JP5542037B2 - Method for estimating force acting on tire - Google Patents

Description

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

  As an estimation method for estimating any of the longitudinal force, lateral force, and vertical force acting on the tire using the sensor output of the strain sensor that measures the tire strain in the sidewall portion of the tire, the following Patent Document 1 is disclosed. Are known.

  In Patent Document 1, as shown in FIG. 8, a first strain sensor a in which a gain maximum line i is inclined to one side in the tire circumferential direction at an angle θ of 45 ° with respect to a tire radial direction line, and a gain maximum line. At least four pairs of sensor pairs c including a second strain sensor b in which i is inclined to the other side in the tire circumferential direction at an angle of 45 ° with respect to the tire radial direction line, And it equip | installs at equal intervals on one circumference line centering on a tire axial center. Then, at a predetermined tire rotation angle position Q, the tire strain is simultaneously measured by the first and second strain sensors a and b, and based on the sensor outputs V of the strain sensors a and b obtained thereby, The tire acting force acting at the tire rotation angle position Q is calculated.

  Specifically, polar coordinates are set around the tire axis, with the vertical line extending upward from the tire axis being 0 ° and the anti-rotation direction of the tire being positive, and at the predetermined tire rotation angle position Q, The sum ΣVr of the sensor outputs Vr of the strain sensors a and b located in the tire traveling direction rear side region Yr in which the coordinate angle in the polar coordinates is larger than 0 ° and smaller than 180 °, and the coordinate angle is more than 180 °. The longitudinal force is calculated based on the difference (ΣVr−ΣVf) of the sum ΣVf of the sensor outputs Vf of the strain sensors a and b located in the tire traveling direction front side region Yf that is a large angle range smaller than 360 °. .

  As for the lateral force, the lateral force is calculated based on the sum ΣV of the sensor outputs V of all the strain sensors.

  Further, in the vertical force, the sum ΣVu of the strain output Vu of the strain sensor located in the tire upper side area Yu where the coordinate angle in the polar coordinate is larger than 270 ° and smaller than 90 °, and the coordinate angle in the polar coordinate is The vertical force is calculated based on the difference (ΣVu−ΣVs) from the total sum ΣVs of the strain outputs Vs of the strain sensors located in the tire lower region Ys which is an angle range larger than 90 ° and smaller than 270 °.

  In this case, only the difference (ΣVr−ΣVf) is a variable in the longitudinal force estimation formula, only the sum ΣV is a variable in the lateral force estimation formula, and only the difference (ΣVu−ΣVs) is in the vertical force estimation formula. Becomes a variable. In other words, the estimation formula can be simplified such that the number of explanatory variables is one with respect to the objective variable, so that the calculation time can be shortened, the time lag can be reduced, and a calculator with a small memory capacity can be used. It is also advantageous to reduce

  However, since the first and second strain sensors a and b forming the sensor pair are arranged close to each other, the magnet of one strain sensor affects the output of the other strain sensor, and the sensor accuracy is reduced. Reduce. As a result, there is a problem that it is difficult to increase the estimation accuracy to a sufficiently satisfactory level.

  In Patent Document 2 below, three or more n strain sensors are attached to the sidewall portions on both sides at intervals on the same circumference, and the tire strain is measured at the predetermined tire rotation angle position Q. It is described that 2n sensor outputs V are obtained by simultaneous measurement, and that the longitudinal force, lateral force, and vertical force are obtained using the 2n sensor outputs V as explanatory variables.

  In this case, since the number of explanatory variables increases to 2n, although the estimation accuracy can be improved, the error increases with the increase of the explanatory variables, so it is difficult to increase the estimation accuracy to a level that can be sufficiently satisfied. In addition, the calculation time is increased and the time lag is increased, the calculation amount is increased, and it is necessary to use an arithmetic unit having a large memory capacity. The sensor output V and the tire distortion amount have a non-linear relationship. Therefore, the estimation accuracy can be improved by using the first and second terms of the 2n sensor outputs V as explanatory variables, respectively. Proposed. However, in this case as well, the error increases as the number of explanatory variables increases, so that the estimation accuracy is not sufficiently improved, and the calculation time is further increased, resulting in a great disadvantage due to the time lag and cost.

JP 2009-46046 A JP 2010-215178 A

  Therefore, the present invention has an object to provide a method for estimating a force acting on a tire that can improve the accuracy of estimation of longitudinal force, lateral force, and vertical force while simplifying the estimation formula with one explanatory variable, for example. Yes.

In order to solve the above problems, the invention of claim 1 of the present application uses any one of the longitudinal force, lateral force and vertical force acting on the tire by using the sensor output of the strain sensor for measuring the tire strain in the sidewall portion of the tire. An estimation method for estimating
A first strain comprising three or more n first strain sensors that are attached to a sidewall portion on one side of the tire at equal intervals in the tire circumferential direction on the same circumferential line centered on the tire axis. A group of sensors;
A second strain sensor group comprising the n second strain sensors attached to the sidewall portion on the other side of the tire at equal intervals in the tire circumferential direction on the same circumferential line centered on the tire axis; ,
Using an angle sensor that measures the rotational angle position of the tire,
A strain measuring step for obtaining 2n sensor outputs by simultaneously measuring tire strain by the first and second strain sensors of the first and second strain sensor groups at a predetermined tire rotation angle position Q;
A calculation step of obtaining an estimated value of a force acting on the tire based on the 2n sensor outputs,
Each of the first strain sensors has an angle θ of 45 ° with respect to a tire radial direction line of a gain maximum line at which a sensing gain is maximum, and each gain maximum line is inclined in the same direction in the tire circumferential direction,
Each of the second strain sensors has the same angle θ with respect to the tire radial direction line of the maximum gain line and the inclination direction in the tire circumferential direction as the first strain sensor,
Moreover, the calculation step includes:
(A) Sum (N _VA + N) of an average value N _VA of n sensor outputs VA from the first strain sensor and an average value N _VB of n sensor outputs VB from the second strain sensor _VB ) is used as a variable to obtain an estimated value of the longitudinal force Fx using the following estimation formula (1).
(B) Obtain an estimated value of the lateral force Fy using the following estimation formula (2) with the difference between the average values N _VA and N _VB (N _VA −N _VB ) as a variable, or (c) Tire rotation angle At the position Q, the average value N _VF of the sensor outputs VF of the first and second strain sensors arranged in the front region that is the front side in the tire traveling direction with respect to the vertical line passing through the tire axis, and the vertical line Also, the following estimation formula using the difference (N _VF −N _VR ) from the average value N _VR of the sensor outputs VR of the first and second strain sensors arranged in the rear region, which is the rear side in the tire traveling direction, as a variable An estimated value of the vertical force Fz is obtained using (3).
Fx = f ( _NVA + _NVB ) ---- (1)
Fy = f (N _VA −N _VB ) −−− (2)
Fz = f (N _VF −N _VR ) −−− (3)

  The invention according to claim 2 is characterized in that the first and second strain sensors are provided at substantially the same phase angle position.

The invention according to claim 3 is characterized in that the estimation equation (1) is the following linear equation (1a).
_{Fx = Kx · (N VA +} N VB) + Ax --- (1a)
(Kx and Ax in the formula are constants)

The invention of claim 4 is characterized in that the estimation equation (2) is the following linear equation (2a).
_{Fy = Ky · (N VA -N} VB) + Ay --- (2a)
(Ky and Ay in the formula are constants)

The invention according to claim 5 is characterized in that the estimation equation (3) is the following linear equation (3a).
Fz = Kz · (N _VF −N _VR ) + Az −−− (3a)
(Kz and Az in the formula are constants)

  As described above, according to the present invention, n first strain sensors are circumferentially arranged on one side wall portion, and n second strain sensors are circumferentially arranged on the other side wall portion. It is separated. Therefore, it is possible to secure a sufficient distance between adjacent strain sensors in the circumferential direction, and to prevent the magnet of one strain sensor from affecting the output of the other strain sensor and lowering the sensor accuracy.

Further, as will be described later in the section “Description of Embodiment”, an average value N _VA of n sensor outputs VA from the first strain sensor and n pieces of n outputs from the second strain sensor. the sum of the average value _{N VB} sensor output _{VB (N VA + N VB)} , lateral force and can offset the influence of a vertical force, the average value _{N VA,} by the difference _{N VB (N VA -N VB)} , longitudinal force and can offset the influence of a vertical force, and the first is disposed on the front side area, and the average value N _VF of the sensor output VF of the second strain sensor, first arranged on the rear region, second The influence of the longitudinal force and the lateral force can be offset by the difference (N _VF −N _VR ) from the average value N _VR of the sensor outputs VR of the strain sensors.

Therefore, the longitudinal force Fx is estimated using the sum (N _VA + N _VB ) as a variable, the lateral force Fy is estimated using the difference (N _VA −N _VB ) as a variable, and the vertical force It becomes possible to estimate Fz with an estimation formula using the difference (N _VF −N _VR ) as a variable. That is, since the number of explanatory variables is as small as one, for example, the estimation formulas for the longitudinal force, lateral force, and vertical force can be simplified, the calculation time can be shortened and the time lag can be reduced, and the memory capacity can be reduced. Since a small and inexpensive arithmetic unit can be used, the cost can be reduced. Moreover, since the occurrence of errors can be suppressed as the number of explanatory variables decreases, it is possible to contribute to improvement in estimation accuracy.

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 the schematic explaining the arrangement | positioning 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.

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 6 </ b> A includes a series of ply folding portions 6 b that are folded from the inner side to the outer side in the tire axial direction around the bead core 5 on both sides of the ply main body portion 6 a that extends between 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 centering on 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 the 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.

  In FIG. 3, four (n = 4) first strain sensors 10A are provided on one side wall portion 3A, and four second strain sensors 10B are provided on the other side wall portion 3B. The case where it attaches at equal intervals on the circumference lines jA and jB of the same radius, respectively is illustrated.

  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 side wall portion 3. 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 angle θ of each gain maximum line i with respect to the tire radial direction line is 45 °, 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 gain maximum line i of the first strain sensor 10A and the gain maximum line i of the second strain sensor 10B are both in the tire radial direction. It inclines toward the tire rotation direction S side. However, both can be inclined toward the anti-tire rotation direction.

  It is preferable that the first strain sensor 10A and the second strain sensor 10B are provided at substantially the same phase angle position. The substantially same phase angle position is described as follows. First, as shown in FIG. 3, a coordinate system around the tire shaft center, where the vertical line passing vertically through the tire shaft core toward the ground contact surface is 0 ° (however, one side in the tire rotation direction, in this example, In the tire rotation direction S (plus (+)), the phase angles of the first to nth first strain sensors 10A1 to 10An sequentially arranged from the 0 ° reference line X0 to the plus side are α1 to αn. The phase angles at the first to nth second strain sensors 10B1 to 10Bn are β1 to βn. At this time, when the difference between the phase angles of the same number, that is, | α1-β1 |, | α2-β2 |... | Αn−βn | That's it.

  Further, it is preferable that the first and second strain sensors 10A and 10B have a built-in transmission means for transmitting the sensor output to the electronic control unit (ECU) of the vehicle control system. This transmitting means is composed of a semiconductor in which a transmission / reception circuit, a control circuit, a memory, etc. are made into a chip, and an antenna. When receiving an interrogation radio wave from the electronic control unit (ECU), this is used as electric energy, The distortion output data in the memory can be transmitted as a response radio wave.

Next, a method for estimating the three component forces Fx, Fy, and Fz will be described using the pneumatic tire 1.
The estimation method is:
(A) At a predetermined tire rotation angle position Q, 2n sensor outputs V are obtained by simultaneously measuring tire strain by the first and second strain sensors 10A and 10B of the first and second strain sensor groups. A strain measurement step,
(B) a calculation step for calculating an estimated value of any one of the longitudinal force Fx, the lateral force Fy, and the vertical force Fz based on the 2n sensor outputs V measured in the strain measurement step;
It is comprised including.

  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. Thereby, 2n sensor outputs V 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 angular position of + 45 °. The rotation position of the tire when passing through 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,
(A) the average value _{N VA} of the n sensor outputs VA from the first strain sensor 10A, the sum of the average value _{N VB} of the n sensor outputs VB from the second strain sensor 10B (N _(VA + N _VB ) is used as a variable to obtain an estimated value of the longitudinal force Fx using the following estimation formula (1).
(B) Obtain an estimated value of the lateral force Fy using the following estimation formula (2) with the difference between the average values N _VA and N _VB (N _VA −N _VB ) as a variable, or (c) Tire rotation angle At the position Q, the average value N _VF of the sensor outputs VF of the first and second strain sensors 10AF, 10BF arranged in the front region YF which is the front side in the tire traveling direction from the vertical line T passing through the tire axis The difference (N _VF −N) from the average value N _VR of the sensor outputs VR of the first and second strain sensors 10AR and 10BR arranged in the rear region YR which is the rear side in the tire traveling direction from the vertical line T. The estimated value of the vertical force Fz is obtained using the following estimation formula (3) with _VR ) as a variable.
Fx = f ( _NVA + _NVB ) ---- (1)
Fy = f (N _VA −N _VB ) −−− (2)
Fz = f (N _VF −N _VR ) −−− (3)

  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 apparent from FIG. 6, the output waveform portion in the front region YF of the output waveform shifts upward as the vertical force Fz increases, and the output waveform portion in the rear region YR 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. That is, when the output waveforms (reference output waveforms) of the first and second strain sensors 10A and 10B during reference running (for example, straight running at a constant speed) are WA0 and WB0, FIG. As described above, the output waveforms WAx and WBx when the longitudinal force Fx is applied to the tire shift from the reference output waveforms WA0 and WB0 to the lower side (or the upper side), for example.

  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.

  Further, as shown in FIG. 7C, when the vertical force Fz is applied to the tire, both output waveforms WAz and WBz shift upward from the reference output waveforms WA0 and WB0 in the front region YF, respectively. On the contrary, in the rear region YR, both output waveforms WAz and WBz shift downward from the reference output waveforms WA0 and WB0, respectively.

Therefore, when considering the average _{N WAX} of the output waveform WAX in the tire one revolution, the average _{N WBX} output waveform WBX, the sum of the average _{N WAX} and the average _{N WBx (N WAx + N WBx} ) is the longitudinal force Fx It can be increased or decreased depending on That is, the sum (N _WAx + N _WBx ) and the longitudinal force Fx have a correlation. On the other _hand , since the difference between the average N _WAx and the average N _WBx (N _WAx −N _WBx ) cancels each other and becomes 0, the difference (N _WAx −N _WBx ) has a correlation with the longitudinal force Fx. Absent.

Further, when considering the average _{N WAY} of the output waveform WAY in the tire one revolution, the average _{N WBY} output waveform WBY, the sum of the average _{N WAY} and the average _{N WBy (N WAy + N WBy} ) the reference output it approaches a constant value which is the sum of the average _{N WB0} average _{N WA0} and the reference output waveform WB0 waveform _{WA0 (N WA0 + N WB0)} . That is, the sum (N _WAY + N _WBy ) and the lateral force Fy have no correlation. On the other _hand , since the difference (N _WAY -N _WBy ) between the average N _WAY and the average N _WBy can be increased or decreased according to the lateral force Fy, the difference (N _WAY -N _WBy ) and the lateral force Fy are correlated. There is.

Further, when considering the average _{N WAZ} of the output waveform WAZ in the tire one revolution, the average _{N WBZ} output waveform WBZ, the sum of the average _{N WAZ} and the average _{N WBz (N WAz + N WBz} ) the reference output it is the sum of the average _{N WB0} average _{N WA0} and the reference output waveform WB0 waveform _{WA0 (N} WA0 _{+ NWB0)} approaches a constant value. That is, the sum (N _WAz + N _WBz ) and the vertical force Fz have no correlation. _Further , the difference between the average N _WAz and the average N _WBz (N _WAz −N _WBz ) cancels each other and becomes 0, so the difference (N _WAz −N _WBz ) and the vertical force Fz are not correlated.

Also in the front region YF, and average _{N FWAx} output waveform WAX, sum _(N FWAx ₊ N _FWBx) and the average _{N FWBx} output waveform WBX, and in the rear region YR, the average _{N RWAx} of the output waveform WAX, output in the sum of the average _{N RWBx} waveform _{WBx (N RWAx + N RWBx)} , the difference of the sum and _(N FWAx ₊ N _FWBx) the sum _{(N RWAx + N RWBx) {} (N FWAx + N FWBx) - (N RWAx + N RWBx) } Approaches a constant value that is the sum of the average N _WAx and the average N _WBx (N _WAx + N _WBx ). That is, the difference {(N _FWAx + N _FWBx ) − (N _RWAx + N _RWBx )} between the sum (N _FWAx + N _FWBx ) and the sum (N _RWAx + N _RWBx ) has no correlation with the front-rear force Fx.

_Further , the sum (N _FWAy + N _FWBy ) of the average N _FWAy of the output waveform _WAy and the average N _FWBy of the output waveform WBy in the front side region YF is the average N _FWA0 of the reference output waveform WA0 in the front side region YF. And a constant value that is the sum (N _FWA0 + N _FWB0 ) of the average N _FWB0 of the reference output waveform WB0. _Further , the sum (N _RWAy + N _RWBy ) of the average N _RWAy of the output waveform _WAy and the average N _RWBy of the output waveform WBy in the rear region YR is the average N _RWA0 of the reference output waveform WA0 in the rear region YR. And a constant value that is the sum (N _RWA0 + N _RWB0 ) of the average N _RWB0 of the reference output waveform WB0. Accordingly, the difference {(N _FWAy + N _FWBy ) − (N _RWAy + N _RWBy )} between the sum (N _FWAy + N _FWBy ) and the sum (N _RWAy + N _RWBy ) approaches a constant value, and has no correlation with the lateral force Fy. .

But in the front side region YF, and average _{N FWAz} output waveform WAZ, the sum of the average _{N FWBz} output waveform _{WBz (N FWAz + N FWBz)} , and in the rear region YR, the average _{N RWAz} of the output waveform WAZ, the output in the sum of the average _{N RWBz} waveform _{WBz (N RWAz + N RWBz)} , the difference of the sum and _(N FWAz ₊ N _FWBz) the sum _{(N RWAz + N RWBz) {} (N FWAz + N FWBz) - (N RWAz + N RWBz) } Can be increased or decreased according to the vertical force Fz, and therefore has a correlation with the vertical force Fz.

In summary,
(A) Sum (N _WAx + N _WBx ) ---- There is a correlation with Fx:
(B) Difference (N _WAx −N _WBx ) _—no correlation with Fx:
(C) Sum ( _N.sub.WAy + _N.sub.WBy ) _--- no correlation with Fy:
( _D ) Difference ( _{N.sub.WAy- N.sub.WBy} ) ---- Fy and correlation:
( _E ) Sum (N _WAz + N _WBz ) ---- No correlation with Fz:
( _F ) Difference (N _WAz −N _WBz ) _—no correlation with Fz:
( _G ) Difference {(N _FWAx + N _FWBx ) − (N _RWAx + N _RWBx )} — no correlation with Fx:
( _H ) Difference {(N _FWAy + N _FWBy ) − (N _RWAy + N _RWBy )} — no correlation with Fy:
(K) Difference {(N _FWAz + N _FWBz ) − (N _RWAz + N _RWBz )} — correlated to Fz:

  Here, strictly speaking, the average of the output waveforms corresponds to the average of the sensor outputs V of the respective strain sensors 10 when an infinite number of strain sensors 10 are mounted on the circumferential line of the sidewall portion. When the number of 10 is finite, the average of the sensor outputs V of the strain sensor 10 can be substituted.

That is,
The average N _WAx can be replaced with an average value N _VA of n sensor outputs VA of the first strain sensor 10A,
The average N _WBx can be replaced with an average value N _VB of n sensor outputs VB of the second strain sensor 10B.
The average N _WAY can be replaced with an average value N _VA of n sensor outputs VA of the first strain sensor 10A,
The average _NWBy can be replaced with an average value N _VB of n sensor outputs VB of the second strain sensor 10B.
The average N _WAz can be replaced with an average value N _VA of n sensor outputs VA of the first strain sensor 10A,
The average N _WBz can be replaced with an average value N _VB of n sensor outputs VB of the second strain sensor 10B.
The sum of the average N _FWAx and the average N _FWBx can be replaced with twice the average value N _FV of the sensor output VF of the first and second strain sensors 10A and 10B arranged in the front region YF.
The sum of the average N _RWAx and the average N _RWBx can be replaced with twice the average value N _RV of the sensor output VF of the first and second strain sensors 10A and 10B arranged in the rear region YR.
The sum of the average N _FWAy and the average N _FWBy can be replaced with twice the average value N _FV of the sensor output VF of the first and second strain sensors 10A and 10B arranged in the front side region YF.
The sum of the average N _RWAy and the average N _RWBy can be replaced with twice the average value N _RV of the sensor output VF of the first and second strain sensors 10A and 10B arranged in the rear region YR.
The sum of the average N _FWAz and the average N _FWBz can be replaced with twice the average value N _FV of the sensor output VF of the first and second strain sensors 10A and 10B arranged in the front region YF.
The sum of the average N _RWAz and the average N _RWBz can be replaced with twice the average value N _RV of the sensor output VF of the first and second strain sensors 10A and 10B arranged in the rear region YR.

Therefore, from the above (a), (c), and (e), it is understood that the sum (N _VA + N _VB ) has a correlation with the longitudinal force Fx, but has no correlation with the lateral force Fy and the vertical force Fz. . From the above (a), (d), and (f), it can be seen that the difference (N _VA -N _VB ) has a correlation with the lateral force Fy, but has no correlation with the longitudinal force Fx and the vertical force Fz. . From the above (ki) to (g), it can be seen that the difference (N _FV −N _RV ) has a correlation with the vertical force Fz, but has no correlation with the longitudinal force Fx and the lateral force Fy.

Therefore, the longitudinal force Fx is expressed by the estimation formula (1) using (N _VA + N _VB ) as a variable, and the lateral force Fy is calculated by using the estimation formula (2) using a difference (N _VA −N _VB ) as a variable. Further, the vertical force Fz can be obtained with high accuracy by the estimation equation (3) using the difference (N _VF −N _VR ) as a variable.

As the estimation equations (1) to (3), the following linear equations (1a) to (3a) can be adopted. In such a case, the number of explanatory variables is one, so that the calculation time is shortened. Thus, the time lag can be reduced, and an inexpensive arithmetic unit with a small memory capacity can be used, so that the cost can be reduced.
_{Fx = Kx · (N VA +} N VB) + Ax --- (1a)
(Kx and Ax in the formula are constants)
_{Fy = Ky · (N VA -N} VB) + Ay --- (2a)
(Ky and Ay in the formula are constants)
Fz = Kz · (N _VF −N _VR ) + Az −−− (3a)
(Kz and Az in the formula are constants)

The estimation equations (1) to (3) or the estimation equations (1a) to (3a) can be obtained by a prior load application test in which the longitudinal force Fx, the lateral force Fy, and the vertical force Fz are different. . For example, tire strain ε when a tire reaches a predetermined tire rotation angle position Q is simultaneously measured by each of the n first and second strain sensors 10A and 10B for each of various different load application conditions. From the obtained sensor outputs VA and VB, the average value N _{VA of} the sensor output _VA , the average value N _VB of the sensor output VB, and the sensor outputs VF of the first and second strain sensors 10A and 10B arranged in the front region YF. Average value N _VF , and the average value N _VR of the sensor outputs VR of the first and second strain sensors 10A, 10B arranged in the rear region YR. Then, Fx, Fy, and Fz, which are inputs of a prior load application test, are used as objective variables, and the sum (N _VA + N _VB ), difference (N _VA −N _VB ), and difference (N _FV −N _RV ) of the average values are used. Can be obtained by performing multiple regression analysis with each as an explanatory variable.

  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, a pneumatic tire in which three (n = 3) strain sensors 10A and 10B are attached to both side wall portions on the same circumferential line j at equal intervals in the circumferential direction. (Size 245 / 40ZR18) was prototyped. The strain sensors 10A and 10B are arranged at symmetrical positions (same phase positions) across the tire equatorial plane. Each strain sensor 10A, 10B uses a molded body in which one magnet and one magnetic sensor element (Hall element--Hel IC manufactured by Melxis: MLX90251) are integrated with a rubber elastic material, and its gain is maximum. The angle θ of the line i with respect to the tire radial line is constant at 45 °, and is inclined toward the tire rotation direction S toward the outer side in the radial direction.

  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 a total of six sensor outputs VA1 to VA3 and VB1 to VB3 obtained thereby are used to estimate the longitudinal force Fx, lateral force Fy, and vertical force Fz for each tire rotation angle of 1 ° using an estimation formula. The variation of the difference from the actual measurement value actually measured using a 6-component 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 yet embodiment, the longitudinal force Fx, the sum of the average value _{N VA} and the average value _{N VB} sensor output VB1~VB3 sensor output VA1~VA3 _(N VA ₊ N _VB) variables and the linear expression (estimated equation ( 1a)), and the lateral force Fy is estimated by a linear equation (see estimation equation (1b)) using the difference between the average values N _VA and N _VB (N _VA −N _VB ) as a variable, vertical force Fz is first disposed in the front side area, and the average value N _VF of the sensor output VF of the second strain sensor of the first sensor output VR of the second strain sensor that is disposed on the rear side region the difference between the average value _{N VR} of _(N VF _{-N VR)} was estimated by a linear expression was used as a variable (estimation equation (1c) refer).

  In Comparative Example 1, the longitudinal force Fx, the lateral force Fy, and the vertical force Fz are estimated using a linear equation (estimation equation) with the sensor outputs VA1 to VA3 and VB1 to VB3 as variables.

  In Comparative Example 2, the longitudinal force Fx, the lateral force Fy, and the vertical force Fz are estimated using a quadratic equation (estimation equation) with the sensor outputs VA1 to VA3 and VB1 to VB3 as variables.

  In Comparative Example 3, estimation was performed based on the estimation method described in Patent Document 1 described in the background art section. Specifically, as shown in FIG. 8, the first strain sensor a in which the maximum gain line i is inclined to one side in the tire circumferential direction at an angle of 45 ° with respect to the tire radial direction line, and the maximum gain line i. Are arranged in the side wall portion on one side and the tire axis center with the second strain sensor b inclined to the other side in the tire circumferential direction at an angle of 45 ° with respect to the tire radial direction line. It is mounted on a single circumferential line j at the center with equal intervals. The difference between the sum ΣVr of the sensor outputs Vr of the strain sensors a and b located in the tire traveling direction rear region Yr and the sum ΣVf of the sensor outputs Vf of the strain sensors a and b located in the tire traveling direction front region Yf. The longitudinal force is calculated based on (ΣVr−ΣVf). In the lateral force, the lateral force is calculated based on the sum ΣV of the sensor output V of the total strain sensor, and in the vertical force, the strain located in the tire upper region Yu. The vertical force is calculated based on the difference (ΣVu−ΣVs) between the sum ΣVu of the strain output Vu of the sensor and the sum ΣVs of the strain output Vs of the strain sensor located in the tire lower region Ys.

  As shown in the table, it can be confirmed that the estimation method of the embodiment can improve the estimation accuracy while the number of explanatory variables is one.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 3 Side wall part 3A One side wall part 3B The other side wall part 10 Strain sensor 10A 1st strain sensor 10B 2nd strain sensor N Gain maximum line

Claims (5)

An estimation method for estimating one of the longitudinal force, lateral force, and vertical force acting on the tire using the sensor output of a strain sensor that measures tire strain in the sidewall portion of the tire,
A first strain comprising three or more n first strain sensors that are attached to a sidewall portion on one side of the tire at equal intervals in the tire circumferential direction on the same circumferential line centered on the tire axis. A group of sensors;
A second strain sensor group comprising the n second strain sensors attached to the sidewall portion on the other side of the tire at equal intervals in the tire circumferential direction on the same circumferential line centered on the tire axis; ,
Using an angle sensor that measures the rotational angle position of the tire,
A strain measuring step for obtaining 2n sensor outputs by simultaneously measuring tire strain by the first and second strain sensors of the first and second strain sensor groups at a predetermined tire rotation angle position Q;
A calculation step of obtaining an estimated value of a force acting on the tire based on the 2n sensor outputs,
Each of the first strain sensors has an angle θ of 45 ° with respect to a tire radial direction line of a gain maximum line at which a sensing gain is maximum, and each gain maximum line is inclined in the same direction in the tire circumferential direction,
Each of the second strain sensors has the same angle θ with respect to the tire radial direction line of the maximum gain line and the inclination direction in the tire circumferential direction as the first strain sensor,
Moreover, the calculation step includes:
(A) Sum (N _VA + N) of an average value N _VA of n sensor outputs VA from the first strain sensor and an average value N _VB of n sensor outputs VB from the second strain sensor _VB ) is used as a variable to obtain an estimated value of the longitudinal force Fx using the following estimation formula (1).
(B) Obtain an estimated value of the lateral force Fy using the following estimation formula (2) with the difference between the average values N _VA and N _VB (N _VA −N _VB ) as a variable, or (c) Tire rotation angle At the position Q, the average value N _VF of the sensor outputs VF of the first and second strain sensors arranged in the front region that is the front side in the tire traveling direction with respect to the vertical line passing through the tire axis, and the vertical line Also, the following estimation formula using the difference (N _VF −N _VR ) from the average value N _VR of the sensor outputs VR of the first and second strain sensors arranged in the rear region, which is the rear side in the tire traveling direction, as a variable A method for estimating a force acting on a tire, wherein an estimated value of the vertical force Fz is obtained using (3).
Fx = f ( _NVA + _NVB ) ---- (1)
Fy = f (N _VA −N _VB ) −−− (2)
Fz = f (N _VF −N _VR ) −−− (3)   The method of estimating a force acting on a tire according to claim 1, wherein the first and second strain sensors are provided at substantially the same phase angle position. The method for estimating a force acting on a tire according to claim 1 or 2, wherein the estimation formula (1) is the following linear formula (1a).
_{Fx = Kx · (N VA +} N VB) + Ax --- (1a)
(Kx and Ax in the formula are constants) 3. The method for estimating a force acting on a tire according to claim 1, wherein the estimation formula (2) is the following linear formula (2a).
_{Fy = Ky · (N VA -N} VB) + Ay --- (2a)
(Ky and Ay in the formula are constants) The method for estimating a force acting on a tire according to claim 1 or 2, wherein the estimation formula (3) is the following linear formula (3a).
Fz = Kz · (N _VF −N _VR ) + Az −−− (3a)
(Kz and Az in the formula are constants)

Images