JP5876667B2 - Method for estimating force acting on tire - Google Patents

Description

The present invention relates to an estimation method for estimating at least a vertical force among longitudinal force, lateral force, and vertical force acting on a tire by measuring tire strain in a sidewall portion with a strain sensor.

  In recent years, for example, as shown in FIG. 8, n strain sensors a are attached to different positions in the circumferential direction on one side wall portion of the tire, and tire strain is simultaneously measured at a predetermined tire rotation angle position Q. The n simultaneous sensor outputs VA to Vn obtained in this way cause the longitudinal force Fx, lateral force Fy, and vertical force Fz acting on the tire (hereinafter, these may be collectively referred to as 3 component forces). Has been proposed (see, for example, Patent Document 1). In the figure, the case of n = 4 is shown.

The tire strain ε measured by each strain sensor a appears 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. 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, using this characteristic, by performing multiple regression analysis using n sensor outputs VA to Vn measured simultaneously at different circumferential positions as explanatory variables and the three component forces Fx, Fy, and Fz as objective variables, regression is performed. The following estimation equation, which is an equation, can be obtained.
Fx = fx (VA, VB,..., Vn)
Ff = fy (VA, VB,..., Vn)
Fz = fz (VA, VB,..., Vn)

  However, the conventional method has a problem that it is difficult to sufficiently increase the estimation accuracy of the three component forces Fx, Fy, and Fz. The reason is that the output form of the strain sensor by the longitudinal force Fx and the output form of the strain sensor by the lateral force Fy are similar, so it is difficult to separate the three component forces Fx, Fy, Fz, and the above-described estimation This is presumably because the accuracy of the expression is reduced.

  For example, in the case of the arrangement of a conventional strain sensor, when a longitudinal force Fx is applied to a tire, each of the strain sensors a1 to a4 detects a tensile strain as conceptually shown in FIG. 9A. When the lateral force Fy is applied to the tire, the strain sensors a1 to a4 detect the tensile strain as conceptually shown in FIG. 9B. When the vertical force Fz is applied to the tire, the strain sensors a2 and a3 detect the tensile strain and the strain sensors a1 and a4 detect the compressive strain, as conceptually shown in FIG. 9C. That is, in the longitudinal force Fx and the lateral force Fy, similar output forms are shown in which each of the strain sensors a1 to a4 detects tensile strain. As a result, when the load addition test data is subjected to multiple regression analysis to obtain an estimation formula (regression formula), it becomes unclear whether the strain is derived from longitudinal force or lateral force, and the error becomes large. This is thought to reduce the accuracy of the expression.

Japanese Patent Laid-Open No. 2005-126008

The present invention aims to provide an estimate how forces acting the number of explanatory variables in the tire capable of improving the estimation accuracy while simplifying the estimation equation as one.

In order to solve the above problems, the invention of claim 1, using the sensor output of the strain sensor for measuring the tire distortion in the sidewall portion of the tire, of the longitudinal force, lateral force and vertical force acting on the tire An estimation method for estimating at least vertical force ,
The maximum gain line at which the sensing gain is maximized is attached to the sidewall portion on one side of the tire at equal intervals on the same circumferential line centering on the tire axial center, and 30 to A first strain sensor group comprising six or more n first strain sensors inclined at an angle θ1 of 60 °;
It is attached to the other sidewall of the tire at a symmetrical position facing the first strain sensor across the tire equatorial plane, and the maximum gain line is at an angle θ2 equal to the angle θ1 of the first strain sensor. A second strain sensor group comprising n second sensors inclined in the same direction as the gain maximum line of the first strain sensor;
While using an angle sensor that measures the rotational angle position of the tire,
A strain measuring step for obtaining a sensor output by simultaneously measuring tire strain by the first strain sensor group and the other strain sensor group at a predetermined tire rotation angle position Q;
And a calculation step for obtaining an estimated value of the force acting on the tire based on the sensor output obtained by the strain measurement step,
In the calculation step, the reference sensor output of the first strain sensor in the unloaded tire is VA _i 0 (i = 1, 2,... N), and the reference sensor output of the second strain sensor is VB _i 0. (I = 1, 2,... N)
(C) the sum Σ | VA _i −VA _i 0 | of the absolute value | VA _i −VA _i 0 | of the difference between the sensor output VA _i by the first strain sensor and the reference sensor output VA _i 0; Sum of absolute values | VB _i −VB _i 0 | of the difference between the sensor output VB _i by the second strain sensor and the reference sensor output VB _i 0 Σ | VB _i −VB _i 0 | It is characterized in that the estimated value of the vertical force Fz is obtained using the following estimation formula (3) with _i −VA _i 0 | + Σ | VB _i −VB _i 0 |) as a variable.
Fz = Kz · (Σ | VA _i −VA _i 0 | + Σ | VB _i −VB _i 0 |) + Az −−− (3)
( Kz and Az in the formula are constants)

In the invention of claim 2, the calculation step comprises:
(A) When determining an estimated value of the longitudinal force Fx, the first and the sum ShigumaVA _i of the n sensor outputs VA _i by the distortion sensor, sum ΣVB of the second strain sensor according to the n sensor outputs VB _{i Using} the following estimation formula (1) using the sum of _i and (ΣVA _i + ΣVB _i ) as a variable:
(B) When obtaining the estimated value of the lateral force Fy, the first and the sum ShigumaVA _i of the n sensor outputs VA _i by strain sensors, the second sum of n sensor outputs VB _i by the distortion sensor ΣVB _The following estimation formula (2) using the difference from _i (ΣVA _i −ΣVB _i ) as a variable is used.
Fx = Kx. (ΣVA _i + ΣVB _i ) + Ax −−− (1)
Fy = Ky · (ΣVA _i −ΣVB _i ) + Ay −−− (2)
(Where Kx, Ky, Ax, Ay are constants)

In the present invention, as will be described later in the section “Description of Embodiments”, the sum ΣVA _i of n sensor outputs VA _i by a first strain sensor and n sensors by a second strain sensor. The sum of the sensor output VB _{i and} the sum ΣVB _i (ΣVA _i + ΣVB _i ) can cancel the influence of the lateral force and the vertical force. The influence of the longitudinal force and the vertical force can be offset by the difference (ΣVA _i −ΣVB _i ) between the sum ΣVA _i and the sum ΣVB _i . The absolute value | VA _i -VA _i 0 | of the difference between the sensor output VA _i by the first strain sensor and the reference sensor output VA _i 0 Σ | VA _i -VA _i 0 | The sum of the absolute value | VB _i −VB _i 0 | of the difference between the sensor output VB _i and the reference sensor output VB _i 0 Σ | VB _i −VB _i 0 | (Σ | VA _i −VA _i 0 | + Σ | VB _i −VB _i 0 |) can cancel the influence of the longitudinal force and the lateral force.

Therefore, when the sum (ΣVA i ₊ ΣVB _i) a variable, because the influence of the lateral force and the vertical force is removed are offset from each other, it is possible to estimate the longitudinal force Fx with high accuracy. Also when the difference (ΣVA _i -ΣVB _i) a variable, because the influence of the longitudinal force and the vertical force is removed are offset from each other, it is possible to estimate the lateral force Fy with high accuracy. Also, the sum _{(Σ | VA i -VA i 0} | + Σ | VB i -VB i 0 |) If it is a variable, because the influence of the longitudinal force and the lateral force is removed are offset from one another, the vertical force Fz Can be estimated with high accuracy.

  Moreover, since the number of explanatory variables is small for each of the longitudinal force, lateral force, and vertical force, the estimation formulas for the longitudinal force, lateral force, and vertical force can be simplified, reducing the calculation time. Thus, the time lag can be reduced, and an inexpensive arithmetic unit having a small arithmetic processing capability can be used, so that the cost can be reduced.

  Since the amount of calculation is small, for example, it is possible to attach a calculator to the tire or rim and transmit the longitudinal force, lateral force, and vertical force calculated on the tire side to the vehicle body side. In this case, the number of transmission channels is three, and the number of channels can be greatly reduced compared to the conventional system that transmits each sensor output to the vehicle body. The transmitter can be downsized and the battery consumption time can be extended. Can be achieved.

It is sectional drawing which shows the pneumatic tire used for the force estimation method of this invention. (A) is a top view which shows one Example of a strain sensor, (B) is a side view which shows the direction of the inclination of the gain maximum line. It is a schematic diagram explaining arrangement of a strain sensor. It is a graph which shows the change of the sensor output by the longitudinal force when a tire makes one rotation. It is a graph which shows the change of the sensor output by lateral force when a tire makes one rotation. It is a graph which shows the change of the sensor output by the up-and-down force when a tire makes one rotation. (A)-(C) are the graphs which show notionally the characteristic of the waveform of a sensor output. It is an arrangement view of a strain sensor for explaining a conventional technique. (A)-(C) are explanatory drawings which exaggerate and show distortion of a tire when longitudinal force, lateral force, and vertical force act, respectively.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 shows a cross-sectional view of an embodiment of a pneumatic tire used in the force estimation method of the present invention. In FIG. 1, a pneumatic tire 1 of this example includes a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, an inner side of the tread portion 2, and a radially outer side of the carcass 6. And a belt layer 7 disposed on the surface.

  The carcass 6 is formed of one or more, in this example, one carcass ply 6A in which carcass cords are arranged at an angle of, for example, 70 to 90 ° with respect to the tire circumferential direction. The carcass ply 6A includes a series of ply turn-up portions 6b that are turned back from the inside in the tire axial direction around the bead core 5 on both sides of the ply body portion 6a straddling the bead cores 5 and 5. Further, a bead apex rubber 8 for reinforcing a bead having a triangular cross section extending from the bead core 5 to the outer side in the tire radial direction is disposed between the ply main body portion 6a and the ply folded portion 6b.

  The belt layer 7 is formed from two or more belt plies 7A and 7B in which belt cords are arranged at an angle of, for example, 10 to 35 ° with respect to the tire circumferential direction, and each belt cord is between plies. By crossing each other, the belt rigidity is enhanced, and the substantially entire width of the tread portion 2 is firmly reinforced with a tagging effect. In this example, a band layer 9 in which band cords are arranged at an angle of 5 degrees or less with respect to the circumferential direction is provided on the outer side in the radial direction of the belt layer 7 in order to improve high-speed running performance and high-speed durability. Provided.

  In addition, as shown in FIG. 3, the pneumatic tire 1 is attached to one side wall portion 3A at equal intervals in the tire circumferential direction on the same circumferential line jA around the tire axis. The first strain sensor group including the n first strain sensors 10A described above is disposed, and the other side wall portion 3B has a tire on the same circumferential line jB centered on the tire axis. A second strain sensor group including n second strain sensors 10B attached at equal intervals in the circumferential direction is arranged. The axle is provided with a tire angle distortion sensor (not shown) such as a resolver or an encoder that detects the rotational phase angle of the tire 1. FIG. 3 illustrates the case where n = 6.

  Here, the region Y (shown in FIG. 1) to which the first and second strain sensors 10A and 10B are attached is 25% of the tire cross-section height h with the middle height position M of the tire cross-section height h as the center. An area range that divides the distance h1 inward and outward in the radial direction is preferable, and in particular, an area range that is closer to the intermediate height position M by setting the distance h1 to 20% and further 15% of the tire cross-section height h is preferable. The tire cross-sectional height h means a radial height from the bead base line BL to the tread surface on the tire equator.

  Next, as shown in FIG. 2A, the first and second strain sensors 10A and 10B are composed of one magnet 11 and one magnet facing each other with a gap on the N-pole side of the magnet 11. The sensor element 12 is provided, and in this example, the magnet 11 and the magnetic sensor element 12 are formed as a block-shaped mold body 20 integrated with an elastic material 13. The symbol i in the figure means a gain maximum line i at which the sensing gain is maximum in the first and second strain sensors 10A and 10B. As the magnetic sensor element 12, a Hall element, an MR element (magnetoresistance effect element), a TMF-MI element, a TMF-FG element, an amorphous strain sensor, or the like can be adopted, and in particular, compactness, sensitivity, ease of handling, etc. From the viewpoint, a Hall element can be preferably employed. Further, in the first and second strain sensors 10A and 10B, it is important that the first and second strain sensors 10A and 10B can be elastically deformed flexibly following the movement of the sidewall portion 3, and as a result, various elastic elastic materials can be used as the elastic material 13. Is adopted. In particular, thermoplastic elastomer (TPE) can be molded by plastic molding such as cast molding and injection molding, and can be suitably employed from the viewpoint of manufacturing the molded body 20.

  In the first and second strain sensors 10A and 10B, as shown in FIG. 2B, the angles θ1 and θ2 of the respective maximum gain lines i with respect to the tire radial direction line are within a range of 30 to 60 °. Equally (θ1 = θ2), and each gain maximum line i is inclined in the same direction with respect to the tire circumferential direction. In this example, as shown in FIG. 3, when the rotation direction of the tire is S, the maximum gain line i of the first strain sensor 10A and the maximum gain line i of the second strain sensor 10B are both outside in the tire radial direction. Toward the tire rotation direction S. However, both can be inclined toward the anti-tire rotation direction.

The first and second strain sensors 10A and 10B are attached to symmetrical positions facing each other across the tire equatorial plane Co. Here, “attaching to a symmetrical position” means that the circumferential line jA and the circumferential line jB have the same diameter, and the first and second strain sensors 10A and 10B have substantially the same phase angle. It means that it is provided at a position. The “substantially the same phase angle position” is explained as follows. First, a coordinate system around the tire axis, where the vertical line passing vertically through the tire axis toward the ground contact surface is 0 ° (however, on one side of the tire rotation direction, in this example, the tire rotation direction plus (+ ) in that), 0 ° of the first ~n th sequentially arranged to the positive side from the reference line X0 first strain sensor _10A 1 Arufa1～arufaenu phase angle at 10 a _n, the second strain sensor _10B 1 ~ _Let the phase angle at 10B _{n be} β1 to βn. At this time, the difference between the same phase angles in the first and second strain sensors 10A and 10B, that is, | α1-β1 |, | α2-β2 | ... | αn-βn | The case is said to be at substantially the same phase angle position.

  The axle is provided with a tire angle distortion sensor (not shown) such as a resolver or an encoder that detects the rotational phase angle of the tire 1.

Next , a method for estimating a force including at least the vertical force Fz among the longitudinal force Fx, the lateral force Fy, and the vertical force Fz using the pneumatic tire 1 will be described.
The estimation method is:
(A) a strain measuring step for obtaining a sensor output by simultaneously measuring tire strain by the first strain sensor group and the other strain sensor group at a predetermined tire rotation angle position Q; and
(B) the strain measuring step longitudinal force Fx on the basis of the sensor output V obtained by the lateral force Fy, configured to include a calculating step of obtaining by calculating an estimate of at least the vertical force Fz of the vertical force Fz . In this example, the calculation step shows a case where the estimated values of the longitudinal force Fx, the lateral force Fy, and the vertical force Fz are calculated and obtained.

In the strain measurement step, a tire rotation angle position Q for measuring tire distortion is set in advance, and when the running tire 1 reaches the tire rotation angle position Q, the first and first tire rotation angle positions Q are set. Two strain sensors 10A and 10B simultaneously measure tire strain. As a result, sensor outputs VA _{1 to} VA _{n obtained} by the first strain sensors 10A _{1 to} 10A _n and sensor outputs VB _{1 to} VB _{n obtained} by the second strain sensors 10B _{1 to} 10B _n can be obtained. In this example, as illustrated in FIG. 3, in the coordinate system, one reference strain sensor 10R (which can be arbitrarily selected from 2n strain sensors 10) has a predetermined angle γ position, for example, an angle of + 45 °. The rotation position of the tire when passing through the position P is set as the tire rotation angle position Q. For example, when the angle γ is 0 °, + 15 °, or + 30 °, the tire rotation angle position Q can be set as appropriate. Also, 360 tire rotation angle positions Q can be set by changing the angular position P every one degree. In such a case, a strain measurement step is performed every one degree.

Next, in the calculation step, the reference sensor output of the first strain sensor 10A in the unloaded tire is VA _i 0 (i = 1, 2,... N), and the reference sensor of the second strain sensor 10B. When the output is VB _i 0 (i = 1, 2,... N),
(A) wherein the sum ShigumaVA _i of the n sensor outputs VA _i by first strain sensor 10A, the sum of the sum ShigumaVB _i of the second by the strain sensor 10B n sensors output VB _{i (ΣVA i} + _ΣVB The estimated value of the longitudinal force Fx is obtained using the following estimation formula (1) with _i ) as a variable:
(B) The difference (ΣVA _i −) between the sum ΣVA _{i of} n sensor outputs VA _{i from} the first strain sensor 10A and the sum ΣVB _{i of} n sensor outputs VB _{i from} the second strain sensor 10B. The estimated value of the lateral force Fy is obtained using the following estimation formula (2) with ΣVB _i ) as a variable, or (c) the sensor output VA _i by the first strain sensor 10A and the reference sensor output VA _i 0 Between the absolute value | VA _i −VA _i 0 | of the difference between Σ | VA _i −VA _i 0 | and the sensor output VB _{i from} the second strain sensor 10B and the reference sensor output VB _i 0 next was a variable absolute value _| VB i _-VB i 0 _| sum Σ _| VB i _-VB i 0 _| sum of _{(Σ | VA i -VA i 0} | + Σ | | VB i -VB i 0) The estimated value of the vertical force Fz is obtained using the estimation formula (3).
Fx = Kx. (ΣVA _i + ΣVB _i ) + Ax −−− (1)
Fy = Ky · (ΣVA _i −ΣVB _i ) + Ay −−− (2)
Fz = Kz · (Σ | VA _i −VA _i 0 | + Σ | VB _i −VB _i 0 |) + Az −−− (3)
(Where Kx, Ky, Kz, Ax, Ay, Az are constants)

  And by using said Formula (1)-(3), the three component force Fx, Fy, and Fz can be isolate | separated and estimation accuracy can be improved.

  Here, FIG. 4 shows a change in the sensor output V due to the longitudinal force Fx when the tire is rotated once, and FIG. 5 shows a change in the sensor output V due to the lateral force Fy when the tire is rotated once. 6 shows changes in the sensor output V due to the vertical force Fz when the tire is rotated once.

  Specifically, in FIG. 4, a tire in which one first strain sensor 10A is attached to one side wall portion 3A, a lateral force Fy = 0 (slip angle 0 °), up and down A waveform (output waveform) of the sensor output V when rotated under the condition of force Fz = constant is shown. Only the longitudinal force Fx is changed to 0N (N is Newton), -1200N, -2400N, and -3600N. The minus display of the longitudinal force Fx means the braking force. As is clear from FIG. 4, when the longitudinal force Fx fluctuates, the entire output waveform shifts upward or downward. Further, when the second strain sensor 10B is provided on the other side wall portion 3B, the same output waveform as in FIG. 4 can be obtained.

  FIG. 5 shows a waveform (output waveform) of the sensor output V when the tire is rotated on the drum under the condition that the longitudinal force Fx = 0 and the vertical force Fz is constant. As the lateral force Fy, only the slip angle is changed to 0 °, left 1 °, left 2 °, right 1 °, and right 2 °. As can be seen from FIG. 5, the entire output waveform shifts upward as the slip angle to the right increases, and conversely as the slip angle increases to the left, the entire output waveform shifts downward. Yes. For example, the output waveform at the left 2 ° slip angle is the output at the right 2 ° slip angle output by the second strain sensor 10B when the second strain sensor 10B is provided on the other side wall. Corresponds to the waveform.

  FIG. 6 shows the waveform (output waveform) of the sensor output V when the tire is rotated on the drum under the conditions of longitudinal force Fx = 0 and lateral force Fy = 0 (slip angle 0 °). Has been. Only the vertical force Fz is changed to 4000N, 6000N, and 8000N. As is apparent from FIG. 6, the output waveform shifts upward as the vertical force Fz increases in the front side of the ground center, and the output waveform rises and falls in the rear side of the ground center. As the force Fz becomes larger, it moves downward. Even when the second strain sensor 10B is provided on the other side wall portion, the same output waveform as in FIG. 6 can be obtained.

The above features are conceptually shown in FIGS. 7A to 7C. For example, when the output waveforms (reference output waveforms) of the first and second strain sensors 10A and 10B when traveling straight at a constant speed are WA and WB, as shown in FIG. The output waveforms WAx and WBx when the force Fx is loaded shift from the reference output waveforms WA0 and WB0 to, for example, the lower side (or the upper side), respectively. That is, when the longitudinal force of the tire changes from Fx to Fx + ΔFx during traveling, the sensor output of an arbitrary i-th (i = 1,..., N) first strain sensor 10A _i is from VA _i to VA. _i + [Delta] V _i to vary, also the sensor output of the second strain sensor 10B _i on the other side, changes from VB _i in VB _i + _{ΔV i.}

As shown in FIG. 7B, when a lateral force Fy is applied to the tire, one output waveform WAy shifts upward (or downward) from the reference output waveform WA0, and conversely, Output waveform WBy shifts downward (or upward) from the reference output waveform WB0. That is, when the lateral force of the tire changes from Fy to Fy + ΔFy during traveling, the sensor output of an arbitrary i-th (i = 1,..., N) first strain sensor 10A _i is from VA _i to VA. _i + [Delta] V _i to vary, also the sensor output of the second strain sensor 10B _i on the other side, changes from VB _i in VB _i + _{ΔV i.}

Further, as shown in FIG. 7C, when the vertical force Fz is applied to the tire, both the output waveforms WAz and WBz are the reference output waveforms WA0 and WB0 on the front side (origin side) from the center of contact. On the other hand, on the rear side of the ground center, both output waveforms WAz and WBz shift downward from the reference output waveforms WA0 and WB0, respectively. That is, when the vertical force of the tire changes from Fz to Fz + ΔFz during traveling, the sensor output of an arbitrary i-th (i = 1,..., N) first strain sensor 10A _i is | VA _i | To | VA _i + ΔV _i |, and the sensor output of the second strain sensor 10B _i changes from | VB _i | to | VB _i + ΔV _i |.

Next, it will be verified below that the three component forces Fx, Fy, and Fz can be separated by using the above formulas (1) to (3). As previously mentioned, when the longitudinal force of the tire is changed into Fx + DerutaFx from Fx during travel, the sensor output of the first strain sensor 10A _i changes from VA _i to VA _i + [Delta] V _i, second distortion on the other side the sensor output of the sensor 10B _i varies from VB _i in VB _i + ΔV _i.
Substituting this into equation (1) gives
Fx + ΔFx = Kx · {Σ (VA _i + ΔV _i ) + Σ (VB _i + ΔV _i )} + Ax
= Kx · 2ΣΔV _i + Fx
In other words, the ΔFx = Kx · 2ΣΔV _i.
Also, when substituting into equation (2),
Fy + ΔFy = Ky · {Σ (VA _i + ΔV _i ) −Σ (VB _i + ΔV _i )} + Ay
= Ky · Σ (ΔV _i −ΔV _i ) + Fy
= Fy
That is, ΔFy = 0.
When substituting into equation (3),
Fz + ΔFz = Kz · (Σ | VA i + ΔV i -VA i 0 | + Σ | VB i + ΔV i -VB i 0 |) + Az
= Kz · [Σ {| VA _i −VA _i 0 | + ΔV _i + (− ΔV _i )} + Σ {| VB _i −VB _i 0 | + ΔV _i + (− ΔV _i )} + Az
= Kz · 2Σ {ΔV _i + (− ΔV _i )} + Fz
= Fz
That is, ΔFz = 0. For the vertical force Fz, ΔV _i is displayed as + on the front side (origin side) with respect to the center of contact and is displayed on the rear side.

  Thus, in the above formulas (1) to (3), the longitudinal force change ΔFx does not affect the lateral force and the vertical force, and therefore the longitudinal force can be estimated with high accuracy.

The traveling, when the lateral force of the tire is changed into Fy + ΔFy from Fy, the sensor output of the first strain sensor 10Ai changes from VA _i to VA _i + [Delta] V _i, the sensor output of the second strain sensor 10B _i is , VB _i changes to VB _i −ΔV _i .
Substituting this into equation (1) gives
Fx + ΔFx = Kx · {Σ (VA _i + ΔV _i ) + Σ (VB _i −ΔV _i )} + Ax
= Kx · {Σ (ΔV _i −ΔV _i )} + Fx
= Fx
That is, ΔFx = 0.
Also, when substituting into equation (2),
Fy + ΔFy = Ky · {Σ (VA _i + ΔV _i ) −Σ (VB _i −ΔV _i )} + Ay
= Ky · 2ΣΔV _i + Fy
That is, ΔFy = Ky · 2ΣΔV _i .
When substituting into equation (3),
Fz + ΔFz = Kz · (Σ | VA _i + ΔV _i −VA _i 0 | ++ Σ | VB _i −ΔV _i −VB _i 0 |) + Az
= Kz · [Σ {| VA _i −VA _i 0 | + ΔV _i + (− ΔV _i )} + Σ {| VB _i −VB _i 0 | −ΔV _i − (− ΔV _i )} + Az
= Kz · 2Σ {ΔV _i + (− ΔV _i )} + Fz
= Fz
That is, ΔFz = 0. For the vertical force Fz, ΔV _i is displayed as + on the front side (origin side) with respect to the center of contact and is displayed on the rear side.

  Thus, in the above formulas (1) to (3), the lateral force change ΔFy does not affect the longitudinal force and the vertical force, and therefore the lateral force can be estimated with high accuracy.

The traveling, when the vertical force of the tire is changed from Fz in Fz + DerutaFz, the sensor output of the first strain sensor 10A _i is, | VA _i | from | VA _i + ΔV _i | to change, the second strain sensor 10B _i sensor output is, | VB _i | from | VB _i + [Delta] V _i | to change.
Substituting this into equation (1) gives
Fx + ΔFx = Kx · [Σ {VA _i + ΔV _i + (− ΔV _i )} + Σ {VB _i + ΔV _i + (− ΔV _i )} + Ax
= Kx · 2Σ {ΔV _i + (− ΔV _i )} + Fx
= Fx
That is, ΔFx = 0.
Also, when substituting into equation (2),
Fy + ΔFy = Ky · [Σ {(VA _i + ΔV _i + (− ΔV _i )} − Σ {(VB _i + ΔV _i + (− ΔV _i ))} + Ay
= Ky · [Σ {ΔV _i + (− ΔV _i )} − Σ {ΔV _i + (− ΔV _i )}] + Fy
= Fy
That is, ΔFy = 0.
When substituting into equation (3),
Fz + ΔFz = Kz · (Σ | VA i + ΔV i -VA i 0 | + Σ | VB i + ΔV i -VB i 0 |) + Az
= Kz · (ΣΔV _i + ΣΔV _i ) + Fz
= Kz · 2ΣΔV _i + Fz
That is, ΔFz = Kz · 2ΣΔV _i .

  Thus, in the above formulas (1) to (3), the vertical force change ΔFz does not affect the longitudinal force and lateral force, and therefore the vertical force can be estimated with high accuracy.

The constants Kx, Ky, Kz, Ax, Ay, and Az in the above formulas (1) to (3) can be obtained by a prior load application test in which the longitudinal force Fx, lateral force Fy, and vertical force Fz are different. it can. For example, the tire strain ε when the tire reaches a predetermined tire rotation angle position Q is simultaneously measured by each of the n strain sensors 10A and 10B for each of various different load application conditions, and sensor outputs VA obtained thereby are obtained. From VB, a sum (ΣVA _i + ΣVB _i ), a difference (ΣVA _i −ΣVB _i ), and a sum (Σ | VA _i −VA _i 0 | + Σ | VB _i −VB _i 0 |) are obtained. Then, Fx, Fy, and Fz, which are inputs of the prior load application test, are used as objective variables, and the sum (ΣVA _i + ΣVB _i ), difference (ΣVA _i −ΣVB _i ), sum (Σ | VA _i −VA _i 0 | + Σ | VB _i −VB _i 0 |) can be obtained as an explanatory variable by performing multiple regression analysis.

  The reason why the number of strain sensors 10A and 10B is 6 or more is as follows. As apparent from FIGS. 4 to 6, the angle γ between the maximum and minimum peaks Pa and Pb in each output waveform is about 60 °, but in order to accurately estimate the three-way forces Fx, Fy, and Fz. It is necessary to capture the peaks Pa and Pb of this output waveform. Therefore, six or more first and second strain sensors 10A and 10B are arranged on the circumference, and two peaks Pa, between the adjacent strain sensors 10A and 10A and between the strain sensors 10B and 10B, Pb is prevented from appearing.

In this way, according to the present invention, the sum (ΣVA _i + ΣVB _i ) is used as an explanatory variable so that the influences of the lateral force and the vertical force are canceled out and eliminated, so the longitudinal force Fx is estimated with high accuracy. It becomes possible to do. In addition, by using the difference (ΣVA _i −ΣVB _i ) as an explanatory variable, the influences of the longitudinal force and the vertical force are canceled out and eliminated, so the lateral force Fy can be estimated with high accuracy. . In addition, since the sum (Σ | VA _i −VA _i 0 | + Σ | VB _i −VB _i 0 |) is used as an explanatory variable, the influences of the longitudinal force and the lateral force are canceled out and eliminated. The force Fz can be estimated with high accuracy.

  In addition, since only one explanatory variable is required for each of the longitudinal force, lateral force, and vertical force, the estimation formulas for the longitudinal force, lateral force, and vertical force are simplified as the above equations (1) to (3). The calculation time can be shortened and the time lag can be reduced, and the cost can be reduced because an inexpensive calculator with a small calculation processing capability can be used. Since the amount of calculation is small, for example, it is possible to attach a calculator to the tire or rim and transmit the longitudinal force, lateral force, and vertical force calculated on the tire side to the vehicle body side. In this case, the number of transmission channels is three, and the number of channels can be greatly reduced compared to the conventional system that transmits each sensor output to the vehicle body. The transmitter can be downsized and the battery consumption time can be extended. Can be achieved.

  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.

  As shown in FIG. 3, six (n = 6) first strain sensors 10A on one side wall portion and six second strain sensors 10B on the other side wall portion (n = 6), respectively, on the same circumferential line. Pneumatic tires (size 245 / 40ZR18) attached at equal intervals were made as trial products. The first strain sensor 10A and the second strain sensor 10B are arranged at symmetrical positions with the tire equatorial plane in between. Each strain sensor 10A, 10B uses a molded body in which one magnet and one magnetic sensor element (Hall element--Melxis Hall IC: MLX90251) are integrated with a rubber elastic material. Angles θ1 and θ2 of the 10B gain maximum line N with respect to the tire radial direction line are 45 °, and are inclined outward in the radial direction toward the tire rotation direction S.

  For tires traveling on a flat belt at a speed of 20 km / h, the tires are rotated by the respective strain sensors 10A and 10B at every tire rotation angle of 1 ° (360 tire rotation angle positions are set every 1 °). Strain is measured simultaneously, and from the sensor outputs VA1 to VA6 and VB1 to VB6 obtained thereby, the longitudinal force Fx, the lateral force Fy, and the vertical force Fz are obtained for each rotation angle of the tire by using an estimation formula. The variation of the difference from the actual measurement value actually measured using a force meter was evaluated by 3σ (σ: standard deviation). The smaller 3σ is, the better the variation with the measured value is. Note that the standard deviation is obtained from data composed of 45000 points of samples obtained by allocating force to 45 levels and measuring each level for 1 second.

  In Comparative Example 1, the longitudinal force Fx, the lateral force Fy, and the vertical force Fz are estimated using a primary equation (estimation equation) with sensor outputs VA1 to VA6 and VB1 to VB6 as explanatory variables.

  As shown in the table, it can be confirmed that the estimation method of the embodiment can improve the estimation accuracy.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 3A One side wall part 3B The other side wall part 10A 1st strain sensor 10B 2nd strain sensor Co tire Equatorial plane jA, jB Circumferential line N Gain maximum line

Claims (2)

An estimation method for estimating at least a vertical force among a longitudinal force, a lateral force and a vertical force acting on a tire using a sensor output of a strain sensor that measures tire distortion in a sidewall portion of the tire,
The maximum gain line at which the sensing gain is maximized is attached to the sidewall portion on one side of the tire at equal intervals on the same circumferential line centering on the tire axial center, and 30 to A first strain sensor group comprising six or more n first strain sensors inclined at an angle θ1 of 60 °;
It is attached to the other sidewall of the tire at a symmetrical position facing the first strain sensor across the tire equatorial plane, and the maximum gain line is at an angle θ2 equal to the angle θ1 of the first strain sensor. A second strain sensor group comprising n second sensors inclined in the same direction as the gain maximum line of the first strain sensor;
While using an angle sensor that measures the rotational angle position of the tire,
A strain measuring step for obtaining a sensor output by simultaneously measuring tire strain by the first strain sensor group and the other strain sensor group at a predetermined tire rotation angle position Q;
And a calculation step for obtaining an estimated value of the force acting on the tire based on the sensor output obtained by the strain measurement step,
In the calculation step, the reference sensor output of the first strain sensor in the unloaded tire is VA _i 0 (i = 1, 2,... N), and the reference sensor output of the second strain sensor is VB _i 0. (I = 1, 2,... N)
(C) the sum Σ | VA _i −VA _i 0 | of the absolute value | VA _i −VA _i 0 | of the difference between the sensor output VA _i by the first strain sensor and the reference sensor output VA _i 0; Sum of absolute values | VB _i −VB _i 0 | of the difference between the sensor output VB _i by the second strain sensor and the reference sensor output VB _i 0 Σ | VB _i −VB _i 0 | Estimation of force acting on the tire, characterized in that an estimated value of the vertical force Fz is obtained using the following estimation formula (3) with _i −VA _i 0 | + Σ | VB _i −VB _i 0 |) as a variable: Method.
Fz = Kz · (Σ | VA _i −VA _i 0 | + Σ | VB _i −VB _i 0 |) + Az −−− (3)
(Kz and Az in the formula are constants)
The calculation step includes:
(A) When obtaining the estimated value of the longitudinal force Fx, the sum ΣVA _i of n sensor outputs VA _i by the first strain sensor and the sum ΣVB of n sensor outputs VB _i by the second strain sensor _Using the following estimation formula (1) using the sum of _i and (ΣVA _i + ΣVB _i ) as a variable:
(A) When obtaining the estimated value of the lateral force Fy, the sum ΣVA _i of the n sensor outputs VA _i by the first strain sensor and the sum ΣVB of the n sensor outputs VB _i by the second strain sensor _The method for estimating a force acting on a tire according to claim 1, wherein the following estimation formula (2) using a difference (ΣVA _i −ΣVB _i ) from _i as a variable is used.
Fx = Kx. (ΣVA _i + ΣVB _i ) + Ax −−− (1)
Fy = Ky · (ΣVA _i −ΣVB _i ) + Ay −−− (2)
(Where Kx, Ky, Ax, Ay are constants)

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