Hub unit bearing

Abstract

To provide a hub unit bearing capable of suppressing change of a gap between an encoder and a sensor due to press-fitting of a cap into an outer ring.SOLUTION: A cap has a metal core, and a synthetic resin cap body. The cap body has a bottomed cylindrical shape as a whole, and has a cylinder part and a bottom plate part that closes the opening of the cylinder part. The core has: a low-rigidity part in which an inboard side portion is connected and fixed to the cylinder part, an outboard side portion is press-fitted into the inboard end part of an outer ring, and an outboard side surface of the bottom plate part is provided radially inside the core; and a high-rigidity part provided radially inside the low-rigidity part.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a hub unit bearing used for rotatably supporting a vehicle wheel of an automobile with respect to a suspension device.

Background Art

[0002] A hub unit bearing with a rotation speed detection device, which is formed by combining a hub unit bearing that rotatably supports a vehicle wheel (driven wheel) of an automobile with respect to a suspension device and a rotation speed detection device for detecting the rotation speed of the wheel necessary for control such as ABS, has been widely used conventionally.

[0003] FIG. 13 is a longitudinal sectional view of a hub unit bearing provided with a cap having a sensor holder portion described in Patent Document 1. FIG. 14 is a longitudinal sectional perspective view showing a state where a magnetic sensor is attached to a cap having a sensor holder portion described in Patent Document 1. FIG. 15 shows a cross-sectional view of a cap having a sensor holder portion described in Patent Document 1.

[0004] As shown in FIG. 13, the hub unit bearing 111 of Patent Document 1 includes an inner ring 112 having an inner ring raceway surface 112A formed on its outer peripheral surface, an outer ring 113 having an outer ring raceway surface 113A formed on its inner peripheral surface, and bearings having rolling elements 114, 114 that roll between the inner ring raceway surface 112A and the outer ring raceway surface 113A. Further, the hub unit bearing 111 includes a magnetic encoder 116 that is located on the inboard side of the bearing and fixed to the inner ring 112 by a support member 117, in which N poles and S poles are alternately arranged in the circumferential direction at a constant interval, a magnetic sensor 100A that detects the rotation of the magnetic encoder 116 facing the magnetic poles of the magnetic encoder 116, and a seal member 115 disposed on the outboard side of the bearing.

[0005] Further, the hub unit bearing 111 includes a cap 101 attached to the outer ring 113 so as to seal the inboard side of the bearing, and the cap 101 has a sensor holder portion 103B that holds the magnetic sensor 100A.

[0006] As shown in Figures 13 to 15, the cap 101 consists of a core metal 102 made of steel plate formed into a cylindrical shape and pressed into the outer ring 113, and a cap body 103 made of synthetic resin. The cap body 103 has a main body portion 103A to which the core metal 102 and the outer circumference are joined, and a sensor holder portion 103B which holds an insert nut 110 into which a mounting bolt 100B for attaching the magnetic sensor 100A is screwed, and which has a sensor mounting hole 104 into which the magnetic sensor 100A is inserted.

[0007] Furthermore, with the cap 101 holding the magnetic sensor 100A, the magnetic sensor 100A faces the magnetic encoder 116, separated by a partition wall 100C with a thickness of 100t formed by the resin surface 105 facing the magnetic sensor 100A and its back surface 106. The back surface 106 of the resin surface 105 facing the magnetic sensor 100A is a removed portion 109 where the raised portion of the intermediate product has been removed. Here, the cap 101 is an injection molded product, and the core metal 102 and nut 110 are insert products. Note that synthetic resin is filled into the circumferential groove 110A of the nut 110, preventing the nut 110 from coming off. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2016-156493 [Overview of the project] [Problems that the invention aims to solve]

[0009] Regardless of whether the magnetic sensor 100A penetrates the cap 101 or not, the resin cap 101 is usually axially drawn by injecting molten resin into a cavity that combines a fixed mold and a movable mold, with a gate located near the center of the main body 103A (bottom plate). Ribs may be provided on the outboard side (bearing internal space side) of the cap 101 to allow the molten resin injected from the gate to spread easily throughout, and to ensure strength while preventing shrinkage by keeping the wall thickness of the molded product as uniform as possible.

[0010] The amount of shrinkage of the molten resin during molding is greater than the shrinkage due to the temperature change (coefficient of linear expansion) of the mandrel 102. Therefore, the main body 103A of the cap 101 molded in the above process is pulled radially from the mandrel 102 all around, becoming relatively flat. However, when the cap 101 is pressed into the inner circumference of the outer ring 113, the mandrel 102 shrinks, and the cap is pushed radially inward from the mandrel 102 all around. As shown by the dashed line in Figure 16, the main body 103A of the cap 101 becomes convex when viewed from the axially inward (inboard side). Although not shown, the main body 103A of the cap 101 may also become concave.

[0011] While deformation of the cap 101 is relatively minimal near the highly rigid sensor holder portion 103B, if the main body portion 103A becomes convex, the gap between the magnetic encoder 116 and the magnetic sensor 100A will widen, potentially weakening the magnetic flux signal and reducing the accuracy of the sensor output. Furthermore, if the main body portion 103A becomes concave, the magnetic encoder 116 and the magnetic sensor 100A may come into contact, potentially causing damage.

[0012] In view of the circumstances described above, the present invention aims to provide a hub unit bearing that can suppress changes in the gap between the encoder and the sensor due to the press-fitting of a cap onto the outer ring. [Means for solving the problem]

[0013] The above objective of the present invention is achieved by the following configuration. (1) An outer ring having a double row of outer ring raceway surfaces formed on its inner circumference, An inner ring having a double row of inner ring raceway surfaces formed on its outer surface, A plurality of rolling elements are arranged to roll freely between the double-row inner ring raceway surface and the double-row outer ring raceway surface, A cap is fixed to the inboard-side end of the outer ring and closes the opening on the inboard side of the outer ring, A hub unit bearing equipped with, The aforementioned cap has a metal core and a cap body made of synthetic resin. The cap body is a bottomed cylindrical shape, and has a cylindrical tube portion and a bottom plate portion that closes the opening of the tube portion. The core metal is bonded and fixed to the cylindrical portion at the inboard side, and press-fitted to the inboard end of the outer ring at the outboard side. The outboard side of the bottom plate portion is A low-rigidity portion is provided on the radially inner side of the core metal, A high-rigidity portion is provided radially inward of the low-rigidity portion, Having, Hub unit bearing. (2) The low-rigidity portion is a groove formed around the entire circumference, The aforementioned high-rigidity part is a protruding rib. (1) The hub unit bearing described above. (3) The rib is cut by the groove and is not connected to the core metal. (2) The hub unit bearing described above. (4) The axial dimension of the groove is greater than the radial dimension. (2) or (3) the hub unit bearing described above. (5) The ribs are Multiple circumferential ribs are arranged concentrically, spaced apart radially from each other, and each extends in the circumferential direction. A radial rib extending in the radial direction connects the radially adjacent circumferential ribs, Includes, A recessed rib groove is defined between adjacent circumferential ribs and radial ribs. The axial dimension of the groove is larger than the axial dimension of the rib groove. The hub unit bearing according to any one of (2) to (4).

Advantages of the Invention

[0014] According to the hub unit bearing of the present invention, it is possible to provide a hub unit bearing capable of suppressing a change in the gap between the encoder and the sensor due to press-fitting of the cap onto the outer ring.

Brief Description of the Drawings

[0015] [Figure 1] FIG. 1 is a cross-sectional view of a hub unit bearing according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of a cap according to a first embodiment. [Figure 3] FIG. 3 is an enlarged view of a main part of the outboard side surface of a cap according to a first embodiment. [Figure 4] FIG. 4 is a cross-sectional view of a cap according to a modification of the first embodiment. [Figure 5] FIG. 5 is a cross-sectional view of a cap according to a second embodiment. [Figure 6] FIG. 6 is an enlarged view of a main part of the outboard side surface of a cap according to a second embodiment. [Figure 7] FIG. 7 is a cross-sectional view of a cap according to a modification of the second embodiment. [Figure 8] FIG. 8 is an enlarged view of a main part of the outboard side surface of a cap according to a modification of the second embodiment. [Figure 9] FIG. 9 is a cross-sectional view of a cap according to a third embodiment. [Figure 10] FIG. 10 is an enlarged view of a main part of the outboard side surface of a cap according to a third embodiment. [Figure 11] FIG. 11 is a cross-sectional view of a cap according to a modification of the third embodiment. [Figure 12] FIG. 12 is an enlarged view of a main part of the outboard side surface of a cap according to a modification of the third embodiment. [Figure 13]Figure 13 is a longitudinal cross-sectional view of a hub unit bearing equipped with a cap having a sensor holder portion, as described in Patent Document 1. [Figure 14] Figure 14 is a vertical cross-sectional perspective view showing a magnetic sensor attached to a cap having a sensor holder portion, as described in Patent Document 1. [Figure 15] Figure 15 is a cross-sectional view of a cap having a sensor holder portion, as described in Patent Document 1. [Figure 16] Figure 16 shows the deformation of the cap as seen in Figure 15. [Modes for carrying out the invention]

[0016] [First Embodiment] A hub unit bearing according to the first embodiment of the present invention will be described in detail with reference to Figures 1 to 3. Figure 1 is a cross-sectional view of the hub unit bearing according to the first embodiment. Figure 2 is a cross-sectional view of the cap according to the first embodiment. Figure 3 is an enlarged view of the main part of the outboard side surface of the cap according to the first embodiment.

[0017] With respect to the hub unit bearing, throughout this specification and the claims, "outside" in the axial direction refers to the left side of Figure 1, which is the outer side in the width direction of the vehicle body when assembled to the automobile, and is also referred to as the "outboard side." Conversely, the right side of Figure 1, which is the central side in the width direction of the vehicle body, is referred to as "inside" in the axial direction, and is also referred to as the "inboard side."

[0018] The hub unit bearing 1 of this embodiment is for a driven wheel and mainly comprises an outer ring 2, an inner ring 3, and a plurality of rolling elements 4, 4.

[0019] The outer ring 2 has a stationary flange 7 on its outer circumference and double-row (2-row) outer ring raceway surfaces 8a and 8b on its inner circumference. When in use, the outer ring 2 does not rotate while supported by the suspension system by connecting and fixing the stationary flange 7 to the knuckle of the suspension system.

[0020] The inner ring 3 is composed of a hub ring 9 and an inner ring member 10, and is arranged coaxially (concentrically) with the outer ring 2 on the radially inner side of the outer ring 2.

[0021] The hub ring 9 is provided with a circular rotating flange 11 that extends radially outward from the axially outward (outboard side) opening of the outer ring 2, for supporting and fixing the wheel (drive wheel) and braking rotating members such as the disc rotor. Specifically, the rotating flange 11 is provided with a plurality of through holes 11a, and hub bolts 17 are serrated into each through hole 11a. Alternatively, the plurality of through holes 11a of the rotating flange 11 can be made into female threaded holes, and hub bolts can be screwed into them to support and fix the wheel (drive wheel) and braking rotating members such as the disc rotor.

[0022] Furthermore, the outer surface of the hub wheel 9 is provided with an inner ring raceway surface 12a of the outboard side row (one of the rows) in the portion facing the outer ring raceway surface 8a of the axially outer (outboard side) row of the outer ring 2. Additionally, a small diameter step portion 13 is provided at the axially inner end of the outer surface of the hub wheel 9 that faces the outer ring raceway surface 8b of the axially inner (inboard side) row of the outer ring 2.

[0023] The inner ring member 10 is provided with an inner ring raceway surface 12b of the inboard side row (the other row) on its outer circumferential surface. The inner ring member 10 is fitted onto the outer circumferential surface of the small-diameter stepped portion 13 of the hub wheel 9 with its outboard side end face abutting against the stepped surface of the small-diameter stepped portion 13, and is fixed to the hub wheel 9 by its inboard side end face being joined and fixed by the crimping portion 24.

[0024] The rolling elements 4, 4 are provided to roll freely in the space between the outer ring raceway surface 8a and the inner ring raceway surface 12a of the outboard side row, and in the space between the outer ring raceway surface 8b and the inner ring raceway surface 12b of the inboard row, while being held by a pair of retainers 6, 6.

[0025] A seal ring 5 is supported and fixed to the outboard end of the inner circumferential surface of the outer ring 2. The seal ring 5 closes the axial outer end opening of the internal space 18, which is located between the inner circumferential surface of the outer ring 2 and the outer circumferential surface of the hub ring 9 and contains a plurality of rolling elements 4, 4. The seal ring 5 slides against the large-diameter stepped portion 20 on the outboard side of the inner ring raceway surface 12a of the outer circumferential surface of the hub ring 9.

[0026] An annular encoder 14 is supported and fixed to the inboard end of the inner ring member 10. The encoder 14 consists of a support ring 26 and an encoder body 27. The support ring 26 is formed in an L-shape in cross-section and an annular shape by press-forming a magnetic metal plate, such as a ferritic stainless steel plate like SUS430 or a rolled steel plate like SPCC. The outboard portion of the support ring 26 is externally fitted and fixed to the inner ring member 10. The encoder body 27 is made of a permanent magnet formed by mixing a magnetic material such as ferrite powder into rubber or thermoplastic resin, and is attached and fixed to the inboard side of the support ring 26. The inboard side (detected surface) of the encoder body 27 is magnetized with alternating S poles and N poles at equal pitches in the circumferential direction.

[0027] A bottomed cylindrical cap 30 is fixed to the inboard end of the outer ring 2, which closes the opening on the inboard side of the outer ring 2.

[0028] The cap 30 has a metal core 40 and a cap body 50 made of synthetic resin.

[0029] The cap body 50 is manufactured in a bottomed cylindrical shape by injection molding (axial draw molding) of synthetic resin, and comprises a cylindrical tube portion 51 and a bottom plate portion 53 that closes the opening of the tube portion 51 facing in the axial direction.

[0030] The synthetic resin material that makes up the cap body 50 is, for example, a fiber-reinforced polyamide resin material which is made by compounding polyamide 66 resin with glass fiber, carbon fiber, or metal fiber as a fibrous reinforcing material. Furthermore, if necessary, the water resistance may be further improved by appropriately adding amorphous aromatic polyamide resin (modified polyamide 6T / 6I) or low water-absorbing aliphatic polyamide resin (polyamide 11 resin, polyamide 12 resin, polyamide 610 resin, polyamide 612 resin) to the polyamide resin.

[0031] The core metal 40 is made of metal such as stainless steel sheet or rolled steel sheet, has an L-shaped cross-section, and is formed in an annular shape overall. The outboard portion of the core metal 40 is press-fitted into the inboard end of the inner circumferential surface of the outer ring 2. The inboard portion of the core metal 40 is also joined and fixed to the cylindrical portion 51. That is, the flange portion, which is provided so as to bend radially outward from the inboard end of the core metal 40, is molded and fixed inside the cylindrical portion 51 of the cap body 50.

[0032] A protrusion 51a is provided around the entire circumference of the radially outer end of the outboard side surface of the cylindrical portion 51, projecting toward the outboard side. A locking groove 51b for engaging an O-ring (not shown) is provided radially between the protrusion 51a and the core metal 40.

[0033] The base plate portion 53 is generally constructed in a circular disc shape. A thickened portion 55 is provided at a position radially outward from the central axis of the base plate portion 53, which has a greater axial thickness than other parts (bulging outwards on both sides in the axial direction).

[0034] The thickened portion 55 has an insertion hole 57 that penetrates the thickened portion 55 axially in the portion facing the detection surface of the encoder body 27 in the axial direction. The insertion hole 57 is for inserting a sensor (not shown, but equivalent to the magnetic sensor 100A in Figures 13 and 14), and the inner circumferential surface of the insertion hole 57 has an inner diameter slightly larger than the outer diameter of the sensor.

[0035] An insert nut 59 is mold-fixed to the radially inner part of the thick-walled portion 55. The insert nut 59 is a bottomed cylindrical bag nut having a bottom at its outboard end, and a female thread is formed on its inner peripheral surface. Then, with the sensor inserted into the insertion hole 57, the sensor is fixed in the insertion hole 57 by screwing a bolt (not shown) that passes through the fixing hole provided in the flange portion of the sensor into the insert nut 59.

[0036] The outboard side surface of the bottom plate portion 53 has a groove portion 61 recessed over the entire circumference radially inside the mandrel 40, and a rib 63 protruding radially inside the groove portion 61.

[0037] The groove portion 61 is provided at a position radially away from the mandrel 40. The groove portion 61 is recessed from the outboard side surface of the bottom plate portion 53 toward the inboard side, and its axial dimension D is larger than the radial dimension R (see FIG. 3) (D > R). Thereby, the shrinkage of the mandrel 40 can be absorbed more.

[0038] The rib 63 includes a circumferential rib 63a extending in the circumferential direction and a radial rib 63b extending in the radial direction. The rib 63 of the present embodiment includes a plurality of circumferential ribs 63a arranged concentrically and spaced apart from each other in the radial direction, and a plurality of radial ribs 63b connecting the circumferential ribs 63a adjacent to each other in the radial direction.

[0039] A rib groove 65, which is a concave groove toward the inboard side, is defined between adjacent circumferential ribs 63a and radial ribs 63b. In the present embodiment, the axial dimension D of the groove portion 61 is set larger than the axial dimension d of the rib groove 65 (d < D). Thereby, the shrinkage of the mandrel 40 can be absorbed more by the groove portion 61.

[0040] Furthermore, in the present embodiment, among the plurality of circumferential ribs 63a, the circumferential rib 63a located most radially outside is connected (adjacent) to the groove portion 61 in the radial direction. That is, the rib 63 is cut by the groove portion 61 and is not connected to the mandrel 40 located radially outside.

[0041] Thus, the cap 30 has, in order from the radially inner side to the radially outer side, a high-rigidity section made of ribs 63, a low-rigidity section made of grooves 61, and a high-rigidity section made of core metal 40. Therefore, even if the core metal 40 shrinks when the cap 30 is press-fitted onto the inner circumferential surface of the outer ring 2, the high-rigidity section made of ribs 63 does not shrink, and the shrinkage is absorbed by the radial contraction of the grooves 61. As a result, it is possible to suppress changes in the gap between the encoder 14 and the sensor due to the press-fitting of the cap 30 onto the outer ring 2.

[0042] [Modified version of the first embodiment] Figure 4 is a cross-sectional view of a modified cap according to the first embodiment.

[0043] In this embodiment, the axial dimension d of the rib groove 65 is approximately equal to the axial dimension D of the groove portion 61. Therefore, the thickness of the portion of the bottom plate 53 in which the groove portion 61 is formed is thicker than in the first embodiment. Although the effect of absorbing the shrinkage caused by press-fitting the cap 30 into the outer ring 2 with the radial shrinkage of the groove portion 61 is reduced, the moldability of the radially outer side of the cap 30 can be improved when the gate is placed towards the center of the cap 30 during molding.

[0044] [Second Embodiment] Figure 5 is a cross-sectional view of the cap according to the second embodiment. Figure 6 is an enlarged view of the main part of the outboard side of the cap according to the second embodiment.

[0045] In this embodiment, the circumferential rib 63a located furthest radially outward among the multiple circumferential ribs 63a is not radially connected to (not adjacent to) the groove 61, while the radial rib 63b is radially connected to the groove 61. In this structure as well, the rib 63 is cut by the groove 61 and is not connected to the core metal 40 located radially outward.

[0046] In this embodiment, by providing radial ribs 63b up to the inner diameter of the groove 61, the moldability of the cap 30 is maintained, the rigidity of the high-rigidity section provided by the ribs 63 is maintained to a certain extent, and the ease with which the cap 30 can be released from the movable mold after injection molding is improved.

[0047] In other words, injection molding is performed by injecting molten resin into a cavity formed by combining a fixed mold and a movable mold, through a gate (the trapezoidal portion indicated by the symbol G in Figure 5) provided in the fixed mold. Due to the shrinkage of the resin during molding, the molded product is removed from the fixed mold while locked to the outer surface of the movable mold, and is then detached from the movable mold by being pushed by an ejector pin that protrudes as the movable mold moves. The locking force between the molded product and the movable mold is high because of the large diameter, which results in a large amount of shrinkage during molding. Furthermore, in the examples shown in Figures 1 to 4, the contact area between the radially outer circumferential rib 63a, which has a large circumferential distance, and the movable mold increases, resulting in higher resistance to detachment. This increases the pressing force of the ejector pin, which may cause deformation of the molded product.

[0048] In contrast, in this embodiment, the outermost circumferential rib 63a is eliminated, which reduces the contact area with the movable mold, lowers the pressing force of the ejector pin, and suppresses deformation of the molded product.

[0049] [Modified version of the second embodiment] Figure 7 is a cross-sectional view of a modified cap according to the second embodiment. Figure 8 is an enlarged view of the main part of the outboard side of the cap according to the modified cap of the second embodiment.

[0050] In this embodiment, the axial dimension d of the rib groove 65 is approximately equal to the axial dimension D of the groove portion 61. Therefore, the thickness of the portion of the bottom plate 53 in which the groove portion 61 is formed is thicker than in the second embodiment. Although the effect of absorbing the shrinkage caused by press-fitting the cap 30 into the outer ring 2 with the radial shrinkage of the groove portion 61 is reduced, the moldability of the radially outer side of the cap 30 can be improved when the gate is placed towards the center of the cap 30 during molding.

[0051] [Third Embodiment] Figure 9 is a cross-sectional view of the cap according to the third embodiment. Figure 10 is an enlarged view of the main part of the outboard side of the cap according to the third embodiment.

[0052] In this embodiment, the radial rib 63b that connects to the groove 61 in the second embodiment (see Figures 5-6) is eliminated. Therefore, a second groove 67 is formed between the outermost circumferential rib 63a and the groove 61. In this structure as well, the rib 63 is cut by the groove 61 and the second groove 67 and is not connected to the core metal 40 located radially outward. Here, the axial dimension D of the groove 61 is greater than the axial dimension L of the second groove 67 (D>L), and the axial dimension L of the second groove 67 is approximately equal to the axial dimension d of the rib groove 65.

[0053] According to this embodiment, compared to the second embodiment, the outermost radial rib 63b is eliminated, which reduces the pressing force of the ejector pin and suppresses deformation of the molded product.

[0054] [Modified version of the third embodiment] Figure 11 is a cross-sectional view of a modified cap according to the third embodiment. Figure 12 is an enlarged view of the main part of the outboard side of the cap according to the modified cap of the third embodiment.

[0055] In this embodiment, the axial dimension d of the rib groove 65 is approximately equal to the axial dimension D of the groove portion 61. Furthermore, the axial dimension D of the groove portion 61 is approximately equal to the axial dimension L of the second groove portion 67. Therefore, the groove portion 61 and the second groove portion 67 are smoothly connected radially and formed integrally.

[0056] In this configuration, the thickness of the portion of the bottom plate 53 in which the groove 61 is formed is thicker than in the third embodiment. Therefore, although the effect of absorbing the shrinkage caused by press-fitting the cap 30 into the outer ring 2 by the radial shrinkage of the groove 61 is reduced, the moldability of the radially outer side of the cap 30 can be improved when the gate is placed towards the center of the cap 30 during molding.

[0057] Furthermore, the present invention is not limited to the embodiments described above, and can be modified and improved as appropriate.

[0058] For example, in the embodiment described above, the insertion hole 57 for inserting the sensor was described as a through hole that penetrates the thickened portion 55, but the insertion hole 57 may not be a through hole.

[0059] Furthermore, the cap 30 does not necessarily have to have a function of supporting the sensor, and the present invention is also suitable, for example, when it is desired to guarantee the axial position of the end face of the cap 30. [Explanation of symbols]

[0060] 1 Hub unit bearing 2 Outer ring 3. Inner Ring 4 Rolling elements 5 Seal ring 6 Cage 7 Stationary flange 8a, 8b Outer ring raceway surface 9 Hub Wheels 10 Inner ring member 11 Rotation side flange 12a, 12b Inner ring raceway surface 13 Small diameter stepped section 14 encoders 18 Interior space 20 Large diameter stepped section 24 Crimping section 26 Support ring 27 Encoder unit 30 caps 40 Mandrel 50 Cap Body 51 Cylinder part 51a Convex part 51b Locking groove 53 Bottom plate part 55 Thick wall part 57 Insertion hole 59 Insert Nut 61 Groove 63 Ribs 63a Circumferential ribs 63b Radial rib 65 Rib groove 67 Groove

Claims

1. An outer ring having a double-row outer ring raceway formed on its inner circumference, An inner ring having a double row of inner ring raceway surfaces formed on its outer surface, A plurality of rolling elements are arranged to roll freely between the double-row inner ring raceway surface and the double-row outer ring raceway surface, An encoder is fixed to the inboard end of the inner ring, A cap is fixed to the inboard-side end of the outer ring and closes the opening on the inboard side of the outer ring, The sensor is supported by the aforementioned cap, A hub unit bearing equipped with, The aforementioned cap has a metal core and a cap body made of synthetic resin. The cap body is a bottomed cylindrical shape, and has a cylindrical tube portion and a bottom plate portion that closes the opening of the tube portion. The core metal is bonded and fixed to the cylindrical portion at the inboard side, and press-fitted to the inboard end of the outer ring at the outboard side. The bottom plate portion is provided with an insertion hole for inserting the sensor in the portion facing the encoder in the axial direction. The outboard side of the bottom plate portion is A low-rigidity portion is provided on the radially inner side of the core metal, A high-rigidity portion is provided radially inward of the low-rigidity portion, It has, The aforementioned high-rigidity portion is a rib integrally formed protruding from the outboard side surface of the bottom plate portion. The rib includes a circumferential rib extending in the circumferential direction and a radial rib extending in the radial direction. The low-rigidity portion is a groove recessed around its entire circumference. The rib is cut by the groove and is not connected to the core metal. The groove is positioned so as to be radially spaced apart from the insertion hole for inserting the sensor. Hub unit bearing.

2. The circumferential ribs are continuously provided as protrusions around the entire circumference of the outboard side surface of the bottom plate. The hub unit bearing according to claim 1.

3. The aforementioned rib is A plurality of circumferential ribs are arranged concentrically, spaced apart radially from each other, and each extends in the circumferential direction, A radial rib extending in the radial direction connects the radially adjacent circumferential ribs, including, A hub unit bearing according to claim 1 or 2.

4. The axial dimension of the groove is larger than the radial dimension. The hub unit bearing according to claim 1.

5. A recessed rib groove is defined between adjacent circumferential ribs and radial ribs. The axial dimension of the groove is larger than the axial dimension of the rib groove. The hub unit bearing according to claim 3.

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