A hydraulic backlash eliminator coupling with automatic pressure regulation

Abstract

The present invention belongs to the technical field of mechanical components, and discloses a hydraulic backlash eliminator coupling with automatic pressure regulation. A cavity is formed on the housing; a first split sleeve is inserted into the cavity and is limitedly connected with the housing through a clamping structure; a piston is inserted into the first split sleeve and is connected with the first split sleeve, and a first pressure chamber is formed between the piston and the first split sleeve; a first end cover is inserted into the cavity, sleeved on the piston and fixedly connected with the first split sleeve, and a second pressure chamber is formed between the piston and the first end cover; a second split sleeve is sleeved on the piston, and a spiral chute is arranged on the second split sleeve, and a second connecting member is inserted through the spiral chute and is fixed with the piston; a second end cover is sleeved on the piston and is fixedly connected with the housing; a first pressure control assembly and a second pressure control assembly are respectively communicated with the first pressure chamber and the second pressure chamber. The present invention realizes bidirectional backlash-free transmission of a single-nut screw drive pair, and has high practicability.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical components, and particularly relates to a hydraulic backlash eliminator coupling with automatic pressure adjustment. Background Art

[0002] In the currently widely used high-end precision CNC machine tools, in order to eliminate the backlash that affects the transmission accuracy of the ball screw pair, the precision ball screw pair with a double-nut structure is one of the main precision functional components most frequently used. With its good precision characteristics and long-term usability, it almost occupies most of the market for precision transmission functional components.

[0003] However, in the currently used double-nut structure, there is a fatal flaw. To eliminate the backlash, the double-nut ball screw pair is achieved by adjusting the thickness of the gasket between the two nuts. When the gasket thickness is too large, it will increase the load on the screw, accelerate the wear of the screw, and reduce the service life of the screw pair; when the gasket thickness is too small, the backlash cannot be completely eliminated, resulting in a reduction in transmission accuracy; therefore, when a new screw is shipped from the factory, it is necessary to grind and match the gasket, which is time-consuming and laborious; moreover, since only a certain section of the screw stroke is often used after the installation of the new screw product, after a period of use, the frequently used section wears severely, and the backlash of the ball screw in the section where the full stroke cannot be guaranteed to be evenly used will inevitably be greater than that in the section that is not frequently used; at this time, neither mechanical nor electrical methods can completely compensate for the backlash at different positions of the same screw, so it will inevitably have an adverse and currently ineliminable impact on the transmission accuracy of the ball screw pair. Once the above-mentioned excessive "uneven wear" phenomenon occurs in a certain section of the screw stroke, it is necessary to disassemble the entire machine tool transmission part, remove the screw, and replace it as a whole, resulting in a high maintenance cost.

[0004] In a single-nut ball screw transmission pair, there is no better method to eliminate the backlash except increasing the interference fit between the balls and the raceways in the nut and adopting the point-by-point compensation method of the electrical system, and the disadvantages of the above two methods are obvious. Summary of the Invention

[0005] The present invention provides a hydraulic backlash eliminator coupling with automatic pressure adjustment to overcome the problems existing in the above-mentioned prior art.

[0006] The technical solution of the present invention is as follows:

[0007] A hydraulic backlash eliminator coupling with automatic pressure adjustment, comprising:

[0008] A housing, on which a cavity is provided;

[0009] The first opening sleeve is inserted into the cavity and is limit-connected to the housing through a clamping structure;

[0010] The piston is inserted into the first opening sleeve and is connected to the first opening sleeve through a guiding transmission structure. A first pressure chamber is formed between the piston and the first opening sleeve;

[0011] The first end cap is inserted into the cavity, sleeved on the piston, and fixedly connected to the first opening sleeve. A second pressure chamber is formed between the first end cap and the piston;

[0012] The second opening sleeve is sleeved on the piston. A spiral chute is provided on the second opening sleeve, and a second connecting member is inserted through the spiral chute. The second connecting member is fixedly connected to the piston;

[0013] The second end cap is sleeved on the piston and is fixedly connected to the housing;

[0014] The first pressure control component and the second pressure control component are respectively communicated with the first pressure chamber and the second pressure chamber, and are used for injecting a pressure medium into the first pressure chamber or the second pressure chamber to push the piston to move.

[0015] Preferably, the guiding transmission structure includes:

[0016] A circular boss provided on the end face of the piston. An external spline is provided on the outer circumference of the circular boss, and the external spline meshes with an internal spline on the first opening sleeve. The internal spline is provided in a groove on the first opening sleeve.

[0017] Preferably, the external spline is replaced by a straight-tooth external gear, and the internal spline is replaced by a straight-tooth internal gear.

[0018] Preferably, the clamping structure includes an annular boss provided at one end of the first opening sleeve. The annular boss is clamped in a step groove provided in the housing.

[0019] Preferably, a first flat thrust bearing is further provided between the annular boss and the step groove, and a second flat thrust bearing is provided between the first end cap and the second end cap. The second flat thrust bearing is sleeved on the second opening sleeve.

[0020] Preferably, at least one first seal is provided between the first opening sleeve and the housing, a second seal is provided between the first opening sleeve and the piston, a third seal is provided between the piston and the first end cap, and a fourth seal is provided between the first opening sleeve and the first end cap.

[0021] Preferably, the first pressure control component and the second pressure control component have the same structure.

[0022] Preferably, the first pressure control component includes a first channel opened on the housing. One end of the first channel communicates with the first pressure chamber, and the other end is provided with a first interface which is communicated with an external first pressure medium source. A first pressure adjustment system for adjusting the pressure of the medium in the first pressure chamber is arranged between the first pressure medium source and the first interface.

[0023] Preferably, the first pressure adjustment system includes a first electro-hydraulic proportional overflow valve and a first pressure sensor, one end of which is connected to the outlet of the first pressure medium source. The other end of the first electro-hydraulic proportional overflow valve is connected to one end of a first reversing valve, and the other end of the first reversing valve is connected to the first interface. The first electro-hydraulic proportional overflow valve is also electrically connected to a first signal amplifier. The first signal amplifier, the first pressure sensor are in signal connection with an external controller, and the controller is electrically connected to a power supply through a control switch.

[0024] In the present invention, a pressure medium is injected into or discharged from the first pressure chamber through the first pressure control component, and a pressure medium is injected into or discharged from the second pressure chamber through the second pressure control component. The pressure difference between the first pressure chamber and the second pressure chamber is controlled according to the load condition to push the piston to reciprocate. Through the cooperation of the spiral chute opened on the second opening sleeve and the second connecting piece, when the driving lead screw reverses, an additional rotation at a required arbitrary angle can be generated instantaneously, so that the bidirectional backlash-free transmission of the single-nut lead screw transmission pair can be realized, the backlash in the single-nut lead screw pair transmission is eliminated. At the same time, the hydraulic pressure inside the piston can be adjusted at any time according to the load change condition to ensure the rigidity during transmission.

[0025] Compared with the prior art, a hydraulic backlash-eliminating coupling with automatic pressure adjustment provided by the present invention has the following beneficial effects:

[0026] 1. The present invention can completely eliminate the reverse transmission backlash at any reverse point and any value. If combined with the pitch error compensation function of the numerical control system, the use accuracy of the single-nut lead screw of the ordinary precision grade can be greatly improved.

[0027] 2. The pressure difference between the first pressure chamber and the second pressure chamber of the present invention can be pre-tension adjusted and real-time adjusted according to the load condition through the control system, so as to reduce the wear during the use of the lead screw nut pair and increase the service life of the lead screw nut pair.

[0028] 3. The present invention can greatly improve the transmission accuracy of the system, has good transmission rigidity and strong practicability, and is worthy of popularization and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic structural diagram of the present invention;

[0030] Figure 2 is the C-C cross-sectional view of the present invention;

[0031] Figure 3 is the D-D cross-sectional view of the present invention;

[0032] Figure 4 is the E-E cross-sectional view of the present invention;

[0033] Figure 5 is the F-F cross-sectional view of the present invention;

[0034] Figure 6 is the G-G cross-sectional view of the present invention;

[0035] Figure 7 is the usage state of the present invention Figure 1 ;

[0036] Figure 8 is the usage state of the present invention Figure 2 .

[0037] Description of reference numerals:

[0038] 1. First connection end; 2. First opening sleeve; 3. Housing; 4. First flat thrust bearing; 5. First connecting member; 6. First seal; 7. Second seal; 8. Fourth seal; 9. First end cover; 10. Piston; 11. Second flat thrust bearing; 12. Third seal; 13. Second end cover; 14. Second connecting member; 15. Second opening sleeve; 16. Third connecting member; 17. Second connection end; 18. First interface; 19. Second interface; 20. Straight chute. Detailed implementation manners

[0039] Next, in combination with the Figures 1 to 8 accompanying drawings, a specific implementation manner of the present invention will be described in detail, but it should be understood that the protection scope of the present invention is not limited by the specific implementation manner.

[0040] Embodiment 1

[0041] As Figure 1 shown, a hydraulically self-adjusting backlash coupling includes a housing 3. A cavity is formed on one end face of the housing 3, and the cross-section of the cavity is stepped. A first opening sleeve 2 is inserted into the stepped cavity, and the first opening sleeve 2 is connected to the housing 3 in a limit manner through a clamping structure.

[0042] Specifically, the clamping structure includes a ring-shaped protrusion provided at one end of the first opening sleeve 2, and the ring-shaped protrusion is clamped on a stepped groove formed in the housing 3, so that the first opening sleeve 2 realizes unidirectional axial limitation.

[0043] A piston 10 is also inserted into the first open sleeve 2 . The piston 10 is connected to the first open sleeve 2 via a guide transmission structure. A first pressure chamber is formed between the piston 10 and the first open sleeve 2 .

[0044] Specifically, the guide transmission structure includes a circular boss formed on the end face of the piston 10, an outer spline is formed on the outer circumference of the circular boss, the outer spline is meshed and transmission-connected with the inner spline on the first open sleeve 2, and the inner spline is formed in a groove on the first open sleeve 2. The meshing of the outer spline and the inner spline can realize the transmission of the circumferential rotation force on the first open sleeve 2 and the piston 10, and can also allow the axial displacement of the first open sleeve 2 and the piston 10.

[0045] In addition, a first end cover 9 is mounted on the piston 10 , the first end cover 9 is inserted into the cavity and fixedly connected to the first opening sleeve 2 by screws, and a second pressure chamber is formed between the piston 10 and the first end cover 9 .

[0046] like Figure 1 and Figure 6 As shown, a second open sleeve 15 is sleeved on the end of the piston 10 away from the first open sleeve 2, and a spiral groove is opened on the second open sleeve 15, the cross-section of the spiral groove is preferably trapezoidal, and a second connecting member 14 is passed through the spiral groove, and the second connecting member 14 is fixedly connected to the piston 10.

[0047] Preferably, the second connecting member 14 is a pin, and the cross section of the pin is a trapezoid that matches the cross section of the spiral slide groove. The trapezoid is larger at the top and smaller at the bottom, which facilitates the insertion of the second connecting member 14.

[0048] Among them, the first open sleeve 2, the piston 10, the first end cover 9 and the shell 3 constitute the main structure of the rotary cylinder, and the second connecting member 14 can move in the spiral groove. The cooperation between the spiral groove and the second connecting member 14 is used to convert the linear movement of the piston 10 into the rotation of the rotary cylinder, providing a required additional rotation at any angle.

[0049] A second end cover 13 is mounted on the piston 10 and is fixedly connected to the housing 3 to achieve sealing of the overall structure.

[0050] Furthermore, the first pressure chamber is connected to a first pressure control assembly, which is used to inject or discharge pressure medium into or out of the first pressure chamber to push the piston 10 to move left and right. The second pressure chamber is connected to a second pressure control assembly, which is used to inject or discharge pressure medium into or out of the second pressure chamber. The pressure medium is injected into or discharged from the first pressure chamber through the first pressure control assembly, and the pressure medium is injected into or discharged from the second pressure chamber through the second pressure control assembly to control the pressure difference between the first pressure chamber and the second pressure chamber to push the piston 10 to move left and right.

[0051] Preferably, a first flat thrust bearing 4 for ensuring smooth relative rotation is further provided between the annular boss and the stepped groove, and a second flat thrust bearing 11 for ensuring smooth relative rotation is provided between the first end cover 9 and the second end cover 13. The second flat thrust bearing 11 is sleeved on the second opening sleeve 15.

[0052] Preferably, as Figure 1 and Figure 3 shown, two first seals 6 are provided between the first opening sleeve 2 and the housing 3, and the two first seals 6 are arranged at intervals. A second seal 7 is provided between the first opening sleeve 2 and the piston 10, a third seal 12 is provided between the piston 10 and the first end cover 9, and a fourth seal 8 is provided between the first opening sleeve 2 and the first end cover 9. The first seal 6, the second seal 7 and the third seal 12 can all preferably be sealing rubber rings, and the fourth seal 8 is preferably a non-metallic sealing gasket. The use of the first seal 6, the second seal 7, the third seal 12 and the fourth seal 8 makes the airtightness of the device good.

[0053] Preferably, the first pressure control assembly and the second pressure control assembly have the same structure.

[0054] Preferably, the structure of the first pressure control assembly includes a first channel opened on the housing 3, one end of the first channel communicates with the first pressure chamber, as Figure 4 shown, the other end is provided with a first interface 18, the first interface 18 communicates with an external first pressure medium source, and a first pressure adjustment system for adjusting the pressure of the medium in the first pressure chamber is provided between the first pressure medium source and the first interface 18. The specific structure of the first pressure adjustment system includes a first electro-hydraulic proportional relief valve and a first pressure sensor connected to the outlet of the first pressure medium source at one end. The other end of the first electro-hydraulic proportional relief valve is connected to one end of a first reversing valve, the other end of the first reversing valve is connected to the first interface 18, the first electro-hydraulic proportional relief valve is also electrically connected to a first signal amplifier, and the first signal amplifier and the first pressure sensor are in signal connection with an external controller. The controller is electrically connected to a power supply through a control switch.

[0055] Preferably, the structure of the second pressure control assembly includes a second channel opened on the housing 3, one end of the second channel communicates with the second pressure chamber, as Figure 5As shown, a second interface 19 is provided at the other end. The second interface 19 is connected to a second pressure medium source of a peripheral device. A second pressure adjustment system for adjusting the pressure of the medium in the second pressure chamber is provided between the second pressure medium source and the second interface 19. The specific structure of the second pressure adjustment system includes a second electro-hydraulic proportional overflow valve and a second pressure sensor, with one end of the second electro-hydraulic proportional overflow valve connected to the outlet of the second pressure medium source. The other end of the second electro-hydraulic proportional overflow valve is connected to one end of a second reversing valve, and the other end of the second reversing valve is connected to the second interface 19. The second electro-hydraulic proportional overflow valve is also electrically connected to a second signal amplifier, and the second signal amplifier and the second pressure sensor are signal-connected to a controller of the peripheral device.

[0056] As the first alternative to the above solution, the external spline can be replaced by a straight-tooth external gear, and the internal spline can be replaced by a straight-tooth internal gear. This can also achieve the transmission of the circumferential rotational force on the first split sleeve 2 and the piston 10, and at the same time allow a small amount of axial displacement of the first split sleeve 2 and the piston 10.

[0057] As the second alternative to the above solution, as Figure 8 shown, the straight-tooth external gear is replaced by a helical external gear, the straight-tooth internal gear is replaced by a helical internal gear, and the spiral chute is replaced by a straight chute 20. This can also achieve the transmission of the circumferential rotational force on the first split sleeve 2 and the piston 10, and at the same time allow a small amount of axial displacement of the first split sleeve 2 and the piston 10.

[0058] Taking the hydraulic backlash eliminator coupling installed between the ball screw and the servo motor of the Z-axis of a CNC lathe as an example, the working principle of the present invention will be further described below.

[0059] A hydraulic backlash eliminator coupling with automatic pressure adjustment, the mechanical structure part of which includes:

[0060] A first split sleeve 2, a housing 3, a first end cover 9, a first flat thrust bearing 4, a piston 10, a second end cover 13, a second connecting member 14 and a second split sleeve 15.

[0061] Among them, as Figure 7 shown, the first split sleeve 2 is used to connect to the first connection end 1. As shown in the C-C sectional view shown in Figure 2 , the first connection end 1 is inserted into the first split sleeve 2. When the first connecting member 5 is tightened, the fixed connection between the first split sleeve 2 and the first connection end 1 can be achieved through the first connecting member 5.

[0062] Among them, the first split sleeve 2, the piston 10, the first end cover 9, the housing 3 and the structure constitute the main structure of the rotary cylinder. The first split sleeve 2 acts as the cylinder block of the rotary cylinder in the device structure.

[0063] Among them, the second connection end 17 is inserted into the second opening sleeve 15 and connected to the second connection end 17 through a third connecting member 16. Specifically, the third connecting member 16 is preferably a connecting bolt.

[0064] The first opening sleeve 2 is sleeved on the screw shaft end 1 and can be fixedly connected to the outer circle of the screw shaft end 1 through a first connecting member 5. The second connecting member 14 is arranged on the piston 10. The second opening sleeve 15 with a spiral chute is fixedly connected to the second connection end 17. The spiral chute penetrates the inner and outer surfaces of the second opening sleeve 15.

[0065] Specifically, the first connecting member 5 is preferably a bolt or other standard fasteners.

[0066] By injecting pressure media with different pressures on both sides of the piston 10, the piston 10 is pushed to reciprocate. Through the non-gap sliding of the second connecting member 14 fixedly connected to the piston 10 along the spiral chute on the second opening sleeve 15, a relative rotation is generated between the driving shaft and the driven shaft, and finally the purpose of eliminating the backlash during single-nut screw drive is achieved. In addition, by controlling the basic hydraulic pressure of the coupling, the pre-tension of the screw can be controlled and adjusted, the service life of the screw can be extended, and the transmission accuracy and service life of the single-nut screw pair can be improved.

[0067] The hydraulic backlash-eliminating coupling, its electrical control part includes:

[0068] The first pressure control component and the second pressure control component have the same structure. The structure of the first pressure control component includes a first channel opened on the housing 3. One end of the first channel is communicated with the first pressure chamber, and the other end is provided with a first interface 18. The first interface 18 is communicated with an external first pressure medium source. A first pressure adjustment system for adjusting the pressure of the medium in the first pressure chamber is arranged between the first pressure medium source and the first interface 18. The specific structure of the first pressure adjustment system includes a first electro-hydraulic proportional relief valve and a first pressure sensor connected to the outlet of the first pressure medium source at one end. The other end of the first electro-hydraulic proportional relief valve is connected to one end of a first reversing valve. The other end of the first reversing valve is connected to the first interface 18. The first electro-hydraulic proportional relief valve is also electrically connected to a first signal amplifier. The first signal amplifier and the first pressure sensor are signal-connected to an external controller. The controller is electrically connected to the power supply through a control switch.

[0069] Preferably, the structure of the second pressure control component includes a second channel formed in the housing 3. One end of the second channel communicates with the second pressure chamber, and the other end is provided with a second interface 19. The second interface 19 communicates with an external second pressure medium source, and a second pressure adjustment system for adjusting the pressure of the medium in the second pressure chamber is provided between the second pressure medium source and the second interface 19. The specific structure of the second pressure adjustment system includes a second electro-hydraulic proportional overflow valve and a second pressure sensor with one end connected to the outlet of the second pressure medium source. The other end of the second electro-hydraulic proportional overflow valve is connected to one end of the second reversing valve, and the other end of the second reversing valve is connected to the second interface 19. The second electro-hydraulic proportional overflow valve is also electrically connected to a second signal amplifier, and the second signal amplifier and the second pressure sensor are signal-connected to an external controller.

[0070] Working principle of the present invention:

[0071] As Figure 1 shown, install the hydraulic backlash eliminator coupling in the present invention at the installation position of the original coupling, and then use the first connecting member 5 and the third connecting member 16 to fix the second split sleeve 15 and the first split sleeve 2 to the servo motor shaft end and the lead screw shaft end respectively; then, inject hydraulic oil with different pressures into the first pressure chamber and the second pressure chamber at both ends of the piston 10 through the pressure medium injection / discharge from the first interface 18 or the second interface 19. The hydraulic backlash eliminator coupling will drive the lead screw to rotate by an angle, so that the driving side of the lead screw raceway pushes the ball to closely abut against the driven side of the nut raceway without clearance; when the servo motor drives the lead screw to rotate in the reverse direction, first, when the servo motor decelerates to a stop, the servo motor will maintain this stop state under the action of the machine tool numerical control system, and at the same time, the control system will send a reverse rotation signal to the servo motor, and the control system of the coupling will also receive this reverse rotation signal at the same time. This reverse rotation signal can control the electro-hydraulic proportional reversing overflow valve to complete all actions of switching the coupling from pressure to driving the lead screw to rotate by a certain angle within dozens of milliseconds; since the servo motor is in a relatively stationary state under the action of the "enable" (allowing rotation / holding) signal of the machine tool numerical control system at this time, the relative rotation at both ends of the hydraulic backlash eliminator coupling can only be the rotation of the lead screw shaft. Once the control system of the electrical part of the hydraulic backlash eliminator coupling receives the reverse rotation signal, it will immediately switch the pressure, making the above-mentioned low-pressure end become the high-pressure end, thereby pushing the piston 10 and the second connecting member 14 to slide along the spiral chute on the second split sleeve 15, causing the lead screw shaft to rotate relative to the stationary motor shaft, and making the driving side of the lead screw raceway push the ball to closely abut against the driven side of the nut raceway without clearance. Once the above-mentioned raceway and ball are in non-clearance contact, it will generate a movement resistance to the rotation of the lead screw, causing the hydraulic pressure pushing the piston to increase, triggering a control signal, closing the oil inlet hole (or making the hydraulic pressures on both sides of the piston the same), and the lead screw shaft stops rotating and remains in this position unchanged. From Figure 7It can be seen that at this time, if the drive motor drives the lead screw to rotate clockwise, when the raceway cross-section shown in Figure 7 moves to the left, the lead screw raceway pushes the nut to move leftward simultaneously through the balls, which is a backlash-free transmission; when the lead screw moves in the reverse direction, within a tiny time period of dozens of milliseconds before the motor drives the lead screw to rotate counterclockwise and makes the raceway cross-section shown in Figure 7 move to the right, the first pressure control component and the second pressure control component are used to adjust the pressures on both sides of the piston 10, and the piston 10 will push the lead screw to rotate counterclockwise. The lead screw pushes the balls along the spiral raceway of the lead screw towards Figure 7 the right side of the lead screw raceway in until they are tightly against the right side of the lead screw raceway. At this time, the motor has not started to rotate counterclockwise and is in the feed hold (rotation lock) stage. At this time, as long as the moving distance of the lead screw raceway caused by the rotation angle of the lead screw brought about by the movement stroke of the piston does not exceed the backlash, the position of the moving part (workbench) will not change, and at this time, the lead screw raceway, the balls, and the nut raceway are kept in close contact; therefore, if the drive motor starts to drive the lead screw to rotate counterclockwise and makes the raceway cross-section shown in Figure 7 move to the right, the lead screw raceway directly pushes the nut to move rightward simultaneously through the balls, which is also a backlash-free transmission.

[0072] As can be seen from the above, as long as the lead screw commutation is completed first through hydraulic drive within the time period of dozens of milliseconds when the lead screw rotates and changes direction, it can be ensured that the transmission of the single-nut lead screw pair is a transmission without reverse backlash; at this time, the lead screw has not started to drive the nut to move, so the relative position of the transmission pair remains unchanged. Also, when the ball screw drives the nut to be in a state of continuous movement in a certain direction, since the piston's entry / exit from the first interface 18 or the second interface 19 is in a closed state, when the moving load changes and causes the forces on both sides of the piston to be unbalanced, the hydraulic media sealed on both sides of the piston will generate opposite acting forces to restore the balance state at both ends of the piston.

[0073] Through the following calculations, it can be verified whether the feasibility conclusion of this implementation plan is correct.

[0074] According to Newton's second law, F = ma. Similarly

[0075] Mn = ε * I = Ft * 2R (1)

[0076] Then ε = Ft * 2R / I (2)

[0077] In the above formula, Mn is the torque that drives the lead screw to rotate when the hydraulic pressure drives the tapered pin to move in the spiral chute;

[0078] ε is the angular acceleration when the lead screw and the coupling fixedly connected to it perform backlash elimination rotation;

[0079] I is the moment of inertia during the backlash elimination rotation of the lead screw (including the coupling).

[0080] I = (m1 * r1² + m2 * r2²) / 2 (3)

[0081] m1 is the total mass of the lead screw during rotation;

[0082] m2 is the mass of the coupling moving together;

[0083] r1 is the radius of rotation of the lead screw;

[0084] r2 is the radius of rotation of the coupling;

[0085] The driving force F that drives the tapered pin to move along the helix direction of the spiral chute can be decomposed into an axial component force Fr and a circumferential component force Ft. When the two tapered pins are evenly stressed

[0086] Fr = p * S / 2 (4)

[0087] Ft = Mn / 2R; (5)

[0088] Ft / Fr = tanθ; (6)

[0089] Among them,

[0090] p is the pressure difference of the pressure medium acting on both ends of the piston;

[0091] S is the piston area acted on by the pressure medium:

[0092] θ is the helix angle of the spiral chute;

[0093] R is the radius of the force application point of the tapered pin driving the lead screw to rotate in contact with the chute;

[0094] According to Newton's kinematic law, the angular velocity and rotation angle of the rotating body have the following relationship:

[0095] ω = ε * t

[0096]

[0097] Among them,

[0098] φ is the angle that the lead screw needs to rotate during backlash elimination rotation;

[0099] ε is the angular acceleration of the lead screw during backlash elimination rotation;

[0100] T is the time taken for the lead screw to eliminate backlash rotation;

[0101] Assume that the backlash at the reverse point of the lead screw is ΔL, and the angle that the lead screw needs to rotate to eliminate ΔL is φ. Then, according to the similarity triangle theorem, the following equation holds:

[0102] ΔL / φ = h / 2π (8)

[0103] Then φ = ΔL * 2π / h (9)

[0104] Wherein,

[0105] h is the lead of the lead screw;

[0106] ε is the angular acceleration when the lead screw performs backlash elimination rotation;

[0107] T is the time taken for the lead screw to perform backlash elimination rotation;

[0108] As can be seen from the above formula, when the influence of motion resistance is not considered,

[0109]

[0110] If ΔL = 0.1 mm (when the test lead screw (model 4016, nominal diameter 40 mm, lead 16 mm,, length 1000 mm) is assembled, the factory clearance is 0.1 mm, the mass of the lead screw is 10 kg), the radius of gyration of the coupling tapered pin is 20 mm, the total mass of the coupling is 0.6 kg, the piston force area S = 1.0446 * 10-3 m 2 , and the spiral angle of the spiral chute is taken as 4° less than the sliding self-locking angle.

[0111] As can be seen from formula (10):

[0112]

[0113] That is, when the pressure difference between the two ends of the piston is 0.25 MPa, T = 67.2 ms.

[0114] It should be noted that this result does not consider the frictional resistance during the rotation of the lead screw and the switching frequency of the hydraulic valve.

[0115] Currently, the pressure of the hydraulic stations with standard configurations of CNC machine tools using ball screw drive pairs can reach above 3.5 MPa, the reverse startup time is about 50 - 100 ms, the highest known action frequency of the reversing valve is 120 Hz, that is, about 8.3 ms, then T = 75.5 ms.

[0116] Therefore, from the results of the above simple calculations, it can be seen that the application of the product of the present invention on lead screws with a nominal diameter of the lead screw less than or equal to 40 mm and a length less than 1000 mm is feasible.

[0117] As can be seen from formula (10), when the coupling is used for lead screw products of other specifications, since the time taken for backlash elimination rotation is inversely proportional to the piston area and the pressure of the pressure medium, the maximum time requirement for backlash elimination rotation can be met by appropriately adjusting the piston area of the hydraulic backlash elimination coupling and the oil supply pressure of the hydraulic oil.

[0118] In addition, it can also be known from formula (10) that the hydraulic pressure required for the backlash elimination movement of the driving nut is directly proportional to the nut mass, inversely proportional to the pressure medium acting area on the piston, and inversely proportional to the square of the time t required for the nut backlash elimination movement.

[0119] The time taken for backlash elimination of the coupling can be controlled within 50 - 100 ms. Therefore, during the reverse process of the lead screw, there will be no machining errors caused by the nut stagnation during the reverse of the lead screw due to reverse clearance.

[0120] In addition, from Figure 1 and Figure 7 it can be seen that when the coupling drives the lead screw to rotate, even if the pressure sensor fails to close the oil supply pipeline in time, as long as the stroke end point of the coupling piston is controlled, the rotation of the lead screw will stop. Therefore, as long as the parameters of the coupling are appropriately adjusted and the piston area is increased so that the time required for backlash elimination rotation is less than 50 ms, the stroke of the piston can be controlled by adjusting the mechanical structure to achieve the purpose of eliminating the reverse clearance of the single-nut ball screw. The transmission of the lead screw driving force is finally transmitted to the load through the lead screw raceway - ball - nut raceway.

[0121] In addition, since the product of the present invention uses the change in the pressure values of the pressure media on both sides of the piston to control the lead screw to perform backlash elimination movement, when a new pitch error occurs due to the length change of the lead screw during operation due to temperature influence, the hydraulic system can also automatically compensate. Therefore, there is no need to perform pre-tensioning work on the lead screw.

[0122] In addition, when it is necessary to adapt to the occasions of inclined shafts or vertical shafts, the force-bearing areas on both sides of the piston 10 of the hydraulic backlash elimination coupling provided by the present invention can be different.

[0123] Compared with the prior art, a hydraulically actuated backlash eliminator with automatic pressure regulation provided by the present invention can push the piston to reciprocate by adjusting the pressure difference between the pressure media injected into both sides of the piston in the rotary cylinder fixedly connected to the lead screw, and drive the lead screw to instantaneously generate an additional rotation at a required arbitrary angle during reverse rotation through the pin shaft fixed at the end of the piston and the chute on the outer ring of the sliding sleeve of the coupling fixedly connected to the motor shaft. Thus, a two-way non-backlash transmission of the single-nut lead screw transmission pair can be realized, the reverse clearance in the transmission of the single-nut lead screw pair is eliminated, and it has high practicability and is worthy of popularization.

[0124] The above only discloses several specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any changes that can be thought of by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A hydraulic backlash eliminator coupling with automatic pressure regulation, characterized in that Comprising: A housing (3) with a cavity formed therein; A first open sleeve (2) inserted into the cavity and limitedly connected to the housing (3) through a clamping structure; A piston (10) inserted into the first open sleeve (2) and connected to the first open sleeve (2) through a guiding transmission structure, a first pressure chamber being formed between the piston (10) and the first open sleeve (2); A first end cap (9) inserted into the cavity, sleeved on the piston (10), and fixedly connected to the first open sleeve (2), a second pressure chamber being formed between the first end cap (9) and the piston (10); A second open sleeve (15) sleeved on the piston (10), a spiral chute being formed in the second open sleeve (15), a second connecting member (14) being inserted through the spiral chute and fixedly connected to the piston (10); A second end cap (13) sleeved on the piston (10) and fixedly connected to the housing (3); A first pressure control assembly and a second pressure control assembly, respectively communicating with the first pressure chamber and the second pressure chamber, for injecting a pressure medium into the first pressure chamber or the second pressure chamber to push the piston (10) to move; The guiding transmission structure includes: A circular boss formed on the end face of the piston (10), an external spline being formed on the outer circumference of the circular boss, the external spline meshing with an internal spline formed in a groove of the first open sleeve (2); The clamping structure includes an annular boss provided at one end of the first open sleeve (2), the annular boss being clamped in a step groove formed in the housing (3).

2. The hydraulic backlash eliminator coupling with automatic pressure regulation according to claim 1, wherein, The external spline is replaced by a straight-tooth external gear, and the internal spline is replaced by a straight-tooth internal gear.

3. The hydraulic backlash eliminator coupling with automatic pressure regulation according to claim 2, wherein, A first flat thrust bearing (4) is further provided between the annular boss and the step groove, a second flat thrust bearing (11) is provided between the first end cap (9) and the second end cap (13), and the second flat thrust bearing (11) is sleeved on the second open sleeve (15).

4. The hydraulic backlash eliminator coupling with automatic pressure regulation according to claim 1, characterized in that, At least one first seal (6) is provided between the first open sleeve (2) and the housing (3), a second seal (7) is provided between the first open sleeve (2) and the piston (10), a third seal (12) is provided between the piston (10) and the first end cap (9), and a fourth seal (8) is provided between the first open sleeve (2) and the first end cap (9).

5. The hydraulic backlash-eliminating coupling with automatic pressure regulation according to claim 1, characterized in that, The first pressure control assembly and the second pressure control assembly have the same structure.

6. The hydraulic backlash-eliminating coupling with automatic pressure regulation according to claim 5, characterized in that, The first pressure control assembly includes a first channel formed in the housing (3), one end of the first channel communicating with the first pressure chamber, the other end being provided with a first interface (18), the first interface (18) communicating with an external first pressure medium source, and a first pressure adjustment system for adjusting the pressure of the medium in the first pressure chamber is provided between the first pressure medium source and the first interface (18).

7. The hydraulic backlash-eliminating coupling with automatic pressure regulation according to claim 6, characterized in that, The first pressure adjustment system includes a first electro-hydraulic proportional overflow valve and a first pressure sensor, with one end of the first electro-hydraulic proportional overflow valve connected to the outlet of the first pressure medium source. The other end of the first electro-hydraulic proportional overflow valve is connected to one end of the first reversing valve, and the other end of the first reversing valve is connected to the first interface (18). The first electro-hydraulic proportional overflow valve is also electrically connected to a first signal amplifier. The first signal amplifier and the first pressure sensor are in signal connection with an external controller, and the controller is electrically connected to a power supply through a control switch.

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