A dual-piston diaphragm air spring and its key parameter design method

Abstract

A dual-piston diaphragm air spring includes a housing, an upper mounting seat for fixedly connected to a vehicle body, and a lower mounting seat for fixedly connected to a suspension swing arm, the upper mounting seat being provided with a first piston mounting column extending downward, a first piston being fixedly provided on the first piston mounting column, the lower mounting seat being provided with a second piston mounting column extending upward, a second piston being fixedly provided on the second piston mounting column, a space being left between the first piston mounting column and the second piston mounting column, a rubber airbag being provided between the first piston and the second piston, the rubber airbag being located in the housing, the upper end of the rubber airbag being fixedly connected to the first piston mounting column, and the lower end being fixedly connected to the second piston mounting column, the axial length ratio of the first piston mounting column to the second piston mounting column being 2:1 to 4:1, the axial length of the first piston being the same as that of the first piston mounting column, and the axial length of the second piston being the same as that of the second piston mounting column.

Description

Technical Field

[0001] The present invention relates to the automotive field, and in particular to a double-piston diaphragm air spring and a design method for key parameters thereof. Background Art

[0002] like Figure 1 As shown, a traditional single-piston diaphragm air spring is a resilient element widely used in automotive and other applications. Its main structure generally includes a first mounting seat 1a, a second mounting seat 9a, a piston 2a disposed between the first and second mounting seats 1a, a piston rod 10a, a rubber airbag formed by a bladder skin 3a, a dust cover 4a, an aluminum shell 5a, a first retaining ring 6a, a support ring 7a, and a second retaining ring 8a. The spring's stiffness can be adjusted as needed to accommodate varying loads and operating conditions. For example, in automotive suspension systems, diaphragm air springs can effectively improve ride comfort and handling stability. They automatically adjust their height and stiffness based on road conditions, reducing vehicle bumps and vibrations and ensuring a smoother, quieter ride.

[0003] However, the current practical application of single-piston diaphragm air springs in automotive suspension systems still has many drawbacks. For example, the greater the sprung mass in the automotive suspension system, the smaller the installation space for the air spring. The smaller the installation space, the less elastic force the air spring can provide. To accommodate an air spring that meets the elastic force and deflection requirements within the limited installation space, the current approach is to reduce the piston diameter under the air spring's designed load state and increase the internal air pressure. While this approach can accommodate an air spring that meets the elastic force requirements within a limited installation space, it still has significant drawbacks. It can cause the air pressure in the air spring chamber to be too high, leading to accelerated aging of the bladder and shortening the life of the air spring.

[0004] To extend the service life of air springs, existing technologies have also adopted the technical means of providing upper and lower pistons to reduce the compression / extension limit of the rubber airbag, thereby achieving the technical purpose of increasing the service life of the rubber airbag. In this dual-piston rubber air spring structure, the upper and lower ends of the rubber airbag can be compressed simultaneously, resulting in a shorter vertical stroke when the airbag is compressed and released, thereby reducing the ultimate load on the rubber airbag skin. Under the same conditions, the aging rate of the airbag skin is alleviated to a certain extent, ultimately extending the service life of the entire air spring. For example, "A Dual-Piston Rubber Air Spring" with publication number CN204784382U.

[0005] However, both the traditional single-piston diaphragm air spring and the above-mentioned double-piston rubber air spring still have a huge technical defect:

[0006] During the actual operation of the vehicle, as the suspension moves vertically, the air spring's deflection angle will be very large, causing the actual stiffness of the air spring to deviate too much from the designed stiffness, resulting in reduced suspension control accuracy, reduced comfort, reduced durability, and reduced safety performance.

[0007] Especially when the air spring is installed at the rear of the vehicle, its deflection angle can reach over 30 degrees as the suspension moves up and down. This large deflection angle causes the piston mounting post to repeatedly contact the inner wall of the rubber airbag during the suspension's movement, subjecting the rubber airbag to immense pressure and making it highly susceptible to puncture by the piston mounting post.

[0008] Compared to traditional fuel-powered vehicles with comparable range, electric vehicles now have more features. To maintain this range, batteries are becoming heavier, leading to an increase in vehicle mass. Consequently, requirements for the lifespan and elasticity of air springs are becoming increasingly stringent. Current air springs and automotive suspension systems are no longer suitable, creating an urgent need for a membrane air spring that can meet design requirements within limited space while ensuring a long service life. Summary of the Invention

[0009] The purpose of the present invention is to address the corresponding shortcomings of the existing technology and provide a double-piston diaphragm air spring, which divides the original single working range into two different working ranges, upper and lower. A corresponding piston is set in each working range. Through the division of labor and cooperation of the two pistons, it can not only meet the design requirements within a limited space, but also ensure its service life.

[0010] The purpose of the present invention is to adopt the following scheme to achieve:

[0011] A dual-piston diaphragm air spring includes a housing, an upper mounting seat for fixedly connected to a vehicle body, and a lower mounting seat for fixedly connected to a suspension swing arm, the upper mounting seat being provided with a first piston mounting column extending downward, a first piston being fixedly provided on the first piston mounting column, the lower mounting seat being provided with a second piston mounting column extending upward, a second piston being fixedly provided on the second piston mounting column (for example, threadedly fixed), a space being left between the first piston mounting column and the second piston mounting column, a rubber airbag being provided between the first piston and the second piston, the rubber airbag being located in the housing, the upper end of the rubber airbag being fixedly connected to the first piston mounting column, and the lower end being fixedly connected to the second piston mounting column, the axial length ratio of the first piston mounting column to the second piston mounting column being 2:1 to 4:1, the axial length of the first piston being the same as that of the first piston mounting column, and the axial length of the second piston being the same as that of the second piston mounting column.

[0012] Preferably, the first piston and the second piston are conical structures, and the taper of the first piston is smaller than that of the second piston.

[0013] Preferably, the first piston mounting column and the second piston mounting column are both provided with blind holes, the bladder skin of the upper part of the rubber airbag is fixedly connected to the lower end of the first piston mounting column by a first buckling ring, and the bladder skin of the lower part of the rubber airbag is fixedly connected to the upper end of the second piston mounting column by a second buckling ring, so that the bladder skin of the rubber airbag and the blind holes of each piston mounting column are sealed to form an air chamber.

[0014] Preferably, a support ring is provided inside the rubber airbag, and the support ring enables the bladder skin of the rubber airbag to abut against the inner wall of the shell.

[0015] Preferably, a dust cover is provided between the exterior of the shell and the upper mounting seat and the lower mounting seat.

[0016] The key parameters of the dual-piston diaphragm air spring include the length and cross-sectional diameter of each piston mounting post, the shape of each piston (including wall thickness, design diameter, minimum diameter, maximum diameter, etc.), as well as the air chamber volume and air chamber pressure. The design method of these key parameters includes the following steps:

[0017] 1) The length of the first piston mounting post is determined based on the vertical design height of the air spring and the relative compression stroke threshold, and the length of the second piston mounting post is determined based on the relative compression stroke threshold and the yaw angle threshold required by the air spring design:

[0018] 2) determining a design diameter of the first piston and a pressure of the air spring chamber under the design load based on the design load of the air spring and a pressure threshold of the air spring chamber;

[0019] 3) Based on the vertical design stiffness required by the air spring design and the principle of suspension frequency invariance, the overall shape of the first piston is designed to obtain the minimum diameter of the first piston and the volume of the air spring chamber under the design load;

[0020] 4) After the overall shape of the first piston is determined, the cross-sectional diameter of the first piston mounting post is determined based on the minimum diameter of the first piston;

[0021] 5) After determining the diameter of the maximum cross section of the air spring according to the suspension envelope requirements, the cross section diameter of the second piston mounting post is determined based on the diameter of the maximum cross section of the air spring.

[0022] 6) Based on the design value of the cross-sectional diameter of the second piston mounting column, the strength design of the second piston is performed to obtain the minimum wall thickness value and the minimum diameter of the second piston.

[0023] 7) According to the design rules of the deflection angle contribution of the second piston, the maximum diameter of the second piston and the overall shape of the second piston are designed.

[0024] Preferably, the design diameter of the first piston and the design value of the air spring chamber pressure under the design load are calculated using the following formula:

[0025] F c (0)=π[R e (0)] 2 [P(0)-P d ]

[0026] Where, F c (0) is the design load of the air spring, π is the circumference of the circle, R e (0) is the design diameter of the first piston, P(0) is the pressure of the air spring chamber under the design load, P d is atmospheric pressure.

[0027] Preferably, the overall shape of the first piston is designed according to the following set of equations, which determine the minimum diameter of the first piston and the volume of the air spring chamber under the design load:

[0028]

[0029] R 差 =R0-R e (z)

[0030]

[0031] Where K is the vertical design stiffness of the membrane air spring, π is the circumference, z is the relative compression stroke of the air spring, R e (z) is the effective radius of the air spring chamber when the relative compression stroke is equal to z, R ’ e (z) is R e (z), P(0) is the pressure of the air spring chamber under the design load, V(0) is the volume of the air spring chamber under the design load, V(z) is the volume of the air spring chamber when the relative compression stroke is equal to z, V1 is the volume in the air spring chamber that does not change with the change of the relative compression stroke, such as the sum of the volumes of the blind holes of the first piston mounting column and the second piston mounting column, V2(z) is the volume of the cylinder V2 when the relative compression stroke is z, V3(z) is the volume of the convex arc rotating body V3 when the relative compression stroke is z, V4(z) is the volume of the standard rotating body V4 when the relative compression stroke is z, V5(z) is the volume of the concave arc rotating body V5 when the relative compression stroke is z, h(z) is the height of the cylinder V2 when the relative compression stroke is z, P d is the atmospheric pressure, R0 is the inner radius of the shell, R s (h) is the function of piston radius, is the piston radius when the air spring compression stroke is z, for The first derivative of R 差 is the difference between the inner radius of the housing and the effective radius of the air spring chamber, H is the distance between the upper end face of the second piston and the top of the air spring when the relative compression displacement is 0, i is the vertical distance between the lowest point of the contact surface between the rubber airbag and the piston and the upper end face of the second piston when the relative compression displacement is 0, V e ’ (z) is the rate of change of the air spring chamber volume.

[0032] Preferably, the cross-sectional diameter of the first piston mounting post is 8-20 mm smaller than the minimum diameter of the first piston. This is because the compressive strength of the entire piston needs to be taken into consideration to ensure that the air spring has a sufficient lifespan and is not shortened due to insufficient piston durability.

[0033] Similarly, to ensure that the bladder skin between the second piston and the outer casing has sufficient space to move and will not contact the bladder skin after the second piston deflects laterally during movement, the cross-sectional diameter of the second piston mounting column is 70 to 100 mm smaller than the diameter of the maximum cross-sectional area of ​​the air spring.

[0034] Preferably, in order to ensure vertical stiffness while leaving sufficient movement space for the bladder skin between the air spring outer sleeve and the first piston, and to avoid the piston mounting column or the piston abutting the bladder skin, so as to ensure the durability of the bladder skin, the maximum cross-sectional diameter of the first piston is 50 to 80 mm smaller than the maximum cross-sectional diameter of the air spring;

[0035] Since the design rules of the second piston's swing angle contribution need to be met (i.e., the swing angle contribution is not less than 80% of the total swing angle design requirement), the maximum cross-sectional diameter of the second piston is 30 to 60 mm smaller than the diameter design value at the maximum cross-sectional area of ​​the air spring.

[0036] The key parameters obtained in steps 1) to 7) of the key parameter design method of the present invention are actually intended to enable the designed air spring to divide the original single working range of the air spring into two different working ranges, each with a corresponding piston to work, and to minimize the risk of contact between the bladder skin and the piston and the piston mounting post during operation:

[0037] ①The first piston is mainly responsible for the up and down reciprocating motion of the air spring (most of it), and its secondary task is to bear a small part of the lateral deflection motion of the air spring;

[0038] ②The second piston is mainly responsible for the lateral deflection movement of the air spring (most of it), and the secondary task of the second piston is to bear the up and down reciprocating movement of a small part of the air spring;

[0039] The advantage of the present invention is that an air spring manufactured according to the key parameters designed in the above manner can, through the division of labor and cooperation between the two pistons, even if the air spring of the present invention is installed at the rear of a vehicle, the piston mounting post will not contact the rubber airbag inner wall, even with the suspension's lifting and lowering motion, even at large deflection angles. This avoids the significant risk of the rubber airbag being punctured by the piston mounting post, thereby extending the service life of the air spring. Therefore, an air spring of this structure can be installed in a limited space without increasing the air pressure within the air spring chamber, and can meet the designed elastic force requirements.

[0040] Glossary

[0041] Relative compression stroke: Once the air spring is installed in the predetermined position, the piston will be subjected to a certain external pressure (this pressure is usually called the design load), so that the air spring is in the design load state. The position of the piston at this time is taken as the relative zero point. When the piston is subjected to additional pressure at the installation position, the displacement of the piston from the initial position (relative zero point) to the end position is the relative compression stroke of the air spring (Note: the additional external pressure on the piston does not include the design load of the air spring). That is, the air spring is in the design load state when the relative compression stroke of the air spring is zero. The "ultimate tensile displacement" in the present invention refers to the upper limit of the relative compression stroke, and the "ultimate compressive displacement" refers to the lower limit of the relative compression stroke.

[0042] Piston design diameter: Figure 11 As shown, a two-dimensional coordinate system is established when the air spring is under its design load. The vertical axis of this two-dimensional coordinate system is the central axis of the air spring. The lowest points of the contact surface between the rubber bladder and the piston include the left and right contact points. The line connecting the left and right contact points coincides with the horizontal axis of the two-dimensional coordinate system. A piston radius function Rs(h) is established in this two-dimensional coordinate system. The vertical coordinates of the left and right contact points in the two-dimensional coordinate system are both 0. In the piston radius function Rs(h), h is the vertical displacement of the lowest point of the contact surface between the rubber bladder and the piston when the relative compression stroke of the air spring is equal to z. When the displacement is upward, h is positive, and when it is downward, h is negative. According to geometric principles, h = z / 2. The curve of the piston radius function Rs(h) is actually the outer contour curve of the piston. The horizontal coordinate of any point on this curve with a vertical coordinate of h is used as the piston radius, that is, the horizontal coordinate of any point on the piston surface with a vertical coordinate of h when the piston is in the two-dimensional coordinate system established above. That is, the piston diameter under the design load state is twice the piston radius when the relative compression stroke of the air spring is zero. For example, the "first piston design diameter" in the present invention refers to the design diameter of the first piston.

[0043] Vertical design stiffness: in the present invention, it refers to the vertical stiffness of the air spring when it is in the design load state.

[0044] Vertical design height: in the present invention, refers to the vertical height of the air spring when it is in the design load state.

[0045] Maximum design diameter: in the present invention, refers to the diameter of the maximum cross section of the air spring in the design load state.

[0046] Minimum diameter of the first piston: refers to the diameter of the first piston at the point where the cross-sectional area is the smallest.

[0047] The principle of constant suspension offset frequency: This principle is a key principle in air spring design. Suspension offset frequency refers to the natural vibration frequency of the vehicle's suspension system. Maintaining this principle means ensuring that the suspension's natural vibration frequency remains within a certain range when designing or adjusting the air spring stiffness. This principle is important for several reasons. First, an appropriate suspension offset frequency ensures a smooth ride. If the offset frequency is too high, the vehicle will feel noticeably jerky, affecting ride comfort. If the offset frequency is too low, the vehicle may experience a sense of jitteriness and compromise handling stability. Second, maintaining a constant suspension offset frequency helps maintain vehicle handling performance. For example, when cornering, a stable suspension offset frequency allows the vehicle to better respond to driver inputs, improving steering accuracy and timeliness.

[0048] Design rules for yaw angle contribution: Design rules for yaw angle contribution are crucial in air spring design. First, the impact of the air spring's structural parameters on the yaw angle must be considered. For example, the shape, size, and material of the airbag directly affect its deformation under load, thereby affecting the yaw angle contribution. Rules may specify the permissible yaw angle range for airbags of different shapes and sizes. Furthermore, the installation method and location also affect the yaw angle contribution. The choice of mounting point and the difference in fixing method can lead to different yaw performance of the air spring during operation. Design rules clarify how to select the appropriate installation method to control the yaw angle. Furthermore, the operating environment and load conditions are also key factors. For example, different road conditions, vehicle speeds, and load weight can all cause changes in the force exerted on the air spring, thereby affecting the yaw angle. The "yaw angle contribution design rules" set corresponding design standards based on these changes. The "yaw angle contribution design rules" in this invention refer to a yaw angle contribution of no less than 80% of the total yaw angle design requirement.

[0049] Bag skin: the rubber skin outside the rubber airbag;

[0050] The effective radius of the air spring chamber: Figure 11As shown, the actual working plane of the air spring chamber is a circle, and the radius of the circle is used as the effective radius of the air spring chamber, that is, the square of the effective radius of the air spring chamber multiplied by pi is equal to the effective cross-sectional area of ​​the air spring chamber. The effective cross-sectional area A of the air spring chamber in the present invention is e The actual working plane area of ​​the air spring chamber is perpendicular to the force direction of the piston. The actual working plane of the air spring chamber is actually an artificially defined force plane inside the air spring chamber. The additional external pressure F c It is equal to the effective cross-sectional area of ​​the air spring chamber multiplied by the pressure of the air spring (the difference between the pressure inside the air spring chamber and the atmospheric pressure). BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a structural diagram of a traditional single-piston diaphragm air spring;

[0052] Figure 2 It is a structural schematic diagram of the present invention;

[0053] Figure 3 This is a schematic diagram of the structure of the present invention when the rubber airbag is not installed;

[0054] Figure 4 A flow chart of the key parameter design method of the present invention;

[0055] Figure 5 This is a schematic diagram of the installation of the present invention on a vehicle suspension in an embodiment;

[0056] Figure 6 Schematic diagram of the installation of a traditional single-piston film air spring in the embodiment;

[0057] Figure 7 Schematic diagram of the installation of a double-piston diaphragm air spring of the prior art in the embodiment;

[0058] Figure 8 Schematic diagram of the operation of the double-piston diaphragm air spring of the present invention in an embodiment;

[0059] Figure 9 Schematic diagram of the operation of a conventional single-piston diaphragm air spring in an embodiment;

[0060] Figure 10 Schematic diagram of the operation of a dual-piston diaphragm air spring of the prior art in the embodiment;

[0061] Figure 11 A schematic diagram of the diameter of the first piston under the design load state in the present invention;

[0062] Figure 12Schematic diagram of the volume V1 of the air spring chamber that does not change with the change of the relative compression stroke in an embodiment of the present invention;

[0063] Figure 13 is the volume of the cylinder V2 in the air spring chamber when the relative compression stroke is z in the embodiment of the present invention;

[0064] Figure 14 Schematic diagram of the volume of the convex arc rotation body V3 in the air chamber of the air spring when the relative compression stroke is z in an embodiment of the present invention;

[0065] Figure 15 Schematic diagram of the volume of the standard rotating body V4 in the air spring chamber when the relative compression stroke is z in an embodiment of the present invention;

[0066] Figure 16 Schematic diagram of the volume of the concave arc rotation body V5 in the air chamber of the air spring when the relative compression stroke is z in an embodiment of the present invention. DETAILED DESCRIPTION

[0067] We are going to design a double piston diaphragm air spring for an installation space with a height of 268 mm. The design requirements of the air spring are as follows:

[0068] ①The vertical design height is 268mm;

[0069] ②The design load is 11063N, the vertical design stiffness is 83N / mm, and the maximum design diameter is 175mm;

[0070] ③The ultimate tensile displacement is 45.8mm, and the ultimate compressive displacement is -47.6mm;

[0071] ④ At the extreme compression / extension stroke, the air spring deflection angle threshold is -15.4° to 14.9°;

[0072] ⑤The blasting pressure is greater than 4MPa.

[0073] The following are examples of the method according to the present invention:

[0074] like Figure 4 As shown, a key parameter design method for a dual-piston diaphragm air spring includes the following steps:

[0075] 1) The length of the first piston mounting post is determined based on the vertical design height of the air spring and the relative compression stroke threshold, and the length of the second piston mounting post is determined based on the relative compression stroke threshold and the yaw angle threshold required by the air spring design:

[0076] For example, the vertical design height of the air spring is 268mm, and the relative compression stroke threshold of the air spring is in the range of -47.6mm to 45.8mm (that is, the upper limit of the relative compression stroke is 45.8mm, and the lower limit of the relative compression stroke is -47.6mm). Using CATIA for vertical space simulation design, it can be concluded that the length of the first piston mounting column should be in the range of 80 to 200mm, and the performance of the air spring can meet the design requirements.

[0077] Similarly, when the relative compression stroke threshold of the air spring is in the range of -47.6mm to 45.8mm, and the yaw angle threshold range is in the range of -15.4° to 14.9°, the yaw motion simulation design using ABAQUS software shows that the performance of the air spring can meet the design requirements when the length of the second piston mounting column is in the range of 30 to 70mm.

[0078] The length ratio of the first piston mounting column to the second piston mounting column is 2:1 to 4:1. Combined with the comprehensive simulation of the vertical design height, the deflection angle threshold, and the relative compression stroke threshold of the air spring, it is finally concluded that in this embodiment, the length of the first piston mounting column is 118 mm, and the design value of the length of the second piston mounting column is 51 mm.

[0079] 2) Based on the design load of the air spring and the pressure threshold of the air spring chamber (1MPa, that is, the maximum pressure of the air spring chamber under the design load cannot exceed 1MPa), and taking into account the movement space of the bladder skin between the first piston and the casing, determine the design diameter of the first piston and the design value of the pressure of the air spring chamber under the design load. The specific formula is as follows:

[0080] F c (0)=π[R e (0)] 2 [P(0)-P d ]

[0081] Where, F c (0) is the design load of the air spring, π is the circumference of the circle, R e (0) is the design diameter of the first piston, P(0) is the pressure of the air spring chamber under the design load, P d is atmospheric pressure.

[0082] Calculation shows that in this embodiment, the design diameter of the first piston is 102 mm, and the pressure of the air spring chamber under the design load is 0.95 MPa.

[0083] 3) Based on the vertical design stiffness required by the air spring design and the principle of constant suspension frequency deviation, the overall shape of the first piston is designed. From this, the minimum diameter of the first piston can be determined, and the total volume of the air spring chamber under the design load can also be determined. The specific formula is as follows:

[0084]

[0085] R 差 =R0-R e (z)

[0086]

[0087] V(z)=V1+V2(z)+V3(z)-V4(z)-V5(z)

[0088]

[0089]

[0090] Where K is the vertical design stiffness of the membrane air spring, π is the circumference, z is the relative compression stroke of the air spring, R e (z) is the effective radius of the air spring chamber when the relative compression stroke is equal to z, R ’ e (z) is R e (z), P(0) is the pressure of the air spring chamber under the design load, V(0) is the volume of the air spring chamber under the design load, V(z) is the volume of the air spring chamber when the relative compression stroke is equal to z, V1 is the volume of the air spring chamber that does not change with the change of the relative compression stroke, V2(z) is the volume of the cylinder V2 when the relative compression stroke is z, V3(z) is the volume of the convex arc rotating body V3 when the relative compression stroke is z, V4(z) is the volume of the standard rotating body V4 when the relative compression stroke is z, V5(z) is the volume of the concave arc rotating body V5 when the relative compression stroke is z, h(z) is the height of the cylinder V2 when the relative compression stroke is z, P d is the atmospheric pressure, R0 is the inner radius of the shell, R s (h) is the function of piston radius, is the piston radius when the air spring compression stroke is z, for The first derivative of R 差 is the difference between the inner radius of the housing and the effective radius of the air spring chamber, H is the distance between the upper end face of the second piston and the top of the air spring when the relative compression displacement is 0, i is the vertical distance between the lowest point of the contact surface between the rubber airbag and the piston and the upper end face of the second piston when the relative compression displacement is 0, V e ’(z) is the rate of change of the air spring chamber volume.

[0091] In fact, the overall shape of the first piston is based on the piston radius function R s (h) is determined. When designing the overall shape of the first piston, in order to ensure vertical stiffness and leave enough space for the bladder skin to move between the air spring outer sleeve and the first piston, to avoid the piston rod or piston abutting the bladder skin, and to ensure the durability of the bladder skin, the maximum cross-sectional diameter of the first piston should be 50 to 80 mm smaller than the maximum design diameter of the air spring, and the volume of the air spring chamber is about 2L to 3.5L. Calculated by the MATLAB simultaneous equations, it can be seen that the maximum cross-sectional diameter of the first piston is 95 to 125 mm, the minimum diameter of the first piston in this embodiment is 92±5 mm, the wall thickness of the first piston is 4 to 15 mm, and the volume of the air spring chamber under the design load is 2.6L. After simulation experiments, it was finally obtained that the design value of the maximum cross-sectional diameter of the first piston is 112 mm, the minimum diameter of the first piston is 92 mm, the wall thickness of the first piston at the maximum cross-sectional area is 14 mm, the wall thickness of the first piston at the minimum cross-sectional area is 4 mm, and the wall thickness of the first piston at the design diameter is 9 mm. Finally, the piston radius function R s (h) Determine the overall shape of the first piston.

[0092] It is worth noting that Figure 12 As shown, the volume V1 of the air spring chamber in this embodiment that does not change with changes in the relative compression stroke includes four parts: V1-1, V1-2, V1-3, and V1-4. V1-1 is the volume of the blind hole cavity of the first piston mounting post 12, and V1-4 is the volume of the blind hole cavity of the second piston mounting post 13. These are the parts that do not change with changes in the relative compression stroke. Although V1-2 and V1-4 do change with changes in the relative compression stroke, the sum of the volumes of these two parts barely changes. Therefore, the volume of V1 can be considered to be unchanged with changes in the relative compression stroke, and has little impact on the final result. V2(z) is the volume of the cylinder V2 when the relative compression stroke is z, V3(z) is the volume of the convex arc rotation body V3 when the relative compression stroke is z, V4(z) is the volume of the standard rotation body V4 when the relative compression stroke is z, and V5(z) is the volume of the concave arc rotation body V5 when the relative compression stroke is z. Among them, the cylinder V2, the convex arc rotation body V3, the standard rotation body V4, and the concave arc rotation body V5 are as follows: Figures 13 to 16As shown in the figure, the volume of these parts of the air chamber will change with the change of the relative compression stroke. By calculating the volume between several parts, it can be known that the volume of the air spring chamber when the relative compression stroke is equal to z is V(z)=V1+V2(z)+V3(z)-V4(z)-V5(z).

[0093] 4) After the overall shape of the first piston is determined, the cross-sectional diameter of the first piston mounting post is determined based on the minimum diameter of the first piston;

[0094] In order to take the pressure resistance of the entire piston into consideration and ensure that the air spring has sufficient life and will not be shortened due to insufficient durability of the piston, Abaqus can be used to simulate the design of the cross-sectional diameter of the first piston mounting post under the premise of "8 to 20 mm smaller than the minimum diameter of the first piston" until an accurate size that meets the requirements of use is obtained. The maximum design diameter of the air spring in this embodiment is 175 mm, the minimum diameter of the first piston is 92 mm, and the cross-sectional diameter of the first piston mounting post should be within the range of 84 ± 5 ​​mm. Abaqus simulation found that when the minimum diameter of the first piston is 92 mm, the cross-sectional diameter of the first piston mounting post is 84 mm, the performance of the air spring is the best, and the piston will not come into contact with the bladder skin. Therefore, the design value of the cross-sectional diameter of the first piston mounting post in this embodiment is 84 mm.

[0095] It should be noted that, in this embodiment, the cross-section of the piston is annular, and the diameter of the maximum cross-section refers to the diameter of the outer circle of the annular ring.

[0096] 5) After determining the diameter of the maximum cross section of the air spring according to the suspension envelope requirements, the cross section diameter of the second piston mounting post is determined based on the diameter of the maximum cross section of the air spring.

[0097] Of course, when designing the cross-sectional diameter of the second piston mounting column, the space requirement for the bladder skin movement between the second piston and the outer casing should also be taken into consideration, leaving enough space for the piston column and the piston to move, so as to avoid the piston or the piston mounting column from contacting the bladder skin during movement. Therefore, the cross-sectional diameter of the second piston mounting column is 70 to 100 mm smaller than the diameter of the maximum cross-sectional area of ​​the air spring. For example, when the diameter of the maximum cross-sectional area of ​​the air spring is 175 mm, the cross-sectional diameter of the second piston mounting column should be within the range of 75 to 105 mm. Using ABAQUS software for yaw motion simulation design, when the design value of the cross-sectional diameter of the second piston mounting column is 90 mm, the air spring has the best performance and will not cause the piston to contact the bladder skin.

[0098] 6) Based on the design value of the cross-sectional diameter of the second piston mounting column and using ABAQUS software to perform strength design of the second piston, the minimum wall thickness value of the second piston is obtained. The minimum diameter of the second piston is the design value of the cross-sectional diameter of the second piston mounting column plus twice the minimum wall thickness of the second piston.

[0099] When the design value of the cross-sectional diameter of the second piston mounting column is 90 mm, the minimum wall thickness of the second piston is 3 mm, so the minimum diameter of the second piston is 96 mm.

[0100] 7) Based on the design rules of the yaw angle contribution of the second piston, the maximum diameter and the overall shape of the second piston are designed by using ABAQUS software for yaw motion simulation.

[0101] When designing the diameter of the maximum cross section of the second piston and the shape of the second piston, since the design rules for the contribution to the deflection angle of the second piston must be met, the maximum cross section diameter of the second piston is 30 to 60 mm smaller than the design value of the diameter at the maximum cross section of the air spring. In this embodiment, the diameter of the maximum cross section of the second piston is 115 to 145 mm. Using ABAQUS software for deflection motion design, it was found that when the maximum design diameter of the air spring is 175 mm, the maximum cross section diameter of the second piston is 140 mm and the maximum wall thickness of the second piston is 25 mm, the air spring has the best performance and will not cause the piston to contact the bladder skin. Therefore, in this embodiment, the design value of the maximum cross section diameter of the second piston is 140 mm, and the design value of the maximum wall thickness of the second piston is 25 mm.

[0102] Finally, based on the design values ​​of the maximum cross-sectional diameter, maximum wall thickness, and minimum wall thickness of the second piston, and the minimum diameter of the second piston, the yaw motion simulation is performed in ABAQUS software to design the entire shape of the second piston, and the design diameter of the second piston under the design load is obtained to be 122 mm.

[0103] After the key parameters of the air spring are designed in the above manner, the other parameters of the air spring can be designed conventionally according to the key parameters. Finally, the following can be obtained: Figure 2The dual-piston diaphragm air spring shown includes a housing 6, an upper mounting base 1 for fixedly connecting to the vehicle body, and a lower mounting base 10 for fixedly connecting to the suspension arm. The upper mounting base 1 is provided with a downwardly extending first piston mounting column 12, on which a first piston 2 is fixedly mounted, and the first piston 2 is threadedly fixed to the first piston mounting column 12. The lower mounting base 10 is provided with an upwardly extending second piston mounting column 13, on which a second piston 8 is fixed, and the second piston 8 is threadedly fixed to the second piston mounting column 13. A space 14 is left between the first piston mounting column 12 and the second piston mounting column 13. Figure 3 As shown. A rubber airbag 5 is disposed between the first piston 2 and the second piston 8. The rubber airbag 5 is located within the housing 6. The upper end of the rubber airbag 5 is fixedly connected to the first piston mounting post 12, and the lower end is fixedly connected to the second piston mounting post 13. The axial length ratio of the first piston mounting post 12 to the second piston mounting post 13 is 2:1 to 4:1, and the axial length of the first piston 2 is the same as that of the first piston mounting post 12, and the axial length of the second piston 8 is the same as that of the second piston mounting post 13. This divides the inner cavity of the air spring into two different upper and lower working areas, each with a different primary task. In this embodiment, the first piston 2 and the second piston 8 have a conical structure, and the taper of the first piston 2 is smaller than that of the second piston 8. The first and second piston mounting posts 12 and 13 are each provided with blind holes. The upper portion of the rubber airbag 5 is fixedly connected to the lower end of the first piston mounting post 12 via a first retaining ring 3, while the lower portion of the rubber airbag 5 is fixedly connected to the upper end of the second piston mounting post 13 via a second retaining ring 9. This seals the rubber airbag 5's skin against the blind holes of each piston mounting post, forming an air chamber. A support ring 7 is located within the rubber airbag 5, securing the rubber airbag 5's skin against the inner wall of the housing 6. The housing 6 is made of aluminum alloy or aluminum-magnesium alloy. Dust covers are provided between the exterior of the housing 6 and both the upper and lower mounting seats 1 and 10. For example, a first dust cover 4 is provided between the exterior of the housing 6 and the upper mounting seat 1, and a second dust cover 11 is provided between the exterior of the housing 6 and the lower mounting seat 10. The material selection for each air spring component is primarily based on a combination of considerations, including protective performance (hardness, ductility, etc.), weight (lightweight), and cost.

[0104] In summary, based on the size of the air spring installation space between the vehicle body and the suspension, as well as the maximum design diameter of the air spring, the key parameters of the dual-piston diaphragm air spring described in this embodiment are as follows:

[0105] a) The length of the first piston mounting post is 118 mm, the cross-sectional diameter of the first piston mounting post is 84 mm, the design value of the maximum cross-sectional diameter of the first piston is 112 mm, the minimum diameter of the first piston is 92 mm, the design diameter of the first piston is 102 mm, and the wall thickness of the first piston is 4 to 15 mm;

[0106] b) The length of the second piston mounting post is 51 mm, the cross-sectional diameter of the second piston mounting post is 90 mm, the design value of the maximum cross-sectional diameter of the second piston is 140 mm, the minimum diameter of the second piston is 96 mm, the design diameter of the second piston is 122 mm, and the wall thickness of the second piston is 3 to 25 mm;

[0107] c) the inner cavity volume of the rubber airbag (5) is 2.6 L, and the inner cavity pressure of the rubber airbag (5) is 0.95 MPa;

[0108] Based on the above key parameters, a dual-piston diaphragm air spring 400 that meets the design requirements was manufactured. In addition, a conventional single-piston diaphragm air spring 500 and a dual-piston rubber air spring 600 with publication number CN204784382U that also meet the design requirements were manufactured using conventional production methods. The main parameters of these springs are shown in the following table:

[0109]

[0110] Table 1

[0111] like Figures 5 to 7 As shown, the dual-piston diaphragm air spring 400 of the present invention, the conventional single-piston diaphragm air spring 500, and the dual-piston rubber air spring 600 with publication number CN204784382U are respectively installed at the same position of the vehicle suspension, and the vehicle body 300 and the suspension control arm 200 are connected by the shock absorber 100, so that the installation space between the vehicle body 300 and the suspension control arm 200 is the same (i.e., the installation height is 268 mm), as shown in FIG. Figures 8 to 10 The yaw angle comparison experiment shown here adjusts the yaw angle of each air spring within the air spring yaw angle threshold range and observes whether the air spring's yaw torque is abnormal. If it suddenly increases, it indicates that the piston is in contact with the bladder skin. The experimental data of this yaw angle comparison experiment is as follows:

[0112]

[0113] Table 2

[0114] As shown in Table 2, the internal pressure of a conventional single-piston diaphragm air spring 500 is 1.12 MPa, exceeding the design standard (typically 1 MPa or less), failing to achieve its design objectives. Furthermore, the entire deflection angle is contributed entirely by the deflection of the single piston. This conventional single-piston diaphragm air spring 500 has a single piston, and its reciprocating, lateral, and deflection motion limits are determined by the space between the piston and the outer aluminum shell. Therefore, conventional single-piston diaphragm air springs 500 can only meet the requirements for high loads and large deflection angles by significantly reducing the piston design diameter and significantly increasing the internal pressure. To meet the reciprocating motion requirements of the suspension, conventional single-piston diaphragm air springs 500 are typically designed with a large piston length. Therefore, if the suspension is suddenly subjected to a large load, resulting in an excessively large deflection angle, the piston mounting post will collide with the inner wall of the rubber airbag. Repeated contact and wear of the rubber airbag inner wall during the suspension's lifting and lowering motion can eventually puncture the rubber airbag inner wall, damaging it and compromising driving safety.

[0115] In the dual-piston rubber air spring 600, published with publication number CN204784382U, 30% of the deflection angle is borne by the first piston, and 70% by the second piston. The upper and lower pistons of this air spring are identical (including length) for the sole purpose of extending the air spring's service life. The use of two pistons reduces the compression and tension limits of the rubber bladder, thereby increasing its service life. In this dual-piston rubber air spring, the upper and lower ends of the rubber bladder can be compressed simultaneously, shortening the upward and downward travel of the bladder during compression and release. This reduces the ultimate load on the rubber bladder skin, mitigates the aging rate of the bladder skin to a certain extent under the same conditions, and ultimately extends the service life of the entire air spring. However, in this air spring, at the extreme tension and compression limits, the second piston will still collide with the bladder skin, which is attached to the outer shell. Repeated collisions can cause the rubber to age and even puncture, shortening the air spring's service life.

[0116] The dual-piston diaphragm air spring 400 of the present invention has an internal pressure of 0.95 MPa, meeting the design standard of 1 MPa or less. Under this premise, more than 85% of the deflection angle is contributed by the second piston, and at the extremes of tension and compression, neither piston will collide with the bladder skin abutting the outer shell. Under the same conditions, the air spring of the present invention has a longer lifespan.

[0117] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications made to the present invention by those skilled in the art without departing from the spirit of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A key parameter design method for a dual-piston diaphragm air spring, characterized in that: The following steps are involved: 1) Determine the length of the first piston mounting post based on the vertical design height of the air spring and the relative compression stroke threshold, and determine the length of the second piston mounting post based on the relative compression stroke threshold and the yaw angle threshold required by the air spring design; 2) determining a design diameter of the first piston and a pressure of the air spring chamber under the design load based on the design load of the air spring and a pressure threshold of the air spring chamber; 3) Based on the vertical design stiffness required by the air spring design and the principle of suspension frequency invariance, the overall shape of the first piston is designed to obtain the minimum diameter of the first piston and the volume of the air spring chamber under the design load; 4) After the overall shape of the first piston is determined, the cross-sectional diameter of the first piston mounting post is determined based on the minimum diameter of the first piston; 5) After determining the diameter of the maximum cross-section of the air spring according to the suspension envelope requirements, the cross-sectional diameter of the second piston mounting post is determined based on the diameter of the maximum cross-section of the air spring; 6) Performing strength design of the second piston based on the design value of the cross-sectional diameter of the second piston mounting post to obtain the minimum wall thickness and minimum diameter of the second piston; 7) Design the maximum diameter and overall shape of the second piston based on the design rules for the second piston's yaw angle contribution; The double-piston diaphragm air spring comprises a housing (6), an upper mounting seat (1) for fixedly connecting to a vehicle body, and a lower mounting seat (10) for fixedly connecting to a suspension swing arm. The upper mounting seat (1) is provided with a first piston mounting column (12) extending downward, and a first piston (2) is fixedly arranged on the first piston mounting column (12). The lower mounting seat (10) is provided with a second piston mounting column (13) extending upward, and a second piston (8) is fixedly arranged on the second piston mounting column (13). A space is left between the first piston mounting column (12) and the second piston mounting column (13). A space spacing (14) is provided between the first piston (2) and the second piston (8), and a rubber airbag (5) is provided between the first piston (2) and the second piston (8). The rubber airbag (5) is located in the housing (6). The upper end of the rubber airbag (5) is fixedly connected to the first piston mounting column (12), and the lower end is fixedly connected to the second piston mounting column (13). The axial length ratio of the first piston mounting column (12) to the second piston mounting column (13) is 2:1 to 4:1, and the axial length of the first piston (2) is the same as that of the first piston mounting column (12), and the axial length of the second piston (8) is the same as that of the second piston mounting column (13).

2. The key parameter design method of the dual-piston diaphragm air spring according to claim 1 is characterized in that: The first piston (2) and the second piston (8) are conical structures, and the taper of the first piston (2) is smaller than the taper of the second piston (8).

3. The key parameter design method of the dual-piston diaphragm air spring according to claim 1 is characterized in that: The first piston mounting column (12) and the second piston mounting column (13) are both provided with blind holes. The upper bladder skin of the rubber airbag (5) is fixedly connected to the lower end of the first piston mounting column (12) via a first buckling ring (3). The lower bladder skin of the rubber airbag (5) is fixedly connected to the upper end of the second piston mounting column (13) via a second buckling ring (9), so that the bladder skin of the rubber airbag (5) and the blind holes of each piston mounting column are sealed to form an air chamber.

4. The key parameter design method of the dual-piston diaphragm air spring according to claim 1 is characterized in that: A support ring (7) is provided inside the rubber airbag (5), and the support ring (7) enables the bladder skin of the rubber airbag (5) to abut against the inner wall of the shell (6).

5. The key parameter design method of the dual-piston diaphragm air spring according to claim 1 is characterized in that: Dust covers are provided between the exterior of the housing (6) and the upper mounting seat (1) and the lower mounting seat (10).

6. The key parameter design method of the dual-piston diaphragm air spring according to claim 1 is characterized in that: The design values ​​of the first piston design diameter and the air spring chamber pressure under the design load are calculated using the following formula: F c (0)=π[R e (0)] 2 [P(0)-P d ] Where, F c (0) is the design load of the air spring, π is the circumference of the circle, R e (0) is the design diameter of the first piston, P(0) is the pressure of the air spring chamber under the design load, P d is atmospheric pressure.

7. The key parameter design method of the dual-piston diaphragm air spring according to claim 1 is characterized in that: The overall shape of the first piston is designed according to the following set of equations, which determine the minimum diameter of the first piston and the volume of the air spring chamber under the design load: R 差 =R0-R e (z) V(z)=V1+V2(z)+V3(z)-V4(z)-V5(z) Where K is the vertical design stiffness of the membrane air spring, π is the circumference, z is the relative compression stroke of the air spring, R e (z) is the effective radius of the air spring chamber when the relative compression stroke is equal to z, R ’ e (z) is R e (z), P(0) is the pressure of the air spring chamber under the design load, V(0) is the volume of the air spring chamber under the design load, V(z) is the volume of the air spring chamber when the relative compression stroke is equal to z, V1 is the volume of the air spring chamber that does not change with the change of the relative compression stroke, V2(z) is the volume of the cylinder V2 when the relative compression stroke is z, V3(z) is the volume of the convex arc rotating body V3 when the relative compression stroke is z, V4(z) is the volume of the standard rotating body V4 when the relative compression stroke is z, V5(z) is the volume of the concave arc rotating body V5 when the relative compression stroke is z, h(z) is the height of the cylinder V2 when the relative compression stroke is z, P d is the atmospheric pressure, R0 is the inner radius of the shell, R s (h) is the function of piston radius, is the piston radius when the air spring compression stroke is z, for The first derivative of R 差 is the difference between the inner radius of the housing and the effective radius of the air spring chamber, H is the distance between the upper end face of the second piston and the top of the air spring when the relative compression displacement is 0, i is the vertical distance between the lowest point of the contact surface between the rubber airbag and the piston and the upper end face of the second piston when the relative compression displacement is 0, V e ’ (z) is the rate of change of the air spring chamber volume.

8. The key parameter design method of the dual-piston diaphragm air spring according to claim 1 is characterized in that: The cross-sectional diameter of the first piston mounting column is 8-20 mm smaller than the minimum diameter of the first piston, and the cross-sectional diameter of the second piston mounting column is 70-100 mm smaller than the maximum cross-sectional diameter of the air spring.

9. The key parameter design method of the dual-piston diaphragm air spring according to claim 1 is characterized in that: The maximum cross-sectional diameter of the first piston is 50 to 80 mm smaller than the maximum cross-sectional diameter of the air spring, and the maximum cross-sectional diameter of the second piston is 30 to 60 mm smaller than the maximum cross-sectional diameter of the air spring.

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