Hollow piston rod hydraulic cylinder with equal reciprocating speed and through oil way structure

Abstract

The invention provides a hollow piston rod hydraulic cylinder with an equal reciprocating speed and a middle through oil way structure, and belongs to the field of design and manufacturing of piston rod type hydraulic cylinders and design of hydraulic systems, the hollow piston rod hydraulic cylinder comprises a hydraulic cylinder shell, a hollow piston rod and a moving carrier, and the hollow piston rod is arranged in the hydraulic cylinder shell; a single-action hydraulic cylinder is installed on the moving carrier and connected with a cavity of the hollow piston rod through a connecting oil way of the moving carrier. Due to the arrangement of the middle oil pipe, the acting areas of the two ends of the piston of the hydraulic cylinder are approximately equal, and the device can control the moving carrier to reciprocate at the same speed by controlling the stretching of the hollow piston rod hydraulic cylinder; through the middle oil pipe at the cylinder bottom and the cavity structure of the hollow piston rod, the function of oil passing inside the piston rod is achieved, arrangement of an external oil pipe oil way is avoided, and the hydraulic pipeline design problem of a moving carrier provided with a hydraulic system or a hydraulic executing mechanism under the moving working condition is solved.

Description

Technical Field

[0001] The invention relates to the field of design and manufacture of piston rod type hydraulic cylinders and hydraulic system design, and in particular to a hollow piston rod hydraulic cylinder with equal reciprocating speed and a central oil path structure. Background Art

[0002] Hydraulic cylinders are core components of hydraulic systems. Their development history is basically consistent with the development of the hydraulic industry. They are widely used in engineering machinery, engineering robots and other fields. As the design of hydraulic systems develops towards high integration and lightweight, higher requirements are placed on the functions of hydraulic cylinders. In particular, in some special application fields, there are stringent requirements for engineering machinery. For example, hydraulic cylinders need to have longer strokes and installation distances, as well as more compact installation spaces, and be able to achieve the telescopic function of mechanisms at specific locations in narrow spaces.

[0003] At the same time, the hydraulic cylinder needs to have a long-stroke telescopic function in engineering use, and it also needs to carry a hydraulic actuator on the driven object. This means that when designing, it is not only necessary to meet the external oil pipe layout requirements of the long-stroke hydraulic cylinder, but also to connect the hydraulic pipeline to the hydraulic actuator on the driven object and provide hydraulic oil. The above problems make the system design very difficult, and it is even more difficult to implement it in a small space.

[0004] Therefore, the external oil pipe of the hydraulic system or hydraulic actuator on the existing hydraulic cylinder and its driving carrier has the disadvantages of difficulty in arranging the external oil source of the hydraulic system or hydraulic actuator on the mobile carrier, the self-prepared oil source is of large quality, and the movement performance of the mobile carrier is affected. Summary of the invention

[0005] The purpose of the present invention is to provide a hollow piston rod hydraulic cylinder with a central oil circuit structure with equal reciprocating speeds. By controlling the extension and contraction of the hollow piston rod hydraulic cylinder, the mobile carrier can be controlled to perform reciprocating motion at equal speeds. The central oil pipe at the bottom of the cylinder and the cavity structure of the hollow piston rod realize the function of passing oil inside the piston rod, avoiding the layout of external oil pipes and oil circuits. The present invention solves the hydraulic pipeline design problem under the motion condition of a mobile carrier equipped with a hydraulic system or a hydraulic actuator driven by a hydraulic cylinder piston rod, reduces the layout space of the external pipelines originally required, and is easy to disassemble and assemble.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A hollow piston rod hydraulic cylinder with equal reciprocating speed and a through oil circuit structure, characterized in that it includes a hydraulic cylinder housing, a hollow piston rod and a moving carrier, the hollow piston rod is arranged inside the hydraulic cylinder housing, a single-acting hydraulic cylinder is installed on the moving carrier, and the single-acting hydraulic cylinder is connected to the cavity of the hollow piston rod through the connecting oil circuit of the moving carrier.

[0008] Furthermore, the hydraulic cylinder housing includes a cylinder bottom, a cylinder head, a cylinder barrel, a cylinder cover and a guide sleeve, the cylinder bottom is arranged on one side of the hydraulic cylinder housing, the cylinder head is arranged on the other side of the hydraulic cylinder housing, the cylinder bottom and the cylinder head are connected by a plurality of tie rods, one end of the cylinder barrel is connected to the cylinder bottom, the other end of the cylinder barrel is connected to the cylinder head, the hollow piston rod is arranged inside the cylinder barrel, the cylinder cover is fixed to the cylinder head by a countersunk screw, and the guide sleeve is arranged between the cylinder head and the hollow piston rod.

[0009] Furthermore, a first opening is provided at the center of the cylinder bottom, and a second opening is provided at the center of the cylinder head. One end of the through oil pipe is connected to the first opening, and the other end of the through oil pipe is flush with the end surface of the second opening. The through oil pipe passes through the hollow piston rod along the axial center line of the hydraulic cylinder housing and the hollow piston rod, and the aperture of the second opening is equal to the outer diameter of the hollow piston rod.

[0010] Furthermore, the hollow piston rod includes a first piston and a sealing device, the first piston is threaded or welded to one end of the hollow piston rod, the first piston is slidably arranged inside the cylinder, the first piston divides the cylinder into a first oil chamber and a second oil chamber, and the sealing device is arranged at the end of the first piston.

[0011] Furthermore, the cylinder bottom is provided with a first oil port, which connects the first oil chamber and the outside world; the end of the through oil pipe close to the cylinder bottom is provided with a second oil port connected to the outside world; the through oil pipe and the internal cavity of the hollow piston rod form a through oil path structure; the cylinder head is provided with a third oil port, which connects the second oil chamber and the outside world; the other end of the hollow piston rod is provided with a fourth oil port.

[0012] Furthermore, the single-acting hydraulic cylinder is provided with a fifth oil port, and the fifth oil port of the single-acting hydraulic cylinder is connected to the fourth oil port of the hollow piston rod through a connecting oil path of the mobile carrier.

[0013] Furthermore, a single output rod matching with the single-acting hydraulic cylinder is installed inside, a second piston is connected to the single output rod by threaded connection or welding, a spring is arranged on the top of the second piston, and the spring is connected to the top of the inner cavity of the single-acting hydraulic cylinder.

[0014] Furthermore, a plurality of threaded holes are evenly arranged at one end of the cylinder head, one end of a plurality of tie rods is connected to the cylinder head through threads, and the other end of the plurality of tie rods is connected to the cylinder bottom through a plurality of nuts.

[0015] Furthermore, a sealing ring is provided at the connection between the cylinder barrel and the cylinder bottom and the cylinder head, a dust ring that fits with the middle piston rod is provided at the inner ring groove of the cylinder head, a sealing ring is provided at the inner ring groove of the guide sleeve, a guide ring and a sealing ring are provided at the side ring groove of the first piston, and a sliding sealing ring that fits with the middle oil pipe is provided in the inner ring groove of the hollow piston rod.

[0016] Furthermore, connection forms of the first oil port, the second oil port, the third oil port, the fourth oil port and the fifth oil port include threaded connection, flange connection, plate connection, stacking connection and plug-in connection.

[0017] Advantages of the present invention:

[0018] 1. Due to the structure of the internal through oil circuit of the hollow piston rod hydraulic cylinder of the present invention, the contact area of ​​the hydraulic oil on both sides of the piston of the hollow piston rod hydraulic cylinder is approximately equal, that is, the oil pressure in the oil chamber on both sides of the hollow piston rod hydraulic cylinder is the same, that is, the thrust exerted on the piston and the speed of movement are approximately the same. By controlling the extension and contraction of the hollow piston rod hydraulic cylinder, the mobile carrier can be controlled to perform reciprocating motion at an equal speed.

[0019] 2. The hollow structure of the through oil pipe at the bottom of the cylinder and the hollow piston rod forms the structure of the through oil circuit, which realizes the function of oil passing through the piston rod, avoids the layout of the external oil pipe and oil circuit, and does not affect the oil circuit of the hydraulic cylinder itself for realizing the telescopic function; at the same time, the through oil circuit structure solves the problem of hydraulic pipeline design under the motion condition of the mobile carrier equipped with a hydraulic system or a hydraulic actuator driven by the hydraulic cylinder piston rod, and optimizes the structure of such hydraulic system; the connecting oil circuit is installed on the mobile carrier, and the oil port on the hollow piston rod is connected with the oil port of the hydraulic actuator, which also reduces the layout of the external oil circuit originally required; it realizes that when there is no oil pipe in the outside world, the mobile carrier is connected to an external oil source, which simplifies the hydraulic system structure on the carrier; reduces the quality of the hydraulic system and improves the controllability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural cross-sectional view of the present invention;

[0021] Figure 2 It is a structural cross-sectional view of the hollow piston rod hydraulic cylinder of the present invention;

[0022] Figure 3 is a structural cross-sectional view of the mobile carrier in the present invention;

[0023] In the figure: 1, hydraulic cylinder housing; 1-1, cylinder bottom; 1-2, cylinder head; 1-3, cylinder barrel; 1-4, cylinder cover; 1-5, guide sleeve; 1-6, first oil port; 1-7, second oil port; 1-8, third oil port; 1-9, middle oil pipe; 1-10, first oil chamber; 1-11, second oil chamber;

[0024] 2. Hollow piston rod; 2-1. First piston; 2-2. Sealing device; 2-3. Fourth oil port;

[0025] 3. Mobile carrier; 3-1. Connect oil circuit;

[0026] 4. Single-acting hydraulic cylinder; 4-1. Fifth oil port; 4-2. Second piston. DETAILED DESCRIPTION

[0027] 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 are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention.

[0028] like Figure 1 As shown, a hollow piston rod hydraulic cylinder with equal reciprocating speed and a through oil circuit structure includes a hydraulic cylinder housing 1, a hollow piston rod 2 and a moving carrier 3. The hollow piston rod 2 is arranged inside the hydraulic cylinder housing 1, and a single-acting hydraulic cylinder 4 is installed on the moving carrier 3. The single-acting hydraulic cylinder 4 is connected to the cavity of the hollow piston rod 2 through the connecting oil circuit 3-1 of the moving carrier 3.

[0029] As a preferred embodiment of the present invention, Figure 2 As shown, the hydraulic cylinder housing 1 includes a cylinder bottom 1-1, a cylinder head 1-2, a cylinder barrel 1-3, a cylinder cover 1-4 and a guide sleeve 1-5. The cylinder bottom 1-1 is arranged on one side of the hydraulic cylinder housing 1, and the cylinder head 1-2 is arranged on the other side of the hydraulic cylinder housing 1. The cylinder bottom 1-1 and the cylinder head 1-2 are connected by a plurality of tie rods. One end of the cylinder barrel 1-3 is connected to the cylinder bottom 1-1, and the other end of the cylinder barrel 1-3 is connected to the cylinder head 1-2. The hollow piston rod 2 is arranged inside the cylinder barrel 1-3. The cylinder cover 1-4 is fixed to the cylinder head 1-2 by countersunk screws, and the guide sleeve 1-5 is arranged between the cylinder head 1-2 and the hollow piston rod 2.

[0030] As a preferred embodiment of the present invention, a first opening is provided at the center of the cylinder bottom 1-1, and a second opening is provided at the center of the cylinder head 1-2. One end of the through oil pipe 1-9 is connected to the first opening and the external hydraulic oil circuit, and the other end of the through oil pipe 1-9 is flush with the end surface of the second opening. The through oil pipe 1-9 passes through the hollow piston rod 2 along the axial center line of the hydraulic cylinder housing 1 and the hollow piston rod 2. The aperture of the second opening is equal to the outer diameter of the hollow piston rod 2, thereby ensuring that the hollow piston rod 2 can be inserted into the inner cavity of the cylinder barrel 1-3.

[0031] The cavity diameter of the hollow piston rod 2 is equal to the nominal size of the outer diameter of the through oil pipe 1-9, ensuring that the through oil pipe can be inserted into the cavity of the hollow piston rod 2.

[0032] As a preferred embodiment of the present invention, the hollow piston rod 2 includes a first piston 2-1 and a sealing device 2-2. The first piston 2-1 is threaded or welded to one end of the hollow piston rod 2. The first piston 2-1 is slidably arranged inside the cylinder 1-3. The first piston 2-1 divides the cylinder 1-3 into a first oil chamber 1-10 and a second oil chamber 1-11. The sealing device 2-2 is arranged at the end of the first piston 2-1.

[0033] As a preferred embodiment of the present invention, the cylinder bottom 1-1 is provided with a first oil port 1-6, which connects the first oil chamber 1-10 with the outside world, and the through oil pipe 1-9 is provided with a second oil port 1-7 connected to the outside world at one end close to the cylinder bottom 1-1, and the through oil pipe 1-9 and the internal cavity of the hollow piston rod 2 form a through oil path structure, and the cylinder head 1-2 is provided with a third oil port 1-8, and the third oil port 1-8 connects the second oil chamber 1-11 with the outside world, and the other end of the hollow piston rod 2 is provided with a fourth oil port 2-3.

[0034] As a preferred embodiment of the present invention, Figure 1 and Figure 3 As shown, the single-acting hydraulic cylinder 4 is provided with a fifth oil port 4 - 1 , and the fifth oil port 4 - 1 of the single-acting hydraulic cylinder 4 is connected to the fourth oil port 2 - 3 of the hollow piston rod 2 through the connecting oil path 3 - 1 of the mobile carrier 3 .

[0035] The hydraulic oil flows in from the central oil pipe 1-9, flows through the cavity of the hollow piston rod, flows out from the internal cavity of the hollow piston rod 2, and flows into the fifth oil port 4-1 of the single-acting hydraulic cylinder 4 through the connecting oil path 3-1.

[0036] As a preferred embodiment of the present invention, the single-acting hydraulic cylinder 4 is internally installed with a single output rod that matches it, and the single output rod is connected to a second piston 4-2 by threaded connection or welding. A spring is arranged on the top of the second piston 4-2, and the spring is connected to the top of the inner cavity of the single-acting hydraulic cylinder 4.

[0037] As a preferred embodiment of the present invention, a plurality of threaded holes are evenly arranged at one end of the cylinder head 1-2, one end of a plurality of tie rods are connected to the cylinder head 1-2 through threads, and the other ends of the plurality of tie rods are connected to the cylinder bottom 1-1 through a plurality of nuts, and the plurality of tie rods can protect the cylinder barrel 1-3 and support the load.

[0038] As a preferred embodiment of the present invention, a sealing ring is provided at the connection between the cylinder barrel 1-3 and the cylinder bottom 1-1 and the cylinder head 1-2, a dust ring that fits with the middle piston rod 2 is provided at the inner ring groove of the cylinder head 1-4, a sealing ring is provided at the inner ring groove of the guide sleeve 1-5, a guide ring and a sealing ring are provided at the side ring groove of the first piston 2-1, and a sliding sealing ring that fits with the middle oil pipe 1-9 is provided in the inner ring groove of the hollow piston rod 2.

[0039] As a preferred embodiment of the present invention, the connection forms of the first oil port 1-6, the second oil port 1-7, the third oil port 1-8, the fourth oil port 2-3 and the fifth oil port 4-1 include threaded connection, flange connection, plate connection, stacking connection and plug-in connection.

[0040] The hollow piston rod 2 is connected to the mobile carrier 3. When the hydraulic oil flows from the first oil port 1-6 into the first oil chamber 1-10, the first piston 2-1 is lifted up, pushing the hollow piston rod 2 to move outward, and the first piston 2-1 extends outward, pushing the mobile carrier 3 connected thereto to move outward. Similarly, when the hollow piston rod hydraulic cylinder retracts, the mobile carrier 3 also moves back. By controlling the extension and retraction of the hollow piston rod hydraulic cylinder, the reciprocating motion of the mobile carrier 3 can be controlled.

[0041] The mobile carrier 3 is equipped with a single-acting hydraulic cylinder 4 as an actuator. While the reciprocating motion of the mobile carrier 3 is controlled by the hollow piston rod 2, the hydraulic oil flows from the outside into the central oil path 1-9 through the second oil port 1-7, flows into the cavity of the hollow piston rod 2 along the central oil path 1-9, and then flows from the fourth oil port 2-3 of the cavity of the hollow piston rod 2 into the connecting oil path 3-1, and flows into the fifth oil port 4-1 of the single-acting hydraulic cylinder 4 through the connecting oil path 3-1, so that the single-acting hydraulic cylinder 4 performs corresponding telescopic movements. The telescopic function of the single-acting hydraulic cylinder 4 is controlled by the oil flow from the central oil pipe 1-9 to the central oil path 1-9 of the hollow piston rod cavity 2 and the connecting pipeline 3-1, and the movement direction is perpendicular to the movement direction of the mobile carrier 3. The purpose of controlling movement in two directions is achieved while reducing the external oil circuit.

[0042] The working principle of the present invention is as follows:

[0043] like Figure 2 As shown, the hollow piston rod 2 is connected to the mobile carrier 3. When the hydraulic oil flows from the first oil port 1-6 of the cylinder bottom 1-1 of the hydraulic cylinder into the first oil chamber 1-10 of the hydraulic cylinder, the piston of the hollow piston rod 2 is lifted, the hollow piston rod 2 is pushed outward, and the mobile carrier 3 connected thereto is pushed outward until the required distance is reached. At the same time, the hydraulic oil in the second oil chamber 1-11 is squeezed and flows back to the oil tank from the third oil port 1-8 installed on the cylinder head 1-2. Similarly, when the hydraulic oil flows from the third oil port 1-8 of the cylinder head 1-2 of the hydraulic cylinder into the second oil chamber 1-11 of the hydraulic cylinder, the first piston 2-1 of the hollow piston rod 2 is pushed, the first piston 2-1 of the hydraulic cylinder retracts inward, and the hollow piston rod 2 is pushed inward, pulling the mobile carrier 3 connected thereto to move inward until the required distance is reached. At the same time, the hydraulic oil in the first oil chamber 1-10 is squeezed and flows back to the oil tank from the first oil port 1-6 installed on the cylinder bottom 1-1. By controlling the extension and retraction of the hollow piston rod 2 , the reciprocating motion of the mobile carrier 3 can be controlled.

[0044] While the reciprocating motion of the mobile carrier 3 is controlled by the hollow piston rod 2, the hydraulic oil flows into the through oil pipe 1-9 through the second oil port 1-7 at one end of the through oil pipe 1-9 close to the cylinder bottom 1-1 through the hydraulic pump, flows into the cavity of the hollow piston rod 2 along the through oil pipe 1-9, and then flows into the connecting oil path 3-1 from the fourth oil port 2-3 of the hollow piston rod 2, and flows into the fifth oil port 4-1 of the single-acting hydraulic cylinder 4 through the connecting oil path 3-1, thereby lifting the second piston 4-2 of the single-acting hydraulic cylinder 4, so that the second piston 4- 2 shrinks inwards, the spring is compressed, and the single-acting hydraulic cylinder 4 extends. Similarly, when the second oil port 1-7 is connected to the oil tank, the hydraulic oil flows into the connecting oil path 3-1 through the fifth oil port 4-1 of the single-acting hydraulic cylinder 4, and then flows into the cavity of the hollow piston rod 2 through the fourth oil port 2-3 of the hollow piston rod 2. Then the hydraulic oil enters the central oil pipe 1-9, and then flows back to the oil tank through the second oil port 1-7. The spring restores its original length, pushing the second piston 4-2 of the single-acting hydraulic cylinder 4 to move outward, completing the retraction of the single-acting hydraulic cylinder 4. Thus, the telescopic function of the single-acting hydraulic cylinder 4 is controlled.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art can still adjust the technical solutions described in the above embodiments or replace some of the technical features by equivalents. Therefore, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A hollow piston rod hydraulic cylinder with equal reciprocating speed and a central oil passage structure, characterized in that: The invention comprises a hydraulic cylinder housing (1), a hollow piston rod (2) and a movable carrier (3); the hollow piston rod (2) is arranged inside the hydraulic cylinder housing (1); a single-acting hydraulic cylinder (4) is installed on the movable carrier (3); the single-acting hydraulic cylinder (4) is connected to the cavity of the hollow piston rod (2) via a connecting oil circuit (3-1) of the movable carrier (3).

2. A hollow piston rod hydraulic cylinder with equal reciprocating speed and a central oil passage structure according to claim 1, characterized in that: The hydraulic cylinder housing (1) comprises a cylinder bottom (1-1), a cylinder head (1-2), a cylinder barrel (1-3), a cylinder cover (1-4) and a guide sleeve (1-5); the cylinder bottom (1-1) is arranged on one side of the hydraulic cylinder housing (1), and the cylinder head (1-2) is arranged on the other side of the hydraulic cylinder housing (1); the cylinder bottom (1-1) and the cylinder head (1-2) are connected by a plurality of tie rods; one end of the cylinder barrel (1-3) is connected to the cylinder bottom (1-1), and the other end of the cylinder barrel (1-3) is connected to the cylinder head (1-2); the hollow piston rod (2) is arranged inside the cylinder barrel (1-3); the cylinder cover (1-4) is fixed to the cylinder head (1-2) by countersunk screws; and the guide sleeve (1-5) is arranged between the cylinder head (1-2) and the hollow piston rod (2).

3. A hollow piston rod hydraulic cylinder with equal reciprocating speed and a central oil passage structure according to claim 2, characterized in that: A first opening is provided at the center of the cylinder bottom (1-1), a second opening is provided at the center of the cylinder head (1-2), one end of the through oil pipe (1-9) is connected to the first opening, the other end of the through oil pipe (1-9) is flush with the end surface of the second opening, the through oil pipe (1-9) passes through the hollow piston rod (2) along the axial center line of the hydraulic cylinder housing (1) and the hollow piston rod (2), and the aperture of the second opening is equal to the outer diameter of the hollow piston rod (2).

4. A hollow piston rod hydraulic cylinder with equal reciprocating speed and a central oil passage structure according to claim 3, characterized in that: The hollow piston rod (2) comprises a first piston (2-1) and a sealing device (2-2); the first piston (2-1) is threadedly connected or welded to one end of the hollow piston rod (2); the first piston (2-1) is slidably arranged inside the cylinder barrel (1-3); the first piston (2-1) divides the cylinder barrel (1-3) into a first oil chamber (1-10) and a second oil chamber (1-11); and the sealing device (2-2) is arranged at the end of the first piston (2-1).

5. A hollow piston rod hydraulic cylinder with equal reciprocating speed and a central oil passage structure according to claim 4, characterized in that: The cylinder bottom (1-1) is provided with a first oil port (1-6), the first oil port (1-6) is connected with the first oil chamber (1-10) and the outside world; the through oil pipe (1-9) is provided with a second oil port (1-7) connected with the outside world at one end close to the cylinder bottom (1-1); the through oil pipe (1-9) and the inner cavity of the hollow piston rod (2) form a through oil path structure; the cylinder head (1-2) is provided with a third oil port (1-8), the third oil port (1-8) is connected with the second oil chamber (1-11) and the outside world; the other end of the hollow piston rod (2) is provided with a fourth oil port (2-3).

6. A hollow piston rod hydraulic cylinder with equal reciprocating speed and a central oil passage structure according to claim 5, characterized in that: The single-acting hydraulic cylinder (4) is provided with a fifth oil port (4-1), and the fifth oil port (4-1) of the single-acting hydraulic cylinder (4) is connected to the fourth oil port (2-3) of the hollow piston rod (2) via a connecting oil path (3-1) of the mobile carrier (3).

7. A hollow piston rod hydraulic cylinder with equal reciprocating speed and a central oil passage structure according to claim 6, characterized in that: A single output rod matching the single-acting hydraulic cylinder (4) is installed inside the single-acting hydraulic cylinder (4), a second piston (4-2) is connected to the single output rod by threaded connection or welding, a spring is arranged on the top of the second piston (4-2), and the spring is connected to the top of the inner cavity of the single-acting hydraulic cylinder (4).

8. A hollow piston rod hydraulic cylinder with equal reciprocating speed and a central oil passage structure according to claim 7, characterized in that: One end of the cylinder head (1-2) is evenly provided with a plurality of threaded holes, one end of a plurality of tie rods is connected to the cylinder head (1-2) via threads, and the other ends of the plurality of tie rods are connected to the cylinder bottom (1-1) via a plurality of nuts.

9. A hollow piston rod hydraulic cylinder with equal reciprocating speed and a central oil passage structure according to claim 8, characterized in that: A sealing ring is provided at the connection between the cylinder barrel (1-3) and the cylinder bottom (1-1) and the cylinder head (1-2); a dust ring that fits the through piston rod (2) is provided at the inner ring groove of the cylinder cover (1-4); a sealing ring is provided at the inner ring groove of the guide sleeve (1-5); a guide ring and a sealing ring are provided at the side ring groove of the first piston (2-1); and a sliding sealing ring that fits the through oil pipe (1-9) is provided in the inner ring groove of the hollow piston rod (2).

10. A hollow piston rod hydraulic cylinder with equal reciprocating speed and a central oil passage structure according to claim 9, characterized in that: The connection forms of the first oil port (1-6), the second oil port (1-7), the third oil port (1-8), the fourth oil port (2-3) and the fifth oil port (4-1) include threaded connection, flange connection, plate connection, stacking connection and plug-in connection.

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