JP4779544B2 - Air pressure abnormality judgment device - Google Patents

Description

  The air pressure abnormality judging device according to the present invention detects a dangerous situation such as a burst of tires, such as detecting and informing the driver when the air pressure of the tire constituting the wheel of the automobile is abnormally lowered. Use to prevent.

  It is required to detect the tire air pressure when the automobile is running in order to prevent the tire from bursting due to running at an excessively low air pressure. For this reason, conventionally, a method of knowing a decrease in the air pressure of a specific tire from the difference in the rotational speed of each wheel accompanying the change in the effective radius of the tire (the distance from the center of rotation of the wheel to the road surface) due to air pressure (indirect method described later) Or a method of indirectly detecting the tire air pressure by detecting a change in the torsional characteristics of the tire when the lateral G is added. Further, as shown in Patent Documents 1 and 2, for example, a pressure sensor that measures the air pressure of the tire and a transmitter that transmits the detection value of the pressure sensor as a radio wave signal are incorporated in the wheel that forms the wheel together with the tire. A method of directly detecting the tire air pressure by sending the radio signal from the transmitter to a receiver provided on the vehicle body side has been considered. Furthermore, as described in Patent Document 3, it is considered that the air pressure in the tire constituting the wheel is obtained from the rotational speed and vibration frequency of the wheel. In the case of these conventional techniques described in Patent Documents 1 to 3, since a dedicated sensor is provided for determining the air pressure, the manufacturing cost of the determination device for determining the presence or absence of abnormal air pressure increases.

  On the other hand, Patent Document 4 describes a rolling bearing unit with a load measuring device as a device for obtaining information for performing control for ensuring driving stability of an automobile with higher accuracy. FIG. 2 shows an example of a rolling bearing unit with a load measuring device described in Patent Document 4. In the case of this conventional structure, a sensor unit 4 is inserted into a mounting hole 3 formed in a portion between the double-row angular outer ring raceways 2 and 2 at an intermediate portion in the axial direction of the outer ring 1 that is a stationary side race ring. The tip 5 of the unit 4 is protruded from the inner peripheral surface of the outer ring 1. The tip portion 5 is provided with a pair of revolution speed detection sensors 6 a and 6 b and a single rotation speed detection sensor 7.

  And the detection part of each revolution speed detection sensor 6a, 6b of these is provided in each holder 9a, 9b holding each rolling element 8a, 8b arranged in a double row freely, and detecting revolution speed The revolving speed of each of the rolling elements 8a and 8b can be detected by being close to and opposed to the side surface in the axial direction that is the detection surface of the encoders 10a and 10b. Further, the detection portion of the rotation speed detection sensor 7 is made to face the outer peripheral surface which is the detection surface of the rotation speed detection encoder 12 which is externally fitted and fixed to the intermediate portion of the hub 11 which is the rotation side raceway ring, The rotational speed of the hub 11 can be detected. According to the rolling bearing unit with a load measuring device having such a configuration, the load (radial load and axial load) applied between the outer ring 1 and the hub 11 is applied regardless of fluctuations in the rotational speed of the hub 11. Desired.

That is, in the case of the rolling bearing unit with a load measuring device as described above, an arithmetic unit (not shown) is arranged between the outer ring 1 and the hub 11 based on the detection signals sent from the sensors 6a, 6b, and 7. One or both of the applied radial load and axial load are calculated. For example, when the radial load is obtained, the computing unit obtains the sum of the revolution speeds of the rolling elements 8a and 8b in the rows detected by the revolution speed detection sensors 6a and 6b, and the sum and the rotation speed. The radial load is calculated based on a ratio with the rotational speed of the hub 11 detected by the speed detection sensor 7. The axial load is obtained by calculating a difference between the revolution speeds of the rolling elements 8a and 8b in each row detected by the revolution speed detection sensors 6a and 6b, and the difference between the difference and the rotational speed detection sensor 7 is detected. It calculates based on ratio with the rotational speed of the said hub 11 to do. Or the said axial load is calculated | required also by ratio of the revolution speed of the rolling elements 8a and 8b of each said row | line | column. This point will be described with reference to FIG. In the following description, the contact angles α _a and α _b of the rolling elements 8a and 8b in each row in the state where the axial load Fy is not applied are the same.

FIG. 3 schematically shows the rolling bearing unit for supporting the wheel shown in FIG. 2 and shows the action state of the load. Preloads F ₀ and F ₀ are applied to the rolling elements 8 a and 8 b arranged in a double row between the double row angular type inner ring raceways 13 and 13 and the double row angular type outer ring raceways 2 and 2. Further, a radial load Fz is applied to the rolling bearing unit during use due to the mass of the vehicle body or the like. Further, an axial load Fy is applied due to centrifugal force applied during turning. These preloads F ₀ , F ₀ , radial load Fz, and axial load Fy all affect the contact angles α (α _a , α _b ) of the rolling elements 8a, 8b. Then, the contact angle alpha _a, the alpha _b is changed, respective rolling elements 8a, the revolution speed n _c and 8b changes. The diameter of the pitch circle of each of the rolling elements 8a, 8b is D, the diameter of each of the rolling elements 8a, 8b is d, the rotational speed of the hub 11 provided with the inner ring raceways 13, 13 is n _i , When the rotational speed of the outer race 1 provided with the outer ring raceway 2,2 to 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 8a, the revolution speed n _c and 8b, these rolling elements 8a, the contact angle α (α _a, α _b) of 8b varies in response to changes in As described above, the contact angles α _a and α _b change according to the radial load Fz and the axial load Fy. Thus the revolution speed n _c is changed according to these radial load Fz and the axial load Fy. In the case of the structure shown in FIGS. 2 to 3, since the hub 11 rotates and the outer ring 1 does not rotate, specifically, as the radial load Fz increases as shown in FIG. The speed nc _decreases . Further, with respect to the axial load Fy, as shown in FIG. 5, the revolution speed of the row that supports the axial load Fy increases, and the revolution speed of the row that does not support the axial load Fy decreases. Therefore, on the basis of the revolution speed n _c, it will be asked to the radial load Fz and the axial load Fy.

In FIG. 4, the solid line A relates to the rolling elements 8b and 8b on the side where the radial load Fz is supported, and the broken line B similarly relates to the rolling elements 8a and 8a on the side where the radial load Fz is supported. The relationship between each revolution speed (and the ratio of the rotation speed of the hub 11) and the radial load Fz is shown. In FIG. 5, the broken line C indicates the relationship between the axial load Fy and the revolution speed of the rolling elements 8a and 8a in the row that supports the axial load Fy, and the solid line D indicates the axial load Fy and the axial load. The relationship with the revolution speed of the rolling elements 8b and 8b of the row | line | column which does not support Fy is shown, respectively. As is apparent from such Figures 2-5, the rolling elements 8a of each row, based on the revolution speed n _c of 8b, asked to the radial load Fz and the axial load Fy.

  Although not disclosed, Japanese Patent Application No. 2004-279155 measures the magnitude of the load applied to the rolling bearing unit based on the phase difference between the output signals of a pair of sensors arranged in the direction of the load. The invention is disclosed. 6 to 12 show the structures of four examples of the prior invention disclosed in the above application. Among the structures according to the respective prior inventions, the structure of the first example shown in FIGS. 6 to 8 supports the wheel on the inner diameter side of the outer ring 1 that is a stationary race ring that does not rotate while being supported by the suspension device. A hub 11 that is a rotating side race ring to be fixed (coupled and fixed) is rotatably supported via a plurality of rolling elements 8 and 8. An encoder 14 is externally fitted and fixed to an intermediate portion of the hub 11, and a pair of sensors 15 are provided between the rolling elements 8 and 8 arranged in a double row at the axial intermediate portion of the outer ring 1. 15 is provided in a state in which each detection unit is close to and opposed to the outer peripheral surface of the encoder 14 which is a detection surface. Note that a magnetic sensing element such as a Hall IC, a Hall element, an MR element, or a GMR element is incorporated in the detection portion of the sensor 15.

  In the case of the structure of the first example of the prior invention shown in FIGS. 6 to 8, the encoder 14 is made of a permanent magnet. On the outer peripheral surface of the encoder 14, which is a detected surface, portions magnetized in the N pole and portions magnetized in the S pole are arranged alternately at equal intervals in the circumferential direction. The boundary between the portion magnetized in the N pole and the portion magnetized in the S pole is inclined by the same angle with respect to the axial direction of the encoder 14, and the inclination direction with respect to the axial direction of the encoder 14 is changed. The axial directions are opposite to each other at the intermediate portion. Therefore, the portion magnetized in the N pole and the portion magnetized in the S pole have a “<” shape with the axially middle portion protruding (or recessed) most in the circumferential direction.

  Further, the position where the detection parts of both the sensors 15 and 15 are opposed to the outer peripheral surface of the encoder 14 is the same position in the circumferential direction of the encoder 14. In other words, the detection parts of both the sensors 15, 15 are arranged on the same virtual plane including the central axis of the outer ring 1. Further, in the state where no axial load is applied between the outer ring 1 and the hub 11, the axial direction intermediate portion between the portion magnetized in the N pole and the portion magnetized in the S pole is related to the circumferential direction. The installation position of each member 14, 15, 15 is regulated so that the most protruding part (the part where the inclination direction of the boundary changes) is exactly at the center position between the detection parts of the sensors 15, 15. is doing. In the case of the first example of the present invention, since the encoder 14 is made of a permanent magnet, it is not necessary to incorporate a permanent magnet on both the sensors 15 and 15 side.

  In the case of the first example of the prior invention configured as described above, when an axial load is applied between the outer ring 1 and the hub 11, the phase in which the output signals of the sensors 15, 15 change is shifted. That is, in the neutral state in which an axial load is not acting between the outer ring 1 and the hub 11 and the outer ring 1 and the hub 11 are not relatively displaced, the detection parts of the sensors 15 and 15 are It is opposed to the solid lines a and b in FIG. 8A, that is, the portion that is shifted from the most protruding portion by the same amount in the axial direction. Therefore, the phases of the output signals of the sensors 15 and 15 coincide as shown in FIG.

  On the other hand, when a downward axial load acts on the hub 11 to which the encoder 14 is fixed in FIG. 8A (the outer ring 1 and the hub 11 are relatively displaced in the axial direction), The detectors of both the sensors 15 and 15 are opposed to the portions indicated by broken lines B and B in FIG. 8A, that is, portions having different axial displacements from the most protruding portion. In this state, the phases of the output signals of the sensors 15 and 15 are shifted as shown in FIG. Further, when an upward axial load is applied to the hub 11 to which the encoder 14 is fixed as shown in FIG. 8A, the detecting portions of both the sensors 15 and 15 are connected to the chain line hub of FIG. , C, that is, the deviation in the axial direction from the most projecting portion opposes different portions in the opposite direction. In this state, the phases of the output signals of the sensors 15 and 15 are shifted as shown in FIG.

  As described above, in the case of the first example of the present invention, the phases of the output signals of the two sensors 15 and 15 are shifted in a direction corresponding to the acting direction of the axial load applied between the outer ring 1 and the hub 11. . In addition, the degree of displacement (displacement amount) of the output signals of the sensors 15 and 15 due to the axial load increases as the axial load increases. Therefore, in the case of the first example, the presence or absence of a phase shift of the output signals of both the sensors 15 and 15 and, if there is a shift, between the outer ring 1 and the hub 11 based on the direction and magnitude. The direction and magnitude of the acting axial load can be determined.

  In the case of the first example of the above-described prior invention, the permanent magnet encoder 14 is used. However, the Japanese Patent Application No. 2004-279155 includes an encoder 14a made of a magnetic material as shown in FIG. It also describes the structure used. Slit-like through holes 16a and 16b and column portions 30a and 30b are alternately arranged at equal intervals in the circumferential direction on the outer peripheral surface of the encoder 14a, which is the detection surface. The through holes 16a and 16b and the pillars 30a and 30b are inclined by the same angle with respect to the axial direction of the encoder 14a, and the inclined direction with respect to the axial direction is bounded by the axial intermediate portion of the encoder 14a. Are in opposite directions. That is, the encoder 14a has through holes 16a and 16a inclined in the same direction in the predetermined direction with respect to the axial direction in one half of the axial direction, and in a direction opposite to the predetermined direction in the other half of the axial direction. Through holes 16b, 16b inclined by the same angle are formed.

  The encoder 14a incorporated in the structure of the second example of the prior invention as described above is externally fitted and fixed to the hub 11 in the same manner as the first example shown in FIG. 6, and is intermediate in the axial direction of the outer ring 1 (see FIG. 6). The detection part of a pair of sensors installed in the part is brought close to and opposed to the outer peripheral surface of the encoder 14a. In the case of the second example of the present invention, since the encoder 14a is simply made of a magnetic material, a permanent magnet is incorporated on the side of the pair of sensors. In the case of the second example of such a prior invention, the action direction and magnitude of the axial load acting between the outer ring 1 and the hub 11 are the same as in the case of the first example of the aforementioned invention. You are asked for it.

  In the encoder 14a shown in FIG. 9 described above, the through holes 16a and 16b that are independent from each other are arranged in a “C” shape. However, as in the third example shown in FIG. It is also possible to use an encoder 14b in which character-shaped through holes 16c and 16c are arranged at equal intervals in the circumferential direction. In the case of the structure shown in FIG. 10, a pair of magnetic detection elements 17, 17 and a single permanent magnet 18 are embedded and supported in the tip of a single holder 19. An integrated sensor unit is configured. The function for obtaining the axial load acting between the outer ring 1 and the hub 11 is the same as in the first example described above or the second example described above.

  FIGS. 11 to 12 show a structure for obtaining the displacement in the axial direction applied between the outer ring 1a and the hub 11a by a single sensor as a fourth example of the prior invention. In the case of this example, since it is intended for a wheel bearing rolling bearing unit for supporting a driving wheel of a heavy automobile, tapered rollers are used as the rolling elements 8c and 8c. In addition, a spline hole 20 is formed in the central portion of the hub 11a, which is the rotating side raceway, for inserting a spline shaft attached to the constant velocity joint. An annular encoder 14c made of a magnetic metal material is externally fitted and fixed to an intermediate portion of the hub 11a. On the outer peripheral surface of the encoder 14c, the concave portions 21 and 21 and the convex portions 22 and 22 are alternately arranged in the circumferential direction. The width dimension in the circumferential direction of each of the concave portions 21 and 21 and the convex portions 22 and 22 gradually changes in the axial direction.

  On the other hand, a magnetic detection type sensor 15a is inserted into a mounting hole 3a formed in the intermediate portion of the outer ring 1a, which is a stationary side race, and the detection portion provided at the tip of the sensor 15a is a detected surface. The encoder 14c is placed close to and opposed to the outer peripheral surface. The detection signal of the sensor 15a changes as the concave portions 21 and 21 and the convex portions 22 and 22 pass alternately in the vicinity of the detection portion. And after making it a rectangular wave by the attached waveform shaping circuit, it sends out to the calculator which is not shown in figure. Thus, the change pattern of the detection signal of the sensor 15a sent from the waveform shaping circuit to the computing unit (duty ratio of detection signal = high potential duration / one cycle) is the encoder that the detection unit faces. It changes with the axial direction position of the outer peripheral surface of 14c. Therefore, an axial load acting between the outer ring 1a and the hub 11a is obtained based on the change pattern. Note that the encoder used for realizing the structure for obtaining this axial load based on the duty ratio of the detection signal is also a permanent magnet instead of the magnetic material as shown in FIG. I can do it. In this case, S poles and N poles are alternately arranged on the outer peripheral surface of the encoder made of permanent magnets, and the width dimensions of these S poles and N poles in the circumferential direction are gradually changed in the axial direction.

The configuration and operation of the rolling bearing unit with a load measuring device described in Japanese Patent Application No. 2004-279155 are as described above, but as a device for measuring the load or moment applied to the rolling bearing unit, For example, there are those disclosed in Japanese Patent Application Nos. 2005-147642 and 2005-267552. In addition, since the moment is also a force acting based on the axial load applied to the rolling bearing unit, the term “ axial load” described in the claims includes this moment. FIGS. 13 to 14 show two examples of other devices for measuring the axial load or moment applied to the rolling bearing unit.
First, in the case of the structure of the fifth example of the present invention shown in FIG. 13, an encoder 14d constituted by a permanent magnet in the middle of the hub 11b is provided via a support ring 23 having a crank-shaped cross section. The outer fitting is fixed. N poles and S poles are alternately arranged at equal intervals in the circumferential direction on the outer circumferential surface, which is the detected surface of the encoder 14d. Further, as shown in FIG. 13A, the shape of the boundary between the N pole and the S pole is inclined by the same angle in the same direction with respect to the axial direction of the encoder 14d (the width direction of the outer peripheral surface). I am letting. And the detection part of the sensor 15b supported by the axial direction intermediate part of the outer ring | wheel 1 is made to oppose to the outer peripheral surface of the said encoder 14d close to the radial direction.

  Further, an inner portion of a slinger 25 that is externally fitted and fixed to the inner end portion of the hub 11b, which forms a combined seal ring 24 that closes the inner end portion inner peripheral surface of the outer ring 1 and the inner end portion outer peripheral surface of the hub 11b. A ring-shaped second encoder 26 is fixedly attached to the side surface concentrically with the hub 11b. N poles and S poles are alternately arranged at equal intervals in the circumferential direction on the inner side surface that is the detected surface of the second encoder 26. Further, as shown in FIG. 13B, the boundary between the N pole and the S pole has a linear shape in the radial direction. The number of S poles and N poles present on the outer peripheral surface of the encoder 14d is equal to the number of S poles and N poles present on the inner side surface of the second encoder 26. And the detection part of the 2nd sensor 27 supported by some stationary members, such as a knuckle (not shown) which comprises a suspension apparatus, is made to oppose and adjoin to the inner surface of this 2nd encoder 26 in the axial direction. .

  In the case of the fifth example of the prior invention, an axial load does not act between the outer ring 1 and the hub 11b, and the outer ring 1 and the hub 11b are not displaced relative to each other in the axial direction. In this state, the detection signals of both the sensors 15b and 27 are changed simultaneously (or with a predetermined time difference). For this reason, in the neutral state, the detection unit of the second sensor 27 faces the boundary between the S pole and the N pole existing on the inner surface of the second encoder 26, and at the same time, the detection unit of the sensor 15b. The positions of the members 27, 26, 15b, and 14d are restricted so as to face the boundary between the south pole and the north pole existing on the outer peripheral surface of the encoder 14d.

  In the case of the fifth example of the prior invention configured as described above, when an axial load acts between the outer ring 1 and the hub 11b (the outer ring 1 and the hub 11b are relatively displaced in the axial direction), The phases of the output signals of both sensors 15b and 27 are shifted. That is, the phase of the detection signal of the second sensor 27 facing the inner surface of the second encoder 26 is constant (no advance or delay) regardless of the presence or absence of the relative displacement. On the other hand, the phase of the detection signal of the sensor 15b facing the outer peripheral surface of the encoder 14d advances or delays with the relative displacement. Therefore, the phases of the output signals of the sensors 15b and 27 are shifted by the amount of advance or delay.

  Thus, in the case of the fifth example of the present invention, the phases of the output signals of the sensors 15b and 27 are shifted in the direction corresponding to the direction of the axial load applied between the outer ring 1 and the hub 11b. . Further, the degree of displacement (displacement amount) of the output signals of the sensors 15b and 27 due to the axial load increases as the axial load increases. Therefore, in the case of the fifth example of the above-described prior invention, the outer ring 1 and the output of the outer ring 1 are determined based on the presence or absence of the phase shift of the output signals of the sensors 15b and 27, and the direction and magnitude of the shift, if any. The direction and magnitude of the axial relative displacement with the hub 11b, and thus the direction and magnitude of the axial load acting between the outer ring 1 and the hub 11b are obtained.

  Next, FIG. 14 shows a sixth example of the prior invention. In the case of the sixth example of the present invention, the support ring 28 is fitted and fixed concentrically with the hub 11 at the inner end portion of the hub 11 which is the rotating raceway. At the same time, a cylindrical encoder 14d having the same configuration as that used in the above-described fifth example of the invention is attached and fixed to the outer peripheral surface of the front end portion of the support ring 28. Further, the detection portions of the pair of sensors 15c and 15d are placed close to and opposed to the upper and lower ends of the outer peripheral surface which is the detection surface of the encoder 14d. That is, the sensors 15c and 15d are supported and fixed at both upper and lower ends of the inner peripheral surface of the cover 29 that is attached to the inner end opening of the outer ring 1 that is a stationary side race, and the detection of both the sensors 15c and 15d is performed. The portion is close to and opposed to the upper and lower end portions of the outer peripheral surface of the encoder 14d.

  In the case of a rolling bearing unit for supporting a wheel of an automobile, the axial load applied between the outer ring 1 and the hub 11 is input from the ground contact surface between the outer peripheral surface of the wheel (tire) coupled to the hub 11 and the road surface. The Since this ground contact surface exists radially outward from the center of rotation of the outer ring 1 and the hub 11, the axial load is not between the outer ring 1 and the hub 11 but as a pure axial load. 1 and the center of the hub 11 and the center of the ground plane are applied with a moment in a virtual plane (in the vertical direction). The magnitude of this moment is proportional to the magnitude of the axial load input from the ground contact surface as long as the wheels have the same radius of rotation. Therefore, if this moment is obtained, this axial load can be obtained. On the other hand, when a moment is applied to the hub 11, the upper end of the encoder 14d is displaced in any direction with respect to the axial direction, and the lower end is similarly displaced in the opposite direction. As a result, the phases of the detection signals of the two sensors 15c and 15d in which the respective detection units are brought close to and opposed to the upper and lower end portions of the outer peripheral surface of the encoder 14d are shifted in the opposite directions with respect to the neutral positions. Therefore, the direction and magnitude of the axial load can be obtained based on the direction and magnitude of the phase shift of the detection signals of both the sensors 15c and 15d.

In any case, the axial load obtained by the rolling bearing unit with a load measuring device is equivalent to the axial load generated on the contact surface (ground surface) between the wheel (tire) and the road surface. Therefore, if the control for stabilizing the running state of the vehicle is performed based on the obtained axial load , the feed forward control for preventing the posture of the vehicle from becoming unstable becomes possible. Advanced control to ensure running stability is possible. The encoder for obtaining the moment is not limited to a permanent magnet as shown in FIG. 14, but may be a magnetic material. When using an encoder made of magnetic material, a permanent magnet is incorporated on the sensor side.

A rolling bearing unit with a load measuring device as described above requires the axial load (including moment) applied to the rolling bearing unit from the contact portion (grounding surface) between the outer peripheral surface of the tire constituting the wheel and the ground. However, unlike the prior art described in Patent Documents 1 to 3 described above, no particular consideration is given to obtaining the air pressure in the tire. Patent Document 5 describes a technique for correcting the measured value of the load with the air pressure so that the load including the axial load can be accurately obtained regardless of the fluctuation of the air pressure. The correction air pressure used in this case is obtained by a pressure sensor provided for measuring the air pressure, for example, in the same manner as the prior art described in Patent Documents 1 to 3 above. Therefore, if a determination device for determining the presence or absence of air pressure abnormality is configured, the manufacturing cost of the determination device increases, which is the same as the prior art described in Patent Documents 1 to 3 above.

Japanese Patent Laid-Open No. 2003-6779 JP 2003-157485 A JP 2003-294560 A JP 2005-31063 A JP-A-2005-214744

  In view of the circumstances as described above, the present invention realizes a structure capable of determining the presence or absence of an abnormality in the air pressure without using a pressure sensor that measures the air pressure in the tire, and for determining the presence or absence of the abnormality. The invention was invented to reduce the manufacturing cost of the determination device.

Each of the air pressure abnormality determination devices of the present invention includes a wheel, a wheel support rolling bearing unit, a load measuring device, and a determination device.
Of these wheels, the tires are assembled around the wheels.
The wheel-supporting rolling bearing unit is for rotatably supporting the wheel with respect to the suspension device.
Further, the load measuring device includes an axial load applied to the wheel (an axial load applied to the ground contact surface, or a stationary bearing ring and a rotating bearing ring constituting the wheel support rolling bearing unit based on the axial load. (Moment applied between the two).
Furthermore, the determination device determines whether or not there is an abnormality in the tire air pressure based on a load signal that represents a measurement value of the axial load by the load measuring device.

In the case of the invention described in claim 1, the determination unit includes a steering angle signal indicating a steering angle given to the steering wheel by the steering wheel, and a load indicating a measurement value of the axial load by the load measuring device. The presence or absence of air pressure abnormality is determined by comparing the signal.
Further, in the case of the invention described in claim 2, the determination device outputs an output signal of a vehicle body behavior sensor for measuring a lateral behavior (force applied to the vehicle body) of the vehicle body such as a yaw rate sensor, an acceleration sensor, and the like. By comparing with the load signal, the presence or absence of air pressure abnormality is determined.
Further, in the case of the invention described in claim 3, the determination device determines the presence or absence of an abnormality in air pressure based on the waveform of the load signal.
Further, in the case of the invention described in claim 4, the judging device compares the tire stiffness value estimated based on the load signal with the tire stiffness value in the normal state recorded in the memory. To determine if there is an abnormal air pressure.
When the invention described in claim 4 is carried out, more specifically, as in the invention described in claim 5 , the amount of movement of the acting point of the axial load acting on the wheel bearing rolling bearing unit. Based on the above, the stiffness value of the tire is estimated.

Further, when implementing the present invention, preferably, as in the invention described in claim 6 , a rotational speed detecting device for determining the rotational speed of the wheel is provided. Then, the determiner determines the presence or absence of abnormal air pressure in consideration of the rotational speed of the wheel obtained by the rotational speed detection device.
In addition, the structure of the load measuring device used when implementing this invention is not specifically limited. However, since the object of the present invention is to reduce the manufacturing cost of the determination device for determining whether there is an abnormality in the air pressure in the tire, it is used for other purposes such as ensuring the running stability of the vehicle. It is preferable to use the signal of the load measuring device for this purpose. Considering this point, it is preferable to use the load measuring device incorporated in the wheel bearing rolling bearing unit as in the invention described in claim 7 .
As the load measuring device incorporated in the wheel bearing rolling bearing unit, the load is calculated based on the change in the revolution speed of the rolling element as described in FIGS. The load is calculated based on the phase difference between the detection signals of a pair of sensors as described in 10, 13, and 14, or the detection signal of one sensor as described in FIGS. Any device that obtains a load based on the duty ratio can be used.

Since the load measuring device is for determining the axial load applied to the wheel, when the air pressure in the tire constituting the wheel fluctuates (decreases), a load signal representing the measured value of the axial load by the load measuring device is obtained. The changing state changes. Therefore, by observing the change state of the load signal, it can be determined whether or not the air pressure is normal.
First, when the steering angle signal and the load signal are compared as in the invention described in claim 1 , the difference (time difference) between the timing at which the steering angle signal changes and the timing at which the load signal changes is large. Based on this, it can be determined whether or not the air pressure is normal.

That is, when the air pressure decreases, the lateral rigidity of the tires constituting the wheels decreases. For this reason, after the steering angle is given to the steered wheel in accordance with the operation of the steering wheel, the contact surface between the wheel (the front wheel that is the steered wheel and the rear wheel that is the non-steered wheel) and the road surface based on the centrifugal force ( The time delay until the axial load is generated on the ground contact surface increases as the air pressure decreases (responsiveness decreases). Further, the level (maximum value or average value) of the axial load generated on the ground contact surface also changes. That is, the level of the axial load increases as the rudder angle increases, but when the air pressure decreases and the amount of tire collapse increases, the moment applied to the wheel-supporting rolling bearing unit supporting the wheel is increased. And the measured value of the axial load also decreases.
Therefore, the steering angle signal that represents the steering wheel operation amount and the load signal that represents the axial load applied to the wheel support rolling bearing unit, the phase difference or level ratio existing between these two signals. In comparison, it is possible to determine whether or not the air pressure is abnormal. Note that the phase difference or level ratio existing between the two signals also varies depending on the running speed of the automobile. Therefore, the phase difference and level are compared in consideration of the traveling speed.

Further, as in the invention described in claim 2, when the signal representing the behavior of the vehicle body (vehicle behavior signal) and the load signal are compared, the presence or absence of the abnormality in the air pressure can be determined based on the same concept.
That is, when the tire air pressure decreases, the lateral rigidity of the wheel including the tire decreases and the rigidity of the undercarriage of the automobile changes (decreases). And the relationship (what is called the dynamic characteristic of a vehicle body) of the timing of the axial load generation | occurrence | production and the magnitude | size of the produced | generated axial load and the lateral behavior of a vehicle body regarding the contact surface regarding this wheel changes.
Therefore, it is possible to determine whether or not the tire air pressure is abnormal from a comparison between the vehicle body behavior signal output from the vehicle body behavior sensor such as a yaw rate sensor or an acceleration sensor and the load information. Also in this case, the relationship between the vehicle body behavior signal and the load information varies depending on the traveling speed of the automobile. Therefore, the comparison between the vehicle body behavior signal and the load information is performed in consideration of the traveling speed.

Further, as in the invention described in claim 3, it is also possible to determine the presence / absence of an abnormality in air pressure based on the waveform of the load signal representing the measured value of the axial load by the load measuring device. The reason for this is as follows.
That is, when the air pressure is abnormal (at the time of lowering), the rigidity of the tire constituting the wheel changes (decreases). For example, the unsprung portion (of the automobile component members, the road surface is more The resonance frequency of the portion present on the side changes, and the frequency characteristics of the waveform of the load signal change accordingly. Alternatively, the load input from the wheel side based on the unevenness of the road surface during traveling is transmitted to the wheel bearing rolling bearing unit through the tire with changed dynamic characteristics, so the waveform of the load signal is normal and abnormal The frequency characteristics change. Therefore, by observing this load signal, it is possible to determine whether or not there is an abnormality in the air pressure. Such a load signal is observed in a circuit for processing an output signal of a sensor constituting the load measuring device or a circuit for obtaining an axial load from the output signal.

As described above, in the case of the method of determining whether there is an abnormality in the air pressure based on the change in the resonance frequency of the unsprung portion or the change in the dynamic characteristics of the tire, this determination is not limited to the change in the load signal. This can also be done by directly measuring the vibration of the wheel bearing rolling bearing unit. In this case, a sensor (G sensor) for measuring this vibration is required, but a circuit for processing an output signal of the sensor constituting the load measuring device or an axial load is obtained from this output signal. Since only the G sensor is added to the circuit for this purpose, an air pressure abnormality determination device can be realized while suppressing an increase in cost.

Further, as in the inventions described in claims 4 and 5 , the tire stiffness value is estimated based on the amount of movement of the point of action of the axial load acting on the wheel bearing rolling bearing unit that can be estimated based on the load signal. Even if this stiffness value is compared with the stiffness value of the tire in a normal state recorded in the memory, it can be determined whether there is an abnormality in the air pressure.
That is, the stiffness value of the tire has a substantially linear relationship with the air pressure in the tire, and the tire stiffness also changes (decreases) when the air pressure is abnormal (at the time of decrease). Specifically, the tire deformation caused by the change in the axial load at the time of changing the course or running on the sloping ground (road surface inclined in the width direction) is larger than when the air pressure is normal (the amount of deformation is large). Become. When the deformation of this tire increases, the position of the load application point (the center point of the range in which the load is applied to the tire from the contact surface between the tire and the road surface) is greatly changed in the width direction of the tire from the state before the deformation. Moving. Since the positional relationship between the center of the wheel support rolling bearing unit and the load application point changes with respect to the width direction of the tire, the axial measurement is performed by a load measuring device incorporated in the wheel support rolling bearing unit. The relationship between the load and the moment will change significantly compared to when the air pressure is normal.

  The relationship between the axial load and the moment is uniquely determined based on the distance between the load application point and the center of the wheel-supporting rolling bearing unit (wheel turning radius), and this distance depends on the air pressure. Change. Therefore, the relationship between the axial load and the moment can be uniquely estimated according to the air pressure. For this reason, when the relationship between these axial loads and moments is significantly disturbed, it can be considered that the air pressure is abnormally lowered and the distance is remarkably shortened. Further, of the axial load and moment, the moment is obtained, for example, with the structure shown in FIG. Further, for example, in the structure shown in FIG. 10, the axial load and the moment are obtained from the information on the phase difference of the detection signals detected by the pair of magnetic detection elements 17 and 17 facing the outer peripheral surface of the lower end of the encoder 14b. And the ability to synthesize. Then, from the resultant force obtained with the structure shown in FIG. 10 and the moment obtained with the structure shown in FIG. 14 (by subtracting the moment from the resultant force), the value of the axial load alone can be obtained. Therefore, as shown in an example of the embodiment described below, if both of these structures are incorporated, both the axial load and the moment can be obtained, and further the relationship between them can be obtained. Further, by using the structure according to Japanese Patent Application No. 2005-267552, the axial load and the moment can be obtained simultaneously. The structure according to Japanese Patent Application No. 2005-267552 is such that, in addition to the structure shown in FIG. 10, a sensor facing the outer peripheral surface of the upper end of the encoder is provided. Based on the phase difference information of the sensor, the axial load and moment can be obtained. In any case, the relationship between the axial load and the moment in the state where the air pressure is normal, the relationship between the axial load and the moment is obtained and stored in the memory of the judgment device attached to the load calculator in advance. The air pressure abnormality can be determined. If the presence or absence of this air pressure abnormality is determined by such a method, it can be determined not only for each wheel independently but also without being affected by the traveling speed.

  FIG. 1 shows an example of an embodiment of the present invention. In the case of this example, a braking disk 33 and a wheel 34 are coupled and fixed to a flange portion 32 provided at an axially outer end portion of the hub 11c constituting the wheel supporting rolling bearing unit 31. The wheel 34 is formed by attaching a tire 36 to the outer peripheral edge of the wheel 35. Also, an encoder 14e made of a magnetic metal plate is fixed concentrically with the hub 11c at the inner end in the axial direction of the hub 11c. In the cylindrical portion 37 constituting the encoder 14e, "H" shaped through holes 16c, 16c are arranged at equal intervals in the circumferential direction as in the structure according to the prior invention shown in FIG. ing. The detectors of the three sensors are placed close to each other on the outer peripheral surface of the encoder 14e.

Of these, the detection portions of the two sensors are opposed to two axially spaced positions at the lower end of the outer peripheral surface of the encoder 14e. That is, these encoders 14e and the two sensors, similar to the structure according to the prior invention shown in FIG. 10 described above constitute a structure for measuring the axial load F _y. On the other hand, the detection part of the remaining one sensor is opposed to the upper end part of the outer peripheral surface of the encoder 14e. In the neutral state in which the central axis of the hub 11c and the central axis of the outer ring 1 coincide with each other while no moment is applied to the wheel bearing rolling bearing unit 31, the detection unit of the remaining one sensor with respect to the encoder 14e. And the facing position of one of the two sensors coincide with each other in the axial direction of the encoder 14e. That is, the remaining one sensor and one of the two sensors are the same as the structure according to the previous invention shown in FIG. 14 (from the permanent magnet to the magnetic material). A structure for measuring the moment M _x , as changed.

According to the structure of this example configured as described above, it is determined whether the air pressure in the tire 36 is abnormal based on the axial load F _y and the moment M _x obtained from the detection signals of the sensors. it can. That is, as described above, when the air pressure in the tire 36 is abnormal (at the time of lowering), the rigidity of the tire 36 is lowered, and when changing the course or traveling on the slope, as shown in FIG. Deforms greatly. When the deformation of the tire 36 becomes large in this way, the position of the load application point is from the state shown in FIG. 1B where the air pressure is normal and the tire 36 is not deformed. Move significantly (δ ₁ min in FIG. 1). Then, the positional relationship between the center of the wheel supporting rolling bearing unit 31 and the load application point changes in the width direction of the tire 36. For this reason, when the air pressure shown in FIG. 1B is normal, the relationship between the axial load F _y and the moment M _x measured by the load measuring device incorporated in the wheel bearing rolling bearing unit 31 is normal. On the other hand, it will change drastically.

The relationship between the axial load F _y and the moment M _x is uniquely determined based on the distance between the load application point and the center of the wheel bearing rolling bearing unit 31 (the rotation radius of the wheel 34). Changes according to the air pressure. That is, when the normal distance shown in FIG. 1B is R, the tire 36 is crushed by δ ₂ when the air pressure decreases, and this distance becomes R−δ ₂ . Therefore, the relationship between the axial load F _y and the moment M _x can be uniquely estimated according to the air pressure. For this reason, when the relationship between the axial load F _y and the moment M _x is significantly disturbed, it can be considered that the air pressure is abnormally lowered and the distance R−δ ₂ is remarkably shortened. Therefore, with the above-described structure, both the axial load F _y and the moment M _x are obtained, and further, the relationship between these is obtained, and the air pressure stored in the memory of the judgment device previously attached to the load calculator is calculated. By comparing the relationship between the axial load F _y and the moment M _x in a normal state, the abnormality in the air pressure can be determined.

The above description has been given for the case where it is determined for each wheel whether or not the tire air pressure is abnormal for all the wheels of the automobile. However, depending on a specific determination method, there is a possibility that the accuracy related to the abnormality determination is affected by whether the tire to be determined constitutes a front wheel or a rear wheel. For example, like the invention described in claim 1 described above, when comparing the steering angle signal and the load signal, although easy to accurately determine the abnormality of the air pressure of the front wheel tires, the tire of the rear wheel pneumatic The abnormality determination accuracy is lower than that of the front wheels.

Even in such a case, in order to ensure the accuracy of the rear wheel abnormality determination, the present invention and the so-called indirect method can be combined to determine whether there is an abnormality in the air pressure of all the wheels. As described above, the indirect method used in this case is to determine whether or not the tire air pressure of any wheel is abnormally decreased by comparing the rotational speeds of all wheels (particularly the rotational speed). This is a method of determining that the tire pressure of a wheel having a fast speed has decreased. In such an indirect determination, there is a problem that an abnormality cannot be determined if the air pressures of all the wheels have decreased simultaneously. On the other hand, if the method of the invention described in claim 1 can accurately determine whether or not the air pressure of the front wheels is abnormal, whether or not the air pressure of all the wheels is abnormal by combining with the indirect method. Whether or not can be accurately determined.

Sectional drawing which shows one example of embodiment of this invention. Sectional drawing which shows an example of the conventional rolling bearing unit with a load measuring apparatus. The schematic diagram for demonstrating the reason for which a load is calculated | required by this conventional structure. The diagram which shows the relationship between the revolution speed of the rolling element of each row | line | column, and radial load. The diagram which similarly shows the relationship between an axial load and revolution speed. Sectional drawing which shows the 1st example of the rolling bearing unit with a load measuring apparatus which concerns on a prior invention. The perspective view of the encoder built in this 1st example. The diagram for demonstrating the state from which the output signal of a pair of sensor changes based on an axial load. The perspective view of the encoder integrated in the 2nd example of the rolling bearing unit with a load measuring apparatus which concerns on a prior invention. Sectional drawing which shows the 3rd example of the rolling bearing unit with a load measuring device which concerns on a prior invention. Sectional drawing which shows the 4th example. The fragmentary perspective view of the encoder integrated in this 4th example. Sectional drawing which shows the 5th example of the rolling bearing unit with a load measuring device which concerns on a prior invention. Sectional drawing which shows the 6th example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a Outer ring 2 Outer ring raceway 3, 3a Mounting hole 4 Sensor unit 5 Tip 6a, 6b Revolution speed detection sensor 7 Rotational speed detection sensor 8, 8a, 8b, 8c Rolling elements 9a, 9b Retainer 10a, 10b Revolution Speed detection encoder 11, 11a, 11b, 11c Hub 12 Rotational speed detection encoder 13 Inner ring raceway 14, 14a, 14b, 14c, 14d, 14e Encoder 15, 15a, 15b, 15c, 15d Sensor 16a, 16b, 16c Through hole DESCRIPTION OF SYMBOLS 17 Magnetic detection element 18 Permanent magnet 19 Holder 20 Spline hole 21 Concave part 22 Convex part 23 Support ring 24 Combination seal ring 25 Slinger 26 Second encoder 27 Second sensor 28 Support ring 29 Cover 30a, 30b Pillar part 31 Rolling bearing for wheel support Unit 32 Flange 33 Disc 34 Wheel 35 Wheel 36 Tire 37 Cylindrical part

Claims (7)

A wheel formed by assembling tires around the wheel, a wheel bearing rolling bearing unit for rotatably supporting the wheel with respect to a suspension device, a load measuring device for determining an axial load applied to the wheel, and the load measurement A determination unit that determines whether there is an abnormality in the tire air pressure based on a load signal that represents a measurement value of an axial load by the device, and the determination unit represents a rudder angle that is given to a steered wheel by a steering wheel. An air pressure abnormality determining device that determines the presence or absence of air pressure abnormality by comparing an angular signal with a load signal that represents a measured value of an axial load by the load measuring device. A wheel formed by assembling tires around the wheel, a wheel bearing rolling bearing unit for rotatably supporting the wheel with respect to a suspension device, a load measuring device for determining an axial load applied to the wheel, and the load measurement A determination unit that determines whether there is an abnormality in the tire air pressure based on a load signal that represents a measurement value of an axial load by the device, and the determination unit includes a lateral signal of the vehicle body that is represented by the output signal of the vehicle body behavior sensor . An air pressure abnormality determination device that determines the presence or absence of an air pressure abnormality by comparing a behavior and a load signal representing a measured value of an axial load by the load measuring device. A wheel formed by assembling tires around the wheel, a wheel bearing rolling bearing unit for rotatably supporting the wheel with respect to a suspension device, a load measuring device for determining an axial load applied to the wheel, and the load measurement A determination device that determines whether there is an abnormality in the tire air pressure based on a load signal that represents a measurement value of the axial load by the device, and this determination device determines whether there is an air pressure abnormality based on the waveform of the load signal Air pressure abnormality determination device. A wheel formed by assembling tires around the wheel, a wheel bearing rolling bearing unit for rotatably supporting the wheel with respect to a suspension device, a load measuring device for determining an axial load applied to the wheel, and the load measurement A determination unit that determines whether there is an abnormality in the tire air pressure based on a load signal that represents a measurement value of an axial load by the device, the determination unit includes a tire stiffness value estimated based on the load signal, and a memory An air pressure abnormality determination device that determines whether or not there is an air pressure abnormality by comparing a tire stiffness value in a normal state recorded therein. The air pressure abnormality determining device according to claim 4 , wherein the determining device estimates a tire stiffness value based on a moving amount of an acting point of an axial load acting on the wheel supporting rolling bearing unit. A rotating speed detector for determining the rotational speed of the wheels, the determination instrument, in consideration of the rotational speed of the wheel obtained by the rotational speed detection device determines the presence or absence of abnormal air pressure, of the claims 1 to 5 The air pressure abnormality determination device according to any one of the above. The air pressure abnormality determination device according to any one of claims 1 to 6 , wherein the load measuring device is incorporated in a wheel bearing rolling bearing unit.

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