CN110486337A - Multiple cavity oil cylinder closed type hydraulic system and engineering machinery - Google Patents

Abstract

The invention discloses a multi-chamber oil cylinder closed hydraulic system and construction machinery. The multi-chamber oil cylinder closed hydraulic system includes a hydraulic cylinder and a closed pump, the hydraulic cylinder is a multi-chamber oil cylinder, and the multi-chamber oil cylinder includes a hydraulic cylinder body, an oil inlet connected to the closed pump and an oil outlet connected to the closed pump, the hydraulic cylinder body includes a rodless chamber and a rod chamber, and the oil inlet connected to the The area of the cross-section of the rodless chamber is equal to the area of the cross-section of the rod chamber connected to the oil outlet; the closed hydraulic system and engineering machinery can use a closed pump to control the flow of hydraulic oil when in use Direction, there are no control elements such as multi-way valves. When the boom of construction machinery moves upward, there is no pressure loss caused by multi-way valves; when the boom of construction machinery moves downward, the flow direction of hydraulic oil changes, and the closed pump Converting it into a motor means converting the gravitational potential energy during the lowering of the boom into the mechanical energy of the closed pump to recycle the gravitational potential energy.

Description

Multi-cavity oil cylinder closed hydraulic system and engineering machinery

technical field

The invention relates to the technical field of hydraulic boom energy saving, in particular to a multi-cavity oil cylinder closed hydraulic system and engineering machinery.

Background technique

The lifting and lowering of booms of excavators and grabbers during work is controlled by boom cylinders. Figure 1 is a schematic structural diagram of the existing excavator and grabber arm hydraulic circuits. Please refer to Figure 1. Excavators and grabbers are currently The hydraulic circuit of the arm of the grabber generally includes a hydraulic pump 1', a multi-way valve 2', a hydraulic cylinder 3' and a holding valve 4'. When the boom is raised, the hydraulic oil is pressurized by the hydraulic pump 1' and then passes through the multi-way valve 2. 'Control to drive the hydraulic cylinder 3' to move and realize the rise of the hydraulic cylinder 3'; when the boom is lowered, throttling through the multi-way valve 2' establishes resistance to keep the boom lowered smoothly.

Existing excavator and grabber arm hydraulic circuits have pressure loss at the multi-way valve when the boom is raised, resulting in energy loss. When the boom is lowered, the multi-way valve throttling creates resistance to keep the boom down smoothly. During the descent, the gravitational potential energy is completely converted into heat, resulting in a waste of energy.

Contents of the invention

The purpose of the present invention is to provide a multi-cavity oil cylinder closed hydraulic system, no pressure loss occurs during the upward movement of the closed pump driving the hydraulic cylinder piston cylinder, and when the hydraulic cylinder piston rod moves downward, the closed pump turns into a motor The working condition recovers the gravitational potential energy.

Another object of the present invention is to provide a construction machine that does not generate pressure loss when the closed pump drives the boom to rise, and when the boom is lowered, the closed pump turns into a motor working mode to recover the gravitational potential energy.

The present invention is achieved through the following technical solutions:

The first aspect of the present invention provides a multi-chamber closed hydraulic system, including a hydraulic cylinder and a closed pump, the hydraulic cylinder is a multi-chamber oil cylinder, the multi-chamber oil cylinder includes a hydraulic cylinder body, and the closed pump The connected oil inlet and the oil outlet connected with the closed pump, the hydraulic cylinder body includes a rodless chamber and a rod chamber, and the cross-sectional area of the rodless chamber connected with the oil inlet is equal to the area of the cross-section of the rod chamber connected to the oil outlet.

As mentioned above in the multi-cavity cylinder closed hydraulic system, the hydraulic cylinder body includes a first cylinder body, a second cylinder body located inside the first cylinder body, and a piston sleeve assembly;

The piston sleeve assembly includes a cylindrical first piston rod containing an inner cavity, a first piston connected to the first piston rod, a second piston rod connected to the inner cavity of the first piston rod and a second piston connected to the second piston rod, and the first piston rod is nested between the inner wall of the first cylinder and the outer wall of the second cylinder, and the second piston rod is set inside the second cylinder;

The rodless chamber includes a first rodless chamber and a second rodless chamber; the rod chamber includes a first rod chamber and a second rod chamber, and the first piston is used to push the inner wall of the first cylinder The inner chamber between the outer wall of the second cylinder body is divided into the first rodless chamber and the first rod chamber, and the second piston is used to divide the inner chamber of the second cylinder body into the first rodless chamber. the second rodless cavity and the second rod cavity;

The oil inlet connected to the closed pump is arranged on any one of the first rodless chamber and the second rodless chamber, and the first rodless chamber and the second rodless chamber There are oil outlets connected to the closed pump on the cavity;

The area of the cross-section of the rodless cavity provided with the oil inlet is equal to the sum of the cross-sectional areas of the first rod cavity and the second rod cavity.

As mentioned above, the multi-chamber closed hydraulic system further includes an accumulator, and an oil port connected to the accumulator is provided on the above-mentioned rodless chamber where the oil inlet is not installed.

As mentioned above in the multi-chamber cylinder closed hydraulic system, the accumulator is used to recover the hydraulic oil in the rodless chamber provided with the oil port when the piston sleeve assembly is lowered, and the accumulator is also used to When the assembly rises, the hydraulic oil is released to provide auxiliary power for the piston sleeve assembly.

As described above in the multi-chamber closed hydraulic system, the second cylinder is arranged coaxially with the first cylinder, and the cross-section of the first rodless chamber is circular, and the second rodless The cavity is circular in cross section.

As mentioned above in the multi-cavity cylinder closed hydraulic system, the first piston rod is a cylindrical piston rod with a built-in cavity, and the second piston rod is a cylindrical piston rod.

As mentioned above, the multi-cavity cylinder closed hydraulic system further includes a holding valve, and the holding valve is arranged between the closed pump and the rodless chamber provided with the oil inlet.

As mentioned above in the multi-cavity cylinder closed hydraulic system, the closed pump is connected with the engine, and the closed pump is used to drive the engine to rotate when the piston sleeve assembly is lowered.

A second aspect of the present invention provides a construction machine, comprising the multi-cavity oil cylinder closed hydraulic system and a boom connected to the hydraulic cylinder.

As described above for the construction machine, the number of the hydraulic cylinders is an even number, and the hydraulic cylinders are arranged in parallel on the lower side of the boom.

The technical solution provided by the application can achieve the following beneficial effects:

The multi-chamber oil cylinder closed hydraulic system of the present invention mainly involves a hydraulic cylinder and a closed pump; the hydraulic cylinder is a multi-chamber oil cylinder, and the multi-chamber oil cylinder includes a hydraulic cylinder body, an oil inlet connected to the closed pump and a closed pump. The oil outlet connected to the pump, the hydraulic cylinder body includes a rodless cavity and a rod cavity; at the same time, the multi-cavity cylinder closed hydraulic system (hydraulic system for short) also requires the cross-sectional area of the rodless cavity connected to the oil inlet It is equal to the area of the cross-section of the rod cavity connected to the oil outlet, so as to realize the same oil inlet and outlet of the hydraulic cylinder body (that is, to realize a closed hydraulic system); when the hydraulic system is working, the closed pump and the hydraulic pressure The cylinder forms a closed hydraulic system. The closed hydraulic system can use a closed pump to control the flow direction of the hydraulic oil. There are no control elements such as multi-way valves. The specific situation is that when the piston of the hydraulic cylinder moves upward, the hydraulic oil does not There is no pressure loss through the multi-way valve; when the piston of the hydraulic cylinder moves downward, the flow direction of the hydraulic oil changes (the flow direction of the hydraulic oil is opposite to the flow direction of the hydraulic oil when the piston of the hydraulic cylinder moves upward), and the closed pump is converted into Motor, so that the gravitational potential energy in the falling of the piston of the hydraulic cylinder can be converted into the mechanical energy of the closed pump, so as to realize the recycling of the gravitational potential energy.

The engineering machinery of the present invention includes the above-mentioned multi-chamber oil cylinder closed hydraulic system, the boom of the engineering machine is connected with the multi-chamber oil cylinder, and the horizontal rodless chamber of the multi-chamber oil cylinder closed hydraulic system (hydraulic system for short) is connected with the oil inlet. The area of the section is equal to the area of the cross section of the rod cavity connected to the oil outlet, so that the oil inlet and outlet of the hydraulic cylinder body are the same (that is, the closed hydraulic system is realized). When the hydraulic system is working, the closed The pump and the hydraulic cylinder form a closed hydraulic system. The closed hydraulic system can use the closed pump to control the movement direction of the hydraulic oil. There are no control elements such as multi-way valves. The specific situation is that when the boom moves upward, the hydraulic oil There is no pressure loss without passing through the multi-way valve; when the boom moves downward, the flow direction of the hydraulic oil changes (the flow direction of the hydraulic oil is opposite to the flow direction of the hydraulic oil when the piston of the hydraulic cylinder moves upward), and the closed pump is converted into a motor at this time , so that the gravitational potential energy in the falling of the piston of the hydraulic cylinder can be converted into the mechanical energy of the closed pump, so as to realize the recycling of the gravitational potential energy.

Description of drawings

In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the following will briefly introduce the accompanying drawings that need to be used in the specific implementation or description of the prior art. Obviously, the accompanying drawings in the following description The drawings show some implementations of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative work.

Fig. 1 is the structural schematic diagram of hydraulic circuit of existing excavator and material grabbing machine arm;

Fig. 2 is a schematic structural diagram of a multi-cavity oil cylinder closed hydraulic system provided by an embodiment of the present invention;

Fig. 3 is a schematic structural diagram of a hydraulic cylinder in a multi-cavity cylinder closed hydraulic system provided by an embodiment of the present invention.

Explanation of reference signs:

1 - closed pump;

2 - hydraulic cylinder;

3 - accumulator;

4 - holding valve;

21 - the first cylinder;

22 - the second cylinder;

23 - the first piston rod;

24 - the second piston rod;

25 - the first rodless chamber;

26 - the second rodless chamber;

27 - the first rod cavity;

28 - second rod cavity.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

In the description of the present invention, it should be understood that the terms "comprising" and "having" and any variations thereof are intended to cover a non-exclusive inclusion, for example, a process comprising a series of steps or units, A method, system, product or device is not necessarily limited to those steps or elements explicitly listed, but may include other steps or elements not explicitly listed or inherent to the process, method, product or device. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features.

The multi-cavity oil cylinder closed hydraulic system and engineering machinery provided by the present invention will be described in detail below in conjunction with specific embodiments.

Embodiment one:

Figure 2 is a schematic structural diagram of a multi-cavity oil cylinder closed hydraulic system provided by an embodiment of the present invention, and Figure 3 is a structural schematic diagram of a hydraulic cylinder in a multi-cavity oil cylinder closed hydraulic system provided by an embodiment of the present invention, please refer to Figures 2 and 3, This embodiment provides a multi-cavity oil cylinder closed hydraulic system, including a closed pump 1 and a hydraulic cylinder 2;

The hydraulic cylinder 2 is a multi-chamber oil cylinder, and the multi-chamber oil cylinder includes a hydraulic cylinder body, an oil inlet connected to the closed pump and an oil outlet connected to the closed pump, and the hydraulic cylinder body includes A rodless cavity and a rod cavity, the area of the cross section of the rodless cavity connected to the oil inlet is equal to the area of the cross section of the rod cavity connected to the oil outlet.

In the multi-cavity cylinder hydraulic system, the cross-sectional area of the rodless chamber connected to the oil inlet is equal to the cross-sectional area of the rod chamber connected to the oil outlet, so that the oil inlet and outlet of the hydraulic cylinder body are the same, When working, the closed pump and the hydraulic cylinder form a closed hydraulic system. The closed hydraulic system can use the closed pump to control the movement direction of the hydraulic oil. There are no control elements such as multi-way valves. When the piston of the hydraulic cylinder moves upward , the hydraulic oil does not produce pressure loss without passing through the multi-way valve; when the piston of the hydraulic cylinder moves downward, the flow direction of the hydraulic oil changes, and the closed pump is converted into a motor at this time, so that the gravitational potential energy of the piston of the hydraulic cylinder can be reduced Converted into the mechanical energy of the closed pump to realize the recycling of gravitational potential energy.

Specifically, in this embodiment, the hydraulic cylinder body includes a first cylinder body 21, a second cylinder body 22 located inside the first cylinder body, and a piston sleeve assembly;

The piston sleeve assembly includes a cylindrical first piston rod 23 containing an inner cavity, a first piston connected to the first piston rod 23, a second piston rod 24 connected to the inner chamber of the first piston rod 23 and The second piston connected with the second piston rod 24, and the first piston rod 23 is nested between the inner wall of the first cylinder 21 and the outer wall of the second cylinder 22, the second piston rod 24 is set inside the second cylinder 22;

The rodless cavity comprises a first rodless cavity 25 and a second rodless cavity 26; the rod cavity comprises a first rod cavity 27 and a second rod cavity 28, and the first piston is used to connect the inner wall of the first cylinder body 21 to the The cavity between the outer walls of the second cylinder body 22 is divided into a first rodless cavity 25 and a first rod cavity 27, and the second piston is used to divide the cavity of the second cylinder body 22 into a second rodless cavity 26 and a second rod chamber 28;

The oil inlet connected to the closed pump is set on any one of the first rodless cavity and the second rodless cavity, and the first rod cavity 27 is connected to the second rodless cavity. The rod cavity 28 is provided with an oil outlet connected to the closed pump 1 . In this embodiment, the oil inlet is opened on the first rodless cavity 25, and the cross-sectional area of the first rodless cavity 25 is equal to the first rod cavity 27 and the second rod cavity. the sum of the areas of the cross-sections of the rod cavity 28;

In other embodiments, the oil inlet can also be opened on the second rodless chamber 26, and at this time, the cross-sectional area of the second rodless chamber 26 is equal to that of the first rod chamber 27 and The sum of the areas of the cross-sections of the second rod cavity 28 is realized.

In this embodiment, by setting the area of the cross-section of the first rodless chamber 25 equal to the sum of the areas of the cross-sections of the first rod chamber 27 and the second rod chamber 28, the oil inlet and outlet of the hydraulic cylinder are the same, In this way, a closed hydraulic system is realized. When the piston of the hydraulic cylinder moves upward, the hydraulic oil does not pass through the multi-way valve without pressure loss; when the piston of the hydraulic cylinder moves downward, the flow direction of the hydraulic oil changes, and the closed pump is converted into As a motor, the gravitational potential energy in the falling of the piston of the hydraulic cylinder can be converted into the mechanical energy of the closed pump, so as to realize the recovery and utilization of the gravitational potential energy.

Further, in this embodiment, the second cylinder body 22 is arranged coaxially with the first cylinder body 21 (that is, the above-mentioned first cylinder body 21 and the second cylinder body 22 should have a coaxial central axis, and in a specific embodiment Among them, the first cylinder 21 and the second cylinder 22 are preferably cylindrical cylinders), the cross section of the first rodless cavity 25 is circular, and the cross section of the second rodless cavity 26 is circular Shape, adopt the cylinder body of above-mentioned structural design, its manufacturing method is simple and convenient.

Further, in this embodiment, the closed pump 1 is connected to the engine, and the closed pump 1 is used to drive the engine to rotate when the hydraulic cylinder piston sleeve assembly is lowered. By connecting the closed pump 1 with the engine, the mechanical energy when the hydraulic cylinder piston sleeve assembly descends is recovered and utilized.

Further, the multi-chamber cylinder closed hydraulic system of this embodiment also includes an accumulator 3, and the oil inlet connected to the closed pump is arranged in the above-mentioned first rodless chamber 25 and the second rodless chamber 26 An oil port connected to the accumulator is opened on any one of the rodless chambers, and the rodless chamber not equipped with the oil inlet. That is, when the oil inlet is arranged in the above-mentioned first rodless chamber 25, the cross-sectional area of the first rodless chamber 25 is equal to the difference between the cross-sectional areas of the first rod chamber 27 and the second rod chamber 28. At this time, the second rodless chamber 26 is provided with an oil port connected to the accumulator 3; that is, the oil inlet is arranged in the second rodless chamber 26, and the second rodless chamber 26 When the cross-sectional area of the first rod chamber 27 and the second rod chamber 28 are equal to the sum of the cross-sectional areas of the first rod chamber 27 and the second rod chamber 28, the first rodless chamber 25 is provided with the accumulator 3 Connected oil port.

The accumulator 3 is used to recover the hydraulic oil in the second rodless chamber 26 or the first rodless chamber 25 to store a part of the hydraulic energy when the piston sleeve assembly of the hydraulic cylinder descends. It is also used to release the above-mentioned hydraulic energy to provide auxiliary power for the upward movement of the piston rod assembly of the hydraulic cylinder when the piston sleeve assembly of the hydraulic cylinder rises. In this embodiment, by setting an accumulator, the second rodless chamber 26 of the hydraulic cylinder 2 and the accumulator 3 form an energy recovery device. Auxiliary power further reduces energy consumption.

Further, the multi-cavity cylinder closed hydraulic system of this embodiment also includes a holding valve 4, and the holding valve 4 is arranged between the closed pump 1 and the rodless chamber provided with the oil inlet; specifically There are two specific embodiments, that is, when the oil inlet is arranged on the first rodless cavity, and the cross-sectional area of the first rodless cavity 25 is equal to the first rod cavity 27 and the second rod cavity When the sum of the cross-sectional areas of the rod chamber 28, the holding valve 4 is specifically installed on the oil circuit between the closed pump 1 and the first rodless chamber 25; in other embodiments, that is When the oil inlet is arranged on the second rodless cavity 26, and the area of the cross section of the second rodless cavity 26 is equal to the area of the cross section of the first rod cavity 27 and the second rod cavity 28 Sometimes, the holding valve is specifically installed on the oil circuit between the closed pump 1 and the second rodless chamber 26 . In this embodiment, the maintenance valve 4 is set to maintain the pressure of the hydraulic cylinder, so as to prevent the danger of the piston sleeve assembly from falling down in the closed hydraulic system of the cavity and cylinder in use.

In the multi-cavity oil cylinder closed hydraulic system of the present invention, the area of the cross-section of the rodless chamber connected to the hydraulic cylinder with the oil inlet is equal to the sum of the cross-sectional areas of the first rod chamber and the second rod chamber. When the system is working, the closed pump and the hydraulic cylinder form a closed hydraulic system. When the piston of the hydraulic cylinder moves upward, the hydraulic oil does not pass through the multi-way valve without pressure loss; when the piston of the hydraulic cylinder moves downward, the hydraulic oil The flow direction of the hydraulic cylinder changes (the flow direction of the hydraulic oil is opposite to the flow direction of the hydraulic oil when the piston of the hydraulic cylinder moves upward), and the closed pump is converted into a motor at this time, so that the gravitational potential energy in the falling of the piston of the hydraulic cylinder can be converted into the mechanical energy of the closed pump , to realize the recycling of gravitational potential energy.

Embodiment two:

This embodiment provides a construction machine, which includes the multi-cavity oil cylinder closed hydraulic system described in the first embodiment and a boom connected to the hydraulic cylinder.

For example, a multi-cavity cylinder closed hydraulic system, including hydraulic cylinders and closed pumps;

The hydraulic cylinder includes a hydraulic cylinder body, an oil inlet connected to the closed pump, and an oil outlet connected to the closed pump. The hydraulic cylinder body includes a rodless chamber and a rod chamber, which are connected to the closed pump. The area of the cross-section of the rodless chamber connected to the oil inlet is equal to the area of the cross-section of the rod chamber connected to the oil outlet.

In this embodiment, the hydraulic cylinder body includes a first cylinder body, a second cylinder body located inside the first cylinder body, and a piston sleeve assembly;

The piston sleeve assembly includes a cylindrical first piston rod containing an inner cavity, a first piston connected to the first piston rod, a second piston rod connected to the inner cavity of the first piston rod and a second piston connected to the second piston rod, and the first piston rod is nested between the inner wall of the first cylinder and the outer wall of the second cylinder, and the second piston rod is set inside the second cylinder;

The rodless chamber includes a first rodless chamber and a second rodless chamber; the rod chamber includes a first rod chamber and a second rod chamber, and the first piston is used to push the inner wall of the first cylinder The inner chamber between the outer wall of the second cylinder body is divided into the first rodless chamber and the first rod chamber, and the second piston is used to divide the inner chamber of the second cylinder body into the first rodless chamber. the second rodless cavity and the second rod cavity;

The first rodless chamber is provided with the oil inlet connected to the closed pump, and the cross-sectional area of the first rodless chamber is equal to that of the first rod chamber and the second rod chamber. The sum of the areas of the cross-sections of the rod cavity.

Both the first rod chamber and the second rod chamber are provided with an oil outlet connected to the closed pump.

In this embodiment, there are two hydraulic cylinders, and the hydraulic cylinders are arranged in parallel on the lower side of the boom. In this embodiment, the first piston rod of the hydraulic cylinder is connected to the boom.

The construction machine in this embodiment may be an excavator or a material grabber.

The construction machinery of this embodiment includes the above-mentioned multi-chamber closed hydraulic system, the boom of the construction machine is connected to the multi-chamber hydraulic cylinder, and the multi-chamber closed hydraulic system (hydraulic system for short) is connected to the oil inlet. The area of the cross-section is equal to the area of the cross-section of the rod chamber connected to the oil outlet, so that the oil inlet and outlet of the hydraulic cylinder body are the same (that is, the closed hydraulic system is realized). When the hydraulic system is working, the closed The hydraulic pump and the hydraulic cylinder form a closed hydraulic system. The closed hydraulic system can use the closed pump to control the movement direction of the hydraulic oil. There are no control elements such as multi-way valves. The specific situation is that when the boom moves upward, the hydraulic pressure The oil does not pass through the multi-way valve without pressure loss; when the boom moves downward, the flow direction of the hydraulic oil changes (the flow direction of the hydraulic oil is opposite to the flow direction of the hydraulic oil when the piston of the hydraulic cylinder moves upward), and the closed pump is converted into Motor, so that the gravitational potential energy in the falling of the piston of the hydraulic cylinder can be converted into the mechanical energy of the closed pump, so as to realize the recycling of the gravitational potential energy.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. scope.

Claims (10)

1. A multi-cavity oil cylinder closed hydraulic system, characterized in that: Including hydraulic cylinder and closed pump; The hydraulic cylinder is a multi-chamber oil cylinder, and the multi-chamber oil cylinder includes a hydraulic cylinder body, an oil inlet connected to the closed pump and an oil outlet connected to the closed pump, and the hydraulic cylinder body includes A rod chamber and a rod chamber, the cross-sectional area of the rodless chamber connected to the oil inlet is equal to the cross-sectional area of the rod chamber connected to the oil outlet. 2. The multi-cavity oil cylinder closed hydraulic system according to claim 1, characterized in that: The hydraulic cylinder body includes a first cylinder body, a second cylinder body located inside the first cylinder body, and a piston sleeve assembly; The piston sleeve assembly includes a cylindrical first piston rod containing an inner cavity, a first piston connected to the first piston rod, a second piston rod connected to the inner cavity of the first piston rod and a second piston connected to the second piston rod, and the first piston rod is nested between the inner wall of the first cylinder and the outer wall of the second cylinder, and the second piston rod is set inside the second cylinder; The rodless chamber includes a first rodless chamber and a second rodless chamber; the rod chamber includes a first rod chamber and a second rod chamber, and the first piston is used to push the inner wall of the first cylinder The inner chamber between the outer wall of the second cylinder body is divided into the first rodless chamber and the first rod chamber, and the second piston is used to divide the inner chamber of the second cylinder body into the first rodless chamber. the second rodless cavity and the second rod cavity; The oil inlet connected to the closed pump is arranged on any one of the first rodless chamber and the second rodless chamber, and the first rodless chamber and the second rodless chamber There are oil outlets connected to the closed pump on the cavity; The area of the cross-section of the rodless cavity provided with the oil inlet is equal to the sum of the cross-sectional areas of the first rod cavity and the second rod cavity. 3. The multi-cavity oil cylinder closed hydraulic system according to claim 2, characterized in that: An accumulator is also included, and an oil port connected to the accumulator is opened on the above-mentioned rodless cavity where the oil inlet is not installed. 4. The multi-cavity cylinder closed hydraulic system according to claim 3, characterized in that: The accumulator is used to recover the hydraulic oil in the rodless cavity provided with the oil port when the piston sleeve assembly is lowered, and the accumulator is also used to release the hydraulic oil for the piston sleeve assembly when the piston sleeve assembly is raised. components provide auxiliary power. 5. The multi-cavity oil cylinder closed hydraulic system according to claim 2, characterized in that: The second cylinder is arranged coaxially with the first cylinder, and the cross section of the first rodless chamber is circular, and the cross section of the second rodless chamber is circular. 6. The multi-cavity oil cylinder closed hydraulic system according to claim 5, characterized in that: The first piston rod is a cylindrical piston rod with a built-in cavity, and the second piston rod is a cylindrical piston rod. 7. The multi-cavity oil cylinder closed hydraulic system according to claim 2, characterized in that: A holding valve is also included, and the holding valve is arranged between the closed pump and the rodless cavity provided with the oil inlet. 8. The multi-cavity cylinder closed hydraulic system according to any one of claims 1-7, characterized in that: The closed pump is connected with the engine, and the closed pump is used to drive the engine to rotate when the piston sleeve assembly descends. 9. A construction machine, characterized in that it comprises the multi-cavity oil cylinder closed hydraulic system according to any one of claims 1-8 and a boom, and the boom is connected to the hydraulic cylinder. 10. The construction machine according to claim 9, characterized in that: The number of the hydraulic cylinders is an even number, and the hydraulic cylinders are arranged in parallel on the lower side of the boom.