this area is located at the nut 20, the hydraulic oil comes out from the hydraulic station (provided externally, not shown in the figure). Referring to Figure 3 and Figure 4 As shown, through the oil supply hole 32 in the oil supply shaft 30, the hydraulic oil enters the second through hole 33, and then enters the helical groove 31 from the second through hole 33. Only in the overlapping area 40, the helical groove 31 of the oil supply shaft 30 and the first through hole 12 on the screw 10 are communicated, at this time, the hydraulic oil in the helical groove 31 can enter the fan-shaped static pressure cavity 13 on the side surface of the external thread 15 through the first through hole 12 on the screw 10 in the overlapping area 40, and form a hydrostatic oil film between the nut 20 and the screw 10. Finally, the hydraulic oil enters the top gap and the bottom gap from the oil sealing edge 14, and flows out from the end surface of the internal thread 16 of the nut 20 to return to the hydraulic oil tank (not shown in the figure).

[0050] As shown in Figure 5 and Figure 6 , the oil supply hole 32 is provided through the oil supply shaft 30, and the two ends of the oil supply hole 32 are provided with plugs 90, which block the two ends of the oil supply shaft 30 to prevent hydraulic oil from flowing out and leaking along the two ends of the oil supply shaft 30. In this embodiment, the oil supply shaft 30 is provided with an oil inlet channel 102 extending in the radial direction of the oil supply shaft 30 and communicating with the oil supply hole 32. In actual processing, the oil inlet channel 102 of this embodiment is provided on the rotary joint 50 with bearings, and the oil inlet channel 102 is located between the two plugs 90, so that the leakage of hydraulic oil can be better prevented. And the oil sealing end cover 34 is provided at both ends of the spiral groove 31, which is sleeved on the oil supply shaft 30 to seal the gap between the shaft hole 11 and the oil supply shaft 30, preventing hydraulic oil from flowing out from both ends of the spiral groove.

[0051] In this embodiment, the static pressure cavity 13 is arranged on the screw rod 10. According to the principle that the number difference of two equal length spiral coils is less than 1, a movable continuous oil supply cavity area is formed by the differential rotation of the oil supply shaft 30 and the screw rod 10, and a stable static pressure oil film is formed between the screw rod 10 and the movable nut 20. The size of the overlapping area depends on two aspects: on the one hand, it depends on the pitch of the spiral groove 31 and the pitch of the spiral line distributed on the inner side of the first through hole 12 of the shaft hole 11 (the spiral line of the outer thread 15 of the screw rod 10). The closer the pitch of the two spiral lines, the closer the two spiral lines, and the larger the overlapping area, the more the number of covered threads; on the contrary, the closer the number difference of the two spiral coils is to 1, the smaller the overlapping area 40, and the fewer the number of covered threads. On the other hand, it depends on the size of the first through hole 12 and the width of the spiral groove 31. The wider the width, the larger the overlapping area 40, and vice versa. Therefore, the size of the overlapping area 40 can be adjusted according to the above two aspects to control the effective load thread number of the nut 20. In theory, the minimum can be achieved by single static pressure cavity 13 oil supply, and the effective load number of the nut 20 is not limited. As shown in Figure 7 and Figure 8 , when the number of oil supply turns is large, an oil return channel 101 can be provided on the nut 20 or the screw rod 10 for oil return. The oil return channel 101 is composed of two parts, including a first conveying section and a second conveying section connected to form. Specifically, an oil return hole is provided on the tooth top 17 or the tooth bottom 18 of the nut 20 or the screw rod 10, and then the oil return hole on the tooth top 17 or the tooth bottom 18 is connected with the first conveying section, and in the meshing area of the screw rod 10 and the nut 20, the first conveying section on each tooth top 17 or tooth bottom 18 is in communication with the second conveying section, so that the oil return can be realized.

[0052] In this embodiment, the screw 10 requires support at both ends. Since there is a small gap between the oil supply shaft 30 and the screw 10 shaft hole 11, when the screw rotates, the oil in the spiral groove 31 enters the gap, forming a lubricating oil film for support. In actual operation, the screw 10 can be supported and driven on one side, or it can be supported on both sides.

[0053] Furthermore, for the single-sided support of the oil supply shaft 30, such as Figure 5 As shown, one end of the oil supply shaft 30 can be located inside the shaft hole 11, and the other end extends out from the shaft hole 11 of the screw 10. The journal is connected to a rotary joint 50 with a bearing, which can supply oil while rotating. The end is connected to the motor 70 through a coupling 60, and oil sealing end caps 34 are provided at both ends of the spiral groove 31 to prevent hydraulic oil from flowing out from both ends of the spiral groove 31. Plugs 90 are provided at both ends of the oil supply hole 32 to prevent hydraulic oil from flowing out from both ends of the oil supply hole 32. The screw 10 can be supported at both ends, with hydrostatic bearings 80 or ball bearings 80 at both ends for support, and the end is connected to the motor 70 through a coupling 60.

[0054] Furthermore, for the oil supply shaft 30 with double-sided support, such as Figure 6 As shown, both ends of the oil supply shaft 30 extend from the shaft hole 11 of the screw 10. One end is connected to a rotary joint 50 with a bearing, which allows for simultaneous rotation and oil supply. The other end is connected to the motor 70 via a coupling 60, and is also supported by a bearing 80. Similarly, oil sealing caps 34 are provided at both ends of the spiral groove 31 to prevent hydraulic oil from flowing out. Plugs 90 are provided at both ends of the oil supply hole 32 to prevent hydraulic oil from flowing out. The screw 10 is also supported at both ends, with hydrostatic bearings 80 or ball bearings 80 at each end. However, since both ends of the screw 10 have oil supply shafts 30 extending from the shaft hole 11, it cannot be directly coaxially connected to the motor 70. A gear or pulley transmission structure 100 can be provided at the end, and the motor 70 can then drive it through the transmission structure 100.

[0055] As can be seen from the above embodiments, the hydrostatic screw includes: screw 10, nut 20 and oil supply shaft 30.

[0056] First, the static pressure chamber 13 is set on the external thread 15 of the screw 10, and a shaft hole 11 is provided inside the screw 10. The oil supply shaft 30 is located inside the screw 10, and the nut 20 is sleeved on the outside of the screw 10. The external thread 15 of the screw 10 and the internal thread 16 of the nut 20 can mesh with each other. The outer side of the oil supply shaft 30 is provided with a spiral groove 31, and the direction of the spiral groove 31 is consistent with the direction of the external thread 15.

[0057] Secondly, a first through hole 12 is arranged between the static pressure cavity 13 and the shaft hole 11 to communicate the two parts; a second through hole 33 is arranged on the spiral groove 31 outside the oil supply shaft 30, and an oil supply hole 32 is arranged inside the oil supply shaft 30 to communicate the second through hole 33.

[0058] Finally, according to the principle that when the number difference of two equal-length spiral coils is less than 1, there is at most one intersection point, a movable continuous oil supply oil cavity area is formed by the differential rotation of the oil supply shaft 30 and the screw rod 10, and a stable static pressure oil film is formed between the screw rod 10 and the movable nut 20.

[0059] Through the above arrangement, the machining difficulty of the static pressure cavity 13 is reduced, the nut 20 and the screw rod 10 can adopt a smaller nominal diameter, and the application range is more extensive. Since the oil supply area (overlap area 40) has a large adjustment range, the effective load number of the nut 20 is not limited, the nut 20 can adopt more thread turns for load bearing, and the load bearing capacity is higher.

[0060] In combination Figures 1 to 8 As shown in the figure, the application also provides a control method of the static pressure screw. The overlap area 40 of the static pressure screw is always kept in coincidence with the nut 20, the first through hole 12 in the static pressure cavity 13 on the screw rod 10 in the meshing area of the nut 20, and the spiral groove 31 of the oil supply shaft 30 are always kept in a state of communication, and the other non-meshing areas are always kept in a closed state.

[0061] Specifically, the control method of the static pressure screw in the embodiment includes:

[0062] When the nut 20 moves, the nut 20 is controlled to rotate at a speed n1 and move relative to the screw rod 10 at a speed v1 (which can be understood as moving in the axial direction of the screw rod 10), the lead of the screw rod 10 and the nut 20 is P1, the length of the screw rod 10 and the nut 20 is L, the number of threads is N, the pitch of the spiral groove 31 of the oil supply shaft 30 is P2, the length of the spiral groove 31 of the oil supply shaft 30 is L, and the number of turns of the spiral groove 31 is X, which needs to satisfy the relationship N-1≤X≤N+1, then the following relationship exists:

[0063] P1=L / N

[0064] P2=L / X

[0065] v1=n1*P1

[0066] Further, in order to make the coincident area 40 move with the nut 20, the coincident area 40 needs to move with the nut 20. Therefore, the oil supply shaft 30 needs to rotate relative to the screw 10, so that the feeding speed of the coincident area 40 is equal to the moving speed of the nut 20. The relative feeding speed (which can be understood as the movement speed of the oil supply shaft 30 in the axial direction of the screw 10) when the oil supply shaft 30 rotates relative to the screw 10 is v 1 , the relative rotation speed of the oil supply shaft 30 relative to the screw 10 is n 1 , then:

[0067] v 1 =v1=n 1 *P2=n1*P1

[0068] n 1 =n1*P1 / P2=n1*X / N

[0069] Further, the rotation speed of the oil supply shaft 30 is n2, which is the superposition of the rotation speed of the screw 10 and the relative rotation speed. Therefore, n2 needs to satisfy the following relationship:

[0070] n2=n1+n 1 =n 1 *(X+N) / N

[0071] Further, when the above relationship is satisfied, the coincident area 40 can always coincide with the nut 20, and the first through hole 12 in the static pressure cavity 13 and the spiral groove 31 of the oil supply shaft 30 in the meshing area of the nut 20 are always in communication, and the other non-meshing areas are always in a closed state.

[0072] After the above control method, the coincident area 40 can always coincide with the nut 20, and the first through hole 12 in the static pressure cavity 13 and the spiral groove 31 of the oil supply shaft 30 in the meshing area of the nut 20 are always in communication, and the other non-meshing areas are always in a closed state; a continuous oil supply state is realized, which can better realize transmission in actual production process. The use of the static pressure ball screw can be more widely used.

[0073] For purposes of the description hereinafter, the orientations in the various drawings will be described as shown in the drawings. However, it will be understood that the device can assume different orientations, e.g. viewed from the bottom, based on the application. Accordingly, the illustrative terms such as "above", "below", "upper", "lower", and the like are used as a shorthand notations to convey the relative positions of an object or feature as shown in the figures. It will be further appreciated that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the figures. For example, if the device described is turned over, then a depiction that was previously described as "above" other parts or steps would then be oriented "below" other parts or steps. Thus, the exemplary term "above" can encompass both an "above" and "below" position depending on the particular orientation being referred to. Similarly, the terms "above" and "below" can include vertical orientations of the device as well as horizontal orientations of the device. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0074] In addition, it should be pointed out that the use of the terms "first", "second" and the like does not indicate any special meaning, but is merely used to distinguish the corresponding parts, and therefore should not be interpreted as limiting the scope of protection of the present application.

[0075] The preferred embodiments of the present application have been described above with the purpose to enable not to limit the scope of protection of the present application. Various alterations and changes can be made by those skilled in the art without departing from the spirit and principles of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A hydrostatic screw, characterized in that The utility model relates to a screw rod (10) is provided with outer thread (15), first through -hole (12) and axle hole (11), is equipped with static pressure cavity (13) on outer thread (15), axle hole (11) extends along the axis direction of screw rod (10), and the both ends of first through -hole (12) are communicated with static pressure cavity (13) and axle hole (11) respectively, Nut (20) is set on screw rod (10), and inner thread (16) is provided in nut (20) and is engaged with outer thread (15), Oil supply shaft (30) is threaded in axle hole (11), and spiral groove (31) for communicating first through -hole (12) is arranged on the outer surface of oil supply shaft (30), spiral groove (31) is arranged along the length direction of oil supply shaft (30), oil supply hole (32) is arranged on the axial direction of oil supply shaft (30), second through -hole (33) is arranged on oil supply shaft (30) and is communicated with spiral groove (31) and oil supply hole (32), Outer thread (15) includes helical tooth, and a plurality of static pressure cavities (13) are arranged on a helical tooth, A helical tooth includes oppositely arranged first helical surface (103) and second helical surface (104), and a plurality of static pressure cavities (13) are arranged on the first helical surface (103) and the second helical surface (104) of a helical tooth, The static pressure cavities (13) on the first helical surface (103) and the second helical surface (104) of a helical tooth are arranged one by one in correspondence, and the corresponding static pressure cavities (13) include first static pressure cavity (131) and second static pressure cavity (132), and the first through -hole (12) communicated with the first static pressure cavity (131) and the axle hole (11) and the first through -hole (12) communicated with the second static pressure cavity (132) and the axle hole (11) are arranged in V shape. A plurality of second through -holes (33) are arranged on a spiral groove (31) on oil supply shaft (30).

2. Hydrostatic screw according to claim 1, characterized in that The rotation direction of outer thread (15) is consistent with the rotation direction of spiral groove (31), outer thread (15) includes helical tooth, screw rod (10) is provided with N helical teeth in effective length L, oil supply shaft (30) is in the same effective length L with screw rod (10), spiral groove (31) has X spiral grooves, wherein X needs to satisfy the relationship: N-1≤X≤N+1.

3. Hydrostatic screw according to claim 1, characterized in that The oil supply hole (32) is arranged through in the oil supply shaft (30), the both ends of the oil supply hole (32) are provided with the plug (90), the oil supply shaft (30) is provided with the oil inlet channel (102), the oil inlet channel (102) extends along the radial direction of the oil supply shaft (30) and is communicated with the oil supply hole (32), and the oil inlet channel (102) is located between the two plugs (90).

4. The hydrostatic screw according to claim 1, characterized in that ​ 5. Hydrostatic screw according to claim 1, characterized in that Two ends of the shaft hole (11) are respectively provided with oil sealing end covers (34), the oil sealing end covers (34) are sleeved on the oil supply shaft (30) to seal the gap between the shaft hole (11) and the oil supply shaft (30).

6. Hydrostatic screw according to any one of claims 1 to 5, characterized in that The screw rod (10) or the nut (20) is provided with an oil return channel (101).

7. A control method of a hydrostatic screw, characterized by, The control method of the hydrostatic ball screw is used for controlling the hydrostatic ball screw in any one of claims 1 to 6, and the control method of the hydrostatic ball screw comprises: controlling the nut (20) to rotate at a rotational speed n1 and to move the nut (20) relative to the screw (10) at a speed v1, and controlling the oil supply shaft (30) to rotate at a rotational speed n2 and to move the oil supply shaft (30) relative to the screw (10) at a speed v 1 moving and rotating at a rotational speed n 1 rotating; wherein n1, v1, n 1 , v 1 and n2 satisfy the relationship: v 1 = v1= n 1 P2=n1P1; n 1 = n1P1 / P2= n1X / N; n2= n1+ n 1 = n 1 *(X+N) / N; Wherein, P1 is the lead distance of the nut (20) and the screw rod (10), P2 is the helical groove (31) pitch of the oil supply shaft (30), N is the number of helical teeth in the effective length L, and X is the number of helical grooves on the outside of the oil supply shaft (30) in the effective length L.

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