A method for calculating the total stiffness of a Z-shaped leaf spring composite air suspension

Abstract

The present invention relates to a method for calculating the total stiffness of a Z-shaped leaf spring composite air suspension. Based on the material mechanics theory, the stiffness of the rear part of the Z-shaped guide spring is firstly considered to calculate the stiffness C of the Z-shaped guide spring at the axle point. BD , and then convert the stiffness of the air spring to the stiffness C at the axle point BA Finally, the total stiffness C of the Z-shaped leaf spring composite air suspension is calculated. B The present invention takes full account of the deformation of all segments of the Z-shaped guide spring and proposes a parameterized calculation method, which improves the calculation accuracy compared with the traditional calculation method. Compared with the finite element calculation method and the vehicle dynamics calculation method, which have similar accuracy, the parameterized calculation method can greatly reduce the calculation time of engineers and greatly improve the efficiency of engineers.

Description

Technical Field

[0001] The invention relates to a method for calculating the total stiffness of a Z-shaped leaf spring composite air suspension, and belongs to the technical field of vehicle suspension design. Background Art

[0002] The vehicle's suspension system is a key component of the vehicle's chassis system. The suspension system attenuates the vibration of the road surface and transmits it to the vehicle, improving the smoothness and comfort of the vehicle's ride. Air suspension is a type of vehicle suspension that can achieve lower stiffness and bias frequency by adjusting the air pressure of the airbag under different loads, thereby better improving the smoothness of the vehicle.

[0003] As for the stiffness calculation of the Z-shaped leaf spring composite air suspension, in the existing traditional calculation method, the total stiffness of the air suspension takes into account the stiffness of the Z-shaped guide spring and the stiffness of the air spring, but the stiffness of the Z-shaped guide spring is assumed to be completely rigid from the axle mounting point to the air spring mounting point. This calculation causes the stiffness of the Z-shaped guide spring to be larger than the actual situation. When the ratio of the stiffness of the Z-shaped guide spring to the stiffness of the air suspension is relatively small, the calculated stiffness and the actual stiffness will deviate greatly. Summary of the invention

[0004] The purpose of the present invention is to propose a method for calculating the total stiffness of a Z-shaped leaf spring composite air suspension in response to the problems existing in the prior art. The Z-shaped guide spring is divided into segments for segmented calculation, and the flexibility of all segments of the Z-shaped guide spring is fully considered. Compared with the traditional theoretical calculation method, the calculation accuracy is greatly improved.

[0005] The specific technical solution of the present invention is as follows: A method for calculating the total stiffness of a Z-shaped leaf spring composite air suspension comprises the following specific steps:

[0006] Step 1: Calculate the stiffness C of the Z-shaped guide spring at the end B of the axle center point BD ,

[0007] The Z-shaped guide spring is simplified into a rectangular structure with equal cross-sections at the front and rear. The front mounting point B1 of the Z-shaped guide spring and the frame and the mounting point B2 of the Z-shaped guide spring and the air spring are simply supported. A vertical upward force F is applied to the center point B of the axle. Under the action of the vertical force F, the vertical displacement of the Z-shaped guide spring is δ BD ;

[0008] According to the stiffness C of the front end point of the Z-shaped guide spring B1 , the ratio of the longitudinal distance b from the air spring to the center of the axle to the longitudinal distance a from the front end of the Z-shaped guide spring to the axle λ, the ratio of the height H of the Z-shaped guide spring to the longitudinal distance a from the front end of the Z-shaped guide spring to the axle λ1, the ratio of the longitudinal distance b2 from the bending point of the Z-shaped guide spring to the installation point of the air spring to the longitudinal distance a from the front end of the Z-shaped guide spring to the center of the axle λ2, then:

[0009]

[0010] Step 2: Calculate the stiffness C of the air spring at the axle point BA

[0011] According to the stiffness C of the air spring B2 , the stiffness C of the axle point is calculated BA , as shown in the following formula:

[0012] C BA =(1+λ) 2 C B2 ;

[0013] Step 3: Calculate the total stiffness C of the Z-shaped leaf spring composite air suspension B

[0014] The total stiffness C of the Z-shaped leaf spring composite air suspension B C BD and C BA The series stiffness of the air spring is defined as B2 The stiffness C of the front end of the Z-shaped guide spring B1 The ratio K is used to calculate the total stiffness C of the air suspension. B , as shown in the following formula:

[0015]

[0016] The structure of the Z-shaped leaf spring composite air suspension adopted by the present invention is a two-point air suspension, in which airbags and Z-shaped leaf springs are symmetrically arranged at the left and right ends of the outer side of the frame longitudinal beam, the lower end base of the airbag is fixed to the rear end of the Z-shaped leaf spring by bolts, and the upper end air chamber cover of the airbag is fixed to the lower wing surface of the frame longitudinal beam by bolts; the Z-shaped leaf spring is a Z-shaped variable cross-section structure, the cross-section thickness is narrow at the front and wide at the rear, and a curled ear-shaped circular hole is provided at the front end of the leaf spring. A column pin is used to fix the front end of the leaf spring to the side wing surface of the frame longitudinal beam through the curled ear hole of the leaf spring, and a U-shaped bolt is used to fix the leaf spring on the axle in the middle of the leaf spring, before the first bending point of the Z shape, and a positioning hole is provided at the rear end of the leaf spring for fixing the airbag base.

[0017] Furthermore, the specific content of step 1 is:

[0018] Step 1.1, set the height H section of the Z-shaped guide spring to be rigid, and calculate the stiffness C of the Z-shaped guide spring at the axle point BD1 , as shown in the following formula:

[0019]

[0020] Step 1.2: Set the height H section of the Z-shaped guide spring as rigid, and calculate the rigidity C of the Z-shaped guide spring at the axle point. BD2, as shown in the following formula:

[0021]

[0022] Step 1.3: Stiffness C of the Z-shaped guide spring at the axle point BD Then C BD1 and C BD2 The series stiffness is

[0023]

[0024] Furthermore, in step 1, the front end point stiffness C of the Z-shaped guide spring is B1 Defined as a cantilever beam with fixed supports at ends B and B2, and a vertical upward load F applied at end B1 B1 , the vertical displacement generated at end B1 is δ B1 , then C B1 As shown in the following formula:

[0025]

[0026] Wherein, E is the elastic modulus of the Z-shaped guide spring material, and I is the moment of inertia of the Z-shaped guide spring section.

[0027] Furthermore, the total stiffness C of the Z-shaped leaf spring composite air suspension is B It also has two forms of expression;

[0028] If the Z-shaped guide spring is assumed to be rigid from the axle center point B to the air spring mounting point B2, and the rigid section includes the Z-shaped guide spring height H, then

[0029]

[0030] If the Z-shaped guide spring height H section is assumed to be rigid, then

[0031]

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention relates to a method for calculating the total stiffness of a Z-shaped leaf spring composite air suspension, which fully considers the deformation of all segments of the Z-shaped guide spring and proposes a parameterized calculation method, which improves the calculation accuracy compared with the traditional calculation method. Compared with the finite element calculation method and the vehicle dynamics calculation method, which have similar accuracy, the parameterized calculation method can greatly reduce the calculation time of engineers and greatly improve the efficiency of engineers. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be further described below in conjunction with the accompanying drawings.

[0035] Figure 1 It is a structural schematic diagram of the present invention. DETAILED DESCRIPTION

[0036] Example

[0037] This embodiment provides a method for calculating the total stiffness of a Z-shaped leaf spring composite air suspension. Figure 1 As shown, the parameters of the Z-shaped leaf spring composite air suspension are known: the longitudinal distance from the front end of the Z-shaped guide spring to the axle a = 700mm, the longitudinal distance from the air spring to the center of the axle b = 409mm, the height of the Z-shaped guide spring H = 190mm, the longitudinal distance from the bending point of the Z-shaped guide spring to the installation point of the air spring b2 = 200mm, the stiffness of the front end of the Z-shaped guide spring C B1 =256N / mm, air spring stiffness C B2 =65N / mm. Calculate the total stiffness of the Z-shaped leaf spring composite air suspension.

[0038] The specific calculation steps are as follows:

[0039] Step 1: Calculate the stiffness C of the Z-shaped guide spring at the center point B of the axle BD ,

[0040] The Z-shaped guide spring is simplified into a rectangular structure with equal cross-sections at the front and rear ends. The front mounting point B1 end of the Z-shaped guide spring and the frame and the mounting point B2 end of the Z-shaped guide spring and the air spring are simply supported. The definition of simply supported is that the support only provides constraints in the translation direction, but not in the rotation direction. A vertical upward force F is applied to the center point B of the axle. Under the action of the vertical force F, the vertical displacement generated by the Z-shaped guide spring is δ BD .

[0041] Define the ratio of the longitudinal distance b from the air spring to the center of the axle to the longitudinal distance a from the front end point of the Z-shaped guide spring to the axle λ, the ratio of the height H of the Z-shaped guide spring to the longitudinal distance a from the front end point of the Z-shaped guide spring to the axle λ1, and the ratio of the longitudinal distance b2 from the "bending point" of the Z-shaped guide spring to the installation point of the air spring to the longitudinal distance a from the front end point of the Z-shaped guide spring to the center of the axle λ2.

[0042] Step 1.1: Set the Z-shaped guide spring height H section to be completely rigid. The stiffness of the Z-shaped guide spring at the axle point is C BD1 .

[0043]

[0044] Step 1.2: Set the height H section of the Z-shaped guide spring to be rigid, and calculate the stiffness C of the Z-shaped guide spring at the axle point. BD2 , as shown in the following formula:

[0045]

[0046] Step 1.3: Stiffness C of the Z-guide spring at the axle point BD C BD1 and C BD2 The series stiffness is

[0047]

[0048] Step 2: Calculate the stiffness C of the air spring at the axle point BA

[0049] According to the stiffness C of the air spring B2 , calculate the stiffness C of the axle point BA , as shown in the following formula:

[0050] C BA =(1+λ) 2 C B2 .

[0051] Step 3: Calculate the total stiffness C of the Z-shaped leaf spring composite air suspension B .

[0052] The total stiffness C of the Z-shaped leaf spring composite air suspension B C BD and C BA The series stiffness of the air spring is defined as C B2 The stiffness C of the front end of the Z-shaped guide spring B1 The ratio K is used to calculate the total stiffness C of the air suspension. B , as shown in the following formula:

[0053]

[0054] Substituting the relevant parameters into the above formula, we get C B =141.4N / mm.

[0055] Moreover, the total stiffness C of the Z-shaped leaf spring composite air suspension of this embodiment is B It can also be expanded into two other forms;

[0056] According to the existing traditional calculation method, if the Z-shaped guide spring from the axle center point B to the air spring installation point B2 is assumed to be rigid (the rigid section includes the Z-shaped guide spring height H), then

[0057]

[0058] If the Z-shaped guide spring height H section is assumed to be rigid, then

[0059]

[0060] In order to further verify the correctness of the formula, the finite element method is used to calculate the stiffness of the Z-shaped leaf spring composite air suspension. The Z-shaped guide spring is simulated by BEAM beam unit, the air spring is simulated by CELAS1 unit, and the solver is Optistruct. The finite element method finally obtains C B =141.3N / mm.

[0061] The theoretical calculation method proposed in the present invention has the same accuracy as the finite element calculation method, and the calculation accuracy is improved by 6.2% compared with the traditional calculation method.

[0062] In addition to the above examples, the present invention may also have other implementations. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope of this claim.

Claims

1. A method for calculating the total stiffness of a Z-shaped leaf spring composite air suspension, characterized in that: The structure of the Z-shaped leaf spring composite air suspension is a two-point air suspension, in which air bags and Z-shaped leaf springs are symmetrically arranged at the left and right ends of the outer side of the frame longitudinal beam. The lower end base of the airbag is fixed to the rear end of the Z-shaped leaf spring by bolts, and the upper end air chamber cover of the airbag is fixed to the lower wing surface of the frame longitudinal beam by bolts; the Z-shaped leaf spring is a Z-shaped variable cross-section structure, the cross-section thickness is narrow at the front and wide at the rear, and the front end of the leaf spring is provided with a rolled ear-shaped circular hole, and the front end of the leaf spring is fixed to the side wing surface of the frame longitudinal beam by a column pin through the leaf spring rolled ear hole, and the leaf spring is fixed to the axle by a U-shaped bolt in the middle of the leaf spring, before the first bending point of the Z shape, and a positioning hole is provided at the rear end of the leaf spring for fixing the airbag base; The specific steps include: Step 1: Calculate the stiffness C of the Z-shaped guide spring at the end B of the axle center point BD , The Z-shaped guide spring is simplified into a rectangular structure with equal cross-sections at the front and rear. The front mounting point B1 of the Z-shaped guide spring and the frame and the mounting point B2 of the Z-shaped guide spring and the air spring are simply supported. A vertical upward force F is applied to the center point B of the axle. Under the action of the vertical force F, the vertical displacement of the Z-shaped guide spring is δ BD ; According to the stiffness C of the front end point of the Z-shaped guide spring B1 , the ratio of the longitudinal distance b from the air spring to the center of the axle to the longitudinal distance a from the front end of the Z-shaped guide spring to the axle λ, the ratio of the height H of the Z-shaped guide spring to the longitudinal distance a from the front end of the Z-shaped guide spring to the axle λ1, the ratio of the longitudinal distance b2 from the bending point of the Z-shaped guide spring to the installation point of the air spring to the longitudinal distance a from the front end of the Z-shaped guide spring to the center of the axle λ2, then: Step 2: Calculate the stiffness C of the air spring at the axle point BA According to the stiffness C of the air spring B2 , the stiffness C of the axle point is calculated BA , as shown in the following formula: C BA =(1+λ) 2 C B2 ; Step 3: Calculate the total stiffness C of the Z-shaped leaf spring composite air suspension B The total stiffness C of the Z-shaped leaf spring composite air suspension B C BD and C BA The series stiffness of the air spring is defined as B2 The front point stiffness C of the Z-shaped guide spring B1 The ratio K is used to calculate the total stiffness C of the air suspension. B , as shown in the following formula:

2. The method for calculating the total stiffness of a Z-shaped leaf spring composite air suspension according to claim 1, characterized in that: The specific content of step 1 is: Step 1.1, set the height H section of the Z-shaped guide spring to be rigid, and calculate the stiffness C of the Z-shaped guide spring at the axle point BD1 , as shown in the following formula: Step 1.2: Set the height H section of the Z-shaped guide spring as rigid, and calculate the rigidity C of the Z-shaped guide spring at the axle point. BD2 , as shown in the following formula: Step 1.3: Stiffness C of the Z-shaped guide spring at the axle point BD Then C BD1 and C BD2 The series stiffness is 3. The method for calculating the total stiffness of a Z-shaped leaf spring composite air suspension according to claim 2, characterized in that: In step 1, the front end point stiffness C of the Z-shaped guide spring B1 Defined as a cantilever beam with fixed supports at ends B and B2, and a vertical upward load F applied at end B1 B1 , the vertical displacement generated at end B1 is δ B1 , then C B1 As shown in the following formula: Wherein, E is the elastic modulus of the Z-shaped guide spring material, and I is the moment of inertia of the Z-shaped guide spring section.

4. The method for calculating the total stiffness of a Z-shaped leaf spring composite air suspension according to claim 1, characterized in that: The total stiffness C of the Z-shaped leaf spring composite air suspension B It also has two forms of expression; If the Z-shaped guide spring is assumed to be rigid from the axle center point B to the air spring mounting point B2, and the rigid section includes the Z-shaped guide spring height H, then If the Z-shaped guide spring height H section is assumed to be rigid, then

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