JP2008232621A - Bearing load measurement device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing load measurement device capable of highly accurately and correctly measuring a load exerted on a bearing by highly accurately and correctly computing a ratio of phase differences even if the rotational speed of the bearing is not constant. <P>SOLUTION: The device includes an encoder fixed to a turning wheel and having a plane to be detected of which characteristics change along a circumferential direction; a detector for detecting changes in the characteristics of the plane to be detected; and a computing unit for computing a load exerted on a bearing by performing prescribed computations on detection signals from the detector. A plurality of rotational speed sensors opposed to the plane to be detected are arranged in the detector along an axial direction. Each rotational speed sensor outputs detection signals (A-phase signals and B-phase signals) corresponding to changes in the characteristics of the plane to be detected with the rotation of the encoder. The computing unit measures times (x1, y1, x2, y2, x3, y3, x4...) of phase differences between detection signals, computes a plurality of ratios P and Q of phase differences in different elapsed times on the basis of results of this measurement, and computes a load exerted on the bearing by computing their average R=(P+Q)/2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a load measuring device for a bearing used, for example, to rotatably support a wheel of an automobile with respect to a suspension device, and more particularly to improvement of a technique for measuring a load applied to the bearing in an axial direction.

  Conventionally, various bearings are known for rotatably supporting wheels (for example, disc wheels) of various vehicles such as automobiles with respect to a vehicle body (for example, a suspension device (suspension)). Note that there are two types of bearings, one for driving wheels and one for driven wheels. FIG. 1 (a) shows a bearing for driven wheels as an example.

  Such a bearing is fixed to the vehicle body side and is always kept in a non-rotating state, and a rotating wheel that is disposed facing the inside of the stationary wheel 2 and is connected to the wheel side and rotates together with the wheel. (Inner ring) 4, and a plurality of rolling elements 6 and 8 are incorporated between the stationary wheel 2 and the rotating wheel 4 in a double row (for example, two rows). An annular raceway groove 2s continuous in the circumferential direction is formed in a double row (for example, two rows) on the inner periphery of the stationary wheel 2, while each raceway groove of the stationary wheel 2 is provided on the outer periphery of the rotating wheel 4. Opposite 2s, raceway grooves 4s are formed in double rows (2 rows). The plurality of rolling elements 6 and 8 are incorporated between the raceway grooves 2 s and 4 s of the stationary wheel 2 and the rotating wheel 4 so as to freely roll.

  Further, a seal member (for example, a lip seal 10a on the wheel side and a cover 10b on the vehicle body side) for sealing the inside of the bearing from the outside of the bearing is provided between the stationary wheel 2 and the rotating wheel 4. The lip seal 10a is slidably positioned with respect to the rotating wheel 4 while being fixed to the wheel side of the stationary wheel 2. On the other hand, the cover 10 b has a disk shape that can be sealed so as to cover the entire vehicle body side of the stationary wheel 2, and the periphery thereof is fixed to the vehicle body side of the stationary wheel 2. In the drawings, balls are illustrated as the rolling elements 6 and 8, but rollers may be applied depending on the configuration and type of the bearing.

  The stationary wheel 2 is integrally formed with a fixing flange 2a that protrudes outward from the outer peripheral surface thereof. In this case, the outer ring 2 can be fixed to a suspension device (knuckle) (not shown) by inserting a fixing bolt (not shown) into the fixing hole 2b of the fixing flange 2a and fastening it to the vehicle body side. On the other hand, the rotating wheel 4 is provided with, for example, a substantially cylindrical hub 12 that rotates while supporting a disk wheel (not shown) of an automobile, and the hub 12 has a hub flange 12a to which the disk wheel is fixed. Is protruding.

  The hub flange 12a extends outward (radially outward of the hub 12) beyond the stationary ring 2, and a plurality of hub flanges 12a are arranged at predetermined intervals along the circumferential direction in the vicinity of the extended edge. Hub bolts 14 are provided. In this case, the disc wheel can be positioned and fixed to the hub flange 12a by inserting a plurality of hub bolts 14 into bolt holes (not shown) formed in the disc wheel and tightening with hub nuts (not shown). At this time, positioning in the radial direction of the wheel is performed by a pilot portion 12d protruding from the wheel side of the hub 12.

  Further, an annular rotating wheel constituting body 16 (another inner ring constituting the rotating wheel 4 together with the hub 12) is fixed to the inner ring 4 (hub 12) on the vehicle body side. In this case, as an example of a fixing method of the rotating wheel component 16, the rotating wheel component 16 is mounted in a state where a plurality of rolling elements 6 and 8 are held by the cage 18 between the stationary wheel 2 and the rotating wheel 4. The step 12b formed on the hub 12 is fitted. Next, for example, a fixing spacer 20 is set on the peripheral end portion 16 s of the rotating wheel constituting body 16, and then a nut 22 is screwed onto a hub shaft 12 c integrally formed on the vehicle body side of the hub 12. Then, the fixing spacer 20 is tightened in the direction of the peripheral end portion 16 s of the rotating wheel component 16 with the nut 22. As a result, the rotating wheel component 16 can be fixed to the rotating wheel 4 while being sandwiched between the fixing spacer 20 and the hub 12.

  At this time, a predetermined preload is applied to the bearing, and in this state, the rolling elements 6 and 8 form a predetermined contact angle with each other and the raceway grooves 2s and 4s of the stationary wheel 2 and the rotating wheel 4 respectively. Each is incorporated in a rotatable manner. In this case, an action line (not shown) connecting the two contact points is orthogonal to each raceway groove 2s, 4s and passes through the center of each rolling element 6, 8 to one point (action point) on the bearing center line. Intersect. This constitutes a rear combination (DB) bearing.

  By the way, in the configuration as described above, all the forces acting on the wheels during traveling of the vehicle are transmitted from the disc wheel to the suspension device through the bearing (hub 12), and various loads are applied to the bearing (hub 12). (Radial load, axial (axial direction) load, moment load, etc.) are applied. In this case, in order to ensure the running stability of the automobile, various loads applied to the bearing are measured by a load measuring device.

  Here, as the load measuring device, for example, various devices including those disclosed in Patent Document 1 are known. As an example, the load measuring device shown in FIGS. 1 (a) and 1 (b) is used. Measures the load applied to the bearing (hub 12) based on the relative displacement between the stationary wheel 2 and the rotating wheel 4. More specifically, the load measuring device has a hollow cylindrical shape having a detection surface 24s that is concentrically fixed to the outer periphery of the hub 12 (the rotating wheel 4) and whose characteristics are changed at predetermined intervals along the circumferential direction. The encoder 24, a detector 26 that is fixed to the stationary wheel 2 so as to face the surface 24s to be detected and detects a change in the characteristics of the surface 24s to be detected, and a predetermined calculation process on the detection signal output from the detector 26 And a calculator (not shown) for calculating a load applied to the bearing (hub 12).

  In the encoder 24, a plurality of through holes (encoded information) 24a and 24b having a slit shape (for example, an elliptical shape) are formed on the detected surface 24s at equal intervals along the circumferential direction and in two rows in the axial direction. Is formed. In this case, the through-holes 24a and 24b in each row are set to have the same inclination angle and the inclination directions are opposite to each other. Note that the sizes and shapes of the through holes 24a and 24b are arbitrarily set according to the size and shape of the encoder 24, for example, and are not particularly limited here. Further, instead of the through holes 24a and 24b, for example, concave groove-shaped encoded information formed by recessing the detected surface 24s may be formed on the detected surface 24s of the encoder 24. Further, as the material of the encoder 24, for example, a magnetic or non-magnetic metal material or a resin material can be arbitrarily applied depending on the type of sensor to be detected, the purpose of use of the bearing, and the usage environment. There is no particular limitation.

  On the other hand, the detector 26 is provided with two rotational speed sensors Sa and Sb facing the respective through holes 24a and 24b in two rows in the axial direction along the axial direction. In this case, each of the rotational speed sensors Sa and Sb passes through the plurality of through holes 24a and 24b immediately before the rotational speed sensors Sa and Sb in a state where the encoder 24 is rotated with the rotation of the bearing (hub 12). Output detection signal (A phase signal, B phase signal: Fig. 2 (a)) corresponding to the change in the characteristics of the detected surface 24s (the change in the shape of the detected surface 24s depending on the presence or absence of the through holes 24a, 24b) To do.

  It should be noted that the rotational speed sensors Sa and Sb do not necessarily have to have the same detection signal phase in the initial state where no load is applied to the bearing (hub 12). In the drawing, the configuration example in which the rotational speed sensors Sa and Sb are arranged in a line along the axial direction is shown, but the configuration is not particularly limited to the configuration in which the rotational speed sensors Sa and Sb are aligned in the axial direction.

  Moreover, as each rotational speed sensor Sa and Sb, a commercially available optical sensor, magnetic sensor, or the like can be applied. In this case, for example, in the case of an optical sensor, a change in optical characteristics (for example, light quantity, wavelength, frequency, etc.) of reflected light from the detected surface 24s accompanying a change in the characteristics of the detected surface 24s is detected. A detection signal is output. On the other hand, in the case of a magnetic sensor, for example, a change in magnetic characteristics (for example, magnetic flux density, magnetic field, etc.) of the detected surface 24s accompanying a change in the characteristics of the detected surface 24s is detected, and a detection signal is output.

Here, a method for measuring the relative displacement amount between the stationary wheel 2 and the rotating wheel 4 in the load measuring apparatus as described above will be described.
In an initial state in which no load is applied to the bearing (hub 12), the phase difference (x or y in FIG. 2) of the detection signals of the rotational speed sensors Sa and Sb is a certain constant value. When the change is equally distributed in the circumferential direction) When the axial (axial) load is applied to the bearing (hub 12), the stationary wheel 2 and the rotating wheel 4 are relatively displaced in the axial direction, A change occurs in the phase difference (x or y in FIG. 2) of the detection signals (A-phase signal and B-phase signal) output from the rotational speed sensors Sa and Sb.

  At this time, the calculator (not shown) calculates the phase difference ratio of the detection signals (A phase signal and B phase signal) output from each of the rotational speed sensors Sa and Sb, and obtains the phase difference ratio as the calculation result. Based on this, the load applied to the bearing (hub 12) is calculated. FIG. 2A schematically shows pulse waveforms of the A-phase signal and the B-phase signal. The phase difference (time x1) from the fall of the A phase signal to the fall of the B phase signal and the phase difference (time y1) from the fall of the B phase signal to the fall of the A phase signal are measured, and P = x1 / (x1 + y1) is calculated, and the phase difference ratio based on the A phase signal is obtained. Here, x1 + y1 indicates the period of the A phase signal.

  However, the rotation of the wheel during traveling of the vehicle is not always constant, and acceleration and deceleration are repeated, and the rotation state of the bearing (hub 12) also changes accordingly. A technique for calculating an accurate phase difference ratio is required. The phase difference ratio P described above shows a constant value when the rotation speed of the rotating shaft (rotating wheel) is constant, but the speed is not constant even during one cycle of the A phase during acceleration / deceleration. Even if the load applied to the bearing is constant, the phase difference ratio P changes. As an example, when the phase difference ratio P = 0.500 (when the load is constant), the change in the phase difference ratio when the acceleration is 100 rpm / s (12.5 km / h / s) is calculated as shown in FIG. b). As shown in FIG. 2B, it can be seen that a change (error) occurs in the phase difference ratio when the rotational speed is about 400 rpm or less.

Therefore, a technology that can accurately and accurately measure the load applied to the bearing in the axial direction by calculating the phase difference ratio with high accuracy and accuracy regardless of the rotation state of the bearing (hub 12). However, such technology is not currently known.
JP 2006-226937 A

  The present invention has been made to meet such demands, and its purpose is to apply a load applied to the bearing by a calculation method capable of obtaining an accurate phase difference ratio even when the rotational speed of the bearing varies during acceleration and deceleration. It is an object of the present invention to provide a load measuring device capable of measuring the accuracy with high accuracy.

  In order to achieve such an object, the present invention provides a load measuring device for a bearing including a rotating wheel disposed so as to be relatively rotatable with respect to a stationary wheel. An encoder having a detected surface that is fixed concentrically and whose characteristics are changed at predetermined intervals along the circumferential direction, and is fixed to a stationary wheel facing the detected surface and changes in characteristics of the detected surface. A detector for detection, and a calculator for calculating a load applied to the bearing by performing a predetermined calculation process on the detection signal output from the detector.

  In this case, the detector is provided with a plurality of rotational speed sensors facing the detected surface of the encoder along the axial direction, and each rotational speed sensor is in a state where the encoder is rotated as the bearing rotates. , A detection signal corresponding to the change in the characteristics of the surface to be detected is output. In addition, the computing unit measures the phase difference between the detection signals output from the respective rotation speed sensors as time, calculates a plurality of phase difference ratios at different elapsed times based on the measurement result, and calculates the plurality of levels. The load applied to the bearing is calculated by taking the average of the phase difference ratio.

  In the present invention, as the first stage, the phase difference from the fall of the A phase signal to the fall of the B phase signal (time x1) and the phase difference from the fall of the B phase signal to the fall of the A phase signal ( Time y1) is measured, P = x1 / (x1 + y1) is calculated, and the phase difference ratio P is obtained. Next, as the second stage, the phase difference (time x2) from the fall of the next A-phase signal to the fall of the B-phase signal is measured, Q = x2 / (y1 + x2) is calculated, and the phase difference ratio Q Ask for. As a third stage, a phase difference ratio R = (P + Q) / 2 is obtained, and the load applied to the bearing is calculated using this R as a phase difference ratio.

  Further, in the present invention, in the initial state where the load is not applied to the bearings, the phases of the detection signals do not necessarily have to coincide with each other. In the encoder, a plurality of pieces of encoded information having a predetermined shape are formed on the detection surface in a plurality of rows in the axial direction at equal intervals along the circumferential direction. Also, the bearing of the present invention is configured to rotatably support the wheels of various vehicles with respect to the vehicle body, the stationary wheel is fixed to the vehicle body side and is always kept in a non-rotating state, It is connected to the wheel side and rotates with the wheel.

  According to the load measuring apparatus of the present invention, the load applied to the bearing can be measured with high accuracy and accuracy by a calculation method capable of obtaining an accurate phase difference ratio even when the rotational speed of the bearing varies during acceleration and deceleration. it can.

  Hereinafter, a bearing load measuring device according to an embodiment of the present invention will be described with reference to the accompanying drawings. Since the present embodiment is an improvement of the arithmetic processing in the arithmetic unit of the above-described bearing load measuring device (FIGS. 1A and 1B), only the improved portion will be described below. In this case, the bearing applied to the present embodiment is the same as the bearing shown in FIG.

  As shown in FIGS. 3 (a) and 3 (b), in the load measuring apparatus of the present embodiment, detection signals (not shown) output from the rotational speed sensors Sa and Sb of the detector 26 (not shown) A phase signal, B phase signal) Measure the phase difference time (x1, y1, x2, y2, x3, y3, x4 ...), and based on the measurement results, a plurality of phase difference ratios at different elapsed times Is calculated, and the average of these plural phase difference ratios is calculated to calculate the load applied to the bearing.

Here, the operation | movement which calculates the load added to a bearing is demonstrated concretely.
In this case, the axial (axial direction) load is applied to the bearing (hub 12) during the rotation of the bearing, and as shown in FIG. 3B, the detection signals (A It is assumed that a phase difference has occurred in the phase signal and the B phase signal. FIG. 2B schematically shows pulse waveforms of the A phase signal and the B phase signal.

  In the present embodiment, the computing unit calculates a plurality of phase difference ratios of the detection signals (A-phase signal and B-phase signal) output from the rotational speed sensors Sa and Sb at different elapsed times. Further, in this calculation process, as an example, the elapsed time is counted with reference to the falling edge of the pulse of one detection signal (for example, the A-phase signal). As a method for counting the elapsed time, for example, an existing period measurement function of a CPU incorporated in an arithmetic unit or a microcomputer may be used, or a time elapsed counter may be additionally provided.

  At this time, the computing unit, as the first stage, has a phase difference (time x1) from the fall of the A phase signal to the fall of the B phase signal, and the level from the fall of the B phase signal to the fall of the A phase signal. The phase difference (time y1) is measured, P = x1 / (x1 + y1) is calculated, and the phase difference ratio P is obtained.

  Subsequently, as the second stage, the phase difference (time x2) from the fall of the next A-phase signal to the fall of the B-phase signal is measured, Q = x2 / (y1 + x2) is calculated, and the phase difference ratio Q Ask for.

As a third stage, a phase difference ratio R = (P + Q) / 2 is obtained, and the load applied to the bearing is calculated using this R as a phase difference ratio. In this case, for example, in a state in which acceleration and deceleration are repeated while the vehicle is running and the rotational acceleration of the bearing (hub 12) is changed accordingly, the two phase difference ratios P and Q are different from each other with respect to the change in acceleration. Since the contradictory characteristics are shown, the influence of the rotational acceleration of the bearing (hub 12) can be reduced by taking the average R.
In the above description, the phase difference (time) has been described as falling from the fall of the A phase and the B phase.

  Here, as an example, when the phase difference ratio P = 0.500, changes in the phase difference ratios P, Q, and R at a rotational acceleration of 100 rpm / s (12.5 km / h / s) are considered. ), It can be seen that the error due to the acceleration of the two phase difference ratios P and Q is opposite and symmetrical when the rotational speed is about 400 rpm or less. On the other hand, the phase difference ratio R obtained by averaging the two phase difference ratios P and Q cancels the error due to the acceleration of the two phase difference ratios P and Q. As a result, the rotational speed is about 400 rpm or less. It can be seen that the error in the phase difference ratio has been eliminated.

  As a result, the phase difference ratio can be calculated with high accuracy and accuracy not only in a state where the rotational speed of the bearing (hub 12) is constant but also in a state where the rotational acceleration changes. As a result, the load applied to the bearing can be measured with high accuracy and accuracy regardless of the rotation state of the bearing.

  In the above-described embodiment, the influence of the rotational acceleration is canceled based on the phase difference ratio R = (P + Q) / 2 that is adjacent (continuous) to each other. It is not necessary to take the phase difference ratio. In this case, two phase difference ratios P and Q exhibiting characteristics that are symmetrically opposite to each other are calculated, and an average of these may be taken.

  For example, in the pulse waveforms of the A-phase signal and the B-phase signal in FIG. 3B, the adjacent times (continuous) times x1 and x2 and the separated times y3 and x4 are counted, and based on the count result , P = x1 / (x1 + y1), Q = x4 / (y3 + x4), respectively. Then, the average R of the two phase difference ratios P and Q is taken as R = (P + Q) / 2, and the load applied to the bearing is measured using the average R as the phase difference ratio.

(a) is sectional drawing of the bearing in which the load measuring device was integrated, (b) is a perspective view of the encoder of a load measuring device. (a) is a figure which shows typically the pulse waveform of the detection signal of the detector used for the conventional load measuring method, (b) is a figure which shows the phase difference ratio of a detection signal. (a) is a figure which shows the phase difference ratio calculated with the load measuring apparatus which concerns on one embodiment of this invention, (b) is the detection signal of the detector used for the load measuring method of this embodiment. The figure which shows a pulse waveform typically.

Explanation of symbols

x1, y1, x2, y2, x3, y3, x4 ... Phase difference time P, Q Phase difference ratio R Average of phase difference ratios P, Q

Claims (5)

A load measuring device for a bearing provided with a rotating wheel disposed so as to be relatively rotatable with respect to a stationary wheel,
The load measuring device is fixed concentrically to the rotating wheel and has an encoder having a detected surface whose characteristics are changed at predetermined intervals along the circumferential direction, and is fixed to the stationary wheel so as to face the detected surface. A detector that detects a change in the characteristics of the detected surface; and a calculator that calculates a load applied to the bearing by performing a predetermined calculation process on the detection signal output from the detector;
The detector is provided with a plurality of rotational speed sensors facing the detection surface of the encoder along the axial direction. Each rotational speed sensor is in a state where the encoder is rotated in accordance with the rotation of the bearing. Output detection signals corresponding to changes in the characteristics of the detection surface,
The computing unit measures the time of the phase difference between the detection signals output from each rotational speed sensor, calculates the multiple phase difference ratios at different elapsed times based on the measurement result, and calculates the load applied to the bearing A bearing load measuring device characterized by that. Time x1 (phase difference) from the change (falling or rising) of one detection signal to the change (falling or rising) of the other detection signal in the output signals A phase and B phase of the two rotational speed sensors, The phase difference ratio P = x1 / (x1 + y1) is calculated with the time from this change point to the next change (falling or rising) of one detection signal as y1 (phase difference) to obtain the phase difference ratio P. ,
The time x2 (phase difference) from the change (falling or rising) of the next one detection signal to the change (falling or rising) of the other signal is measured, and Q = x2 / (y1 + x2) is calculated. Find the phase difference ratio Q,
2. The bearing load measuring apparatus according to claim 1, wherein a phase difference ratio R = (P + Q) / 2 is obtained, and the phase difference ratio for obtaining R is used.   In the calculation of the phase difference ratio Q, a distant pulse is used instead of an adjacent pulse, and the time y3 (position) of the change (falling or rising) of one detection signal from the change (falling or rising) of the other detection signal is used. Phase difference), a time x4 (phase difference) from a change (falling or rising) of one detection signal to a change (falling or rising) of the other detection signal is measured, and Q = x4 / (y3 + x4) is measured. The bearing load measuring device according to claim 2, wherein the phase difference ratio Q is obtained by calculation.   The encoder is characterized in that a plurality of pieces of encoded information having a predetermined shape are formed on the detected surface at regular intervals along the circumferential direction and in a plurality of rows in the axial direction. Item 4. The bearing load measuring device according to any one of Items 1 to 3.   The bearing is configured to rotatably support the wheels of various vehicles with respect to the vehicle body, the stationary wheel is fixed to the vehicle body side and is always kept non-rotating, and the rotating wheel is connected to the wheel side. The bearing load measuring device according to claim 1, wherein the bearing load measuring device rotates with the wheel.

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