A leaf spring air bag composite suspension system and vehicle

Abstract

This invention relates to a leaf spring airbag composite suspension system and a vehicle. The system includes a three-axle airbag system, comprising an air reservoir, a height valve, a pressure limiting valve, an overflow valve, and airbags disposed on both sides of the three axles. The air reservoir supplies gas to the airbags, and its outlet is connected to the inlet of the pressure limiting valve. The pressure limiting valve controls and changes the output gas pressure of the air reservoir, and its outlet is connected to the inlet of the height valve. The height valve adjusts the balance and height of the airbags on both sides of the three axles, and its outlet is connected to the airbags. The overflow valve works in conjunction with the pressure limiting valve to release gas when the airbag gas pressure exceeds an overflow pressure threshold, thereby maintaining a constant airbag gas pressure. The inlet of the overflow valve is connected to the airbags, and its outlet is connected to the outside air. The system based on this invention can solve the problems of poor axle load control and overload protection.

Description

Technical Field

[0001] This invention belongs to the field of vehicle manufacturing technology, specifically relating to a leaf spring airbag composite suspension system and a vehicle. Background Technology

[0002] With the continuous development of the transportation industry, three-axle vehicles, which have greater load capacity and higher operating economy compared to two-axle vehicles, are increasingly favored by the market.

[0003] Currently, most three-axle vehicles use suspension control systems with full leaf springs or full airbags. However, the full airbag suspension control system has a complex structure and high cost. The overlapping leaf spring supports in the full leaf spring suspension control system are not conducive to the overall vehicle layout. To address the problems of the full leaf spring or full airbag suspension control system, a leaf spring-airbag composite suspension control system has emerged in existing vehicles. In this composite suspension control system, the airbag and leaf spring are set on the same axle, and the airbag is controlled by a single height valve. However, in the single height valve suspension control system, the height valve is used to maintain the horizontal relationship of the airbag and cannot adjust the airbag height as needed. Moreover, the airbag pressure changes linearly, making it impossible to achieve axle load control and overload protection of the airbag suspension as needed, resulting in poor axle load control and overload protection effects. Summary of the Invention

[0004] This invention provides a leaf spring airbag composite suspension system and vehicle to solve the problem that the existing technology cannot achieve axle load control and overload protection of airbag suspension as needed, resulting in poor axle load control and overload protection effects.

[0005] To solve the above-mentioned technical problems, the present invention provides a leaf spring airbag composite suspension system, including a three-axle airbag system. The three-axle airbag system includes an air storage device, a height valve, a pressure limiting valve, an overflow valve, and airbags disposed on both sides of the three axles.

[0006] The gas storage device is used to supply gas to the airbag, and the outlet of the gas storage device is connected to the inlet of the pressure relief valve.

[0007] The pressure relief valve is used to control and change the output gas pressure of the gas storage device. The outlet of the pressure relief valve is connected to the inlet of the height valve.

[0008] The height valve is used to adjust the balance and height of the airbags on both sides of the three bridges. The air outlet of the height valve is connected to the airbag.

[0009] The overflow valve works in conjunction with the pressure relief valve to release gas when the airbag gas pressure exceeds the overflow pressure threshold, so as to maintain the airbag gas pressure constant. The air inlet of the overflow valve is connected to the airbag, and the air outlet of the overflow valve is connected to the outside air.

[0010] The beneficial effects of the above technical solution are as follows: For the composite suspension system of two-axle leaf springs and three-axle airbags, the airbag suspension balance is maintained by a height valve, gas is released by an overflow valve and controlled in conjunction with a pressure limiting valve to achieve maximum load on the three axles, and the gas pressure output by the gas storage device is controlled by the pressure limiting valve. In this case, the overflow of airbag gas is controlled by the coordinated control of the height valve, pressure limiting valve and overflow valve, thereby enabling the airbag height to be adjusted as needed and the pressure change of the airbag to be controlled as needed. This better achieves axle load control and overload protection of the airbag suspension, and solves the problem that the existing technology cannot achieve axle load control and overload protection of the airbag suspension as needed, resulting in poor axle load control and overload protection effects.

[0011] Furthermore, in order to better achieve axle load control and overload protection, the present invention provides a leaf spring airbag composite suspension system, which also includes the overflow pressure threshold calculated based on the full load axle load of the three axles, the full load axle load of the two axles, the unsprung load of the three axles, and the effective cross section of the three axles airbags.

[0012] Furthermore, to better achieve axle load control and overload protection, this invention provides a leaf spring airbag composite suspension system, which also includes an overflow pressure threshold that satisfies:

[0013]

[0014] Where P2 is the overflow pressure threshold, M 31 For the three bridges under full axle load, M 21 For the full load axle load of the second bridge, M 32 S represents the unsprung load of the three-bridge airbag, and S represents the effective cross-section of the three-bridge airbag.

[0015] Furthermore, in order to better achieve axle load control and overload protection, the present invention provides a leaf spring airbag composite suspension system, which also includes a pressure limiting valve that controls and changes the output gas pressure of the air storage device by using a set pressure limiting threshold value, wherein the pressure limiting threshold value is obtained by using an overflow pressure threshold value.

[0016] Furthermore, to better achieve axle load control and overload protection, this invention provides a leaf spring airbag composite suspension system, which also includes a pressure limiting threshold that satisfies:

[0017] P2-P1≤0.3bar

[0018] Where P1 is the pressure limiting threshold and P2 is the overflow pressure threshold.

[0019] The present invention also provides a vehicle, including a vehicle body and a leaf spring airbag composite suspension system disposed on the vehicle body;

[0020] The leaf spring airbag composite suspension system includes a two-axle leaf spring system, a three-axle airbag system and a controller. The three-axle airbag system includes an air storage device, a height valve, a pressure limiting valve, an overflow valve, and airbags located on both sides of the three axles.

[0021] The gas storage device is used to supply gas to the airbag, and the outlet of the gas storage device is connected to the inlet of the pressure relief valve.

[0022] The pressure relief valve is used to control and change the output gas pressure of the gas storage device. The outlet of the pressure relief valve is connected to the inlet of the height valve.

[0023] The height valve is used to adjust the balance and height of the airbags on both sides of the three bridges. The air outlet of the height valve is connected to the airbag.

[0024] The overflow valve works in conjunction with the pressure relief valve to release gas when the airbag gas pressure exceeds the overflow pressure threshold, so as to maintain the airbag gas pressure constant. The air inlet of the overflow valve is connected to the airbag, and the air outlet of the overflow valve is connected to the outside air.

[0025] The controller is connected to the gas storage device, height valve, pressure relief valve and overflow valve.

[0026] Furthermore, in order to better achieve axle load control and overload protection, the present invention provides a vehicle, which also includes the overflow pressure threshold calculated based on the full load axle load of the three axles, the full load axle load of the two axles, the unsprung load of the three axles, and the effective cross-section of the three axles airbags.

[0027] Furthermore, to better achieve axle load control and overload protection, the present invention provides a vehicle that also includes an overflow pressure threshold that satisfies:

[0028]

[0029] Where P2 is the overflow pressure threshold, M 31 For the three bridges under full axle load, M 21 For the full load axle load of the second bridge, M 32 S represents the unsprung load of the three-bridge airbag, and S represents the effective cross-section of the three-bridge airbag.

[0030] Furthermore, in order to better achieve axle load control and overload protection, the present invention provides a vehicle that also includes a pressure relief valve that controls and changes the output gas pressure of the gas storage device by using a set pressure relief threshold, wherein the pressure relief threshold is obtained by using an overflow pressure threshold.

[0031] Furthermore, to better achieve axle load control and overload protection, the present invention provides a vehicle that also includes a pressure limiting threshold that satisfies:

[0032] P2-P1≤0.3bar

[0033] Where P1 is the pressure limiting threshold and P2 is the overflow pressure threshold. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the leaf spring airbag composite suspension system of the present invention;

[0035] Figure 2 This is a flowchart of the control method for the leaf spring airbag composite suspension system of the present invention;

[0036] Figure 3 It is a graph showing the axle load of the two-bridge and the axle load of the three-bridge. Detailed Implementation

[0037] The basic concept of this invention is as follows: For a composite suspension system with two leaf springs and three airbags, the airbag suspension balance is maintained by a height valve, gas is released by an overflow valve and controlled by a pressure limiting valve to achieve maximum load on the three axles, and the gas pressure output by the gas storage device is controlled by the pressure limiting valve. In this case, by using the coordinated control of the height valve, pressure limiting valve and overflow valve, the overflow of gas in the airbag is controlled, so that the airbag height can be adjusted as needed and the pressure change of the airbag can be controlled as needed, thereby better realizing axle load control and overload protection of the airbag suspension.

[0038] To make the objectives, technical solutions, and technical effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Vehicle Example:

[0040] Figure 1 This is a schematic diagram of the leaf spring airbag composite suspension system of the present invention. Figure 2 This is a flowchart of the control method for the leaf spring airbag composite suspension system of the present invention. Figure 3 It is a graph showing the axle load of the two-bridge and the axle load of the three-bridge.

[0041] This embodiment provides a vehicle. The vehicle includes a vehicle body and a leaf spring airbag composite suspension system mounted on the vehicle body.

[0042] In this embodiment, the leaf spring-airbag composite suspension system includes a two-axle leaf spring system, a three-axle airbag system, and a controller. The two-axle leaf spring system is a full leaf spring suspension system. The three-axle airbag system is a full airbag suspension system.

[0043] In this embodiment, as Figure 1 As shown, the three-bridge airbag system includes an air storage device 1, a pressure limiting valve 2, a height valve 4, an overflow valve, and airbags located on both sides of the three bridges.

[0044] In this embodiment, the gas storage device 1 is used to supply gas to the airbag. The outlet of the gas storage device 1 is connected to the inlet of the pressure relief valve 2. Specifically, the gas storage device 1 is used to store gas. The gas in the gas storage device 1 enters the airbag via the pressure relief valve 2 and the height valve 4. The gas storage device 1 is, for example, a gas cylinder.

[0045] In this embodiment, the pressure limiting valve 2 is used to control and change the output gas pressure of the gas storage device 1. The outlet of the pressure limiting valve 2 is connected to the inlet of the height valve 4. Specifically, the pressure limiting valve 2 is set with a pressure limiting threshold, denoted by P1. After receiving gas from the gas storage device 1, the gas inlet of the pressure limiting valve 2 is controlled and changed internally, resulting in the output of gas with a pressure value of P1 at the outlet of the pressure limiting valve 2. The gas output from the outlet of the pressure limiting valve 2 enters the air bladder via the height valve 4. The pressure value at the outlet of the pressure limiting valve 2 is less than the pressure value at the inlet. That is, the pressure limiting valve 2 controls and changes the output gas pressure of the gas storage device 1 using the set pressure limiting threshold.

[0046] In this embodiment, the pressure limiting threshold is obtained using the overflow pressure threshold (described later). The pressure limiting threshold satisfies:

[0047] P2-P1≤0.3bar

[0048] Where P1 is the pressure limiting threshold and P2 is the overflow pressure threshold. 0.3 bar is obtained based on the airbag overflow volume and the change in the arc height of the secondary axle leaf spring. Specifically, if the pressure limiting threshold P1 rises to the overflow pressure threshold P2, the change in the arc height of the secondary axle leaf spring (H2-H1) is less than the total change in the arc height of the secondary axle leaf spring under full load. Here, H1 is the arc height of the leaf spring when the airbag pressure reaches the pressure limiting threshold P1, and H2 is the arc height of the leaf spring when the airbag pressure reaches the overflow pressure threshold P2.

[0049] In this embodiment, the airbag includes a first airbag 51 and a second airbag 52 disposed on both sides of the three bridges. Figure 1 As shown, the first airbag 51 and the second airbag 52 are respectively connected to different air outlets of the altitude valve 4. The first airbag 51 and the second airbag 52 respectively receive gas from the corresponding air outlet of the altitude valve 4.

[0050] The first airbag 51 is connected to the first overflow valve 31. The second airbag 52 is connected to the second overflow valve 32. When the pressure in the first airbag 51 or the second airbag 52 exceeds the overflow pressure threshold, gas is released through the first overflow valve 31 or the second overflow valve 32 respectively, thereby preventing the airbag from being damaged by excessive gas pressure.

[0051] In this embodiment, the height valve 4 is used to adjust the balance and height of the first airbag 51 and the second airbag 52 on both sides of the three-bridge structure. The height valve 4 includes a first air outlet and a second air outlet. The first air outlet is connected to the first airbag 51. The second air outlet is connected to the second airbag 52.

[0052] In this embodiment, the height valve 4 enables axle load distribution (i.e., pressure distribution) of the airbag. Specifically, the height valve 4 includes a rocker arm, which distributes gas to different outlets of the height valve 4 by swinging the rocker arm, thereby allowing gas to enter the corresponding airbag through different outlets and thus controlling the height of the airbag. When unloaded, the height valve 4 controls the unloaded axle load by calibrating the three-bridge unloaded airbag pressure P. When the airbag pressure reaches the pressure limit valve value, the height valve 4 can no longer inflate the airbag.

[0053] In this embodiment, the overflow valve works in conjunction with the pressure relief valve 2 to release gas when the airbag gas pressure exceeds the overflow pressure threshold, thereby maintaining the maximum airbag gas pressure (i.e., maximum load) constant. This enables overload protection for the three axles, reducing the risk of tire blowouts caused by overload.

[0054] In this embodiment, the air inlet of the overflow valve is connected to the airbag, and the air outlet of the overflow valve is connected to the outside air. Specifically, as shown... Figure 1 As shown, the overflow valve includes a first overflow valve 31 and a second overflow valve 32. The air inlet of the first overflow valve 31 is connected to the first airbag 51, and the air outlet of the first overflow valve 31 is connected to the outside air. The air inlet of the second overflow valve 32 is connected to the second airbag 52, and the air outlet of the second overflow valve 32 is connected to the outside air.

[0055] In this embodiment, the overflow pressure threshold of the overflow valve is calculated based on the full load axle load of the three-bridge, the full load axle load of the two-bridge, the unsprung load of the three-bridge, and the effective cross-section of the three-bridge airbag using the axle load control principle.

[0056] First, the principle of axle load control will be introduced. The principle of axle load control satisfies:

[0057] M2:M3=M2:(2PS+M 32 (1)

[0058] Where M2 is the unloaded axle load of the second axle, M3 is the unloaded axle load of the third axle, P is the unloaded airbag pressure of the third axle, S is the effective cross-section of the airbag of the third axle, and M 32 The unsprung mass of the three bridges.

[0059] Since the overflow pressure threshold P2 is equal to the airbag pressure when the three axles are under maximum load, the airbag pressure overflows through the overflow valve after the three axles are overloaded, thus preventing the three axles from being overloaded. Therefore, the no-load parameter in equation (1) is replaced with the full-load parameter, resulting in:

[0060] M 21 :M 31 =M 21 :(2P2S+M 32 (2)

[0061] Among them, M 21 For the full load axle load of the second bridge, M 31 P1 represents the full load axle load of the three axles, and P2 represents the overflow pressure threshold.

[0062] After transforming equation (2), the overflow pressure threshold is obtained, which satisfies the following:

[0063]

[0064] In this embodiment, the pressure limiting valve 2, the overflow valve, and the height valve 4 constitute the control unit of the three-axle airbag system. The height valve 4 maintains the airbag suspension balance, the overflow valve controls the maximum load on the three axles, and the pressure limiting valve 2 controls the airbag gas overflow rate. Without the pressure limiting valve 2 for pressure limiting protection, the overflow valve would remain in an overflowing state after the vehicle is overloaded, wasting the vehicle's air supply. Therefore, adding the pressure limiting valve 2 saves energy. In this case, the overflow valve and the pressure limiting valve 2 can work together based on the pressure difference to control the airbag overflow rate and the three-axle airbag pressure, thereby achieving three-axle axle load control and overload protection functions.

[0065] In this embodiment, as Figure 2 As shown, the working process of the control unit, which consists of a pressure relief valve, a relief valve, and a height valve, is as follows:

[0066] When unloaded, the height valve controls the airbag height based on a set height value. As the load increases, the gas pressure in the airbag (i.e., the airbag pressure) continuously increases. When the gas pressure in the airbag reaches the pressure limit valve value, the pressure limit protection function activates. At this point, the height valve can no longer inflate the airbag, and the airbag pressure increase slows down. When the airbag pressure reaches the overflow pressure threshold, the airbag is fully loaded. If the airbag pressure continues to increase and exceeds the overflow pressure threshold, the airbag is overloaded, and the overload protection function activates. At this point, the overflow valve begins to overflow to keep the airbag load constant. Simultaneously, the pressure limit valve's pressure limit protection reduces the gas overflow flow, ensuring that the overflow valve does not overflow continuously. This reduces the load after overload and maintains balance. If the load decreases, the height valve adjusts the airbag height to reduce the airbag pressure.

[0067] In this embodiment, for example, the unloaded ratio of the second and third axles of the vehicle is M2:M3 = 5:1, and the full load ratio of the second and third axles of the vehicle is M... 21 :M 31=10:3. Under no-load conditions, the no-load axle load control is achieved by calibrating the no-load airbag pressure P value of the three axles, reaching M2:M3 = 5:1. Under full load conditions, the overflow pressure threshold P2 can be set, and the pressure limiting threshold P1 can be set to P2 - 0.3 bar, allowing the vehicle to achieve M2:M3 = 5:1. 21 :M 31 With an axle load control requirement of 10:3, when the pressure reaches the pressure limit valve, the height valve can no longer inflate the airbag, the airbag pressure increase slows down, and the overflow valve begins to overflow after overload. The pressure limit valve's pressure-limiting protection minimizes the gas overflow, ensuring the overflow valve does not overflow continuously, thereby controlling the axle load to reach full load (M). 21 :M 31 =10:3. The axle load increase curves for the second and third bridges are as follows: Figure 3 As shown, Figure 3 Curve a in the diagram represents the load on a two-bridge axle, and curve b represents the load on a three-bridge axle. Based on Figure 3 It can be seen that the axle load of the second and third bridges increases with the increase of pressure, while the axle load of the third bridge tends to slow down and become more moderate thereafter.

[0068] In this embodiment, the controller is connected to the gas storage device 1. The controller controls and modulates the output gas pressure value of the gas storage device 1.

[0069] In this embodiment, the controller is connected to the height valve 4.

[0070] In this embodiment, the controller is connected to the pressure relief valve 2. The controller adjusts the pressure relief valve value using the overflow pressure threshold.

[0071] In this embodiment, the controller is connected to the overflow valve. The controller adjusts and changes the overflow pressure threshold of the overflow valve based on the different needs of different vehicles. Specifically, the controller is connected to the first overflow valve 31 and the second overflow valve 32 respectively to control the overflow pressure threshold of the first overflow valve 31 and the second overflow valve 32 respectively.

[0072] The vehicles in this embodiment include, but are not limited to, traditional buses, new energy buses, and trucks.

[0073] Based on the vehicle in this embodiment, for the composite suspension system of two-axle leaf springs and three-axle airbags, the airbag suspension balance is maintained by a height valve, gas is released by an overflow valve and controlled in conjunction with a pressure limiting valve to control the maximum load on the three axles, and the gas pressure output by the gas storage device is controlled by the pressure limiting valve. In this case, the cost of the mechanical control system is reduced by the coordinated control of the height valve, pressure limiting valve and overflow valve, and the overflow of airbag gas is controlled. This allows the airbag height to be adjusted as needed and the pressure change of the airbag to be controlled as needed, thereby better realizing the axle load control and overload protection of the airbag suspension. This solves the problem in the prior art that the axle load control and overload protection of the airbag suspension cannot be realized as needed, resulting in poor axle load control and overload protection effects.

[0074] Example of a leaf spring airbag composite suspension system:

[0075] This embodiment also provides a leaf spring airbag composite suspension system. The leaf spring airbag composite suspension system includes a three-axle airbag system. The three-axle airbag system includes an air storage device, a height valve, a pressure limiting valve, an overflow valve, and airbags disposed on both sides of the three axles. Specific details of the three-axle airbag system can be found in the corresponding description in the vehicle embodiment, and will not be repeated here. Based on this embodiment, the leaf spring airbag composite suspension system utilizes the coordinated control of the height valve, pressure limiting valve, and overflow valve to control the overflow of airbag gas. This allows for on-demand adjustment of the airbag height and on-demand control of airbag pressure changes, thereby better achieving axle load control and overload protection of the airbag suspension. This solves the problem in the prior art where on-demand axle load control and overload protection of the airbag suspension cannot be achieved, resulting in poor axle load control and overload protection effects.

Claims

1. A leaf spring airbag composite suspension system, characterized in that, It includes a two-axle leaf spring system and a three-axle airbag system. The three-axle airbag system includes an air storage device, a height valve, a pressure limiting valve, an overflow valve, and airbags located on both sides of the three axles. The gas storage device is used to supply gas to the airbag, and the outlet of the gas storage device is connected to the inlet of the pressure relief valve. The pressure relief valve is used to control and change the output gas pressure of the gas storage device using the pressure relief valve value P1. The outlet of the pressure relief valve is connected to the inlet of the height valve. The height valve is used to adjust the balance and height of the airbags on both sides of the three bridges. The air outlet of the height valve is connected to the airbag. The overflow valve works in conjunction with the pressure relief valve to release gas when the airbag gas pressure exceeds the overflow pressure threshold P2, thereby maintaining a constant airbag gas pressure. The air inlet of the overflow valve is connected to the airbag, and the air outlet of the overflow valve is connected to the outside air. P2-P1≤P0, where P0 is based on the airbag overflow volume and the change in the arc height of the second axle leaf spring. This ensures that when P1 rises to P2, the change in the arc height of the second axle leaf spring is less than the total change in the arc height of the second axle leaf spring under full load, thus meeting the requirements for the full load axle load ratio of the second and third axles when the vehicle is fully loaded.

2. The leaf spring airbag composite suspension system according to claim 1, characterized in that, The overflow pressure threshold is calculated based on the full load axle load of the three-axle bridge, the full load axle load of the two-axle bridge, the unsprung load of the three-axle bridge, and the effective cross-section of the airbag of the three-axle bridge.

3. The leaf spring airbag composite suspension system according to claim 2, characterized in that, The overflow pressure threshold must satisfy: Where P2 is the overflow pressure threshold. M 31 For the three bridges at full axle load, M 21 For the second bridge at full load axle load, M 32 For the three-bridge underspring load, S This is the effective cross-section of the three-bridge airbag.

4. The leaf spring airbag composite suspension system according to claim 1, characterized in that, The overflow pressure threshold is equal to the airbag pressure when the three axles are under maximum load.

5. The leaf spring airbag composite suspension system according to claim 1, characterized in that, P0 = 0.3 bar.

6. A vehicle, characterized in that, include: The vehicle body and the leaf spring airbag composite suspension system mounted on the vehicle body; The leaf spring airbag composite suspension system includes a two-axle leaf spring system, a three-axle airbag system and a controller. The three-axle airbag system includes an air storage device, a height valve, a pressure limiting valve, an overflow valve, and airbags located on both sides of the three axles. The gas storage device is used to supply gas to the airbag, and the outlet of the gas storage device is connected to the inlet of the pressure relief valve. The pressure relief valve is used to control and change the output gas pressure of the gas storage device using the pressure relief valve value P1. The outlet of the pressure relief valve is connected to the inlet of the height valve. The height valve is used to adjust the balance and height of the airbags on both sides of the three bridges. The air outlet of the height valve is connected to the airbag. The overflow valve works in conjunction with the pressure relief valve to release gas when the airbag gas pressure exceeds the overflow pressure threshold P2, so as to maintain the airbag gas pressure constant. The air inlet of the overflow valve is connected to the airbag, and the air outlet of the overflow valve is connected to the outside air. P2-P1≤P0, where P0 is based on the airbag overflow volume and the arc height change of the second axle leaf spring, so that when P1 rises to P2, the arc height change of the second axle leaf spring is less than the total arc height change of the second axle leaf spring under full load, which meets the requirements of the full load axle load ratio of the second and third axles when the vehicle is fully loaded. The controller is connected to the gas storage device, height valve, pressure relief valve and overflow valve.

7. The vehicle according to claim 6, characterized in that, The overflow pressure threshold is calculated based on the full load axle load of the three-axle bridge, the full load axle load of the two-axle bridge, the unsprung load of the three-axle bridge, and the effective cross-section of the airbag of the three-axle bridge.

8. The vehicle according to claim 7, characterized in that, The overflow pressure threshold must satisfy: Where P2 is the overflow pressure threshold. M 31 For the three bridges at full axle load, M 21 For the second bridge at full load axle load, M 32 For the three-bridge underspring load, S This is the effective cross-section of the three-bridge airbag.

9. The vehicle according to claim 6, characterized in that, The overflow pressure threshold is equal to the airbag pressure when the three axles are under maximum load.

10. The vehicle according to claim 6, characterized in that, P0 = 0.3 bar.

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