Symmetrical hydraulic cylinder

Abstract

The symmetrical hydraulic cylinder comprises a cylinder barrel and a piston rod, the piston rod is installed in the cylinder barrel in a sliding mode, a stroke cavity is formed in the piston rod, and a return stroke cavity is formed between the piston rod and the inner wall of the cylinder barrel. A stroke oil way communicated with the stroke cavity is arranged at the bottom of the cylinder barrel and used for providing stretching force of the piston rod; the head of the cylinder barrel is provided with a return oil way communicated with the return cavity and used for providing retraction force of the piston rod. By arranging the stroke cavity, the return stroke cavity and the corresponding oil way, the stretching force and the retracting force of the piston rod are equal under the same hydraulic pressure, symmetrical stress and balanced movement are achieved, and the problems of uneven movement and impact caused by unequal stress areas of a traditional hydraulic cylinder are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of hydraulic technology, and specifically to a symmetrical hydraulic cylinder. Background Technology

[0002] With the rapid development of global marine engineering, heavy equipment manufacturing, and automated production lines, hydraulic transmission systems have become widely used as core power devices in modern industry. Hydraulic cylinders, as the actuators in hydraulic systems that convert hydraulic energy into mechanical energy, directly affect the working efficiency and stability of the entire system. Especially in high-end equipment fields such as offshore platforms, large lifting equipment, and precision machine tools, increasingly higher demands are placed on the dynamic response characteristics, reversing smoothness, and output force consistency of hydraulic cylinders. As operating conditions become increasingly high-speed and high-frequency, the impact problem of hydraulic cylinders during rapid reversing processes is becoming increasingly prominent, becoming a key bottleneck restricting equipment performance improvement.

[0003] The common single-piston rod hydraulic cylinders widely used in engineering practice have a structural characteristic that results in a difference in the effective working area on both sides of the piston: one side represents the full cross-sectional area of ​​the cylinder barrel, while the other side requires deducting the cross-sectional area of ​​the piston rod. This inherent structural asymmetry leads to a significant difference in the output force generated when the hydraulic cylinder extends and retracts under the same working pressure. To address this issue, the industry typically employs techniques such as increasing the displacement of the hydraulic pump to compensate for the force difference, using proportional valves or servo valves for pressure compensation control, or achieving force balance through complex hydraulic control circuits. However, these methods generally suffer from drawbacks such as high system complexity, increased cost, and limited response speed. Especially under high-speed conditions requiring frequent reversals and a certain degree of acceleration, the inconsistency in the output forces of the two chambers can easily generate significant impacts and vibrations during reversals, affecting the stable operation and service life of the equipment.

[0004] In view of the above, in order to overcome the above technical problems, the present invention designs a symmetrical hydraulic cylinder, which solves the above technical problems. Summary of the Invention

[0005] The technical objective of this invention is to provide a symmetrical hydraulic cylinder that achieves true balance of output forces at both ends through the structure of the hydraulic cylinder body.

[0006] To achieve the above-mentioned technical objectives, the present invention provides the following technical solution: The present invention provides a symmetrical hydraulic cylinder, including a cylinder barrel and a piston rod. The piston rod has a stroke cavity, and the piston rod is slidably installed in the cylinder barrel. The piston rod body and the cavity of the inner wall of the cylinder barrel form a return cavity. It also includes a stroke oil passage and a return oil passage. The stroke oil passage is located at the bottom of the cylinder and is connected to the stroke chamber to provide an extension force for the piston rod. The return oil passage is located at the head of the cylinder and is connected to the return chamber to provide a retraction force for the piston rod. The extension force and the retraction force are equal.

[0007] Furthermore, the outer diameter of the piston rod is d, the inner diameter of the stroke chamber is D2, the inner diameter of the cylinder is D1, and d² + D2² = D1².

[0008] When the hydraulic oil enters the stroke oil passage, the hydraulic oil enters the stroke cavity with an inner diameter of D2, and the resulting extension force is F1=P×π×D2² / 4; when the hydraulic oil enters the return oil passage, the hydraulic oil enters the annular cavity between the inner diameter of the cylinder D1 and the outer diameter of the piston rod d, and the resulting retraction force is F2=P×π×(D1²-d²) / 4; where P is the pressure of the hydraulic oil in the oil passage.

[0009] Based on the above, preferably, a stroke sensor is installed on the cylinder and piston rod to detect the movement stroke of the piston rod.

[0010] More preferably, the stroke sensor includes a sensor electronic compartment and a sensor magnetic scale, the sensor electronic compartment being installed at the center of the bottom of the cylinder, and the sensor magnetic scale being installed at the axis of the piston rod.

[0011] The piston rod is connected to a connecting lug, and the cylinder is connected to a connecting shaft seat; the connecting lug is installed on the head of the piston rod by a threaded connection, and the connecting shaft seat is installed on the outer wall of the piston rod by welding.

[0012] On the other hand, the bottom of the cylinder is also provided with a balance oil passage, which is connected to the bottom of the piston rod and is used to balance system errors; the system errors include the force generated by the weight of the piston rod and the force generated by the system operation error.

[0013] Furthermore, F1 + F0 = F2, where F0 is the systematic error.

[0014] The beneficial effects of this invention are as follows: 1. This invention provides a stroke cavity inside the piston rod, connecting it to the stroke oil passage at the bottom of the cylinder. Simultaneously, a return oil passage at the cylinder head connects to the return cavity, allowing hydraulic oil to act on both the inner and annular cavities. This ensures equal extension and retraction forces under the same hydraulic oil pressure. Furthermore, the Pythagorean theorem-based dimensional design ensures symmetrical force distribution on the piston rod during extension and retraction, effectively avoiding the uneven motion caused by unequal effective pressure areas in conventional single-piston hydraulic cylinders. This improves the stability and control accuracy of the hydraulic cylinder's reciprocating motion, reduces vibration and impact, and enhances system reliability and lifespan.

[0015] 2. By installing stroke sensors on the cylinder and piston rod, and using a sensor electronic compartment installed at the center of the bottom of the cylinder and a sensor magnetic scale installed at the center of the piston rod shaft, the sensors can detect the changes in the stroke position of the piston rod in real time during symmetrical motion. Utilizing the magnetic coupling detection principle, non-contact stroke monitoring is achieved, effectively improving the accuracy and response speed of hydraulic cylinder displacement detection. This facilitates closed-loop control of the piston rod movement and further enhances the automation control performance and safety of the hydraulic actuator.

[0016] 3. By adding a balance oil circuit at the bottom of the cylinder and connecting it to the bottom of the piston rod, and automatically compensating for the hydraulic oil flow based on the force balance relationship F1+F0=F2, the additional force caused by the piston rod gravity and system operation error is offset. During the hydraulic oil flow, dynamic pressure regulation is achieved through the balance oil circuit, which can effectively suppress the stroke deviation of the hydraulic cylinder under asymmetrical load or installation posture changes, ensure the balance and linearity of symmetrical motion, and thus improve the dynamic response stability and execution accuracy of the system. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] The above and other aspects of the invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 This is a schematic diagram of the present invention.

[0019] In the diagram: 1. Cylinder; 2. Piston rod; 3. Stroke chamber; 4. Return chamber; 5. Stroke oil passage; 6. Return oil passage; 7. Stroke sensor; 71. Sensor electronic compartment; 72. Sensor magnetic scale; 8. Connecting lug; 9. Connecting shaft seat; 10. Balance oil passage. Detailed Implementation

[0020] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods. Example 1

[0021] like Figure 1 As shown, this embodiment provides a symmetrical hydraulic cylinder, including a cylinder barrel 1 and a piston rod 2. The piston rod 2 is slidably installed inside the cylinder barrel 1. A stroke cavity 3 is formed inside the piston rod 2, and a return cavity 4 is formed between the piston rod 2 and the inner wall of the cylinder barrel 1. A stroke oil passage 5 is provided at the bottom of the cylinder barrel 1, which is connected to the stroke cavity 3, and is used to provide an extension force for the piston rod 2. A return oil passage 6 is provided at the head of the cylinder barrel 1, which is connected to the return cavity 4, and is used to provide a retraction force for the piston rod 2. The extension force and the retraction force are equal, so that the piston rod 2 is in a symmetrical force state during the extension and retraction processes. This ensures that the hydraulic cylinder is subjected to balanced forces during movement, resulting in smooth movement. This eliminates the uneven movement phenomenon caused by the unequal effective pressure area during the two strokes of a conventional single-piston hydraulic cylinder, thereby improving the control accuracy and operational stability of the hydraulic cylinder.

[0022] The outer diameter of the piston rod 2 is d, the inner diameter of the stroke chamber 3 is D2, and the inner diameter of the cylinder 1 is D1. To ensure symmetrical hydraulic oil action areas during extension and retraction, thus guaranteeing equal extension and retraction forces, the three satisfy the geometric relationship d² + D2² = D1². When oil enters the stroke oil passage 5, the hydraulic oil enters the stroke chamber 3 with an inner diameter of D2, generating an extension force F1 = P × π × D2² / 4. When oil enters the return oil passage 6, the hydraulic oil enters the annular cavity between the inner diameter D1 of the cylinder 1 and the outer diameter d of the piston rod 2, generating a retraction force F2 = P × π × (D1² − d²) / 4, where P is the pressure of the hydraulic oil in the oil passage. Through the above parameter design, F1 and F2 are made equal, achieving symmetrical movement of the hydraulic cylinder.

[0023] In this embodiment, a stroke sensor 7 is installed on the cylinder 1 and piston rod 2 to detect the movement stroke of the piston rod 2. The stroke sensor 7 includes a sensor electronic housing 71 and a sensor magnetic scale 72. The sensor electronic housing 71 is installed at the center of the bottom of the cylinder 1, and the sensor magnetic scale 72 is installed at the axis of the piston rod 2. The position of the piston rod 2 is monitored in real time through the magnetic coupling between the electronic housing and the magnetic scale. The detection accuracy is high and the response is fast, which facilitates the implementation of closed-loop control of the hydraulic cylinder movement.

[0024] In this embodiment, a connecting lug 8 is connected to the piston rod 2, and a connecting shaft seat 9 is connected to the cylinder 1. The connecting lug 8 is threaded onto the head of the piston rod 2, and the connecting shaft seat 9 is welded onto the outer wall of the cylinder 1. This structure allows the hydraulic cylinder to be easily connected to external mechanisms, ensuring reliable installation and high load-bearing capacity. Example 2

[0025] This embodiment is a further improvement on Embodiment 1, such as... Figure 1 As shown, a balance oil passage 10 is added to the bottom of the cylinder 1, which is connected to the bottom of the piston rod 2 to balance system errors. The system errors include the weight of the piston rod 2 and the additional force generated by system operation errors. When the hydraulic oil flows in the balance oil passage 10, it can slightly compensate for the force on the piston rod 2, so that the extension force F1, the retraction force F2, and the system error F0 satisfy the relationship F1+F0=F2. Thus, dynamic balance is automatically achieved when there is a deviation in the system, ensuring the symmetry and stability of the piston rod 2 during its movement.

[0026] The balancing oil circuit 10, through automatic fluid pressure regulation during hydraulic cylinder operation, counteracts the imbalance effect caused by the weight of the piston rod 2 or residual pressure differences in the system, thereby preventing stroke deviation when the hydraulic cylinder is not horizontally installed or under uneven load. This effectively improves the motion consistency and operational reliability of the hydraulic cylinder under complex working conditions, extending the service life of the equipment. The remaining structure and working principle of this embodiment are the same as in Embodiment 1, and will not be repeated here.

[0027] The working process of this invention is as follows: When the hydraulic system is started, hydraulic oil enters the stroke oil passage 5 at the bottom of the cylinder 1 through the control valve, and flows into the stroke chamber 3 inside the piston rod 2 along the stroke oil passage 5. Since the pressure-bearing area of ​​the stroke chamber 3 is π×D2² / 4, the hydraulic oil generates uniform pressure on this area, causing the piston rod 2 to extend outward axially. During this process, the return oil passage 6 at the head of the cylinder 1 serves as a return oil channel. While the hydraulic oil in the stroke chamber 3 pushes the piston rod 2 to move, it discharges the hydraulic oil in the return chamber 4 through the return oil passage 6, thus achieving a smooth extension of the piston rod 2.

[0028] When the hydraulic cylinder needs to retract, the hydraulic system reverses direction, and hydraulic oil enters from the return oil passage 6 at the head of cylinder 1, connecting with the annular cavity formed between the inner wall of cylinder 1 and the outer wall of piston rod 2. The pressure area generated by the hydraulic oil in the annular cavity is π×(D1²−d²) / 4. Since the geometric relationship d²+D2²=D1² is satisfied in the design, the extension force F1 and the retraction force F2 are equal at this time, thus ensuring that the piston rod 2 experiences consistent forces and symmetrical motion during the extension and retraction process under the same hydraulic pressure. During the return stroke, the stroke oil passage 5 at the bottom of cylinder 1 acts as the return port, discharging the hydraulic oil in the stroke cavity 3, and the piston rod 2 smoothly retracts to its initial position.

[0029] In Example 1, the movement of the hydraulic cylinder relies entirely on the hydraulic switching between the stroke oil circuit 5 and the return oil circuit 6 to achieve symmetrical movement, without considering the influence of additional loads or system deviations. This is suitable for situations where the structure is installed horizontally and the load is symmetrical. The symmetrical pressure structure ensures smooth movement, minimal impact, and sensitive response of the hydraulic cylinder throughout its entire stroke. The stroke sensor 7 detects the displacement of the piston rod 2 in real time during movement and feeds the displacement signal back to the control system, achieving precise control and monitoring of the stroke position.

[0030] In Embodiment 2, in addition to the above-described working process, the balance oil circuit 10 at the bottom of cylinder 1 plays a compensating role during the operation of the hydraulic cylinder. When there is an additional force F0 in the system caused by the weight of the piston rod 2 or the deviation of the installation angle, the hydraulic oil in the balance oil circuit 10 forms a small compensating pressure through pressure transmission, so that the extension force F1, the retraction force F2 and the system error F0 satisfy the balance relationship F1+F0=F2. This compensation process is dynamically and automatically adjusted without the need for additional control signals, and can maintain a symmetrical force state under different postures and load conditions of the hydraulic cylinder. Through this working mode, the hydraulic cylinder can still maintain the balance of extension and retraction motion under complex working conditions, eliminate the offset or vibration caused by system errors, and improve the operational stability and execution accuracy.

[0031] The description herein is provided to enable those skilled in the art to implement or use the present disclosure. Various modifications to the present disclosure will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other variations without departing from the scope of the disclosure. Therefore, this disclosure is not limited to the examples and designs described herein, but should be given the broadest scope consistent with the principles and novel features disclosed herein.

[0032] Although one or more exemplary embodiments of this disclosure have been described with reference to the accompanying drawings, those skilled in the art will understand that various changes in form and detail may be made therein without departing from the spirit and scope of this disclosure as defined by the appended claims.

[0033] The foregoing description is merely illustrative of this disclosure, and modifications may be made to the invention in light of the above detailed description. The terminology used in the appended claims should not be construed as limiting the invention to the specific embodiments disclosed in the specification. Rather, the scope of the invention will be fully defined by the appended claims, which will be interpreted according to established principles of claim interpretation.

Claims

1. A symmetrical hydraulic cylinder, characterized in that It comprises a cylinder (1) and a piston rod (2), the piston rod (2) is provided with a stroke cavity (3), the piston rod (2) is slidingly installed in the cylinder (1), the rod body of the piston rod (2) and the cavity of the inner wall of the cylinder (1) form a return cavity (4); It also comprises a stroke oil way (5) and a return oil way (6), the stroke oil way (5) is arranged at the bottom of the cylinder (1) and is communicated with the stroke cavity (3), used for providing the piston rod (2) with an extension force; the return oil way (6) is arranged at the head of the cylinder (1) and is communicated with the return cavity (4), used for providing the piston rod (2) with a retraction force; the extension force is equal to the retraction force.

2. The symmetrical hydraulic cylinder of claim 1, wherein: The outer diameter of the piston rod (2) is d, the inner diameter of the stroke cavity (3) is D2, the inner diameter of the cylinder (1) is D1, and d²+D2²=D1².

3. The symmetrical hydraulic cylinder of claim 2, wherein: When the stroke oil way (5) is filled with oil, the hydraulic oil enters the stroke cavity (3) with the inner diameter D2, and the generated extension force is F1=P×π×D2² / 4; when the return oil way (6) is filled with oil, the hydraulic oil enters the annular cavity between the inner diameter D1 of the cylinder (1) and the outer diameter d of the piston rod (2), and the generated retraction force is F2=P×π×(D1²-d²) / 4; wherein P is the pressure of the hydraulic oil in the oil way.

4. Symmetric hydraulic cylinder according to any of claims 1-3, characterized in that: The cylinder (1) and the piston rod (2) are provided with a stroke sensor (7) for detecting the movement stroke of the piston rod (2).

5. The symmetrical hydraulic cylinder of claim 4, wherein: The stroke sensor (7) comprises a sensor electronic bin (71) and a sensor magnetic ruler (72), the sensor electronic bin (71) is installed at the center of the bottom of the cylinder (1), and the sensor magnetic ruler (72) is installed at the shaft center of the piston rod (2).

6. The symmetrical hydraulic cylinder according to any one of claims 1-3, characterized in that: The piston rod (2) is connected with a connecting ear ring (8), and the cylinder (1) is connected with a connecting shaft seat (9); the connecting ear ring (8) is installed on the head of the piston rod (2) through threaded connection, and the connecting shaft seat (9) is installed on the outer wall of the rod cylinder through welding.

7. The symmetrical hydraulic cylinder of claim 3, wherein: The bottom of the cylinder (1) is also provided with a balance oil way (10), the balance oil way (10) is communicated with the bottom of the piston rod (2) and is used for balancing system errors; the system errors include the force generated by the gravity of the piston rod (2) and the system running error.

8. The symmetrical hydraulic cylinder of claim 7, wherein: F1+F0=F2, wherein F0 is the system error.

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