Preload measuring method for hub unit bearing

Abstract

To provide a preload measuring method for a hub unit bearing capable of suppressing a thrust load applied to the hub unit bearing and applicable to various types of hub unit bearings.SOLUTION: A preload measurement method for a hub unit bearing comprises: a torque measurement process S1 in which a radial load F1 is applied between an outer ring 2 and a hub 3 and the torque of the hub unit bearing 1 is measured while increasing the radial load F1; and a preload calculation process S2 in which the preload applied to rolling elements 4a and 4b is determined based on the radial load F1 applied between the outer ring 2 and the hub 3 at the time when the torque suddenly decreases.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a method for measuring preload in a hub unit bearing. [Background technology]

[0002] A hub unit bearing supports the wheels of an automobile for rotation relative to a suspension system. The hub unit bearing includes an outer ring having multiple rows of outer ring raceways on its inner circumferential surface, a hub having multiple rows of inner ring raceways on its outer circumferential surface, and a plurality of rolling elements arranged to roll freely between the multiple rows of outer ring raceways and the multiple rows of inner ring raceways.

[0003] In a hub unit bearing, a preload is applied to the rolling elements to suppress rattling between the outer ring and the hub and to enable smooth relative rotation between the outer ring and the inner ring.

[0004] If the preload applied to the rolling elements is too large, problems such as a shortened lifespan of the hub unit bearing and a deterioration in the running performance of the vehicle due to an increase in the dynamic torque of the hub unit bearing are likely to occur.

[0005] On the other hand, if the preload applied to the rolling elements is too small, the moment rigidity of the hub unit bearing will be insufficient, which can easily cause problems such as a decrease in vehicle handling stability.

[0006] For this reason, the preload in the hub unit bearing must be strictly controlled, and after assembly of the hub unit bearing is complete, it is required to inspect whether an appropriate preload is applied to the rolling elements.

[0007] JP 2021-148710 A discloses a preload measurement method that can calculate the preload applied to the rolling elements after assembly of the hub unit bearing is completed.

[0008] The preload measurement method described in JP 2021-148710 A measures the axial relative distance between the outer ring and the hub while increasing the thrust load that presses the outer ring and the hub from both axial sides. Then, an inflection point on the transition line of the relative distance is identified, and the thrust load at which the inflection point appears is determined. After that, the preload applied to the rolling elements of the hub unit bearing is calculated from the thrust load. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent Publication No. 2021-148710 [Non-patent literature]

[0010] [Non-Patent Document 1] "NSK Technical Report", NSK Ltd., 2020 edition (first published September 1991) Summary of the Invention [Problem to be solved by the invention]

[0011] The preload measurement method described in JP 2021-148710 A identifies an inflection point on the transition line of the axial relative distance between the outer ring and the hub, and calculates the preload using the inflection point, so there are two problems as follows:

[0012] First, in a tapered roller hub unit bearing that uses tapered rollers as rolling elements, when a thrust load is applied, the transition line of the axial relative distance between the outer ring and the hub hardly bends and becomes almost linear, making it difficult to identify the inflection point. For this reason, it is difficult to apply the preload measurement method described in JP 2021-148710 A to a tapered roller hub unit bearing.

[0013] In addition, even when a thrust load is applied to a ball bearing type hub unit bearing, the change in the inflection point that appears on the transition line of the axial relative distance between the outer ring and the hub is small, so in order to identify the inflection point, it is necessary to apply at least two thrust loads of different values ​​that are sufficiently larger than the thrust load at which the inflection point appears. This increases the amount of work required to calculate the preload. In addition, damage such as scratches and indentations may occur on the raceway surface and rolling surface.

[0014] In addition, the Technical Report also includes the following technical content related to the present disclosure: the load factor ε decreases as the radial load acting on the bearing increases, and the rotational torque of the bearing is determined by the speed term M v and the load term M, which is a friction term that is independent of the rotational speed other than the fluid friction term. i It is described that the above can be obtained as the sum of

[0015] An object of the present disclosure is to provide a preload measuring method for a hub unit bearing that can reduce the thrust load applied to the hub unit bearing and that can be applied to various types of hub unit bearings. [Means for solving the problem]

[0016] The present disclosure relates to a method for measuring a preload of a hub unit bearing, an outer ring having a plurality of rows of outer ring raceways on an inner circumferential surface; A hub having a plurality of rows of inner ring raceways on its outer circumferential surface; a plurality of rolling elements, each of which is rollably disposed between the plurality of rows of outer ring raceways and the plurality of rows of inner ring raceways and to which a preload is applied; The present invention relates to a hub unit bearing comprising:

[0017] A method for measuring a preload of a hub unit bearing according to a first aspect of the present disclosure includes: a torque measuring process for applying a radial load between the outer ring and the hub and measuring a torque of the hub unit bearing, specifically, a starting torque or a rotational torque, while increasing the radial load; a preload calculation step of calculating the preload based on the radial load applied between the outer ring and the hub at a time when the torque suddenly decreases; Equipped with.

[0018] In a preload measuring method for a hub unit bearing of a second aspect of the present disclosure, in the preload measuring method for a hub unit bearing of the first aspect of the present disclosure, the multi-row outer ring raceways are composed of double row outer ring raceways and the multi-row inner ring raceways are composed of double row inner ring raceways, and in the preload calculation step, the preload can be determined based on the radial load applied between the outer ring and the hub at the time the torque first suddenly decreased.

[0019] In a preload measuring method for a hub unit bearing of a third aspect of the present disclosure, in the preload measuring method for a hub unit bearing of the first or second aspect of the present disclosure, the multiple rows of outer ring raceways can be composed of double row outer ring raceways and the multiple rows of inner ring raceways can be composed of double row inner ring raceways, and the rolling elements of one row of the plurality of rolling elements can be composed of balls and the rolling elements of the other row of the plurality of rolling elements can be composed of tapered rollers. That is, the preload measuring method for a hub unit bearing of the third aspect of the present disclosure can be applied to a hybrid type hub unit bearing.

[0020] A preload measuring method for a hub unit bearing according to a fourth aspect of the present disclosure may be the same as the preload measuring method for a hub unit bearing according to the first aspect of the present disclosure, except that the multiple rows of outer ring raceways are composed of three or more rows of outer ring raceways, and the multiple rows of inner ring raceways are composed of three or more rows of inner ring raceways. That is, the preload measuring method for a hub unit bearing according to the fourth aspect of the present disclosure may be applicable to a multi-row hub unit bearing having three or more rows. Furthermore, the preload measuring method for a hub unit bearing according to the fourth aspect of the present disclosure may include a determination step of determining which row's load factor has decreased based on the amount of decrease in torque. Effect of the Invention

[0021] According to the method for measuring the preload of a hub unit bearing of the present invention, the thrust load applied to the hub unit bearing can be reduced, and the method can be applied to various types of hub unit bearings. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a hub unit bearing that is the subject of a preload measuring method for a hub unit bearing according to a first example of an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a cross-sectional view showing a state in which the first example of the method for measuring preload of a hub unit bearing is carried out. [Diagram 3] FIG. 3 is a diagram showing the relationship between the radial load F1 applied to the hub and the torque T acting on the outer ring. [Figure 4] Figure 4 is a diagram to explain the width of the load area when a radial load and an axial load act on a single-row rolling bearing with a contact angle α, where Figure 4(A) is a cross-sectional view of the single-row ball bearing, Figure 4(B) is a view of the outer surface of the inner ring from the axial direction, and Figure 4(C) is a view of the inner ring from the radial direction. [Diagram 5] FIG. 5 is a diagram showing a schematic relationship between the radial load Fr applied to a single row rolling bearing and the torque of the single row rolling bearing. [Figure 6] FIG. 6 is a cross-sectional view showing another example of a hub unit bearing to which the preload measuring method for a hub unit bearing according to the first embodiment of the present disclosure can be applied. [Figure 7] FIG. 7 is a diagram corresponding to FIG. 2 and relating to a second example of the embodiment of the present disclosure. [Figure 8] FIG. 8 is a diagram corresponding to FIG. 2 and relating to a third example of the embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] [Example 1] A first example of an embodiment of the present disclosure will be described with reference to FIGS. 1 to 5. FIG.

[0024] <Hub unit bearing structure> FIG. 1 shows a hub unit bearing 1 that is the subject of a preload measuring method according to an embodiment of the present disclosure.

[0025] The hub unit bearing 1 includes an outer ring 2, a hub 3, and a plurality of rolling elements 4a, 4b.

[0026] With regard to hub unit bearing 1, the left side in FIG. 1 and the lower side in FIG. 2, which are located on the outer side in the width direction of the vehicle when hub unit bearing 1 is assembled to the vehicle, are referred to as the outer axial direction, and the right side in FIG. 1 and the upper side in FIG. 2, which are located on the central side in the width direction of the vehicle when hub unit bearing 1 is assembled to the vehicle, are referred to as the inner axial direction.

[0027] The outer ring 2 has a substantially cylindrical shape and has a plurality of rows of outer ring raceways 5a, 5b on its inner circumferential surface.

[0028] In this example, the outer ring 2 has double-row outer ring raceways 5a, 5b on its inner circumferential surface. That is, the outer ring 2 has two rows of outer ring raceways 5a, 5b.

[0029] The double row outer ring raceways 5a, 5b have an arc-shaped cross section in a cross section including the center axis of the outer ring 2.

[0030] The outer ring 2 has a stationary flange 6 protruding radially outward at an axially intermediate portion. The stationary flange 6 has support holes 7 penetrating in the axial direction at a plurality of circumferential positions at the radially intermediate portion.

[0031] In this example, the support hole 7 is configured as a screw hole. The outer ring 2 is supported and fixed to the suspension by a support bolt that is inserted through a through hole provided in the knuckle of the suspension and is screwed into the support hole 7 of the stationary flange 6 from the inside in the axial direction, so that the outer ring 2 does not rotate even when the wheel rotates.

[0032] The support hole may be a circular hole. In this case, the outer ring is supported and fixed to the knuckle by screwing a support bolt inserted through the support hole into a threaded hole provided in the knuckle, or by screwing a nut onto a tip of a support bolt inserted through the support hole and a through hole provided in the knuckle.

[0033] The outer ring 2 is made of a hard metal such as medium carbon steel.

[0034] The hub 3 is disposed radially inside the outer ring 2 and coaxially with the outer ring 2. The hub 3 has a plurality of rows of inner ring raceways 8a, 8b on its outer circumferential surface.

[0035] In this example, the hub 3 has double row inner ring raceways 8a, 8b on its outer circumferential surface. That is, the hub 3 has two rows of inner ring raceways 8a, 8b.

[0036] The double row inner ring raceways 8a, 8b have an arc-shaped cross section in a cross section including the central axis of the hub 3.

[0037] The double row inner ring raceways 8a, 8b are provided over the entire circumference of the outer circumferential surface of the hub 3 in portions that face the double row outer ring raceways 5a, 5b.

[0038] The hub 3 has a rotation flange 9 protruding radially outward at a portion protruding axially outward beyond the outer ring 2, and also has a cylindrical pilot portion 10 at the axially outer end.

[0039] The rotating flange 9 has mounting holes 11 penetrating in the axial direction at multiple circumferential positions in the radially middle portion. Studs 12 for connecting and fixing a braking rotor such as a disc or drum and a wheel that constitutes a wheel to the rotating flange 9 are press-fitted into each of the mounting holes 11 with serrations. That is, in this example, the mounting holes 11 are cylindrical holes.

[0040] A braking rotating body such as a brake disc and a wheel of a vehicle are connected and fixed to the rotating flange 9 by inserting a pilot portion 10 into a central hole provided in the center of each of them and inserting a stud 12 into through holes provided at multiple locations in the circumferential direction of each of them in the radial middle portion, and then screwing a hub nut onto the tip of the stud 12.

[0041] The mounting hole 11 of the rotating flange 9 can also be configured as a screw hole. In this case, the braking rotor and the wheel are connected and fixed to the rotating flange 9 by screwing a hub bolt, which has passed through a through hole provided in the braking rotor and a through hole provided in the wheel, into the mounting hole 11 from the outside in the axial direction.

[0042] Since the hub unit bearing 1 of this example is a hub unit bearing for a driven wheel, the hub 3 is solid. However, the preload measuring method for a hub unit bearing according to one embodiment of the present disclosure can also be applied to a hub unit bearing for a driving wheel. In this case, the target hub unit bearing has a spline hole penetrating in the axial direction at the center of the hub. A tip end of a drive shaft that is rotated and driven by an engine or an electric motor as a drive source is spline-engaged with the spline hole. When the automobile is traveling, the hub is rotated by the drive shaft, thereby rotating and driving the wheel and the braking rotor that are coupled and fixed to the rotating flange of the hub.

[0043] The hub 3 is formed by combining an inner ring 13 and a hub ring 14 .

[0044] The inner ring 13 has an annular shape, and has at least the axially innermost inner ring raceway 8b among the multiple rows of inner ring raceways 8a, 8b on its outer circumferential surface.

[0045] In this example, the inner ring 13 has, at an axially inner middle portion of its outer circumferential surface, the inner ring raceway 8b, which is one of the double row inner ring raceways 8a, 8b.

[0046] The inner ring 13 is made of a hard metal such as bearing steel.

[0047] The hub ring 14 has, on its outer circumferential surface, at least the inner ring raceway 8a which is the axially outermost one of the multiple rows of inner ring raceways 8a, 8b.

[0048] In this example, the hub wheel 14 has, in the axially outermost portion of the double row inner ring raceways 8a, 8b, the inner ring raceway 8a in the axially outermost portion of the outer circumferential surface.

[0049] The hub wheel 14 has a rotating flange 9 that protrudes radially outward at a portion located axially outer than the axially outer inner ring raceway 8a, and has a cylindrical pilot portion 10 at its axially outer end.

[0050] The hub ring 14 has a small diameter step 15, located axially more inward than the axially outer inner ring raceway 8a, which has an outer diameter smaller than that of an adjacent axially outer portion. The hub ring 14 has a step surface 16 facing axially inward at the axially outer end of the small diameter step 15, and has a crimped portion 17 bent radially outward from the axially inner end of the small diameter step 15.

[0051] The hub ring 14 is made of a hard metal such as medium carbon steel.

[0052] The inner ring 13 is fitted onto the small diameter step 15 of the hub ring 14, and is sandwiched from both axial sides between a step surface 16 and a crimped portion 17 of the hub ring 14. In this way, the inner ring 13 and the hub ring 14 are joined to form the hub 3, and a preload is applied to the rolling elements 4a, 4b.

[0053] In addition, the inner ring can also be clamped from both axial sides between the step surface of the hub wheel and the nut by screwing a nut onto the axially inner end of the hub wheel that protrudes from the axially inner end of the inner ring.

[0054] The rolling elements 4a, 4b are disposed between a plurality of rows of outer ring raceways 5a, 5b and a plurality of rows of inner ring raceways 8a, 8b so as to be rollable in each row, and a preload is applied thereto.

[0055] In this example, the rolling elements 4a and 4b are formed of balls.

[0056] Half the diameter of the rolling elements 4a, 4b is slightly smaller than the respective radii of curvature of the outer ring raceways 5a, 5b and the inner ring raceways 8a, 8b.

[0057] The rolling elements 4a, 4b are made of an iron alloy such as bearing steel or ceramics.

[0058] The rolling elements 4a, 4b are arranged at equal intervals in the circumferential direction by using ring-shaped cages 18a, 18b.

[0059] The hub unit bearing 1 has an equal diameter PCD type structure in which the pitch circle diameter of the rolling elements 4a in the axially outer row is equal to the pitch circle diameter of the rolling elements 4b in the axially inner row. However, the preload measurement method for a hub unit bearing according to one embodiment of the present disclosure can also be applied to a different diameter PCD type hub unit bearing in which the pitch circle diameter of the rolling elements in the axially outer row is larger or smaller than the pitch circle diameter of the rolling elements in the axially inner row.

[0060] <Hub unit bearing preload measuring device> An example of a preload measuring device capable of implementing the preload measuring method for a hub unit bearing according to an embodiment of the present disclosure will be described with reference to FIG.

[0061] With respect to the preload measuring device 19, the axial direction, radial direction, and circumferential direction refer to the axial direction, radial direction, and circumferential direction of the hub unit bearing 1 unless otherwise specified.

[0062] The preload measuring device 19 of this example measures the preload applied to the rolling elements 4a, 4b with the hub unit bearing 1 facing with the axially inner side facing upward and the axially outer side facing downward.

[0063] The preload measuring method for a hub unit bearing according to an embodiment of the present disclosure can be performed with the hub unit bearing facing upward on the axially outer side and facing downward on the axially inner side, or with the axial direction of the hub unit bearing facing horizontally. However, in order to prevent a radial load from being applied between the outer ring and the hub due to the action of gravity, the preload measuring method for a hub unit bearing according to an embodiment of the present disclosure is preferably performed with the axial direction of the hub unit bearing facing vertically.

[0064] The preload measuring device 19 includes a load applying device 20, a rotary drive device 21, a torque measuring device 22, and a computing unit 23.

[0065] The load applying device 20 applies a radial load F1 between the outer ring 2 and the hub 3. In this example, the load applying device 20 presses the hub 3 in the radial direction.

[0066] The load application device 20 includes a hub support jig 24 , a bearing device 25 , an arm 26 , and an actuator 27 .

[0067] The hub support jig 24 is supported relative to the hub 3 .

[0068] In this example, the hub support jig 24 has a generally stepped cylindrical shape. Specifically, the hub support jig 24 has, in order from the inside in the axial direction, a large diameter portion 28, a medium diameter portion 29, and a small diameter portion 30.

[0069] The large diameter portion 28 has a recess 31 in the center of its axially inner surface, into which the pilot portion 10 of the hub 3 can be inserted without radial rattle, and also has insertion holes (not shown) at multiple circumferential locations on the axially inner surface around the recess 31, into which the tips of the studs 12 can be inserted.

[0070] The hub 3 is supported in the hub support jig 24 so that relative rotation is disabled by inserting the pilot portion 10 into the recess 31 without any radial play, and by inserting the tips of the studs 12 press-fitted into each of the mounting holes 11 into the insertion holes.

[0071] The bearing device 25 is fitted onto the small diameter portion 30 of the hub support jig 24 without any rattle. In this example, the bearing device 25 is configured as a bearing unit consisting of two combined radial rolling bearings. However, the bearing device 25 is not particularly limited as long as it can support the moment load, and can also be configured from a single radial rolling bearing.

[0072] The arm 26 is configured in a generally rod-like shape and extends in the axial direction. An end portion on the outer side in the axial direction of the arm 26 (the lower end portion in FIG. 2) is pressed against one circumferential position on the outer circumferential surface of the bearing device 25. An end portion on the inner side in the axial direction of the arm 26 (the upper end portion in FIG. 2) is located radially outward of a portion whose axial position coincides with the center position between the double-row rolling elements 4a, 4b.

[0073] The actuator 27 is configured to be able to press the axially inner end of the arm 26 radially inward. As a result, the load application device 20 is configured to be able to apply an equal load (=F1 / 2) to the double row rolling elements 4a, 4b by applying a radial load F1 to a portion whose axial position coincides with the center position between the double row rolling elements 4a, 4b.

[0074] The actuator 27 can be configured by, but is not limited to, a hydraulic or pneumatic actuator, or a pressing device equipped with a rotary-linear conversion mechanism such as a feed screw mechanism or a cam mechanism, and a servo motor.

[0075] The rotation drive device 21 rotationally drives the hub 3. In this example, the rotation drive device 21 rotationally drives the hub 3 via a hub support jig 24.

[0076] The rotation drive device 21 includes an electric motor 32. In this example, a motor output shaft 33 of the electric motor 32 is connected to a driven shaft 36 provided at the center of the axially outer surface of the small diameter portion 30 of the hub support jig 24 so as to be capable of transmitting torque via two joints (constant velocity joints) 34a, 34b and an intermediate shaft 35. However, when carrying out the method for measuring preload of a hub unit bearing according to an embodiment of the present disclosure, the structure of the portion that rotates the hub is not limited to this example.

[0077] The rotary drive device 21 rotates the hub 3 at a sufficiently slow rotation speed, specifically, but not limited to, 3s -1 The rotation speed is as follows:

[0078] The torque measuring device 22 measures the torque, that is, the starting torque or the running torque, of the hub unit bearing 1. In this example, the torque measuring device 22 is configured to be able to measure the torque T acting on the outer ring 2.

[0079] The outer ring 2 tends to rotate as the hub 3 is rotated by the rotary drive device 21. Therefore, the torque measuring device 22 of this example measures the torque T acting on the outer ring 2 as the torque of the hub unit bearing 1.

[0080] The torque measuring device 22 includes an outer ring supporting jig 37 and a torque sensor 38 .

[0081] The outer ring support jig 37 is supported and fixed to the outer ring 2, and is supported rotatably without generating torque by a fixed portion 39 which does not displace or rotate even when the preload measuring device 19 is in use.

[0082] In this example, the outer ring support jig 37 has a generally stepped cylindrical shape. Specifically, the outer ring support jig 37 has, in order from the outside in the axial direction, a small diameter portion 40 and a large diameter portion 41.

[0083] The small diameter portion 40 has a recess 42 at the center of its axially outer surface, into which the axially inner end portion of the outer ring 2 can be inserted without any radial backlash.

[0084] The large diameter portion 41 is rotatably supported by a hydrostatic bearing 43 relative to the fixed portion 39 .

[0085] With its axially inner end inserted without rattle into the recess 42, the outer ring 2 is supported and fixed to the outer ring support jig 37 so as to prevent relative rotation. Specifically, for example, a bolt passing through a through hole provided in the small diameter portion 40 is screwed into a support hole 7 provided in the stationary flange 6 of the outer ring 2, thereby supporting and fixing the outer ring 2 to the outer ring support jig 37 so as to prevent relative rotation.

[0086] The torque sensor 38 measures the torque acting on the outer ring 2, which is the torque T acting on the outer ring 2, acting on the outer ring support jig 37 to which the outer ring 2 is supported and fixed. In this example, the torque sensor 38 includes a shaft end 38a, an arm 38b, and a load cell 38c. The shaft end 38a protrudes axially inward from the center of the axially inner surface of the large diameter portion 41 of the outer ring support jig 37. The arm 38b protrudes radially outward from one circumferential position on the outer peripheral surface of the shaft end 38a. The load cell 38c is stretched between the tip end (the radially outer end) of the arm 38b and the fixed portion 39. However, when carrying out the preload measuring method for a hub unit bearing according to one embodiment of the present disclosure, the torque sensor is not particularly limited as long as it can measure the torque acting on the outer ring directly or via another member.

[0087] The calculator 23 has the function of calculating the preload applied to the rolling elements 4a, 4b based on the torque of the hub unit bearing 1 measured by the torque measuring device 22 and the radial load F1 applied between the outer ring 2 and the hub 3 by the load applying device 20.

[0088] In the preload measuring device 19 of this example, the hub 3 is rotated by the rotary drive device 21 and the hub 3 is pressed radially inward by the load applying device 20, thereby applying a radial load F1 between the outer ring 2 and the hub 3, and while increasing the radial load F1, the torque measuring device 22 measures the torque T acting on the outer ring 2. The calculator 23 has a function of calculating the preload applied to the rolling elements 4a, 4b based on the radial load F1 applied between the outer ring 2 and the hub 3 by the load applying device 20 at the point in time when the torque T acting on the outer ring 2 measured by the torque measuring device 22 suddenly drops.

[0089] More specifically, the calculator 23 of the preload measuring device 19 in this example has the function of calculating the preload applied to the rolling elements 4a, 4b based on the radial load F1 applied between the outer ring 2 and the hub 3 by the load application device 20 at the time when the torque T acting on the outer ring 2 measured by the torque measuring device 22 first suddenly drops.

[0090] <How to measure preload on hub unit bearings> We will now explain a preload measurement method for measuring the preload applied to the rolling elements 4a, 4b of the hub unit bearing 1. The preload measurement method (preload measurement process) can be carried out by being incorporated into the assembly process of the hub unit bearing 1, or can be carried out independently of the assembly process.

[0091] A preload measuring method for a hub unit bearing according to an embodiment of the present disclosure measures the preload applied to the rolling elements 4a, 4b by utilizing the fact that the load factor ε decreases as the radial load acting on the hub unit bearing 1 increases.

[0092] The principle of preload measurement by the preload measuring method for a hub unit bearing according to one embodiment of the present disclosure will be described with reference to FIGS. 4(A) to 5. FIG.

[0093] As shown in FIG. 4(A) to FIG. 4(C), a single-row rolling bearing 44 having a contact angle α is subjected to a radial load F r and axial load F aA single row rolling bearing 44 comprises an outer ring 46 having an outer ring raceway 45 on its inner peripheral surface, an inner ring 48 having an inner ring raceway 47 on its outer peripheral surface, and rolling elements 49 arranged between the outer ring raceway 45 and the inner ring raceway 47 so as to be able to roll freely with a contact angle α being given to them. In the illustrated example, balls are used as the rolling elements 49, but tapered rollers can also be used in the same way.

[0094] The width of the load area of ​​the single-row rolling bearing 44 is the radial load F r and axial load F a The width of such a loaded area is represented by the load factor ε. Specifically, as shown in Figures 4(B) and 4(C), when the loaded area exists only in a part of the circumferential direction, the load factor ε is represented by the ratio of the diameter D of the inner ring raceway to the projected length εD of the loaded area (εD / D=ε). In such a case, the value of the load factor ε is 1 or less (ε≦1). In contrast, when the loaded area exists over the entire circumference, the load factor ε is expressed by the elastic displacement δ of the rolling element 49 at the maximum load position of the loaded area, i.e., the rolling element 49 that receives the maximum load. max and the elastic displacement δ of the rolling element 49 at the minimum load position in the load zone, i.e., the rolling element 49 receiving the minimum load. min Using these, it is expressed by the following equation (1).

number

[0095] FIG. 5 shows the torque of the single-row rolling bearing 44, specifically the starting torque or the running torque, and the radial load F acting on the single-row rolling bearing 44. r As shown in FIG. 5, the torque of the single-row rolling bearing 44 is expressed as a function of the radial load F r As the radial load F increases, the load increases gradually for a certain period, then suddenly drops for a certain amount. This phenomenon is called r This occurs because the number of rolling elements 49 present in the loaded area decreases as the loaded area decreases with an increase in the load.

[0096] For example, when only a preload is applied to the single-row rolling bearing 44, a radial load F r Start applying this radial load F r is gradually increased, a phenomenon occurs in which the torque of the single-row rolling bearing 44 suddenly drops midway. In this case, the moment when the torque of the single-row rolling bearing 44 first suddenly drops occurs is the moment when the load zone switches from a state in which the load zone exists over the entire circumference to a state in which the load zone exists only in a portion of the circumference, that is, the moment when the value of the load factor ε falls below 1.

[0097] As described above, the width of the load area of ​​the single-row rolling bearing 44, that is, the load factor ε, is determined by the radial load F r and axial load F a Therefore, the radial load F at the moment when the torque of the single-row rolling bearing 44 first suddenly drops, that is, when the value of the load factor ε becomes 1 (strictly speaking, when it falls below 1), r Based on this, the axial load F corresponding to the preload applied to the rolling element 49 is a Based on this principle, in the preload measuring method for a hub unit bearing according to one embodiment of the present disclosure, the preload applied to the rolling elements 4a, 4b is determined.

[0098] Next, the preload measuring method of this embodiment will be specifically described.

[0099] The preload measuring method of this embodiment includes a torque measuring step S1 and a preload calculating step S2. Hereinafter, a case where the preload measuring method is carried out using a preload measuring device 19 will be described.

[0100] (Torque measurement process S1) In the torque measurement process S1, a radial load is applied between the outer ring 2 and the hub 3, and the torque of the hub unit bearing 1 is measured while the radial load is increased. Specifically, in this example, the hub 3 is rotated, and a radial load F1 is applied to the hub 3, and the torque T acting on the outer ring 2 is measured while the radial load F1 is increased.

[0101] For this purpose, first, the hub unit bearing 1 to be measured is set in the preload measuring device 19. Specifically, the hub support jig 24 is supported and fixed to the hub 3, and the outer ring support jig 37 is supported and fixed to the outer ring 2.

[0102] Next, the hub 3 is rotated by the rotary drive device 21 at a sufficiently slow rotation speed, specifically, 3s -1 While driving the hub 3 to rotate at a predetermined rotation speed as described below, the torque measuring device 22 measures the torque T acting on the outer ring 2. While measuring the torque T acting on the outer ring 2, the load applying device 20 presses the hub 3 radially inward to apply a radial load F1 to the hub 3, and gradually increase this radial load F1.

[0103] The reason why the hub 3 is rotated and driven at a sufficiently slow rotational speed is that if the rotational speed is too high, the change in preload due to temperature rise and the change in the stirring resistance of the lubricating grease become too large to be ignored. In other words, the speed term M v becomes too large to be ignored, making it impossible to perform proper preload measurement.

[0104] As shown in Fig. 3, when the radial load F1 is gradually increased, the torque T acting on the outer ring 2 increases gradually over a certain range as the major axis of the contact ellipse increases due to the increase in the radial load applied to the rolling elements 4a, 4b. Then, when the radial load F1 reaches a predetermined magnitude, the number of rolling elements 4a, 4b supporting the radial load decreases by one per row, causing a phenomenon in which the magnitude of the torque T acting on the outer ring 2 suddenly drops. This phenomenon in which the magnitude of the torque T acting on the outer ring 2 suddenly drops occurs repeatedly as the radial load F1 increases, but in this example, the torque measurement process S1 is promptly terminated after the above phenomenon first occurs.

[0105] The amount of decrease in torque T when the above phenomenon occurs is approximately equal to the torque T acting on the outer ring 2 immediately before the above phenomenon occurs divided by the number of rolling elements per row. In the hub unit bearing 1 to which preload is applied, even if the number of rolling elements 4a, 4b that support the load decreases by one per row, the change in the rolling element load acting on the rolling elements 4a, 4b is small, and the change in the major axis of the contact ellipse is also small. In addition, in this example, since the radial load F1 is applied to the center position between the rolling elements 4a, 4b in the double row, the change in the load factor ε occurs simultaneously between the rolling elements 4a in the axially outer row and the rolling elements 4b in the axially inner row. Therefore, it is easy to grasp the phenomenon of the torque T decreasing due to the occurrence of the above phenomenon.

[0106] (Preload calculation process S2) In the preload calculation step S2, the preload applied to the rolling elements 4a, 4b is calculated based on the radial load applied between the outer ring 2 and the hub 3 at the time when the torque of the hub unit bearing 1 suddenly drops.

[0107] In this example, the calculator 23 determines the preload applied to the rolling elements 4a, 4b based on the radial load F1 applied to the hub 3 at the time when the torque T acting on the outer ring 2 suddenly drops.

[0108] More specifically, in this example, the calculator 23 calculates the preload applied to the rolling elements 4a, 4b based on the radial load F1 applied to the hub 3 at the point when the torque T acting on the outer ring 2 suddenly drops, in other words, at the moment when the value of the load factor ε becomes 1, based on the relationship between the radial load F1 and the preload obtained in advance by theoretical calculation.

[0109] That is, it is known that the relationship between the axial load, radial load, and load factor corresponding to the preload for a rolling bearing can be found based on the Lundberg-Palmgren theory. Therefore, in this example, the calculator 23 calculates the preload applied to the rolling elements 4a and 4b by substituting the load factor ε=1 and the radial load F1 when the load factor ε=1 into a relational expression found in advance based on the specifications of the hub unit bearing 1.

[0110] However, when carrying out the preload measuring method for a hub unit bearing according to an embodiment of the present disclosure, the relationship between the radial load applied between the outer ring and hub and the preload applied to the rolling elements when the load factor ε = 1 can be determined in advance by experiment or simulation and stored as a map or formula in the memory of the calculator. In this case, the calculator inputs the radial load when the load factor ε = 1 measured in the torque measurement process into the map or formula stored in the memory, and outputs the preload applied to the rolling elements.

[0111] In the preload measuring method for a hub unit bearing of this example, a radial load F1 is applied between the outer ring 2 and the hub 3, the torque T of the hub unit bearing 1 is measured while increasing the radial load F1, and the preload applied to the rolling elements 4a, 4b is calculated based on the radial load F1 at the point when the torque T suddenly drops. Therefore, in the preload measuring method for a hub unit bearing of this example, it is not necessary to apply a large thrust load to the rolling elements 4a, 4b. Specifically, it is not necessary to apply a thrust load that exceeds the preload to the rolling elements 4a, 4b. Therefore, it is possible to prevent damage such as scratches and indentations from occurring to the rolling elements 4a, 4b, the outer ring raceways 5a, 5b, and the inner ring raceways 8a, 8b.

[0112] Furthermore, in the preload measuring method for a hub unit bearing of this embodiment, the torque measuring step S1 is quickly terminated after the torque T measured by the torque measuring device 22 first suddenly drops. Therefore, the preload measuring method for a hub unit bearing of this embodiment can prevent an excessively large radial load F1 from being applied between the outer ring 2 and the hub 3. From this perspective, damage such as scratches and indentations can be suppressed from occurring on the rolling elements 4a, 4b, the outer ring raceways 5a, 5b, and the inner ring raceways 8a, 8b. Also, the number of steps required to calculate the preload can be reduced.

[0113] In addition, the preload measurement method for the hub unit bearing of this example does not use an inflection point on the transition line of the axial relative distance between the outer ring and the hub as in the conventional preload measurement method described in JP 2021-148710 A, but obtains the preload applied to the rolling elements 4a, 4b based on the radial load F1 applied between the outer ring 2 and the hub 3. For this reason, it is not limited to the ball bearing type hub unit bearing 1 using balls as the rolling elements 4a, 4b, but can be applied to various types of hub unit bearings such as a tapered roller type hub unit bearing 1a using tapered rollers as the rolling elements 4c as shown in FIG. 6, a hybrid bearing type hub unit bearing using balls as the rolling elements on one axial side row and tapered rollers as the rolling elements on the other axial side row, and a multi-row type hub unit bearing with three or more rows.

[0114] Furthermore, in the preload measuring method for a hub unit bearing of this embodiment, the preload applied to the rolling elements 4a, 4b is found based on the radial load F1 at the time when the torque T measured by the torque measuring device 22 suddenly drops. In other words, the torque T is not used to calculate the preload applied to the rolling elements 4a, 4b. Therefore, according to the preload measuring method for a hub unit bearing of this embodiment, the influence of the seal torque can be eliminated. In other words, the preload measuring method for a hub unit bearing of this embodiment can be implemented regardless of the presence or absence of a seal device.

[0115] In this example, the radial load F1 is applied to the center position of the double row rolling elements 4a, 4b, and the change in the load factor ε occurs simultaneously between the rolling elements 4a in the axially outer row and the rolling elements 4b in the axially inner row, but the position where the radial load F1 is applied may be shifted in the axial direction from the center position of the double row rolling elements to make the radial loads applied to the rolling elements in the axially outer row and the rolling elements in the axially inner row different from each other, thereby causing a phenomenon in which the number of rolling elements supporting the radial load only in one axial row decreases, thereby capturing the phenomenon of a decrease in the torque T. In this case, the magnitude of the applied radial load can be kept small compared to the case where the radial load F1 is applied to the center position of the double row rolling elements 4a, 4b.

[0116] [Example 2] A second embodiment of the present disclosure will be described with reference to FIG.

[0117] In this example, a hybrid bearing type hub unit bearing 1b is used, in which balls are used as the axially outer row of rolling elements 4d and tapered rollers are used as the axially inner row of rolling elements 4e.

[0118] In the torque measuring step S1 of the preload measuring method for a hub unit bearing of this example, similar to the torque measuring step S1 of the preload measuring method for a hub unit bearing of the first example, the rotary drive device 21 drives and rotates the hub 3 at a predetermined rotational speed, and the load application device 20 presses the hub 3 in the radial direction to apply a radial load F1 to the hub 3, and while the radial load F1 is increased, the torque measuring device 22 measures the torque T acting on the outer ring 2. Then, after the first occurrence of a phenomenon in which the magnitude of the torque T acting on the outer ring 2 suddenly drops, the torque measuring step S1 is promptly terminated.

[0119] In the next preload calculation step S2, similar to the preload calculation step S2 of the first example of the preload measurement method for a hub unit bearing, the calculator 23 determines the preload applied to the rolling elements 4d, 4e based on the radial load F1 that was loaded on the hub 3 at the time when the torque T acting on the outer ring 2 suddenly decreased.

[0120] The load applying device 20 constituting the preload measuring device 19 of this example is configured to apply a radial load F1 to a portion whose axial position coincides with the center position between the double-row rolling elements 4d, 4e, similarly to the load applying device 20 of the first example. In addition, in the hybrid bearing type hub unit bearing 1b, the load capacity on the ball bearing side is smaller than the load capacity on the tapered roller bearing side. Therefore, in this example, in the process in which the loaded area decreases with an increase in the radial load F1, the number of rolling elements 4d present in the loaded area on the ball bearing side (axial outer row) decreases before the number of rolling elements 4e present in the loaded area on the tapered roller bearing side (axial inner row) decreases.

[0121] Therefore, in this example, the preload applied to the rolling element 4d is calculated by substituting the load factor ε=1 and the radial load F1 when the load factor ε=1 into a relational expression that has been determined in advance based on the specifications of the ball bearing.

[0122] However, by adjusting the axial position at which the radial load F1 is applied by the load application device in accordance with the ratio between the load capacity of the ball bearing side and the load capacity of the tapered roller bearing side, it is also possible to calculate the preload applied to the rolling element 4e by substituting the load factor ε=1 and the radial load F1 when the load factor ε=1 into the relational equation that has been determined in advance based on the specifications of the tapered roller bearing side.

[0123] The configuration and the effects of other parts of the second example are similar to those of the first example.

[0124] [Example 3] A third embodiment of the present disclosure will be described with reference to FIG.

[0125] In this example, a multi-row type hub unit bearing 1c for driving wheels is targeted.

[0126] The outer ring 2a has three rows of outer ring raceways 5c, 5d, and 5e on its inner circumferential surface.

[0127] The hub 3a has three rows of inner ring raceways 8c, 8d, and 8e on its outer circumferential surface, and also has a spline hole 50 penetrating in the axial direction at the center.

[0128] Each of the rolling elements 4f, 4g, 4h is composed of a ball, and is disposed between three rows of outer ring raceways 5c, 5d, 5e and three rows of inner ring raceways 8c, 8d, 8e, with multiple rolling elements in each row, so as to be freely rollable.

[0129] In the hub unit bearing 1c of this embodiment, the outermost row rolling element 4f and the innermost row rolling element 4h are provided with a contact angle that results in a back-to-back combination. Also, the intermediate row rolling element 4g, which is disposed in an intermediate row that is located between the outermost row and the innermost row in the axial direction, is provided with a contact angle that results in a back-to-back combination with respect to the outermost row rolling element 4h.

[0130] The outermost row rolling element 4f has a larger diameter than the intermediate row rolling elements 4g and the innermost row rolling elements 4h. The innermost row rolling element 4h has a larger diameter than the intermediate row rolling elements 4g. The pitch circle diameter of the outermost row rolling element 4f is larger than the pitch circle diameter of the intermediate row rolling elements 4g and smaller than the pitch circle diameter of the innermost row rolling element 4h.

[0131] In the torque measuring step S1 of the preload measuring method for a hub unit bearing of this example, similar to the torque measuring step S1 of the preload measuring method for a hub unit bearing of the first example, the rotary drive device 21 drives and rotates the hub 3a at a predetermined rotational speed, and the load application device 20 presses the hub 3a in the radial direction to apply a radial load F1 to the hub 3a, and while increasing the radial load F1, the torque measuring device 22 measures the torque T acting on the outer ring 2a. Then, when a phenomenon occurs in which the magnitude of the torque T acting on the outer ring 2a suddenly drops, the amount of drop in torque T and the radial load F1 are obtained.

[0132] The preload measuring method for a hub unit bearing of this example includes a determining step S3 for determining which row's load factor has decreased based on the amount of decrease in torque of the hub unit bearing 1c. Specifically, based on the amount of decrease in torque T acting on the outer ring 2a measured by the torque measuring device 22, it is determined which row's load factor ε has decreased.

[0133] In a multiple-row type hub unit bearing 1c, if the preload applied to the intermediate row rolling elements 4g, which have a small diameter and a small load capacity, becomes greater than the preload applied to the innermost row rolling elements 4h, the load will be concentrated on the intermediate row rolling elements 4g during use of the hub unit bearing 1c, which may reduce the bearing life, indentation resistance, and / or bearing rigidity. Therefore, it is important to determine which row's load factor ε is causing the sudden drop in torque T.

[0134] In the multi-row hub unit bearing 1c of this example, the diameter and number of rolling elements 4f, 4g, 4h are different for each row. Therefore, the load area decreases with an increase in radial load F1, and the amount of decrease in torque T caused by the decrease in the number of rolling elements 4f, 4g, 4h present in the load area varies depending on which row the number of rolling elements 4f, 4g, 4h has decreased in. Therefore, based on the amount of decrease in torque T, it is determined which row's load factor ε has decreased.

[0135] The relationship between the amount of decrease in torque T and the load factor ε for each row is obtained in advance by calculation, simulation, experiment, etc. Alternatively, since the amount of decrease in torque T is approximately equal to the torque T immediately before divided by the number of rolling elements in the row in which the number of rolling elements 4f, 4g, 4h has been reduced, it can also be determined based on this amount.

[0136] Then, in the preload calculation process S2, the preload applied to the rolling elements of the row is calculated by substituting the load factor ε=1 and the radial load F1 when the load factor ε=1 into a relational expression that has been determined in advance based on the specifications of the bearings of the row determined in the determination process S3.

[0137] When carrying out the preload measurement method for a hub unit bearing of this example, as in the first example, the torque measurement process S1 can be terminated promptly after the phenomenon in which the magnitude of the torque T acting on the outer ring 2a suddenly decreases for the first time, or the torque measurement process S1 can be terminated after the phenomenon occurs multiple times in order to determine the preload applied to the rolling elements of each row.

[0138] The configuration and the effects of other parts of the third example are similar to those of the first example.

[0139] The first to third examples of the embodiment of the present disclosure can be implemented in any suitable combination as long as no contradiction occurs. [Explanation of symbols]

[0140] 1, 1a, 1b, 1c Hub unit bearings 2, 2a Outer ring 3, 3a hub 4a, 4b, 4c, 4d, 4e, 4f, 4g, 4h rolling elements 5a, 5b, 5c, 5d, 5e outer raceway 6 Stationary Flange 7 Support hole 8a, 8b, 8c, 8d, 8e Inner raceway 9 Rotating flange 10 Pilot Division 11 Mounting hole 12 Stud 13. Inner Circle 14 Hub wheel 15 Small diameter stepped section 16 Step surface 17 Crimping part 18a, 18b retainer 19 Preload measuring device 20 Load bearing device 21 Rotational drive unit 22 Torque measuring device 23 Arithmetic unit 24 Hub support jig 25 Bearing device 26 Arm 27 Actuator 28 Large diameter section 29 Medium diameter part 30 Small diameter section 31 Recess 32 Electric motor 33 Motor output shaft 34a, 34b Joints (constant velocity joints) 35 Intermediate shaft 36 Driven shaft 37 Outer ring support jig 38 Torque Sensor 38a Shaft end 38b Arm 38c Load Cell 39 Fixed part 40 Small diameter section 41 Large diameter section 42 Recess 43 Hydrostatic bearing 44 Single row rolling bearing 45 Outer raceway 46 Outer Ring 47 Inner raceway 48 Inner Circle 49 Rolling elements 50 spline hole

Claims

1. an outer ring having a plurality of rows of outer ring raceways on an inner circumferential surface; A hub having a plurality of rows of inner ring raceways on its outer circumferential surface; a plurality of rolling elements, each of which is rollably disposed between the plurality of rows of outer ring raceways and the plurality of rows of inner ring raceways and to which a preload is applied; A method for measuring a preload of a hub unit bearing, comprising: a torque measuring process of applying a radial load between the outer ring and the hub and measuring the torque of the hub unit bearing while increasing the radial load; a preload calculation step of calculating the preload based on the radial load applied between the outer ring and the hub at a time when the torque suddenly decreases; A method for measuring a preload of a hub unit bearing comprising:

2. The multiple-row outer ring raceways are constituted by a double-row outer ring raceway, and the multiple-row inner ring raceways are constituted by a double-row inner ring raceway, 2. The preload measuring method for a hub unit bearing according to claim 1, wherein in the preload calculating step, the preload is calculated based on the radial load applied between the outer ring and the hub at a time when the torque first suddenly decreases.

3. The multiple-row outer ring raceways are constituted by a double-row outer ring raceway, and the multiple-row inner ring raceways are constituted by a double-row inner ring raceway, 2. A method for measuring a preload of a hub unit bearing as described in claim 1, wherein the rolling elements of one row of the plurality of rolling elements are constituted by balls, and the rolling elements of the other row of the plurality of rolling elements are constituted by tapered rollers.

4. The multiple-row outer ring raceways are composed of three or more rows of outer ring raceways, and the multiple-row inner ring raceways are composed of three or more rows of inner ring raceways, 2. The preload measuring method for a hub unit bearing according to claim 1, further comprising a determining step of determining which row's load factor has decreased based on the amount of decrease in the torque.

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