Nut tightening tool and nut tightening method

Abstract

The invention relates to the technical field of power-assisted shafts, and provides a nut tightening tool and a nut tightening method for tightening a bearing locking nut of a power-assisted shaft. A worm gear is fixedly sleeved on the boosting shaft, the worm gear is accommodated in a shell, and a bearing for rotatably supporting the boosting shaft and the worm gear is assembled in the shell; the nut tightening tool comprises a bearing mechanism used for positioning and supporting a shell; the gravity pressing mechanism is used for pressing the shell and the worm gear; the jacking and screwing mechanism comprises a liftable jacking rod and a screwing sleeve rotationally screwed outside the jacking rod, the jacking rod is used for jacking the power-assisted shaft, a pressure measuring element is arranged at the end of the jacking rod, and an assembling groove for assembling the bearing locking nut is formed in the end of the screwing sleeve. The bearing locking nut can be accurately screwed in place, so that the bearing meets the rigidity requirements that the axial clearance is eliminated and the axial displacement is in a proper interval under the action of a certain axial force, the yield is improved, the operation is simple, convenient and efficient, and the production efficiency can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of power-assist shafts, in particular to a nut tightening tool and a nut tightening method for tightening a bearing locking nut of a power-assist shaft. Background Art

[0002] The power-assist shaft is an important part of the steering system, and the bearing is used to rotatably support the power-assist shaft. The bearing is axially locked by the locking nut to ensure that the power-assist shaft rotates smoothly and reliably, so that the steering system can operate stably and reliably.

[0003] How to tighten the locking nut into place so that the bearing can meet the stiffness requirements of eliminating axial clearance and keeping the axial displacement within an appropriate range under a certain axial force is currently a very challenging problem.

[0004] The current nut tightening equipment generally has the problem of being unable to accurately tighten the locking nut. It is easy to fail to tighten it into place and fail to eliminate the axial clearance of the bearing, or over-tighten it and consume the axial displacement that the bearing should retain. In addition, the current nut tightening equipment is time-consuming to operate and has low efficiency.

[0005] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0006] In view of this, the present invention provides a nut tightening tool and a nut tightening method for tightening the bearing locking nut of the power-assisting shaft, which can accurately screw the bearing locking nut into place so that the axial clearance of the bearing is eliminated and the axial displacement is in a suitable range under the action of a certain axial force. The stiffness requirement improves the yield rate. The nut tightening tool and the nut tightening method of the present invention are simple and efficient to operate, and can improve production efficiency.

[0007] One aspect of the present invention provides a nut tightening tool for tightening the bearing locking nut of a power-assisting shaft, wherein a worm gear is fixedly mounted on the power-assisting shaft, and the worm gear is accommodated in a shell, and a bearing for rotatably supporting the power-assisting shaft and the worm gear is assembled in the shell; the nut tightening tool comprises: a bearing mechanism for positioning and supporting the shell; a gravity pressing mechanism for pressing the shell and the worm gear; a lifting and screwing mechanism, comprising a lifting rod that can be raised and lowered and a screwing sleeve that is rotatably screwed to the outside of the lifting rod, the lifting rod is used to tighten the power-assisting shaft, a pressure measuring element is arranged at the end of the lifting rod, and an assembly groove for assembling the bearing locking nut is arranged at the end of the screwing sleeve.

[0008] In some embodiments, the bearing mechanism includes: a bearing seat, which is provided with a through hole for the lifting rod and the screw sleeve to pass through; a plurality of support seats, which are fixed to the bearing seat and respectively matched with a plurality of positioning holes of the shell; and a calibrator, which is distributed around the bearing seat.

[0009] In some embodiments, the gravity pressing mechanism includes: an annular pressure head, which is adapted to the end face of the shell; a downward pressing cylinder, connected to the annular pressure head, and used to drive the annular pressure head to press down; a self-weight pressure rod, including a counterweight block and a pressure rod connected to the counterweight block, the lower end face of the pressure rod extending out of the annular pressure head and being unidirectionally limited to the annular pressure head; as the annular pressure head is pressed against the end face of the shell, the self-weight pressure rod presses against the upper end face of the worm gear with its own weight.

[0010] In some embodiments, the lifting and screwing mechanism further includes: a lifting motor connected to the lifting rod, used to drive the lifting rod to rise and fall; wherein, the end of the lifting rod is provided with an internal spline that is compatible with the external spline of the end of the power-assisting shaft.

[0011] In some embodiments, the lifting and screwing mechanism further includes: a rotary motor connected to the screwing sleeve and used to drive the screwing sleeve to rotate.

[0012] In some embodiments, the bearing includes: an upper bearing, the end face of the outer ring of the upper bearing is supported on the shoulder of the housing, the upper end face of the inner ring of the upper bearing abuts the lower end face of the worm gear, and the inner ring of the upper bearing is interference fit with the power-assist shaft; a lower bearing, the end face of the outer ring of the lower bearing is supported on the shoulder of the housing, and the inner ring of the lower bearing is slidingly fit with the power-assist shaft; as the bearing locking nut tightens the lower end face of the inner ring of the lower bearing, the inner ring of the lower bearing and the inner ring of the upper bearing move up and down successively to eliminate the axial clearance of the lower bearing and the axial clearance of the upper bearing respectively, and the pressure measuring element detects the force of the bearing locking nut on the upper bearing.

[0013] Another aspect of the present invention provides a nut tightening method, based on the nut tightening tool as described in any of the above embodiments to tighten the bearing locking nut of the power-assisting shaft, the nut tightening method includes: positioning the housing on the bearing mechanism, driving the gravity clamping mechanism and the lifting rod to extend in sequence, so that the gravity clamping mechanism presses the housing and the worm gear, and the lifting rod presses the power-assisting shaft; driving the screwing sleeve to rotate, so that the bearing locking nut is screwed onto the power-assisting shaft and presses the inner ring of the bearing; wherein, during the process of driving the screwing sleeve to rotate, the pressure measuring element detects a preset force and stops the screwing sleeve.

[0014] In some embodiments, the preset force is determined according to the force required to eliminate the axial clearance of the bearing and the response time of the lifting and screwing mechanism.

[0015] In some embodiments, the bearing includes an upper bearing and a lower bearing, the end face of the outer ring of the upper bearing is supported on the shoulder of the housing, the upper end face of the inner ring of the upper bearing abuts the lower end face of the worm gear, the inner ring of the upper bearing is interference fit with the power-assist shaft, the end face of the outer ring of the lower bearing is supported on the shoulder of the housing, and the inner ring of the lower bearing is slidingly fit with the power-assist shaft; in the process of driving the screw sleeve to rotate, the first clearance elimination stage and the second clearance elimination stage are successively performed through the bearing locking nut; in the first clearance elimination stage, the bearing locking nut lifts the inner ring of the lower bearing, so that the inner ring of the lower bearing moves up to eliminate the axial clearance of the lower bearing; in the second clearance elimination stage, the bearing locking nut pulls down the inner ring of the upper bearing through the power-assist shaft, so that the inner ring of the upper bearing moves down to eliminate the axial clearance of the upper bearing, and the pressure measuring element detects the force of the bearing locking nut on the upper bearing.

[0016] In some embodiments, the nut tightening method also includes: driving the lifting rod to retract; driving the lifting rod to extend, and measuring the axial displacement of the bearing when the difference between the lifting force of the lifting rod and the downward pressure of the gravity clamping mechanism reaches a preset negative value and a preset positive value respectively; determining whether the bearing meets the standards based on the sum of the two measured axial displacements.

[0017] The beneficial effects of the present invention compared with the prior art include at least:

[0018] The nut tightening tool and nut tightening method of the present invention can stably and reliably position and support the power-assisting shaft through the cooperation of the bearing mechanism, the gravity pressing mechanism and the jacking rod, so that the power-assisting shaft remains stable during the nut tightening process; through the ingenious cooperation of the jacking rod and the screwing sleeve, after the jacking rod tightens the power-assisting shaft, the screwing sleeve is driven to rotate, so that the screwing sleeve drives the bearing locking nut to be screwed onto the power-assisting shaft; in addition, through the pressure measuring element arranged at the end of the jacking rod, in the process of driving the screwing sleeve to rotate, the pressure measuring element detects the force of the bearing locking nut acting on the power-assisting shaft and the bearing and then feeding back to the jacking rod, so as to monitor the force of the bearing locking nut on the bearing, and ensure that the bearing locking nut is accurately screwed into place;

[0019] Therefore, the nut tightening tool and nut tightening method of the present invention can accurately screw the bearing locking nut into place, so that the bearing meets the stiffness requirements that the axial clearance is eliminated and the axial displacement is in a suitable range under the action of a certain axial force, thereby improving the yield rate. The nut tightening tool and nut tightening method of the present invention are simple and efficient to operate, and can improve production efficiency.

[0020] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings herein are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present invention, and together with the specification are used to explain the principles of the present invention. Obviously, the accompanying drawings described below are only some embodiments of the present invention, and for those of ordinary skill in the art, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0022] Figure 1 A schematic structural diagram of a power assist shaft in an embodiment of the present invention is shown;

[0023] Figure 2 A schematic structural diagram of a nut tightening tool according to an embodiment of the present invention is shown;

[0024] Figure 3 A schematic structural diagram of a lifting and screwing mechanism in an embodiment of the present invention is shown;

[0025] Figure 4 A schematic structural diagram of a bearing mechanism in an embodiment of the present invention is shown;

[0026] Figure 5 A schematic diagram showing the structure of a gravity pressing mechanism in an embodiment of the present invention is shown;

[0027] Figure 6 A schematic diagram showing the steps of a nut tightening method in an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0028] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the embodiments set forth herein. Instead, these embodiments are provided to make the present invention comprehensive and complete and to fully convey the concepts of the example embodiments to those skilled in the art.

[0029] The accompanying drawings are only schematic illustrations of the present invention and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and their repeated description will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software form, or in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0030] The processes shown in the accompanying drawings are only exemplary and do not necessarily include all the steps. For example, some steps may be decomposed, some steps may be combined or partially combined, and the actual execution order may change according to the actual situation. The words "first", "second" and similar words used in the specific description do not indicate any order, quantity or importance, but are only used to distinguish different components.

[0031] In addition, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "up", "down", "rise", "fall", etc. are based on the directions 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 direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0032] It should be noted that, in the absence of conflict, the embodiments of the present invention and features in different embodiments may be combined with each other.

[0033] Figure 1 Shows the structure of the booster shaft; Figure 1 As shown, a worm gear 11 is fixedly mounted on the power-assist shaft 10 , and the worm gear 11 is accommodated in a housing 12 , in which a bearing 15 for rotatably supporting the power-assist shaft 10 and the worm gear 11 is assembled.

[0034] Figure 2 The structure of the nut tightening tool is shown. Figure 3 Shows the structure of the lifting and screwing mechanism; combined Figures 1 to 3 As shown, the nut tightening tool for tightening the bearing locking nut 16 of the power assist shaft 10 provided in the embodiment of the present invention includes:

[0035] A bearing mechanism 20, used for positioning and supporting the housing 12;

[0036] A gravity pressing mechanism 30, used for pressing the housing 12 and the worm gear 11;

[0037] The lifting and screwing mechanism 40 includes a lifting rod 42 that can be raised and lowered and a screwing sleeve 44 that is rotatably screwed to the outside of the lifting rod 42. The lifting rod 42 is used to tighten the power-assisting shaft 10. A pressure measuring element (not specifically shown in the figure) is provided at the end of the lifting rod 42. An assembly groove for assembling the bearing locking nut 16 is provided at the end of the screwing sleeve 44.

[0038] The above-mentioned nut tightening tool, through the cooperation of the bearing mechanism 20, the gravity pressing mechanism 30 and the lifting rod 42, can stably and reliably position and support the power-assisting shaft 10, so that the power-assisting shaft 10 remains stable during the nut tightening process. Specifically, the bearing mechanism 20 positions and supports the housing 12, and the gravity pressing mechanism 30 presses the housing 12, so that the housing 12 remains stable; and the outer ring of the bearing 15 is pressed with the housing 12 by interference fit, so that the outer ring of the bearing 15 remains fixed. In addition, the gravity pressing mechanism 30 presses the worm wheel 11, the lifting rod 42 presses the power-assisting shaft 10, and the worm wheel 11 is fixedly sleeved on the power-assisting shaft 10, so that the power-assisting shaft 10 and the worm wheel 11 remain stable; and the inner ring of the bearing 15 cooperates with the power-assisting shaft 10 and the worm wheel 11, so that it is convenient to adjust the axial clearance between the inner and outer rings of the bearing 15 during the process of screwing the bearing locking nut 16 on the power-assisting shaft 10.

[0039] The above-mentioned nut tightening tool, through the ingenious cooperation between the lifting rod 42 and the screwing sleeve 44, drives the screwing sleeve 44 threaded on the outside of the lifting rod 42 to rotate after the lifting rod 42 tightens the power-assisting shaft 10, so that the screwing sleeve 44 drives the bearing locking nut 16 to be screwed onto the stably tightened power-assisting shaft 10.

[0040] In addition, the above-mentioned nut tightening tooling, through the pressure measuring element set at the end of the lifting rod 42, during the process of driving the screwing sleeve 44 to rotate, the pressure measuring element detects the force of the bearing locking nut 16 acting on the power-assisting shaft 10 and the bearing 15 and feeds back to the lifting rod 42, thereby monitoring the force of the bearing locking nut 16 on the bearing 15 and ensuring that the bearing locking nut 16 is accurately screwed into place.

[0041] Therefore, the above-mentioned nut tightening tool can accurately screw the bearing locking nut 16 into place, so that the bearing 15 meets the stiffness requirements that the axial clearance is eliminated and the axial displacement is in a suitable range under a certain axial force, thereby improving the yield rate. In addition, the above-mentioned nut tightening tool is simple and efficient to operate, which can improve production efficiency.

[0042] Figure 4 Shows the structure of the bearing mechanism; combined Figures 1 to 4 As shown, in some embodiments, the supporting mechanism 20 includes: a supporting seat 22, which is provided with a through hole 220 for the lifting rod 42 and the screw sleeve 44 to pass through; a plurality of support seats 24, which are fixed to the supporting seat 22 and respectively matched with a plurality of positioning holes of the shell 12; and a calibrator 26, which is distributed around the supporting seat 22.

[0043] The through hole 220 provided through the bearing seat 22 is used for the lifting rod 42 and the screwing sleeve 44 to pass through, so as to tighten the power-assisting shaft 10 and screw the bearing locking nut 16; through multiple support seats 24, stable and reliable multi-point support for the shell 12 is achieved; through the calibrator 26, it is possible to calibrate whether the power-assisting shaft 10 is assembled in place, so as to ensure that the bearing locking nut 16 is subsequently accurately screwed into place.

[0044] Figure 5 Shows the structure of the gravity clamping mechanism; combined Figures 1 to 5 As shown, in some embodiments, the gravity clamping mechanism 30 includes: an annular pressure head 33, which is adapted to the end face of the shell 12; a downward pressing cylinder 34, which is connected to the annular pressure head 33 and is used to drive the annular pressure head 33 to press down; a self-weight pressure rod, including a counterweight block 35a and a pressure rod connected to the counterweight block 35a, and the lower end face 35b of the pressure rod extends out of the annular pressure head 33 and is unidirectionally limited to the annular pressure head 33; as the annular pressure head 33 is pressed against the end face of the shell 12, the self-weight pressure rod presses against the upper end face of the worm gear 11 with its own weight.

[0045] The housing 12 is stably and reliably pressed by the annular pressing head 33 matched with the end surface of the housing 12 and the pressing cylinder 34 driving the annular pressing head 33 to press downward. The lower end surface 35b of the pressing rod is unidirectionally limited to the annular pressing head 33 to prevent the self-weight pressing rod from slipping in the non-pressing state; in the pressing state, the lower end surface 35b of the pressing rod presses the upper end surface of the worm wheel 11, so that the self-weight pressing rod floats relative to the annular pressing head 33, so that the self-weight pressing rod presses the upper end surface of the worm wheel 11 by its own weight.

[0046] The number / weight of the counterweight 35a can be adjusted as needed so that the deadweight pressure rod applies a suitable downward pressure to the worm gear 11. For example, the downward pressure is 780N, but not limited thereto.

[0047] Continue to combine Figures 1 to 5 As shown, in some embodiments, the lifting and screwing mechanism 40 also includes: a lifting motor 41, connected to a lifting rod 42, for driving the lifting rod 42 to rise and fall; wherein, the end of the lifting rod 42 is provided with an internal spline 42' adapted to the external spline 10' at the end of the power-assisting shaft 10.

[0048] The lifting motor 41 drives the lifting rod 42 to rise and fall, thereby tightening / loosening the booster shaft 10. The tightening force of the lifting rod 42 on the booster shaft 10 needs to be basically balanced with the downward pressure of the deadweight pressure rod on the worm gear 11, for example, 750N, but not limited thereto. The end of the lifting rod 42 and the end of the booster shaft 10 are splined to prevent rotation, ensuring that the booster shaft 10 remains stable when the bearing locking nut 16 is screwed.

[0049] In some embodiments, the lifting and screwing mechanism 40 further includes: a rotary motor 45 connected to the screwing sleeve 44 for driving the screwing sleeve 44 to rotate. Driven by the rotary motor 45, the screwing sleeve 44 can spirally rise along the lifting rod 42 to screw the bearing locking nut 16 to the power assist shaft 10.

[0050] Continue to combine Figures 1 to 5 As shown, in some embodiments, the bearing 15 includes: an upper bearing 15a, the end face of the outer ring of the upper bearing 15a is supported on the shoulder 120 of the housing 12, the upper end face of the inner ring of the upper bearing 15a abuts the lower end face of the worm gear 11, and the inner ring of the upper bearing 15a is interference fit with the power-assist shaft 10; and a lower bearing 15b, the end face of the outer ring of the lower bearing 15b is supported on the shoulder 120 of the housing 12, and the inner ring of the lower bearing 15b is sliding fit with the power-assist shaft 10.

[0051] As the bearing locking nut 16 presses against the lower end surface of the inner ring of the lower bearing 15b, the inner ring of the lower bearing 15b and the inner ring of the upper bearing 15a move up and down successively to eliminate the axial clearance of the lower bearing 15b and the axial clearance of the upper bearing 15a respectively, and the pressure measuring element detects the force of the bearing locking nut 16 on the upper bearing 15a.

[0052] Specifically, the process of screwing the bearing locking nut 16 into place includes the first stage and the second stage. In the first stage, the bearing locking nut 16 contacts and presses against the lower end surface of the inner ring of the lower bearing 15b. In this stage, the bearing locking nut 16 acts on the inner ring of the lower bearing 15b, driving the inner ring of the lower bearing 15b to slide upward to eliminate the axial clearance between the inner and outer rings of the lower bearing 15b. When the axial clearance of the lower bearing 15b is completely eliminated, the steel ball of the lower bearing 15b is stressed. At this time, since the housing 12 is fixed, the lower bearing 15b no longer moves, and enters the second stage: the force of the bearing locking nut 16 is transmitted to the power-assisting shaft 10, pulling the power-assisting shaft 10 to move downward; and the inner ring of the upper bearing 15a is pressed against the power-assisting shaft 10 by interference, so it moves downward with the power-assisting shaft 10 to eliminate the axial clearance between the inner and outer rings of the upper bearing 15a. At the same time, the power-assisting shaft 10 transmits the force to the lifting rod 42, and then the pressure measuring element detects the corresponding force.

[0053] When the tightening force of the lifting rod 42 on the assist shaft 10 is not equal to the downward force of the deadweight pressure rod on the worm gear 11, the pressure measuring element will detect a certain pre-force. In the second stage of screwing the bearing locking nut 16, the force detected by the pressure measuring element changes, which accurately reflects that the axial clearance of the upper bearing 15a has been eliminated and how much force the inner ring of the lower bearing 15b is bearing; further, by controlling the force of screwing the bearing locking nut 16, the force detected by the pressure measuring element is equal to the force required to eliminate the axial clearance (which can be obtained by preliminary testing) after deducting the pre-force, so that the bearing locking nut 16 can be accurately controlled to be screwed into place, so that the bearing 15 meets the stiffness requirements that the axial clearance is eliminated and the axial displacement under a certain axial force is in a suitable range.

[0054] In a specific example, for example, the force for screwing the bearing locking nut 16 is controlled to reach 1300N, so that the bearing locking nut 16 can be screwed into place, but the present invention is not limited thereto.

[0055] The embodiment of the present invention further provides a nut tightening method, based on the nut tightening tool as described in any of the above embodiments to tighten the bearing locking nut 16 of the power assist shaft 10. The features and principles of the nut tightening tool described in any of the above embodiments can be applied to the following nut tightening method embodiments.

[0056] Figure 6 Shows the main steps of the nut tightening method; combined Figures 1 to 6 As shown, the nut tightening method provided by the embodiment of the present invention includes:

[0057] S610 , the housing 12 is positioned and supported on the bearing mechanism 20 , and the gravity pressing mechanism 30 and the lifting rod 42 are driven to extend in sequence, so that the gravity pressing mechanism 30 presses the housing 12 and the worm gear 11 , and the lifting rod 42 presses the power assist shaft 10 .

[0058] The positioning and supporting principle of the housing 12 by the bearing mechanism 20 , the pressing principle of the housing 12 and the worm gear 11 by the gravity pressing mechanism 30 , and the pressing principle of the assist shaft 10 by the lifting rod 42 can be referred to the description of the above embodiments.

[0059] S620, driving the screwing sleeve 44 to rotate, so that the bearing locking nut 16 is screwed onto the power-assisting shaft 10 and presses against the inner ring of the bearing 15; wherein, during the process of driving the screwing sleeve 44 to rotate, the pressure measuring element detects a preset force and stops screwing the screwing sleeve 44.

[0060] During the process of screwing the bearing locking nut 16 , the action principle of the bearing locking nut 16 on the bearing 15 may refer to the description of the above embodiments.

[0061] The nut tightening method of the present invention can stably and reliably position and support the power-assisting shaft 10 through the cooperation of the bearing mechanism 20, the gravity pressing mechanism 30 and the lifting rod 42, so that the power-assisting shaft 10 remains stable during the nut tightening process; through the ingenious cooperation of the lifting rod 42 and the screwing sleeve 44, after the lifting rod 42 presses the power-assisting shaft 10, the screwing sleeve 44 is driven to rotate, so that the screwing sleeve 44 drives the bearing locking nut 16 to be screwed onto the power-assisting shaft 10; in addition, through the pressure measuring element provided at the end of the lifting rod 42, in the process of driving the screwing sleeve 44 to rotate, the pressure measuring element detects the force of the bearing locking nut 16 acting on the power-assisting shaft 10 and the bearing 15 and then feeding back to the lifting rod 42, so as to monitor the force of the bearing locking nut 16 on the bearing 15, and ensure that the bearing locking nut 16 is accurately screwed into place;

[0062] Therefore, the nut tightening method of the present invention can accurately screw the bearing locking nut 16 into place, so that the bearing 15 meets the stiffness requirements that the axial clearance is eliminated and the axial displacement is in a suitable range under a certain axial force, thereby improving the yield rate. In addition, the nut tightening tool and nut tightening method of the present invention are simple and efficient to operate, and can improve production efficiency.

[0063] In some embodiments, the preset force is determined based on the force required to eliminate the axial play of the bearing 15 and the response time of the lifting and screwing mechanism 40 (specifically, the response time of the rotary motor 45). The response time of the rotary motor 45 determines how much force the bearing locking nut 16 will be subjected to after the screwing sleeve 44 stops, that is, how much force the bearing locking nut 16 will still apply to the bearing 15; wherein, the functional relationship between the force and time on the bearing locking nut 16 can be obtained by monitoring in advance, or calculated based on parameters such as the rotation speed and torque of the rotary motor 45. The preset force is determined based on the force required to eliminate the axial play of the bearing 15 and the response time of the lifting and screwing mechanism 40, which can prevent the bearing locking nut 16 from being over-tightened and ensure that the bearing locking nut 16 is screwed into place.

[0064] In some embodiments, the bearing 15 includes an upper bearing 15a and a lower bearing 15b as described above, wherein the inner ring of the upper bearing 15a is interference fit with the power-assisting shaft 10, and the inner ring of the lower bearing 15b is sliding fit with the power-assisting shaft 10. In the process of driving the screw sleeve 44 to rotate, the first clearance elimination stage and the second clearance elimination stage are successively performed through the bearing locking nut 16; in the first clearance elimination stage, the bearing locking nut 16 lifts the inner ring of the lower bearing 15b, so that the inner ring of the lower bearing 15b moves upward to eliminate the axial clearance of the lower bearing 15b; in the second clearance elimination stage, the bearing locking nut 16 pulls down the inner ring of the upper bearing 15a through the power-assisting shaft 10, so that the inner ring of the upper bearing 15a moves downward to eliminate the axial clearance of the upper bearing 15a, and the pressure measuring element detects the force of the bearing locking nut 16 on the upper bearing 15a.

[0065] Specifically, as described in the above embodiment, in the first clearance elimination stage, the bearing locking nut 16 contacts and presses against the lower end surface of the inner ring of the lower bearing 15b. In this stage, the bearing locking nut 16 acts on the inner ring of the lower bearing 15b, driving the inner ring of the lower bearing 15b to slide upward to eliminate the axial clearance between the inner and outer rings of the lower bearing 15b. When the axial clearance of the lower bearing 15b is completely eliminated, the steel ball of the lower bearing 15b is stressed. At this time, since the housing 12 is fixed, the lower bearing 15b no longer moves, and enters the second clearance elimination stage: the force of the bearing locking nut 16 is transmitted to the power-assisting shaft 10, pulling the power-assisting shaft 10 to move downward; and the inner ring of the upper bearing 15a is pressed against the power-assisting shaft 10 by interference, so it moves downward with the power-assisting shaft 10 to eliminate the axial clearance between the inner and outer rings of the upper bearing 15a. At the same time, the power-assisting shaft 10 transmits the force to the lifting rod 42, and then the pressure measuring element detects the corresponding force.

[0066] When the tightening force of the lifting rod 42 on the assist shaft 10 is not equal to the downward force of the deadweight pressure rod on the worm gear 11, the pressure measuring element will detect a certain pre-force. In the second stage of screwing the bearing locking nut 16, the force detected by the pressure measuring element changes, which accurately reflects that the axial clearance of the upper bearing 15a has been eliminated and how much force the inner ring of the lower bearing 15b is bearing; further, by controlling the force of screwing the bearing locking nut 16, the force detected by the pressure measuring element is equal to the force required to eliminate the axial clearance (which can be obtained by preliminary testing) after deducting the pre-force, so that the bearing locking nut 16 can be accurately controlled to be screwed into place, so that the bearing 15 meets the stiffness requirements that the axial clearance is eliminated and the axial displacement under a certain axial force is in a suitable range.

[0067] In a specific example, for example, the force for screwing the bearing locking nut 16 is controlled to reach 1300N, so that the bearing locking nut 16 can be screwed into place, but the present invention is not limited thereto.

[0068] Further, continue to combine Figures 1 to 6 As shown, in some embodiments, the nut tightening method also includes a gap measurement process, which includes: driving the lifting rod 42 to retract; driving the lifting rod 42 to extend, and measuring the axial displacement of the bearing 15 when the difference between the lifting force of the lifting rod 42 and the downward pressure of the gravity clamping mechanism 30 reaches a preset negative value and a preset positive value respectively; determining whether the bearing 15 meets the standards based on the sum of the two measured axial displacements.

[0069] When the driving lifting rod 42 is retracted, only the gravity pressing mechanism 30 presses down the housing 12 and the worm gear 11; when the driving lifting rod 42 is extended, the lifting force of the lifting rod 42 gradually offsets the downward pressure of the gravity pressing mechanism 30. When the difference between the lifting force and the downward pressure reaches a preset negative value (for example, -100N, at which time the lifting force is 100N less than the downward pressure) and a preset positive value (for example, 100N, at which time the lifting force is 100N greater than the downward pressure), the axial displacement between the inner and outer rings of the bearing 15 is detected by the displacement sensor 38, and the two measured axial displacements are added. If it is within the set displacement range (for example, 4 to 10μm), it can be determined that the axial clearance of the bearing 15 meets the standard.

[0070] In addition, when the axial clearance of the bearing 15 (ie, the sum of the axial displacements measured twice) is greater than the set displacement range, the axial clearance of the bearing 15 can be adjusted again by tightening the nut.

[0071] In summary, the nut tightening tool and the nut tightening method of the present invention can accurately screw the bearing locking nut 16 into place, so that the bearing 15 meets the stiffness requirements that the axial clearance is eliminated and the axial displacement is in a suitable range under a certain axial force, thereby improving the yield rate. The nut tightening tool and the nut tightening method of the present invention are simple and efficient to operate, and can improve production efficiency.

[0072] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A nut tightening tool, used for tightening the bearing locking nut of a power-assisting shaft, wherein a worm gear is fixedly mounted on the power-assisting shaft, the worm gear is accommodated in a housing, and a bearing for rotatably supporting the power-assisting shaft and the worm gear is assembled in the housing; It is characterized in that The nut tightening tool comprises: A bearing mechanism, used for positioning and supporting the housing; A gravity pressing mechanism, used for pressing the housing and the worm gear; The lifting and screwing mechanism includes a lifting rod that can be raised and lowered and a screwing sleeve that is rotatably screwed to the outside of the lifting rod. The lifting rod is used to tighten the power-assisting shaft. A pressure measuring element is provided at the end of the lifting rod, and an assembly groove for assembling the bearing locking nut is provided at the end of the screwing sleeve.

2. The nut tightening tool according to claim 1, characterized in that: The carrying mechanism comprises: A bearing seat, provided with a through hole for the jacking rod and the screwing sleeve to pass through; A plurality of support seats, fixed to the bearing seat, respectively matched with the plurality of positioning holes of the shell; The calibrators are distributed around the supporting base.

3. The nut tightening tool according to claim 1, characterized in that: The gravity pressing mechanism comprises: An annular pressure head adapted to the end surface of the shell; A downward pressure cylinder connected to the annular pressure head and used to drive the annular pressure head to press downward; A deadweight pressure rod, comprising a counterweight block and a pressure rod connected to the counterweight block, wherein the lower end surface of the pressure rod extends out of the annular pressure head and is unidirectionally limited to the annular pressure head; As the annular pressure head presses against the end surface of the housing, the self-weight pressure rod presses against the upper end surface of the worm wheel by its own weight.

4. The nut tightening tool according to claim 1, characterized in that: The lifting and screwing mechanism also includes: A lifting motor connected to the lifting rod and used to drive the lifting rod to move up and down; Wherein, the end of the lifting rod is provided with an internal spline which is matched with the external spline of the end of the power-assisting shaft.

5. The nut tightening tool according to claim 1, characterized in that: The lifting and screwing mechanism also includes: A rotary motor is connected to the screw sleeve and is used to drive the screw sleeve to rotate.

6. The nut tightening tool according to any one of claims 1 to 5, characterized in that: The bearing comprises: An upper bearing, wherein the end face of the outer ring of the upper bearing is supported on the shoulder of the housing, the upper end face of the inner ring of the upper bearing abuts against the lower end face of the worm gear, and the inner ring of the upper bearing is interference fit with the power-assisting shaft; A lower bearing, wherein the end surface of the outer ring of the lower bearing is supported on the shoulder of the housing, and the inner ring of the lower bearing is slidably matched with the power-assisting shaft; As the bearing locking nut presses against the lower end surface of the inner ring of the lower bearing, the inner ring of the lower bearing and the inner ring of the upper bearing move up and down successively to eliminate the axial clearance of the lower bearing and the axial clearance of the upper bearing respectively, and the pressure measuring element detects the force of the bearing locking nut on the upper bearing.

7. A nut tightening method, characterized in that: Based on tightening the bearing locking nut of the power-assisting shaft with the nut tightening tool according to any one of claims 1 to 6, the nut tightening method comprises: The housing is positioned and supported on the bearing mechanism, and the gravity pressing mechanism and the lifting rod are driven to extend successively, so that the gravity pressing mechanism presses the housing and the worm gear, and the lifting rod presses the power-assisting shaft; The screw sleeve is driven to rotate, so that the bearing locking nut is screwed onto the power-assisting shaft and tightens the inner ring of the bearing; Wherein, during the process of driving the screwing sleeve to rotate, when the pressure measuring element detects a preset force, the screwing sleeve is stopped.

8. The nut tightening method according to claim 7, characterized in that: The preset force is determined according to the force required to eliminate the axial clearance of the bearing and the response time of the lifting and screwing mechanism.

9. The nut tightening method according to claim 7, characterized in that: The bearing comprises an upper bearing and a lower bearing, the end face of the outer ring of the upper bearing is supported on the shoulder of the housing, the upper end face of the inner ring of the upper bearing abuts against the lower end face of the worm wheel, the inner ring of the upper bearing is interference fit with the power-assisting shaft, the end face of the outer ring of the lower bearing is supported on the shoulder of the housing, and the inner ring of the lower bearing is slidingly fit with the power-assisting shaft; During the process of driving the screwing sleeve to rotate, the first clearance elimination stage and the second clearance elimination stage are successively performed through the bearing locking nut; In the first clearance elimination stage, the bearing locking nut lifts the inner ring of the lower bearing, so that the inner ring of the lower bearing moves upward to eliminate the axial clearance of the lower bearing; In the second clearance elimination stage, the bearing locking nut pulls down the inner ring of the upper bearing through the power-assist shaft, so that the inner ring of the upper bearing moves downward to eliminate the axial clearance of the upper bearing, and the pressure measuring element detects the force of the bearing locking nut on the upper bearing.

10. The nut tightening method according to claim 7, characterized in that: Also includes: driving the lifting rod to retract; The jacking rod is driven to extend, and when the difference between the jacking force of the jacking rod and the downward force of the gravity pressing mechanism reaches a preset negative value and a preset positive value respectively, the axial displacement of the bearing is measured; The compliance of the bearing with the standard is determined based on the sum of the axial displacements measured twice.

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