Method for calculating axle load of each axle during braking of 8*4 vehicle

Abstract

A method for calculating the axle load of each axle during braking of an 8 * 4 vehicle belongs to the field of vehicle design, and comprises the following steps: acquiring the mass of the whole vehicle, the structural parameters of the vehicle and the leaf spring stiffness parameter of each axle; each shaft plate spring set at the reference horizontal position of the frame has an initial compression amount, and the deformation amount of each shaft plate spring is obtained by adding the initial compression amount and the deformation amount of the actual position of the frame relative to the reference horizontal position; carrying out force and moment balance analysis on the frame, unifying the initial compression coefficient according to the real axle load data, and calculating to obtain the axle load of each axle; axle load transfer during braking is added, the axle load transfer amount is determined according to moment balance, axle load distribution during braking is obtained through calculation, and the initial compression coefficient of the plate spring is introduced to the reference horizontal position, so that calculation of the supporting force of the plate spring is more accurate. And when the displacement of each axle of the frame relative to the horizontal position is used as the total deformation of the suspension to calculate the axle load of each axle, the calculation result is inaccurate.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle design, and particularly to a method for calculating the axle loads of each axle during braking of an 8×4 vehicle. Background Art

[0002] During the vehicle design process, the vehicle axle load is a key factor. The vehicle axle load is an important basis for checking the strength of the vehicle frame and is also an essential basic parameter for carrying out safety and comfort analyses. In particular, the dynamic change of the axle load during braking plays a decisive role in the braking safety of the vehicle and is directly related to driving safety.

[0003] Currently, for the calculation of the axle loads of vehicles with more than two axles, the main idea is to regard the displacement of the actual positions of each axle of the vehicle frame relative to the horizontal position as the total deformation of the suspension, and use this as a starting point to calculate the force borne by each axle. After obtaining the force data of each axle, the axle loads of each axle are further calculated based on the force and moment balance equations.

[0004] However, in actual situations, there may already be different deformation amounts in the suspensions of each axle when the vehicle frame is in the horizontal position. When the existing vehicle axle load calculation method simply uses the displacement of each axle of the vehicle frame relative to the horizontal position as the total deformation of the suspension to calculate the axle loads of each axle, since the existing suspension deformation amount when the vehicle frame is horizontal is not taken into consideration, the data basis on which the calculation depends will have deviations, resulting in relatively large deviations in the calculated results. Summary of the Invention

[0005] To solve the technical problem in the above-mentioned background art that when the existing vehicle axle load calculation method simply uses the displacement of each axle of the vehicle frame relative to the horizontal position as the total deformation of the suspension to calculate the axle loads of each axle, and the existing suspension deformation amount when the vehicle frame is horizontal is not taken into consideration, resulting in relatively large deviations in the calculation results, the present invention provides a method for calculating the axle loads of each axle during braking of an 8×4 vehicle.

[0006] The technical solution of the present invention is as follows: The present invention provides a method for calculating the axle loads of each axle during braking of an 8×4 vehicle, including: Obtaining the vehicle's total mass, the vehicle's structural parameters, and the leaf spring stiffness parameters of each axle, providing reliable data support for subsequent calculations, and making the calculation results closer to the axle load conditions under the actual operating state of the vehicle; Setting an initial compression amount for the leaf springs of each axle at the reference horizontal position of the vehicle frame, adding the deformation amount of the vehicle frame's actual position relative to the reference horizontal position to obtain the deformation amount of the leaf springs of each axle. Introducing an initial compression coefficient of the leaf spring at the reference horizontal position, calculating the deformation amount of the leaf spring by setting the initial compression amount and combining with the actual deformation amount, making up for the defect that the traditional calculation method does not consider the existing suspension deformation amount when the vehicle frame is horizontal, making the calculated deformation amount of the leaf spring more in line with the actual situation, and thus improving the accuracy of the axle load calculation. Perform a force and moment balance analysis on the vehicle frame. At the same time, unify the initial compression coefficient according to the actual axle load data of the vehicle, calculate the axle load of each axle. The force and moment balance analysis combined with the actual axle load data of the vehicle comprehensively considers the actual force situation of the vehicle, unifies the initial compression coefficient to further optimize the calculation process, ensures that the calculated axle load of each axle is more accurate, and provides a more reliable basis for the vehicle's structural design, component selection, etc.; Add the axle load transfer during braking, determine the axle load transfer amount according to the moment balance, and calculate the axle load distribution during braking. Considering the axle load transfer during braking makes the axle load calculation more comprehensively reflect the actual situation of the vehicle under braking conditions, helps to accurately evaluate the vehicle's braking performance, provides key data for the design and optimization of the vehicle's braking system, and improves the braking safety of the vehicle.

[0007] Preferably, the structural parameters of the vehicle include the wheelbase between the first and second axles, the wheelbase between the second axle and the equivalent rear axle, and the distance from the center of mass to the first axle, which can perform vehicle mechanical analysis and axle load calculation more accurately, make the calculation model more in line with the actual structure of the vehicle, improve the credibility and practicality of the calculation results, and facilitate in-depth research and optimization of vehicle performance based on these parameters.

[0008] Preferably, during braking, the axle load of each axle of the vehicle is:

[0009]

[0010]

[0011] is the unsprung mass of each axle; is the force exerted by the leaf spring of each axle on the vehicle frame. Incorporating the leaf spring force and unsprung mass into the calculation makes the axle load calculation more comprehensive and accurate, provides a standardized calculation method for axle load analysis of the vehicle under different working conditions, and is convenient for engineering applications and actual operations.

[0012] Preferably, the force exerted by the leaf spring of each axle on the vehicle frame is:

[0013]

[0014]

[0015] is the initial compression of the corresponding leaf spring of each axle; is the deformation of the leaf spring of each axle; is the leaf spring stiffness corresponding to each axis, which clarifies the relationship between the leaf spring force, leaf spring stiffness, deformation amount, and initial compression amount, provides a clear basis for calculating the force of the leaf spring on the vehicle frame, and makes the entire axle load calculation system more complete and accurate.

[0016] Preferably, the initial compression amount of the leaf spring , takes 0, takes 3 - 5, which avoids calculation differences caused by unclear values of the initial compression amount, helps different personnel perform axle load calculations according to a unified standard, improves the consistency and reliability of calculation results, and reduces the error between the calculated axle load data and the measured axle load data.

[0017] Preferably, by analyzing the force balance and moment balance of the vehicle frame:

[0018]

[0019] is the total supporting force of all leaf springs. By establishing force balance and moment balance equations, the force situation of the vehicle frame is comprehensively considered, and the leaf spring forces of each axis are related to the vehicle weight, braking overturning moment, etc., providing a theoretical basis for accurately calculating the axle load and making the calculation results more in line with the actual mechanical principles of the vehicle.

[0020] Preferably, during braking, the overturning moment exerted by the ground on the vehicle is:

[0021] is the braking deceleration; is the height of the sprung mass center; is the vehicle weight. Incorporating key factors such as braking deceleration, height of the sprung mass center, and vehicle weight makes the calculation of axle load transfer during braking more accurate, thereby more precisely calculating the axle load distribution during braking and providing an important calculation basis for studying vehicle braking performance.

[0022] Preferably, there is a geometric relationship between the compression amounts of the leaf springs of each axis:

[0023] is the wheelbase between the first and second axles; is the wheelbase between the second and third axles; is the distance from the center of mass to the first axle. Using the geometric relationship between axles to establish the connection between the compression amounts of leaf springs further improves the calculation system, enables the solution of other leaf spring compression amounts when some parameters are known, improves the accuracy and convenience of calculation, and enhances the practicality of the calculation method.

[0024] Preferably, Take the curb weight; the unsprung weight Both are 0, which simplifies the calculation process, reduces the complexity of the calculation, does not have a great impact on the accuracy of the calculation result, facilitates a quick estimation of the axle load, and provides a simple method for the preliminary analysis of the vehicle axle load distribution.

[0025] Preferably, by combining the geometric relationships existing between the compression amounts of the leaf springs of each axle and the analysis of the force balance and moment balance of the vehicle frame, it is obtained that:

[0026]

[0027]

[0028] Among them,

[0029]

[0030]

[0031] Integrating various relationships to obtain the calculation formula for the deformation amount of the leaf springs of each axle makes the calculation process more systematic and comprehensive, can accurately solve the deformation amount of the leaf springs of each axle, and then accurately calculate the axle load of each axle, providing a complete and accurate calculation method for vehicle axle load calculation.

[0032] It can be seen from the above technical solutions that the advantages of the present invention are as follows: Introducing the initial compression coefficient of the leaf spring at the reference horizontal position makes the calculation of the leaf spring support force more accurate and improves the calculation accuracy. On the basis of introducing the initial compression coefficient of the leaf spring, adding the deformation amount of the vehicle frame at the actual position relative to the reference horizontal position to obtain the deformation amount of the leaf springs of each axle; and performing force and moment balance analysis on the vehicle frame, and at the same time unifying the initial compression coefficient according to the actual vehicle axle load data to calculate the axle load of each axle; then adding the axle load transfer during braking, determining the axle load transfer amount according to the moment balance, and calculating the axle load distribution during braking. When calculating the load change generated by the braking force on the vehicle, considering the vehicle load transfer makes the calculation result more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0034] Figure 1 It is a schematic diagram of the forces acting on the vehicle model in a stationary state; Figure 2 Schematic diagram of forces acting on a vehicle model in the braking state The components represented by the reference numerals in the figure are as follows 1. Reference horizontal position; 2. Actual position of the vehicle frame Specific implementation manner

[0035] In order to make the objectives, features, and advantages of the present invention more obvious and understandable, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the specific embodiments of the present invention. Obviously, the embodiments described below are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in this patent, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this patent

[0036] In a typical implementation manner of the present invention, as Figure 1 - Figure 2 shown, a method for calculating the axle loads of each axle during braking of an 8×4 vehicle is proposed, including: obtaining the vehicle's gross vehicle weight, the vehicle's structural parameters, and the leaf spring stiffness parameters of each axle, providing reliable data support for subsequent calculations, making the calculation results closer to the axle load conditions under the actual operating state of the vehicle. Among them, the vehicle's structural parameters include the wheelbase between the first and second axles, the wheelbase between the second axle and the equivalent rear axle, and the distance from the center of mass to the first axle; setting an initial compression amount for the leaf springs of each axle at the reference horizontal position 1 of the vehicle frame, introducing a leaf spring initial compression coefficient at the reference horizontal position 1 to make the calculation of the leaf spring support force more accurate and improve the calculation accuracy. On the basis of introducing the leaf spring initial compression coefficient, adding the deformation amount of the actual position 2 of the vehicle frame relative to the reference horizontal position 1 to obtain the deformation amounts of the leaf springs of each axle; performing force and moment balance analysis on the vehicle frame, and unifying the initial compression coefficient according to the actual axle load data of the vehicle to calculate the axle loads of each axle; adding the axle load transfer during braking, determining the axle load transfer amount according to moment balance, and calculating the axle load distribution during braking. When calculating the load change generated by the braking force on the vehicle, considering the vehicle load transfer makes the calculation results more accurate

[0037] Specifically as follows The bending stiffness of the vehicle frame is relatively large, so the vehicle frame is assumed to be a rigid beam; for an 8×4 vehicle, the third and fourth axles are drive axles, and a leaf spring type balance suspension is adopted, that is, the axle loads of the two axles are approximately the same, so it is simplified to one axle, that is, the equivalent rear axle, located at the geometric center of the third and fourth axles, and its stiffness is the sum of the stiffnesses of the third and fourth axles. The balance suspension type double rear axle is simplified into one axle, located in the middle of the third and fourth axles, which simplifies the subsequent calculation formula and improves the calculation efficiency

[0038] In the stationary state, the force model of the vehicle is as Figure 1As shown; Assuming that the frame is in the reference horizontal position 1, the leaf springs corresponding to the three axes are initially compressed , from the reference horizontal position 1 to the frame position where the leaf spring is stressed (i.e. the actual frame position 2), the deformation of the leaf springs of the three axes is ;in addition Figure 1 In, They are the leaf spring stiffness corresponding to the first, second and third axes respectively. Therefore, the support force of the leaf spring on the frame is:

[0039]

[0040]

[0041] The force balance and moment balance analysis of the frame yields:

[0042]

[0043] In the formula, The wheelbase of the first and second axles; The wheelbase of the second and third axles; is the distance from the center of mass to the first axis; is the sprung load, i.e. the total support force of all leaf springs; At the same time, there is a geometric relationship between the compression amounts of leaf springs on each axis:

[0044] Combining the above three equations, we get:

[0045]

[0046]

[0047] Where:

[0048]

[0049]

[0050] Based on this, the forces exerted by the leaf springs of the three axes on the frame can be obtained as follows: ; The axle load of the vehicle is:

[0051]

[0052]

[0053] In the formula, is the unsprung mass of the three axles; During the calculation process, the sprung mass is replaced by the vehicle mass to reduce the calculation difficulty. Generally, the vehicle mass is easier to obtain than the sprung mass. Therefore, for the sake of simplicity in calculation, the unsprung mass are all taken as 0; Take the vehicle mass, and the initial displacement of the leaf spring is unknown. Therefore, the initial compression coefficient is fitted according to the measured axle load data of existing vehicles.

[0054] Analyze the influence of the initial compression coefficient on the axle load calculation, and clarify the influence trend of the initial compression coefficient on the axle load of each axle respectively; invert the initial compression coefficient according to the measured axle load data and unify it, and set unified leaf spring initial displacement parameters for different vehicles to make the calculation more convenient.

[0055] Specifically, the total weight of an 8×4 engineering vehicle is 9607 kg, the wheelbase of the first axle and the second axle is 1800 mm, the wheelbase between the second axle and the equivalent rear axle is 3500 mm, the distance from the center of mass to the first axle is 2632 mm, the unilateral suspension stiffness of the first axle is 582 N / mm, the unilateral suspension stiffness of the second axle is 582 N / mm, and the unilateral suspension stiffness of the rear axle is 3620 N / mm; The measured axle load data of the vehicle is:

[0056] Take different initial compression coefficients and study the influence of each coefficient on the calculated axle load:

[0057] The results show that: As increases, the calculated axle load of the first axle increases, the axle load of the second axle decreases, and the axle load of the rear axle increases; As increases, the calculated axle load of the first axle decreases, the axle load of the second axle increases, and the axle load of the rear axle decreases; As increases, the calculated axle load of the first axle increases, the axle load of the second axle decreases, and the axle load of the rear axle increases; Although and have the same influence trend on the axle load, but has a greater influence amplitude than ; According to the inversion based on the measured axle load data of multiple vehicles, the initial compression amount , is taken as 0, is taken as 3 - 5, and the error between the calculated axle load data and the measured axle load data is relatively small.

[0058] When calculating the load change caused by the braking force on the vehicle, the load transfer of the entire vehicle is considered to make the calculation result more accurate. When braking, the braking force of the ground on the vehicle will generate a turning moment around the center of mass, the magnitude of which is:

[0059] In the formula, ——Braking deceleration (g); ——height of sprung mass centre; ——Vehicle weight.

[0060] The force model of the vehicle is as follows: Figure 2 As shown; Assuming that the frame is in the reference horizontal position 1, the leaf springs corresponding to the three axes are initially compressed , in the braking state, from the reference horizontal position 1 to the frame position where the leaf spring is stressed (i.e. the actual frame position 2), the deformation of the leaf springs of the three axes is ;in addition Figure 2 In, They are the leaf spring stiffness corresponding to the first, second and third axes respectively. Therefore, the support force of each leaf spring on the frame is:

[0061]

[0062]

[0063] Similarly, the force balance and moment balance analysis of the frame yields:

[0064]

[0065] There is a geometric relationship between the compression of leaf springs on each axis:

[0066] Combining the above three equations, we get:

[0067]

[0068]

[0069] Where:

[0070]

[0071]

[0072] Accordingly, the acting forces of the three axle leaf springs on the vehicle frame can be obtained as follows ; At this time, the axle loads of each axle of the vehicle are:

[0073]

[0074]

[0075] In the formula, is the unsprung mass of the three axles.

[0076] Embodiment 1 In this embodiment, there is an 8×4 engineering vehicle with a total weight of 9607 kg, the wheelbase between the first and second axles is 1800 mm, the wheelbase between the second axle and the equivalent rear axle is 3500 mm, the distance from the center of mass to the first axle is 2632 mm, the unilateral suspension stiffness of the first axle is 582 N / mm, the unilateral suspension stiffness of the second axle is 582 N / mm, and the unilateral suspension stiffness of the rear axle is 3620 N / mm.

[0077] The axle load data calculated according to the traditional method and the method of the present invention are shown in the following table:

[0078] The results show that the axle load calculation method adopted in this embodiment has a smaller error and is closer to the measured result.

[0079] Assuming that the braking deceleration is 0.5g, the axle loads of each axle during braking are obtained by calculation as: .

[0080] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for calculating the axle loads of each axle during braking of an 8×4 vehicle, characterized in that, Including: Obtaining the gross vehicle mass of the vehicle, the structural parameters of the vehicle, and the leaf spring stiffness parameters of each axle; Setting an initial compression amount for each axle leaf spring at the reference horizontal position (1) of the vehicle frame, and adding the deformation amount of the actual position (2) of the vehicle frame relative to the reference horizontal position (1) to obtain the deformation amount of each axle leaf spring; Performing force and moment balance analyses on the vehicle frame, and simultaneously unifying the initial compression coefficient according to the actual axle load data of the vehicle to calculate the axle load of each axle; Adding the axle load transfer during braking, determining the axle load transfer amount according to moment balance, and calculating the axle load distribution during braking.

2. The axle load calculation method for each axle during braking of an 8×4 vehicle according to claim 1, characterized in that, The structural parameters of the vehicle include the wheelbase between the first and second axles, the wheelbase between the second axle and the equivalent rear axle, and the distance from the center of mass to the first axle.

3. The axle load calculation method for each axle during braking of an 8×4 vehicle according to claim 1, wherein During braking, the axle load of each axle of the vehicle is: is the unsprung mass of each axle; is the force exerted by the leaf spring of each axle on the vehicle frame.

4. The axle load calculation method for each axle during braking of an 8×4 vehicle according to claim 3, characterized in that, The acting force of each axle leaf spring on the vehicle frame is: is the initial compression amount of the leaf spring corresponding to each axis; is the deformation amount of the leaf spring of each axis; is the leaf spring stiffness corresponding to each axis.

5. The axle load calculation method for each axle during braking of an 8×4 vehicle according to claim 4, characterized in that, Initial compression of leaf spring , Take 0, Take 3 - 5.

6. The method for calculating the axle loads of each axle during braking of an 8×4 vehicle according to claim 4, characterized in that, From the force balance and moment balance analyses of the vehicle frame: It is the total supporting force of all leaf springs.

7. The axle load calculation method for each axle during braking of an 8×4 vehicle according to claim 6, wherein During braking, the overturning moment applied by the ground to the vehicle is: is the braking deceleration; is the height of the sprung mass center; is the vehicle weight.

8. The axle load calculation method for each axle during braking of an 8×4 vehicle according to claim 6, characterized in that, There is a geometric relationship between the compression amounts of each axle leaf spring: is the wheelbase between the first and second axles; is the wheelbase between the second and third axles; is the distance from the centroid to the first axle.

9. The axle load calculation method for each axle during braking of an 8×4 vehicle according to claim 6, characterized in that, Take the vehicle curb weight; unsprung mass Both are 0.

10. The axle load calculation method for each axle during braking of an 8×4 vehicle according to claim 8, characterized in that, Combining the geometric relationship existing between the compression amounts of each axle leaf spring and the force balance and moment balance analyses of the vehicle frame: Wherein, 。

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