JP4271093B2 - Wheel bearing device with variable preload mechanism - Google Patents

Description

  The present invention relates to a wheel bearing device with a preload variable mechanism that can be variably set to an optimal preload amount in accordance with the running state of a vehicle.

  In vehicles such as automobiles, the power transmission device that transmits engine power to wheels not only transmits power from the engine to the wheels, but also bounces when driving on rough roads, and the radial direction and axis from the wheels that occur when the vehicle turns. It is necessary to allow directional displacement and moment load. For this reason, in such a power transmission device, one end of the drive shaft interposed between the engine side and the drive wheel side is connected to the differential through a sliding type constant velocity joint, and the other end is fixed. The wheel is connected to a wheel through a wheel bearing device including a constant velocity joint.

In the wheel bearing device, a predetermined bearing preload has been conventionally applied in order to ensure a desired bearing rigidity. At that time, if the bearing preload is large, the bearing rigidity is improved, and the tilt angle of the bearing with respect to radial / axial displacement, moment load, etc. can be reduced, and the brake rotor tilt that occurs when the vehicle turns is suppressed. There is an advantage that you can. On the other hand, when the bearing preload amount is large, the rotational torque of the bearing increases, friction loss increases, and fuel consumption deteriorates. Conversely, when the bearing preload is small, the rotational torque of the bearing is reduced and friction loss is reduced, but the bearing rigidity is reduced.
Considering the running state of the car, it is desired to reduce the rotational torque as much as possible during straight running and to increase the bearing rigidity as much as possible during turning to suppress the tilt of the brake rotor.

Conventionally, a variable preload bearing unit as shown in FIG. 8 is known as one that variably sets a preload amount of a bearing (for example, Patent Document 1). In this variable preload bearing unit, an even number of rolling bearings 34 are held by the outer cylindrical portion 36 and the inner cylindrical portion 32, and voltage is applied from the voltage control means 43 to the piezoelectric element 42 disposed on the axial end surface of the inner cylindrical portion 32, for example. Is controlled and applied. The cylindrical portions 32 and 36 are sandwiched and fixed together with the piezoelectric element 42 by a screw 38 into which the inner cylindrical portion 32 is fitted and a bearing support member including a base 37 to which the screw 38 is screwed. The preload amount of the bearing is variably set by the expansion / contraction of the piezoelectric element 42 by the voltage control means 43.
JP-A-11-223216

  However, this variable preload bearing unit simply suppresses fluctuations in the preload amount of the two sets of rolling bearings set in the initial stage due to temperature changes by controlling the piezoelectric element. This is different from the one that variably sets the optimal preload amount according to the running state of the vehicle. That is, in the wheel bearing device, the straight traveling and turning of the vehicle are repeated at random, and the running state constantly changes, and the load applied to the device constantly changes with the change of the running state. For this reason, in the configuration of the preload variable bearing unit that suppresses the fluctuation of the preload amount of the rolling bearing due to the temperature change by controlling the piezoelectric element, the wheel bearing device is always set to the optimum preload amount according to the running state of the vehicle. Cannot be variably set. Further, the amount of preload required for the wheel bearing device is large, and the piezoelectric element cannot be used because a load cannot be produced.

  An object of the present invention is to provide a wheel bearing device with a preload variable mechanism that can be variably set to an optimum preload amount in accordance with the running state of a vehicle.

The wheel bearing device with a variable preload mechanism according to the present invention includes an outer member having a double-row raceway surface on an inner periphery, an inner member having a raceway surface facing these raceway surfaces, and an opposing raceway surface. And a detecting means for detecting the running state of the vehicle, in a wheel bearing for rotatably supporting the wheel with respect to the vehicle body, and a preload variable mechanism for changing the preload to the bearing. And means for causing the variable preload mechanism to perform a preload changing operation based on the output of the detecting means.
According to this configuration, since the variable preload mechanism performs the preload changing operation according to the traveling state of the vehicle detected by the detecting means, the amount of preload applied to the bearing can be optimally variably set according to the traveling state of the vehicle. For example, in a traveling state in which straight travel and turning of the vehicle always change randomly, the preload amount of the wheel bearing device can be variably set to be small during straight traveling and large during cornering. it can. As a result, it is possible to improve fuel efficiency and life by reducing friction loss during straight traveling. Moreover, the inclination of the brake rotor at the time of cornering can be suppressed, and traveling stability can be improved.

Ing in the front Kigaikata member and the outer ring member and the outer ring. The outer ring member has a vehicle body mounting flange integrally on the outer periphery, and an outboard side row raceway surface is formed on the inner circumference, and a cylinder extending in the axial direction from the outboard side raceway surface via a step surface. The outer ring fitting surface is planar and has a larger diameter than the raceway surface. The outer ring is formed with an inboard side raceway surface and is fitted to the outer ring fitting surface of the outer ring member. The variable preload mechanism is interposed between the step surface of the outer ring member and the end surface of the outer ring.
The variable preload mechanism is a cam mechanism that expands and contracts in the axial direction by relative rotation of a pair of cam surfaces facing in the axial direction via a ball, and rotates the outer ring with respect to the outer ring member, whereby the cam mechanism but works, it is assumed capable of changing the preload.

In this configuration, when the outer ring is rotated, the pair of cam surfaces interposing the balls in the preload variable mechanism rotate relative to each other so that the preload variable mechanism expands and contracts in the axial direction. The axial interval between the outer ring member on which the surface is formed and the outer ring on which the raceway surface of the inboard side row is formed changes, whereby the preload applied to the bearing can be changed.
In addition, since a cam mechanism that expands and contracts in the axial direction by the relative rotation of a pair of cam surfaces facing in the axial direction via the ball can be used, a large axial force can be generated with a small force, and the inside of the wheel bearing device Preload variable mechanism can be housed in a lightweight and compact.

In this configuration, the outer ring has a rotationally transmitted portion that protrudes toward the inboard side of the outer ring member, and the outer ring that causes the preload variable mechanism to change the preload via the rotationally transmitted portion. It shall receive the driving force of the rotation. The rotation receiving part is, for example, a gear.
Thus, by providing the outer ring with the rotation transmitted portion that protrudes toward the inboard side of the outer ring member, the rotation of the drive source can be given to the outer ring with a simple configuration.

In the present invention, the means for detecting the traveling state of the vehicle is capable of discriminating between straight traveling and turning traveling of the vehicle, and the means for causing the preload varying mechanism to perform a preload changing operation proceeds straight ahead. The preload changing operation may be performed so as to be small during traveling and large during turning.
By providing such a traveling state detection means, it is possible to change the preload according to straight traveling and turning traveling. The discrimination between the straight running and the turning run by the detection means may be performed by binary values, or by a plurality of steps or continuous values. By reducing the preload amount during straight traveling and increasing during turning, the fuel consumption and life are improved by reducing friction loss during straight traveling as described above, and the running stability during turning is also improved. Can be made.

In the present invention, the means for causing the preload varying mechanism to perform the preload changing operation sets the initial preload amount to a small value, and keeps the initial preload amount during straight traveling in accordance with the traveling state of the vehicle. May increase the amount of preload.
As a result, it is not necessary to drive for changing the preload amount during straight running, which occupies most of the travel time, and the drive for changing the preload amount can be reduced. Further, the control for changing the preload amount is also simplified.

The means for causing the preload variable mechanism to perform a preload changing operation variably sets the preload so that the bearing clearance is −10 to 0 μm when the vehicle is running straight and the bearing clearance is −50 to −10 μm when the vehicle is turning. It is good to do.
Setting excessive bearing rigidity due to excessive preload amount will lead to a decrease in efficiency due to an increase in rotational torque, etc., and a decrease in bearing life. However, if it is set within the above bearing clearance range, an appropriate bearing preload will be maintained. It is possible to extend the bearing life. Therefore, the bearing device can be downsized as compared with the case of the conventional example.

The wheel bearing device with a variable preload mechanism according to the present invention includes an outer member having a double-row raceway surface on an inner periphery, an inner member having a raceway surface facing these raceway surfaces, and an opposing raceway surface. And a detecting means for detecting the running state of the vehicle, in a wheel bearing for rotatably supporting the wheel with respect to the vehicle body, and a preload variable mechanism for changing the preload to the bearing. When, only set and means for causing a preload changing operation to the preload variable mechanism by an output of the detection means, the outer member is in the outer ring member and the outer ring, the outer ring member, a body mounted on the outer periphery The track surface of the outboard side row is formed on the inner periphery with a flange integrally, and is a cylindrical surface extending in the axial direction from the outboard side track surface through the step surface and having a diameter larger than that of the track surface. It has an outer ring fitting surface, and the outer ring is arranged on the inboard side row. A road surface is formed and is fitted to the outer ring fitting surface of the outer ring member, and the preload variable mechanism is interposed between the step surface of the outer ring member and an end surface of the outer ring, and the preload variable mechanism. Is a cam mechanism that expands and contracts in the axial direction by relative rotation of a pair of cam surfaces facing in the axial direction via the ball, and the cam mechanism operates by rotating the outer ring with respect to the outer ring member, In order to change the preload, the outer ring has a rotationally transmitted portion that protrudes toward the inboard side of the outer ring member, and the preload changing mechanism operates to change the preload via the rotationally transmitted portion. Therefore, it is possible to variably set the optimal preload amount in accordance with the traveling state of the vehicle. Therefore, for example, it is possible to improve fuel efficiency and life by reducing friction loss during straight traveling, and improve traveling stability during turning.

A first embodiment of the present invention will be described with reference to FIGS. The wheel bearing device with a preload varying mechanism of this embodiment is an example applied to a wheel bearing for driving wheel support, which is a third generation inner ring rotating type. In this specification, the side closer to the outer side in the vehicle width direction of the vehicle when attached to the vehicle is referred to as the outboard side, and the side closer to the center of the vehicle is referred to as the inboard side. In FIG. 1, the left side is the outboard side and the right side is the inboard side.
In FIG. 1, this wheel bearing device includes an outer member 1 having double-row raceway surfaces 4 on the inner periphery, an inner member 2 having raceway surfaces 5 on the outer periphery, which respectively face the raceway surfaces 4, A double row rolling element 3 interposed between the double row raceway surfaces 4 and 5. Each of the raceway surfaces 4 and 5 has a circular arc shape in cross section, and each of the raceway surfaces 4 and 5 is formed so that the contact angle is back to back. The rolling elements 3 are formed of balls and are held by the cage 6 for each row.

  The outer member 1 is a member on the fixed side, and is provided with an outer ring member 7 integrally having a vehicle body mounting flange 1a on the outer periphery and an inner diameter of the end portion on the inboard side of the outer ring member 7 It consists of the outer ring 8 of the body. An outboard side raceway surface 4 is formed on the inner circumference of the outer ring member 7, and an inboard side raceway surface 4 is formed on the inner circumference of the outer ring 8. The vehicle body mounting flange 1a is fastened to a knuckle installed in a vehicle body (not shown) with a plurality of bolts (not shown) in the circumferential direction.

The inner periphery of the outer ring member 7 has a cylindrical surface extending in the axial direction from the outboard side raceway surface 4 via the step surface 7 a and has an outer ring fitting surface 7 b having a larger diameter than the raceway surface 4. The outer ring 8 is fitted to the outer ring fitting surface 7b so as to be relatively rotatable.
A variable preload mechanism 9 is provided between the stepped surface 7a of the outer ring member 7 and the end surface of the outer ring 8 facing the stepped surface 7a so that the preload can be changed.

The variable preload mechanism 9 includes a ring-shaped fixing member 10 that is fitted and fixed over a part of the outer ring fitting surface 7 b from the step surface 7 a on the inner periphery of the outer ring member 7, and the fixing member 10 of the outer ring 8. A ring-shaped rotating member 11 fixed to the opposing end surfaces, a pair of cam surfaces 10a, 11a formed on these members 10, 11 facing each other in the axial direction, and a ball 12 interposed between both cam surfaces 10a, 11a It is a cam mechanism consisting of That is, the preload variable mechanism 9 is a torque cam having a ball ramp mechanism.
Specifically, the variable preload mechanism 9 includes a plurality (three in this case) of groove-shaped cams extending along the circumferential direction as shown in FIG. 3 on the surfaces of the fixed member 10 and the rotating member 11 that are opposed to each other in the axial direction. Surfaces 10a and 11a are formed. As shown in FIG. 2, the cam surfaces 10a and 11a are gradually deepened from both ends toward the intermediate portion, and the ball 12 is sandwiched between each pair of opposing cam surfaces 10a and 11a. Due to the relative rotation of the cam surfaces 10a and 11a, the entire preload variable mechanism 9 expands and contracts in the axial direction.

  As shown in FIG. 1, the outer ring 8 to which the rotating member 11 is fixed is integrally formed with a gear portion 8 a on an outer periphery of an end portion that protrudes inward from the outer ring member 7. The rotation of the motor 13 serving as a drive source for changing the preload amount is transmitted to the outer ring 8 through the gear 14 meshed with the gear portion 8a.

  The inner member 2 is a member on the rotation side, and includes a hub wheel 2A having a wheel mounting flange 2a, and a separate inner ring 2B fitted to the outer diameter of the end portion on the inboard side of the hub wheel 2A. Each row of raceway surfaces 5 is formed on the hub wheel 2A and the inner ring 2B. The inner ring 2B is clamped and fixed in the axial direction with respect to the hub wheel 2A by a crimping portion 2Aa provided at the inboard side end of the hub wheel 2A. The open end portions on the outboard side and the inboard side of the annular space formed between the inner and outer members 2 and 1 are sealed with contact-type seals 15 and 16, respectively. A stem portion (not shown) of the constant velocity joint outer ring is inserted into and connected to the inner diameter hole 17 at the center of the hub wheel 2A.

  As shown in FIG. 1, in an automobile (ECU) 18 of an automobile equipped with this wheel bearing device, for example, a running state detecting means 19 for detecting the running state of the vehicle, and the output of the detecting means 19 Preload change control means 20 is provided for causing the preload variable mechanism 9 to perform a preload change operation. The traveling state detection means 19 is based on detection signals from the wheel rotation sensors 21A, 21B... And the wheel load sensors 22A, 22B. This is to detect the distinction and degree. The preload change control means 20 causes the preload variable mechanism 9 to perform a preload change operation by controlling the motor 13 to rotate in the forward and reverse directions based on the running state detected by the running state detecting means 19.

  Next, the preload changing operation of the preload variable mechanism 9 in the wheel bearing device with the preload variable mechanism will be described. The initial value of the preload amount for the wheel bearing is set small. That is, in the preload variable mechanism 9, the ball 12 is sandwiched between the deep portions of the cam surfaces 10a and 11a, and the entire preload variable mechanism 9 is in a state of being contracted in the axial direction. At this time, the axial interval between the outer ring member 7 formed with the raceway surface 4 on the outboard side row of the outer member 1 and the outer ring 8 formed with the raceway surface 4 on the inboard side row becomes small. ing.

  When the traveling state detection means 19 determines that the vehicle is in a straight traveling state from the detection signals of the wheel rotation sensors 21A, 21B,... The control means 20 does not output a control signal to the motor 13, and the preload varying mechanism 9 does not perform the preload changing operation. For this reason, the preload amount of the bearing is kept at a small initial value. As a result, during straight running, the rotational torque of the bearing is reduced, friction is reduced, and fuel efficiency is improved.

  When the traveling state detecting means 19 determines that the vehicle has shifted to turning from the detection signals of the wheel rotation sensors 21A, 21B... And the wheel load sensors 22A, 22B. A signal is output, and the motor 13 is rotated forward, for example. As a result, the outer ring 8 of the outer member 1 rotates and relative rotation occurs between the fixed member 10 and the rotating member 11 in the preload variable mechanism 9, and the ball 12 is sandwiched between the shallow portions of the cam surfaces 10a and 11a. As a result, the entire preload variable mechanism 9 is extended in the axial direction. As a result, a load separating in the axial direction acts on the outer ring member 7 and the outer ring 8 of the outer member 1, and the amount of preload acting on the bearing increases. When the bearing preload amount is high, the bearing rigidity is improved, so that the inclination angle of the bearing with respect to radial / axial displacement and moment load can be reduced, and the inclination of the brake rotor that occurs when the vehicle turns can be suppressed.

  When the vehicle returns from turning to straight running, the preload change control means 20 controls the motor 13 in reverse rotation based on a detection signal from the running condition detection means 19 that detects the running condition. As a result, the outer ring 8 rotates in the reverse direction, the entire preload variable mechanism 9 is reduced in the axial direction, and the amount of preload acting on the bearing returns to the initial value. As a result, the rotational torque of the bearing is reduced, friction is reduced, and fuel efficiency is improved. When the vehicle repeats straight traveling and turning, the variable preload mechanism 9 variably adjusts the preload amount of the bearing as described above, and is set to a preload amount suitable for the traveling state.

In addition, since a preload is applied to the wheel bearing device, the bearing gap becomes a minus gap due to elastic displacement in the axial direction. When the wheel bearing device is a mass-produced product, the tolerance of the bearing gap is normally set in the range of −30 to 0 μm in consideration of the manufacturing tolerance range and the bearing life, and corresponds to this bearing gap. A preload amount is set. Therefore, in this embodiment, the preload change control means 20 for causing the preload variable mechanism 9 to perform the preload changing operation is a preload amount corresponding to a bearing gap of −10 to 0 μm when the vehicle running state is linear running, and a bearing gap when turning. The preload amount is variably set so that the preload amount corresponds to −50 to 10 μm.
If the preload amount becomes too large and excessive bearing rigidity is set, the efficiency will decrease due to an increase in rotational torque, etc. and the bearing life will be reduced. However, as described above, an appropriate bearing preload (that is, an appropriate bearing gap) If this is to be maintained, the bearing life can be extended, so that the bearing device can be made smaller than in the case of the conventional example.

  FIG. 4 shows another embodiment of the present invention. The wheel bearing device with a variable preload mechanism according to this embodiment is obtained by integrating the rotating member 11 of the variable preload mechanism 9 with the outer ring 8 in the first embodiment shown in FIGS. That is, the rotating member 11 which is an independent part is omitted, and the cam surface 11a facing the cam surface 10a of the fixing member 10 is formed on the end surface of the outer ring 8 which faces the fixing member 10 of the preload variable mechanism 9 in the axial direction. It is. Also in this case, the cam surface 11a is the same as the cam surface 11a of the rotating member 11 in the first embodiment.

  Thus, by integrating the rotating member 11 of the preload variable mechanism 9 with the outer ring 8, the influence of the rotation play between the outer ring 8 and the rotating member 11 can be eliminated, and the variable control of the preload amount is ensured. It can be performed. Other configurations and effects are the same as those in the first embodiment.

  FIG. 5 shows another embodiment of the present invention. The wheel bearing device with a preload variable mechanism according to this embodiment is obtained by further integrating the fixing member 10 of the preload variable mechanism 9 with the outer ring member 7 in the embodiment shown in FIG. That is, the fixing member 10 which is an independent part is omitted, and the cam surface 10 a facing the cam surface 11 a of the outer ring 8 is formed on the step surface 7 a of the outer ring member 7 facing the cam surface 11 a of the outer ring 8. . Also in this case, the cam surface 10a is the same as the cam surface 10a of the fixing member 10 in the first embodiment.

  In this way, not only the rotating member 11 of the preload varying mechanism 9 is integrated with the outer ring 8 but also the fixing member 10 is integrated with the outer ring member 7, so that not only between the outer ring 8 and the rotating member 11. Further, the influence of the rotation play between the outer ring member 7 and the fixing member 10 can be eliminated, and the variable control of the preload amount can be performed more reliably. Other configurations and effects are the same as those in the first embodiment.

FIG. 6 shows a reference proposal example of the present invention. This wheel bearing device with a variable preload mechanism, in the first embodiment shown in FIGS. 1 to 3, has the inner member 2 as an integral member of only the hub wheel, and a double row track of the inner and outer members 2 and 1. The surfaces 4 and 5 have a contact angle opposite to that in the case of the first embodiment, that is, an inverted half-shaped DF set, that is, face-to-face alignment.
The preload variable mechanism 9A includes a ring-shaped fixing member 10 fixed to an end surface of the outer ring 8 facing the inboard side, and is disposed on the inboard side of the fixing member 10 and is arranged on the outer ring fitting surface 7b of the outer ring member 7. The rotating member 11 that fits in a rotatable manner and the ball 12 are used. This preload variable mechanism 9A is also a torque cam having a ball ramp mechanism, as in the first embodiment. Specifically, the preload variable mechanism 9A has a cam surface 10a formed on a surface of the fixed member 10 facing the rotating member 11 in the axial direction, and a cam surface 11a formed on the surface of the rotating member 11 facing the fixed member 10 in the axial direction. These cam surfaces 10a and 11a face each other in the axial direction via the balls 12.

In this reference proposal example , the outer ring 8 is fitted to the outer ring fitting surface 7b of the outer ring member 7 so as to be axially displaceable and non-rotatable. The configuration of the cam surfaces 10a and 11a and the relationship between the cam surfaces 10a and 11a and the ball 12 are the same as those in the first embodiment described above with reference to FIGS. A gear portion 11 b that meshes with a gear 14 that is rotationally driven by the motor 13 is integrally formed on the outer periphery of the inboard side end portion of the rotating member 11. Although the travel state detection means, the preload change control means, and the like provided in the ECU are not shown in the drawing, these configurations are the same as those in the first embodiment, and the description thereof is omitted here.

Also in this reference proposal example , the rotation of the rotating member 11 of the preload variable mechanism 9A causes the entire preload variable mechanism 9A to expand and contract in the axial direction. That is, the variable preload mechanism 9A is contracted in the axial direction during the initial state and when the vehicle is traveling straight, and the amount of preload applied to the bearing from the variable preload mechanism 9A via the outer ring 7 is set to a small initial value. When the vehicle shifts to turning, the rotary member 11 of the preload variable mechanism 9A is rotationally driven, whereby the preload variable mechanism 9A as a whole extends in the axial direction, and the amount of preload applied to the bearing increases.

FIG. 7 shows still another reference proposal example of the present invention. The wheel bearing device with a preload variable mechanism of this reference proposal example is obtained by integrating the fixing member 10 of the preload variable mechanism 9A with the outer ring 8 in the reference proposal example of FIG. That is, the fixing member 10 which is an independent part is omitted, and the cam surface 10a facing the cam surface 11a of the rotating member 11 is formed on the end surface of the outer ring 8 facing the rotating member 11 of the preload variable mechanism 9A in the axial direction. It is. Also in this case, the cam surface 10a is the same as the cam surface 10a of the fixing member 10 in the first embodiment.

Thus, by integrating the fixing member 10 of the preload variable mechanism 9A with the outer ring 8, the influence of the rotation play between the outer ring 8 and the fixing member 10 can be eliminated, and the variable control of the preload amount is reliably performed. It can be performed. Other configurations and effects are the same as those of the reference proposal example of FIG.

It is explanatory drawing which combined sectional drawing of the wheel bearing apparatus with a preload variable mechanism concerning 1st Embodiment of this invention, and the block diagram of the control system. It is sectional drawing of the preload variable mechanism in the same bearing apparatus. It is a front view of the fixing member of the preload variable mechanism in the same bearing device, and a rotation member. It is sectional drawing of the wheel bearing apparatus with a preload variable mechanism concerning other embodiment of this invention. It is sectional drawing of the wheel bearing apparatus with a preload variable mechanism concerning further another embodiment of this invention. It is sectional drawing of the wheel bearing apparatus with a preload variable mechanism concerning the example of a reference proposal of this invention. It is sectional drawing of the wheel bearing apparatus with a preload variable mechanism concerning the further another reference proposal example of this invention. It is explanatory drawing of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Outer member 1a ... Car body mounting flange 2 ... Inner member 3 ... Rolling elements 4, 5 ... Track surface 7 ... Outer ring member 7a ... Step surface 7b ... Outer ring fitting surface 8 ... Outer ring 9, 9A ... Preload variable mechanism DESCRIPTION OF SYMBOLS 10 ... Fixed member 11 ... Rotating member 10a, 11a ... Cam surface 12 ... Ball 19 ... Running condition detection means 20 ... Preload change control means

Claims (4)

An outer member having a double-row raceway surface on the inner periphery, an inner member having a raceway surface facing these raceway surfaces, and a double-row rolling element interposed between the opposing raceway surfaces, In the wheel bearing that supports the wheel rotatably,
A preload adjustment mechanism for changeably impart a preload to the bearing, e Bei detecting means for detecting a running condition of the vehicle, and means for causing a preload changing operation to the preload variable mechanism by an output of the detection means,
The outer member is composed of an outer ring member and an outer ring, and the outer ring member has a body mounting flange integrally on the outer periphery, and a raceway surface of the outboard side row is formed on the inner periphery. A cylindrical surface extending in the axial direction from the side raceway surface through a step surface, and having an outer ring fitting surface larger in diameter than the raceway surface, and the outer ring is formed with a raceway surface in an inboard side row to form the outer ring Fitting to the outer ring fitting surface of the member,
The preload variable mechanism is interposed between the step surface of the outer ring member and the end surface of the outer ring, and the preload variable mechanism is axially driven by relative rotation of a pair of cam surfaces facing in the axial direction via balls. The cam mechanism is operated by rotating the outer ring with respect to the outer ring member, and the preload can be changed.
The outer ring has a rotationally transmitted portion that protrudes toward the inboard side of the outer ring member, and through this rotationally transmitted portion, a driving force for rotating the outer ring for causing the preload variable mechanism to change the preload. Wheel bearing device with variable preload mechanism to receive . Oite to claim 1, means for detecting a traveling state of the vehicle are those that can distinguish between the turning and straight running of the vehicle, means for causing a preload changing operation to the preload variable mechanism, preload A wheel bearing device with a variable preload mechanism that performs a preload changing operation so that the amount is small during straight traveling and large during turning. In the first or second aspect , the means for causing the preload variable mechanism to perform the preload changing operation sets the initial preload amount to be small, and sets the initial preload amount during straight traveling according to the traveling state of the vehicle. A wheel bearing device with a variable preload mechanism that keeps the amount of preload increased during turning. In any one of claims 1 to 3, wherein the means for causing a preload changing operation to the preload variable mechanism, the bearing clearance at the time of straight running by the vehicle running state in -10～0Myuemu, bearing clearance during cornering A wheel bearing device with a preload variable mechanism, in which the preload is variably set so that becomes -50 to -10 m.

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