Closed air suspension fine tuning system and method with balance air tank

Abstract

The application relates to a closed air suspension fine leveling system with a balance tank and a method, and relates to the technical field of vehicle air suspension systems and vehicle body height control, which comprises an air spring, a main tank, a balance tank, a balance control valve, a detection unit and a suspension controller, wherein the detection unit comprises a pressure detection unit and a height detection unit; the balance tank is selectively communicated with the air spring branch through the balance control valve, thereby forming a fine leveling gas circuit independent of the main tank large-flow regulation passage; the suspension controller controls the balance control valve to perform short-time communication, so that small-flow gas transfer is generated between the air spring and the balance tank, thereby realizing pressure rebalancing and residual stress release of the air spring. The application realizes high-precision fine leveling of air spring residual internal stress release and vehicle body posture, significantly reduces leveling noise, energy consumption and valve group wear, and improves system availability and user perception stability.

Description

Technical Field

[0001] This application relates to the field of vehicle air suspension systems and vehicle height control technology, specifically to a balance air tank, fine-tuning air circuit, and control method for a closed air suspension system. Background Technology

[0002] With the increasing demands for vehicle comfort, air suspension systems have been widely adopted in various passenger and commercial vehicles. An air suspension system typically includes air springs, an air supply unit (ASU), a main air tank, an air distribution valve assembly, a height sensor, a pressure sensor, and a suspension controller. Based on the gas circulation method, air suspension systems can be divided into open and closed systems. Closed air suspension systems typically do not directly vent the air from the air springs to the outside atmosphere; instead, they recover and recycle the air through the main air tank, compressor, and valve assembly, offering advantages such as low energy consumption and good environmental performance.

[0003] In a closed air suspension system, after vehicle height adjustment, the actual pressure of the air springs is affected not only by the inflation / deflation volume but also by a combination of factors, including vehicle load, wheel end constraints, road surface excitation, temperature changes, air spring rubber deformation, bracket friction, suspension bushing preload, and the vehicle lifting and lowering process. Therefore, in actual vehicles, a completely stable static equilibrium state is not immediately achieved after height adjustment; residual internal stress may exist within the air springs, or uneven pressure may occur at the four corners.

[0004] After a vehicle is raised and lowered, traversing uneven terrain, experiencing unilateral compression and rebound, or after prolonged parking, the pressure of the four corner air springs and the vehicle height may exhibit unexpected drift. This typically manifests as the vehicle height at one corner or axle being higher or lower than normal, an increased left-right height difference, and an uneven vehicle posture. In severe cases, the height error can exceed 10mm. These phenomena not only affect the user's perception of the vehicle's leveling function but may also cause problems such as vehicle swerving, reduced posture maintenance, or repeated corrections during subsequent height adjustments due to uneven air spring pressure.

[0005] Existing closed-loop air suspension systems typically correct height deviations by re-inflating or deflating the main air tank, compressor, and distribution valve assembly after detecting such deviations. While this method is suitable for large height adjustments, it suffers from drawbacks such as long response time, frequent valve operations, increased compressor start-stop cycles, and increased noise and energy consumption when dealing with minor height deviations after adjustment, residual stress release, or slight uneven pressure at the four corners.

[0006] Furthermore, some existing systems estimate the amount of gas to be transferred based on complex software air volume models, considering factors such as air spring pressure, volume, target height, and temperature. However, the effective volume of the air spring varies with height and load, and factors such as air circuit temperature changes, rubber hysteresis, vehicle body structure friction, and road surface disturbances can introduce estimation errors. Relying solely on air volume models can easily lead to over-adjustment, under-adjustment, or the need for multiple iterations for correction.

[0007] While existing technologies include solutions such as dual air tanks, low-pressure tanks, auxiliary air chambers, or additional air chambers for adjusting stiffness, their main purpose is usually to improve the capacity for large-flow inflation and deflation, achieve rapid lifting and lowering, reduce compressor load, or change the stiffness of air springs. They do not establish a dedicated preset pressure balance tank and corresponding control logic for the release of residual internal stress and fine-tuning of attitude after the vehicle has completed height adjustment.

[0008] In summary, the existing technology has the following shortcomings:

[0009] 1. Conventional closed air suspension leveling requires the use of the main air tank or compressor. When correcting minor deviations, the response chain is relatively long, resulting in higher energy consumption and noise. 2. After vehicle height adjustment, lifting and lowering, or on bumpy roads, there may be residual uneven pressure in the air springs and residual internal stress in the suspension mechanism, which cannot be eliminated stably in one go by conventional height control. 3. When relying solely on the gas volume model for leveling, it is easily affected by factors such as effective volume, temperature, rubber hysteresis, and mechanical friction, leading to over-adjustment or repeated corrections. 4. Existing auxiliary gas chamber or dual-tank solutions are mainly geared towards rapid lifting, gas recovery, or stiffness adjustment, but lack balanced pressure windows, short-term connectivity, and feedback closed-loop strategies for fine-tuning. 5. When users perceive that the vehicle is uneven, the existing system often needs to perform the full height adjustment action again, resulting in a poor user experience. Summary of the Invention

[0010] The purpose of this application is to provide a closed air suspension fine-tuning system and method with a balance air tank, so that after the vehicle has completed height adjustment, lifting and lowering, passing through uneven road surfaces or detecting attitude deviation, it can rebalance the air spring circuit with a small flow rate through the balance air tank maintained at a preset pressure window without starting the compressor, exhausting air to the outside atmosphere, or performing a complete main air tank inflation and deflation process, thereby releasing residual internal stress and improving the vehicle body attitude leveling accuracy.

[0011] This application establishes a controllable short-term air circuit and feedback closed-loop control strategy between the balance air tank and the air spring branch, and combines it with a periodic pressure self-maintenance program to reduce dependence on complex air volume models, avoid false triggering under driving dynamic conditions, and thus improve the response speed of small-amplitude leveling and the stability perceived by the user.

[0012] To achieve the above objectives, the present invention provides a closed air suspension fine-tuning system with a balance air tank, comprising: Air springs are used to support the vehicle body; The main air tank serves as the primary high-pressure air source for the closed air suspension system. The balancing gas tank has a smaller volume than the main gas tank and is configured to be maintained within a preset pressure window; The balance control valve is installed in the air path between the balance air tank and the air spring; The detection unit includes a pressure detection unit and a height detection unit; The suspension controller is communicatively connected to the balance control valve and the detection unit. The balance air tank is selectively connected to the air spring branch through the balance control valve, forming a fine-tuning air circuit independent of the main air tank's large-flow adjustment path. The suspension controller is configured to control the balance control valve to perform a short-term connection when it detects that the vehicle has a fine-tuning requirement, so that a small flow of gas is transferred between the air spring and the balance air tank, thereby achieving pressure rebalancing and residual stress release of the air spring without starting the compressor, exhausting gas to the outside atmosphere, or performing the complete main air tank charging and discharging process.

[0013] Preferably, the volume of the balancing gas tank is 0.1 to 0.6 times that of the main gas tank, and more preferably 0.25 to 0.4 times.

[0014] Preferably, the preset pressure window is Pb_low ≤ Pb ≤ Pb_high, where Pb is the pressure of the balance air tank. The pressure window is determined based on the vehicle platform, target height, axle load range, target static pressure of the air spring, temperature compensation coefficient, main air tank pressure, and allowable fine-tuning amount. The pressure of the balance air tank is lower than the pressure of the main air tank and higher than or close to the target static pressure of the air spring.

[0015] Preferably, the balancing control valve is one of the following: a two-way controllable valve, a proportional valve, a combination of a throttle valve and a solenoid valve, or a combination of a check valve and a bypass valve.

[0016] Preferably, it also includes a self-maintaining pressure replenishment path, through which the balance air tank is connected to the main air tank or ASU compressor; the suspension controller is configured to perform pressure replenishment when the pressure of the balance air tank is lower than the lower limit of the preset pressure window, and to perform recovery when it is higher than the upper limit of the preset pressure window, so as to keep the balance air tank in a usable state for a long time.

[0017] Preferably, the balance air tank is a shared balance air tank, which is connected to four air spring branches respectively through a distribution valve group; or, the balance air tank includes a front axle balance air tank and a rear axle balance air tank, which are used for independent pressure balancing of the front and rear axles and pitch attitude correction respectively.

[0018] Preferably, the balance gas tank is integrated into the ASU or valve block housing.

[0019] The technical solution of the present invention also provides a method for fine-tuning a closed air suspension with a balance air tank, comprising the following steps: S100, Signal Acquisition: Acquires target altitude, actual altitude, air spring pressure, balance tank pressure, main tank pressure, temperature, and vehicle status; S200, fine-tuning level condition recognition: determines whether it is in the stable stage after adjustment, after lifting and lowering the vehicle, after bumpy road surface, or when the software requests fine-tuning level condition. S300, Deviation Judgment: Determines whether the vehicle height deviation, left-right height difference, attitude angle or pressure difference exceeds the set threshold. S400, Balanced Gas Tank Availability Determination: Confirm whether the pressure of the balanced gas tank is within the preset pressure window; S500, Short-time connection control: Open the corresponding balance control valve to execute a short-time or pulse connection, so that a small flow of gas is transferred between the air spring and the balance air tank to achieve pressure rebalancing; S600, Closed-loop Exit: The balance control valve is closed based on vehicle height feedback, pressure change, pressure change rate, or valve opening time. S700, Result Recording and Self-Maintenance: Records the leveling results and initiates the self-maintenance process for pressure replenishment or recovery when necessary.

[0020] Preferably, the preset pressure window is a fixed calibration value, or it can be adaptively corrected based on the target height setting, vehicle load, ambient temperature, vehicle mode, and historical leveling results.

[0021] Preferably, in step S700, the self-maintenance process is executed before the vehicle goes into hibernation, after it is woken up, when the vehicle is parked and stationary, after the normal height adjustment is completed, or when a preset time interval is reached; when the pressure of the balance air tank is lower than the lower limit, the pressure is replenished through the main air tank, compressor, or closed recovery air circuit; when it is higher than the upper limit, the gas is transferred to the main air tank, low-pressure side circuit, or air spring branch with lower pressure; if the pressure window cannot be reached within the specified time or the pressure drop rate exceeds the threshold, the leakage fault is recorded and the fine-tuning function is disabled.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects: 1. This application adds a balance air tank that maintains a preset pressure window to the existing closed air suspension system, so that when there is a small height deviation or residual internal stress in the air spring, a small flow pressure rebalancing can be achieved through a short-term connection of the balance control valve, thereby effectively improving the vehicle body leveling stability.

[0023] 2. During the fine-tuning process, there is no need to start the compressor, connect to the outside atmosphere, or perform the large-flow charging and discharging process of the main gas tank, which significantly reduces the noise, energy consumption, and valve group operation frequency during the balancing process.

[0024] 3. By limiting the pressure variation range of the air spring through a preset pressure window, significant over-adjustment can be effectively avoided, improving user satisfaction with the static leveling function.

[0025] 4. The closed-loop exit mechanism based on vehicle height feedback, pressure feedback and attitude feedback can effectively avoid the estimation error caused by relying solely on the air volume model and prevent repeated corrections and iterations.

[0026] 5. Through the periodic pressure self-maintenance program, the balancing gas storage tank can be kept in a usable state for a long time, thereby improving the availability and operational consistency of the system.

[0027] 6. Compared with ordinary dual-tank systems or auxiliary air chamber solutions, the technical objectives and control logic of this application are more clearly defined, focusing on the release of residual internal stress and minor attitude correction after the vehicle has completed height adjustment, thus achieving higher precision static leveling control. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the architecture of a closed air suspension fine-tuning system and method with a balance air tank according to the present invention. Figure 2 This is a schematic diagram of the preset pressure window and pressure convergence of the balance air tank in the closed air suspension fine-tuning system and method with a balance air tank of the present invention. Figure 3 This is a flowchart of the fine-tuning control method in the closed air suspension fine-tuning system and method with a balance air tank of the present invention. Figure 4 This is the fine-tuning triggering and execution strategy matrix in the closed air suspension fine-tuning system and method with a balance air tank of the present invention; Figure 5 This is a table of fine-tuning triggering and execution strategies in a closed air suspension fine-tuning system and method with a balance air tank according to the present invention. Figure 6 This is a table of recommended key parameters for a closed air suspension fine-tuning system and method with a balance air tank, as described in this invention. Figure 7 This table compares the closed air suspension fine-tuning system and method with a balance storage tank of the present invention with existing technical solutions. Figure 8 This is a comparison table of exemplary verification results in the closed air suspension fine-tuning system and method with a balance air tank of the present invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] This invention discloses a closed-loop air suspension fine-tuning system and method with a balance air tank. It adds a small-volume balance air tank to the existing main air tank of the closed-loop air suspension. This balance air tank is selectively connected to the air spring branch, the air spring side air path of the air distribution valve, or the fine-tuning air path in the ASU valve block via a balance control valve, thus forming a fine-tuning air path independent of the main air tank's high-flow-rate adjustment path. This balance air tank is not a typical low-pressure recovery tank, nor is it simply an empty tank used for rapid descent. Instead, it is an intermediate balance air source maintained within a preset pressure window. After the vehicle completes height adjustment, lifting and lowering, traversing uneven roads, or experiencing attitude deviations, it releases or rebalances the residual pressure in the air springs and the internal stress of the system, thereby achieving fine-tuning of the vehicle's height and attitude. Furthermore, it eliminates the need to prioritize starting the compressor, exhaust air to the outside atmosphere, or perform the complete main air tank inflation / deflation process.

[0031] The system of this application includes at least air springs, an air supply unit (ASU), a main air tank, a balance air tank, a distribution valve assembly, a balance control valve, a pressure detection unit, a height detection unit, and a suspension controller, all located at the four corners of the vehicle or at least one axle. The air springs support the vehicle body and adjust the vehicle height through changes in internal air pressure; the relationship between their internal pressure and vehicle height is affected by load, temperature, and mechanical structure. The ASU includes a compressor, a dryer, necessary one-way valves, and solenoid valves, providing air to the main and balance air tanks and participating in gas recovery in the closed loop. Its function is to ensure the cleanliness and circulation supply capacity of the system's air. The main air tank, as the primary high-pressure air source for the closed-loop air suspension, is used for regular lifting and significant vehicle height adjustment; its large volume provides ample gas reserves.

[0032] The balancing air tank, serving as an intermediate balancing air source for fine-tuning, has a volume smaller than the main air tank, preferably 0.1 to 0.6 times the volume of the main air tank, and more preferably 0.25 to 0.4 times. This volume ratio ensures sufficient gas buffering capacity while avoiding excessive increases in system volume and cost. A balancing control valve is located between the balancing air tank and the air spring branch, used to control short-term connection between the balancing air tank and one or more air springs. Its structure can be a combination of a bidirectional controllable valve, a proportional valve, a throttle valve and a solenoid valve, or a one-way valve and a bypass valve, to achieve different flow characteristics and control accuracy requirements. The pressure detection unit detects the main air tank pressure Pmain, the balancing air tank pressure Pb, the air spring pressure Ps, or the valve group branch pressure, providing real-time pressure feedback for control decisions. The height detection unit detects the vehicle's four corner heights, axial height, or vehicle posture. It can be a height sensor, a displacement sensor, or a height signal estimated by other sensors; its detection accuracy directly affects the fine-tuning effect. As the core control unit of the system, the suspension controller controls the balance control valve, main air tank valve, compressor, and distribution valve group based on target height, actual height, pressure, temperature, vehicle speed, door status, load status, and user requests. It internally stores preset control logic and parameter calibration values. In terms of air circuit connections, the main air tank is connected to the distribution valve group and air spring branch via the main air tank air circuit Vm, while the balance air tank is connected to the distribution valve group / air spring branch via an independent balance air circuit Vb. A PMIAN passage is provided between the balance air tank and the main air tank for self-maintenance pressure replenishment. The ASU compressor can also be directly connected to the balance air tank via this self-maintenance pressure replenishment passage. The suspension controller receives height / pressure / attitude feedback signals from the pressure detection unit and height detection unit and outputs control commands to each actuator, thus forming a complete closed-loop control link from signal acquisition to action execution.

[0033] The balance air tank is maintained within a preset pressure window, denoted as Pb_low≤Pb≤Pb_high. This pressure window can be determined based on the vehicle platform, target height, axle load range, target static pressure of the air springs, temperature compensation coefficient, main air tank pressure, and allowable fine-tuning amount. Preferably, the balance air tank pressure is lower than the main air tank pressure and higher than or close to the target static pressure of the air springs, so that when connected to air springs with excessively high pressure, it can receive some gas and reduce the air spring pressure, while preventing the air spring pressure from dropping too low rapidly. For air replenishment, the balance air tank pressure can be set slightly higher than the target static pressure, allowing it to provide a limited amount of air to air springs with locally low pressure. When an air spring pressure is too high, the vehicle height is too high, or local residual stress needs to be released, the controller briefly opens the corresponding balance control valve, causing a small flow of gas transfer between the air spring and the balance air tank. The air spring pressure converges to the balance air tank pressure, thereby achieving minor height correction and residual stress release. This pressure convergence process is a physical self-balancing process, which does not rely on complex gas volume calculation models. Therefore, it can effectively avoid estimation errors caused by temperature changes, rubber hysteresis, and mechanical friction. The pressure window of the balancing gas tank can be a fixed calibration value, or it can be adaptively corrected according to the target height setting, vehicle load, ambient temperature, vehicle mode, and historical leveling results to adapt to different operating conditions and vehicle aging.

[0034] The fine-tuning control method of this application includes the following steps: S100, Signal Acquisition: The system acquires target height Htar, actual height Hact, height difference at four corners, air spring pressure Ps, balance air tank pressure Pb, main air tank pressure Pmain, ambient temperature, air circuit temperature, vehicle speed, door status, lifting status, road surface excitation status, and user requests. These signals together constitute the basic data for control decision-making.

[0035] S200, Fine-tuning Condition Recognition: The system determines whether the vehicle is in the stable stage after completing height adjustment, the re-landing stage after lifting and lowering, the stable stage after passing through bumpy roads, the stationary parking leveling stage, or the fine-tuning stage actively requested by the software. The purpose of this step is to avoid accidentally triggering fine-tuning during dynamic driving conditions or large height adjustments.

[0036] S300 Deviation Judgment: When the difference between the actual height and the target height, the difference between the left and right heights, the front and rear pitch angles, the lateral roll angles, the air spring pressure difference, or the height change rate exceeds the set threshold, the system determines that there is a need for fine-tuning. This threshold is usually set to 5 to 15 millimeters or calibrated according to the vehicle model, corresponding to static unevenness problems that can be perceived by the user.

[0037] S400, Balanced Air Tank Availability Determination: The system determines whether Pb is within the preset pressure window and confirms that there are no faults affecting fine-tuning in the main air tank, compressor, related valve group, pressure sensor and height sensor. If the balanced air tank is unavailable, it switches to the self-maintenance or regular height adjustment process.

[0038] S500, short-time connection control: The system selects the corresponding air spring branch according to the direction of deviation, opens the balance control valve, and connects the air spring to the balance air tank for a short time. The valve opening mode can be single short-time valve opening, pulse valve opening, multi-stage throttling valve opening, or continuous control of proportional valve. The single valve opening time can be adjusted from 20ms to 5s according to the valve diameter and air circuit volume. The maximum number of valve openings can be set from 1 to 10 times to avoid repeated action and over-adjustment.

[0039] S600, Closed-loop Exit: The system closes the balance control valve based on vehicle height feedback, pressure change, pressure change rate, valve opening time, number of valve openings, or attitude angle convergence. This closed-loop mechanism can effectively prevent repeated corrections caused by simple gas volume model errors.

[0040] S700, Result Recording and Self-Maintenance: The system records the height, pressure, valve opening time and execution results before and after leveling. When Pb is lower or higher than the target window, it enters the self-maintenance process of balancing the gas storage tank pressure.

[0041] The step numbers are used to indicate the logical order, but are not intended to require that they be executed in exactly the same order. Some steps can be combined, split, or adjusted without affecting the technical effect.

[0042] The fine-tuning function triggers and executes differentiated control strategies in various scenarios: After the vehicle completes the raising or lowering action, when the difference between the actual height and the target height continues to exceed the set threshold and the vehicle speed is low, such as 5 to 15 mm, the system triggers fine-tuning. The control action is to connect the high-angle or axle-side air circuit, so that the high-angle side air spring releases some gas to the balance air tank. The exit condition is that the height enters the target zone.

[0043] In vehicle lifting and lowering scenarios, when the height difference at the four corners or the air spring pressure difference exceeds the set threshold, the system triggers fine-tuning. The control action is to execute a short-time pulse depressurization to release residual stress. The exit condition is a decrease in the pressure change rate.

[0044] If the vehicle's attitude angle or height deviation does not recover within a stable time after passing over a bumpy road, speed bump, or unilateral compression and rebound, the system will trigger fine-tuning. The control action is to perform fine-tuning of the balance tank without turning on the compressor. The exit condition is that the attitude error converges.

[0045] The user initiates a leveling request, or the vehicle controller requests the air suspension to perform static attitude correction.

[0046] The system detected that the pressure of a certain air spring was significantly higher than its target pressure, and it was expected that the correction could be completed by briefly connecting the balance air tank.

[0047] Preferably, the fine-tuning process does not start the compressor, does not connect to the outside atmosphere, and does not perform the large-flow charging and discharging action of the main air tank. It is completed only by rebalancing the small-flow gas between the balancing air tank and the target air spring branch. If the fine-tuning exceeds the maximum number of valve openings or still fails to converge, the fine-tuning is exited and the process switches to regular height adjustment or fault diagnosis.

[0048] To ensure the balance tank remains usable during fine-tuning, this application incorporates a pressure self-maintenance program. This program can execute before vehicle hibernation, after waking, when parked, after routine height adjustment, or at preset time intervals. The timing of execution balances system availability and energy efficiency. When Pb is below Pb_low, the controller can repressurize the balance tank via the main tank, compressor, or closed-loop recovery system. During repressurization, pressure compensation based on temperature corrects for its impact on gas pressure. When Pb is above Pb_high, the controller can transfer some gas from the balance tank to the main tank, low-pressure side circuit, or lower-pressure air spring branch. It can also reduce Pb through a closed-loop recovery system, enabling gas recycling within the system. The self-maintenance process also monitors the balance tank pressure drop rate. If the pressure window cannot be reached within a specified time, or if the pressure drop rate exceeds a threshold, a potential gas leak is detected. In this case, the system records the fault and disables fine-tuning to ensure system safety and reliability.

[0049] Among the alternative approaches, this application provides several implementation schemes to adapt to different vehicle architecture requirements: 1. A common balance air tank is set up and connected to four air spring branches through a distribution valve group for uniform fine-tuning of the four corners of the vehicle; 2. Balance air tanks are installed on the front and rear axles respectively for independent pressure balancing and pitch attitude correction between the front and rear axles. This scheme can improve the decoupling control capability between the axles. 3. The balance gas tank is integrated into the ASU or valve block housing, reducing the length of external pipelines and improving response speed, while reducing the risk of system leakage; 4. The balance control valve adopts a combination of proportional valve or throttle valve to make the flow rate adjustable, reduce pressure changes and vehicle body vibration, and improve the smoothness of adjustment. 5. Under low temperature, high temperature or heavy load conditions, adjust Pb_target, valve opening time and leveling threshold according to temperature and load to compensate for the effects of extreme conditions on gas state and suspension mechanical characteristics.

[0050] The exemplary verification results show that, compared with the conventional closed air suspension leveling scheme, this application, by setting a balance air tank with a preset pressure window and performing short-term connection control after adjustment, after lifting and lowering the vehicle, or after the vehicle's posture deviation exceeds the limit, can achieve small-flow rebalancing of the air spring pressure without starting the compressor, without connecting to the outside atmosphere, and without performing large-flow inflation and deflation of the main air tank.

[0051] Verification results show that, after adopting the proposed solution, the maximum height error at the four corners after adjustment decreased from 12.4 mm to 3.2 mm, a reduction of approximately 74.2%; the left-right height difference decreased from 9.8 mm to 2.6 mm, a reduction of approximately 73.5%; the maximum height deviation at a single corner after lifting and lowering the vehicle decreased from 13.6 mm to 3.5 mm; the left-right air spring pressure difference after lifting and lowering the vehicle decreased from 0.38 bar to 0.09 bar, a reduction of approximately 76.3%; and the single fine-tuning response time was shortened from 8.5 seconds. The time to adjust the balance tank was reduced to 2.1 seconds, a reduction of approximately 75.3%; the number of compressor starts during the fine-tuning process was reduced from 1 to 0; the number of single fine-tuning valve group actions was reduced from 6 to 2, a reduction of approximately 66.7%; the peak perceived noise level inside the vehicle was reduced from 42.0 dB(A) to 33.5 dB(A), a reduction of approximately 8.5 dB(A); after 10 consecutive fine-tuning operations, the pressure of the balance tank remained within the range of 6.6 bar to 8.3 bar, indicating that the pressure self-maintenance strategy can ensure that the balance tank remains in a usable state for a long time.

[0052] Compared with existing conventional closed single-main-tank systems, dual-tank closed systems, auxiliary air chamber stiffness adjustment schemes, and air volume model-based leveling schemes, the core difference of this application lies in the fact that the balance air tank serves as an intermediate balance air source within a preset pressure window, rather than a regular low-pressure recovery tank or a rapidly descending empty tank. A short-term connection between the balance air tank and the air spring branch's balance control valve is specifically used for residual internal stress release and fine-tuning. Fine-tuning is triggered based on height deviation, pressure difference, attitude angle, post-adjustment state, lifting and lowering state, or software requests. Closed-loop exit is achieved based on vehicle height feedback, pressure change, pressure change rate, valve opening time, or number of valve openings. Simultaneously, periodic self-maintenance ensures the balance air tank remains in a usable state for an extended period, thereby effectively improving vehicle static leveling accuracy, reducing noise during the leveling process, and enhancing the user's perception of the air suspension leveling function.

[0053] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A closed-loop air suspension fine-tuning system with a balance air tank, characterized in that, include: Air springs are used to support the vehicle body; The main air tank serves as the primary high-pressure air source for the closed air suspension system. The balancing gas tank has a smaller volume than the main gas tank and is configured to be maintained within a preset pressure window; The balance control valve is installed in the air path between the balance air tank and the air spring; The detection unit includes a pressure detection unit and a height detection unit; The suspension controller is communicatively connected to the balance control valve and the detection unit. The balance air tank is selectively connected to the air spring branch through the balance control valve, forming a fine-tuning air circuit independent of the main air tank's large-flow adjustment path. The suspension controller is configured to control the balance control valve to perform a short-term connection when it detects that the vehicle has a fine-tuning requirement, so that a small flow of gas is transferred between the air spring and the balance air tank, thereby achieving pressure rebalancing and residual stress release of the air spring without starting the compressor, exhausting gas to the outside atmosphere, or performing the complete main air tank charging and discharging process.

2. The closed-loop air suspension fine-tuning system with a balance air tank according to claim 1, characterized in that, The volume of the balancing gas storage tank is 0.1 to 0.6 times that of the main gas storage tank, preferably 0.25 to 0.4 times.

3. The closed-loop air suspension fine-tuning system with a balance air tank according to claim 1, characterized in that, The preset pressure window is Pb_low ≤ Pb ≤ Pb_high, where Pb is the pressure of the balance air tank. The pressure window is determined based on the vehicle platform, target height, axle load range, target static pressure of the air spring, temperature compensation coefficient, main air tank pressure, and allowable fine-tuning amount. The pressure of the balance air tank is lower than the pressure of the main air tank and higher than or close to the target static pressure of the air spring.

4. A closed-loop air suspension fine-tuning system with a balance air tank according to claim 1, characterized in that, The balance control valve is one of the following: a two-way controllable valve, a proportional valve, a combination of a throttle valve and a solenoid valve, or a combination of a check valve and a bypass valve.

5. A closed-loop air suspension fine-tuning system with a balance air tank according to claim 1, characterized in that, It also includes a self-maintaining pressure replenishment path, through which the balance air tank is connected to the main air tank or ASU compressor; the suspension controller is configured to perform pressure replenishment when the pressure of the balance air tank is lower than the lower limit of the preset pressure window, and to perform recovery when it is higher than the upper limit of the preset pressure window, so as to keep the balance air tank in a usable state for a long time.

6. A closed-loop air suspension fine-tuning system with a balance air tank according to claim 1, characterized in that, The balance air tank is a shared balance air tank, which is connected to four air spring branches through a distribution valve group; or, the balance air tank includes a front axle balance air tank and a rear axle balance air tank, which are used for independent pressure balancing and pitch attitude correction of the front and rear axles, respectively.

7. A closed-loop air suspension fine-tuning system with a balance air tank according to claim 1, characterized in that, The balance gas tank is integrated into the ASU or valve block housing.

8. A method for using a closed air suspension fine-tuning system with a balance air tank as described in any one of claims 1-7, characterized in that, Includes the following steps: S100, Signal Acquisition: Acquires target altitude, actual altitude, air spring pressure, balance tank pressure, main tank pressure, temperature, and vehicle status; S200, fine-tuning level condition recognition: determines whether it is in the stable stage after adjustment, after lifting and lowering the vehicle, after bumpy road surface, or when the software requests fine-tuning level condition. S300, Deviation Judgment: Determines whether the vehicle height deviation, left-right height difference, attitude angle or pressure difference exceeds the set threshold. S400, Balanced Gas Tank Availability Determination: Confirm whether the pressure of the balanced gas tank is within the preset pressure window; S500, Short-time connection control: Open the corresponding balance control valve to execute a short-time or pulse connection, so as to generate a small flow of gas transfer between the air spring and the balance air tank to achieve pressure rebalancing; S600, Closed-loop Exit: The balance control valve is closed based on vehicle height feedback, pressure change, pressure change rate, or valve opening time. S700, Result Recording and Self-Maintenance: Records the leveling results and initiates the self-maintenance process for pressure replenishment or recovery when necessary.

9. A method for fine-tuning a closed air suspension with a balance air tank according to claim 8, characterized in that, The preset pressure window is a fixed calibration value, or it can be adaptively corrected based on the target height setting, vehicle load, ambient temperature, vehicle mode, and historical leveling results.

10. A method for fine-tuning a closed air suspension with a balance air tank according to claim 8, characterized in that, In step S700, the self-maintenance process is executed before the vehicle goes into hibernation, after it is woken up, when the vehicle is parked and stationary, after the normal height adjustment is completed, or when a preset time interval is reached. When the pressure of the balance air tank is lower than the lower limit, the pressure is replenished through the main air tank, the compressor, or the closed recovery air circuit. When the pressure is higher than the upper limit, the gas is transferred to the main air tank, the low-pressure side circuit, or the air spring branch with lower pressure. If the pressure window cannot be reached within the specified time or the pressure drop rate exceeds the threshold, the leakage fault is recorded and the fine-tuning function is disabled.

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