A high-energy-density hollow piston rod hydraulic accumulator and its working method

Abstract

This invention discloses a high-energy-density hollow piston rod hydraulic accumulator and its working method, belonging to the field of hydraulic energy storage technology. It includes a cylindrical cylinder and a gas cylinder. The bottom of the cylinder has a liquid chamber end cap sealing the bottom end, and the top of the cylinder has a gas chamber end cap sealing the top end. A piston is located in the middle of the cylinder, and a hollow piston rod penetrates the gas chamber end cap. The rodless chamber in the cylinder, separated by the piston, is a liquid chamber filled with hydraulic oil. The rodless chamber in the cylinder, separated by the piston, is a gas chamber. A gas chamber port is located on the cylinder side wall near the gas chamber end cap, and the gas chamber port is connected to the gas cylinder via a high-pressure pipe. The liquid chamber end cap has a liquid chamber oil inlet communicating with the liquid chamber. The hollow piston rod is entirely sealed, with a through hole on the side wall near the piston connecting to the inner cavity of the hollow piston rod. This increases the initial volume of the gas chamber, improves the energy storage density of the accumulator, and simultaneously reduces the weight of the hollow piston rod itself, thus reducing production costs.

Description

Technical Field

[0001] This invention relates to the field of hydraulic energy storage technology, and is particularly applicable to a high-energy-density hollow piston rod hydraulic accumulator and its working method. Background Technology

[0002] With the rapid development of the global economy, energy conservation in construction machinery is receiving increasing attention. A significant challenge facing the construction machinery market is its substantial energy consumption. Hydraulic systems are key components of construction machinery, widely used due to their high power density and output force. However, during the operation of various large construction machines, a large amount of high-pressure oil flows directly back to the oil tank, resulting in significant energy waste. Therefore, improving energy utilization efficiency has become a crucial means of achieving energy conservation.

[0003] To recover this energy and convert it into mechanical, electrical, and hydraulic energy for reuse, a series of energy-saving methods have been proposed. Among them, hydraulic accumulators are widely used in various hydraulic energy-saving systems due to their advantages such as fast charging and discharging speed, high energy conversion efficiency, and compact structure. Based on their structure, accumulators can be divided into spring-type, piston-type, and air-bladder-type. Piston-type accumulators are a commonly used hydraulic energy storage device in excavator hydraulic systems. Piston-type accumulators recover hydraulic energy by storing oil in an oil chamber, while simultaneously moving the piston to compress the air chamber, thus converting the hydraulic energy into gas compression energy for storage. When the system needs it, the air chamber releases the energy, achieving a reverse energy conversion to replenish the hydraulic system.

[0004] Hydraulic accumulators, as energy storage elements, have fewer energy conversion stages compared to other energy storage elements, resulting in higher energy storage efficiency. Furthermore, hydraulic accumulators can achieve rapid charging and discharging of hydraulic oil and can absorb hydraulic shocks, eliminating pulsations. However, their energy density is far lower than commonly used energy storage elements such as fuel cells, and they also suffer from disadvantages such as large size and high cost.

[0005] Energy density, power density, and efficiency are three important indicators of hydraulic energy storage. Currently, the high power density of hydraulic accumulators ensures rapid energy storage and release. However, to achieve better energy storage performance and reduce the size and cost of the accumulator, further improvements are needed to ensure sufficient energy storage and high energy utilization during operation. Therefore, research on hydraulic energy storage mainly focuses on improving efficiency and energy density.

[0006] High energy storage density in accumulators can be expressed in two ways: one is that for the same gas volume and initial pressure, the pressure change in the liquid chamber is small when storing the same volume of oil; the other is that for the same gas volume and initial pressure, the pressure change in the liquid chamber is the same, but the volume of oil stored is large. Currently, most accumulators utilize the compressibility of gases for energy storage, with nitrogen being the most common gas. Compression and release follow the gas law. Under high-pressure conditions, accumulators typically require high pre-charge pressure and initial volume to meet energy storage requirements. Therefore, accumulators suffer from high cost and large size, resulting in relatively low energy storage density. Summary of the Invention

[0007] Purpose of the invention: To address the shortcomings of existing technologies, this invention proposes a high-energy-density hollow piston rod hydraulic accumulator and its working method. During compression, the force-bearing areas of the liquid chamber and the gas chamber are different, which improves the energy storage density of the accumulator. Moreover, it is lightweight and effectively reduces production costs.

[0008] Technical Objective: To achieve the above-mentioned technical objective, the present invention provides a high-energy-density hollow piston rod hydraulic accumulator, comprising a cylindrical cylinder and a gas cylinder. The bottom of the cylinder is provided with a liquid chamber end cap sealing the bottom end of the cylinder, and the top of the cylinder is provided with a gas chamber end cap sealing the top end of the cylinder. A piston is located in the middle of the cylinder, and a hollow piston rod is provided on the piston, penetrating the gas chamber end cap. The rodless chamber in the cylinder, separated by the piston, is a liquid chamber filled with hydraulic oil, and the rodless chamber in the cylinder, separated by the piston, is a gas chamber. A gas chamber port is provided on the cylinder side wall near the gas chamber end cap, and the gas chamber port is connected to the gas cylinder via a high-pressure pipe. The liquid chamber end cap is provided with a liquid chamber oil inlet communicating with the liquid chamber. The hollow piston rod is entirely sealed, with a through hole on the side wall near the piston connecting to the inner cavity of the hollow piston rod. This allows the space inside the hollow piston rod to serve as part of the gas volume of the gas chamber, increasing the initial volume of the gas chamber, improving the energy storage density of the accumulator, and simultaneously reducing the weight of the hollow piston rod itself, thus reducing production costs.

[0009] Furthermore, a sealing ring is provided between the piston and the inner wall of the cylinder, and a sealing ring is installed between the inner wall of the hollow piston rod and the end cover of the gas chamber.

[0010] Furthermore, the hollow piston rod and piston are connected by a spherical hinge, thereby reducing the precision requirements of machining.

[0011] A method for operating a high-energy-density hollow piston rod hydraulic accumulator includes the following steps: The high-energy-density hollow piston rod hydraulic accumulator relies on the compression and expansion of the gas volume within the gas chamber to achieve the filling and discharging of the liquid chamber from the oil inlet. During energy storage, the piston is initially located at the bottom of the cylinder, i.e., the liquid chamber space is zero. High-pressure oil enters the liquid chamber through the oil inlet, pushing the piston towards the gas chamber, compressing the gas within the gas chamber, and converting hydraulic energy into the internal energy of the gas in the gas chamber and gas cylinder. The area of ​​action of the gas on the piston is smaller than that of the liquid on the piston. The volume within the hollow piston rod communicates with the gas chamber, thereby increasing the accumulator's stored energy. With the same gas chamber volume, compared to a traditional piston accumulator, this increases the energy storage density. When the energy storage reaches its maximum, the gas chamber pressure is greater than the liquid chamber pressure. times.

[0012] Furthermore, in the initial state during energy storage, with the piston at the bottom of the cylinder, neglecting oil compression, internal and external leakage, and friction, when the piston rises at a constant speed, the force exerted by the liquid chamber on the hollow piston rod is:

[0013] P y1 A2 = P q1 A1 (6)

[0014] Since the air chamber (7) has a hollow piston rod (5) occupying part of the area, the force-bearing area of ​​the air chamber (7) on the piston (4) is smaller than the force-bearing area of ​​the liquid chamber (3) A1 < A2.

[0015] In the final state, the pressure in the liquid chamber gradually increases to its maximum value and balances with the pressure in the gas chamber. During this process, the piston moves to the equilibrium position, and the force exerted by the liquid chamber on the hollow piston rod is:

[0016] P y2 A2 = P q2 A1 (7)

[0017] Combining equations (6) and (7), the air chamber pressure P is obtained. q and fluid chamber pressure P y The relationship between them:

[0018]

[0019] The relationship between the change in air chamber volume ΔV and the change in liquid chamber volume ΔV2:

[0020]

[0021] According to the gas law, if the pressure in the gas chamber is P q1 Rise to P q2 The following relationship must be satisfied:

[0022] P q1 V q1n =P q2 V q2 n (10)

[0023] In the formula: P y1 P represents the initial high-pressure oil pressure in the lower chamber; y2 The pressure of the lower chamber high-pressure oil in the final state; P q1 P represents the initial pressure of the air chamber. q2 V represents the pressure in the air chamber at the final state; A1 is the effective working area of ​​the upper air chamber; A2 is the effective working area of ​​the lower piston, A2 > A1; q1 V is the initial volume of the air chamber; q2 The final volume of the air chamber is ΔV. y ΔV represents the change in the liquid chamber volume of the accumulator of this invention. q This represents the change in air cavity volume;

[0024] Substituting equation (8) into equation (10) yields...

[0025]

[0026] Substituting equation (11) into equation (9), we can obtain the result when the liquid chamber pressure changes from P. y1 Rise to P y2 Afterwards, the change in the volume of the liquid cavity, ΔV y :

[0027]

[0028] The stored energy is calculated using the formula for the energy of a gas as a work quantity:

[0029]

[0030] Substituting equation (11) into the equation and simplifying, we can obtain the expression for energy density μ2.

[0031]

[0032] The pressure P of the liquid chamber in the initial state y1 The pressure P at the end state y2 Initial volume V of the air chamber q1 When all are the same, comparing equation (3) and equation (12), since It can be seen that the volume change of the liquid chamber of the accumulator of the present invention is larger than that of the traditional accumulator, and the volume of oil stored is larger.

[0033] Furthermore, the increase in energy density of the high-energy-density hollow piston rod hydraulic accumulator is related to the cross-sectional areas A1 and A2 of the piston: the smaller A1 is, that is, the closer A1 is to A2, the greater the energy density; if the maximum pressure of the air chamber is P qmax The maximum pressure in the liquid chamber is P.ymax From equation (8), the relationship between the effective working area A1 of the upper chamber air cavity and the effective working area A2 of the lower chamber piston can be obtained as follows:

[0034]

[0035] As can be seen from equation (15), the smaller A1 is, the greater the energy density of the accumulator and the greater the maximum pressure P in the liquid chamber. ymax It is determined by the actual working conditions. To reduce A1, the maximum pressure P in the air chamber needs to be increased. qmax However, the maximum air pressure of the accumulator is limited, thus restricting the maximum value of A1. This is when the maximum pressure P of the oil to be stored... ymax The maximum pressure P in the air chamber qmax When the energy density approaches the target value, A1 becomes very large, meaning the energy density cannot be increased. Therefore, the ratio of A1 to A2 should be selected appropriately based on the actual operating conditions.

[0036] Beneficial effects:

[0037] 1. The present invention has a higher energy storage density than traditional energy storage devices when storing energy, that is, the present invention can store more energy when compressing the same volume of gas.

[0038] 2. The piston rod is a hollow structure, and small holes are opened on the side wall of the hollow piston rod to connect the gas inside the piston rod with the gas in the gas cylinder. This can reduce the weight of the accumulator, reduce the cost of the accumulator, increase the initial volume of the gas chamber, and further improve the energy storage density of the accumulator.

[0039] Instruction manual illustrations

[0040] Figure 1 This is a schematic diagram of the high energy density hollow piston rod hydraulic accumulator of the present invention.

[0041] In the diagram: 1. Liquid chamber oil inlet; 2. Liquid chamber end cap; 3. Liquid chamber; 4. Piston; 5. Hollow piston rod; 6. Cylinder; 7. Cylinder; 8. Gas chamber end cap; 9. Gas chamber air port; 10. Gas cylinder. Detailed Implementation

[0042] like Figure 1 As shown, this invention provides a high energy density hollow piston rod hydraulic accumulator, which consists of 2, a liquid chamber end cap; 4, a piston; 5, a hollow piston rod; 6, a cylinder; 8, an air chamber end cap; and 10, an air cylinder; A0 is the cross-sectional area of ​​the piston rod; A1 is the effective working area of ​​the upper air chamber; A2 is the effective working area of ​​the lower piston, and A2 > A1.

[0043] The accumulator is connected as follows: the liquid chamber end cap 2 and the bottom of the liquid chamber cylinder 6 are sealed together; the piston 4 is installed inside the cylinder 7; the piston 4 has a sealing ring; and the liquid chamber end cap 2, the cylinder 6, and the piston 4 form a liquid chamber 3. The gas chamber end cap 8 is connected to the cylinder 6; the hollow piston rod 5 and the piston 4 are coaxially connected; and a sealing ring is installed between the inner wall of the hollow piston rod 5 and the gas chamber end cap 8; and the liquid chamber end cap 8, the cylinder 6, the piston 4, and the inner cavity of the piston rod form a gas chamber 7.

[0044] The liquid chamber end cap 2 is provided with a liquid chamber oil inlet 1, and the lower inner wall of the hollow piston rod 5 has an air hole, which connects the gas in the hollow piston rod with the gas cylinder. The cylinder wall of the cylinder barrel 6 is provided with a gas chamber air port 9, and the gas cylinder 10 is connected to the gas chamber 7 through the gas chamber air port 9 by a high-pressure pipe.

[0045] High-energy-density hollow piston rod hydraulic accumulator energy storage principle

[0046] The energy storage principle of the high-energy-density hollow piston rod hydraulic accumulator of this invention is the same as that of a conventional piston accumulator, both relying on the compression and expansion of the gas chamber volume to achieve the filling and discharging functions. During energy storage, high-pressure oil enters the liquid chamber 3 through the oil inlet 1, pushing the piston 4 upwards and compressing the gas in the gas chamber 7, converting hydraulic energy into the internal energy of the gas in the gas chamber 7 and the gas cylinder 10. The difference lies in the fact that in a conventional accumulator, the contact area between the liquid and gas on the piston is the same, while in the accumulator with a piston rod of this invention, the contact area between the gas and the piston is larger than the contact area between the liquid and the piston.

[0047] The hollow piston rod of the accumulator of this invention has the following two advantages: 1. It reduces the weight of the accumulator and reduces costs. 2. The gas volume inside the piston rod can be used as part of the gas volume, increasing the initial volume of the gas chamber.

[0048] The effective area of ​​hydraulic oil pressure acting on the piston is A2, and the effective area of ​​gas acting on the piston is the same as A1. Since there is a piston rod in the gas chamber, A1 < A2.

[0049] According to the second interpretation of high energy storage density of accumulators: for accumulators with the same initial gas volume and initial pressure, the pressure change in the liquid chamber is the same; if the volume of stored oil is large, the energy storage density of the accumulator is high. The high energy storage density of the present invention will now be explained.

[0050] Traditional accumulators rely on changes in the volume and pressure of their filling chamber to achieve filling and discharging functions. According to the gas law, if the liquid chamber pressure changes from P... y1 Rise to P y2 Then the air chamber pressure also changes from P q1 Rise to P q2 It satisfies the following relationship:

[0051] P q1 Vq1 n =P q2 V q2 n (1)

[0052] In the formula: P q1 P represents the initial pressure of the air chamber. q2 V represents the pressure in the gas chamber at the final state; n is the polytropic exponent, n = 1.4 for an adiabatic process, V q1 V is the initial volume of the air chamber; q2 The final volume of the air chamber; ΔV q This represents the change in air cavity volume.

[0053] available

[0054]

[0055] Simplification yields the change in the liquid chamber volume of a traditional accumulator, ΔV. q :

[0056]

[0057] The stored energy is essentially the work done by the liquid on the piston, which is converted into the internal energy of the gas. The stored energy is calculated by the following formula:

[0058]

[0059] Substituting equation (2) into the equation and simplifying, we can obtain the expression for the energy density μ1.

[0060]

[0061] In order to compare with conventional accumulators, the pressure P of the accumulator liquid chamber in the initial state of the present invention is... y1 The pressure P at the end state y2 Initial volume V of the air chamber q1 It is equivalent to traditional energy storage devices.

[0062] Initial force analysis of the piston rod:

[0063] P y1 A2 = P q1 A1 (6)

[0064] Force analysis of the piston rod in the final state:

[0065] P y2 A2 = P q2 A1 (7)

[0066] By combining equation (6-7), the relationship between the air chamber pressure and the liquid chamber pressure can be obtained:

[0067]

[0068] The relationship between the change in air chamber volume ΔV and the change in liquid chamber volume ΔV2:

[0069]

[0070] According to the gas law, if the pressure in the gas chamber is P q1 Rise to P q2 The following relationship must be satisfied:

[0071] P q1 V q1 n =P q2 V q2 n (10)

[0072] In the formula: P y1 P represents the initial high-pressure oil pressure in the lower chamber; y2 The pressure of the lower chamber high-pressure oil in the final state; P q1 P represents the initial pressure of the air chamber. q2 V represents the pressure in the air chamber at the final state; A1 is the effective working area of ​​the upper air chamber; A2 is the effective working area of ​​the lower piston, A2 > A1; q1 V is the initial volume of the air chamber; q2 The final volume of the air chamber is ΔV. y ΔV represents the change in the liquid chamber volume of the accumulator of this invention. q This represents the change in air cavity volume.

[0073] Substituting equation (8) into equation (10) yields...

[0074]

[0075] Substituting equation (11) into equation (9), we can obtain the result when the liquid chamber pressure changes from P. y1 Rise to P y2 Afterwards, the change in the volume of the liquid cavity, ΔV y :

[0076]

[0077] The stored energy is calculated using the formula for the energy of a gas as a work quantity:

[0078]

[0079] Substituting equation (11) into the equation and simplifying, we can obtain the expression for energy density μ2.

[0080]

[0081] The pressure P of the liquid chamber in the initial state y1 The pressure P at the end statey2 Initial volume V of the air chamber q1 When all are the same, comparing equation (3) and equation (12), since It can be seen that the volume change of the accumulator's liquid chamber is greater than that of a conventional accumulator, resulting in a larger volume of stored oil. By definition, the accumulator of this invention has a higher energy storage density than conventional accumulators.

[0082] Comparing the energy density expression μ1 of a conventional energy storage device with the energy density expression μ2 of this invention, it can be seen that the energy density of the energy storage device of this invention is higher than that of a conventional energy storage device. Times. Due to Therefore, the energy density μ2 of this invention is greater than the energy density μ1 of a conventional accumulator.

[0083] The increase in energy density is related to the cross-sectional areas A1 and A2 of the two pistons. The smaller A1 is, that is, the closer A1 is to A2, the greater the energy density. If the maximum pressure in the gas chamber is P... qmax The maximum pressure in the liquid chamber is P. ymax From equation (8), we can obtain:

[0084]

[0085] As can be seen from equation (15), the smaller A1 is, the greater the energy density of the accumulator and the greater the maximum pressure P in the liquid chamber. ymax It is determined by the actual working conditions. To reduce A1, the maximum pressure P in the air chamber needs to be increased. qmax However, the maximum air pressure of the accumulator is limited, thus restricting the maximum value of A1. This is when the maximum pressure P of the oil to be stored... ymax The maximum pressure P in the air chamber qmax When the energy density approaches the given value, A1 becomes very large, meaning the energy density cannot be increased. Therefore, the appropriate ratio of A1 to A2 should be chosen based on actual operating conditions, with A0 + A1 approaching A2.

[0086] Example 1

[0087] The following examples demonstrate that the energy storage density of this accumulator is greater than that of conventional accumulators.

[0088] Under energy storage conditions, if the pressure in the accumulator's liquid chamber rises from 7 MPa to 11 MPa, the initial volume of both the accumulator of this invention and the conventional accumulator is 100 L.

[0089] Therefore, the volume of liquid stored in a traditional accumulator, ΔV, can be calculated according to equation (3). y

[0090]

[0091] If the cross-sectional area of ​​the upper chamber piston in this invention is half the area of ​​the lower chamber piston, that is... Therefore, the liquid volume ΔV2 stored in the accumulator of the present invention can be calculated according to equation (12).

[0092]

[0093] It can be seen that, under the same gas volume and initial pressure, the accumulator of the present invention stores 27.60L more oil than the conventional accumulator.

[0094] Next, compare energy storage density:

[0095] The energy density of a conventional accumulator is calculated according to equation (5):

[0096]

[0097] The energy density of the energy storage device of the present invention is calculated according to equation (14):

[0098]

[0099] It is evident that the energy density has increased by 2 times.

Claims

1. A high-energy-density hollow piston rod hydraulic accumulator, characterized in that: Includes a cylindrical cylinder (6) and a gas cylinder (10). The bottom of the cylinder (6) is provided with a liquid chamber end cap (2) to seal the bottom end of the cylinder (6), and the top of the cylinder (6) is provided with a gas chamber end cap (8) to seal the top end of the cylinder (6). A piston (4) is provided in the middle of the cylinder (6), and a hollow piston rod (5) is provided on the piston (4) that penetrates the gas chamber end cap (8). The rodless chamber in the cylinder (6) separated by the piston (4) is a liquid chamber (3) filled with hydraulic oil. The cavity is a gas cavity (7). The gas cavity (7) has a gas cavity port (9) on the side wall of the cylinder (6) near the gas cavity end cap (8). The gas cavity port (9) is connected to the gas cylinder (10) through a high-pressure pipe. The liquid cavity end cap (2) has a liquid cavity oil inlet (1) that communicates with the liquid cavity (3). The hollow piston rod (5) is completely sealed. Only on the side wall near the piston (4) is there a through hole that communicates with the inner cavity of the hollow piston rod (5), so that the space inside the hollow piston rod (5) is part of the gas volume of the gas cavity (7).

2. The high energy density hollow piston rod hydraulic accumulator according to claim 1, characterized in that: A sealing ring is provided between the piston (4) and the inner wall of the cylinder (6), and a sealing ring is installed between the inner wall of the hollow piston rod (5) and the end cap (8) of the air chamber.

3. The high energy density hollow piston rod hydraulic accumulator according to claim 1, characterized in that: The hollow piston rod (5) and the piston (4) are connected by a spherical hinge, thereby reducing the precision requirements of the machining.

4. A method for operating the high energy density hollow piston rod hydraulic accumulator as described in claim 1, characterized in that... The steps are as follows: The high energy density hollow piston rod hydraulic accumulator relies on the compression and expansion of the gas volume in the gas chamber (7) to realize the filling and drainage of the liquid chamber (3) from the oil inlet (1); when storing energy, the piston (4) is initially located at the bottom of the cylinder (6), that is, the liquid chamber space is 0. High pressure oil enters the liquid chamber (3) through the oil inlet (1), and the high pressure oil pushes the piston (4) to move towards the gas chamber (7), compressing the gas in the gas chamber (7) and converting the hydraulic energy into the internal energy of the gas in the gas chamber (7) and the gas cylinder (10); The area of ​​gas acting on piston (4) is smaller than the area of ​​liquid acting on piston (4); The volume inside the hollow piston rod (5) communicates with the air chamber (7), thereby increasing the energy storage capacity of the accumulator. With the same air chamber volume, compared to a traditional piston accumulator, this increases the energy storage density of the accumulator. When the energy storage reaches its maximum, the air chamber pressure is equal to the liquid chamber pressure. times.

5. The working method according to claim 4, characterized in that: In the initial state of energy storage, the piston (4) is at the bottom of the cylinder (6). Ignoring the compression of the oil, internal and external leakage, and friction, when the piston (4) rises at a constant speed, the force exerted by the liquid chamber (3) on the hollow piston rod (5) is: （6）, Because the air chamber (7) has a hollow piston rod (5) occupying part of its area, the force-bearing area of ​​the air chamber (7) on the piston (4) is smaller than the force-bearing area of ​​the liquid chamber (3). ; In the final state, the pressure in the liquid chamber gradually increases to its maximum value and balances with the pressure in the gas chamber. During this process, the piston moves to the equilibrium position, and the force exerted by the liquid chamber (3) on the hollow piston rod (5) is: （7）, Combining equation (6-7) yields the air chamber pressure. and fluid chamber pressure The relationship between them: （8）, The relationship between the change in air chamber volume ΔV and the change in liquid chamber volume ΔV2: （9）, According to the gas law, if the pressure in the gas chamber is... Rise to The following relationship must be satisfied: （10）, In the formula: This represents the initial high-pressure oil pressure in the lower chamber. The pressure of the lower chamber high-pressure oil in the final state; This represents the initial pressure of the air chamber. The pressure in the air chamber at the final state; The effective working area of ​​the upper air cavity; The effective working area of ​​the lower chamber piston. ; This represents the initial volume of the air chamber. This refers to the final volume of the air chamber. This refers to the change in the liquid chamber volume of the accumulator in this invention. This represents the change in air cavity volume; Substituting equation (8) into equation (10) yields... （11）, Substituting equation (11) into equation (9), we can obtain the result when the liquid chamber pressure changes from... Rise to Afterwards, the change in the volume of the liquid cavity : （12）, The stored energy is calculated using the formula for the energy of a gas as a work quantity: （13）, Substituting equation (11) into the equation and simplifying, we can obtain the energy density. expression （14）, Pressure of the liquid chamber in its initial state Pressure at the end state Initial volume of air chamber When all are the same, comparing equation (3) and equation (12), since It can be seen that the volume change of the liquid chamber (3) of the accumulator of the present invention is larger than that of the traditional accumulator, and the volume of oil stored is larger.

6. The high energy density hollow piston rod hydraulic accumulator according to claim 5, characterized in that: The increase in energy density of the high-energy-density hollow piston rod hydraulic accumulator is related to the cross-sectional area of ​​the piston (4). and related: The smaller, that is The closer to The higher the energy density, the greater the maximum pressure in the air chamber. The maximum pressure in the liquid chamber is The effective working area of ​​the upper air cavity can be obtained from equation (8). Effective working area with the lower chamber piston The relationship between them can be obtained as follows: （15）, From equation (15), we can see that The smaller the accumulator, the higher its energy density and the greater the maximum pressure in the liquid chamber. It is determined by the actual working conditions; if you want to reduce... This requires increasing the maximum pressure in the air chamber. However, the maximum air pressure of the accumulator is limited, which restricts its operation. The maximum value when the maximum pressure of the oil to be stored is... The maximum pressure of the air chamber When approaching, at this time The energy density cannot be increased significantly; therefore, a reasonable selection should be made based on the actual operating conditions. and The ratio of .

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