JP5045244B2 - Tire behavior calculation method - Google Patents

Description

  The present invention relates to a tire behavior calculation method for calculating tire behavior when a vehicle turns.

  Generally, in a vehicle steering apparatus, when the steering wheel is steered by a driver, the rotational motion of the steering shaft is converted into the linear motion of the rack bar. The steering force is transmitted to the knuckle arm via the rack bar, whereby the knuckle arm rotates around the kingpin and the steered wheels are steered (see, for example, Patent Document 1). The knuckle arm is connected to the vehicle body by an upper arm or a lower arm. For example, the upper arm and the lower arm are connected to a part of the vehicle body via a rubber bush on the inner end side, and are connected to the knuckle arm via a ball joint on the outer end side.

In calculating the tire behavior such as the tire turning angle in such a vehicle steering apparatus, generally, an arithmetic processing based on the specifications of the suspension apparatus that supports the steered wheels is performed. Mechanism analysis software capable of calculating such tire behavior is also generally available on the market.
JP 2006-103390 A

  However, in the conventional tire behavior calculation processing, generally, for example, calculation that takes into account the force and moment acting on the tire (hereinafter also referred to as “tire generation force”) such as the force generated between the tire and the road surface. Has not been made. For this reason, for example, when the tire behavior at the time of turning of the vehicle is calculated, it may not be consistent with the actual measurement value.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a highly accurate calculation method for tire behavior that can be matched with actual measurement values when the vehicle turns.

  In order to solve the above-described problem, an aspect of the present invention provides a tire behavior calculation method for calculating tire behavior at the time of turning of a vehicle, a tire behavior initial value calculation step of calculating tire behavior based on initial input information, and A tire generation force calculation step for calculating tire generation force from the calculated tire behavior, a tire behavior calculation step for calculating tire behavior based on the calculated tire generation force, a tire generation force calculation step and a tire behavior calculation step In the process of repeatedly executing, a convergence determination step for determining whether the tire behavior has converged, and a calculation value output step for outputting the convergence value as a tire behavior calculation result when it is determined that the tire behavior has converged And comprising.

  Here, “tire behavior” can target various parameters related to the operation of the steered wheels when the vehicle is turning, and can include, for example, the position, posture (angle) of the steered wheels, and the amount of change thereof. . For example, the camber angle of a steering wheel, a toe angle (cutting angle), etc. may be sufficient. In this aspect, when one is calculated in the calculation process of the tire behavior and the tire generated force, the calculation process is repeated by feeding back to the other. Initial input information is input at the beginning of the calculation of the tire behavior. This “initial input information” can be set in advance, for example, as a temporary value of the tire generating force.

  According to this aspect, the tire generation force and the tire behavior are repeatedly calculated, and the convergence value is output as the calculation result of the tire behavior. That is, each calculation result is fed back to each other in each calculation process of the tire generation force and the tire behavior, and the force applied to the tire in the process of the repeated calculation balances and the calculation values converge. Here, tire generation force is considered in the calculation of the tire behavior, and a stable calculation result after convergence is obtained, so that the consistency with the actually measured value is also improved.

  Specifically, the tire behavior calculation step may include a step of calculating changes in the camber angle and toe angle of the steered wheels when the vehicle turns as the tire behavior. The tire generation force calculation step may include a step of calculating a lateral force acting on the tire as a tire generation force and a step of calculating a moment acting on the tire. Thus, the accuracy of the calculation result can be improved by considering the lateral force and moment as the tire generating force.

  The convergence determination step may calculate the Ackermann rate from the calculated tire behavior, and may determine that the tire behavior has converged when the change amount of the Ackermann rate is within a preset convergence determination value.

  The “Ackermann rate” here can be defined as the ratio of the design inner / outer wheel cut angle difference to the theoretical inner / outer wheel cut angle difference when the turning center of the vehicle is on the extension of the rear axle. . As the Ackermann rate increases, the slip of the tire during vehicle turning can be suppressed, but the value becomes a constant value based on the steering of the vehicle. That is, since it can be said that the tire behavior at the time of vehicle turning can be specified by the convergence of the Ackermann rate, the calculation result is output with the convergence here.

  More specifically, in the tire generation force calculation step, a calculation process including a moment generated by a difference in turning radius in each part of the tire contact surface may be performed as a moment. In the tire generation force calculation step, a calculation process including a moment generated due to a difference in tire radius at each portion of the contact surface with a change in the camber angle of the tire may be performed. In this way, the tire behavior can be calculated with higher accuracy by taking into account the moment associated with the behavior of the tire due to turning of the vehicle.

  ADVANTAGE OF THE INVENTION According to this invention, the highly accurate calculation method of the tire behavior which can take an adjustment with the measured value at the time of vehicle turning can be provided.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a vehicle steering apparatus to which a tire behavior calculation method according to the present embodiment is applied.

  In the vehicle steering apparatus 10, the steering shaft 14 is divided into an input shaft 14 a that is connected to a steering wheel 12 that is operated by a driver and to which rotation is input, and an intermediate shaft 14 b that transmits rotation to the pinion 40. . The input shaft 14a and the intermediate shaft 14b are connected by a universal joint 16.

  A rack bar 52 extending in the left-right direction of the vehicle, that is, in the vehicle width direction is movably accommodated in the rack housing 50. Both ends of the pinion 40 are rotatably supported by bearings 44. The pinion 40 is meshed with a rack 42 formed on a part of the rack bar 52. When the intermediate shaft 14b connected to the universal joint 16 rotates, the pinion 40 rotates through a gear (not shown). One end of a tie rod 54 is connected to each end of the rack bar 52. The other end of the tie rod 54 is connected to a knuckle arm 56 that supports the left and right steering wheels 58. The knuckle arm 56 rotates with the king pin 60 as a fulcrum. When the steering wheel 12 is operated and the steering shaft 14 rotates, this rotation is converted into a linear motion of the rack bar 52 in the vehicle left-right direction by the pinion 40 and the rack 42. This linear motion is converted into rotation around the kingpin 60 of the knuckle arm 56, and the steered wheels 58 are steered.

FIG. 2 is a diagram schematically showing a configuration around a steered wheel.
The steered wheels 58 are supported by a so-called double joint type suspension device. That is, the knuckle arm 56 is connected to the vehicle body 51 by a pair of upper arms 61 and 62, a pair of lower arms 63 and 64, a tie rod 54, and the like. The upper arms 61 and 62 are respectively extended in the vehicle width direction, connected to a part of the vehicle body 51 via rubber bushes 61a and 62a at their inner ends, and via ball joints 61b and 62b at their outer ends. It is connected to the upper part of the knuckle arm 56. On the other hand, the lower arms 63 and 64 are respectively extended in the vehicle width direction, connected to a part of the vehicle body 51 via rubber bushes 63a and 64a at the respective inner ends, and ball joints 63b and 64b at the respective outer ends. It is connected to the lower part of the knuckle arm 56 via the via. The tie rod 54 extends in the vehicle width direction, and is connected to the intermediate portion of the knuckle arm 56 at the outer end via a ball joint 54a and connected to the rack bar 52 at the inner end via a ball joint 54b. Yes.

  In such a suspension device, the upper arms 61 and 62 and the lower arms 63 and 64 are displaced as indicated by the broken lines in the drawings when the steering is performed from the state indicated by the solid lines in the drawings. That is, the inclination angle of the king pin 60 is changed from a state indicated by a thick dashed line in the drawing to a state indicated by a thin dashed line. As a result, the deflection of the steered wheels 58 is increased, the amount by which the tire contact surface is dragged to the road surface increases, and the axial force (rack axial force) applied to the rack bar 52 by the frictional force also increases. Further, the tire turning angle may change transiently due to the bending of each rubber bush during steering. For this reason, when calculating the tire behavior such as the tire turning angle when turning the vehicle, it is necessary to sufficiently consider the force and moment acting on the tire (collectively referred to as “tire generating force”).

  This tire behavior is usually obtained using commercially available mechanism analysis software, but in general, the force generated between the tire and the road surface is not sufficiently considered in the calculation. For this reason, there is a problem that it is not possible to match the measured values. Therefore, in the present embodiment, as will be described below, highly accurate calculation processing of tire behavior is performed in consideration of tire generation force.

Next, a tire behavior calculation method according to the present embodiment will be described.
FIG. 3 is a block diagram showing an outline of a tire behavior computing device that performs tire behavior computing processing. Each block can be realized in hardware by an element such as a computer CPU and memory, an electric circuit, and a mechanical device. In software, it is realized by a computer program or the like. It is drawn as a functional block to be realized. Therefore, those skilled in the art will understand that these functional blocks can be realized in various forms by a combination of hardware and software.

The tire behavior calculation apparatus according to the present embodiment includes an input unit 102, a behavior data calculation unit 104, a data transfer unit 106, a tire generation force calculation unit 108, and an output unit 110.
The input unit 102 receives various types of input information necessary for behavior calculation of the suspension device mounted on the vehicle. This input information is input by the user. Based on the input information, the behavior data calculation unit 104 executes tire behavior calculation for calculating wheel alignment such as a camber angle and a toe angle of the steered wheels 58 and a displacement of a tire contact point described later. The calculation processing by the behavior data calculation unit 104 is performed by using known mechanism analysis software described later. The data transfer unit 106 transfers a part of the result data calculated by the behavior data calculation unit 104 to the tire generation force calculation unit 108. The tire generation force calculation unit 108 sequentially fetches the transferred result data and calculates the tire generation force. Calculation processing by the tire generation force calculation unit 108 is performed by using spreadsheet software or the like. In the present embodiment, the tire generation force calculated by the tire generation force calculation unit 108 is fed back to the behavior data calculation unit 104. The behavior data calculation unit 104 executes the tire behavior calculation process again using the fed-back tire generation force as an input. In a process in which such feedback calculation processing is repeated, the tire generation force calculation unit 108 monitors the convergence state of the tire behavior. Here, it is determined that the tire behavior has converged when the Ackermann rate has converged within a predetermined range, details of which will be described later. The output unit 110 outputs the calculation result of the behavior data calculation unit 104 such as the calculation result of the converged tire behavior and the calculation result of the tire generation force calculation unit 108 to a screen or the like as necessary.

Next, a specific processing flow according to the tire behavior calculation method will be described.
FIG. 4 is a flowchart showing the flow of the tire behavior calculation process. 5 to 13 are explanatory views specifically showing the process of the tire behavior calculation process. Hereinafter, based on the flowchart of FIG. 4, it demonstrates, referring suitably the explanatory drawing of FIGS.

  First, the behavior data calculation unit 104 calculates the behavior of the suspension device when the vehicle turns based on information input by the user via the input unit 102 (S10). The behavior data calculation unit 104 executes the behavior calculation using commercially available mechanism analysis software (such as Adams / Car dedicated to automobile design / test) such as ADAMS (MSC, USA). As described above, such mechanism analysis software is publicly known and frequently used by those skilled in the art, and thus detailed description thereof is omitted. Here, the position information of the attachment point of the suspension to the body (vehicle body), the front axle weight (FR axle weight) on which the steering wheel 58 is provided, the road surface friction μ, the wheel base, the tire static load radius, and the tire when traveling straight Various information such as information on characteristics and tire characteristics to be described later used for calculating tire generating force are input to the suspension constituent members such as the contact length and contact width of the tire. Each value is unique to the vehicle or wheel, and can be input. The behavior data calculation unit 104 performs a known mechanism calculation process based on the input information, and calculates a tire behavior when the vehicle is turned at a predetermined steering angle. In the present embodiment, the coordinates of the ground contact point J of both the steered wheels 58 (inner and outer wheels), the camber angle θ, the toe when the steered wheels 58 (that is, the tires) are steered to the maximum by steering at very low speeds. The tire behavior including the angle α (equal to the maximum turning angle) is calculated. Although the tire generation force is included in this input information, since there is no calculation result by the tire generation force calculation unit 108 at the beginning of the calculation, a temporary value set in advance as the initial input information is input. The data transfer unit 106 outputs the calculation result as tire behavior data to the tire generation force calculation unit 108 (S12).

  The tire generation force calculation unit 108 calculates the tire generation force for each of the steered wheels 58 based on the received tire behavior data (S14). FIG. 5 shows the tire generation force calculated here. The vertical axis in the figure represents a coordinate L in the length direction with a predetermined position of the vehicle body as a reference (origin), and the horizontal axis represents a coordinate W in a direction perpendicular thereto. In the illustrated example, the behavior of the tires 70 of the two steered wheels 58 during a right turn is shown. In the figure, a thick alternate long and short dash line indicates the traveling direction of the tire 70, and a thick solid line indicates the rolling direction of the tire 70 according to the camber angle. Further, the thick dotted line indicates the direction of the tire 70, and the angle formed by this and the traveling direction of the tire 70 is the slip angle β.

Here, the lateral force Fy and the moment Tz acting on the tire 70 are calculated as the tire generating force.
The lateral force Fy is a vector sum of forces acting in the lateral direction of the tire 70, and is represented by the following formula (1) using the cornering force CF and the canvas last CT.
Fy = CF + CT (1)
However, CF = Cn0 · Fz · β
CT = CS0 · Fz · θ
Here, the normalized cornering power Cn0, the normalized canvas stiffness CS0, and the front wheel weight Fz are values specific to the steering wheel 58 and the vehicle, and are known as tire characteristic information. The camber angle θ is calculated by the behavior data calculation unit 104.

  Further, the slip angle β is calculated using the toe angle α calculated for the two steered wheels 58 by the behavior data calculation unit 104. FIG. 6 shows a method of calculating the slip angle β when it is assumed that the vehicle is turning right. In the figure, the upper side represents the front of the vehicle, and the lower side represents the rear of the vehicle.

  That is, assuming that the inner and outer turning angles of the front wheels when the turning center O of the vehicle is on the rear axle extension are αl and αr, respectively, the slip angles βl and βr of the left and right steering wheels 58 are expressed by the following formula (2). (3).

βl = αl-arctan (Ll / Wl) (2)
βr = αr−arctan (Lr / Wr) (3)
Here, Ll is the distance between the grounding points on the outer ring side, and Lr is the distance between the grounding points on the inner ring side. Wl is the distance in the vehicle width direction between the ground point of the outer wheel side steering wheel 58 and the turning center O, and Wr is the distance in the vehicle width direction between the ground point of the inner wheel side steering wheel 58 and the turning center O. is there. Each value Ll, Lr, Wl, Wr can be calculated geometrically from the configuration of the vehicle, and the cut angles αl, αr can be acquired as toe angles α calculated by the behavior data calculation unit 104. . Therefore, the slip angles βl and βr can also be calculated.

On the other hand, the moment Tz is the sum of rotational moments around the vertical axis of the tire 70, and is expressed by the following formula (4) using the self-aligning torque SAT, camber torque CTQ, and turn slip moment Mts.
Tz = SAT + CTQ + Mts (4)
However, SAT = CF · SATno / Cn0
CTQ = CT · CTQno / CS0
Mts = Mts1 + Mts2
Here, the normalized self-aligning torque SATno and the normalized camber torque CTQno are values specific to the steering wheel 58 and the vehicle, and are known as tire characteristic information. Further, the cornering force CF and the canvas last CT are obtained in the calculation process of the above equation (1).

  On the other hand, Mts1 and Mts2 are moments in the return direction due to the speed difference between the inside and the outside of each tire. Mts1 is a moment for a turn slip caused by a difference in turning radius inside and outside the tire. Mts2 is a moment generated by a difference in tire radius accompanying a change in camber angle inside and outside the tire.

  FIG. 7A is a diagram for explaining the generation of Mts1, and illustrates the case where the vehicle is turning right. On the left side of the figure, the tire generating force applied to the steered wheels 58 is shown. FIG. 7B is a diagram illustrating a method for calculating Mts1. In the same figure, a plan view of the tire 70 is shown.

  As shown in FIG. 7A, for example, when the vehicle turns right about the turning center O, the rotational speed outside the tire 70 is larger than the inside of the tire 70 as theoretically indicated by a thin solid arrow in the figure. Become. For this reason, a force is generated in the tire 70 in a direction that is relatively inwardly cut as indicated by a two-dot chain line arrow, and a moment Mts1 indicated by a thick solid line arrow is generated as a reaction force from the road surface. A slip is generated by the moment Mts1 acting between the tire 70 and the road surface.

  In FIG. 7B, the ground contact surface of the tire 70 when the steered wheel 58 is steered is shown in a semi-elliptical shape. In the figure, the y coordinate is taken in the contact width direction with reference to the center position O1 of the tire 70, and the traveling speed V (y) of the tire 70 at the y coordinate is shown. The centroid position G in the y direction of the contact surface is expressed by the following formula (5), where A is the area of the contact surface and dA is the minute area.

G = ∫ _A y · dA / A (5)
Here, if the turning radius of the tire 70 is R and the turning angular velocity is ω, the traveling speed Vc at the centroid position of the tire 70 is expressed by the following equation (6), and the traveling speed V ( y) is expressed by the following formula (7).

Vc = R · ω (6)
V (y) = (1 + y / R) · Vc (7)
Here, if the turning angular velocity ω is constant (= 1) and the slip ratio for the sum of the longitudinal forces due to slip at each position to be zero is S (y), the following equation (8) is established.

S (y) = (V (y) −Vc) / Vc = y / R (8)
When the braking stiffness per unit width of the tire 70 is kx, the generated force f (y) at each position is expressed by the following formula (9).

f (y) = kx · S (y) = (kx / R) · y (9)
Therefore, the moment Mts1 generated in the tire 70 due to the slip is expressed by the following formula (10).

Mts1 = kx / R · ∫y ² dy (10)
Here, when the braking stiffness kx is represented by the normalized braking stiffness Cxn, the following formula (11) is obtained using the ground contact width b illustrated.

kx = Cxn · Fz / b (11)
Therefore, the moment Mts1 is calculated by the following equation (12).

Mts1 = (Cxn · Fz) / (R · b) · ∫ ² dy (12)
FIG. 8 is a diagram for explaining the generation of Mts2 and the calculation method thereof. In the same figure, a rear view of the tire 70 is shown. In the upper part of the figure, the shape of the ground plane is shown.

  For example, when the vehicle turns right about the turning center O, the rotational speed increases toward the outside of the tire 70 even when the camber angle θ changes. Therefore, a moment Mts2 indicated by a hollow arrow is generated in the tire 70 as a reaction force from the road surface g due to the difference in rotational speed. A slip is generated by the moment Mts2 acting between the tire 70 and the road surface.

  Again, the y coordinate is taken in the contact width direction with reference to the center position O1 of the tire 70, and the traveling speed of the tire 70 at the y coordinate is V (y). Here, the rolling radius at the centroid position according to the camber angle θ of the tire 70 is Rc, the rolling radius Rc (y) at the position y, the rotational angular velocity is ωc, and the camber angle θ is changed at the centroid position. Let the tire radius be rc, and the tire radius at position y be rc (y). At this time, since rc (y) is proportional to Rc (y), the traveling speed Vc at the centroid position of the tire 70 is expressed by the following equation (13), and the traveling speed V (y at each position in the y direction is ) Is represented by the following formula (14).

Vc = rc · ωc (13)
V (y) = (1 + y / Rc) · Vc (14)
Here, assuming that the rotational angular velocity ωc of the tire 70 is constant (= 1) and the slip ratio at which the sum of the longitudinal forces due to slip at each position becomes zero is S (y), the following equation (15) is established. To do.

S (y) = (V (y) −Vc) / Vc = y / Rc (15)
When the braking stiffness per unit width of the tire 70 is kx, the generated force f (y) at each position is expressed by the following formula (16).

f (y) = kx · S (y) = (kx / Rc) · y (16)
Therefore, the moment Mts2 generated in the tire 70 due to the slip is expressed by the following formula (17).

Mts2 = kx / R · ∫y ² dy (17)
Here, when the braking stiffness kx is expressed by the normalized braking stiffness Cxn, the above equation (11) already described is obtained, so the moment Mts2 is calculated by the following equation (18).

Mts2 = (Cxn · Fz) / (Rc · b) · ∫y ² dy (18)
Note that the centroid position G of the above-described ground plane can be calculated as follows, for example. 9-11 is explanatory drawing showing the example of a calculation of the centroid position of a ground-contact plane.
As shown in FIG. 9, assuming a cylindrical model of the tire 70, a tire coordinate system is set for a surface facing the road surface. That is, as shown in a plan view of the tire in FIG. 9A, a coordinate system is set in which the X axis is set in the direction of the contact length L and the Y axis is set in the direction of the contact width W with the center of the contact point of the tire 70 as the origin. Then, the opposing surface is divided into a large number of minute elements by dividing each of the opposing surfaces at intervals of 1 to 2 mm in each axial direction. As shown in the rear view of the tire in FIG. 9B, the tire 70 is loaded with a vertical load associated with the vehicle weight or the like, so that the static load radius r (from the tire axial center to the road surface). The distance) is smaller than the no-load radius R when there is no load. The no-load radius R can be calculated from the following equation (19) based on the static load radius r and the contact length L when traveling straight.

R = L / 2 / cos (atan (2.L / r))) (19)
Subsequently, the ground contact range of the tire 70 corresponding to the change in the camber angle when the vehicle turns is calculated. In FIG. 10, a plan view of the tire outline is shown in the upper left stage, a rear view is shown in the lower left stage, and a side view is shown in the lower right stage. When the tire 70 is steered from the straight traveling direction, the state shown by the dotted line in the rear view changes to the state shown by the solid line. That is, the camber angle θ changes, and the shape of the ground contact surface of the tire 70 changes accordingly. The ground contact width of the tire 70 changes as shown by a thick line in the rear view, and the contact length also changes as shown by a thick line in the side view. The ground contact range of the tire 70 can be obtained from the geometric shape of the tire 70 accompanying such a change in the camber angle θ.

  When the camber angle θ of the tire 70 changes as shown in the rear view on the left side of FIG. 11, the distance m from the rotation axis of the tire 70 to the road surface g indicated by the alternate long and short dash line is expressed by the following equation (20). Become. Here, w represents the half width of the tire (1/2 of the width), R represents the above-described no-load radius R, and r represents the tire static load radius.

m = (r + w · sinθ) / cosθ (20)
For this reason, in the tire 70, the contact length L = 0 at a location where m> R. On the other hand, the contact length L is expressed by the following formula (21) at a location where m ≦ R.
L = 2 · m / (tan (asin (m / R))) (21)
In this way, the contact length L is calculated at intervals of the minute elements along the contact width direction of the tire 70, that is, the y direction. At this time, the centroid position G can be calculated as the following equation (22).

G = ∫ _A y · dA / A = Σ (l · y) / Σl (22)
When the lateral force Fy and the moment Tz as the tire generating force are calculated as described above, the tire generating force calculation unit 108 calculates the Ackermann rate X at that time and determines the convergence (S16). That is, for example, when a force is applied to the tire 70 with the steering turned to the maximum, the cutting angle changes transiently due to, for example, the deflection of the rubber bush at the end of each arm. When this turning angle changes, the tire generating force changes, and the force applied to the tire 70 gradually balances by repeating the changing of the cutting angle due to the change in the tire generating force. As a result of this balance, the change in the turning angle and the change in the tire generating force finally converge, so the Ackermann rate X is calculated as an index for estimating the convergence state.

  Here, the Ackermann rate X [%] is defined as the ratio of the design inner / outer wheel break angle difference to the theoretical inner / outer wheel cut angle difference when the turning center of the vehicle is on the extension of the rear axle. Yes. However, the tire turning angle is assumed to be equal to the toe angle.

  Referring to FIG. 6, an ideal outer wheel turning angle θa (= αl) that the vehicle can turn without generating a slip angle β (βl, βr) is expressed by the following equation (23).

θa = arctan (L1 / (C + W)) (23)
However, C = Lr / tanαr
At this time, the Ackermann rate X [%] is expressed by the following formula (24).

X = {(| αr | − | αl |) / (| αr | − | θa |)} × 100 (24)
If the difference (change margin) between the previously calculated Ackermann rate X and the currently calculated Ackermann rate X is within a preset convergence determination value (Y in S16), the tire generation force calculation unit 108 converges. As a result, the calculation processing of the tire generation force is terminated. For example, an appropriate value can be appropriately set for the convergence determination value by experiment or the like, for example, between 0.1% and 1.0%. On the other hand, if the difference is not within the convergence determination value (N in S16), the process returns to S10 because the Ackermann rate X is not yet converged. In this case, the behavior data calculation unit 104 performs the tire behavior calculation process again using the tire generation force calculated this time by the tire generation force calculation unit 108 as an input value.

  In this way, the processing from S10 to S16 is repeated, and when it is determined in S16 that the Ackermann rate X has converged, the output unit 110 outputs the behavior data of the requested tire behavior on the screen (S18). FIG. 12 shows a calculation process of the tire generation force calculation unit 108 in a spreadsheet format. FIG. 3A shows tire behavior input data input from the behavior data calculation unit 104 to the tire generation force calculation unit 108 via the data transfer unit 106. FIG. 5B shows tire generation force calculation data calculated by the tire generation force calculation unit 108. In FIG. 13, the change in the Ackermann rate X in the calculation process is represented by the number of calculations as a parameter.

  These figures show an example in which the Ackermann rate X converges to about 77% after 13 calculations (case 13 in the figure). In this example, the state when the steering is turned to the maximum is shown. For this reason, for example, the toe angle α at the time of convergence of the Ackermann rate X can be output as the maximum cutting angle.

  As described above, in the present embodiment, the tire generation force and the tire behavior are repeatedly calculated to calculate the tire behavior such as the maximum turning angle, and the calculation result of the tire behavior is determined with the convergence of the Ackermann rate. . In this way, tire generation force is considered in the calculation of the tire behavior, and a stable calculation result based on the convergence value is obtained, so that the consistency with the actually measured value is also improved.

  The present invention is not limited to the above-described embodiments, and various modifications such as design changes can be added to the embodiments based on the knowledge of those skilled in the art. The described embodiments can also be included in the scope of the present invention.

In the above-described embodiment, the example in which the cutting angle of the tire 70 is calculated as the tire behavior is shown. However, the technical idea can be applied to the calculation of the camber angle, the tire displacement, and other tire behaviors. is there.
Although the rack and pinion type steering device has been described in the above embodiment, the present invention may be applied to a recirculating ball type steering device.

  In the embodiment described above, an example in which the rack axial force is calculated for a vehicle on which a so-called double joint type suspension device is mounted has been shown. In the modification, the tire behavior calculation method of the present invention may be applied to a vehicle equipped with a so-called single joint type or other type of suspension device.

1 is a diagram illustrating a schematic configuration of a vehicle steering apparatus to which a tire behavior calculation method according to an embodiment is applied. It is a figure which shows roughly the structure of the periphery of a steering wheel. It is a block diagram which shows the outline of the tire behavior calculating apparatus which performs a tire behavior calculating process. It is a flowchart showing the flow of a tire behavior calculation process. It is explanatory drawing which represents specifically the process of a tire behavior calculation process. It is explanatory drawing which represents specifically the process of a tire behavior calculation process. It is explanatory drawing which represents specifically the process of a tire behavior calculation process. It is explanatory drawing which represents specifically the process of a tire behavior calculation process. It is explanatory drawing which represents specifically the process of a tire behavior calculation process. It is explanatory drawing which represents specifically the process of a tire behavior calculation process. It is explanatory drawing which represents specifically the process of a tire behavior calculation process. It is explanatory drawing which represents specifically the process of a tire behavior calculation process. It is explanatory drawing which represents specifically the process of a tire behavior calculation process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Vehicle steering device, 12 Steering wheel, 14 Steering shaft, 40 Pinion, 42 Rack, 51 Car body, 52 Rack bar, 54 Tie rod, 58 Steering wheel, 60 Kingpin, 61,62 Upper arm, 63,64 Lower arm, 70 Tire, 102 An input unit, 104 behavior data calculation unit, 106 data transfer unit, 108 tire generation force calculation unit, 110 output unit.

Claims (5)

In the tire behavior calculation method for calculating the tire behavior when turning the vehicle,
A tire behavior initial value calculating step for calculating tire behavior based on the initial input information;
A tire generation force calculation step for calculating tire generation force from the calculated tire behavior;
A tire behavior calculation step for calculating tire behavior based on the calculated tire generation force;
In the process of repeatedly executing the tire generation force calculation step and the tire behavior calculation step, a convergence determination step for determining whether the tire behavior has converged,
When it is determined that the tire behavior has converged, a calculation value output step of outputting the convergence value as a calculation result of the tire behavior;
A tire behavior calculation method comprising: The tire behavior calculation step includes a step of calculating a change in camber angle and toe angle of a steered wheel when the vehicle turns as the tire behavior,
The tire generation force calculation step includes a step of calculating a lateral force acting on the tire as the tire generation force, and a step of calculating a moment acting on the tire.
The tire behavior calculation method according to claim 1.   The convergence determination step calculates an Ackermann rate from the calculated tire behavior, and determines that the tire behavior has converged when the change amount of the Ackermann rate is within a preset convergence determination value. The tire behavior calculation method according to claim 2.   The tire behavior according to claim 2 or 3, wherein the tire generation force calculation step performs calculation processing including, as the moment, a moment generated by a difference in turning radius in each part of the ground contact surface of the tire. Calculation method.   The tire generation force calculation step performs calculation processing including, as the moment, a moment generated due to a difference in tire radius at each portion of the contact surface with a change in the camber angle of the tire. The tire behavior calculation method according to any one of?

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