Stroke-controllable hydro-pneumatic suspension cylinder and control method thereof

Abstract

The invention discloses a stroke-controllable hydro-pneumatic suspension cylinder and a control method thereof.The stroke-controllable hydro-pneumatic suspension cylinder comprises a cylinder barrel, a piston rod, a piston, an internal control valve set, a sealing seat ring, an energy accumulator, a control valve, a gas-liquid booster pump and a flow control cylinder, the piston is arranged in the cylinder barrel, the piston rod is connected to the piston, and the piston rod is connected with the upper portion of the cylinder barrel through the sealing seat ring in a sealed mode; an inner cavity of the cylinder barrel is communicated with an inner cavity of the piston rod through a damping channel on the internal control valve group to form an independent suspension cylinder inner cavity system; a suspension cylinder inner cavity is defined by the cylinder barrel, the piston rod and the piston in the suspension cylinder, an auxiliary oil cavity is defined by the cylinder barrel, the sealing seat ring, the piston rod and the piston on the side wall of the waist portion of the suspension cylinder, and the auxiliary oil cavity is externally connected with a control valve and an energy storage device through pipelines to form an independent external control loop. A double-channel isobaric and synchronous control system structure is formed by the gas-liquid booster pump, the flow control cylinder and a constructed double-loop system, reliable and stable stroke control can be achieved, and meanwhile rigidity and height control is attached.

Description

Technical Field

[0001] The present invention relates to the technical field of oil-gas suspension cylinders, and in particular to a controllable-stroke oil-gas suspension cylinder and a control method thereof. Background Art

[0002] The oil-gas suspension cylinder integrates the structural principles and usage functions of air springs and hydraulic dampers, and has better mechanical properties and application range. The oil-gas suspension cylinder is filled with nitrogen and hydraulic oil. Nitrogen, as an elastic medium and energy storage medium, has variable stiffness characteristics and a larger energy storage ratio than metal elastic materials. Hydraulic oil, as a damping medium, generates damping force through the damping structure inside the suspension cylinder.

[0003] Since nitrogen is encapsulated in the cylinder structure, the oil-gas suspension cylinder has a greater working pressure and capacity than the air spring. Similar to the structure of a conventional hydraulic cylinder, the oil-gas suspension cylinder is also composed of a cylinder assembly and a piston rod assembly according to the motion relationship and installation structure. The internal volume compartment includes a rod chamber and a rodless chamber, and the piston rod is usually a hollow structure. Among them, the rodless chamber is called the suspension cylinder cavity, which is composed of the cylinder cavity and the piston rod cavity. The rod cavity is called the auxiliary oil cavity, which is an annular space surrounded by the cylinder assembly and the piston rod assembly between the side walls of the waist of the suspension cylinder.

[0004] When the inner cavity of the suspension cylinder is used as a cavity, it is filled with hydraulic oil and nitrogen, also known as an oil-gas mixing cavity or a mixed oil cavity. During use, the volume space of the auxiliary oil cavity changes the most, and is usually used as the source of the damping flow inside the suspension cylinder. The auxiliary oil cavity is filled with hydraulic oil, and a damping channel is provided on the side wall of the piston rod inside the cavity to connect with the inner cavity of the suspension cylinder.

[0005] like Figure 1 , Figure 2 The following are two typical structural types of single-chamber and double-oil-cavity oil-gas suspension cylinders. Figure 1 It is a piston rod upper structure. Figure 2 It is a structure with a downward piston rod. The oil chamber that is only filled with hydraulic oil is called a pure oil chamber, which includes a variable pure oil chamber and an immutable pure oil chamber. The variable pure oil chamber is connected to the mixed oil chamber to form a damping channel. When the suspension cylinder is compressed or stretched, the volume and pressure of the variable pure oil chamber and the mixed oil chamber change to generate a damping flow. In the single-chamber dual-oil chamber structure, the auxiliary oil chamber is connected to the suspension inner cavity as a variable pure oil chamber. The area where the system pressure inside the suspension cylinder provides elastic force to the outside is called the pressure action area. The area that generates damping flow with the compression or extension speed of the suspension cylinder is called the damping flow area. The elastic force of the suspension cylinder is determined by the system pressure inside the suspension cylinder and the pressure action area. The damping flow of the system is determined by the damping flow area and the compression or extension speed of the suspension cylinder. In the single-chamber dual-oil chamber structure, the pressure action area is the outer circle area of ​​the piston rod of the suspension cylinder. For the stiffness curve, refer to Fig.13The damping flow area is the cross-sectional area of ​​the variable pure oil chamber, that is, the annular area of ​​the auxiliary oil chamber. For damping characteristics, see Fig.15 .

[0006] like Figure 3-Figure 6 The following are four typical single air chamber and three oil chamber structures. The pressure action area is the piston rod area. The stiffness curve is shown in Fig.13 The three-chamber structure is to divide the suspension cylinder cavity into the cylinder barrel cavity and the piston rod cavity through the piston or valve plate structure. The main oil chamber is filled with hydraulic oil alone, and the mixed oil chamber is filled with hydraulic oil and nitrogen at the same time. The piston or valve plate is arranged with a damping structure, which connects the cylinder barrel cavity and the piston rod cavity to form an inner cavity damping channel. The auxiliary oil chamber is connected to the suspension cylinder cavity through the piston rod side wall damping structure to form an auxiliary oil chamber damping channel. The damping characteristics refer to Fig.15 .

[0007] Figure 3 The figure shows a piston rod upper structure. The cylinder inner cavity (main oil chamber) and the auxiliary oil chamber are both variable pure oil chambers, which are respectively connected with the piston rod inner cavity (mixed oil chamber) to form two parallel damping channels. The damping structure on the piston rod side wall and the damping structure on the piston or valve plate are also usually a combination of a one-way valve and a damping hole. The damping flow area of ​​the main oil chamber channel is the cylinder inner cavity area, and the damping flow area of ​​the auxiliary oil chamber channel is the auxiliary oil chamber annular area.

[0008] Figure 4 The figure shows a piston rod down-mounted structure, in which the auxiliary oil chamber is a variable pure oil chamber, the piston rod inner chamber (main oil chamber) is an immutable pure oil chamber, and the auxiliary oil chamber is connected with the cylinder inner chamber (mixed oil chamber) through the piston rod inner chamber to form a damping channel, and the damping flow area is the annular area of ​​the auxiliary oil chamber.

[0009] Figure 5 The figure shows another piston rod down-mounted structure, in which the inner cavity of the piston rod is separated from the oil / gas part by a floating piston to form a mixed oil chamber. The inner cavity of the cylinder barrel (main oil chamber) and the auxiliary oil chamber are both variable pure oil chambers, which are respectively connected to the inner cavity of the piston rod to form two parallel damping channels. The damping flow area of ​​the main oil chamber channel is the inner cavity area of ​​the cylinder barrel, and the damping flow area of ​​the auxiliary oil chamber channel is the annular area of ​​the auxiliary oil chamber.

[0010] Figure 6 The figure shows the pressure compensation structure on the piston rod. The inner cavity of the cylinder (main oil cavity) and the auxiliary oil cavity are both variable pure oil cavities, and the inner cavity of the piston rod is a mixed oil cavity. The auxiliary oil cavity → main oil cavity → mixed oil cavity are connected in sequence to form two damping channels in series, forming a complementary relationship between the pressure and flow between the auxiliary oil cavity and the main oil cavity, eliminating the system negative pressure phenomenon of the oil-gas suspension cylinder and significantly improving the application range of the system damping coefficient. The damping flow area of ​​the main oil cavity channel is the outer circle area of ​​the piston rod, and the damping flow area of ​​the auxiliary oil cavity channel is the annular area of ​​the auxiliary oil cavity.

[0011] like Figure 7 , Figure 8 , Fig. 9 The following are three typical double-chamber and three-oil-cavity oil-gas suspension cylinder structures, all of which have downwardly placed piston rods.

[0012] Figure 7 It is a double-chamber forward series structure. The inner cavity of the cylinder barrel and the inner cavity of the piston rod each contain a mixed oil chamber, which are connected through a damping structure. The auxiliary oil chamber is a variable pure oil chamber that is connected to the inner cavity of the piston rod to provide the main damping flow of the system. The damping flow area is the area of ​​the auxiliary oil chamber. Additional damping flow can be generated between the two mixed oil chambers. The size and flow direction depend on the initial inflation parameters of the upper and lower air chambers. The auxiliary oil chamber and the two mixed oil chambers in the inner cavity of the cylinder barrel and the inner cavity of the piston rod constitute a full-through hydraulic circuit, which includes two damping channels. The overall pressure action area of ​​the suspension cylinder is the area of ​​the piston rod. For the stiffness curve, see Fig.13 , damping characteristics see Fig.15 .

[0013] Figure 8 It is a double air chamber oppositely opposed structure. The inner cavity of the suspension cylinder is isolated by a closed piston structure into a cylinder inner cavity and a piston rod inner cavity which are independent of each other. The inner cavity of the cylinder and the inner cavity of the piston rod each contain a mixed oil chamber. The pressure of the inner cavity of the piston rod is introduced into the auxiliary oil chamber through a set of pipelines to form a counter-pressure opposed structure with the inner cavity of the cylinder. Its elastic force output is the difference between the pressure output of the inner cavity area of ​​the cylinder and the pressure output of the auxiliary oil chamber area. For the stiffness curve, see Fig.14 The auxiliary oil chamber is used as a variable pure oil chamber. It forms a damping channel through the connecting pipeline with the inner cavity of the piston rod to form the damping flow of the system. The damping flow area of ​​the system is the area of ​​the auxiliary oil chamber. For damping characteristics, see Fig.15 .

[0014] Fig. 9 It is another double air chamber oppositely opposed structure, and its stiffness characteristics are similar to Figure 8 Similar structure, see Fig.14 .and Figure 8 The difference in structure is that the inner cavity of the cylinder is a variable pure oil chamber, and an accumulator is added outside as a mixed oil chamber. The middle is connected by a pipeline and a damping valve to form a main oil chamber damping channel. The damping flow area of ​​the main oil chamber channel is the inner cavity area of ​​the cylinder, and the damping flow area of ​​the auxiliary oil chamber channel is the annular area of ​​the auxiliary oil chamber.

[0015] It should be noted that:

[0016] 1. In addition to the basic single air chamber and double oil chamber structure ( Figure 1 , Figure 2 ), the piston rod upper structure and the piston rod lower structure no longer have the same mechanical model and mechanical relationship (such as Figure 3 and Figure 4), and it involves the different packaging structures, positions and damping channel structures of hydraulic oil and nitrogen. A type of oil-gas suspension cylinder may not be usable after being inverted, which is also a feature of the oil-gas suspension cylinder.

[0017] 2. The damping flow of the suspension cylinder comes from the volume change of the variable pure oil chamber when the suspension cylinder is compressed or stretched. The generation of the damping flow must connect the variable pure oil chamber to the mixed oil chamber, or finally connect to the mixed oil chamber through another pure oil chamber to form a damping channel, otherwise the mechanical relationship inside the suspension cylinder will not hold.

[0018] From the existing ( Figure 1-Figure 9 ) From the perspective of various application structures, the auxiliary oil chamber is the main source of the system damping flow, and without exception, they are all connected to the inner cavity of the suspension cylinder to form a hydraulic circuit closed to the outside.

[0019] 3. Figure 8 , Fig. 9 As shown in the figure, both are counter-pressure opposing structures with the piston rod placed downward. Although relatively good stiffness characteristics are obtained ( Fig.14 ), but these two structures must be based on the physical isolation of the cylinder cavity and the piston rod cavity, which loses the important structural, position, speed, flow and pressure relationships between the cylinder cavity and the piston rod cavity, and the complex duct structure of the piston rod cavity occupies the internal effective space, making it impossible to arrange and apply the variable damping structure based on the position, flow and pressure control relationship in the suspension cylinder cavity; in addition, the complex duct structure of the piston rod cavity is difficult to install and maintain, and has poor reliability.

[0020] 4. Figure 1-Figure 9 The nine structures listed are the main structural forms of the existing oil-gas suspension cylinder in terms of stiffness structure. Under the conventional structure, the damping structure of the system consists of a damping hole and a one-way valve, which cannot be adjusted during use. The damping characteristic of the system is a quadratic curve F=f(v) based on the velocity term and the difference between the forward and reverse directions. See Fig.15 .

[0021] Figure 1-Figure 7 The structure and stiffness characteristics are basically the same. For the characteristic curve, see Fig.13 , which is a positive nonlinear curve with a hard point at the starting position of the curve. The entire suspension cylinder internal system is a closed loop, and external input cannot be introduced for control. However, variable damping mechanism can be arranged based on the internal space and structure to achieve variable damping control to a certain extent.

[0022] Figure 8 , Fig. 9 The structure has obtained relatively good stiffness characteristics and eliminated hard points (see stiffness characteristic curve for details). Fig.14), but the lack of external control targets and control links makes it difficult to achieve external control of the system stiffness and state. Moreover, due to the physical isolation of the suspension cylinder cavity in its structure, the subsequent variable damping control cannot be achieved.

[0023] Active and semi-active control suspension systems focus on active or semi-active comprehensive control of system travel, state, stiffness, and damping. The existing various types of oil and gas suspension cylinder structures lack the structural foundation and conditions for complete realization.

[0024] 5. The existing oil-gas suspension cylinders of various structures all focus on the matching of the internal stiffness and damping characteristics of the suspension cylinder itself, as well as the integrity and reliability of independent operation. They do not consider setting external input ports and internal control links for external active control. The internal oil chambers and air chambers are interrelated and mutually controlled, and they were usually used independently as separate components before. However, as the entire chassis, especially active and semi-active suspensions, active or semi-active control is required for different road conditions, operating states, and different driving and operating environments; and the entire oil-gas suspension cylinder does not have an independent link for external control or multi-suspension cylinder combination control, so that the excellent performance and combination potential of the oil-gas suspension cylinder cannot be fully utilized. Applying external active control on the existing type of suspension cylinder structure will cause the internal flow and pressure of the suspension cylinder to be disordered, leading to problems with system stability and reliability.

[0025] Active and semi-active suspensions are widely used in high-end products such as sedans and commercial vehicles. They are mainly based on the combination of leaf springs, coil springs, air springs, etc. with electronically controlled dampers, and are controlled by electronic control systems. However, they are limited by the working capacity, control capacity, system accuracy, and cost structure of suspension components and electronic control systems, and are greatly restricted in their application in large vehicles and popular products. The application of oil-gas suspensions in engineering, heavy-duty, and popular vehicles is still blank. Among them, the travel control, height control, and state control of the suspension system are the most basic functional requirements. It is urgent to propose a basic oil-gas suspension cylinder structure that can be used in active and semi-active control systems, as well as a basic system structure solution for travel and state control. Summary of the invention

[0026] The purpose of the present invention is to provide a controllable stroke oil-gas suspension cylinder and a control method thereof, to construct a basic structure for external active control and combined control between multiple suspension cylinders, and a structural scheme for implementing stroke, height and state control. The core lies in constructing two independent internal / external hydraulic circuit systems, the target link of external active control, the control form and the structural scheme for implementing control, so as to solve the above problems existing in the prior art.

[0027] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0028] A controllable stroke oil-gas suspension cylinder of the present invention comprises a cylinder barrel, a piston rod, a piston, an internal control valve group, a sealing seat ring, an accumulator, a control valve, a gas-liquid booster pump and a flow control cylinder, wherein the cylinder barrel is provided with the piston, the piston rod is connected to the piston, and the piston rod is sealed and connected to the upper part of the cylinder barrel through the sealing seat ring;

[0029] The cylinder barrel, the piston rod and the piston form a suspension cylinder inner cavity inside the suspension cylinder, the suspension cylinder inner cavity is a rodless cavity, the bottom of the piston rod is provided with the internal control valve group, and the internal control valve group divides the suspension cylinder inner cavity into a cylinder barrel inner cavity and a piston rod inner cavity, the cylinder barrel inner cavity is filled with hydraulic oil and an external control interface is provided at the bottom, and the piston rod inner cavity is filled with hydraulic oil and nitrogen, wherein the cylinder barrel inner cavity and the piston rod inner cavity are connected through the damping channel on the internal control valve group to form an independent suspension cylinder inner cavity system;

[0030] The cylinder barrel, the sealing seat ring, the piston rod and the piston form a secondary oil chamber between the side walls of the waist of the suspension cylinder. The secondary oil chamber is a rod chamber, the secondary oil chamber is filled with hydraulic oil and is completely isolated from the inner cavity of the suspension cylinder. The secondary oil chamber is provided with a connection port at a position of the cylinder barrel near the sealing seat ring. The secondary oil chamber is externally connected to the control valve and the accumulator through a pipeline to form an independent external control circuit.

[0031] The gas-liquid booster pump includes a reversing valve that can implement oil circuit reversing and closing control, and is internally connected to the rodless chamber of the flow control cylinder. The gas-liquid booster pump is provided with an external control interface, and the external control interface of the gas-liquid booster pump is connected to the external control interface of the suspension cylinder inner chamber system; the flow control cylinder is provided with an external control interface, and the external control interface of the flow control cylinder is arranged in the rod chamber and connected to the external control interface of the external control circuit; thereby forming two independent closed systems, forming two independent channels for synchronous control of the suspension cylinder stroke, stiffness and height.

[0032] Furthermore, the control valve is an input port for externally controlling the stroke, stiffness and height of the suspension cylinder, and serves as a damping / flow control element within an external control loop, and is provided with an external control interface.

[0033] Furthermore, the auxiliary oil chamber in the external control circuit and the cylinder inner chamber in the suspension cylinder inner chamber system form a double air chamber counter-pressure opposing structure.

[0034] Furthermore, the accumulator is filled with hydraulic oil and nitrogen.

[0035] Furthermore, the inner cavity of the suspension cylinder maintains a complete inner cavity structure and pressure / flow relationship, and the internal control valve group serves as a damping control component between the inner cavity of the cylinder barrel and the inner cavity of the piston rod.

[0036] The present invention also provides a control method for a controllable-stroke oil-gas suspension cylinder, comprising:

[0037] 1) When the suspension cylinder stroke needs to be reduced, the reversing valve is placed in the retracted position, the gas-liquid booster pump is started, and a certain amount of hydraulic oil in the suspension cylinder inner cavity system is injected into the rodless cavity of the flow control cylinder, and at the same time, a certain amount of hydraulic oil in the rod cavity of the flow control cylinder is injected into the auxiliary oil cavity of the suspension cylinder through the external control circuit; the suspension cylinder stroke is reduced, and the balance position changes until a new balance position is reached; wherein, the piston rod / cylinder area ratio selected by the flow control cylinder is associated with the piston rod / cylinder area ratio of the suspension cylinder, and an isobaric control state or a non-isobaric control state can be achieved;

[0038] 2) When the stroke of the suspension cylinder needs to be increased, the reversing valve is placed in the release position, the gas-liquid booster pump is started, and the hydraulic oil in the rodless chamber of the flow control cylinder is reversely injected into the suspension cylinder inner chamber system. At the same time, relying on the pressure difference between the two circuits / systems, the quantitative hydraulic oil in the auxiliary oil chamber of the suspension cylinder is discharged back to the rod chamber of the flow control cylinder through the external control circuit;

[0039] 3) When there is no need to control or change the stroke of the suspension cylinder, turn off and start the gas-liquid booster pump and place the reversing valve in the cut-off position.

[0040] When the suspension cylinder is compressed or stretched, the volumes of the cylinder cavity and the auxiliary oil cavity change, and both are variable oil cavities. For the suspension cylinder cavity system, flow is exchanged between the cylinder cavity and the piston rod cavity, and the damping flow area is the cylinder cavity area. For the external control circuit, flow is exchanged between the auxiliary oil chamber and the accumulator, and the damping flow area is the auxiliary oil chamber area. The suspension cylinder cavity system and the external control circuit form a double-chamber counter-pressure opposing structure through the cylinder cavity (main oil chamber) and the auxiliary oil chamber. The pressure action area of ​​the suspension cylinder cavity system is the cylinder cavity area. The pressure action area of ​​the external control circuit is the auxiliary oil chamber area. The overall elastic force output of the suspension cylinder is the superposition of the pressure of the cylinder cavity area and the auxiliary oil chamber area. See Fig. 20 Curve 1 is the stiffness curve of the suspension cylinder inner cavity system, curve 2 is the stiffness curve of the external control loop, and curve 3 is the comprehensive stiffness curve of the suspension cylinder system. Fig. 20 It can be seen that the external control loop makes a good correction to the stiffness characteristics of the suspension cylinder inner cavity system in the initial stage and forms a positive and negative zero-crossing equilibrium position.

[0041] The internal structure of the gas-liquid booster pump is a cylinder / plunger cylinder combination structure. Relying on the reciprocating motion of the piston / plunger combined with the one-way valve, the hydraulic oil in the suspension cylinder cavity is injected into the rodless cavity of the flow control cylinder at a high pressure and pulsating flow rate, pushing the hydraulic oil in the rod cavity on the other side into the auxiliary oil cavity of the suspension cylinder to achieve the control of the suspension cylinder stroke and height. The piston in the flow control cylinder still plays the role of isolating the suspension cylinder cavity system from the external control circuit. The area ratio of the rod cavity / rodless cavity of the flow control cylinder maintains a certain proportional relationship with the area ratio of the auxiliary oil cavity / cylinder cavity of the suspension cylinder to achieve a specific control effect. When releasing, open the release switch between the gas-liquid booster pump and the flow control cylinder, and the flow control cylinder returns to its position in a differential manner. In addition to adjusting the control characteristics, the piston rod of the flow control cylinder also serves as a signal acquisition component and control trigger component for the position and state of the suspension cylinder. Fig.17 The pressure characteristic curves of the dual circuits / systems of the present invention are shown in Figure 1. Curve 1 is the pressure characteristic curve of the external control circuit, and curve 2 is the pressure characteristic curve of the suspension cylinder inner cavity system. The pressures of the two circuits / systems reach a balance of elastic force at the equilibrium position through their respective pressure action areas.

[0042] When the height of the suspension cylinder needs to be lowered or the suspension cylinder needs to be retracted, the gas-liquid booster pump is started to inject a certain amount of hydraulic oil in the suspension cylinder cavity system into the rodless cavity of the flow control cylinder, and at the same time, a certain amount of hydraulic oil in the rod cavity is injected into the auxiliary oil cavity of the suspension cylinder. The height of the oil-gas suspension cylinder is lowered, and the balance position changes until a new balance position is reached. Fig.26 The figure shows the suspension cylinder in the retracted state. The flow control cylinder can achieve isobaric control by selecting a suitable piston rod / cylinder diameter ratio. Fig.19 The following are the pressure characteristic curves of the system under isobaric control. Curve 1 and Curve 2 are the pressure characteristic curves of the external control circuit and the suspension cylinder cavity system under the original equilibrium state, and Curve 3 and Curve 4 are the pressure characteristic curves of the external control circuit and the suspension cylinder cavity system under the new equilibrium state. Fig.24 As shown in the figure, it is the system stiffness characteristic curve under isobaric control. Curve 1 is the system stiffness characteristic curve under the original equilibrium state, and curve 2 is the system stiffness characteristic curve under the new equilibrium state. Fig.19 and Fig.24 It can be seen that when the height of the suspension cylinder is adjusted under isobaric control, each working position of the suspension cylinder drops synchronously with the equilibrium position, and the working stroke changes.

[0043] When it is necessary to restore the original height of the suspension cylinder or release the suspension cylinder, switch the reversing valve position and start the gas-liquid booster pump to reversely inject the hydraulic oil in the rodless chamber of the flow control cylinder into the suspension cylinder inner chamber system. At the same time, relying on the pressure difference between the two circuits / systems, the quantitative hydraulic oil in the auxiliary oil chamber is discharged back to the rod chamber of the flow control cylinder. When restoring the height of the suspension cylinder, it is necessary to overcome the gravity of the vehicle's sprung mass and rise to the original working height. In the case of non-isobaric control, it is also necessary to overcome the additional pressure in the two circuits / systems. Fig. 27 As shown, this is a system structure diagram for recovering from a compressed state to an initial state.

[0044] When the diameter ratio of the piston rod / cylinder barrel of the flow control cylinder is not the corresponding diameter ratio of the piston rod / cylinder barrel of the suspension cylinder, a non-isobaric control state is formed. Fig.11 The structure shown is the case where the diameter of the flow control cylinder piston rod is zero. Fig.23 The following is the change of the stiffness curve of the height and stroke control of this non-isobaric structure. Curve 1 is the original stiffness curve, and curve 2 is the stiffness curve of the new equilibrium position. Fig.23 It can be seen that although the non-isobaric structure has carried out corresponding control on the balance position of the suspension cylinder, the actual height and stroke control are significantly weakened in the empty / full load state.

[0045] Fig.12 For another extreme case, the flow exchange channel with the suspension cylinder cavity system is disconnected, and the gas-liquid booster pump adopts an open structure to form a single-loop control structure. The pressure characteristics of the suspension cylinder cavity system and the external control loop under this control structure are as follows: Fig.18 shown. Fig.18 In the figure, curve 1 is the pressure characteristic curve of the external control circuit at the original equilibrium position, curve 3 is the pressure characteristic curve of the external control circuit at the new equilibrium position, and curves 2 / 4 are the pressure characteristic curves of the suspension cylinder inner cavity system. Fig.18 It can be seen that during the control process, the pressure characteristics of the suspension cylinder inner cavity system remain unchanged. Fig.21 , 22 The changes of the suspension cylinder stiffness curve under two control forces, curve 1 is the original stiffness curve, and curve 2 is the stiffness curve under the new equilibrium position. Fig.21 , 22 It can be seen that the single-loop control structure still has a weak control over the actual working height of the suspension cylinder, and has a more significant control over the working stroke of the suspension cylinder, but it also significantly changes the system stiffness value under no-load and full-load conditions. For a specific vehicle, the no-load and full-load conditions are relatively fixed, so the single-loop control structure has a certain impact on the smoothness of vehicle operation.

[0046] The dual-circuit equal pressure control structure of the present invention is as follows: Fig.19 , Fig.24 The control of the balance position and the actual working position is accurate and consistent, with small additional pressure and a smooth process, keeping the original empty / full load stiffness characteristics unchanged, so that the control start / start state and the intermediate transition states maintain very good consistency, thus ensuring the smoothness and stability of the system when used alone or in combination with multiple systems.

[0047] The controllable stroke oil-gas suspension cylinder of the present invention has a closed system for the external control circuit and the suspension cylinder inner cavity system. The gas-liquid booster pump / flow control cylinder → external control circuit → suspension cylinder inner cavity system is an isolated step-by-step control, which is a reversible and safe control.

[0048] Fig.28 This is the system structure diagram under normal operation and no-load condition. Fig.29 This is the system structure diagram under normal operation and full load. Fig.28 , 29 It can be seen that during normal operation, flow is exchanged between the cylinder barrel inner cavity and the piston rod inner cavity in the suspension cylinder inner cavity system, and flow is exchanged between the auxiliary oil cavity and the accumulator in the external control circuit, while there is no flow exchange between the gas-liquid booster pump / flow control cylinder and the external control circuit and the suspension cylinder inner cavity system, and the reversing valve inside the gas-liquid booster pump / flow control cylinder is in a fully stopped state, ensuring the stability and reliability of the system operation. Fig.28 In the process, the internal control valve group inside the suspension cylinder is in a no-load state. Fig.29 In the process, the internal control valve group is in full load state. Fig.30 , Fig.31 They are detailed structural diagrams of the internal control valve group under no-load and full-load conditions respectively.

[0049] The internal control valve group is an internal pressure-controlled automatic variable damping structural component, which can sense and determine the working state of the suspension cylinder according to the pressure of the suspension cylinder inner cavity system, and automatically adjust and control the flow and damping coefficient between the cylinder inner cavity (main oil cavity) and the piston rod inner cavity (mixed oil cavity). Fig.16 As shown, this is the variable damping characteristic curve of the internal control valve group which is automatically controlled according to the internal pressure of the system.

[0050] Compared with the prior art, the beneficial technical effects of the present invention are:

[0051] 1. The controllable stroke oil-gas suspension cylinder of the present invention completely isolates the auxiliary oil chamber of the oil-gas suspension cylinder from the inner chamber of the suspension cylinder (including the inner chamber of the cylinder barrel and the inner chamber of the piston rod), and uses the auxiliary oil chamber as the target link for external control to achieve active or semi-active control of the stroke, length and stiffness of the suspension cylinder;

[0052] 2. The controllable stroke oil-gas suspension cylinder of the present invention controls the internal cylinder cavity (main oil cavity) and the mixed piston rod cavity (combined oil cavity) with the internal control valve group as the core, constructing a complete and independent pressure / flow control system, providing the main stiffness / damping mechanical parameters of the suspension cylinder, and realizing the variable damping active control inside the system. Its pressure action area and damping flow area are both the cylinder cavity area;

[0053] 3. The controllable stroke oil-gas suspension cylinder of the present invention is provided with an energy storage device, a control valve and a pipeline outside the oil-gas suspension cylinder, which is connected to the auxiliary oil chamber of the suspension cylinder to construct an independent external control circuit, which can achieve the following three purposes: ① The energy storage device (mixed oil chamber) is used to construct a complete pressure and flow relationship of the external control circuit with the auxiliary oil chamber; ② The control valve is used to establish an external control input port, which also serves as a damping element of the external control circuit itself; ③ The established external control circuit and the suspension cylinder inner cavity system form a new and complete double-chamber counter-pressure opposing structural relationship through the auxiliary oil chamber;

[0054] 4. The external control circuit of the controllable stroke oil-gas suspension cylinder of the present invention is independent of the suspension cylinder inner cavity system. The mechanical parameters of the suspension cylinder inner cavity system are supplemented and corrected through the auxiliary oil cavity, and the suspension cylinder inner cavity system is reversely controlled in terms of stiffness, stroke, state, pressure and other parameters. Its pressure action area and damping flow area are both the annular area of ​​the auxiliary oil cavity;

[0055] 5. The controllable stroke oil-gas suspension cylinder of the present invention constructs a complete suspension cylinder inner cavity structure on the basis of realizing the dual air chamber back pressure opposing structure. The complete structure and parameter association of the relative position, speed, pressure, flow, etc. between the cylinder inner cavity and the piston rod inner cavity are established through the internal control valve group. For the first time, the automatic variable damping function of the suspension cylinder inner cavity system based on the dual air chamber back pressure opposing structure is realized, and a new basic architecture is provided for various variable damping active controls in the future;

[0056] 6. The controllable stroke oil-gas suspension cylinder of the present invention is connected to the suspension cylinder inner cavity system and the external control circuit with a gas-liquid booster pump / flow control cylinder, respectively, to form a closed double-loop equal pressure control system. The gas-liquid booster pump is used as the control actuator of the present invention, and the internal reversing valve is used to perform forward and reverse control and cut-off and closing during normal operation.

[0057] To summarize, the controllable stroke oil-gas suspension cylinder of the present invention constructs the suspension cylinder inner cavity system and the external control circuit by isolating the auxiliary oil chamber from the suspension cylinder inner cavity through the structure; and forms a dual-channel equal pressure and synchronous control system structure with the constructed dual-circuit system through the liquid booster pump / flow control cylinder, thereby realizing reliable and stable height and state control; at the same time, a new type of dual-chamber back-pressure oil-gas suspension cylinder structure is also constructed, and automatic variable damping control in the empty / full load state of the system is realized, opening up a new technical structure of active and semi-active control oil-gas suspension. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0059] Figure 1 It is a structural schematic diagram of a single-chamber double-oil-cavity oil-gas suspension cylinder with a piston rod mounted on the prior art;

[0060] Figure 2 It is a structural schematic diagram of a single-air-chamber and double-oil-chamber oil-gas suspension cylinder with a piston rod placed downward in the prior art;

[0061] Figure 3 It is a structural schematic diagram of a single-chamber three-oil-cavity oil-gas suspension cylinder with a piston rod mounted on the prior art;

[0062] Figure 4 It is a structural schematic diagram of a single air chamber and three oil chamber oil-gas suspension cylinder with a piston rod placed downward in the prior art;

[0063] Figure 5 It is a structural schematic diagram of a single air chamber and three oil chamber oil-gas suspension cylinder with a piston rod placed downward in the prior art;

[0064] Figure 6 It is a structural schematic diagram of a single air chamber, three oil chambers / pressure compensation type oil-gas suspension cylinder with a piston rod mounted on the prior art;

[0065] Figure 7 It is a structural schematic diagram of a three-oil-chamber oil-gas suspension cylinder with a piston rod placed downward and double air chambers connected in series in the prior art;

[0066] Figure 8 It is a structural schematic diagram of a three-chamber oil-gas suspension cylinder with a piston rod placed downward and double air chambers in opposite directions in the prior art;

[0067] Fig. 9 It is a structural schematic diagram of a prior art oil-gas suspension cylinder with a piston rod placed downwardly and double air chambers in opposite directions and three oil chambers;

[0068] Fig.10 It is a structural schematic diagram of the controllable stroke oil-gas suspension cylinder of the present invention;

[0069] Fig.11 It is a structural schematic diagram of non-isobaric control in a controllable stroke oil-gas suspension cylinder of the present invention;

[0070] Fig.12 It is a structural schematic diagram of a single-channel control in a controllable-stroke oil-gas suspension cylinder of the present invention;

[0071] Fig.13 This is the stiffness characteristic curve of the traditional oil-gas suspension cylinder;

[0072] Fig.14 It is the stiffness characteristic curve of the oil-gas suspension cylinder with double air chamber back-pressure opposed structure;

[0073] Fig.15 This is the damping characteristic curve of the traditional oil-gas suspension cylinder;

[0074] Fig.16 The variable damping characteristic curve diagram of the controllable stroke oil-gas suspension cylinder of the present invention;

[0075] Fig.17 The system pressure characteristic curve diagram of the controllable stroke oil-gas suspension cylinder of the present invention;

[0076] Fig.18 The pressure characteristic curve diagram of the stroke control system of the single-channel control structure in the controllable stroke oil-gas suspension cylinder of the present invention;

[0077] Fig.19 The pressure characteristic curve diagram of the controllable stroke oil-gas suspension cylinder height / state control system of the present invention;

[0078] Fig. 20 The stiffness characteristic curve of the controllable stroke oil-gas suspension cylinder of the present invention;

[0079] Fig.21 The stroke control stiffness characteristic curve of the single-channel control structure in the controllable stroke oil-gas suspension cylinder of the present invention;

[0080] Fig. 22 The stroke control stiffness characteristic curve of the single-channel control structure in the controllable stroke oil-gas suspension cylinder of the present invention;

[0081] Fig.23 The stroke control stiffness characteristic curve of the non-isobaric control structure in the controllable stroke oil-gas suspension cylinder of the present invention;

[0082] Fig.24 The height / state control stiffness characteristic curve of the medium-pressure control structure in the controllable stroke oil-gas suspension cylinder of the present invention;

[0083] Fig.25 System structure diagram of the controllable stroke oil-gas suspension cylinder of the present invention;

[0084] Fig.26 The structural diagram of the controllable stroke oil-gas suspension cylinder stowed state system of the present invention;

[0085] Fig. 27 The structure diagram of the controllable stroke oil-gas suspension cylinder release state system of the present invention;

[0086] Fig.28 The structure diagram of the controllable stroke oil-gas suspension cylinder no-load state system of the present invention;

[0087] Fig.29 The structure diagram of the controllable stroke oil-gas suspension cylinder in full load state system of the present invention;

[0088] Fig.30 A partial enlarged view of the no-load state of the pressure-controlled variable damping structure of the internal control valve group in the controllable stroke oil-gas suspension cylinder of the present invention;

[0089] Fig.31 A partial enlarged view of the fully loaded state of the pressure-controlled variable damping structure of the internal control valve group in the controllable stroke oil-gas suspension cylinder of the present invention.

[0090] Explanation of the reference numerals in the accompanying drawings: 10. piston rod; 11. piston; 12. internal control valve group; 13. cylinder barrel; 14. sealing seat ring; 15. accumulator; 16. control valve; 17. gas-liquid booster pump; 18. flow control cylinder; 19. reversing valve; 20. suspension cylinder cavity; 21. auxiliary oil cavity; 22. cylinder barrel cavity; 23. piston rod cavity; 25. pipeline; 30. suspension cylinder cavity system; 31. external control interface; 32. external control interface; 40. external control circuit; 41. external control interface; 42. external control interface. DETAILED DESCRIPTION

[0091] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0092] In the description of the present invention, it should be understood that the terms "length", "width", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0093] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0094] The embodiment of the present specification provides a controllable stroke oil-gas suspension cylinder, including a cylinder barrel, a piston rod, a piston, an internal control valve group, a sealing seat ring, an accumulator, a control valve, a gas-liquid booster pump and a flow control cylinder. A piston is arranged in the cylinder barrel, a piston rod is connected to the piston, and the piston rod is sealed to the upper part of the cylinder barrel by a sealing seat ring.

[0095] Among them, the cylinder barrel, piston rod and piston form a suspension cylinder inner cavity inside the suspension cylinder, the suspension cylinder inner cavity is a rodless cavity, an internal control valve group is arranged at the bottom of the piston rod, and the internal control valve group divides the suspension cylinder inner cavity into a cylinder barrel inner cavity and a piston rod inner cavity, the cylinder barrel inner cavity is filled with hydraulic oil and an external control interface is arranged at the bottom, and the piston rod inner cavity is filled with hydraulic oil and nitrogen, wherein the cylinder barrel inner cavity and the piston rod inner cavity are connected through the damping channel on the internal control valve group to form an independent suspension cylinder inner cavity system.

[0096] In addition, the cylinder barrel, the sealing seat ring, the piston rod and the piston form an auxiliary oil chamber between the side walls of the waist of the suspension cylinder. The auxiliary oil chamber is a rod chamber, which is filled with hydraulic oil and is completely isolated from the inner cavity of the suspension cylinder. A connecting port is set at the position of the cylinder barrel near the sealing seat ring. The auxiliary oil chamber is connected to an external control valve and an accumulator through a pipeline to form an independent external control circuit.

[0097] At the same time, the gas-liquid booster pump includes a reversing valve that can implement oil circuit reversing and closing control, and is internally connected to the rodless chamber of the flow control cylinder. The gas-liquid booster pump is provided with an external control interface, and the external control interface of the gas-liquid booster pump is connected to the external control interface of the suspension cylinder inner chamber system; the flow control cylinder is provided with an external control interface, and the external control interface of the flow control cylinder is arranged in the rod chamber and is connected to the external control interface of the external control loop; thereby forming two independent closed systems, forming two independent channels for synchronous control of the suspension cylinder stroke, stiffness and height.

[0098] At this time, the control valve is the input port for externally controlling the suspension cylinder stroke, stiffness and height, and serves as a damping / flow control element within the external control loop, and is provided with an external control interface.

[0099] In addition, the auxiliary oil chamber in the external control circuit and the cylinder barrel inner chamber in the suspension cylinder inner chamber system form a double air chamber counter-pressure opposing structure.

[0100] In addition, the accumulator is filled with hydraulic oil and nitrogen.

[0101] At this time, the inner cavity of the suspension cylinder maintains a complete inner cavity structure and pressure / flow relationship, and the internal control valve group serves as a damping control component between the inner cavity of the cylinder barrel and the inner cavity of the piston rod.

[0102] The control method of the controllable stroke oil-gas suspension cylinder comprises:

[0103] 1) When it is necessary to reduce the stroke of the suspension cylinder, the reversing valve is placed in the retracted position, the gas-liquid booster pump is started, and a certain amount of hydraulic oil in the suspension cylinder inner cavity system is injected into the rodless cavity of the flow control cylinder, and at the same time, a certain amount of hydraulic oil in the rod cavity of the flow control cylinder is injected into the auxiliary oil cavity of the suspension cylinder through an external control circuit; the stroke of the suspension cylinder is reduced, and the balance position changes until a new balance position is reached; wherein, the piston rod / cylinder barrel area ratio selected by the flow control cylinder is associated with the piston rod / cylinder barrel area ratio of the suspension cylinder, and an isobaric control state or a non-isobaric control state can be achieved; when the piston rod / cylinder barrel area ratio selected by the flow control cylinder is consistent with the piston rod / cylinder barrel area ratio of the suspension cylinder, it is an isobaric control state, and the height of the suspension cylinder is adjusted in the isobaric control state, and each working position of the suspension cylinder drops synchronously with the balance position, and the working stroke changes;

[0104] 2) When the stroke of the suspension cylinder needs to be increased, the reversing valve is placed in the release position, the gas-liquid booster pump is started, and the hydraulic oil in the rodless chamber of the flow control cylinder is reversely injected into the suspension cylinder inner chamber system. At the same time, relying on the pressure difference between the two circuits / systems, the quantitative hydraulic oil in the auxiliary oil chamber of the suspension cylinder is discharged back to the rod chamber of the flow control cylinder through the external control circuit;

[0105] 3) When there is no need to control or change the stroke of the suspension cylinder, turn off and start the gas-liquid booster pump and place the reversing valve in the cut-off position.

[0106] The technical solutions provided by various embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0107] Example 1

[0108] The controllable stroke oil-gas suspension cylinder of embodiment 1 of the present invention comprises a piston rod 10, a piston 11, an internal control valve group 12, a cylinder barrel 13, a sealing seat ring 14, an accumulator 15, a control valve 16, a gas-liquid booster pump 17, a flow control cylinder 18, a reversing valve 19, and a pipeline 25. The cylinder barrel 13, the piston rod 10, and the piston 11 form a suspension cylinder inner cavity 20 (rodless cavity) inside the suspension cylinder. The cylinder barrel 13, the sealing seat ring 14, the piston rod 10, and the piston 11 form a secondary oil cavity 21 (rod cavity) between the side walls of the waist of the suspension cylinder. The secondary oil cavity 21 is filled with hydraulic oil and is completely isolated from the suspension cylinder inner cavity 20. The suspension cylinder inner cavity 20 is divided into a cylinder barrel inner cavity 22 and a piston rod inner cavity 23 by the internal control valve group 12 at the bottom of the piston rod 10. The cylinder barrel inner cavity 22 is filled with hydraulic oil, and the piston rod inner cavity 23 is filled with hydraulic oil and nitrogen. The cylinder inner cavity 22 and the piston rod inner cavity 23 are connected through the damping channel on the internal control valve group 12 to form a complete and independent suspension cylinder inner cavity system 30. The auxiliary oil chamber 21 is provided with an external connection port at a position of the cylinder 13 near the sealing seat ring 14, and is connected to the accumulator 15 and the control valve 16 through the pipeline 25 to form an independent external control circuit 40.

[0109] The suspension cylinder cavity system 30 is enclosed in the suspension cylinder cavity 20, and is composed of the piston rod cavity 23, the cylinder cavity 22 and the internal control valve group 12. An external control interface 31 is provided at the bottom of the cylinder cavity 22. The external control circuit 40 is composed of the auxiliary oil cavity 21, the accumulator 15, the control valve 16 and the pipeline 25. The control valve 16 is provided with an external control interface 41. The external control circuit 40 is completely isolated from the suspension cylinder cavity system 30 and is independent of each other.

[0110] The auxiliary oil chamber 21 in the external control circuit 40 and the cylinder inner chamber 22 in the suspension cylinder inner chamber system 30 form a double air chamber counter-pressure opposing structure relationship. The accumulator 15 is filled with hydraulic oil and nitrogen. The auxiliary oil chamber 21 serves as the target link for externally controlling the height and stroke of the suspension cylinder. The control valve 16, in addition to being the input port for externally controlling the height, stroke and stiffness of the suspension cylinder, also serves as the damping / flow control element of the external control circuit 40 itself.

[0111] The gas-liquid booster pump 17 contains a reversing valve 19, which forms a component with the flow control cylinder 18 to control the stroke and height of the suspension cylinder. The internal control interface of the gas-liquid booster pump 17 is connected to the rodless cavity of the flow control cylinder 18, and the external control interface 32 can be used for real-time external control. The external control interface 42 of the flow control cylinder 18 is set in the rod cavity. The reversing valve 19 can implement the reversing and closing control of the oil circuit. The external control interface 32 of the gas-liquid booster pump 17 and the external control interface 42 of the flow control cylinder 18 are respectively connected to the external control interface 31 of the suspension cylinder inner cavity system 30 and the external control interface 41 of the external control loop 40, forming two independent closed systems, forming two channels for continuous isobaric / synchronous control of the height / stroke of the suspension cylinder. Fig.25The figure shows the structure diagram of the controllable stroke oil-gas suspension cylinder system. Fig.10 It is a structural diagram.

[0112] When the suspension cylinder is compressed or stretched, the volume of the cylinder cavity 22 and the auxiliary oil cavity 21 both change, and both are variable oil cavities. For the suspension cylinder cavity system 30, the flow is exchanged between the cylinder cavity 22 and the piston rod cavity 23, and the damping flow area is the cross-sectional area of ​​the cylinder cavity 22. For the external control circuit 40, the flow is exchanged between the auxiliary oil cavity 21 and the accumulator 15, and the damping flow area is the cross-sectional area of ​​the auxiliary oil cavity 21. The damping flow of the suspension cylinder is the sum of the damping flow of the suspension cylinder cavity system 30 and the external control circuit 40. The suspension cylinder cavity system 30 and the external control circuit 40 form a double air chamber counter-pressure opposing structure through the cylinder cavity 22 and the auxiliary oil cavity 21. The pressure action area of ​​the suspension cylinder cavity system 30 is the cross-sectional area of ​​the cylinder cavity 22. The pressure action area of ​​the external control circuit 40 is the cross-sectional area of ​​the auxiliary oil cavity 21. The overall stiffness of the suspension cylinder is formed by the superposition of the pressure and pressure action area of ​​the suspension cylinder cavity system 30 and the pressure and pressure action area of ​​the external control circuit 40. See also Fig. 20 Curve 1 is the stiffness curve of the suspension cylinder inner cavity system 30, curve 2 is the stiffness curve of the external control loop 40, and curve 3 is the comprehensive stiffness curve of the suspension cylinder system. Fig. 20 It can be seen that the external control loop 40 has made a good correction to the stiffness characteristics of the suspension cylinder inner cavity system 30 in the initial stage.

[0113] The internal control valve group 12 is a pressure-controlled automatic variable damping control component installed at the bottom of the piston rod 10. It senses the system pressure of the suspension cylinder inner cavity system 30 to achieve automatic variable damping control when the suspension cylinder is empty or fully loaded. Fig.16 , the empty / full load automatic variable damping control characteristic curve of the present invention. Fig.30 , Fig.31 It is the structural state diagram of the internal control valve group 12 in the empty / full load state. Fig.30 , Fig.31 It can be seen that the internal control valve group 12 is based on the complete structure of the suspension cylinder cavity 20 and the complete position / speed and pressure / flow relationship between the internal cylinder cavity 22 and the piston rod cavity 23. Fig.28 , Fig.29 As shown, it is a system structure diagram of the controllable stroke oil-gas suspension cylinder of the present invention in empty / full load state.

[0114] When the suspension cylinder needs to be lowered or retracted, the reversing valve 19 is placed in the retracted position, the gas-liquid booster pump 17 is started, and a certain amount of hydraulic oil in the suspension cylinder inner cavity system 30 is injected into the rodless cavity of the flow control cylinder 18, and a certain amount of hydraulic oil in the rod cavity on the other side is injected into the auxiliary oil cavity 21 of the external control circuit 40. The height of the suspension cylinder is lowered, and the balance position changes until a new balance position is reached. Fig.26 The diagram shows the system structure of the suspension cylinder in the retracted state. The piston rod / cylinder area ratio selected by the flow control cylinder 18 is consistent with the area ratio of the suspension cylinder piston rod 10 / cylinder 13, which is an isobaric control state. Fig.19 As shown, the system pressure characteristic curve under isobaric control. Curve 1 / curve 2 are respectively the pressure characteristic curves of the external control loop 40 and the suspension cylinder inner cavity system 30 in the original equilibrium state, and curve 3 / curve 4 are respectively the pressure characteristic curves of the external control loop 40 and the suspension cylinder inner cavity system 30 in the new equilibrium state. Fig.24 As shown in the figure, it is the system stiffness characteristic curve under isobaric control. Curve 1 is the system stiffness characteristic curve under the original equilibrium state, and curve 2 is the system stiffness characteristic curve under the new equilibrium state. Fig.19 and Fig.24 It can be seen that when the height of the suspension cylinder is adjusted under the isobaric control state, each working position of the suspension cylinder drops synchronously with the equilibrium position, and the working stroke changes.

[0115] When it is necessary to restore the original height of the suspension cylinder or release the suspension cylinder, the reversing valve 19 is placed in the release position, the gas-liquid booster pump 17 is started, and the hydraulic oil in the rodless cavity of the flow control cylinder 18 is reversely injected into the suspension cylinder inner cavity system 30. At the same time, the quantitative hydraulic oil in the auxiliary oil cavity 21 of the external control circuit 40 is discharged back to the rod cavity of the flow control cylinder 18 by relying on the pressure difference between the two circuits / systems. Fig. 27 The figure shows the system structure diagram of the suspension cylinder release state.

[0116] When there is no need to adjust the height of the suspension cylinder or the vehicle is operating normally, the gas-liquid booster pump 17 is turned off and started and the reversing valve 19 is placed in the cut-off position.

[0117] The controllable stroke oil-gas suspension cylinder of the present invention isolates the auxiliary oil chamber as the target link of external control, constructs two independent control loop systems, namely the suspension cylinder inner cavity system and the external control loop, and forms two isobaric and synchronous control channels for the height and stroke control of the suspension cylinder. The control input ports of the external control loop and the suspension cylinder inner cavity system and the damping control structure of the loop / system itself are comprehensively set, maintaining the integrity of the suspension cylinder inner cavity and the complete correlation structure of the position, speed, pressure, flow, etc. between the piston rod inner cavity and the cylinder barrel inner cavity, realizing multiple combined functions such as active external control, dual air chamber back pressure opposing structure, and internal active variable damping control, eliminating the shortcomings of traditional structures and realizing complete and excellent mechanical properties. The overall function and structure of the suspension cylinder are complete, and the internal structure is simple, which maximizes the structural efficiency of the oil-gas suspension cylinder. While effectively implementing external active control, the stability and reliability of the suspension cylinder inner cavity system are ensured.

[0118] The controllable-stroke oil-gas suspension cylinder structure of the present invention is the first in existing literature and products in terms of key technical functions such as isolation of the auxiliary oil chamber and the inner cavity of the suspension cylinder, independent dual-circuit system, equal-pressure and synchronous dual-channel control, dual-chamber opposed structure, variable stiffness and variable damping, etc., and provides a new basic suspension cylinder structure with complete and reliable structure and functions for further expanding active and semi-active oil-gas suspension.

[0119] The technical solution proposed in the present invention, based on the oil-gas suspension structure, has obvious advantages in terms of load capacity, control capacity and cost structure, etc. This provides an efficient and economical technical means and product direction for improving chassis performance of many products such as ordinary vehicles, load-carrying vehicles and special vehicles, and is extremely valuable.

[0120] It should be noted that: 1. The closed dual-loop isobaric control system constructed by the present invention includes active control of the height and state of the suspension cylinder, automatic variable damping control of no-load and full-load, and a dual-chamber back-pressure opposing structure established by the external control loop and the suspension cylinder inner cavity system, which can be controlled individually or operated in combination.

[0121] When the vehicle is adjusting its height and state, the gas-liquid booster pump / flow control cylinder and the suspension cylinder inner cavity / auxiliary oil cavity are synchronized and isobarically exchanged with each other ( Fig.24 ). The starting position and the intermediate state transition smoothly.

[0122] When the vehicle is running, the flow is exchanged between the cylinder bore and the piston rod in the suspension cylinder cavity system, and the flow is exchanged between the auxiliary oil cavity and the accumulator in the external control loop. The external control loop fully supplements and corrects the mechanical parameters of the suspension cylinder cavity system, outputting good stiffness characteristics ( Fig. 20 The suspension cylinder cavity system is based on a complete internal structure and relies on the internal control valve group to output good variable damping characteristics ( Fig.16 ).

[0123] When running without load, the working pressure in the suspension cylinder cavity is in a low pressure state. The internal control valve group opens the variable damping channel, and the suspension cylinder cavity system is in a low damping coefficient state. When running with full load, the working pressure in the suspension cylinder cavity is in a high pressure state. The internal control valve group closes the variable damping channel, and the suspension cylinder cavity system is in a high damping coefficient state. When running without load or full load, the suspension cylinder can output good damping characteristics.

[0124] 2. The dual-chamber back-pressure opposed suspension cylinder structure of the present invention maintains a complete and simple suspension cylinder inner cavity structure, as well as a complete connection between the cylinder barrel inner cavity and the piston rod inner cavity, to construct a complete suspension cylinder inner cavity system and an independent external control loop. The suspension cylinder inner cavity system provides the main parameters of the suspension cylinder, and the external control loop provides the control parameters of the system. The independent suspension cylinder inner cavity system and the external control loop structure ensure the stability and reliability of the suspension system.

[0125] 3. The pressure action area and damping flow area of ​​the suspension cylinder inner cavity system of the present invention are the cylinder inner cavity area, and the pressure action area and damping flow area of ​​the external control circuit are the auxiliary oil cavity area. The external control circuit and the suspension cylinder inner cavity system form a counter-pressure opposing structure, which eliminates the hard points in the stroke, forms a zero-crossing balance point of the suspension cylinder, and outputs good stiffness characteristics.

[0126] 4. The variable damping adaptive control of the present invention is based on the complete structure of the suspension cylinder cavity, as well as the complete structure and association of the relative position, speed, pressure, flow rate, etc. between the cylinder cavity and the piston rod cavity. The internal control valve group is a variable damping control mechanism based on the internal pressure of the system, which realizes dual-point, steady-state variable damping flow control, F = f (p, v), Fig.16 The system automatically matches two damping characteristic curves in the empty / full load state. The variable damping control flow area of ​​the present invention is the cylinder inner cavity area, which has reached the maximum state of the cylinder structure.

[0127] Among them, the core of the internal control valve group is to build a valve core assembly and a variable damping structure with internal pressure as the control input to form an internal variable damping channel. The valve core assembly contains a closed pressure chamber for system identification, and the internal spring provides the valve core reference pressure to drive the valve core to move. The valve core reference pressure is set between the no-load pressure and the full-load pressure of the suspension cylinder. The valve core is arranged with two sets of internal / external damping holes and a one-way valve, which cooperate with the valve core seat ring to form a fixed damping channel and a controllable damping channel. The fixed damping channel is long-passed. The controllable damping channel opens when the valve core is extended, and the controllable damping channel closes when the valve core is retracted. The valve core assembly also includes a damping chamber and a damping ring, which are used to control the steady-state response of the valve core itself. Fig.30 , Fig.31 , which is the working structure diagram of the internal control valve group under empty / full load conditions.

[0128] For the internal control valve group, it is necessary to explain that: 1) the variable damping structure, variable damping channel and automatic control structure built inside the cylinder body use the system pressure in the suspension cylinder cavity as the input parameter of the variable damping control, F = f (p, v); 2) the valve core reference pressure is used to identify the no-load pressure and full-load pressure inside the system, and is superimposed with the system pressure to push the valve core to maintain two specific positions of extension and retraction. Therefore, it is a typical two-point variable damping control, see Fig.16 ; 3) The damping chamber and damping ring in the valve core assembly are used to control the steady-state response of the valve core itself. The pressure fluctuation and pressure shock inside the system will not cause transient start-up and rigid impact of the valve core. Therefore, the system is a steady-state control; 4) The present invention is currently the only suspension cylinder structure based on a dual-chamber back-pressure opposed structure that realizes external active control and internal variable damping automatic control, providing a new basic oil-gas suspension cylinder structure for future technological development.

[0129] As a structural solution for actively controlling the height and state of an oil-gas suspension under a mechanical / hydraulic control mode, the present invention has obvious innovative characteristics and application value.

[0130] Example 2

[0131] The control method of the controllable stroke oil-gas suspension cylinder of embodiment 2 of the present invention comprises:

[0132] 1) When it is necessary to lower the height of the suspension cylinder or to retract the suspension cylinder, the reversing valve 19 is placed in the retracted position, the gas-liquid booster pump 17 is started, and a certain amount of hydraulic oil in the suspension cylinder inner cavity system 30 is injected into the rodless cavity of the flow control cylinder 18, and at the same time, a certain amount of hydraulic oil in the rod cavity on the other side is injected into the auxiliary oil cavity 21 of the external control circuit 40; the height of the suspension cylinder is lowered, and the balance position changes until a new balance position is reached. The piston rod / cylinder area ratio selected by the flow control cylinder 18 is consistent with the area ratio of the piston rod / cylinder of the suspension cylinder, which is an isobaric control state. Under the isobaric control state, the height of the suspension cylinder is adjusted, and each working position of the suspension cylinder drops synchronously with the balance position, and the working stroke changes;

[0133] 2) When it is necessary to restore the original height of the suspension cylinder or release the suspension cylinder, the reversing valve 19 is placed in the release position, the gas-liquid booster pump 17 is started, and the hydraulic oil in the rodless cavity of the flow control cylinder 18 is reversely injected into the suspension cylinder inner cavity system 30. At the same time, relying on the pressure difference between the two circuits / systems, the quantitative hydraulic oil in the auxiliary oil cavity 21 of the external control circuit 40 is discharged back to the rod cavity of the flow control cylinder 18;

[0134] 3) When there is no need to adjust the height of the suspension cylinder or the vehicle is operating normally, the gas-liquid booster pump 17 is turned off and started, and the reversing valve 19 is placed in the cut-off position.

[0135] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A controllable stroke oil-gas suspension cylinder, characterized in that: It includes a cylinder barrel, a piston rod, a piston, an internal control valve group, a sealing seat ring, an accumulator, a control valve, a gas-liquid booster pump and a flow control cylinder. The piston is arranged in the cylinder barrel, the piston rod is connected to the piston, and the piston rod is sealed to the upper part of the cylinder barrel through the sealing seat ring; The cylinder barrel, the piston rod and the piston form a suspension cylinder inner cavity inside the suspension cylinder, the suspension cylinder inner cavity is a rodless cavity, the bottom of the piston rod is provided with the internal control valve group, and the internal control valve group divides the suspension cylinder inner cavity into a cylinder barrel inner cavity and a piston rod inner cavity, the cylinder barrel inner cavity is filled with hydraulic oil and an external control interface is provided at the bottom, and the piston rod inner cavity is filled with hydraulic oil and nitrogen, wherein the cylinder barrel inner cavity and the piston rod inner cavity are connected through the damping channel on the internal control valve group to form an independent suspension cylinder inner cavity system; The cylinder barrel, the sealing seat ring, the piston rod and the piston form a secondary oil chamber between the side walls of the waist of the suspension cylinder. The secondary oil chamber is a rod chamber, the secondary oil chamber is filled with hydraulic oil and is completely isolated from the inner cavity of the suspension cylinder. The secondary oil chamber is provided with a connection port at a position of the cylinder barrel near the sealing seat ring. The secondary oil chamber is externally connected to the control valve and the accumulator through a pipeline to form an independent external control circuit. The gas-liquid booster pump includes a reversing valve that can implement oil circuit reversing and closing control, and is internally connected to the rodless chamber of the flow control cylinder. The gas-liquid booster pump is provided with an external control interface, and the external control interface of the gas-liquid booster pump is connected to the external control interface of the suspension cylinder inner chamber system; the flow control cylinder is provided with an external control interface, and the external control interface of the flow control cylinder is arranged in the rod chamber and connected to the external control interface of the external control circuit; thereby forming two independent closed systems, forming two independent channels for synchronous control of the suspension cylinder stroke, stiffness and height.

2. The controllable stroke oil-gas suspension cylinder according to claim 1, characterized in that: The control valve is an input port for externally controlling the stroke, stiffness and height of the suspension cylinder, and serves as a damping / flow control element within the external control loop, and is provided with an external control interface.

3. The controllable stroke oil-gas suspension cylinder according to claim 1, characterized in that: The auxiliary oil chamber in the external control circuit and the cylinder inner chamber in the suspension cylinder inner chamber system form a double air chamber counter-pressure opposing structure.

4. The controllable stroke oil-gas suspension cylinder according to claim 1, characterized in that: The energy accumulator is filled with hydraulic oil and nitrogen.

5. The controllable stroke oil-gas suspension cylinder according to any one of claims 1 to 4, characterized in that: The inner cavity of the suspension cylinder maintains a complete inner cavity structure and pressure / flow relationship, and the internal control valve group serves as a damping control component between the inner cavity of the cylinder barrel and the inner cavity of the piston rod.

6. A control method for a controllable stroke oil-gas suspension cylinder, characterized in that: include: 1) When the suspension cylinder stroke needs to be reduced, the reversing valve is placed in the retracted position, the gas-liquid booster pump is started, and a certain amount of hydraulic oil in the suspension cylinder inner cavity system is injected into the rodless cavity of the flow control cylinder, and at the same time, a certain amount of hydraulic oil in the rod cavity of the flow control cylinder is injected into the auxiliary oil cavity of the suspension cylinder through the external control circuit; the suspension cylinder stroke is reduced, and the balance position changes until a new balance position is reached; wherein, the piston rod / cylinder area ratio selected by the flow control cylinder is associated with the piston rod / cylinder area ratio of the suspension cylinder, and an isobaric control state or a non-isobaric control state can be achieved; 2) When the stroke of the suspension cylinder needs to be increased, the reversing valve is placed in the release position, the gas-liquid booster pump is started, and the hydraulic oil in the rodless chamber of the flow control cylinder is reversely injected into the suspension cylinder inner chamber system. At the same time, relying on the pressure difference between the two circuits / systems, the quantitative hydraulic oil in the auxiliary oil chamber of the suspension cylinder is discharged back to the rod chamber of the flow control cylinder through the external control circuit; 3) When there is no need to control or change the stroke of the suspension cylinder, turn off and start the gas-liquid booster pump and place the reversing valve in the cut-off position.

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