Patent Description:
Generally, hub unit bearings are used in a state in which a pre-load is applied. When a pre-load does not fall within an appropriate range, problems occur in that a sufficient strength or service life is not secured, a low torque cannot be sufficiently achieved, or the like. These problems may affect steering stability or ride comfort of the automobile. Therefore, a pre-load needs to be within an appropriate range in hub unit bearings.

On the other hand, <CIT> (Patent Document <NUM>) describes a hub unit bearing to which a pre-load according to the amount of caulking of an axial end portion of a hub wheel is applied. In the hub unit bearing, a hub rotating together with a wheel includes the hub wheel and an inner wheel externally fitted to the hub wheel and fixed to the hub wheel by caulking the axial end portion of the hub wheel. Also, Patent Document <NUM> describes a method of determining a pre-load after completing an operation of forming a caulking part in order to perform pre-load management for such a hub unit bearing.

Further, conventionally, as a method of caulking an axial end portion of a hub wheel, rotary caulking in which a caulking die that performs rotary rotation is pressed against the axial end portion of the hub wheel is widely known. <CIT> (Patent Document <NUM>), <CIT> (Patent Document <NUM>), and <CIT> (Patent Document <NUM>) describe methods and devices for caulking an axial end portion of a hub wheel so that an unbalanced load is not applied.

Patent document <CIT> (Patent Document <NUM>), on which the preamble of independent claims <NUM> and <NUM> is based, relates to a pre-load applying device of a bearing when caulking work is started by gradually lowering a caulking die of a swinging type caulking device, a pre-load is applied to a combinational bearing from a certain time <NUM>, and rotational torque T changes. When its change width reaches a preset prescribed width Δ, it is judged that the pre-load reaches a prescribed value, and caulking work is finished. Therefore, a pre-load can be adjusted at caulking work time of the combinational bearing.

In the method described in Patent Document <NUM> (<CIT>), since a pre-load is determined after an operation of forming a caulking part is competed, basically, there is a problem in that adjustment of the pre-load cannot be performed thereafter, even when it is found that the pre-load does not fall within an appropriate range as a result of the determination.

An objective of the present invention is to provide a specific means capable of causing a pre-load to fall within an appropriate range.

The presently claimed invention relates to a method according to claim <NUM> and a manufacturing device of a hub unit bearing according to claim <NUM>.

A hub unit bearing to be manufactured according to the present invention may include an outer wheel having a plurality of rows of outer wheel trajectories on an inner circumferential surface thereof, a hub having a plurality of rows of inner wheel trajectories on an outer circumferential surface thereof, and a plurality of rolling elements disposed between the plurality of rows of the inner wheel trajectories and the plurality of rows of the outer wheel trajectories. The hub includes a hub wheel and an inner wheel externally fitted to the hub wheel and fixed to the hub wheel by caulking an axial end portion of the hub wheel. A pre-load according to an amount of caulking of the axial end portion of the hub wheel is applied.

The method of manufacturing a hub unit bearing according to the present invention includes a caulking step and a pre-load determination step. In the caulking process, caulking processing of the axial end portion of the hub wheel (or hub main body) is performed while rotationally driving the outer wheel with respect to the hub (or hub main body) in a manufacturing device. In the pre-load determination step, a change in rotation speed of the outer wheel is measured while the outer wheel is rotated only by inertia with respect to the hub and whether or not the pre-load of the hub unit bearing falls within an appropriate range is determined on the basis of the measured change in the rotation speed in the manufacturing device after the caulking step has ended.

The following configuration can be employed in the method of manufacturing a hub unit bearing according to the present invention. That is, in the pre-load determination step, a difference between the measured change in the rotation speed and the change in the rotation speed of the outer wheel rotated only by inertia when an optimum pre-load is applied to the hub unit bearing that has been investigated in advance is obtained, and the pre-load of the hub unit bearing is determined to fall within the appropriate range only when the difference is equal to or less than a preset threshold value.

The following configuration can be employed in the method of manufacturing a hub unit bearing according to the present invention. That is, in the caulking step, the caulking processing is performed under a processing condition in which the pre-load of the hub unit bearing is smaller than the optimum pre-load at the end of the caulking processing.

A method of manufacturing a vehicle according to the present invention is directed to a vehicle including a hub unit bearing, and the hub unit bearing is manufactured by the method of manufacturing a hub unit bearing according to the present invention.

An exemplary manufacturing device of a hub unit bearing includes an outer wheel driver, a caulking tool, a rotation speed sensor, and a pre-load determinator. The outer wheel driver can selectively switch between a state of rotationally driving the outer wheel with respect to the hub and a state of allowing the outer wheel to rotate only by inertia without rotational drive. The caulking tool can selectively switch between states of performing and not performing caulking processing of the axial end portion of the hub wheel. The rotation speed sensor can measure a change in rotation speed of the outer wheel rotated only by inertia. The pre-load determination unit determines whether or not a pre-load of the hub unit bearing falls within an appropriate range on the basis of the change in the rotation speed of the outer wheel rotated only by inertia measured by the rotation speed sensor.

The following configuration can be employed in the manufacturing device of a hub unit bearing according to the present invention. That is, the pre-load determinator has functions of obtaining a difference between the change in the rotation speed of the outer wheel rotated only by inertia measured by the rotation speed sensor and the change in the rotation speed of the outer wheel rotated only by inertia when an optimum pre-load is applied to the hub unit bearing that has been stored in advance, and determining the pre-load of the hub unit bearing to be within the appropriate range only when the difference is equal to or less than a preset threshold value.

According to the present invention, it is possible to cause the pre-load of the hub unit bearing to fall within an appropriate range.

A first example of an embodiment of the present invention will be described with reference to <FIG>.

<FIG> is a partial schematic view of a vehicle <NUM> including a hub unit bearing (bearing unit) <NUM>. The present invention can be applied to any of a hub unit bearing for driving wheels and a hub unit bearing for driven wheels. In <FIG>, the hub unit bearing <NUM> is for drive wheels and includes an outer wheel 2A, a hub 3A, and a plurality of rolling elements 4A. The outer wheel 2A is fixed to a knuckle <NUM> of a suspension system using bolts or the like. A wheel (and a rotating body for braking) <NUM> is fixed to a flange (rotating flange) 9A provided on the hub 3A using bolts or the like. Also, the vehicle <NUM> can have the same support structure as described above for the hub unit bearing <NUM> for driven wheels.

<FIG> shows the hub unit bearing (bearing unit) <NUM> for driven wheels. In the example of <FIG>, the hub unit bearing <NUM> includes an outer wheel <NUM>, a hub <NUM>, and a plurality of rolling elements <NUM>.

Also, regarding the hub unit bearing <NUM>, an axially outer side is the left side in <FIG> which is an outer side in a width direction of a vehicle in a state in which it is assembled to the vehicle. An axially inner side is the right side in <FIG> which is on a center side in the width direction of the vehicle in a state in which the hub unit bearing <NUM> is assembled to the vehicle.

The outer wheel <NUM> includes a plurality of rows of outer wheel trajectories <NUM> on an inner circumferential surface and includes a stationary flange <NUM> protruding outward in a radial direction at an intermediate portion in the axial direction. The stationary flange <NUM> includes support holes <NUM> at a plurality of positions in a circumferential direction. The outer wheel <NUM> is coupled and fixed to a knuckle of a suspension system using knuckle bolts inserted or screwed into the support holes <NUM>.

The hub <NUM> is disposed coaxially with the outer wheel <NUM> on an inner diameter side of the outer wheel <NUM> and includes a plurality of rows of inner wheel trajectories <NUM> on an outer circumferential surface. Further, the hub <NUM> includes a rotating flange <NUM> protruding outward in the radial direction at an axially outer side portion which protrudes outward in the axial direction with respect to the outer wheel <NUM>. The rotating flange <NUM> includes attachment holes <NUM> at a plurality of positions in the circumferential direction. The wheel and the rotating body for braking are supported by and fixed to the rotating flange <NUM> using hub bolts press-fitted or screwed into the attachment holes <NUM>.

The plurality of rolling elements <NUM> are disposed to be rollable in each of the rows between the plurality of rows of the outer wheel trajectories <NUM> and the plurality of rows of the inner wheel trajectories <NUM>. Further, in the shown example, tapered rollers are used as the rolling elements <NUM>. In another example, balls can be used as the rolling elements <NUM>.

Also, the hub <NUM> includes a hub wheel (hub main body, unit main body) <NUM> and a pair of inner wheels 12a and 12b. The plurality of rows of the inner wheel trajectories <NUM> are provided on an outer circumferential surface of each of the pair of inner wheels 12a and 12b. The rotating flange <NUM> is provided on the axially outer portion of the hub wheel <NUM>. Also, the hub wheel <NUM> includes a cylindrical fitting surface part <NUM> on an outer circumferential surface of an intermediate portion and an inner end portion in the axial direction. Further, the hub wheel <NUM> includes a stepped surface <NUM> facing the inner side in the axial direction on an outer end portion in the axial direction of the fitting surface part <NUM>. The pair of inner wheels 12a and 12b are externally fitted to the fitting surface part <NUM> of the hub wheel <NUM> by press-fitting (interference fitting). In this state, a caulking part <NUM> is formed by caulking a cylindrical part (axial end) <NUM> provided at an inner end portion in the axial direction of the hub wheel <NUM> (by plastic deformation outward in the radial direction). An axially inner end surface of the inner wheel 12a on the axially inner side is pressed down by the caulking part <NUM>. That is, by interposing the pair of inner wheels 12a and 12b between the stepped surface <NUM> of the hub wheel <NUM> and the caulking part <NUM>, separation between the pair of inner wheels 12a and 12b and the hub wheel <NUM> can be prevented. Also, in this state, a pre-load in an appropriate range is applied to the hub unit bearing <NUM>.

In the present example, in a state in which the hub unit bearing <NUM> is assembled before the caulking part <NUM> is formed (first assembly state), shapes and dimensions of respective members constituting the hub unit bearing <NUM> are restricted so that a pre-load smaller than a pre-load after the caulking part <NUM> is formed is applied. In the first assembly state, a plurality of rolling elements <NUM> are disposed to be rollable in each of the rows between the plurality of rows of the outer wheel trajectories <NUM> and the plurality of rows of the inner wheel trajectories <NUM>, and the pair of inner wheels 12a and 12b are externally fitted on the fitting surface part <NUM> of the hub wheel <NUM> before the caulking part <NUM> is formed by press-fitting. Also, in the first assembly state, an axially outer end surface of the inner wheel 12b on the axially outer side is in contact with the stepped surface <NUM>, and an axially outer end surface of the inner wheel 12a on the axially inner side is in contact with an axially inner end surface of the inner wheel 12b on the axially outer side. Thereafter, when the caulking part <NUM> is formed, an axial force from the caulking part <NUM> is applied to the inner wheel 12a on the axially inner side, thereby increasing the pre-load. The pre-load in a second assembly state in which the caulking part <NUM> is formed has a greater value compared to the pre-load in the first assembly state. An increment in the pre-load at this time is an amount according to a degree of processing of the caulking part <NUM>, that is, an amount of caulking of the axially inner end portion of the hub wheel <NUM>. The hub unit bearing <NUM> is manufactured such that the pre-load in a state in which such a caulking part <NUM> is formed (second assembly state) falls within an appropriate range (predetermined range).

Next, a manufacturing device (a caulking device, a rotary caulking device) <NUM> of the hub unit bearing of the present example will be described. The manufacturing device <NUM> of the present example is for forming the caulking part <NUM> by caulking the cylindrical part <NUM> (<FIG>) of the hub wheel <NUM>. As shown in <FIG>, such a manufacturing device <NUM> of the present example includes a support body (base) <NUM>, a caulking die <NUM> serving as a caulking tool, a rotating body (rotating adapter, adapter) <NUM>, an outer wheel driver (drive unit) <NUM>, a rotation speed sensor (sensor) <NUM>, and a control device <NUM>.

The support body (base) <NUM> is for supporting the hub wheel <NUM> of the hub unit bearing <NUM> and has a reference axis C in a vertical direction. Also, the support body <NUM> has a shape on which the hub wheel <NUM> can be coaxially placed with the axially outer end portion of the hub wheel <NUM> directed downward.

The caulking die <NUM> is disposed above the support body <NUM>. The caulking die <NUM> has a main axis α provided coaxially with the reference axis C of the support body <NUM> and a rotation axis β inclined at a predetermined angle θ with respect to the main axis α. Also, the caulking die <NUM> includes a processing surface part <NUM> having an annular shape centered on the rotation axis β at a distal end (lower end) thereof. The caulking die <NUM> as described above is provided to be vertically movable with respect to the support body <NUM>. Further, the caulking die <NUM> can revolve (rotary rotation) around the main axis α and is rotatable around the rotation axis β with an electric motor (not shown) for the caulking die as a drive source.

The rotating body (adapter) <NUM> is fixed to the outer wheel <NUM> of the hub unit bearing <NUM> when the caulking part <NUM> is formed and rotates together with the outer wheel <NUM>. The rotating body <NUM> is formed in an annular shape and is disposed coaxially with the outer wheel <NUM> around the axially inner portion of the outer wheel <NUM>. Also, in a state in which the rotating body <NUM> is in contact with an axially inner surface of the stationary flange <NUM> constituting the outer wheel <NUM>, the rotating body <NUM> is fixed to the outer wheel <NUM> by inserting or screwing coupling members such as bolts (not shown) into the support holes <NUM>. Also, the rotating body <NUM> includes an outer circumferential portion on which a driven gear part <NUM> having a projected or indented shape along the circumferential direction is formed. Also, the rotating body <NUM> is made of a magnetic metal and is configured such that the driven gear part <NUM> can function as a part to be detected for detecting a rotation speed. In another example, the rotating body <NUM> is configured to rotate together with the outer wheel <NUM> in a state in which it is not substantially fixed to the outer wheel <NUM>, for example, in a state in which a portion of the rotating body <NUM> is in contact with the outer wheel <NUM>.

The outer wheel driver <NUM> is for rotationally driving the outer wheel <NUM> and includes a gear <NUM> and an outer wheel electric motor (drive motor, drive source) <NUM> (<FIG>). The gear <NUM> is formed in a disc shape. Also, the gear <NUM> includes an outer circumferential portion on which a drive gear part <NUM> having a projected or indented shape along the circumferential direction is formed. The gear <NUM> as described above is disposed at a position facing the rotating body <NUM> fixed to the outer wheel <NUM> in the radial direction in a state in which a central axis G of the gear <NUM> is caused to coincide with the vertical direction. Also, the gear <NUM> is rotatable around its own central axis G with the outer wheel electric motor <NUM> as the drive source and is movable toward and away from the rotating body <NUM> in the radial direction. On the basis of the fact that the gear <NUM> is movable toward and away from the rotating body <NUM> in the radial direction, it is possible to switch between a state in which the drive gear part <NUM> is engaged with the driven gear part <NUM> to transmit a torque (<FIG>) and a state in which the drive gear part <NUM> is separated from the driven gear part <NUM> (<FIG> and <FIG>).

The rotation speed sensor <NUM> is for measuring a rotation speed of the outer wheel <NUM>. In one example, when measuring at least the rotation speed of the outer wheel <NUM>, the rotation speed sensor <NUM> is disposed at a position at which it closely faces the driven gear part <NUM> of the rotating body <NUM> fixed to the outer wheel <NUM> in the radial direction. For example, the rotation speed sensor <NUM> is a magnetic-type sensor, and a magnetic detection element such as a Hall IC or the like and a permanent magnet are incorporated in a detection part facing the driven gear part <NUM>. When measuring the rotation speed of the outer wheel <NUM>, when the rotating body <NUM> rotates together with the outer wheel <NUM>, a convex part (tooth part) and a concave part (groove part) constituting the driven gear part <NUM> alternately pass in the vicinity of the detection part. As a result, due to the density of magnetic flux passing through the magnetic detection element changing periodically, an output signal of the rotation speed sensor <NUM> changes periodically. Since the frequency of the output signal at this time is proportional to the rotation speed of the outer wheel <NUM>, the rotation speed of the outer wheel <NUM> can be obtained on the basis of the frequency of the output signal.

The control device <NUM> is for controlling an operation of the manufacturing device <NUM> and has a function of controlling movement of the caulking die <NUM> and the outer wheel driver <NUM>, and a function of performing determination of a pre-load and setting of processing conditions to be described below. In the present example, the control device <NUM> functions as a pre-load determinator. The control device <NUM> can include, for example, a controller having a memory <NUM>, a computer (a central processing unit (CPU), a processor, or a circuit) <NUM>, and the like.

Next, a method of forming the caulking part <NUM> by subjecting the cylindrical part <NUM> (<FIG>) of the hub wheel <NUM> to caulking processing in order to manufacture the hub unit bearing <NUM> of the present example will be described.

Further, an operation of forming the caulking part <NUM> is performed in a state in which the hub unit bearing <NUM> is assembled before the caulking part <NUM> is formed (first assembly state). Therefore, the hub unit bearing <NUM> is assembled in advance before the caulking part <NUM> is formed.

When forming the caulking part <NUM> using the manufacturing device <NUM> of the present example, first, as shown in <FIG>, the hub wheel <NUM> is coaxially placed on the support body <NUM> with the axially outer end portion directed downward in a state in which the caulking die <NUM> is raised and the gear <NUM> is retreated radially outward. At the same time, the rotating body <NUM> is coaxially fixed to the outer wheel <NUM>. In this state, the detection part of the rotation speed sensor <NUM> closely faces the driven gear part <NUM> of the rotating body <NUM> in the radial direction.

Next, the drive gear part <NUM> of the gear <NUM> is engaged with the driven gear part <NUM> of the rotating body <NUM> by bringing the gear <NUM> close to the rotating body <NUM>. By rotationally driving the gear <NUM>, the rotating body <NUM> and the outer wheel <NUM> are rotated with respect to the hub <NUM>. At the same time, the caulking die <NUM> is rotated (rotary rotation) around the main axis α.

In this state, the cylindrical part <NUM> is subjected to the caulking processing by lowering the caulking die <NUM> and pressing the processing surface part <NUM> of the caulking die <NUM> against the cylindrical part <NUM> of the hub wheel <NUM>, and thereby the caulking part <NUM> is formed (see <FIG>). That is, a load is applied downward in the vertical direction and outward in the radial direction from the caulking die <NUM> to a portion in the circumferential direction of the cylindrical part <NUM>. Also, the position to which the load is applied is continuously changed in the circumferential direction of the cylindrical part <NUM> as the caulking die <NUM> rotates around the main axis α. Thus, the caulking part <NUM> is formed by caulking the cylindrical part <NUM>.

Particularly, in the present example, the above-described caulking processing is performed while determining the pre-load of the hub unit bearing in the middle thereof.

That is, in the present example, in order to determine the pre-load in the middle of the caulking processing shown in <FIG>, the caulking die <NUM> is raised to eliminate a load applied from the caulking die <NUM> to the hub unit bearing <NUM> as shown in <FIG>, and simultaneously with or after this, the gear <NUM> is retreated from the rotating body <NUM> to release the driving force applied from the gear <NUM> to the rotating body <NUM>. Thereby, the outer wheel <NUM> (together with the rotating body <NUM> and the coupling member) is rotated only by inertia (inertial rotation). A change in the rotation speed (differential coefficient), which is a temporal change of the rotation speed of the outer wheel <NUM> at this time, is measured by the rotation speed sensor <NUM>.

Here, a relationship between time and a rotation speed of the outer wheel <NUM> that rotates only by inertia differs for each pre-load of the hub unit bearing <NUM>. <FIG> shows a conceptual diagram of the relationship. As shown in <FIG>, the rotation speed of the outer wheel <NUM> rotated only by inertia changes (decreases) with the elapse of time, and the rate of change becomes greater as the pre-load of the hub unit bearing <NUM> (rolling resistance of the rolling elements <NUM>) becomes greater. In other words, the change in the rotation speed of the outer wheel <NUM> rotated only by inertia corresponds to the pre-load. Therefore, in the present example, the pre-load of the hub unit bearing <NUM> is determined, that is, ascertained from the change in the rotation speed of the outer wheel <NUM> that rotates only by inertia.

Further, V<NUM> in <FIG> and <FIG> to be described below is the rotation speed of the outer wheel <NUM> at the time of performing the caulking processing (<FIG>), and is the rotation speed (initial rotation speed) of the outer wheel <NUM> at the moment when the outer wheel <NUM> starts rotating only by inertia, that is, at the moment when the driving force applied to the rotating body <NUM> from the gear <NUM> is released. In the present example, V<NUM> is always the same magnitude.

In <FIG>, the change in the rotation speed of the outer wheel <NUM> rotated only by inertia at the initial stage (immediately after the rotation is started only by inertia, that is, in the region X surrounded by the chain line in <FIG>) (hereinafter, this may be simply referred to as an initial change in the rotation speed) is shown as an inclination of a straight line in coordinates representing a relationship between time and a rotation speed. Such an initial change in the rotation speed also differs for each pre-load as a matter of course. In order to complete the operation of forming the caulking part <NUM> at an early stage, it is desirable to finish the operation of pre-load determination in a short time. Therefore, in the present example, the pre-load is determined from the initial change in the rotation speed measured by the rotation speed sensor <NUM>. Further, a length of the initial time can be arbitrarily set but is preferably set as small as possible within a range in which the change in the rotation speed can be measured with high accuracy.

In any case, in the present example, next, it is determined whether the pre-load ascertained from the initial change in the rotation speed measured by the rotation speed sensor <NUM> falls within an appropriate range. As a result, when it is found that the pre-load does not fall within the appropriate range, the caulking processing (<FIG>) is resumed to further increase the degree of processing of the caulking part <NUM> (increment of the pre-load by the caulking part <NUM>). Further, a rotation speed of the outer wheel <NUM> during the caulking processing at this time is also set to V<NUM>. Thereafter, an initial change in the rotation speed of the outer wheel <NUM> rotated only by inertia is measured again (<FIG>), and it is determined whether a pre-load ascertained from the measured change in the rotation speed falls within the appropriate range. In the present example, the caulking processing (<FIG>) and the determination as described above are repeated until it is determined that the pre-load falls within the appropriate range. Then, when the pre-load falls within the appropriate range, the operation of forming the caulking part <NUM> is completed.

As described above, in the one example, a method of manufacturing the hub unit bearing <NUM> includes a step of supporting the hub wheel (hub main body) <NUM>, a step of caulking the hub wheel <NUM> to which the inner wheels 12a and 12b and the outer wheel <NUM> are attached, a step of detecting a speed of inertial rotation of the outer wheel <NUM> by the sensor <NUM>, and a step of comparing reference information on a change of the speed in the inertial rotation of the outer wheel <NUM> to measurement information on a change of the speed in the inertial rotation of the outer wheel <NUM> according to a detection result of the sensor <NUM>. The control device <NUM> includes the memory <NUM> and the circuit <NUM> communicating with the sensor <NUM> and the memory <NUM>. The control device <NUM> outputs the reference information on the change of the speed in the inertial rotation of the outer wheel <NUM> stored in the memory <NUM> and the measurement information on the change of the speed in the inertial rotation of the outer wheel <NUM> according to the detection result of the sensor <NUM>. The output information can be displayed, for example, on a display (not shown). With regard to the change of the speed in the inertial rotation of the outer wheel <NUM>, the reference information can include a lower limit value and an upper limit value according to an appropriate range of the pre-load in the hub unit bearing <NUM>. The control device <NUM> can be configured to determine the appropriateness of the pre-load in the hub unit bearing <NUM> according to the reference information and the measurement information.

Next, the operation forming the caulking part <NUM> for causing the pre-load to fall within the appropriate range as described above will be described by taking a more specific example.

Further, in the present example, as a preparation for performing the operation of forming the caulking part <NUM> as described above, curves of changes in the rotation speed of the outer wheel <NUM> rotated only by inertia which are different for each pre-load as shown in <FIG> are obtained beforehand using a hub unit bearing <NUM> (master) whose pre-load is known. Further, initial changes in the rotation speed of these obtained curves are stored in a database as inclinations of straight lines as shown in <FIG>. Then, this database is stored in the control device <NUM>. This database is used to obtain conditions (processing load, processing time, rotary rotation speed, or the like) for a second and subsequent caulking processes to be described below.

First, a first caulking step, that is, the caulking processing (<FIG>) is performed. Conditions of the caulking processing at this time are adjusted so that the pre-load is not greater than an optimum pre-load. Further, a rotation speed of the outer wheel <NUM> during the caulking processing at this time is set to V0. Thereafter, a first pre-load determination step is performed. For this, first, an initial rotation speed change A1 of the first time is measured (<FIG> and <FIG>). Next, a difference (A1-A) between the measured rotation speed change A1 and an initial rotation speed change A when the optimum pre-load is applied is obtained. Further, the difference (A1-A) is a difference in inclinations between the two straight lines A1 and A in <FIG>. Next, whether the obtained difference (A1-A) is equal to or less than a threshold value ΔA {(A1-A) ≤ ΔA}, that is, whether or not the pre-load falls within the appropriate range is determined. When the pre-load falls within the appropriate range (when it is determined to be within), the operation of forming the caulking part <NUM> ends, and when the pre-load does not fall within the appropriate range (when it is not determined to be within), the operation of forming the caulking part <NUM> is continued. Here, it is assumed that the pre-load does not fall within the appropriate range.

Therefore, in order to continue the operation of forming the caulking part <NUM>, conditions of the caulking processing (<FIG>) for a second caulking step are obtained. Specifically, the conditions of the caulking processing are obtained such that the initial change in the rotation speed corresponding to the pre-load is slightly lower than or the same as the initial change in the rotation speed when the optimum pre-load is applied. When the conditions are obtained, the above-described database is utilized. For this, a relationship between the difference (A1-A) and conditions of the caulking processing for eliminating the difference (A1-A) obtained by conducting an experiment in advance or information for obtaining the conditions of the caulking processing to eliminate the difference (A1-A) by calculation is included in the above-described database.

Next, the second caulking step, that is, the caulking processing (<FIG>) is performed under the conditions of the caulking processing obtained as described above. A rotation speed of the outer wheel <NUM> during the caulking processing at this time is also set to V<NUM>. Thereafter, a second pre-load determination step is performed. For this, first, an initial rotation speed change A2 of the second time is measured (<FIG> and <FIG>). Next, similarly to the first time, a difference (A2-A) between the measured rotation speed change A2 and the initial rotation speed change A when the optimum pre-load is applied is obtained. Next, whether the obtained difference (A2-A) is equal to or less than the threshold value ΔA {(A2-A) ≤ ΔA}, that is, whether or not the pre-load falls within the appropriate range is determined. When the pre-load falls within the appropriate range, the operation of forming the caulking part <NUM> ends, and when the pre-load does not fall within the appropriate range, the operation of forming the caulking part <NUM> is continued. Here, it is assumed that the pre-load does not fall within the appropriate range.

Therefore, in order to continue the operation of forming the caulking part <NUM>, conditions of the caulking processing (<FIG>) for a third caulking step are obtained. Specifically, the conditions of the caulking processing are obtained such that the initial change in the rotation speed corresponding to the pre-load is slightly lower than or the same as the initial change in the rotation speed when the optimum pre-load is applied. When the conditions are obtained, the above-described database is utilized.

Next, the third caulking step, that is, the caulking processing (<FIG>) is performed under the conditions of the caulking processing obtained as described above. A rotation speed of the outer wheel <NUM> during the caulking processing at this time is also set to V<NUM>. Thereafter, a third pre-load determination step is performed. For this, first, an initial rotation speed change A3 of the third time is measured (<FIG> and <FIG>). Similarly to the first time, a difference (A3-A) between the measured rotation speed change A3 and the initial rotation speed change A when the optimum pre-load is applied is obtained. Next, whether the obtained difference (A3-A) is equal to or less than the threshold value ΔA {(A3-A) ≤ ΔA}, that is, whether or not the pre-load falls within the appropriate range is determined. When the pre-load falls within the appropriate range, the operation of forming the caulking part <NUM> ends, and when the pre-load does not fall within the appropriate range, the operation of forming the caulking part <NUM> is continued (hereafter also, the caulking step and pre-load determination step are repeated until the pre-load falls within the proper range). Here, it is assumed that the pre-load falls within the appropriate range.

Therefore, the operation of forming the caulking part <NUM> ends, and the hub unit bearing <NUM> is taken out from the manufacturing device <NUM>. Further, <FIG> shows changes in the rotation speed of the outer wheel <NUM> from the start to the end of the operation of forming the caulking part <NUM> described above.

As described above, in the present example, since the caulking processing for forming the caulking part <NUM> is performed while determining the pre-load of the hub unit bearing <NUM> in the middle thereof, it is possible to cause the pre-load to fall within the appropriate range.

Also, in the present example, since a method of gradually bringing the pre-load of the hub unit bearing <NUM> closer to an optimum pre-load while repeating the caulking step and the pre-load determination step is employed, for example, variations in pre-load of the hub unit bearing <NUM> after completion can be sufficiently reduced compared to a method of completing the operation of forming the caulking part <NUM> with performing the caulking processing only once for all the hub unit bearings <NUM> to be manufactured. Accordingly, even when manufacturing a hub unit bearing <NUM> in which the appropriate range of the pre-load is narrow, an applied pre-load can easily be within the appropriate range.

Also, in the present example, since the caulking step and the pre-load determination step from the first time to the third time (final time) can be performed without taking out the hub unit bearing <NUM> from the manufacturing device <NUM> in the middle or stopping rotation of the outer wheel <NUM> in the middle (see <FIG>), the operation of forming the caulking part <NUM> can be efficiently performed.

The present invention is also applicable to a hub unit bearing having a structure in which a hub wheel and an inner wheel on an axially outer side are integrated, that is, a structure in which inner wheel trajectories on the axially outer side are formed directly on an outer circumferential surface of the hub wheel.

In the manufacturing device of the hub unit bearing of the present invention, as for the structure of the first example of the embodiment, a configuration in which the support body <NUM> moves in the vertical direction instead of the caulking die <NUM> moving in the vertical direction can also be employed.

Claim 1:
A method of manufacturing a hub unit bearing (<NUM>) including:
supporting a hub main body (<NUM>);
caulking the hub main body (<NUM>), to which an inner wheel (12a, 12b) and an outer wheel (<NUM>) are attached, in a caulking step in which caulking processing of an axial end portion (<NUM>) of the hub main body (<NUM>) is performed while rotationally driving the outer wheel (<NUM>) with respect to the hub main body (<NUM>) in a manufacturing device,
wherein the method is characterized in that:
in the manufacturing device, after the caulking step has ended, a pre-load determination step is performed, in which a change in rotation speed of the outer wheel (<NUM>) is measured while the outer wheel (<NUM>) is rotated only by inertia with respect to the hub main body (<NUM>) and whether or not the pre-load of the hub unit bearing (<NUM>) falls within an appropriate range is determined on the basis of the measured change in the rotation speed.