JP2005091073A - Rotation speed detector and load measuring instrument for roller bearing unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect a revolution speed of a rotary member with a fixed encoder, even when an output signal of a rotation detecting sensor is varied by fluctuation in distances between a detected face of the encoder and a detecting part of the rotation detecting sensor. <P>SOLUTION: A sensor capable of transmitting an analog signal varied as shown by a full line c in (A) is used as the rotation detecting sensor. The analog signal is compared with threshold values shown by broken lines a, b in the (A), by a comparator, to obtain a digital data shown in (B). The threshold values are changed in response to a peak value just before the analog signal. By this constitution, a pitch of the digital signal is prevented from being shifted with respect to a pitch of the analog signal, irrespective of fluctuation of the analog signal based on the fluctuation in distances, so as to solve the problem hereinbefore. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  A rotational speed detection device and a load measuring device for a rolling bearing unit according to the present invention relate to an improvement of a rolling bearing unit for supporting wheels of a moving body such as an automobile, a railway vehicle, and various transport vehicles. Measures the rotational speed of the rotating member, and also the load (one or both of radial load and axial load) applied to this rolling bearing unit, and uses it to ensure the stability of the operation of the moving body. .

  For example, an automobile wheel is rotatably supported by a double row angular rolling bearing unit with respect to a suspension device. In order to ensure the running stability of automobiles, vehicle running stabilizers such as an antilock brake system (ABS), a traction control system (TCS), and a vehicle stability control system (VSC) are used. . In order to control such various vehicle running stabilizers, signals such as the rotational speed of the wheels and the acceleration in each direction applied to the vehicle body are required. In order to perform higher-level control, it may be preferable to know the magnitude of a load (one or both of a radial load and an axial load) applied to the rolling bearing unit via the wheel.

  In view of such circumstances, Patent Document 1 describes a rolling bearing unit with a load measuring device capable of measuring a radial load. This conventional rolling bearing unit with a load measuring device of the first example measures a radial load and is configured as shown in FIG. A hub 2, which is a rotating wheel, is connected to the inner diameter side of the outer ring 1, which is a stationary wheel, and is supported by the suspension device. The hub 2 includes a hub body 4 having a rotation-side flange 3 for fixing a wheel at an outer end thereof (an end on the outer side in the width direction when assembled to a vehicle), and an inner end of the hub body 4. And an inner ring 6 that is externally fitted to the end (on the widthwise center side in the assembled state in the vehicle) and held down by a nut 5. And the double row outer ring raceways 7 and 7 each formed on the inner peripheral surface of the outer ring 1 and each of which is a stationary side track, and the double row each formed on the outer peripheral surface of the hub 2 and each of which is a rotation side track. A plurality of rolling elements 9 a and 9 b are arranged between the inner ring raceways 8 and 8, respectively, so that the hub 2 can freely rotate on the inner diameter side of the outer ring 1.

  A mounting hole 10 that diametrically penetrates the outer ring 1 is formed in a substantially vertical direction at an upper end portion of the outer ring 1 in a portion between the double row outer ring raceways 7 and 7 at an intermediate portion in the axial direction of the outer ring 1. Yes. In the mounting hole 10, a circular (rod-shaped) displacement sensor 11, which is a load measuring sensor, is mounted. This displacement sensor 11 is a non-contact type, and the detection surface provided on the front end surface (lower end surface) is closely opposed to the outer peripheral surface of the sensor ring 12 fitted and fixed to the intermediate portion in the axial direction of the hub 2. When the distance between the detection surface and the outer peripheral surface of the sensor ring 12 changes, the displacement sensor 11 outputs a signal corresponding to the amount of change.

  In the case of the conventional rolling bearing unit with a load measuring device configured as described above, the load applied to the rolling bearing unit can be obtained based on the detection signal of the displacement sensor 11. That is, the outer ring 1 supported by the vehicle suspension device is pushed downward by the weight of the vehicle, whereas the hub 2 supporting and fixing the wheel tends to stop at the same position. For this reason, the greater the weight, the greater the deviation between the center of the outer ring 1 and the center of the hub 2 based on the elastic deformation of the outer ring 1, the hub 2, and the rolling elements 9a, 9b. The distance between the detection surface of the displacement sensor 11 and the outer peripheral surface of the sensor ring 12 provided at the upper end of the outer ring 1 becomes shorter as the weight increases. Therefore, if the detection signal of the displacement sensor 11 is sent to the controller, the radial load applied to the rolling bearing unit in which the displacement sensor 11 is incorporated can be obtained from a relational expression or a map obtained beforehand through experiments or the like. Based on the load applied to each rolling bearing unit thus obtained, the ABS is appropriately controlled and the driver is informed of the poor loading state.

  In the conventional structure shown in FIG. 9, in addition to the load applied to the rolling bearing unit, the rotational speed of the hub 2 can also be detected. For this purpose, the sensor rotor 13 is fitted and fixed to the inner end portion of the inner ring 6, and the rotational speed detection sensor 15 is supported by a cover 14 attached to the inner end opening of the outer ring 1. The detection portion of the rotational speed detection sensor 15 is opposed to the detection portion of the sensor rotor 13 via a detection gap.

  When the rolling bearing unit incorporating the rotational speed detection device as described above is used, the sensor rotor 13 rotates together with the hub 2 to which the wheel is fixed, and the detected portion of the sensor rotor 13 is connected to the rotational speed detection sensor 15. When traveling in the vicinity of the detection unit, the output of the rotational speed detection sensor 15 changes. The frequency at which the output of the rotational speed detection sensor 15 changes in this way is proportional to the rotational speed of the wheel. Therefore, if the output signal of the rotational speed detection sensor 15 is sent to a controller (not shown), ABS and TCS can be controlled appropriately.

  The rolling bearing unit with a load measuring device of the first example of the conventional structure as described above is for measuring the radial load applied to the rolling bearing unit, but the structure for measuring the axial load applied to the rolling bearing unit is also, It is described in Patent Document 2 and the like and has been conventionally known. FIG. 10 shows a rolling bearing unit with a load measuring device described in Patent Document 2 for measuring an axial load. In the case of the second example of the conventional structure, the rotation side flange 3a for supporting the wheel is fixed to the outer peripheral surface of the outer end portion of the hub 2a which is a rotating wheel. In addition, a fixed-side flange 17 for fixing the outer ring 1a to the knuckle 16 constituting the suspension device is fixed to the outer peripheral surface of the outer ring 1a which is a stationary wheel. A plurality of rolling rings are respectively provided between the double row outer ring raceways 7 and 7 formed on the inner peripheral surface of the outer ring 1a and the double row inner ring raceways 8 and 8 formed on the outer peripheral surface of the hub 2a. By providing the moving bodies 9a and 9b so as to be able to roll, the hub 2a is rotatably supported on the inner diameter side of the outer ring 1a.

  Further, a load sensor 20 is attached to a part surrounding the screw hole 19 for screwing the bolt 18 for connecting the fixed side flange 17 to the knuckle 16 at a plurality of positions on the inner side surface of the fixed side flange 17. Has been established. Each load sensor 20 is sandwiched between the outer side surface of the knuckle 16 and the inner side surface of the fixed-side flange 17 in a state where the outer ring 1 a is supported and fixed to the knuckle 16.

  In the case of the load measuring device of the rolling bearing unit of the second example having such a conventional structure, when an axial load is applied between a wheel (not shown) and the knuckle 16, the outer surface of the knuckle 16 and the fixed side flange 17 The inner surface strongly presses the load sensors 20 from both sides in the axial direction. Therefore, the axial load applied between the wheel and the knuckle 16 can be obtained by summing up the measured values of the load sensors 20. Although not shown, Patent Document 3 describes a method of obtaining the revolution speed of the rolling element from the vibration frequency of a member corresponding to an outer ring having a reduced rigidity, and measuring the axial load applied to the rolling bearing. ing.

  In the case of the first example of the conventional structure shown in FIG. 9, the load applied to the rolling bearing unit is measured by measuring the displacement in the radial direction between the outer ring 1 and the hub 2 by the displacement sensor 11. However, since the displacement amount in the radial direction is small, it is necessary to use a highly accurate displacement sensor 11 in order to obtain this load with high accuracy. Since high-precision non-contact sensors are expensive, it is inevitable that the cost of the entire rolling bearing unit with a load measuring device increases.

  In the case of the second example of the conventional structure shown in FIG. 10 described above, it is necessary to provide as many load sensors 20 as bolts 18 for supporting and fixing the outer ring 1a to the knuckle 16. For this reason, coupled with the fact that the load sensor 20 itself is expensive, it is inevitable that the cost of the entire load measuring device of the rolling bearing unit is considerably increased. Further, the method described in Patent Document 3 requires that the rigidity of a part of the outer ring equivalent member be lowered, and it may be difficult to ensure the durability of the outer ring equivalent member.

  In view of such circumstances, the present inventors have previously described this rolling bearing unit based on the revolution speed of a pair of rolling elements (balls) constituting a rolling bearing unit which is a double row angular ball bearing. An invention relating to a load measuring device for a rolling bearing unit that measures a radial load or an axial load applied to the bearing is performed (Japanese Patent Application Nos. 2003-171715 and 172483). In the case of the load measuring device of the rolling bearing unit according to the present invention, in order to obtain the revolution speed of the rolling elements in each row, it is possible to detect the rotation speed of the cage holding the rolling elements in each row. Is effective in terms of obtaining high resolution. For this purpose, in the prior invention, the encoder is supported and fixed to the cage (or the cage itself has a function as an encoder), and the detection portion of the rotation detection sensor is opposed to the detection surface of the encoder. The rotational speed of the cage is detected.

  However, between the rolling surfaces of the rolling elements in each row and the inner surfaces of the pockets of the cages in each row, the rolling elements are allowed to roll and to the rolling surfaces of these rolling elements. Since there is a gap for allowing the grease to adhere, each of the cages may be displaced in the radial direction and the axial direction while rotating. As a result of such displacement, when the distance between the detected surface of the encoder and the detection unit of the rotation detection sensor changes, the rotational speed of the cages in each row, and thus the rolling elements in each row, The revolution speed cannot be measured accurately.

  Such a problem may occur not only when the rotational speed of the cage is measured by a load measuring device for a rolling bearing unit that measures a radial load or an axial load applied to the rolling bearing unit. That is, in a rotational speed detection device for detecting the rotational speed of various rotating members, when the distance between the detected surface of the encoder supported and fixed to the member whose rotational speed is to be detected and the detection portion of the rotational detection sensor varies. The detection accuracy of the rotational speed is deteriorated.

JP 2001-21577 A Japanese Patent Laid-Open No. 3-209016 Japanese Patent Publication No.62-3365

  In view of the circumstances as described above, the present invention requires the rotational speed of the rotating member provided with this encoder for control even if the distance between the detected surface of the encoder and the detecting portion of the rotation detecting sensor fluctuates. The present invention was invented to realize a rotational speed detection device capable of measuring while ensuring the accuracy.

The rotational speed detection device of the present invention includes an encoder, a rotational detection sensor, and a calculator, as in the conventional rotational speed detection device.
Among these, the encoder is supported and fixed to the rotating member and rotates together with the rotating member, and the characteristics are alternately changed in the circumferential direction.
Further, the rotation detection sensor is provided in a state where the detection portion faces the detection surface of the encoder.
Further, the computing unit calculates a rotation speed of the rotating member based on an output signal sent from the rotation detection sensor.

In particular, in the rotation speed detection device of the present invention, the rotation detection sensor is a linear sensor that sends out an analog signal in response to the change in the characteristics.
The arithmetic unit includes a comparator that compares an analog signal sent from the rotation detection sensor with a threshold (threshold level) and converts the analog signal into a digital signal.
The comparator has a function of changing the threshold according to the distance between the detection target surface of the encoder and the detection unit of the rotation detection sensor.

  The rotational speed detection device of the present invention configured as described above can accurately detect the rotational speed of the rotating member that supports and fixes the encoder even when the distance between the detected surface of the encoder and the detection portion of the rotation detection sensor changes. Is required. That is, when the distance changes, the amplitude of the analog signal sent out from the rotation detection sensor changes corresponding to the change in the characteristics of the encoder. Therefore, when the threshold value of the comparator of the arithmetic unit provided for converting this analog signal into a digital signal is constant, the period of the obtained digital signal and the period of the original analog signal are not proportional. On the other hand, in the case of the rotational speed detection device of the present invention, the threshold value is changed according to the distance between the detected surface of the encoder and the detection unit of the rotation detection sensor. The period and the period of the original analog signal can be made proportional.

When the present invention is implemented, preferably, as described in claim 2, a permanent magnet in which S poles and N poles are alternately arranged at equal intervals on the detection surface is used as an encoder. A rotation detection sensor that outputs a sinusoidal analog signal that changes in accordance with the density and direction of the magnetic flux reaching the detection unit is used. Further, a comparator having a function of increasing the absolute value of the threshold as the amplitude of the analog signal is increased is used.
With this configuration, it is possible to reliably perform the operation of making the period of the obtained digital signal proportional to the period of the original analog signal.

Preferably, as described in claim 3, the rotating member is provided between a pair of race rings constituting the rolling bearing unit, and accompanying the revolution of the rolling elements held in a plurality of pockets. A rotating cage.
There is a gap between the inner surface of each pocket and the rolling surface of each rolling element so that a lubricant such as grease adheres to the rolling surface of each rolling element. Based on the existence of the gap, the cage is unavoidably displaced in the radial direction and the axial direction. Therefore, when detecting the rotation speed of the cage, the period of the obtained digital signal and the period of the original analog signal are changed regardless of the change in the distance between the detection target surface of the encoder and the detection unit of the rotation detection sensor. It is very important to make the ratio proportional. That is, when detecting the rotational speed of the cage, the action and effect of the present invention are particularly remarkable.

In particular, as described in claim 4, when the detected surface is one side surface of the encoder in the axial direction, it is important to implement the present invention.
When the encoder is supported and fixed to a part of the cage, the detection surface of this encoder and the rotation detection sensor can be detected regardless of the surface to be detected (regardless of the circumferential surface or one side surface in the axial direction). The amplitude of the analog signal sent out from the rotation detection sensor changes based on the change in the distance to the unit, and the period of the obtained digital signal is not proportional to the period of the original analog signal. However, in the case where the encoder and the detection unit of the rotation detection sensor are arranged in a limited space inside the rolling bearing, the degree of freedom in design increases when the detected surface is one side surface in the axial direction of the encoder.

Further, as a preferred embodiment of the present invention, a load measuring device for a rolling bearing unit as described in claim 5 is conceivable.
The load measuring device of the rolling bearing unit includes a stationary wheel, a rotating wheel, a plurality of rolling elements, a pair of rotational speed detecting devices, and a calculator.
Of these, the stationary wheels do not rotate during use.
The rotating wheel is disposed concentrically with the stationary wheel and rotates when in use.
In addition, each of the above rolling elements has a plurality of each between a stationary side raceway and a rotational side raceway formed in two rows each in a portion where the stationary wheel and the rotating wheel face each other. And the direction of the contact angle is opposite to each other.
Each of the rotational speed detection devices is for detecting the rotational speed of a pair of cages holding the rolling elements in both rows.
The computing unit calculates a load applied between the stationary wheel and the rotating wheel based on the rotating speed of the pair of cages detected by the rotating speed detecting devices.
When the present invention is applied to such a load measuring device for a rolling bearing unit, each of the rotational speed detecting devices has a structure described in any one of the first to fourth aspects.
More preferably, as described in claim 6, the rotating wheel is a hub that rotates together with the wheel of an automobile while the wheel of the automobile is fixed.

  1 to 4 show an embodiment of the present invention. In this embodiment, the load (radial load and axial load) applied to the rolling bearing unit for supporting the driven wheel of the automobile (the front wheel of the FR car, the RR car, the MD car, the rear wheel of the FF car) is measured. A case where the present invention is applied to a load measuring device of a rolling bearing unit is shown. Since the configuration and operation of the rolling bearing unit itself are the same as those of the conventional structure shown in FIG. 9, the same reference numerals are given to the same parts, and the redundant description is omitted or simplified. The description will focus on the characteristic part.

Formed on the outer peripheral surface of the hub 2 that is a rotating wheel, each formed on the inner peripheral surface of the double-row angular inner ring races 8 and 8 that are rotating side tracks, and the outer ring 1 that is a stationary ring, respectively. The rolling elements (balls) 9a and 9b are divided into double rows (two rows) between the double row angular outer ring races 7 and 7, which are tracks, and a plurality of cages 21a are provided for each row. The hub 2 is rotatably supported on the inner diameter side of the outer ring 1 by being provided so as to be able to roll while being held by the spring 21b. In this state, the rolling elements 9a and 9b in each row are provided with contact angles α _a and α _b (FIG. 2) in the opposite directions and the same magnitude, so that the double-row angular contact of the rear combination type Configures a ball bearing. Sufficient preload is applied to the rolling elements 9a and 9b in each row so as not to be lost due to an axial load applied during use. When such a rolling bearing unit is used, the outer ring 1 is supported and fixed to a suspension device, and a braking disk and a wheel of a wheel are supported and fixed to the rotation side flange 3 of the hub 2.

  A mounting hole 10a is formed in the axially intermediate portion of the outer ring 1 constituting the rolling bearing unit as described above between the double row outer ring raceways 7 and 7 so as to penetrate the outer ring 1 in the radial direction. ing. Then, the sensor unit 22 is inserted into the mounting hole 10 a from the radially outer side of the outer ring 1 to the inner side, and the detection unit 23 provided at the tip of the sensor unit 22 is inserted from the inner peripheral surface of the outer ring 1. It is protruding. The detection unit 23 is provided with a pair of revolution speed detection sensors 24a and 24b, each of which is a rotation detection sensor, and one rotation speed detection sensor 15a.

  Among these, the revolution speed detection sensors 24a and 24b are for measuring the revolution speed of the rolling elements 9a and 9b arranged in the double row. Each detection surface is arrange | positioned on the both sides | surfaces regarding (the left-right direction of FIGS. 1-2). In this example, the revolution speed detection sensors 24a and 24b detect the revolution speeds of the rolling elements 9a and 9b arranged in the double row as the rotation speeds of the cages 21a and 21b. For this reason, in the case of this example, the rim portions 25 and 25 constituting the retainers 21a and 21b are arranged on the sides facing each other. Then, revolving speed detection encoders 26a and 26b each having a ring shape are attached and supported on the surfaces of the rim portions 25 and 25 facing each other over the entire circumference. The characteristics of the detected surfaces of the encoders 26a and 26b are changed alternately and at equal intervals in the circumferential direction, and the rotational speeds of the cages 21a and 21b are changed by the revolution speed detection sensors 24a and 24b. Detectable.

  For this purpose, the detection surfaces of the revolution speed detection sensors 24a and 24b are made to face each other and face to face, which are the detection surfaces of the revolution speed detection encoders 26a and 26b. The distances (detection gaps) between the detected surfaces of the revolution speed detection encoders 26a and 26b and the detection surfaces of the revolution speed detection sensors 24a and 24b are the inner surfaces of the pockets of the retainers 21a and 21b. And larger than a pocket gap, which is a gap between the rolling elements 9a and 9b, and preferably 2 mm or less. If the detection gap is equal to or less than the pocket gap, it is not preferable because the detected surface and the detection surface may rub against each other when the cages 21a and 21b are displaced by the pocket gap. On the contrary, if the detection gap exceeds 2 mm, it becomes difficult to accurately measure the rotations of the revolution speed detecting encoders 26a and 26b by the revolution speed detecting sensors 24a and 24b.

  On the other hand, the rotational speed detection sensor 15a is for measuring the rotational speed of the hub 2, which is a rotating wheel, and is provided on the tip surface of the detecting portion 23, that is, on the radially inner end surface of the outer ring 1. The detection surface is arranged. A cylindrical rotational speed detecting encoder 27 is externally fitted and fixed between the double-row inner ring raceways 8 and 8 at the intermediate portion of the hub 2. The detection surface of the rotation speed detection sensor 15a is opposed to the outer peripheral surface, which is the detection surface of the rotation speed detection encoder 27. The characteristics of the surface to be detected of the rotational speed detecting encoder 27 are changed alternately and at equal intervals in the circumferential direction so that the rotational speed of the hub 2 can be detected by the rotational speed detecting sensor 15a. The measurement gap between the outer peripheral surface of the rotational speed detection encoder 27 and the detection surface of the rotational speed detection sensor 15a is also suppressed to 2 mm or less.

  As the encoders 26a, 26b, and 27, those of various structures that have been used for detecting the rotational speed of the wheel in order to obtain ABS and TCS control signals can be used. For example, as the encoders 26a, 26b, 27, multipole magnets having N poles and S poles alternately arranged at equal intervals on the detection surface (side surface or outer peripheral surface) can be preferably used.

  In the case of this example, as each of the revolution speed detection encoders 26a and 26b, an annular permanent magnet in which S poles and N poles are alternately arranged at equal intervals on the side surface in the axial direction, which is a detected surface. I use it. Such revolving speed detecting encoders 26a and 26b are bonded and fixed to the side surfaces of the rim portions 25 and 25 of the holders 21a and 21b, which are separately manufactured, or these holders 21a and 21b. When injection molding is performed, insert molding is performed by setting each of the revolution speed detecting encoders 26a and 26b in the cavity. Which method is adopted is selected according to the cost, the required bond strength, and the like.

  In addition, as each of the revolution speed detection sensors 24a and 24b and the rotation speed detection sensor 15a, which are sensors for detecting the rotation speed, magnetic rotation speed detection sensors can be preferably used. Further, as this magnetic type rotational speed detection sensor, an active type incorporating a magnetic detection element such as a Hall element, Hall IC, magnetoresistive element (MR element, GMR element), MI element or the like is used. In order to construct an active type rotational speed detection sensor incorporating such a magnetic detection element, for example, one side surface of the magnetic detection element is directly or via a stator made of a magnetic material, the magnetization direction of the permanent magnet. Abut against one end surface (when a magnetic material encoder is used), and the other side surface of the magnetic detection element directly or via a magnetic material stator to the detection surface of each encoder 26a, 26b, 27 Make them face each other. In this example, since a permanent magnet encoder is used, a permanent magnet on the sensor side is unnecessary.

In the case of the load measuring device of the rolling bearing unit of the present embodiment, the detection signals of the sensors 24a, 24b and 15a are input to a calculator (not shown). Based on the detection signals sent from the sensors 24a, 24b, and 15a, the computing unit applies one or both of the radial load and the axial load applied between the outer ring 1 and the hub 2. Is calculated. For example, when the radial load is obtained, the computing unit obtains the sum of the revolution speeds of the rolling elements 9a and 9b in each row detected by the revolution speed detection sensors 24a and 24b, and the sum and the rotation speed. The radial load is calculated based on the ratio to the rotational speed of the hub 2 detected by the detection sensor 15a. The axial load is determined based on the ratio of the revolution speeds of the rolling elements 9a and 9b in the respective rows detected by the respective revolution speed detection sensors 24a and 24b, or the revolutions of the rolling elements 9a and 9b in the respective rows. A speed difference is obtained and calculated based on a ratio between this difference and the rotational speed of the hub 2 detected by the rotational speed detection sensor 15a. This point will be described with reference to FIG. In the following description, it is assumed that the contact angles α _a and α _b of the rolling elements 9 a and 9 b in each row are the same in a state where the axial load F _a is not applied.

FIG. 4 schematically shows the rolling bearing unit for supporting the wheel shown in FIG. 1 and shows the action state of the load. Preloads F ₀ and F ₀ are applied to the rolling elements 9 a and 9 b arranged in a double row between the double row inner ring raceways 8 and 8 and the double row outer ring raceways 7 and 7. Further, a radial load F _r is applied to the rolling bearing unit during use due to the weight of the vehicle body or the like. Further, by the centrifugal force or the like applied during cornering, applied is the axial load F _a. These preloads F ₀ , F ₀ , radial load F _r , and axial load F _a all affect the contact angles α (α _a , α _b ) of the rolling elements 9a, 9b. Then, the contact angle alpha _a, the alpha _b is changed, these rolling elements 9a, the revolution speed n _c of 9b changes. The diameter of the pitch circle of each of these rolling elements 9a, 9b is D, the diameter of each of these rolling elements 9a, 9b is d, the rotational speed of the hub 2 provided with each of the inner ring raceways 8, 8 is n _i , When the rotational speed of the outer race 1 provided with the outer ring raceway 7, 7 and n _o, the revolution speed n _c is expressed by the following equation (1).
n _c = {1− (d · cos α / D) · (n _i / 2)} + {1+ (d · cos α / D) · (n _o / 2)} --- (1)

As is clear from this equation (1), the rolling elements 9a, the revolution speed n _c of 9b, these rolling elements 9a, the contact angle α (α _a, α _b) of 9b varies in response to changes in As described above, the contact angles α _a and α _b change according to the radial load F _r and the axial load F _a . Thus the revolution speed n _c is changed according to these radial load F _r and axial load F _a. In this example, since the hub 2 rotates and the outer ring 1 does not rotate, specifically, as the radial load F _r increases, the revolution speed nc _decreases . Further, with respect to the axial load F _a, the revolution speed of the column that supports the axial load F _a faster, revolution speeds of the columns that do not support this axial load F _a is delayed. Therefore, the radial load F _r and the axial load F _a can be obtained based on the revolution speed n _c .

However, the contact angle α which leads to a change in the revolution speed n _c, as well as the radial load F _r and the axial load F _a is changed while associated with each other, also varies the preload F _0, F ₀ To do. Also, the revolution speed n _c is changed in proportion to the rotational speed n _i of the hub 2. Therefore, if the radial load F _r , the axial load F _a , the preload F ₀ , F ₀ , and the rotational speed n _i of the hub 2 are not considered in total, it is possible to accurately obtain the revolution speed n _c. Can not. Of these, the preloads F ₀ and F ₀ do not change according to the operating state, so it is easy to eliminate the influence by initial setting or the like. On the other hand, the radial load F _r , the axial load F _a , and the rotational speed n _i of the hub 2 constantly change according to the operating state, so that the influence cannot be eliminated by initial setting or the like.

In the case of the present embodiment in view of such circumstances, as described above, when the radial load F _r is obtained, the rolling elements 9a of the respective rows detected by the respective revolution speed detecting sensors 24a, 24b, by obtaining the sum of the revolution speeds of 9b, it is less affected in the axial load F _a. Further, when determining the axial load F _a , the influence of the radial load F _r is reduced by determining the difference in revolution speed between the rolling elements 9 a and 9 b in each row. Further calculation, in any case, and the sum or difference, the ratio to the radial load F _r or the axial load F _a on the basis of the rotational speed n _i of the hub 2 to the rotational speed detecting sensor 15a detects by and by eliminating the influence of the rotational speed n _i of the hub 2. However, the axial load F _a, when calculating on the basis of the rolling elements 9a, 9b ratio of the revolution speed of said each row, the rotational speed n _i of the hub 2 is not necessarily required.

There are various other methods for calculating one or both of the radial load F _r and the axial load F _a based on the signals of the revolution speed detection sensors 24a and 24b. Such a method is described in detail in the above-mentioned Japanese Patent Application Nos. 2003-171715 and 172484, and is not related to the gist of the present invention.
However, whichever load is obtained by any method, the revolution speed of the rolling elements 9a, 9b in each row can be accurately obtained based on the detection signals of the respective revolution speed detection sensors 24a, 24b. It is important to increase the load measurement accuracy.

  On the other hand, if the detection signals of the revolution speed detection sensors 24a and 24b are not appropriately processed, the detection units of the revolution speed detection sensors 24a and 24b and the revolution speed detection encoders 26a and 26b An error based on a change in the distance to the surface to be detected enters, and the revolution speeds of the rolling elements 9a and 9b in each row cannot be obtained accurately. In order to prevent such an error from entering, in the case of this embodiment, as the revolution speed detecting sensors 24a and 24b, the characteristics of the detected surfaces of the revolution speed detecting encoders 26a and 26b are changed. A linear sensor that sends out an analog signal (a voltage signal that changes in a sine wave shape) corresponding to (switching between the S pole and the N pole) is used.

Further, the output signals of the respective revolution speed detection sensors 24a and 24b are processed, and the rotational speeds of the cages 21a and 21b (revolution speeds of the rolling elements 9a and 9b in the respective rows), and further the radial loads. A comparator is incorporated in the arithmetic unit for calculating F _r or the axial load F _a . This comparator functions as an A / D converter that compares the analog signal sent from each of the revolution speed detection sensors 24a and 24b with a threshold value and converts the analog signal into a digital signal. Further, the comparator has a function of changing the threshold value in accordance with the distance between the detected surface of each of the revolution speed detecting encoders 26a and 26b and the detecting portion of each of the revolution speed detecting sensors 24a and 24b. Have. In the case of the present embodiment, by adopting such a configuration, the distance between the detected surface of each of the revolution speed detection encoders 26a and 26b and the detection portion of each of the revolution speed detection sensors 24a and 24b changes. even if we, each retainer 21a, the rotational speed of 21b (each row of the rolling elements 9a, 9b revolution speeds of), even the radial load F _r or the axial load F _a, as can be calculated accurately I have to.

This point will be described with reference to FIGS. First, a standard operation when an analog signal is converted into a digital signal by a comparator having a threshold value will be described with reference to FIG. In the state shown in FIG. 6A, the encoder rotates at a constant speed without changing the radial direction or the axial direction (with the distance between the detection surface and the detection unit being constant), and the rotation is detected. It shows a state in which the period and amplitude of the analog signal sent from the sensor do not change. In this case, assuming that the voltage of the analog signal changes between ± V ₁ , the threshold value of the comparator is ± V ₂ (| V ₂ | <| V ₁ |, for example, | V ₂ | = 0. .5 | V ₁ |). The comparator performs switching (ON and OFF are alternately repeated) every time the analog signal passes both the threshold values, and obtains a digital signal as shown in FIG. 6B. In such a state shown in FIG. 6, since the period and amplitude of the analog signal do not change, the period of the analog signal that is the original signal and the obtained digital signal can be obtained even if the threshold value is kept constant. The period of Accordingly, the rotational speed of each of the cages 21a and 21b (the revolution speed of the rolling elements 9a and 9b in each row), and further the radial load F _r or the axial load F _a can be accurately calculated without any change.

On the other hand, the encoder fluctuates in the radial direction or the axial direction (in the structure shown in FIGS. 1 and 2, the axial direction), and the detected surfaces of the revolution speed detection encoders 26a and 26b and the revolution speed detection sensors 24a. 24b, the amplitudes of the analog signals sent from the revolution speed detection sensors 24a and 24b fluctuate as shown in FIG. 7A. That is, when the distance is shortened, the density of magnetic flux reaching the detection portions of the revolution speed detection sensors 24a and 24b increases, and the voltage of the output signal of each of the revolution speed detection sensors 24a and 24b increases (the amplitude increases). growing. Further, as the distance becomes longer, the density of magnetic flux reaching the detection portions of the respective revolution speed detection sensors 24a and 24b becomes lower, and the voltage of the output signal of each of the revolution speed detection sensors 24a and 24b becomes lower (the amplitude becomes smaller). )Become. In such a case, when the digital signal is obtained while keeping the threshold value of the comparator constant, the period of the analog signal, which is the original signal, is obtained as shown in FIG. The period of the digital signal does not match. Therefore, as it is, each of the retainer 21a, the rotational speed of 21b (each row of the rolling elements 9a, the revolution speed of 9b), even the radial load F _r or the axial load F _a, can not be accurately calculated .

On the other hand, in the case of the present embodiment, as shown by thin lines A and B in FIG. 5A according to the amplitude of the analog signal sent out from each of the revolution speed detection sensors 24a and 24b, the threshold value is set. Change the value of. Therefore, the rotational speeds of the cages 21a and 21b (revolving speeds of the rolling elements 9a and 9b in each row), which support and fix the revolution speed detection encoders 26a and 26b, and the radial load F _r or the axial load F _a can be accurately calculated. That is, the revolution speed detection sensors 24a and 24b output sinusoidal analog signals as shown by the full line C in FIG. 5, which change according to the density and direction of the magnetic flux reaching the respective detection units. The comparator increases the absolute value of the threshold as the amplitude of the analog signal increases. For example, as shown in FIG. 5A, this comparator sets a value of 20% of the immediately preceding peak value as a threshold value (B _op , B _rp ) by reversing ±. For example, in FIG. 5A, | V ₂₁ | = 0.2 | V ₁₁ |, | V ₂₂ | = 0.2 | V ₁₂ |, and | V ₂₃ | = 0.2 | V ₁₃ | The center position (reference) of the magnetic flux density O in FIG. 5 differs depending on the output form of the revolution speed detection sensors 24a and 24b. That is, when each of the revolution speed detection sensors 24a and 24b has a 0V center (0V output at a magnetic flux density O) and a positive / negative output, the center position becomes 0V. On the other hand, when the outputs at the magnetic flux density O of the revolution speed detection sensors 24a and 24b are a single positive output and a single negative output, the center position (threshold center) is the offset voltage V _off .

  As described above, the amplitude of the analog signal sent out from each of the revolution speed detection sensors 24a and 24b is the same as that of the revolution speed detection sensors 24a and 24b and the revolution speed detection encoders 26a and 26b. It changes according to the distance to the surface to be detected. In the case of the present embodiment, the threshold value of the comparator is changed in accordance with the amplitude of the analog signal sent from each of the revolution speed detection sensors 24a and 24b, which changes in this way. The period of the digital signal as shown in FIG. 5B and the period of the original analog signal as shown in FIG. 5A can be made substantially proportional (match).

  FIG. 8 shows the result of a simulation performed to confirm the effect of this embodiment. The vertical axis of FIG. 8 indicates the S pole and N pole of the pitch obtained based on the digital signal obtained by passing through the comparator and arranged on the detected surface in each of the revolution speed detecting encoders 26a and 26b. The horizontal axis represents the error relative to the pitch, and the horizontal axis represents the signal period. The solid line a in FIG. 8 shows the same broken line b when the threshold value is changed in accordance with the fluctuation in the amplitude of the analog signal as in the present embodiment shown in FIG. 5, regardless of the fluctuation in the amplitude of the analog signal. The results are shown when the threshold value is constant. As is clear from the description of FIG. 8, the threshold value of the comparator for converting the analog signals sent from the respective revolution speed detection sensors 24a and 24b into digital signals is shown in FIG. In this manner, if the speed is changed in accordance with the amplitude of the analog signal, an accurate speed can be obtained regardless of fluctuations in the analog signals sent from the respective revolution speed detection sensors 24a and 24b.

  In particular, when the load applied to the rolling bearing unit is obtained based on the change in the revolution speed of the rolling elements in each row as in this embodiment, the change in the revolution speed is 10% or less at the maximum. The effect of eliminating the influence of the pitch error based on the fluctuation of the signal amplitude is great. Note that when a sensor that directly sends a digital signal is used as the revolution speed detection sensor, the detection part of the revolution speed detection sensor and the revolution speed detection encoder are added to the digital signal sent from the revolution speed detection sensor. Although an error based on a change in the distance to the detection surface enters, a signal corresponding to this distance cannot be obtained. Therefore, when implementing the present invention, it is essential to send an analog signal from a rotation detection sensor such as an encoder for detecting revolution speed to the comparator. It should be noted that the change of the threshold value in the comparator portion is not limited to the method of the embodiment as long as the error based on the change in the distance can be reduced.

  The rotational speed detecting device of the present invention is not limited to the load measuring device of the rolling bearing unit for measuring the load applied to the rolling bearing unit that supports the wheel of the automobile, as shown in the embodiment, but of various rotating machinery devices. This can be used to detect the rotational speed of the rotating member. In this case, the member that supports and fixes the encoder is not limited to a member that may move far and away with respect to the detection unit of the rotation detection sensor, such as a cage, but to the detection unit of the rotation detection sensor such as a rotation shaft. And a rotating member that does not move far and away. In this case, it is not necessary to particularly increase the accuracy of assembly of the encoder to the rotating member, and the cost required for assembly can be reduced.

Sectional drawing of the rolling bearing unit incorporating the rotation detection apparatus for load measurements which shows the Example of this invention. The A section enlarged view of FIG. FIG. 3 is a schematic diagram showing a cage, rolling elements, an encoder, and a rotation detection sensor as seen from above in FIG. 2. The schematic diagram of a rolling bearing unit for demonstrating the reason which can measure a load based on rotational speed. In the case of the present invention, even if the amplitude of the analog signal sent out from the rotation detection sensor changes, the line indicating the reason that the period of the analog signal can be substantially proportional to the period of the digital signal obtained from the analog signal. Figure. The diagram which shows the state which acquires a digital signal from the analog signal sent out from a rotation detection sensor in the case of the conventional structure. The diagram which shows the reason why the period of this analog signal is not proportional to the period of the digital signal obtained from this analog signal when the amplitude of the analog signal sent from the rotation detection sensor changes in the case of the conventional structure. A line indicating the difference in the degree of deviation between the period of the analog signal and the period of the digital signal obtained from the analog signal between the case of the present invention shown in FIG. 5 and the case of the conventional structure shown in FIG. Figure. Sectional drawing of the rolling bearing unit which incorporated the sensor for radial load measurement known conventionally. Sectional drawing of the rolling bearing unit which incorporated the sensor for axial load measurement conventionally known.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a Outer ring 2, 2a Hub 3, 3a Rotation side flange 4 Hub body 5 Nut 6 Inner ring 7 Outer ring raceway 8 Inner ring raceway 9a, 9b Rolling element 10, 10a Mounting hole 11 Displacement sensor 12 Sensor ring 13 Sensor rotor 14 Cover 15, 15a Rotational speed detection sensor 16 Knuckle 17 Fixed flange 18 Bolt 19 Screw hole 20 Load sensor 21a, 21b Cage 22 Sensor unit 23 Detection unit 24a, 24b Revolution speed detection sensor 25, 25a Rim part 26a, 26b Revolution speed detection Encoder 27 Rotation speed detection encoder

Claims (6)

  An encoder that is supported and fixed to a rotating member and rotates together with the rotating member, the characteristics of which are alternately changed with respect to the circumferential direction, and a rotation detection sensor that is provided in a state in which the detecting portion faces the detected surface of the encoder And a calculator for calculating the rotation speed of the rotating member based on an output signal sent from the rotation detection sensor, wherein the rotation detection sensor responds to a change in the characteristic. A linear sensor that sends out an analog signal, and the arithmetic unit includes a comparator that compares the analog signal sent from the rotation detection sensor with a threshold value and converts the analog signal into a digital signal. The comparator has a function of changing the threshold value in accordance with the distance between the detected surface of the encoder and the detection unit of the rotation detection sensor. Speed detecting apparatus according to claim.   The encoder is a permanent magnet in which S poles and N poles are alternately arranged at equal intervals on the surface to be detected, and the rotation detection sensor has a sinusoidal shape that changes according to the density and direction of the magnetic flux reaching the detection unit. The rotational speed detection apparatus according to claim 1, which outputs an analog signal, and the comparator has a function of increasing the absolute value of the threshold as the amplitude of the analog signal increases.   The rotating member is a cage that is provided between a pair of bearing rings that constitute a rolling bearing unit and that rotates in accordance with the revolution of rolling elements held in a plurality of pockets. A rotation speed detection device as described above.   The rotational speed detection apparatus according to any one of claims 1 to 3, wherein the detected surface is one side surface of the encoder in the axial direction.   A stationary wheel that does not rotate even when in use, a rotating wheel that is arranged concentrically with the stationary wheel and that rotates when in use, and a stationary side track that is formed in two rows on opposite portions of the stationary wheel and the rotating wheel. A plurality of rolling elements provided so as to be able to roll with each other between the two rows, with the direction of the contact angle being opposite to each other, and the rolling elements in both rows are held between the rotation side track and each of the plurality of rolling elements. A pair of rotation speed detection devices for detecting the rotation speed of a pair of cages, and the stationary wheel and the rotation wheel based on the rotation speeds of the pair of cages detected by the rotation speed detection devices. A load measuring device for a rolling bearing unit, wherein each of the rotational speed detecting devices is a rotational speed detecting device according to any one of claims 1 to 4. The load measuring device for a rolling bearing unit according to claim 5, wherein the rotating wheel is a hub that rotates together with the wheel of an automobile while the wheel is fixed.

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