A method for analyzing the strength of a gear shift structure of a small cover of a transmission

Abstract

In order to realize the rationality of the gear selecting and shifting force and the structure design of the small cover gear selecting and shifting structure, the application provides a kind of strength analysis method of the gear selecting and shifting structure of the transmission small cover, comprising: S1, testing the gear selecting and shifting force and the strain information of sensitive key points of the gear selecting and shifting structure of the transmission small cover through a test bench; S2, inputting the tested gear selecting and shifting force as the external load spectrum of a simulation model to obtain the strain results of the sensitive key points of the gear selecting and shifting structure of the transmission small cover; S3, comparing the strain information of the sensitive key points of the gear selecting and shifting structure of the transmission small cover with the simulation strain results; S4, adjusting the simulation model according to the comparison results; S5, obtaining the stress and strain results of the sensitive key points by the adjusted simulation model, and calculating the stress time history of the gear selecting and shifting structure of the transmission small cover; S6, calculating the fatigue safety margin and fatigue life of the gear selecting and shifting structure; S7, judging whether the gear selecting and shifting structure of the transmission small cover meets the design requirements according to the fatigue safety margin and fatigue life, and optimizing the gear selecting and shifting force and the gear selecting and shifting structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vehicles, in particular to a transmission small cover selection gear shifting structure strength analysis method. BACKGROUND

[0002] With the increasing requirements of the commercial vehicle market on the handling performance, the selection gear shifting performance of the transmission has become the focus of the vehicle manufacturers and customers, and customers have higher requirements on the comfort of the commercial vehicle driving operation. The commercial vehicle transmission has many gears, and it is very important to realize smooth, clear and light feeling during the selection gear shifting.

[0003] The small cover selection gear shifting structure is an important structure affecting the selection gear shifting of the transmission, and the selection gear shifting force feeling of the customer is mainly reflected on the small cover selection gear shifting structure. In addition, the insufficient service life of the selection gear shifting structure can cause the failure of the transmission, affect the normal operation of the vehicle, and reduce the service life of the transmission.

[0004] At present, the strength of the small cover selection gear shifting structure is mainly evaluated by stress, and the fatigue life of the structure is calculated by a single load. However, the actual small cover selection gear shifting structure is a variable amplitude load, so it is very important to analyze the strength and fatigue strength of the small cover selection gear shifting structure. SUMMARY

[0005] In order to realize the rationality of the selection gear shifting force and the structure design of the small cover selection gear shifting structure, the present application provides a transmission small cover selection gear shifting structure strength analysis method, which adopts the following technical scheme:

[0006] A transmission small cover selection gear shifting structure strength analysis method, characterized in that it comprises the following steps:

[0007] S1, a selection gear shifting test bench is simulated by building a whole vehicle, and the selection gear shifting force of the transmission small cover selection gear shifting structure and the strain information of the sensitive key points are tested by the test bench;

[0008] S2, the tested selection gear shifting force is input as the external load spectrum of the simulation model, and the strain results of the sensitive key points of the small cover selection gear shifting structure are obtained;

[0009] S3, the strain information of the sensitive key points of the tested small cover selection gear shifting structure is compared with the simulation strain results;

[0010] S4, the simulation model is adjusted according to the comparison results;

[0011] S5, the stress and strain results of the sensitive key points are obtained by the adjusted simulation model, and the stress time history formula of the small cover selection gear shifting structure is obtained by formula calculation:

[0012] σ i (t)=σ i’ F(t),

[0013] wherein σ i (t) is the stress time history of the selected shift structure, F(t) is the load time history of the selected shift structure, σ i’ is the static stress of the selected shift structure, m is the fatigue strength exponent;

[0014] S6, calculating the fatigue safety margin and fatigue life of the selected shift structure;

[0015] S7, judging whether the selected shift structure of the small cover meets the design requirements according to the fatigue safety margin and the fatigue life, if the fatigue safety margin is less than the preset value or the fatigue life does not meet the design requirements, optimizing the selected shift force and the selected shift structure.

[0016] Further, in the step S1, the selected shift rocker of the transmission is connected with the simulated whole vehicle manipulator and the selected shift soft shaft, at the same time, the selected shift tester is installed on the sensing handle ball, the sensing handle ball is operated by the selected shift, and the strain gauges are arranged at the sensitive key points of the selected shift structure of the small cover, so that the strain information under different selected shift forces is obtained through the force sensor and the strain acquisition instrument.

[0017] Further, in the step S1, the sensitive key points are positions in the selected shift structure of the small cover which are sensitive to the selected shift force and easy to produce stress concentration.

[0018] Further, in the step S6, the original S-N curve is fitted by using the material parameters, the S-N curve is corrected by using the Goodman average stress, and the fatigue limit σ -1 :

[0019] ;

[0020] wherein σ m is the average stress, σ b is the tensile strength, m is the fatigue strength exponent, N is the stress cycle number, and C is the material constant;

[0021] According to the simulation analysis result, the fatigue safety margin S is calculated according to the maximum static stress:

[0022] ;

[0023] wherein S is the fatigue safety margin, σ -1 is the fatigue limit, σ max is the maximum static stress of the structure obtained according to the stress time history formula of the selected shift structure of the small cover;

[0024] Judging whether the fatigue safety margin S is greater than the preset value.

[0025] Further, the step S6 also includes:

[0026] The fatigue life of the selected gear shifting structure under single load is calculated:

[0027] ,

[0028] Wherein, E is the elastic modulus of the material, σ f ’ The fatigue strength coefficient of the material, ε f ’ The fatigue continuation coefficient of the material, N fi The fatigue life under the i-th load;

[0029] The cycle number, stress mean value and stress amplitude parameters of the stress time sequence under different selected gear shifting forces are calculated by using rainflow counting, the fatigue life of the selected gear shifting structure under single load is converted into the fatigue life under multiple loads, and the fatigue damage under q loads is obtained:

[0030] ,

[0031] Wherein, n i The cycle number of the i-th load;

[0032] The fatigue life calculation formula of the small cover selected gear shifting structure is obtained by using the modified Miner rule:

[0033] .

[0034] Further, in the step S7, the improvement of the small cover selected gear shifting structure mainly reflects that the action radius of the selected gear shifting rocker arm is lengthened, the selected gear shifting lever ratio of the transmission rocker arm is increased, the selected gear shifting force of the whole vehicle is reduced, or the effective length of the selected gear shifting steel ball spring is reduced, and the selected gear shifting force of the whole vehicle is reduced.

[0035] The beneficial effects of the present application are:

[0036] 1. The stress time history σ i’ (t) of the selected gear shifting structure is obtained by the load time history F (t) of the selected gear shifting structure and the static stress σ i (t) of the selected gear shifting structure, the corresponding relationship under different loads, different stresses and different times can be obtained, the stress size can be directly obtained by adjusting the selected gear shifting force of the selected gear shifting structure through the function curve, the fatigue safety margin of the small cover selected gear shifting structure is judged according to the obtained static stress value; on the other hand, the cycle number of the stress time sequence under different selected gear shifting forces can be calculated by using rainflow counting, and the fatigue life of the small cover selected gear shifting structure can be calculated;

[0037] 2. By correcting the SN curve using the Goodman mean stress, the fatigue limit value obtained after correction can be used to determine the fatigue safety margin of the small cover selector shift structure more accurately and reliably.

[0038] 3. It can reasonably and comprehensively predict and evaluate the fatigue life of the small cover shifting structure under variable amplitude load; at the same time, based on the calculated fatigue safety margin and fatigue life, the shifting force can be reduced by optimizing the small cover shifting structure. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the process of the present invention.

[0040] Figure 2 Original SN curve for the strength analysis method of the shift structure of the transmission cover

[0041] Figure 3 Stress-time history and load-time history diagrams for the strength analysis method of the shift structure of the transmission cover. Detailed Implementation

[0042] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0043] like Figure 1 The strength analysis method for the gear selector structure shown in the diagram includes the following steps:

[0044] S1. A test bench is built by simulating a complete vehicle. The gear shift rocker arm of the transmission is connected to the simulated vehicle controller and the gear shift flexible shaft. At the same time, the gear shift tester is installed on the sensing handle ball. The gear shift is operated by the sensing handle ball. Strain gauges are placed at the sensitive key points of the small cover gear shift structure. In this way, the gear shift force and strain information of the sensitive key points are obtained by force sensor and strain acquisition instrument.

[0045] This example uses a 5-speed transmission with a small cover for gear selection and shifting. The gear selection and shifting force test includes the shifting force of 5 forward gears and one reverse gear. In order to eliminate human and testing instrument factors, different people and different time periods were selected for the test.

[0046] The sensitive key points of the small cover gear selection structure are arranged with strain gauges. The sensitive key points are arranged mainly considering the parts which are sensitive to gear selection force and prone to stress concentration. The strain gauges are arranged on the parts with good surface polishing, polishing, cleaning and the like, such as the surface near the gear selection rocker arm and gear selection arm support hole, the surface near the gear selection rocker arm support hole, the gear selection rocker arm support shaft surface, the gear selection rocker arm support shaft surface and the like. The strain information under different gear selection forces is collected by the strain gauges.

[0047] S2, the gear selection force of the test is input as the external load spectrum of the simulation model, and the strain results of the sensitive key points of the small cover gear selection structure are simulated;

[0048] The three-dimensional model of the small cover gear selection structure is established, imported into the finite element software, the material properties and parameters are defined by the finite element pre-processing software, the tetrahedral element meshing is performed on the three-dimensional model, the external load spectrum and constraints are applied for analysis, and the strain results of the sensitive key points are obtained.

[0049] S3, the strain information of the sensitive key points measured by the test bench and the strain results obtained by the simulation analysis are compared;

[0050] The test strain and simulation strain data of the sensitive key points of the small cover gear selection structure at the same position are compared.

[0051] S4, for the test and simulation strain results, the simulation model of the small cover gear selection structure is adjusted;

[0052] S5, the stress and strain results of the sensitive key points are obtained for the adjusted simulation model;

[0053] The stress time history formula of the small cover gear selection structure is calculated:

[0054] σ i (t) = σ i’ F(t) (1);

[0055] Where σ i (t) is the stress time history of the gear selection structure, F(t) is the load time history of the gear selection structure, and σ i’ is the static stress of the gear selection structure.

[0056] S6, the fatigue safety margin and fatigue life of the gear selection structure are calculated.

[0057] The gear selection structure uses the material parameter tensile strength to fit the S-N curve (two-point fitting curve is selected, see Figure 2 ), wherein the fitted S-N curve is divided into two sections, and the corresponding fatigue number is corresponding to the fatigue limit value.

[0058] Moreover,Figure 2 The SN curve is obtained under symmetrical cyclic conditions. The small cover shifting structure, however, undergoes asymmetrical cyclic conditions in actual operation. Therefore, when calculating the fatigue life of the shifting structure, its mean stress needs to be corrected. The fatigue limit value σ is obtained by correcting the SN curve using the Goodman mean stress (Formula 2). -1 :

[0059] (2);

[0060] Where, σ m The mean stress, σ b denoted as tensile strength, m as fatigue strength exponent, N as stress cycle number, and C as material constant.

[0061] The fatigue limit σ is obtained from the Goodman-corrected SN curve. -1 Smaller than the original SN curve, using Figure 2 The fatigue limit value used to determine the fatigue safety margin of the small cover gear selector structure is too large, which will lead to redundant design. Therefore, the fatigue limit value obtained after correction is more accurate and reliable for determining the fatigue safety margin of the small cover gear selector structure.

[0062] The fatigue safety margin is calculated based on the maximum stress from the simulation analysis results. It is then determined whether the fatigue safety margin S is greater than the preset value of 1.1. If S ≥ 1.1, the fatigue strength requirement is met.

[0063] The fatigue safety margin formula is as follows:

[0064] (3);

[0065] Where S is the fatigue safety margin, σ -1 For fatigue limit, σ max To simulate and analyze the stress-time history of the small cover shifting structure, the maximum static stress of the structure is obtained.

[0066] The fatigue life of the shifting structure under a single load is calculated as follows:

[0067] (4);

[0068] Where E is the elastic modulus of the material, σ f ’ The fatigue strength coefficient of the material, ε f ’ N is the fatigue continuity factor of the material. fi Let σ be the fatigue life under the i-th load. i’ The static stress of the gear shifting structure is obtained by using formula (1) in step S5.

[0069] Calculate the number of cycles n of the stress time series under different switching forces using rainflow counting. i The fatigue life of the shifting structure under a single load is transformed into the fatigue life under multiple loads by taking the mean stress and stress amplitude parameters, resulting in the following formula for fatigue damage under q loads:

[0070] (5);

[0071] Where, n i The number of cycles for the i-th load is applied;

[0072] Using the modified Miner's rule, the fatigue life calculation formula for the small cover shifting structure is obtained:

[0073] (6).

[0074] S7. Determine whether the small cover shifting structure meets the design requirements based on the fatigue safety margin and fatigue life. If the fatigue safety margin is less than the preset value or the fatigue life does not meet the design requirements, the shifting force and shifting structure need to be optimized and improved.

[0075] Among them, the improvement of the small cover shifting structure is mainly reflected in the increase of the working radius of the shifting rocker arm, which reduces the shifting force of the whole vehicle by increasing the shifting lever ratio of the shifting rocker arm itself; or by reducing the effective length of the shifting steel ball spring, which reduces the shifting force of the whole vehicle.

[0076] In this embodiment, the material of the small cover selection and shifting structure is 45# steel, and the fatigue parameters of the material are as follows:

[0077]

[0078] Using the formulas (1) to (6) above, we can obtain that the fatigue safety margin S of the small cover gear shifting structure is less than 1.1, and the fatigue life L of the small cover gear shifting structure is... f =1,756,389 cycles, less than the designed fatigue life of 1,800,000 cycles. Therefore, in the 3D model of the small cover gear selector, the working radius of the transmission rocker arm can be increased (from 80mm to 90mm) or the effective length of the steel ball spring can be reduced to decrease the gear selector force. The modified 3D model is imported into the simulation analysis, and the fatigue safety margin S of the small cover gear selector structure is calculated to be greater than 1.1, and the fatigue life L of the small cover gear selector structure is... f =2,123,568 cycles, which is greater than the designed fatigue life of 1,800,000 cycles.

[0079] The transmission small cover selection gear shift structure strength analysis method can reasonably and comprehensively predict and evaluate the fatigue life of the small cover selection gear shift structure under variable amplitude load; meanwhile, according to the calculation of the fatigue safety margin and the fatigue life, the selection gear shift structure can be optimized to reduce the selection gear shift force, accurate and reliable basis is provided for the lightening of the selection gear shift force, and on the other hand, the selection gear shift structure life prediction can be made before the initial sample trial, thereby saving the test cost.

[0080] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements without departing from the principles of the present application, and these improvements should also be considered within the protection scope of the present application.

Claims

1. A method of analyzing the strength of a shift structure of a small cover of a transmission, characterized by, The method comprises the following steps: S1, a whole vehicle building and gear selecting and shifting test bench is simulated, gear selecting and shifting force of a small cover gear selecting and shifting structure and strain information of sensitive key points are tested by the test bench; S2, the tested gear selecting and shifting force is input as an external load spectrum of a simulation model, and strain results of the sensitive key points of the small cover gear selecting and shifting structure are obtained; S3, the tested strain information of the sensitive key points of the small cover gear selecting and shifting structure is compared with the simulation strain results; S4, the simulation model is adjusted according to the comparison results; S5, stress and strain results of the sensitive key points are obtained by the adjusted simulation model, and a stress time history formula of the small cover gear selecting and shifting structure is obtained by formula calculation: σ i (t) = σ i’ F(t), where σ i (t) is the stress time history of the selected shift structure, F(t) is the load time history of the selected shift structure, σ i’ is the static stress of the selected shift structure; S6, fatigue safety margin and fatigue life of the gear selecting and shifting structure are calculated, and fatigue life of the gear selecting and shifting structure under single load is calculated: ， where E is the modulus of elasticity of the material, σ f ’ the fatigue strength coefficient of the material, ε f ’ the fatigue endurance coefficient of the material, N fi the fatigue life under the ith load, m is the fatigue strength exponent; S7, whether the small cover gear selecting and shifting structure meets design requirements is judged according to the fatigue safety margin and the fatigue life, if the fatigue safety margin is less than a preset value or the fatigue life does not meet the design requirements, the gear selecting and shifting force and the gear selecting and shifting structure are optimized.

2. The transmission small cover shift structure strength analysis method according to claim 1, characterized by, In the step S1, a gear selecting and shifting rocker of the transmission is connected with a whole vehicle simulator and a gear selecting and shifting soft shaft, a gear selecting and shifting tester is installed on a sensing handle ball, the sensing handle ball is operated for gear selecting and shifting, and strain gauges are arranged at sensitive key points of the small cover gear selecting and shifting structure, strain information under different gear selecting and shifting forces is obtained by a force sensor and a strain acquisition instrument.

3. The transmission small cover shift structure strength analysis method according to claim 2, characterized by, In the step S1, the sensitive key points are positions in the small cover gear selecting and shifting structure which are sensitive to gear selecting and shifting force and are prone to stress concentration.

4. The transmission small cover shift structure strength analysis method according to claim 1, characterized by, In the step S6, a fatigue safety margin S is calculated according to a maximum static stress of simulation analysis results: The original S-N curve is fitted by using material parameters, the S-N curve is corrected by using Goodman average stress, and the fatigue limit value σ -1 : ; where σ m is the mean stress, σ b is the tensile strength, m is the fatigue strength exponent, N is the number of stress cycles, and C is a material constant. Whether the fatigue safety margin S is greater than a preset value is judged. ; where S is the fatigue safety margin, σ -1 is the fatigue limit, σ max is the maximum static stress of the structure obtained from the stress time history formula of the small cover selected gear shifting structure according to the simulation analysis. In the step S6, a fatigue life calculation method is as follows:

5. The transmission small cover shift structure strength analysis method according to claim 4, characterized by, A cycle number, a stress mean value and a stress amplitude parameter of a stress time sequence under different gear selecting and shifting forces are calculated by rain flow counting, fatigue life of the gear selecting and shifting structure under single load is converted into fatigue life under multiple loads, and fatigue damage under q loads is obtained: A fatigue life calculation formula of the small cover gear selecting and shifting structure is obtained by a modified Miner rule: ， wherein n i is the number of cycles for the i-th load application; In the step S7, improvement of the small cover gear selecting and shifting structure mainly reflects that an action radius of a gear selecting and shifting rocker is lengthened, gear selecting and shifting force of the whole vehicle is reduced by increasing a gear selecting and shifting lever ratio of the transmission rocker itself, or effective length of a gear selecting and shifting steel ball spring is reduced, and gear selecting and shifting force of the whole vehicle is reduced. 。 6. The transmission small cover shift structure strength analysis method according to claim 1, characterized by, ​

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