Fluid pressure cylinder

Abstract

A hydraulic cylinder (100) is provided with: a cylinder tube (10); a piston rod (20); a piston member (30); a rod internal passage (50) provided in the piston rod (20), one opening portion (51) opening in the cylinder tube (10) at an outer peripheral surface of the piston rod (20), the other opening portion (52) opening outside the cylinder tube (10); a pressure sensor (60) provided outside the cylinder tube (10) and detecting a case where a working fluid is guided to the rod internal passage (50), the piston member (30) being connected to the piston rod (20) in a state where one end surface is in contact with an annular step portion (23) provided at the outer peripheral surface of the piston rod (20) and blocks the one opening portion (51) of the rod internal passage (50), the pressure sensor (60) detecting a case where the working fluid is guided to the rod internal passage (50) from a fluid pressure chamber via the step portion (23) and the piston member (30).

Description

Technical Field

[0001] This invention relates to a fluid pressure cylinder. Background Technology

[0002] Japanese Patent Application Publication No. JP2004-263713A discloses a fluid pressure cylinder having a cylinder body in which a piston is installed in a free reciprocating motion, and a piston rod mounted on the piston and protruding outward from the end of the cylinder body. The piston is threadedly engaged with the end of the piston rod and is mounted on the piston rod. Summary of the Invention

[0003] In the fluid pressure cylinder described in Japanese Patent Application Publication JP2004-263713A, when an excessive load is applied to the piston, the piston may become loose relative to the piston rod. When this loosening of the piston relative to the piston rod worsens, the fluid pressure cylinder malfunctions. In the fluid pressure cylinder described in Japanese Patent Application Publication JP2004-263713A, the operator is unlikely to notice the piston loosening until the fluid pressure cylinder malfunctions.

[0004] The purpose of this invention is to prevent malfunction of the fluid pressure cylinder caused by loosening of the piston components.

[0005] According to one aspect of the present invention, a fluid pressure cylinder comprises: a cylinder barrel; a piston rod inserted into the cylinder barrel in a freely reciprocating manner; a piston component connected to the top end of the piston rod and dividing a fluid pressure chamber within the cylinder barrel; a rod internal passage disposed within the piston rod, one opening of which is located within the cylinder barrel and opens onto the outer circumferential surface of the piston rod, and the other opening of which is located outside the cylinder barrel; and a detection unit disposed outside the cylinder barrel for detecting when working fluid is guided into the rod internal passage. The piston component is connected to the piston rod in a state where one end face contacts an annular step portion disposed on the outer circumferential surface of the piston rod and blocks the one opening of the rod internal passage. The detection unit detects when working fluid is guided from the fluid pressure chamber through the step portion and the piston component into the rod internal passage. Attached Figure Description

[0006] Figure 1 This is a partial cross-sectional view of the fluid pressure cylinder according to an embodiment of the present invention.

[0007] Figure 2 This is a partial cross-sectional view of a fluid pressure cylinder according to an embodiment of the present invention, showing the piston assembly in a relaxed state relative to the piston rod.

[0008] Figure 3This is a partial cross-sectional view of a fluid pressure cylinder according to a modified example 2 of the present invention. Detailed Implementation

[0009] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0010] Reference Figure 1 The fluid pressure cylinder according to the embodiments of the present invention will be described below. Hereinafter, the case of a hydraulic cylinder 100 in which the working fluid is used as the working fluid will be described.

[0011] The hydraulic cylinder 100 is used as an actuator mounted on construction machinery and industrial machinery. For example, the hydraulic cylinder 100 is used as an actuator to drive the boom, stick, bucket, etc. mounted on a hydraulic excavator.

[0012] like Figure 1 As shown, the hydraulic cylinder 100 includes: a cylindrical cylinder 10; a piston rod 20 inserted into the cylinder 10 in a freely reciprocating manner; a piston assembly 30 connected to the top end of the piston rod 20, which divides the cylinder 10 into a rod-side chamber 11 and a rod-opposite-side chamber 12 serving as fluid pressure chambers; and a cylinder head 40 that closes the open end of the cylinder 10. The hydraulic cylinder 100 performs axial extension and retraction by supplying working fluid from a hydraulic source to one of the rod-side chambers 11 and 12 and discharging working fluid from the fluid tank in the other direction. Alternatively, a water-soluble alternative fluid, such as a water-soluble substitute, can be used as the working fluid to replace oil.

[0013] The piston rod 20 has: a small-diameter portion 21 formed at the top end and connected to the piston component 30; and a large-diameter portion 22, the outer diameter of which is larger than that of the small-diameter portion 21 and supported by the cylinder head 40 for free sliding. An annular surface, i.e., a stepped portion 23, perpendicular to the axial direction of the piston rod 20 is provided between the small-diameter portion 21 and the large-diameter portion 22. Furthermore, the piston rod 20 has a curved surface portion 24 recessed into the small-diameter portion 21 at the boundary with the stepped portion 23, forming an annular shape. The curved surface portion 24 is recessed radially inward of the small-diameter portion 21. The curved surface portion 24 alleviates stress concentration at the boundary between the small-diameter portion 21 and the stepped portion 23. A male threaded portion 21a, threadedly engaging with the piston component 30, is provided in a portion of the small-diameter portion 21. Additionally, the large-diameter portion 22 extends from the open end of the cylinder 10, and a mounting portion 22a for mounting to other equipment is provided at its end. Mounting part 22a is mounted to the end of large-diameter part 22, for example, by welding. Additionally, mounting part 22a is also part of piston rod 20.

[0014] An internal passage 50 is provided within the piston rod 20, extending axially. One opening 51 of the internal passage 50 opens onto the outer peripheral surface of the small-diameter portion 21 within the cylinder 10, while the other opening 52 opens onto the outside of the cylinder 10. Specifically, the opening 51 is located near the stepped portion 23, between the stepped portion 23 and the male threaded portion 21a. The opening 52 is located on the outer peripheral surface of the mounting portion 22a. Thus, even in the most retracted state of the hydraulic cylinder 100, the opening 52 remains outside the cylinder 10.

[0015] The rod internal passage 50 is machined before the mounting portion 22a is installed at the end of the piston rod 20. Specifically, it is formed by cutting along the axial direction of the piston rod 20 from the end of the piston rod 20 and cutting from the outer peripheral surface of the mounting portion 22a toward the center of the mounting surface on which the piston rod 20 is mounted.

[0016] The hydraulic cylinder 100 includes a pressure sensor 60 as a detection unit. This pressure sensor 60 is located outside the cylinder barrel 10 and detects when working fluid is guided into the rod internal passage 50. The pressure sensor 60 is mounted on the mounting portion 22a via a connector 80. A passage 81 is formed on the connector 80, communicating with the rod internal passage 50 and guiding working fluid from the rod internal passage 50 to the pressure sensor 60. The pressure sensor 60 detects when working fluid is guided from the opening 51 into the rod internal passage 50 and wirelessly transmits this detection signal as an electrical signal to an external device (not shown).

[0017] The piston component 30 includes: a piston body portion 31 that slides along the inner circumferential surface of the cylinder 10; and a ring component 32 disposed between the piston body portion 31 and the stepped portion 23 of the piston rod 20. The piston body portion 31 and the ring component 32 are formed of the same material. The ring component 32 has a smaller outer diameter than the piston body portion 31. The ring component 32 is in surface contact with the piston body portion 31, and working fluid is not guided between the piston body portion 31 and the ring component 32. A portion of the inner circumferential surface of the piston body portion 31 is provided with a female thread portion 31a that is threaded into the male thread portion 21a of the piston rod 20. The female thread portion 31a is screwed into the male thread portion 21a of the piston rod 20 until the ring component 32 contacts the stepped portion 23. Thus, the piston component 30 is connected to the piston rod 20 with one end face 33 in contact with the stepped portion 23 of the piston rod 20. As described above, the opening 51 of the rod internal passage 50 is located between the stepped portion 23 and the male threaded portion 21a. Therefore, when the piston component 30 is connected to the piston rod 20, the ring component 32 of the piston component 30 contacts the stepped portion 23 and covers the opening 51 of the rod internal passage 50, thereby blocking the flow of working fluid from the rod-side chamber 11 to the rod internal passage 50. In this way, the ring component 32 blocks the opening 51.

[0018] Furthermore, the ring member 32 has a tapered portion 32a disposed on the inner circumferential surface of the ring member 32, facing the curved portion 24 of the piston rod 20, and whose inner diameter increases toward the end face 33. The tapered portion 32a is formed in a ring shape on the inner circumferential surface of the ring member 32, extending to the end face 33. The tapered portion 32a prevents contact between the ring member 32 and the curved portion 24 of the piston rod 20. This ensures contact between the piston member 30 and the curved portion 24 of the piston rod 20.

[0019] The hydraulic cylinder 100 includes an annular O-ring 70 as a sealing member, which is compressively disposed between the piston member 30 and the piston rod 20 to seal the two. An annular groove 31b for receiving the O-ring 70 is formed on the inner circumferential surface of the piston body 31. The annular groove 31b is formed by opening through the ring member 32 on the end face of the piston body 31 opposite to the stepped portion 23. That is, the annular groove 31b is formed by opening on the end face of the piston body 31 that contacts the ring member 32. Therefore, the O-ring 70 can be easily received in the annular groove 31b during assembly.

[0020] The cylinder head 40 is a generally cylindrical component through which the piston rod 20 is inserted. The cylinder head 40 has a flange 41, which is threaded to the end of the cylinder barrel 10 by screws (not shown). Alternatively, the flange 41 can be fastened to the end face of the cylinder barrel 10 by bolts (not shown). The cylinder head 40 is provided with a supply / discharge port 42 for supplying and discharging working fluid to the rod-side chamber 11. One end of the supply / discharge port 42 faces the outer peripheral surface of the piston rod 20 and communicates with the rod-side chamber 11 through an annular gap between the outer peripheral surface of the piston rod 20 and the inner peripheral surface of the cylinder head 40. The other end of the supply / discharge port 42 is open on the outer peripheral surface of the cylinder head 40. A hydraulic hose (not shown) is connected to the other end of the supply / discharge port 42, and the hydraulic hose is connected to a hydraulic power source or fluid tank via a switching valve.

[0021] Here, in the hydraulic cylinder 100, when an excessive load is applied to the piston component 30, the piston component 30 may become loose relative to the piston rod 20 (hereinafter, also referred to as "loosening of the piston component 30"). When the loosening of the piston component 30 intensifies, the hydraulic cylinder 100 malfunctions. Specifically, when a load exceeding the axial force in the connection between the piston component 30 and the piston rod 20 is applied to the piston component 30, the piston rod 20 extends axially while the threaded engagement between the female thread portion 31a of the piston component 30 and the male thread portion 21a of the piston rod 20 is maintained. When the piston rod 20 extends axially, the stepped portion 23 of the piston rod 20, which bears the axial force in the connection between the piston component 30 and the piston rod 20, separates from the end face 33 of the piston component 30. As a result, the axial force acting on the piston component 30 decreases, and the threaded engagement between the female thread portion 31a of the piston component 30 and the male thread portion 21a of the piston rod 20 loosens. In a typical hydraulic cylinder, the operator may not notice the piston loosening until the piston components become increasingly loose and the cylinder malfunctions.

[0022] In this regard, in the hydraulic cylinder 100, the slack in the piston component 30 can be detected early by the pressure sensor 60 before the hydraulic cylinder 100 malfunctions. See below for reference. Figure 1 , Figure 2 The detection of slack in piston component 30 by pressure sensor 60 will be described in detail.

[0023] With the piston assembly 30 connected to the piston rod 20, as described above, the ring assembly 32 contacts the stepped portion 23 of the piston rod 20, thereby blocking the flow of working fluid from the rod-side chamber 11 connecting the two to the rod internal passage 50. Furthermore, the threaded connection between the female threaded portion 31a of the piston body 31 and the male threaded portion 21a of the piston rod 20, along with the O-ring 70, also blocks the flow of working fluid from the rod-opposite chamber 12 connecting the inner circumferential surface of the piston assembly 30 and the outer circumferential surface of the small-diameter portion 21 of the piston rod 20 to the rod internal passage 50. Additionally, the O-ring 70 also blocks the flow of working fluid from the rod-side chamber 11 connecting the piston body 31 and the ring assembly 32 to the rod internal passage 50. Therefore, working fluid is not guided from the rod-side chamber 11 and the rod-opposite chamber 12 to the rod internal passage 50.

[0024] like Figure 2As shown, when the piston component 30 relaxes relative to the piston rod 20, the ring component 32 and the step portion 23 separate, creating a gap between them. This allows the working fluid to be guided from the rod-side chamber 11 through the gap between the ring component 32 and the step portion 23 into the rod internal passage 50. Furthermore, the guidance of the working fluid into the rod internal passage 50 is detected by the pressure sensor 60. Therefore, the relaxation of the piston component 30 can be detected by the pressure sensor 60. Thus, the relaxation of the piston component 30 can be detected in its initial stage, preventing malfunctions of the hydraulic cylinder 100 caused by the relaxation of the piston component 30.

[0025] Furthermore, in the hydraulic cylinder 100, the O-ring 70 is provided on the side opposite to the stepped portion 23 of the piston rod 20, with the opening 51 of the rod inner passage 50 as its boundary. Thus, the communication between the rod-side chamber 11 and the opposite-side chamber 12, which connects the inner circumferential surface of the piston component 30 and the outer circumferential surface of the small-diameter portion 21 of the piston rod 20, is blocked by the O-ring 70. Consequently, when a gap is created between the ring component 32 and the stepped portion 23 of the piston component 30, the working fluid flowing from the rod-side chamber 11 into this gap is not guided to the opposite-side chamber 12, but is guided towards the rod inner passage 50. This improves the detection accuracy of piston component 30 relaxation implemented by the pressure sensor 60. Although the detection accuracy of piston component 30 relaxation is reduced, the annular groove 31b and the O-ring 70 are not necessarily required and are not essential structures of the present invention.

[0026] Furthermore, in the hydraulic cylinder 100, as described above, the annular groove 31b of the piston body portion 31 of the piston component 30 is formed by opening on the end face opposite to the stepped portion 23 of the piston rod 20. Therefore, assuming a structure in which the end face of the piston body portion 31 contacts the stepped portion 23 of the piston rod 20, the contact area between the piston component 30 and the stepped portion 23 is small, thus reducing the sealing performance between them. However, in the hydraulic cylinder 100, an annular component 32 is provided between the piston body portion 31 and the stepped portion 23 of the piston rod 20, and the annular component 32 contacts the stepped portion 23. Therefore, the contact area between the piston component 30 and the stepped portion 23 is ensured, further blocking the flow of working fluid toward the rod passage 50 that connects the two. As a result, the detection accuracy of the slack of the piston component 30 implemented by the pressure sensor 60 is improved.

[0027] Furthermore, the contact surface between the piston component 30 and the stepped portion 23 of the piston rod 20 is the surface that bears the axial force generated by the threaded fastening when the piston component 30 and the piston rod 20 are connected. Since the contact area between the piston component 30 and the stepped portion 23 is ensured by the ring component 32 in the hydraulic cylinder 100, the fastening force of the piston component 30 relative to the piston rod 20 can be ensured.

[0028] In the hydraulic cylinder 100, as described above, the pressure sensor 60 detects that the working fluid is guided from the rod-side chamber 11 to the rod internal passage 50, and this detection signal is wirelessly transmitted as an electrical signal to an external device (not shown). Therefore, even when the construction or industrial machinery on which the hydraulic cylinder 100 is mounted is remotely operated by an operator via a terminal or similar device, the operator can confirm the slack of the piston component 30 by transmitting detection information, such as that obtained by the pressure sensor 60, to the terminal or similar device. Alternatively, the detection signal can be transmitted to the external device via a wired connection.

[0029] According to the above implementation method, the following effects are achieved.

[0030] In the hydraulic cylinder 100, when the piston component 30 is relaxed relative to the piston rod 20, the working fluid is guided from the rod-side chamber 11 through the gap between the ring component 32 and the step portion 23 to the rod internal passage 50, and detected by the pressure sensor 60. Therefore, the relaxation of the piston component 30 can be detected by the pressure sensor 60, and malfunction of the hydraulic cylinder 100 caused by the relaxation of the piston component 30 can be prevented.

[0031] Furthermore, in the hydraulic cylinder 100, the communication between the rod-side chamber 11, which connects the inner circumferential surface of the piston component 30 and the outer circumferential surface of the small-diameter portion 21 of the piston rod 20, and the opposite-side chamber 12 is blocked by the O-ring 70. This allows the working fluid flowing into the piston component 30 to be guided into the rod internal passage 50 when the piston component 30 relaxes and a gap is created between the ring component 32 and the step portion 23. This improves the detection accuracy of the relaxation of the piston component 30 as implemented by the pressure sensor 60.

[0032] Furthermore, in the hydraulic cylinder 100, the ring member 32 contacts the step portion 23, thus ensuring the contact area between the piston member 30 and the step portion 23. Therefore, in a state where there is no gap between the piston member 30 and the step portion 23, the flow of working fluid through the rod internal passage 50 between them can be further blocked. This improves the detection accuracy of the slack in the piston member 30 implemented by the pressure sensor 60.

[0033] Furthermore, in the hydraulic cylinder 100, even when the construction machinery or industrial machinery on which the hydraulic cylinder 100 is mounted is remotely operated by an operator via a terminal or the like, the operator can confirm the loosening of the piston component 30 by sending detection information of the slack of the piston component 30 obtained by, for example, the pressure sensor 60 to the terminal or the like.

[0034] Next, variations of the above embodiments will be described. The following variations are also within the scope of the present invention, and it is possible to combine the structures shown in the variations with the structures described in the above embodiments, or to combine the structures described in the following different variations with each other.

[0035] <Variation Example 1>

[0036] In the above embodiment, the detection unit for detecting the flow of working fluid into the rod internal passage 50 is described as a pressure sensor 60. However, this is not a limitation; the detection unit can also be a sensor 160 such as an image sensor or a volume sensor. Specifically, a component that changes color in response to the working fluid, a component that changes shape due to reaction with the working fluid or hydraulic pressure, and a container for storing the working fluid are provided facing the opening 52 of the rod internal passage 50. The sensor 160 observes the color change, shape change, and the amount of working fluid in the container of these components to detect the flow of working fluid into the rod internal passage 50. In this structure, the flow of working fluid into the rod internal passage 50 can be detected by using a sensor 160 other than a pressure sensor, such as an image sensor or a volume sensor. Alternatively, the operator can visually observe the color change, shape change, and the amount of working fluid in the container without using the sensor 160 to confirm the loosening of the piston component 30. In this case, the component or container itself, which is positioned to face the opening 52 of the inner passage 50 of the rod, becomes the detection unit.

[0037] <Variation Example 2>

[0038] In the above embodiment, a ring member 32 is provided between the piston body portion 31 and the stepped portion 23 of the piston rod 20. The ring member 32 contacts the stepped portion 23, thereby blocking the flow of working fluid from the rod-side chamber 11 connecting the two to the rod internal passage 50. However, this is not a limitation; for example... Figure 3 As shown, the ring member 32 may be omitted, and the piston member 30 may be formed solely by the piston body portion 31. Even with this structure, as in the above embodiment, it is possible to prevent malfunction of the hydraulic cylinder 100 caused by loosening of the piston member 30. Even in this configuration, the O-ring 70 is provided on the side opposite to the stepped portion 23 of the piston rod 20, with the opening 51 of the rod inner passage 50 as its boundary, just as in the above embodiment. However, the annular groove 31b for receiving the O-ring 70 is not formed by opening on the end face of the piston body portion 31. Therefore, it is difficult to receive the O-ring 70 in the annular groove 31b. In contrast, in the above embodiment, the ring member 32 is provided, and the annular groove 31b opens on the end face of the piston body portion 31, thus making it easy to receive the O-ring 70 in the annular groove 31b.

[0039] The structure, function, and effects of the embodiments of the present invention are summarized and explained below.

[0040] The hydraulic cylinder 100, serving as a fluid pressure cylinder, includes: a cylinder barrel 10; a piston rod 20 inserted into the cylinder barrel 10 in a freely reciprocating manner; a piston component 30 connected to the top end of the piston rod 20, and dividing the cylinder barrel 10 into a rod-side chamber 11 and a rod-opposite-side chamber 12 serving as fluid pressure chambers; a rod internal passage 50 disposed within the piston rod 20, with one opening 51 opening inside the cylinder barrel 10 on the outer peripheral surface of the piston rod 20, and the other opening 52 opening outside the cylinder barrel 10; and detection units 60 and 1. The detection units 60 and 160 are located outside the cylinder 10 and detect when the working fluid is guided to the rod internal passage 50. The piston component 30 is connected to the piston rod 20 in a state where one end face 33 contacts the annular step portion 23 provided on the outer peripheral surface of the piston rod 20 and blocks one opening 51 of the rod internal passage 50. The detection units 60 and 160 detect when the working fluid is guided from the rod side chamber 11 and the opposite side chamber 12 of the rod through the step portion 23 and the piston component 30 to the rod internal passage 50.

[0041] In this structure, with the piston component 30 and piston rod 20 in the connected state, one end face 33 of the piston component 30 contacts the step portion 23 of the piston rod 20, thereby blocking the flow of working fluid from the rod-side chamber 11 and the opposite-side chamber 12 to the rod internal passage 50. When the piston component 30 relaxes relative to the piston rod 20, the working fluid is guided to the rod internal passage 50 through the gap between the end face 33 of the piston component 30 and the step portion 23 of the piston rod 20, and is detected by the detection units 60 and 160. Therefore, the relaxation of the piston component 30 relative to the piston rod 20 can be detected by the detection units 60 and 160.

[0042] In addition, the hydraulic cylinder 100 also has an annular O-ring 70 as a sealing component. The O-ring 70 is compressedly disposed between the piston component 30 and the piston rod 20. The O-ring 70 is disposed on the side opposite to the step portion 23 with the opening 51 of one side of the rod passage 50 as the boundary.

[0043] In this structure, the O-ring 70 blocks the communication between the rod-side chamber 11 and the opposite-side chamber 12 that connect the piston component 30 and the piston rod 20. Therefore, when the piston component 30 relaxes relative to the piston rod 20, creating a gap between the piston component 30 and the step portion 23 of the piston rod 20, the working fluid flowing into this gap is easily guided into the rod passage 50. This improves the detection accuracy of the relaxation of the piston component 30 performed by the detection units 60 and 160.

[0044] Additionally, the piston component 30 includes: a piston body portion 31 that slides along the inner circumferential surface of the cylinder 10; and a ring component 32 disposed between the piston body portion 31 and the stepped portion 23 of the piston rod 20, blocking one of the openings 51 of the rod internal passage 50. The piston body portion 31 has an annular groove 31b formed on its inner circumferential surface and is formed by opening on the end face opposite to the stepped portion 23 of the piston rod 20 through the ring component 32. The annular groove 31b accommodates an O-ring 70.

[0045] In this structure, the annular groove 31b for receiving the O-ring 70 is formed by opening on the end face of the piston body 31 opposite to the stepped portion 23 of the piston rod 20. However, since a ring member 32 is provided between the piston body 31 and the stepped portion 23 of the piston rod 20, and the ring member 32 contacts the stepped portion 23, the contact area between the piston member 30 and the stepped portion 23 of the piston rod 20 is ensured.

[0046] In addition, the piston rod 20 has: a small diameter portion 21 formed on the top side compared to the stepped portion 23; a curved portion 24 disposed in the boundary portion of the small diameter portion 21 with the stepped portion 23 and recessed into an annular shape; and the piston component 30 has a tapered portion 32a disposed on the inner circumferential surface of the piston component 30 in a manner opposite to the curved portion 24, and whose inner diameter increases towards one end face 33.

[0047] In this structure, the curved portion 24 of the piston rod 20 suppresses stress concentration at the boundary between the small diameter portion 21 and the stepped portion 23. Furthermore, the tapered portion 32a of the piston component 30 prevents contact between the piston component 30 and the curved portion 24 of the piston rod 20, thus ensuring contact between the piston component 30 and the stepped portion 23 of the piston rod 20.

[0048] While the above description illustrates this embodiment, it is merely a partial example of the application of the present invention and is not intended to limit the technical scope of the present invention to the specific structure of the above embodiment.

[0049] This application claims priority based on Japanese Patent Application No. 2021-123341 filed with the Japan Patent Office on July 28, 2021, the entire contents of which are incorporated herein by reference.

Claims

1. A fluid pressure cylinder, wherein, have: Cylinder; A piston rod is inserted into the cylinder in a manner that allows for free reciprocating movement; A piston assembly, which is connected to the top end of the piston rod and divides the cylinder into a fluid pressure chamber; An internal passage is provided inside the piston rod, with one opening inside the cylinder and opening on the outer circumferential surface of the piston rod, and the other opening opening outside the cylinder. A detection unit, located outside the cylinder, detects whether the working fluid is guided into the internal passage of the rod. The piston component is connected to the piston rod in a state where one end face contacts the annular stepped portion provided on the outer peripheral surface of the piston rod, thereby blocking the opening of one side of the passage within the rod. The detection unit detects the working fluid being guided from the fluid pressure chamber through the step portion and the piston component into the rod internal passage.

2. The fluid pressure cylinder as described in claim 1, wherein, It also includes an annular sealing component, which is compressively disposed between the piston component and the piston rod. The sealing component is positioned on the opposite side of the stepped portion, with the opening of one of the passageways in the rod serving as the boundary.

3. The fluid pressure cylinder as described in claim 2, wherein, The piston component has: The piston body slides along the inner circumferential surface of the cylinder. A ring component is disposed between the piston body and the stepped portion of the piston rod, and blocks one opening of the passage within the rod. The piston body has an annular groove formed on its inner circumferential surface and is formed by opening on the end face opposite the stepped portion of the piston rod, with the annular member in between, and the annular groove accommodates the sealing member.

4. The fluid pressure cylinder as described in claim 1, wherein, The piston rod has: The smaller diameter portion is formed on the top side compared to the stepped portion; The curved surface is located at the boundary between the small diameter portion and the stepped portion, and is recessed into a ring shape. The piston component has a tapered portion disposed on the inner circumferential surface of the piston component in a manner opposite to the curved portion, and the inner diameter increases toward one of the end faces.

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