A method for matching camber and toe angles of a vehicle wheel

Abstract

The application discloses a matching method for camber and toe angle of a vehicle wheel, which comprises the influence of ground vertical reaction force on tire cornering characteristics when the wheel is cambered. When the wheel is cambered, an equivalent camber cornering force is applied to the tire in the direction opposite to the camber direction of the wheel. When the wheel is straightly driven, the wheel is cambered, but the tire cornering angle is zero because the wheel is constrained by the vehicle body. When the wheel is straightly driven and the camber angle is zero, the ground generates a lateral force on the wheel. When the toe angle is equal to the tire cornering angle caused by the camber, the lateral force can be eliminated. The ideal matching relationship between the camber angle and the toe angle of the wheel is derived based on the influence of the wheel camber on the tire cornering characteristics. The formula is simple in form, convenient to use, and contains various factors influencing the correct matching relationship between the camber angle and the toe angle of the wheel, and is more scientific and reasonable.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automobile wheel positioning technology, in particular to a matching method of camber angle and toe angle of automobile wheel. BACKGROUND

[0002] The camber angle and toe angle of automobile wheel are two important parameters in front wheel positioning. The toe angle is a parameter designed to reasonably match the camber angle to overcome the adverse effects of the camber angle and ensure the pure rolling of automobile wheel. If the camber angle and toe angle are not reasonably matched, the side slip of automobile wheel will be increased, which will cause abnormal wear of tire. The excessive side slip of automobile wheel will increase the driving resistance of automobile, which will have adverse effects on the power performance, fuel economy and braking performance of automobile. The side slip of front wheel has a power function relationship with the service life of tire, and the increase of the side slip will aggravate the wear of tire and cause uneven wear, thereby reducing the service life of tire. Reasonable matching of camber angle and toe angle can reduce the lateral force acting on the wheel and improve the stability of steering and driving of automobile.

[0003] Many scholars have made extensive and in-depth research on the matching relationship between camber angle and toe angle. Some scholars have theoretically analyzed the principle of side slip of automobile wheel caused by camber angle and toe angle and the correct matching. Many scholars have analyzed the geometric relationship of the motion trajectory of front wheel under the combined action of camber angle and toe angle. Through prior art retrieval, it is found that the Chinese invention patent with the publication number CN 104742968 A discloses a matching method of toe angle and camber angle of double front axle commercial vehicle. Under the premise that the lateral forces generated by camber angle and toe angle are offset, the matching formula of camber angle and toe angle is derived, and the formula is verified through side slip test of actual vehicle. The scheme close to the present application is to provide a formula for reasonably matching the camber angle and toe angle of automobile wheel. The above-mentioned related problems exist in the patent technology, and therefore, an improved matching method of camber angle and toe angle of automobile wheel is needed to solve the above-mentioned problems in the prior art. SUMMARY

[0004] The present application aims to provide a matching method of camber angle and toe angle of automobile wheel, which is simple in formula form, convenient to use, contains various factors affecting the correct matching relationship between camber angle and toe angle, and is more scientific and reasonable, so as to solve the problems in the background technology.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a matching method of camber angle and toe angle of automobile wheel: when the tire is cambered, the vertical ground reaction force F z of the tire is affected by the side slip characteristics of the tire, and a vertical plane l c passing through the center of the tire is formed, F z is the vertical force of the tire, F c ·sinγ is the component of F z in the lc If the plane does not tilt, the ground l will necessarily exert a force F on the tire in the same direction as the tire's tilt. y And F y In l c Component of the plane and F z In l c The components of the force in the plane are equal in magnitude and opposite in direction, and their relationship is as follows:

[0006] F y ·cosγ=-F z ·sinγ (1)

[0007] That is, F y =-F z ·tanγ (2)

[0008] Due to the influence of tire body roll deformation, the camber angle in the above formula should be replaced by the effective roll angle, and the relationship between the two is as follows:

[0009] γ e =γ-γ c (3)

[0010] In the formula, γ e γ is the effective roll angle; γ is the camber angle; γ c This is the local tire body roll angle, which is smaller when the normal wheel camber angle is used.

[0011] Preferably, when the wheel roll affects the lateral slip characteristics, the tire carcass deformation and the camber angle γ should be the effective roll angle γ. e Instead, formula F y =-F z ·tanγ rewritten as

[0012] F y =-F z ·tanγ e (4)

[0013] The effect of the vertical ground reaction force on the wheel's lateral slip characteristics when the wheel cambers outward is equivalent to a force exerted by the ground on the wheel in the opposite direction to the wheel's lateral slip. This force exerted by the ground on the wheel in the opposite direction to the wheel's lateral slip is equivalent to F. y Let F be a force of equal magnitude but opposite direction exerted by the ground on the wheel, in the opposite direction to the wheel's tilt. ye And the force exerted by the ground on the wheel in the opposite direction to the wheel's lateral tilt is defined as the equivalent camber lateral force. From equation (5), it can be seen that F ye The expression is:

[0014] F ye =F z ·tanγ e (5)

[0015] The tire of the vehicle is not subjected to lateral force, then the tire will certainly be subjected to side slip when the tire is cambered, let the side slip angle caused by the camber be α0, the side slip of the tire on the ground l can be converted to l c The analysis is made in the plane direction, which is equivalent to analyzing the side slip characteristics of the tire with zero side slip angle, let the side slip angle in the plane direction be α0', the relationship between α0' and α0 is: c

[0016] tanα0' = tanα0 · cosγ e (6)

[0017] When α0 is small, then:

[0018] α0' = α0 · cosγ e (7)

[0019] In the plane direction of l c , it is:

[0020] F z · sinγ e = k α α0 · cosγ e (8)

[0021] In the formula, k α is the side slip stiffness in the plane direction of l z c, the load of the tire in the direction perpendicular to the plane direction of l e c is F α · cosγ

[0022]

[0023] Preferably, the tire of the vehicle is cambered, the cambered tire is simultaneously subjected to lateral force, let the lateral force be F Y , the side slip angle of the cambered tire subjected to the lateral force is α y , in the plane direction of l c , it is:

[0024] F Y · cosγ e = k α α y · cosγ e (10)

[0025] That is:

[0026] In the formula, the side slip stiffness of the tire in the direction of the road surface is also k α , the actual side slip angle of the tire is α

[0027] ​

[0028] When the tire small side angle is obtained:

[0029] F Y +F z ·tanγ e =k α α (13)

[0030] Preferably, the wheel only has camber and no toe and straight driving, the side angle of the wheel is zero, and formula (13) can be obtained:

[0031] F Y =-F z ·tanγ e

[0032] When the wheel only has camber and the toe angle is zero and straight driving, the ground will generate a lateral force on the wheel, in order to eliminate the lateral force to the wheel A suitable toe angle is provided, and formula (13) can be obtained when the lateral force is zero F z ·tanγ e =k α α, the toe angle θ is exactly equal to the size of the tire side angle α caused by the camber of the wheel, and the relationship between the camber angle γ of the wheel and the toe angle θ is:

[0033]

[0034] The return torque caused by the camber of the wheel will reduce the toe angle, and the actual toe angle is slightly larger than the toe angle calculated by formula (15).

[0035] Preferably, a simulation of a matching method of a camber angle and a toe angle of a wheel comprises the following steps:

[0036] Step 1, a tire side deflection characteristic simulation model is established by AMEsim;

[0037] Step 2, the wheel only has camber and no toe, the side deflection angle of the tire is set to zero, and when the small camber angle is obtained, the equivalent camber side deflection force and the actual side deflection force are completely equal, with the increase of the camber angle, the equivalent side deflection force calculation value is larger, and the error is larger.

[0038] Step 3, several fixed camber angles of the wheel are set, the corresponding side deflection angle when the side deflection force is zero is obtained, and the calculated side deflection angle is compared.

[0039] Compared with the prior art, the beneficial effects of the present application are:

[0040] Based on the influence of wheel camber on tire lateral slip characteristics, this invention derives and proves the ideal matching relationship between wheel camber angle and toe angle. The formula is simple in form and easy to use, and includes various factors that affect the correct matching relationship between wheel camber angle and toe angle, making it more scientific and reasonable. Attached Figure Description

[0041] Fig. 1 This is a schematic diagram showing the relationship between the reverse value of the lateral force and the equivalent outward tilt lateral force when the lateral deflection angle is zero according to the present invention.

[0042] Fig. 2 This is a schematic diagram showing the relationship between the lateral force and the lateral slip angle under different lateral slip angles according to the present invention;

[0043] Fig. 3 This is a schematic diagram illustrating the principle of lateral plane transformation in this invention. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Please see Figs. 1-3 The present invention provides a technical solution: a method that considers the vertical ground reaction force F when the tire tilts outward. z To assess the effect of tire lateral slip characteristics, construct a plane perpendicular to the tire's midline. c F z In l c The magnitude of the component force in the plane is F. z ·sinγ, to make the tire in l c If the plane does not tilt, the ground l will necessarily exert a force F on the tire in the same direction as the tire's tilt. y And F y In l c Component of the plane and F z In l c The components of the force in the plane are equal in magnitude and opposite in direction; their relationship is as follows:

[0046] F y ·cosγ=-F z ·sinγ (1)

[0047] Right now

[0048] F y =-F z ·tanγ (2)

[0049] If the effect of the tire side deformation is considered, the camber angle in the above equation should be replaced by the effective side angle, and the relationship between them is

[0050] γ e = γ - γ c (3)

[0051] where γ e is the effective side angle; γ is the camber angle; and γ c is the local tire side deformation angle, which is small when the normal wheel camber angle is used.

[0052] When the effect of the tire side deformation is considered in the study of the effect of the wheel side deformation on the cornering characteristics, the γ in the above equation should be replaced by γ e , and the equation F y = - F z • tan γ is rewritten as

[0053] F y = - F z • tan γ e (4)

[0054] Therefore, the effect of the ground vertical reaction force on the tire cornering characteristics when the wheel is cambered is equivalent to that of a force acting on the tire in the opposite direction of the tire side deformation, which is equal in magnitude and opposite in direction to F y , and the force acting on the tire in the opposite direction of the tire side deformation is defined as the equivalent camber cornering force F ye . The expression of F y is obtained from equation F z = - F e • tan γ ye .

[0055] F ye = F z • tan γ e (5)

[0056] However, it should be noted that F ye is not a real force that can be drawn on a force diagram, that is, the vertical reaction force of the ground on the tire causes the tire to deform laterally in the same way as a force F ye acting on the tire in the opposite direction of the tire side deformation.

[0057] Taking a single tire as the research object, assuming that the tire tread is not subjected to a lateral force, the tire will certainly corner when it is cambered, and the cornering angle caused by the camber is assumed to be α0. The cornering of the tire on the ground l can be converted to the l c plane for analysis, which is equivalent to analyzing the cornering characteristics of a tire with zero side deformation angle, and the cornering angle caused by the camber is assumed to be α0. cThe side slip angle in the plane direction is α0', and it is known that α0' and α0 are related as

[0058] tan α0' = tan α0 · cos γ e (6)

[0059] When α0 is small, there is

[0060] α0' = α0 · cos γ e (7)

[0061] In the l c plane direction, there is

[0062] F z · sin γ e = k α α0 · cos γ e (8)

[0063] In the formula, k α is the side slip stiffness in the l c plane direction, and at this time, the load of the tire in the vertical l c plane direction is F z · cos γ e , so k α changes with γ, and generally is inversely proportional, from the formula F z · sin γ e = k α α0 · cos γ e , we have:

[0064]

[0065] If the outer inclined tire surface is simultaneously subjected to a lateral force, let it be F Y The side slip angle generated by the outer inclined tire surface subjected to the lateral force is α y , and in the l c plane direction, there is

[0066] F Y · cos γ e = k α α y · cos γ e (10)

[0067] That is,

[0068]

[0069] From the formula , it is known that the side slip stiffness of the tire in the road surface direction is also k α , and the actual side slip angle of the tire is α, and it is:

[0070]

[0071] Then, when the tire side slip angle is small (less than 4°-5°), the following relationship is obtained:

[0072] F Y +F z ·tanγ e =k α α (13)

[0073] When the wheel has only camber and no toe and the vehicle is driving straight, the wheel has camber but the side slip angle is zero because the wheel is constrained by the vehicle body. From equation F Y +F z ·tanγ e =k α α, it can be seen that F Y =-F z ·tanγ e When the wheel has only camber and no toe and the vehicle is driving straight, the ground will generate a lateral force on the wheel. In order to eliminate this lateral force, a suitable toe angle can be set for the wheel. From equation F Y +F z ·tanγ e =k α α, it can be seen that F z ·tanγ e =k α α when the lateral force is zero. At this time, the toe angle θ should be exactly equal to the size of the tire side slip angle α caused by the camber of the wheel. Therefore, in the ideal case, the relationship between the camber angle γ of the wheel and the toe angle θ is:

[0074]

[0075] The return torque caused by the camber of the wheel will reduce the toe angle. Therefore, the actual toe angle should be slightly larger than the toe angle calculated by equation The relationship between the camber angle γ of the wheel and the toe angle θ is:

[0076]

[0077] In order to verify the correctness of the above theoretical analysis, a tire side slip characteristic simulation model is established by AMEsim in this paper, and the Pacejka2002 tire model is selected.

[0078] Comparison of tire side slip force and equivalent camber side slip force when the tire has only camber and no toe and the vehicle is driving straight. The equivalent camber side slip force in the figure is calculated by equation F ye =F z ·tanγ e , and the tire side slip force is obtained by simulation. When simulating, the side slip angle of the tire is set to zero, and FY +F z ·tanγ e =k α α indicates that F should exist. z ·tanγ e =-F Y To compare the side camber force in the diagram, at small camber angles, the equivalent camber side camber force and the actual side camber force are exactly equal. As the camber angle increases, there is a certain error between the two. The reason for this error is that the effective camber angle was used instead of the actual camber angle in the calculation, and the calculated value of the equivalent side camber force is too large. The larger the camber angle, the greater the error. Therefore, if the influence of tire carcass roll deformation is considered, the equivalent camber side camber force in the relationship between the side camber force and the equivalent camber side camber force when the camber angle is zero will be closer to the side camber force inverse value. Radial tires have softer sidewalls than ordinary bias-ply tires. Under the same working conditions, radial tires produce larger local tire carcass roll deformation and have a smaller effective camber angle, so the equivalent camber side camber force of radial tires is smaller.

[0079] By setting several fixed wheel camber angles and observing the relationship between lateral force and lateral slip angle, simulations can be used to determine the lateral slip angle corresponding to zero lateral force, and this can be compared with the formula F. Y +F z ·tanγ e =k α Compare the sideslip angle calculated by α with γ e Substituting γ, the results are shown in Table 1. It is found that the simulated values ​​and the theoretical calculation values ​​are very close. If the influence of tire roll deformation is considered, the values ​​will be even closer. The inverse value of the theoretically calculated slip angle in the table is the ideal toe angle corresponding to a certain wheel camber angle. Through simulation verification, the correctness of the theoretical analysis conclusions is proved.

[0080] Table 1 Comparison of theoretically calculated and simulated sideslip angles

[0081]

[0082]

[0083] Based on the influence of wheel camber on tire lateral slip characteristics, this invention derives and proves the ideal matching relationship between wheel camber angle and toe angle. The formula is simple in form and easy to use, and includes various factors that affect the correct matching relationship between wheel camber angle and toe angle, making it more scientific and reasonable.

[0084] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for matching wheel camber angle and toe angle, characterized in that: Including the vertical ground reaction force F when the tire leans outward. z To assess the effect of tire lateral slip characteristics, construct a plane perpendicular to the tire's midline. c F z In l c The magnitude of the component force in the plane is To make the tires in l c If the plane does not tilt, the ground l will necessarily exert a force F on the tire in the same direction as the tire's tilt. y And F y In l c Component of the plane and F z In l c The components of the force in the plane are equal in magnitude and opposite in direction, and their relationship is as follows: （1） Right now (2) The effect of tire body roll deformation, in the above formula, the camber angle is replaced by the effective roll angle, and the relationship between the two is: （3） In the formula, Effective roll angle; Outward tilt angle; The camber angle is the localized tire body roll deformation angle, which is relatively small when using the normal wheel camber angle; when the wheel roll affects the lateral slip characteristics, the tire body deforms, and the camber angle... Use effective roll angle Instead, the （4） The effect of the vertical ground reaction force on the wheel's lateral slip characteristics when the wheel cambers outward is equivalent to a force exerted by the ground on the wheel in the opposite direction to the wheel's lateral slip. This force exerted by the ground on the wheel in the opposite direction to the wheel's lateral slip is equivalent to F. y Let the forces acting on the wheel be equal in magnitude and opposite in direction, and let the forces acting on the wheel be opposite in direction to the wheel's tilt. And the force exerted by the ground on the wheel in the opposite direction to the wheel's lateral tilt is defined as the equivalent camber lateral force. From equation (4), it can be seen that... The expression is: （5） If the tire tread of the wheel is not subjected to lateral force, then lateral slip will definitely occur when the tire cambers outward. Let the slip angle caused by camber be θ. When the tire deflects laterally on the ground, it can be converted to l. c Analyzing in the planar direction involves analyzing the lateral slip characteristics of a tire with zero camber. Let l be an example. c The sideslip angle in the planar direction is The and The relationship is: （6） when When smaller: （7） In l c The planar direction is: （8） In the formula Let be the lateral stiffness along the lc plane direction, and the load on the tire in the direction perpendicular to the lc plane is . , Follow It changes with the change, and from equation (9) we get: （9）； The tire tread of the vehicle is sloping outwards, and the sloping tire tread is simultaneously subjected to a lateral force, denoted as F. Y The camber angle produced by the outward-facing wheel subjected to lateral force is... , in l c In the planar direction: （10） Right now (11) Among them: the lateral stiffness of the tire in the direction of road surface is also... The actual slip angle of the tire is for: （12） When the tire has a small sideslip angle: （13）； The wheel has only a camber angle and no toe-in, and travels in a straight line. The wheel's slip angle is zero. From equation (13), we can obtain: When a wheel has only a camber angle and a zero toe angle and is traveling in a straight line, the ground will exert a lateral force on the wheel. To eliminate this lateral force, a suitable toe angle is set for the wheel. From equation (13), it can be seen that when the lateral force is zero, we have: , toe angle Exactly equal to the tire slip angle caused by wheel camber The size of the wheel camber angle With toe angle The relation is: （14） The camber of the wheel will reduce the toe angle, and the actual toe angle is slightly larger than the toe angle calculated by formula (14).

2. The simulation method for implementing the wheel camber angle and toe angle matching method as described in claim 1 includes the following steps: Step 1: Establish a simulation model of tire side slip characteristics using AMEsim; Step 2: The wheel has only camber and no toe-in. Assuming the tire's lateral deflection angle is zero, at a small camber angle, the equivalent camber lateral deflection force and the actual lateral deflection force are exactly equal. As the camber angle increases, the calculated value of the equivalent lateral deflection force is too large, and the larger the camber angle, the greater the error. Step 3: Set several fixed wheel camber angles, obtain the slip angle corresponding to zero lateral force, and compare it with the calculated slip angle.

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