JP2011073646A - Method for estimating force on tire, and tire and tire wheel assembly to be used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for estimating longitudinal force Fx, vertical force Fz and lateral force Fy with high accuracy while suppressing trouble of a tire. <P>SOLUTION: The method uses a sensor unit 7 which consists of one magnet 8 mounted on a sidewall portion 2b and first-fourth magnetic sensors 9a-9d mounted on a tire wheel 3, and in which sensor centers C1, C2 of the magnetic sensors 9a, 9b and sensor centers C3, C4 of the third and forth magnetic sensors 9c, 9d are located at an equal distance La on both sides of a peripheral reference line Θ passing through an intersection P and sensor centers C1, C4 of the magnetic sensors 9a, 9d and sensor centers C2, C3 of the second and third magnetic sensors 9b, 9c are located at the distance La on both sides of a radial reference line R passing through the intersection P and extending in a tire radial direction. It includes a measuring step of producing sensor outputs V1-V4 using the magnetic sensors 9a, 9d, and a computing step of finding at least one of the longitudinal force Fx, the vertical force Fz, and the lateral force Fy in accordance with the sensor outputs V1-V4. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an estimation method for estimating a force acting on a tire by using a sensor unit including one magnet attached to a sidewall portion of a tire and four magnetic sensors attached to a tire wheel, and the tire and the tire wheel used therefor And the assembly.

  In recent years, n strain sensors are attached to tire sidewall portions at different positions in the tire circumferential direction, and tire strain is simultaneously measured at a predetermined tire rotation position, and n simultaneous sensor outputs V1 obtained thereby are obtained. A technique for estimating the longitudinal force Fx, the lateral force Fy, and the vertical force Fz acting on the tire based on ˜Vn has been proposed (see, for example, Patent Document 1).

  Here, the tire strain ε measured by each strain sensor is measured only as the sum of the strain εx caused by the longitudinal force Fx, the strain εy caused by the lateral force Fy, and the strain εz caused by the vertical force Fz (ε = εx + εy + εz). However, at different circumferential positions, the relationship between the longitudinal force Fx and its strain εx, the relationship between the lateral force Fy and its strain εy, and the relationship between the vertical force Fz and its strain εz are different for each circumferential position. , Each has a characteristic of appearing differently. Therefore, by using this difference in characteristics and using n sensor outputs V1 to Vn measured simultaneously at different circumferential positions, the acting forces Fx, Fy, and Fz acting at that time can be separately estimated. It becomes possible.

Japanese Patent Laid-Open No. 2005-126008

  However, in the proposed technique, it is necessary to transmit the sensor output from the strain sensor attached to the tire to an electronic control unit (ECU) on the vehicle body side.

  As this transmission means, for example, it is conceivable that each strain sensor has a wireless transmission function. However, it is necessary to provide a small strain sensor with a wireless transmission function. It is a big hindrance. As another method, a wireless device may be attached to the tire wheel, and the wireless device and each strain sensor may be connected by a lead wire passing through the tire. However, in this case, an external force acts on the lead wire due to air resistance, centrifugal force, or the like during traveling, so that a measurement error becomes large, such as affecting tire distortion, and there is a problem that estimation accuracy is reduced. Moreover, since the said lead wire repeats bending deformation following a tire, there also exists a possibility of a disconnection.

  Therefore, the present invention is based on using a sensor unit comprising one magnet attached to the sidewall portion of the tire and four magnetic sensors attached to the tire wheel, and specifying the arrangement position of the four magnetic sensors. A method for estimating a force acting on a tire that can accurately estimate the longitudinal force Fx, the vertical force Fz, and the lateral force Fy while suppressing an increase in cost and problems such as measurement errors and disconnections caused by the lead wire, and the method used therefor An object of the present invention is to provide an assembly of a tire and a tire wheel.

In order to solve the above-mentioned problem, the invention of claim 1 of the present application provides a magnet that is attached to a sidewall portion of a tire and has a magnetic flux center on a meridional surface including a tire axis, and a tire wheel on which the tire is mounted. An estimation method for estimating a force acting on a tire using a sensor unit including a magnetic sensor group including first, second, third, and fourth magnetic sensors that are attached and detect magnetic flux from the magnet. ,
The first, second, third, and fourth magnetic sensors are disposed on a reference plane S1 orthogonal to the magnetic flux center of the magnet at an intersection P,
Moreover, in a no-load state where no force is acting on the tire,
The sensor centers C1 and C2 of the first and second magnetic sensors and the sensor centers C3 and C4 of the third and fourth magnetic sensors pass through the intersection point P with respect to the circumferential reference line Θ extending in the tire circumferential direction. Located on both sides at an equal distance La from the circumferential reference line Θ,
The sensor centers C1 and C4 of the first and fourth magnetic sensors and the sensor centers C2 and C3 of the second and third magnetic sensors pass through the intersection point P in the radial direction of the tire R. And a distance Lb equal to the distance La from the radial reference line R, and
While traveling, the magnetic output from the magnet is detected by the first, second, third, and fourth magnetic sensors, respectively, so that the sensor output V1 of the first magnetic sensor and the sensor output V2 of the second magnetic sensor are detected. A measurement step of obtaining a sensor output V3 of the third magnetic sensor and a sensor output V4 of the fourth magnetic sensor;
And a calculation step for obtaining at least one of the longitudinal force Fx, the vertical force Fz, and the lateral force Fy acting on the tire based on the sensor outputs V1, V2, V3, and V4.

According to a second aspect of the present invention, in the calculation step, each sensor output varies from the difference between the sensor outputs V1, V2, V3, V4 and the reference sensor outputs V01, V02, V03, V04 in the no-load state. Fluctuation amount obtaining step for obtaining amounts ΔV1, ΔV2, ΔV3, and ΔV4, and from the variation amounts ΔV1, ΔV2, ΔV3, and ΔV4, the displacement amount dθ in the circumferential direction of the magnet, the displacement amount dr in the radial direction, and the magnetic flux center direction A displacement amount obtaining step for obtaining a displacement amount dj of
A displacement amount conversion step for converting the displacement amounts dθ, dr, dj into a displacement amount DX in the longitudinal direction of the magnet, a displacement amount DZ in the vertical direction, a displacement amount DY in the lateral direction, or a displacement amount DT in the torsion direction;
An operation force calculating step for obtaining a longitudinal force Fx from the longitudinal displacement amount DX, a vertical force Fz from the vertical displacement amount DZ, or a lateral force Fy from the lateral displacement amount DY.

The invention according to claim 3 is an assembly of a tire and a tire wheel used in a method for estimating a force acting on the tire, wherein the center of magnetic flux passes through the meridian plane that is attached to the sidewall of the tire and includes the tire axis. A sensor unit is provided that includes one magnet and a magnetic sensor group including first, second, third, and fourth magnetic sensors that are attached to a tire wheel on which the tire is mounted and that detect magnetic flux from the magnet. With
The first, second, third, and fourth magnetic sensors are disposed on a reference plane S1 orthogonal to the magnetic flux center of the magnet at an intersection P,
Moreover, in a no-load state where no force is acting on the tire,
The sensor centers C1 and C2 of the first and second magnetic sensors and the sensor centers C3 and C4 of the third and fourth magnetic sensors pass through the intersection point P with respect to the circumferential reference line Θ extending in the tire circumferential direction. Located on both sides at an equal distance La from the circumferential reference line Θ,
The sensor centers C1 and C4 of the first and fourth magnetic sensors and the sensor centers C2 and C3 of the second and third magnetic sensors pass through the intersection point P in the radial direction of the tire R. And a distance Lb equal to the distance La from the radial reference line R.

  The present invention uses a sensor unit including one magnet that is attached to a sidewall portion of a tire and four magnetic sensors that are attached to a tire wheel. Therefore, even when a wireless device is attached to the tire wheel side and this wireless device is connected to the magnetic sensor with a lead wire, since the lead wire is wired irrespective of the tire, an external force acts on the lead wire. Also, the measurement accuracy can be kept high without adversely affecting the tire distortion. Moreover, since there is no repeated bending deformation following the tire, disconnection can be suppressed.

  Further, since the magnetic flux of one magnet is detected by four magnetic sensors in a specific arrangement, the longitudinal force Fx, the vertical force Fz, and the lateral force Fy are obtained by calculation from the sensor outputs V1 to V4, that is, estimated. be able to.

It is sectional drawing which shows one Example of the assembly of the tire and tire wheel used for the estimation method of the force which acts on the tire of this invention. It is a side view which expands and shows the principal part. It is a side view which shows an example of arrangement | positioning of a sensor unit. It is the arrow surface which looked at the positional relationship of a magnet and the 1st-4th magnetic sensor from the magnetic flux center direction. It is the arrow surface which looked at the positional relationship of a magnet and the 1st-4th magnetic sensor from the magnetic flux center from the right angle direction. (A), (B) is the graph which shows the state of the change of the sensor output by the distance between magnets, and an arrangement | positioning figure at that time. It is a conceptual diagram which shows the positional relationship of the magnet in a no-load state, and the 1st-4th magnetic sensor. (A)-(C) are side views which show the deformation | transformation state of a tire when front-back force, up-down force, and lateral force act.

  Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is a cross-sectional view showing an example of an assembly 1 (hereinafter referred to as a tire assembly 1) of a tire and a tire wheel used in a method for estimating a force acting on a tire according to the present invention. The assembly 1 includes a tire 2, a tire wheel 3 on which the tire 2 is mounted, and at least one sensor unit 7.

  The tire 2 is formed at a tread portion 2a that comes into contact with the road surface, a pair of sidewall portions 2b extending inward in the tire radial direction from both ends in the tire axial center direction, and radially inner ends of the respective sidewall portions 2b. A pneumatic tire having a bead portion 2c, which is reinforced by a well-known tire cord layer (not shown) including a carcass and a belt layer, and imparts necessary rigidity, strength, durability, and the like. .

  In the present example, the tire wheel 3 includes a wheel body 5 fixed to the axle 4 and a cosmetic wheel cap 6 attached to the wheel body 5. The wheel body 5 has a well-known structure including a substantially disk-shaped disc portion 5A that is bolted to the hub portion at the tip of the axle 4 and a rim portion 5B that is assembled and mounted with the bead portion 2c of the tire 2.

  The wheel cap 6 has a plurality of fitting projections 6b extending inward in the axial direction toward the wheel main body 5 on the inner surface of a substantially disc-shaped cap main portion 6a covering the wheel main body 5. Formed side by side. The fitting projection 6b has a locking claw portion 6b1 that fits with a fitting recess 5B1 provided on the inner surface in the radial direction of the rim portion 5B in this example at the inner end in the axial center direction. As a result, the wheel cap 6 can be attached to the wheel body 5 with high accuracy with one touch and without being displaced. The means for fixing the wheel cap 6 to the wheel body 5 is not limited to the fitting protrusion 6b of this example, and various conventional ones are employed.

  Next, at least one sensor unit 7 is attached to the tire assembly 1. In this example, as shown in FIGS. 2 and 3, a case where a plurality of (for example, six) sensor units 7 are attached at equal intervals in the circumferential direction is illustrated. Each sensor unit 7 has a single magnet 8 attached to the sidewall portion 2b of the tire 2, and first, second, third, and fourth attached to the tire wheel 3 and detecting magnetic flux from the magnet 8. The magnetic sensor group includes magnetic sensors 9a, 9b, 9c, and 9d. The first, second, third, and fourth magnetic sensors 9a, 9b, 9c, and 9d are collectively referred to as a magnetic sensor 9.

  The magnet 8 is attached so that the magnetic flux center j passes on the meridian plane S0 including the tire axis i. The magnet 8 can be adhered on the outer surface of the sidewall portion 2b or can be embedded in the rubber of the sidewall portion 2b. As the magnet 8, a rare earth magnet capable of obtaining a high magnetic flux density is suitable. However, depending on the type, there is a problem that demagnetization occurs due to heat during vulcanization and a sufficient sensor output cannot be obtained. Therefore, the magnet 8 is preferably a samarium cobalt magnet (so-called samacoba magnet) having a high Curie temperature and a small change in magnetic flux density due to the temperature.

  The first to fourth magnetic sensors 9a to 9d are attached to the wheel cap 6 in this example. As shown in FIGS. 1 and 2, the wheel cap 6 includes extending portions 6c extending radially outward from the outer peripheral edge of the cap main portion 6a, and the first to fourth magnetic sensors are provided in the extending portions 6c. 9a to 9d are mounted on the reference plane S1 orthogonal to the magnetic flux center j at the intersection P and in the following arrangement. Specifically, as shown in FIGS. 4 and 5, in the no-load state where no force is applied to the tire, the sensor centers C1, C2 of the first and second magnetic sensors 9a, 9b, The sensor centers C3 and C4 of the fourth magnetic sensors 9c and 9d are separated from the circumferential reference line Θ by an equal distance La on both sides of the circumferential reference line Θ extending in the tire circumferential direction through the intersection P. Arranged. The sensor centers C1 and C4 of the first and fourth magnetic sensors 9a and 9d and the sensor centers C2 and C3 of the second and third magnetic sensors 9b and 9c pass through the intersection point P in the tire radial direction. On both sides of the extending radial reference line R, a distance Lb equal to the distance La from the radial reference line R is arranged.

  The magnetic flux center j means a straight line passing through the center of the magnetic pole surface on one side and the center of the magnetic pole surface on the other side of the magnet 8, and the magnetic flux density is highest at the magnetic flux center j. The sensor centers C1 to C4 mean the center of the area of the sensor element in the magnetic sensor.

  As the magnetic sensor 9, sensors using sensor elements such as Hall elements, MR elements (magnetoresistance effect elements), TMF-MI elements, TMF-FG elements, etc. can be adopted, and particularly compactness, sensitivity, and ease of handling. From the viewpoint of the above, a device using a Hall element can be suitably employed. Further, the wheel cap 6 includes a control device 10 (shown in FIG. 1) including a power source for operating each magnetic sensor 9 and a wireless device for transmitting a sensor output signal from each magnetic sensor 9 to an electronic control device on the vehicle side. ) And the control device 10 and each magnetic sensor 9 are connected by lead wires (not shown).

  In this example, a ferromagnetic material such as iron, cobalt, nickel, or the like is interposed between the magnetic sensor 9 and the extension 6c so that the magnetic flux from the magnet 8 can stably pass through the magnetic sensor 9. It is preferable to interpose a magnetic plate 11 (shown in FIG. 5). The wheel body 5 and the wheel cap 6 are preferably formed of a nonmagnetic material such as aluminum, copper, or synthetic resin in order to avoid adverse effects on the magnetic flux.

  Next, an estimation method for estimating at least one of the longitudinal force Fx, the vertical force Fz, and the lateral force Fy acting on the tire using the tire assembly 1 will be described.

  This estimation method includes a measurement step and a calculation step. In the measurement step, the magnetic flux from the magnet 8 is detected by the first to fourth magnetic sensors 9a to 9d during traveling, and thereby the first step is performed. The sensor output V1 of the first magnetic sensor 9a, the sensor output V2 of the second magnetic sensor 9b, the sensor output V3 of the third magnetic sensor 9c, and the sensor output V4 of the fourth magnetic sensor 9d are obtained. The sensor outputs V1 to V4 are collectively referred to as sensor output V.

  In the measurement step, the angular position of the sensor unit 7 at the time of detecting the magnetic flux is measured, or the magnetic flux is detected when the sensor unit 7 reaches a predetermined angular position. The angular position can be detected by, for example, attaching an angle sensor (not shown) such as a resolver or an encoder that measures the tire rotation angle around the axis of the axle 4 to the vehicle body. In this example, as shown in FIG. 3, a vertical line extending from the tire axis i to the anti-contact surface side is defined as a reference position N, and an angle α from the reference position N (0 °) to the intersection P of the sensor unit 7. Is used to display the angular position of each sensor unit 7. The angle α is + in the tire rotation direction.

  Here, in the magnetic sensor 9, the sensor output V changes according to the strength of the magnetic field penetrating the sensor element, and the strength of the magnetic field changes according to the distance between the magnetic sensor 9 and the magnet 8. To do. Therefore, the distance between the magnetic sensor 9 and the magnet 8 or the displacement amount of the magnet 8 can be obtained from the sensor output V or the variation ΔV thereof. 6 (A) and 6 (B), the distance A in the direction of the magnetic flux center between the magnet 8 and the magnetic sensor 9 and the distance B from the magnetic flux center j to the sensor center C of the magnetic sensor 9 are different. The change of the sensor output V of the magnetic sensor 9 is shown. As the magnet 8, a cylindrical magnet having a diameter of 3.0 mm and a magnetic flux density of 310 mT was used, and as the magnetic sensor 9, a magnet having a Hall element (Merixis MLX90251) was used. As shown in the figure, the sensor output V (output voltage) changes in the range of 3.5 to 10.0 mm in the distance A in the magnetic flux center direction, and the distance in the direction perpendicular to the magnetic flux center j. The sensor output V (output voltage) changes within the range of B from 0 to 3 mm. Accordingly, the distances La and Lb (corresponding to the distance B) in the magnetic sensors 9a to 9d are preferably 2.0 mm or less, and the distance Lc (corresponding to the distance A) in the magnetic flux center direction from the magnet 8 of the magnetic sensors 9a to 9d. ) Is preferably in the range of 3.5 to 10.0 mm.

  Next, in the calculation step, at least one of the longitudinal force Fx, the vertical force Fz, and the lateral force Fy is obtained by calculation based on the sensor outputs V1, V2, V3, and V4. In this example, the calculation step includes a fluctuation amount acquisition step, a displacement amount acquisition step, a displacement amount conversion step, and an action force calculation step.

  In the fluctuation amount acquisition step, each sensor output is calculated from the difference between the sensor outputs V1, V2, V3, V4 measured during driving and the reference sensor outputs V01, V02, V03, V04 measured in advance in a no-load state. Fluctuations ΔV1 (= V1−V01), ΔV2 (= V2−V02), ΔV3 (= V3−V03), and ΔV4 (= V4−V04) are obtained.

  In the displacement amount acquisition step, the displacement amount dθ in the circumferential direction of the magnet 8, the displacement amount dr in the radial direction, and the displacement amount dj in the magnetic flux center direction are calculated from the variation amounts ΔV1, ΔV2, ΔV3, and ΔV4, respectively. Ask.

  FIG. 7 is a conceptual diagram showing the positional relationship between the magnet 8 and the magnetic sensors 9a to 9b in the no-load state, and the magnet 8 ′ during travel is displaced in the circumferential direction from the magnet 8 in the no-load state by the acting force. It is displaced by an amount dθ, a displacement amount dr in the radial direction, and a displacement amount dj in the magnetic flux center direction. The displacement amount dθ is smaller than the distance Lb, the displacement amount dr is smaller than the distance La, and the displacement amount dj is smaller than the distance Lc.

Here, the variation ΔV1 in the first magnetic sensor 9a includes a variation component ΔV1θ based on the circumferential displacement dθ, a variation component ΔV1r based on the radial displacement dr, and a displacement in the magnetic flux center direction. It is shown as the sum of the fluctuation amount component ΔV1j based on dj.
The variation ΔV2 in the second magnetic sensor 9b includes a variation component −ΔV2θ based on the circumferential displacement dθ, a variation component ΔV2r based on the radial displacement dr, and a displacement dj in the magnetic flux center direction. It is shown as the sum with the fluctuation amount component ΔV2j based on.
The variation ΔV3 in the third magnetic sensor 9c includes a variation component −ΔV3θ based on the circumferential displacement dθ, a variation component −ΔV3r based on the radial displacement dr, and a displacement in the direction of the magnetic flux center. It is shown as the sum of the fluctuation amount component ΔV3j based on dj.
The variation ΔV4 in the fourth magnetic sensor 9d includes a variation component ΔV4θ based on the circumferential displacement dθ, a variation component −ΔV4r based on the radial displacement dr, and a displacement dj in the magnetic flux center direction. It is shown as the sum with the fluctuation amount component ΔV4j based on.
When the magnet 8 is displaced in the circumferential direction by the displacement amount dθ, the second and third magnetic sensors 9b and 9c are separated from the magnet 8 (that is, the sensor output is reduced), so the variation component is − (minus). It is displayed. Similarly, when the magnet 8 is displaced in the radial direction by the displacement amount dr, the third and fourth magnetic sensors 9c and 9d are separated from the magnet 8 (that is, the sensor output is reduced), so the variation component is − ( Minus) is displayed.
ΔV1 = ΔV1θ + ΔV1r + ΔV1j
ΔV2 = −ΔV2θ + ΔV2r + ΔV2j
ΔV3 = −ΔV3θ−ΔV3r + ΔV3j
ΔV4 = ΔV4θ−ΔV3r + ΔV3j

  At this time, the sensor centers C1 and C2 of the first and second magnetic sensors 9a and 9b and the sensor centers C3 and C4 of the third and fourth magnetic sensors 9c and 9d are on both sides of the circumferential reference line Θ. The sensor centers C1 and C4 of the first and fourth magnetic sensors 9a and 9d and the sensor centers C2 and C3 of the second and third magnetic sensors 9b and 9c are arranged in a radial direction with an equal distance La therebetween. Since they are arranged at equal distances Lb on both sides of the reference line R, ΔV1θ = ΔV4θ, ΔV2θ = ΔV3θ, ΔV1r = ΔV2r, ΔV3r = ΔV4r, ΔV1j = ΔV2j = ΔV3j = ΔV4j.

Therefore, when (ΔV1 + ΔV4) − (ΔV2 + ΔV3) is considered, in this equation, the variation components ΔV1r to ΔV4r in the radial direction and the variation components ΔV1j to ΔV4j in the magnetic flux center direction are canceled out, and the variation component ΔV1θ in the circumferential direction It is shown as the sum of only ~ ΔV4θ.
(ΔV1 + ΔV4) − (ΔV2 + ΔV3) = ΔV1θ + ΔV2θ + ΔV3θ + ΔV4θ --- (1)
Thereby, the displacement dθ in the circumferential direction can be expressed as a function of (ΔV1 + ΔV4) − (ΔV2 + ΔV3) as in the following equation (2).
dθ = f {(ΔV1 + ΔV4)-(ΔV2 + ΔV3)} --- (2)

Similarly, when (ΔV1 + ΔV2) − (ΔV3 + ΔV4) is considered, in this equation, the fluctuation amount components ΔV1θ to ΔV4θ in the circumferential direction and the fluctuation amount components ΔV1j to ΔV4j in the magnetic flux center direction are canceled, and the fluctuation amount component in the radial direction. It is shown as the sum of only ΔV1r to ΔV4r.
(ΔV1 + ΔV2) − (ΔV3 + ΔV4) = ΔV1r + ΔV2r + ΔV3r + ΔV4r --- (3)
As a result, the displacement dr in the radial direction can be expressed as a function of (ΔV1 + ΔV2) − (ΔV3 + ΔV4) as in the following equation (4).
dr = f {(ΔV1 + ΔV2)-(ΔV3 + ΔV4)} --- (4)

In the first to fourth magnetic sensors 9a to 9d, since La = Lb, ΔV1θ≈ΔV2θ, ΔV3θ≈ΔV4θ, ΔV1r≈ΔV3r, ΔV2r≈ΔV4r. Therefore, when (ΔV1 + ΔV2 + ΔV3 + ΔV4) is considered, in this expression, the fluctuation amount components ΔV1θ to ΔV4θ in the circumferential direction and the fluctuation amount components ΔV1r to ΔV4r in the radial direction are canceled out, and only the fluctuation amount components ΔV1j to ΔV4j in the magnetic flux center direction. It is shown as the sum of
(ΔV1 + ΔV2 + ΔV3 + ΔV4) = ΔV1j + ΔV2j + ΔV3j + ΔV4j --- (5)
Thus, the displacement dj in the direction of the magnetic flux center can be expressed as a function of (ΔV1 + ΔV2 + ΔV3 + ΔV4) as in the following equation (6).
dj = f (ΔV1 + ΔV2 + ΔV3 + ΔV4) --- (6)

  That is, by obtaining the sensor output fluctuation amounts ΔV1, ΔV2, ΔV3, and ΔV4, the displacement amounts dθ, dr, and dj of the magnet 8 are obtained using the equations (2), (4), and (6), respectively. Can do. In addition, said Formula (2), (4), (6) can be previously calculated | required by the prior load addition test. Specifically, many load application tests are performed, and data of dθ and ΔV1, ΔV2, ΔV3, and ΔV4, data of dr and ΔV1, ΔV2, ΔV3, and ΔV4, dj and ΔV1, ΔV2, ΔV3, By regression analysis of data with ΔV4, the above equations (2), (4), and (6) are obtained as regression equations with dθ, dr, and dj as objective variables and ΔV1, ΔV2, ΔV3, and ΔV4 as explanatory variables. be able to.

In the displacement amount conversion step, the displacement amounts dθ, dr, dj obtained in the displacement amount acquisition step are changed to the displacement amount DX in the front-rear direction, the displacement amount DZ in the vertical direction, or the displacement amount DY in the lateral direction of the magnet 8. Convert. When the rotation angle from the reference position N of the sensor unit 7 at the time of detecting the magnetic flux is α, the displacement amount DX in the front-rear direction, the displacement amount DZ in the vertical direction, and the displacement amount DY in the lateral direction are the displacement amounts dθ, dr, It is represented by the following formula using dj. That is, it can be converted. As shown in FIG. 1, the angle β is an angle with respect to the axial direction of the magnetic flux center j.
DX = dθ · cosα−dj · sinα · sinβ−dr · sinα · cosβ
DY = dj · cosβ-drsinβ
DZ = dθ · sinα + dj · cosα · sinβ + dr · cosα · cosβ
If β ≒ 0,
DX = dθ · cos α−dr · sin α
DY = dj
DZ = dθ · sinα + dj · cosα
It becomes.

In the acting force calculation step, the longitudinal force Fx, the vertical force Fz, and the lateral force Fy are obtained from the longitudinal displacement amount DX, the vertical displacement amount DZ, and the lateral displacement amount DY, respectively. 8A to 8C show the deformation state of the sidewall portion 2b of the tire 2 when the longitudinal force Fx, the vertical force Fz, and the lateral force Fy are applied to the tire 2, respectively. There is a relationship of the following formulas (7) to (9) between the displacement amount and the acting force.
Fx = Ka · DX --- (7)
Fz = Kb · DZ --- (8)
Fy = Kc · DY --- (9)

  Therefore, by using the equations (7) to (9), the longitudinal force Fx, the vertical force Fz, and the lateral force Fy can be obtained from the displacement amounts DX, DZ, and DY, respectively. In addition, said Formula (7)-(9) or constant Ka-Kc is the longitudinal force Fx and vertical force Fz which were calculated | required by the prior load addition test similarly to the case of said Formula (2), (4), (6). It can be obtained in advance by analyzing the data of the lateral force Fy and the displacement amounts DX, DZ, DY. The expressions (7) to (9) are set according to the value of the angle α.

  When a plurality of sensor units 7 are provided as in this example, the front / rear force Fx, the vertical force Fz, and the lateral force Fy can be estimated simultaneously by each sensor unit 7. In this case, it is possible to further increase the estimation accuracy by averaging the estimated values of the sensor units 7.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

DESCRIPTION OF SYMBOLS 1 Assembly of tire and tire wheel 2 Tire 2b Side wall part 3 Tire wheel 7 Sensor unit 8 Magnet 9a 1st magnetic sensor 9b 2nd magnetic sensor 9c 3rd magnetic sensor 9d 4th magnetic sensor i Tire shaft Heart j Magnetic flux center S0 Meridian

Claims (3)

One magnet that is attached to the sidewall portion of the tire and that passes through the meridional plane including the tire axis, and that is attached to the tire wheel to which the tire is mounted and that detects the magnetic flux from the magnet. An estimation method for estimating a force acting on a tire using a sensor unit including a magnetic sensor group including third and fourth magnetic sensors,
The first, second, third, and fourth magnetic sensors are disposed on a reference plane S1 orthogonal to the magnetic flux center of the magnet at an intersection P,
Moreover, in a no-load state where no force is acting on the tire,
The sensor centers C1 and C2 of the first and second magnetic sensors and the sensor centers C3 and C4 of the third and fourth magnetic sensors pass through the intersection point P with respect to the circumferential reference line Θ extending in the tire circumferential direction. Located on both sides at an equal distance La from the circumferential reference line Θ,
The sensor centers C1 and C4 of the first and fourth magnetic sensors and the sensor centers C2 and C3 of the second and third magnetic sensors pass through the intersection point P in the radial direction of the tire R. And a distance Lb equal to the distance La from the radial reference line R, and
While traveling, the magnetic output from the magnet is detected by the first, second, third, and fourth magnetic sensors, respectively, so that the sensor output V1 of the first magnetic sensor and the sensor output V2 of the second magnetic sensor are detected. A measurement step of obtaining a sensor output V3 of the third magnetic sensor and a sensor output V4 of the fourth magnetic sensor;
A force acting on the tire, including a calculation step for obtaining at least one of the longitudinal force Fx, the vertical force Fz, and the lateral force Fy acting on the tire based on the sensor outputs V1, V2, V3, and V4. Estimation method. The calculation step includes fluctuation amounts ΔV1, ΔV2, ΔV3, ΔV4 of each sensor output based on differences between the sensor outputs V1, V2, V3, V4 and reference sensor outputs V01, V02, V03, V04 in the no-load state. The displacement amount obtaining step for obtaining the displacement amount and the displacement amounts ΔV1, ΔV2, ΔV3, and ΔV4 for obtaining the displacement amount dθ in the circumferential direction of the magnet, the displacement amount dr in the radial direction, and the displacement amount dj in the magnetic flux center direction, respectively. A quantity acquisition step;
A displacement amount conversion step for converting the displacement amounts dθ, dr, dj into a displacement amount DX in the longitudinal direction of the magnet, a displacement amount DZ in the vertical direction, or a displacement amount DY in the lateral direction;
And an acting force calculating step for obtaining a longitudinal force Fx from the longitudinal displacement amount DX, a vertical force Fz from the vertical displacement amount DZ, or a lateral force Fy from the lateral displacement amount DY. A method for estimating a force acting on a tire according to 1. An assembly of a tire and a tire wheel used in a method for estimating a force acting on a tire according to claim 1 or 2, wherein the magnetic flux center passes through a meridional surface that is attached to a sidewall of the tire and includes a tire axis. A sensor unit including a magnet and a magnetic sensor group including first, second, third, and fourth magnetic sensors that are attached to a tire wheel on which the tire is mounted and that detects magnetic flux from the magnet;
The first, second, third, and fourth magnetic sensors are disposed on a reference plane S1 orthogonal to the magnetic flux center of the magnet at an intersection P,
Moreover, in a no-load state where no force is acting on the tire,
The sensor centers C1 and C2 of the first and second magnetic sensors and the sensor centers C3 and C4 of the third and fourth magnetic sensors pass through the intersection point P with respect to the circumferential reference line Θ extending in the tire circumferential direction. Located on both sides at an equal distance La from the circumferential reference line Θ,
The sensor centers C1 and C4 of the first and fourth magnetic sensors and the sensor centers C2 and C3 of the second and third magnetic sensors pass through the intersection point P in the radial direction of the tire R. The tire and tire wheel assembly is located on both sides of the tire at a distance Lb equal to the distance La from the radial reference line R.

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