Fluid pressure cylinder

Abstract

A hydraulic cylinder (100) comprises: a magnet (40) that is installed inside a cylinder tube (10) and reciprocates together with a piston rod (20); and a magnetic sensor (50) that detects strokes of the piston rod (20) and a piston (30) using magnetism of the magnet (40). The piston rod (20) has a piston fixing part (22), which has an external thread (22a) formed on an outer circumferential surface and to which the piston (30) is connected, and a tip part (23) formed with a smaller diameter than the piston fixing part (22). The piston (30) is attached to the piston fixing part (22) by screwing an internal thread (35a) of a nut part (35), which is formed in the piston (30) or separately from the piston (30), with the external thread of the piston fixing part (22). The magnet (40) is attached to the tip part (23) of the piston rod (20).

Description

Hydraulic cylinder

[0001] The present invention relates to a hydraulic cylinder.

[0002] CN-U-218765085 discloses a cylinder provided with a magnetic sensor for detecting the magnetism of a magnet attached to a piston via a holder. The magnetic sensor is disposed on the outer peripheral surface of the cylinder tube of the hydraulic cylinder and detects the stroke of the piston. The piston is provided with an extension portion formed to extend coaxially with the piston rod, and a magnet is attached to the outer peripheral surface of the extension portion via a holder. The piston and the holder are fixed by fixing a nut to the tip end portion of the extension portion.

[0003] In the cylinder described in CN-U-218765085, since the nut is fixed to the tip end portion of the extension portion when the piston is attached, a load acts on the magnet provided on the extension portion during attachment. Further, in the cylinder described in CN-U-218765085, when an external force in the extending direction acts on the piston rod in the fully extended state, a compressive load acts on the magnet between the piston and the nut. Thus, in the cylinder described in CN-U-218765085, since a load easily acts on the magnet, there is a problem with the durability of the magnet.

[0004] An object of the present invention is to improve the durability of the magnet.

[0005] According to one aspect of the present invention, a fluid pressure cylinder comprises a cylinder tube, a piston rod reciprocally provided within the cylinder tube, a piston connected to the piston rod and slidably housed within the cylinder tube, a magnet provided within the cylinder tube and reciprocating together with the piston rod, and a magnetic sensor that detects the stroke of the piston rod and the piston by the magnetic field of the magnet, wherein the piston rod has a piston fixing portion to which the piston is connected, with a male thread formed on its outer circumference, and a tip portion formed to be smaller in diameter than the piston fixing portion, the piston is attached to the piston fixing portion by a female thread of a nut portion formed on the piston or separately from the piston screwing into the male thread of the piston fixing portion, and the magnet is attached to the tip portion of the piston rod.

[0006] Figure 1 is a partial cross-sectional view of a fluid pressure cylinder according to an embodiment of the present invention. Figure 2 is an external view of a fluid pressure cylinder according to an embodiment of the present invention. Figure 3 is a perspective view showing the holder attached to the piston rod. Figure 4 is a cross-sectional view of the holder along the line IV-IV shown in Figure 3. Figure 5 is a perspective view of the holder, shown in correspondence with Figure 3.

[0007] A fluid pressure cylinder according to an embodiment of the present invention will be described with reference to the drawings. Below, a hydraulic cylinder 100 in which hydraulic oil is used as the working fluid will be described.

[0008] First, the overall configuration of the hydraulic cylinder 100 will be described with reference to Figures 1 and 2.

[0009] As shown in Figure 1, the hydraulic cylinder 100 includes a cylinder tube 10, a piston rod 20 reciprocally mounted within the cylinder tube 10, a piston 30 connected to the piston rod 20 and slidably housed within the cylinder tube 10, a cylinder head 12 that closes the opening at one end of the cylinder tube 10 and through which the piston rod 20 is inserted, a cylinder bottom 13 that closes the opening at the other end of the cylinder tube 10, a magnet 40 mounted within the cylinder tube 10 and reciprocating together with the piston rod 20, a holder 71 that holds the magnet 40, and a magnetic sensor 50 that detects the stroke of the piston rod 20 and the piston 30 by the magnetic field of the magnet 40. Note that the magnetic sensor 50 is not shown in Figure 1.

[0010] The cylinder tube 10 is formed of a magnetic material made of steel. The cylinder head 12 is fastened to the cylinder tube 10 via, for example, a plurality of fastening members such as bolts (not shown). The cylinder bottom 13 is joined to the cylinder tube 10 by welding, for example. The rod side chamber 2 is partitioned by the cylinder tube 10, the cylinder head 12, and the piston 30, and the opposite rod side chamber 3 is partitioned by the cylinder tube 10, the cylinder bottom 13, and the piston 30. A head side port 11a is formed on the cylinder head 12 side of the cylinder tube 10 as a supply and discharge port that communicates with the rod side chamber 2. Hereafter, the axial direction of the cylinder tube 10 will be simply referred to as the "axial direction," the radial direction of the cylinder tube 10 as the "radial direction," and the circumferential direction of the cylinder tube 10 as the "circumferential direction."

[0011] The cylinder head 12 is formed in an annular shape and slidably supports the piston rod 20. The cylinder bottom 13 has a bottom-side port 13a and a passage 13b which serve as supply and discharge ports communicating with the anti-rod side chamber 3.

[0012] The piston rod 20 has a rod body 21 that is slidably supported by the cylinder head 12, a piston fixing portion 22 on which the piston 30 is provided and fixed to the outer circumference, and a tip portion 23 that is formed to be smaller in diameter than the piston fixing portion 22. In the piston rod 20, the rod body 21, the piston fixing portion 22, and the tip portion 23 are arranged in this order in the axial direction. Steps are formed between adjacent rod bodies 21, piston fixing portions 22, and tip portions 23. In the piston rod 20, the rod body 21 has the largest diameter, and the tip portion 23 has the smallest diameter. A male thread 22a is formed on the outer circumferential surface of the end of the piston fixing portion 22 on the tip portion 23 side. The outer diameter of the male thread 22a (specifically, the bottom of the male thread 22a) is smaller than the outer diameter of the outer circumferential surface 22b on which the male thread 22a is not formed in the piston fixing portion 22, and larger than the outer diameter of the tip portion 23 and the flange portion 23a described later.

[0013] A holder 71 for holding the magnet 40 is attached to the outer circumferential surface of the tip portion 23. In other words, the magnet 40 is attached to the piston rod 20 (tip portion 23) via the holder 71. A flange portion 23a with a larger diameter than the tip portion 23 is formed on the tip portion 23, and the flange portion 23a prevents the holder 71 from coming off. The detailed configuration of the holder 71 will be described later. The magnet 40 is a permanent magnet such as neodymium, and is provided on a part of the circumferential direction of the cylinder tube 10 so as to face the magnetic sensor 50 (see Figure 2) on either side of the cylinder tube 10. Specifically, the magnet 40 is provided in an area smaller than half the circumference of the cylinder tube 10. When the holder 71 is attached to the tip portion 23, the holder 71 and the magnet 40 are provided so as not to contact (be attracted to) the inner circumferential surface of the cylinder tube 10. Therefore, even if the magnet 40 is provided inside the cylinder tube 10 which is made of a magnetic material, the operation of the hydraulic cylinder 100 is not hindered. Even if the magnet 40 is attracted to the inner surface of the cylinder tube 10 by magnetic force, the stroke direction of the piston rod 20 and piston 30 is perpendicular to the lines of force of the magnetic force, so it will have little effect on the stroke of the piston rod 20 and piston 30. For this reason, it is preferable that the magnet 40 is not attracted to the inner surface of the cylinder tube 10, but it is also possible for the magnet 40 to be attracted to the inner surface of the cylinder tube 10.

[0014] The piston 30 is formed in an annular shape. A nut portion 35 is formed on one axial end of the piston 30 (right side in Figure 1), and a female thread 35a is formed on the inner circumferential surface of the nut portion 35. The piston 30 is attached to and connected to the piston rod 20 by screwing the female thread 35a of the nut portion 35 of the piston 30 with the male thread 22a of the piston fixing portion 22 of the piston rod 20. The piston 30 is formed to be shorter in axial length than the piston fixing portion 22, and when the piston 30 is attached to the piston rod 20, a region is formed at the tip of the piston fixing portion 22 where the piston 30 is not provided (see Figure 4). A sealing member 31 is provided on the outer circumferential surface of the piston 30. This blocks communication between the rod-side chamber 2 and the non-rod-side chamber 3 through the space between the inner circumferential surface of the cylinder tube 10 and the outer circumferential surface of the piston 30.

[0015] In such a hydraulic cylinder 100, when hydraulic fluid is supplied from a hydraulic source (working fluid pressure source) to the anti-rod side chamber 3 through the bottom side port 13a and passage 13b, the piston rod 20 and piston 30 move in a direction that reduces the rod side chamber 2, and the hydraulic cylinder 100 extends. At this time, the hydraulic fluid in the rod side chamber 2 is discharged to a tank (not shown) through the head side port 11a.

[0016] Furthermore, when hydraulic fluid is supplied from the hydraulic source to the rod-side chamber 2 through the head-side port 11a, the piston rod 20 and piston 30 move in a direction that reduces the anti-rod-side chamber 3, causing the hydraulic cylinder 100 to contract. At this time, the hydraulic fluid in the anti-rod-side chamber 3 is discharged to the tank through the bottom-side port 13a and passage 13b.

[0017] As shown in Figure 2, the magnetic sensor 50 extends axially along the cylinder tube 10 and is provided on the outer circumferential surface of the cylinder tube 10. The magnetic sensor 50 includes a plurality of Hall elements (not shown) spaced apart in the axial direction, an electronic circuit board (not shown) on which the Hall elements are mounted, and a connector 53. The connector 53 is connected to a processing unit (not shown) that processes the detection results of the Hall elements. The magnetic sensor 50 detects the magnetism of the magnet 40 using the Hall elements and outputs the detection result to the processing unit through the connector 53, thereby detecting the stroke of the piston rod 20 and the piston 30 (for example, displacement from the initial position). The magnetic sensor 50 is attached to the outer circumferential surface of the cylinder tube 10 by a plurality of mounting parts 60 spaced apart in the axial direction, restricting the axial and radial movement of the cylinder tube 10 and preventing rotation.

[0018] Next, we will describe in detail the configuration related to the holder 71.

[0019] Figure 3 is a perspective view showing the holder 71 attached to the tip 23 of the piston rod 20, Figure 4 is a cross-sectional view of the holder 71 along the line IV-IV in Figure 3, and Figure 5 is a perspective view of the holder 71 corresponding to Figure 3. Note that the sealing member 31 provided on the piston 30 is not shown in Figures 3 and 4.

[0020] As shown in Figure 3, the holder 71 has a holder body 41 and a magnet holding portion 70 that is supported by the holder body 41 and holds the magnet 40. The magnet holding portion 70 is formed in a crescent shape. Two magnets 40 are embedded and fixed in the magnet holding portion 70 with an axial gap between them. In this way, the magnets 40 are held in the magnet holding portion 70.

[0021] As shown in Figures 3 to 5, the holder body 41 is formed in a cylindrical shape. The holder body 41 has an insertion hole 42 (see Figures 4 and 5) through which the tip 23 of the piston rod 20 is inserted, large diameter portions 43a and 43b formed at both ends in the axial direction, and a small diameter portion 44 formed between the large diameter portions 43a and 43b. Annular grooves 45a and 45b are formed in each of the large diameter portions 43a and 43b, respectively, which house contaminant seals 80a and 80b as sealing members. In this embodiment, the holder body 41 is formed by joining symmetrical, halved holder pieces 41a and 41b that are divided in the circumferential direction. The holder body 41 is fixed to each other by fastening members (not shown) such as bolts fastened to fastening holes 49 formed across the holder pieces 41a and 41b. As shown in Figure 4, since a region where the piston 30 is not provided is formed at the tip of the piston fixing portion 22, when attaching the holder body 41 to the tip portion 23 of the piston rod 20, the holder body 41 can be attached with an axial gap between it and the piston 30.

[0022] The inner diameter of the insertion hole 42 is formed to be approximately the same as the outer diameter of the tip portion 23 of the piston rod 20 and smaller than the outer diameter of the flange portion 23a. The holder body 41 is fixed by joining the holder pieces 41a and 41b so that the tip portion 23 is inserted into the insertion hole 42. The holder body 41 is attached to the tip portion 23 by restricting the rotation of the holder body 41 with a set screw 88 (see Figure 4), which will be described later. In addition, the flange portion 23a of the tip portion 23 prevents the holder 71 from coming off. The outer diameters of the large diameter portions 43a and 43b are formed to be smaller than the inner circumferential surface of the cylinder tube 10. Therefore, the holder body 41 does not come into contact with the inner circumferential surface of the cylinder tube 10. As shown in Figure 4, the large diameter portion 43a located on the piston fixing portion 22 side (piston 30 side) of the piston rod 20 is formed in a hollow shape having a hollow portion 46. The hollow portion 46 is formed continuously with the insertion hole 42 and is formed coaxially with the insertion hole 42. The inner circumferential surface of the hollow portion 46 is formed to be larger in diameter than the inner circumferential surface of the insertion hole 42, and the nut portion 35 of the piston 30 is housed in the hollow portion 46. Annular claw portions 47a and 47b are formed on the outer circumferential edges of the large-diameter portions 43a and 43b, respectively, projecting axially toward the small-diameter portion 44.

[0023] The small-diameter portion 44 is formed concentrically with the large-diameter portions 43a and 43b. As shown in Figures 4 and 5, a planar notch 44a is formed in the small-diameter portion 44. The bottom surface of the crescent-shaped magnet holder portion 70 contacts the notch 44a. The magnet holder portion 70 is placed on the notch 44a of the holder body 41 and is held by the holder body 41 by the engagement of its outer peripheral surfaces 70a and 70b at both axial ends with the annular claw portions 47a and 47b of the holder body 41. The axial dimensions of the magnet holder portion 70 and the axial dimensions between the large-diameter portions 43a and 43b of the holder body 41 are formed to be approximately the same, and the outer diameters of the outer peripheral surfaces 70a and 70b at both axial ends of the magnet holder portion 70 and the inner diameters of the inner surfaces of the annular claw portions 47a and 47b are formed to be approximately the same. This restricts the relative movement of the magnet holding portion 70 with respect to the holder body 41, thereby positioning the magnet holding portion 70 relative to the holder body 41.

[0024] The annular grooves 45a and 45b are formed on the outer circumferential surfaces of the large-diameter portions 43a and 43b, respectively. In other words, the annular grooves 45a and 45b are provided on both sides of the magnet 40 in the axial direction. The contaminant seals 80a and 80b are made of, for example, fluororesin and are formed in an annular shape. The contaminant seals 80a and 80b are provided on the holder body 41 with a portion of each housed in the annular grooves 45a and 45b, respectively, and slide along the inner circumference of the cylinder tube 10 as shown in Figure 1. This prevents foreign matter such as metal fragments in the hydraulic fluid from being attracted to the magnet 40. Therefore, foreign matter attracted to the magnet 40 will not slide inside the cylinder tube 10, and damage to the cylinder tube 10 is prevented. In addition, one of the annular grooves 45a and the contaminant seal 80a is located radially outward from the nut portion 35 of the piston 30. Therefore, since the contamination seal 80a is provided by utilizing the space radially outside the nut portion 35, it is not necessary to lengthen the piston rod 20 (specifically, the tip portion 23) in the axial direction for the purpose of providing the contamination seal 80a, and the contamination seal 80a can be provided without sacrificing the stroke of the piston rod 20 and the piston 30.

[0025] As shown in Figure 4, the holder pieces 41a and 41b are provided with a set screw 88, which acts as a rotation-retaining member that abuts against the tip 23 of the piston rod 20 and restricts the rotation of the holder body 41 relative to the tip 23, and a screw hole (not shown) through which the set screw 88 is inserted. In Figure 4, the hidden set screw 88 is shown by a dotted line. In this embodiment, one set screw 88 and one screw hole are provided on each of the holder pieces 41a and 41b, and are provided parallel to the dividing surfaces of the holder pieces 41a and 41b, respectively. In other words, the set screw 88 and the screw hole are provided perpendicular to the fastening member. The set screw 88 is screwed into the screw hole and abuts against the tip 23 of the piston rod 20.

[0026] Here, if the piston 30 of the hydraulic cylinder 100 were not provided with a nut portion 35, and the piston 30 and holder 71 were fixed by a nut provided in place of the flange portion 23a of the tip portion 23 of the piston rod 20, then when the nut is tightened, a load will be applied to the tip portion 23 and the magnet 40. Furthermore, in this configuration, if an external force in the extension direction is applied to the piston rod 20 when the piston 30 is in its most extended state and in contact with the cylinder head 12, the piston 30 will be unable to move because it is in contact with the cylinder head 12, and a compressive load will be applied between the piston 30 and the nut. In such a configuration of the hydraulic cylinder 100, a load is easily applied to the magnet 40, which poses a problem for the durability of the magnet 40.

[0027] In contrast, in the hydraulic cylinder 100 of this embodiment, the male thread of the piston fixing portion 22 of the piston rod 20 and the female thread of the nut portion 35 of the piston 30 are screwed together, and the magnet 40 is attached to the tip portion 23 of the piston rod 20. Therefore, when the piston rod 20 and the piston 30 are connected, a load is applied to the rod body 21 and the piston fixing portion 22 of the piston rod 20 when the nut portion 35 is tightened, but no load is applied to the tip portion 23, and no load is applied to the magnet 40. Furthermore, in the hydraulic cylinder 100 of this embodiment, a nut is not provided on the tip portion 23 of the piston rod 20, and only a flange portion 23a with a smaller diameter than a nut is formed to prevent the holder 71 from falling off. Therefore, even if an external force in the extension direction is applied to the piston rod 20 in the fully extended state, a compressive load is unlikely to be applied to the magnet 40. The magnet 40 is attached to the tip 23 of the piston rod 20 via the holder 71, and is positioned radially outward compared to when it is directly attached to the tip 23. Therefore, the above-mentioned compressive load is less likely to act on the magnet 40. Thus, the durability of the magnet 40 can be improved.

[0028] Furthermore, in the hydraulic cylinder 100 of this embodiment, an axial gap is formed between the piston 30 and the holder 71, so that even when the piston 30 is subjected to a load, the load is not transmitted to the holder 71.

[0029] Furthermore, in the hydraulic cylinder 100 of this embodiment, the female thread of the nut portion 35 of the piston 30 is screwed onto the male thread of the piston fixing portion 22 of the piston rod 20. This allows the female thread of the nut portion 35 to be screwed onto a larger diameter portion of the rod than would be possible if it were screwed onto the tip portion 23 of the piston rod 20.

[0030] According to the above embodiment, the following effects and advantages are achieved.

[0031] In the hydraulic cylinder 100, the male thread of the piston fixing portion 22 of the piston rod 20 and the female thread of the nut portion 35 of the piston 30 are screwed together, and the magnet 40 is attached to the tip portion 23 of the piston rod 20. Therefore, no load is applied to the magnet 40 when the piston rod 20 and the piston 30 are connected, and even if an external force in the extension direction is applied to the piston rod 20 in the fully extended state, a compressive load is unlikely to be applied to the magnet 40. Thus, the durability of the magnet 40 can be improved.

[0032] Next, modifications of this embodiment will be described. The following modifications are also within the scope of the present invention, and it is possible to combine the configurations shown in the modifications with the configurations described in the above embodiments, or to combine the configurations described in the following different modifications.

[0033] <Modification 1> In the above embodiment, the hydraulic cylinder 100 includes a holder 71 attached to the tip 23 of the piston rod 20 to hold the magnet 40. However, the hydraulic cylinder 100 is not limited to the above configuration as long as the magnet 40 is attached to the tip 23 and reciprocates together with the piston rod 20. In other words, the holder 71 is not an essential component, and the magnet 40 may be directly attached to the tip 23 of the piston rod 20. Also, the contamination seal 80 provided on the holder body 41 to protect the magnet 40 is not an essential component. Even with this configuration, the same effects as in the above embodiment can be achieved.

[0034] <Modification 2> In the above embodiment, the holder body 41 is formed by joining together symmetrical, halved holder pieces 41a and 41b that are divided in the circumferential direction. However, the holder body 41 may be formed without being divided in the circumferential direction.

[0035] <Modification 3> In the above embodiment, one of the contaminant seals 80 (contaminant seal 80a) in the holder body 41 is located radially outside the nut portion 35 of the piston 30. This eliminates the need to lengthen the piston rod 20 axially for the sake of the contaminant seal 80a, and allows the contaminant seal 80a to be provided without sacrificing the stroke of the piston rod 20 and the piston 30. However, in cases where the stroke of the piston rod 20 and the piston 30 can be short, the contaminant seal 80a does not need to be located radially outside the nut portion 35 of the piston 30.

[0036] <Modification 4> In the above embodiment, a nut portion 35 is formed on the piston 30, and the piston 30 is attached to the piston rod 20 by screwing the female thread 35a of the nut portion 35 of the piston 30 with the male thread 22a of the piston fixing portion 22 of the piston rod 20. However, the nut portion 35 may not be formed on the piston 30, and a separate nut (a separate component) may be provided at the tip of the piston 30 as the nut portion 35. Even in this configuration, the piston 30 is attached to the piston fixing portion 22 by screwing the female thread 35a of the nut portion 35 with the male thread 22a of the piston fixing portion 22.

[0037] The configuration, operation, and effects of the embodiment of the present invention configured as described above will be summarized below.

[0038] The hydraulic cylinder 100, as a fluid pressure cylinder, comprises a cylinder tube 10, a piston rod 20 reciprocally mounted within the cylinder tube 10, a piston 30 connected to the piston rod 20 and slidably housed within the cylinder tube 10, a magnet 40 mounted within the cylinder tube 10 and reciprocating together with the piston rod 20, and a magnetic sensor 50 that detects the stroke of the piston rod 20 and the piston 30 by the magnetic field of the magnet 40. The piston rod 20 has a piston fixing portion 22 to which the piston 30 is connected, with a male thread 22a formed on its outer circumference, and a tip portion 23 formed to be smaller in diameter than the piston fixing portion 22. The piston 30 is attached to the piston fixing portion 22 by the female thread 35a of a nut portion 35, which is formed on or separately from the piston 30, screwing into the male thread of the piston fixing portion 22, and the magnet 40 is attached to the tip portion 23 of the piston rod 20.

[0039] In this configuration, the piston 30 is attached to the piston fixing portion 22 of the piston rod 20 by screwing together the male thread 22a of the piston fixing portion 22 of the piston rod 20 and the female thread 35a of the nut portion 35 of the piston 30, and the magnet 40 is attached to the tip portion 23 of the piston rod 20. Therefore, no load is applied to the magnet 40 when the piston rod 20 and the piston 30 are connected, and even if an external force in the extension direction is applied to the piston rod 20 in the fully extended state, a compressive load is unlikely to be applied to the magnet 40. Thus, the durability of the magnet 40 can be improved.

[0040] Furthermore, the hydraulic cylinder 100 is further equipped with a holder 71 attached to the tip 23 of the piston rod 20 to hold the magnet 40, and the holder 71 is provided with a pair of contaminant seals 80 as sealing members, which are provided on both sides of the magnet 40 in the axial direction of the cylinder tube 10 and slide along the inner circumference of the cylinder tube 10.

[0041] In this configuration, foreign matter in the working fluid is prevented from being attracted to the magnet 40.

[0042] Further, in the hydraulic cylinder 100, in the holder 71, one side (contamination seal 80a) of the contamination seal 80 is located radially outside the nut portion 35.

[0043] In this configuration, since the contamination seal 80a is provided by using the space radially outside the nut portion 35, it is not necessary to lengthen the piston rod 20 axially for the contamination seal 80a, and the contamination seal 80a can be provided without sacrificing the stroke of the piston rod 20 and the piston 30.

[0044] As described above, the embodiments of the present invention have been described. However, the above embodiments merely show a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

[0045] This application claims priority based on Japanese Patent Application No. 2024-168829 filed with the Japan Patent Office on September 27, 2024, and the entire contents of this application are incorporated herein by reference.

Claims

1. A fluid pressure cylinder comprising: a cylinder tube; a piston rod reciprocally mounted within the cylinder tube; a piston connected to the piston rod and slidably housed within the cylinder tube; a magnet mounted within the cylinder tube and reciprocating together with the piston rod; and a magnetic sensor that detects the stroke of the piston rod and the piston by the magnetic field of the magnet, wherein the piston rod has a piston fixing portion to which the piston is connected, with a male thread formed on its outer circumference; and a tip portion formed to be smaller in diameter than the piston fixing portion; the piston is attached to the piston fixing portion by a female thread of a nut portion formed on the piston or separately from the piston engaging with the male thread of the piston fixing portion; and the magnet is attached to the tip portion of the piston rod.

2. A fluid pressure cylinder according to claim 1, further comprising a holder attached to the tip of the piston rod for holding the magnet, wherein the holder is provided with a pair of sealing members provided on both sides of the magnet in the axial direction of the cylinder tube and sliding along the inner circumference of the cylinder tube.

3. A fluid pressure cylinder according to claim 2, wherein in the holder, one of the sealing members is located radially outward of the nut portion.

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