Thin cylinder with displacement sensor

Abstract

The utility model discloses a kind of thin oil cylinder with displacement sensor, including oil cylinder body and the displacement sensor being located at oil cylinder end part, the displacement sensor is magnetostrictive sensor, it includes waveguide tube that stretches into cylinder barrel, the piston of the oil cylinder body is equipped with the magnetic ring that is inducted with the waveguide tube;The oil cylinder body includes sensor mounting end cap, the inboard surface of the sensor mounting end cap is equipped with the counterbore of axial extension;The side of the piston close to the sensor mounting end cap is fixedly connected with mounting seat, the magnetic ring is embedded on the mounting seat;The axial thickness of the magnetic ring, so that when the piston moves to the first limit position of the sensor mounting end cap side, the mounting seat can be completely accommodated in the counterbore, to make the axial center plane of the magnetic ring infinitely close to the theoretical installation surface of the displacement sensor electronic head.The utility model can significantly reduce the size of oil cylinder axial direction, and make the measurement dead zone minimization.

Description

Technical Field

[0001] This utility model relates to the field of hydraulic cylinder technology, and in particular to a thin hydraulic cylinder with a displacement sensor. Background Technology

[0002] In the field of industrial automation, precise control of hydraulic cylinder piston displacement is crucial. Magnetostrictive displacement sensors are widely used for hydraulic cylinder position detection due to their high accuracy and reliability. These sensors typically include an electronic head fixed to the cylinder end cap and a waveguide extending into the cylinder barrel. A magnetic ring is mounted on the piston, inducing movement with the waveguide. Installing this displacement sensor on the cylinder hardly affects its radial dimensions, and the cylinder stroke is unrestricted. The cylinder bore can also be machined as a through hole, simplifying the manufacturing process. Therefore, magnetostrictive displacement sensors are particularly suitable for displacement detection in thin-walled hydraulic cylinders.

[0003] However, in actual installation, due to the thickness of the sensor mounting end cap and the axial dimensions and assembly clearances of the magnetic ring mounting structure, when the piston moves to its limit position near the end cap, the magnetic field center plane of the magnetic ring is still far from the theoretical mounting surface. This creates a measurement dead zone that cannot be effectively detected at the end of the stroke near the end cap. This dead zone, introduced by the mechanical structure, significantly reduces the effective stroke of the hydraulic cylinder. Summary of the Invention

[0004] Purpose of the invention: In order to overcome the shortcomings of the existing technology, this utility model provides a thin hydraulic cylinder with displacement sensor, which can significantly reduce the axial dimension of the hydraulic cylinder to meet the size requirements of thin hydraulic cylinder, while minimizing the measurement dead zone.

[0005] Technical Solution: To achieve the above objectives, this utility model provides a thin hydraulic cylinder with a displacement sensor, comprising a cylinder body and a displacement sensor disposed at the end of the cylinder. The displacement sensor is a magnetostrictive sensor, which includes a waveguide extending into the cylinder barrel. A magnetic ring that interacts with the waveguide is provided on the piston of the cylinder body. The cylinder body includes a sensor mounting end cap, and an axially extending countersunk hole is provided on the inner side of the sensor mounting end cap. A mounting base is fixedly connected to the side of the piston near the sensor mounting end cap, and the magnetic ring is embedded in the mounting base. The axial thickness of the magnetic ring is such that when the piston moves to the first extreme position on the side of the sensor mounting end cap, the mounting base can be completely accommodated in the countersunk hole, so that the axial center plane of the magnetic ring is infinitely close to the theoretical mounting surface of the displacement sensor electronic head.

[0006] Furthermore, the mounting base is provided with an axially extending insert groove on the side near the theoretical mounting surface, the magnetic ring is interference-fitted with the insert groove, and a retaining ring is engaged on the side of the magnetic ring near the theoretical mounting surface.

[0007] Furthermore, both the mounting base and the retaining ring are made of non-magnetic materials.

[0008] Furthermore, the mounting base and the countersunk hole are in a clearance fit or a transition fit, with the clearance used to allow hydraulic oil to pass through, and the outer surface of the mounting base is a smooth surface.

[0009] Furthermore, when the piston is in the first extreme position, there is a gap or contact between the end face of the mounting base and the bottom surface of the countersunk hole.

[0010] Furthermore, the mounting base is provided with a magnetically conductive assembly for enhancing the radial magnetic field of the magnetic ring; the magnetically conductive assembly includes two magnetically conductive bodies, which are respectively disposed in the two radial magnetic pole regions of the magnetic ring and in contact with the radial magnetic pole surface of the magnetic ring.

[0011] Furthermore, the axial center plane of the magnetic conductor is offset towards the theoretical mounting surface relative to the axial center plane of the magnetic ring.

[0012] Furthermore, the thickness of the magnetic conductor at the end closest to the theoretical mounting surface in the axial direction is greater than the thickness at the end furthest from the theoretical mounting surface.

[0013] Beneficial Effects: This utility model discloses a thin-film hydraulic cylinder with a displacement sensor. Through the nested structure of the mounting base and the countersunk hole, the center plane of the magnetic ring is made infinitely close to the theoretical sensing surface of the sensor when the piston is at its extreme position. This completely eliminates the measurement dead zone introduced by mechanical factors such as end caps and mounting structures, retaining only the sensor's inherent physical minimum dead zone and maximizing the effective stroke of the hydraulic cylinder. While achieving a thinner magnetic ring assembly to adapt to compact spaces, the addition of a oriented and optimized magnetic guiding component effectively enhances and focuses the radial magnetic field, ensuring that the thin magnetic ring still has a sufficiently strong and stable signal at critical dead zone positions, thus resolving the contradiction between compactness and reliability. The magnetic ring adopts a stable mounting method with an interference fit and a retaining ring for limiting, and the fit between the mounting base and the countersunk hole is reasonable, taking into account smooth movement, sealing, and structural strength. Attached Figure Description

[0014] Figure 1 This is a cross-sectional schematic diagram of an embodiment of the present invention with the piston in the first extreme position.

[0015] Figure 2 for Figure 1 A magnified view of a portion of point A in the middle. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings.

[0017] As attached Figure 1-2A thin hydraulic cylinder with a displacement sensor includes a cylinder body and a displacement sensor located at the end of the cylinder. The cylinder body includes a cylinder barrel, a piston 2, a piston rod, and a sensor mounting end cap 4. The displacement sensor is a magnetostrictive sensor, and its electronic head is fixedly mounted on the outside of the sensor mounting end cap 4. A waveguide 1 inside the waveguide 1 extends axially into the cylinder barrel through the central hole of the end cap. The piston 2 is provided with a magnetic ring 3 that interacts with the waveguide 1.

[0018] The inner side of the sensor mounting end cover 4 is machined with an axially extending cylindrical countersunk hole 41; the piston 2 is fixedly connected to the mounting base 5 on the side near the sensor mounting end cover 4 by means of screws or threads, and the center of the mounting base 5 has a through hole for the waveguide 1 to pass through.

[0019] The mounting base 5 has an axially extending insert groove on the side near the theoretical mounting surface. The magnetic ring 3 is embedded in the insert groove with an interference fit. On the side of the magnetic ring 3 near the sensor electronic head, a retaining ring 6 is fixedly installed to limit the axial movement and prevent the magnetic ring 3 from coming out under hydraulic pressure impact or vibration.

[0020] Preferably, both the mounting base 5 and the retaining ring 6 are made of non-magnetic materials, such as aluminum alloy, austenitic stainless steel, and engineering plastics. This avoids interference with the magnetic field of the magnetic ring or the formation of a magnetic short circuit.

[0021] The axial thickness of the magnetic ring 3 can be specially designed according to requirements, so that when the piston 2 moves to the first extreme position on the side of the sensor mounting end cover 4, the mounting base 5 can be completely accommodated within the countersunk hole 41. At this time, by accurately calculating and designing the axial thickness of the magnetic ring 3, and considering the dimensions and assembly relationship of the mounting base 5 and the retaining ring 6, the axial center plane of the magnetic ring 3 is made infinitely close to the theoretical mounting surface inside the displacement sensor electronic head. The theoretical mounting surface is the position plane of the theoretical induced wave on the waveguide. Theoretically, the two can tend to coincide, thereby achieving zero-distance sensing in the mechanical structure and eliminating additional measurement dead zones.

[0022] With the above structure, when the piston 2 reaches the first limit position (for example, when the piston moves to fit against the sensor mounting end cap 4), the mounting base 5 and the magnetic ring 3 are housed in the countersunk hole 41 of the end cap, thereby bypassing the limitation on the axial position of the magnetic ring 3 by the end cap thickness and conventional mounting clearance. This allows the magnetic field center of the magnetic ring 3 to be sensed by the electronic head to the maximum extent, fundamentally eliminating the additional measurement dead zone caused by mechanical structures such as end cap thickness, mounting base size, and assembly clearance. This results in the total measurement dead zone of the system being only the non-eliminable physical minimum dead zone required for sensor electronic processing, greatly improving the effective stroke utilization rate of the hydraulic cylinder.

[0023] Preferably, the mounting base 5 and the countersunk hole 41 are in a clearance fit or a transition fit. The clearance is used to allow hydraulic oil to pass through, achieving lubrication and pressure balance. The outer surface of the mounting base 5 is a smooth surface to reduce movement resistance and wear. When the piston 2 is in the first extreme position, a small gap may be left between the end face of the mounting base 5 and the bottom surface of the countersunk hole 41, or they may be in direct contact as auxiliary mechanical limiting.

[0024] In summary, the addition of the mounting base and its nested fit with the countersunk hole 41 greatly solves the measurement dead zone problem, but may lead to an increase in the axial dimension of the hydraulic cylinder. To balance axial compactness and end cap strength, the countersunk hole size is limited, requiring the magnetic ring 3 to adopt a thin design to accommodate the compact space of the countersunk hole 41 and control the axial dimension of the mounting base 5. Therefore, the thickness of the magnetic ring 3 can be adjusted according to the specific design of the countersunk hole, which is especially suitable for thin hydraulic cylinders that need to ensure the extension stroke and have limited overall axial dimensions. A compact layout of the mounting base 5 is achieved by thinning the magnetic ring 3.

[0025] To compensate for the potential weakening of the radial magnetic field strength due to the thinning of the magnetic ring, the mounting base 5 is provided with a magnetically conductive component 7 for enhancing the radial magnetic field of the magnetic ring 3. The magnetically conductive component 7 includes two magnetically conductive bodies 71, which are respectively disposed in the two radial magnetic pole regions of the magnetic ring 3 and in contact with the radial magnetic pole surface of the magnetic ring 3.

[0026] The magnetic conductor 71 is made of magnetically conductive materials such as low-carbon steel and silicon steel, and its shape matches the radial magnetic pole surface of the magnetic ring 3. The two magnetic conductors 71 are tightly fitted or embedded in corresponding cavities within the mounting base 5, forming a low magnetic resistance path between the inner surface of the magnetic conductor 71 and the N and S pole surfaces of the magnetic ring 3. The two magnetic conductors 71 form a converging magnetic focusing opening on the side near the waveguide 1, which is a roughly C-shaped arc segment in cross-section, enclosing the magnetic ring 3 within an arc range of approximately 120° to 180°. This is used to concentrate and guide the radial magnetic field generated by the magnetic ring 3 to the region where the waveguide 1 is located. The two magnetic conductors 71 are separated by the non-magnetic mounting base 5 body, forming physical and magnetic isolation.

[0027] Preferably, the axial center plane of the magnetic conductor 71 is slightly offset relative to the axial center plane of the magnetic ring 3, towards the theoretical mounting surface. This offset design can more effectively guide and concentrate magnetic field energy towards the theoretical mounting surface, further optimizing the signal strength at the dead zone location.

[0028] The magnetic conductor may have an asymmetrical shape in the axial direction. For example, in the axial direction, the thickness of the end closer to the theoretical mounting surface is greater than the thickness of the end farther from the theoretical mounting surface, forming a slope or wedge structure to more actively guide the magnetic field to the sensor sensing area.

[0029] The working process of this utility model is as follows:

[0030] The piston 2 reciprocates within the cylinder under the drive of hydraulic oil. Whether the piston 2 is in the middle of its stroke or approaching the sensor mounting end cap 4 (as shown in the image), the piston continues to reciprocate. Figure 1 The magnetic rings 3 on the piston generate a radial magnetic field around the waveguide 1. When the sensor's electron head emits a query pulse, the pulse propagates along the waveguide 1. At the location of the magnetic ring 3, the pulse's magnetic field interacts with the static magnetic field of the magnetic ring to generate a torsional stress wave (Weidmann effect). This wave returns to the electron head and is detected. By measuring the time from the pulse's emission to the stress wave's return, the real-time position of the piston 2 can be accurately calculated. Since the dead zone introduced by the mechanical structure is eliminated at the first extreme position, the sensor can detect the piston position almost touching the end cap, greatly expanding the effective measurement range.

[0031] The above are merely preferred embodiments of this utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this utility model, and these improvements and modifications should also be considered within the protection scope of this utility model.

Claims

1. A thin hydraulic cylinder with a displacement sensor, comprising a cylinder body and a displacement sensor disposed at the end of the cylinder, wherein the displacement sensor is a magnetostrictive sensor, comprising a waveguide (1) extending into the cylinder barrel, and a magnetic ring (3) that is mutually induced with the waveguide (1) is disposed on the piston (2) of the cylinder body. Its features are: The cylinder body includes a sensor mounting end cover (4), and the inner side of the sensor mounting end cover (4) is provided with an axially extending countersunk hole (41); the piston (2) is fixedly connected to a mounting base (5) on the side near the sensor mounting end cover (4), and the magnetic ring (3) is embedded in the mounting base (5). The axial thickness of the magnetic ring (3) is such that when the piston (2) moves to the first limit position on the side of the sensor mounting end cap (4), the mounting base (5) can be completely accommodated in the countersunk hole (41), so that the axial center plane of the magnetic ring (3) is infinitely close to the theoretical mounting surface of the displacement sensor electronic head.

2. A thin hydraulic cylinder with a displacement sensor according to claim 1, characterized in that: The mounting base (5) has an axially extending insert groove on the side near the theoretical mounting surface. The magnetic ring (3) is interference-fitted with the insert groove. A retaining ring (6) is installed on the side of the magnetic ring (3) near the theoretical mounting surface.

3. A thin hydraulic cylinder with a displacement sensor according to claim 2, characterized in that: Both the mounting base (5) and the retaining ring (6) are made of non-magnetic materials.

4. A thin hydraulic cylinder with a displacement sensor according to claim 3, characterized in that: The mounting base (5) and the countersunk hole (41) are in clearance fit or transition fit, and the clearance is used to pass hydraulic oil. The outer surface of the mounting base (5) is a smooth surface.

5. A thin hydraulic cylinder with a displacement sensor according to claim 4, characterized in that: When the piston (2) is in the first extreme position, there is a gap or contact between the end face of the mounting base (5) and the bottom surface of the countersunk hole (41).

6. A thin hydraulic cylinder with a displacement sensor according to claim 1, characterized in that: The mounting base (5) is provided with a magnetic guide assembly (7) for enhancing the radial magnetic field of the magnetic ring (3); the magnetic guide assembly (7) includes two magnetic guides (71), which are respectively disposed in the two radial magnetic pole regions of the magnetic ring (3) and in contact with the radial magnetic pole surface of the magnetic ring (3).

7. A thin hydraulic cylinder with a displacement sensor according to claim 6, characterized in that: The axial center plane of the magnetic conductor (71) is offset towards the theoretical mounting surface relative to the axial center plane of the magnetic ring (3).

8. A thin hydraulic cylinder with a displacement sensor according to claim 7, characterized in that: The thickness of the magnetic conductor (71) in the axial direction is greater at the end closest to the theoretical mounting surface than at the end furthest from the theoretical mounting surface.

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