Cylinder device

Abstract

Cylinder device comprising: a first cylinder (5) containing hydraulic fluid in a sealing manner; a first piston (6) slidably fitted into the first cylinder (5) and defining an inner surface of this first cylinder (5) into a rod-side chamber (C) and a bottom-side chamber (B); an oil passage (6A) provided on the first piston (6) and configured to establish a connection between the rod-side chamber (C) and the bottom-side chamber (B); a poppet valve (6D) configured to suppress movement of the hydraulic fluid flowing in the oil passage (6A) in order to generate a damping force; a piston rod (7) coupled to the first piston (6); a closing element (9) provided at an end face of the first cylinder (5) and configured to close the first cylinder (5) with the piston rod (7) inserted through it; and a stopper mechanism (11) configured toto operate when the piston rod (7) extends and moves towards an end section within the first cylinder (5), wherein the stopper mechanism (11) comprises a second cylinder (12) which is movably provided relative to the piston rod (7), the second cylinder (12) having a bottom section (12A) on one end side of the first cylinder (5) and a cylinder section (12B) extending from the bottom section (12A) towards the other end side of the first cylinder (5), and a second piston (18) which is provided such that it can move with a movement of the piston rod (7) to be fitted into the second cylinder (12), and wherein a spring element (21) is provided between the second cylinder (12) and the closing element (9), characterized in that a first communication passage (13) is provided on the second cylinder (12), wherein the first communication passage (13) is provided,to establish a connection between an interior of the second cylinder (12) and a chamber (C2) on the side of the locking element (9), wherein a passage area changing mechanism (22) is provided in this first communication passage (13), wherein the passage area changing mechanism (22) is configured to decrease a passage area of ​​the first communication passage (13) during an extension stroke of the piston rod (7) and to increase the passage area of ​​the first communication passage (13) during a compression stroke of the piston rod (7), and wherein the passage area changing mechanism (22) is a check valve.

Description

TECHNICAL FIELDThe present invention relates to a cylinder device mounted on a vehicle such as a four-wheeled automobile, and preferably serves to absorb vibration of the vehicle.PRIOR ARTIn general, a vehicle such as a four-wheel automobile is equipped with a cylinder device as a hydraulic shock absorber between each of wheels (an axle side) and a vehicle body individually, and the cylinder device is configured to absorb vibration of the vehicle by means of extension and retraction of a piston rod relative to a cylinder (see PTL 1, for example). This type of cylinder device is provided with a hydraulic stopper mechanism configured to prevent the piston rod from exceeding a full limit of extension by limiting the flow of the hydraulic oil when the piston rod is largely extended.CITI ANIMAL LISTPATENT LITERATURE[PTL 1] US 8 418 820 B2US 5 810 130 A is prior art which discloses the features of the preamble of claim 1.SUMMARY OF THE INVENTIONTECHNICAL PROBLEMThen, the stopper mechanism described above is configured in a manner that a communication passage is formed on a free piston provided at the distal end of a recoil spring, and the communication passage of the free piston is blocked by a stopper provided on the piston rod when the piston rod is largely extended. According to this configuration, when the communication passage of the free piston is blocked by the stopper, the flow of the hydraulic oil is stopped, and thereby a resistance force against the extension of the piston rod undesirably suddenly increases. In addition, this configuration results in the flow of the hydraulic oil through the stopper being continuously restricted until the stopper is separated from the free piston when the piston rod is compressed from the fully extended state. As a result, the cylinder device described above has a problem of being unable to stabilize the damping force due to the resistance force generated during the piston rod extension / retraction operation, thereby impairing ride comfort.SOLUTION OF PROBLEMThe present invention has been made in consideration of the above-described problem, and an object thereof is to provide a cylinder device configured to be capable of controlling a resistance force during full extension of a piston rod and a compression operation from the full extended state, thereby achieving excellent riding comfort.The invention is defined by claim 1.According to the one aspect of the present invention, the cylinder device can control the resistance force during the piston rod fully extended and the compression operation from the fully extended state, thereby achieving excellent riding comfort.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a vertical cross-sectional view of a hydraulic shock absorber as a cylinder device according to an embodiment of the present invention. FIG. 2 is a vertical cross-sectional view illustrating a second cylinder in FIG. 1 in an enlarged manner. FIG. 3 is a plan view of the second cylinder illustrated in FIG. 2 as viewed from above. FIG. 4 is a bottom view of the second cylinder illustrated in FIG. 2 as viewed from below. FIG. 5 is a vertical cross-sectional view of an annular valve body in FIG. 1 in an enlarged view. FIG. 6 is a plan view of the annular valve body illustrated in FIG. 5 as viewed from above. FIG. 7 is a bottom view of the annular valve element illustrated in FIG. 5 as viewed from below. FIG. 8 is a vertical cross-sectional view showing the flow of hydraulic oil in a first communication passage and a second communication passage during a compression stroke of a piston rod in an enlarged view. FIG. 9 is a vertical cross-sectional view showing a flow of the hydraulic oil when the second cylinder and the second piston are separated from each other at an extension stroke of the piston rod, in an enlarged view. FIG. 10 is a vertical cross section showing a flow of the hydraulic oil when the second piston is inserted into the second cylinder in the extension stroke of the piston rod, in an enlarged view. FIG. 11 is a cross-sectional view showing a flow of the hydraulic oil when the piston rod is fully extended, in an enlarged view.DESCRIPTION OF THE EMBODIMENTSIn the following description, a cylinder device according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 11 based on an example in applying the cylinder device to a hydraulic shock absorber. In each of the drawings, various types of passages are illustrated in a manner that is larger than in reality to facilitate better understanding of the shapes of the various types of passages and the flows of hydraulic oil therein.In FIG. 1, a hydraulic shock absorber 1 is configured as a two-tube shock absorber, and includes a cylindrical outer cylinder 2 forming an outer periphery of the hydraulic shock absorber 1, an inner cylinder 5 described below, a first piston 6, a piston rod 7, a rod guide 9, and a stopper mechanism 11.The outer cylinder 2 of the hydraulic shock absorber 1 has an open end on one end side thereof (the upper end in FIG. 1 ) and a closed end closed by a bottom cover 2B on the lower end side as the other end side. A radially inwardly bent crimping portion 2A is provided on the open end side (the upper end) of the outer cylinder 2, and this crimping portion 2A holds a cover member 3 closing the open end side of the outer cylinder 2 in a state that prevents the cover member 3 from being detached.The cover member 3 formed of an annular disk is fixed to the outer peripheral side thereof by the crimping portion 2A of the outer cylinder 2 in a state of abutting against the rod guide 9 for closing the open end (upper end) side of the outer cylinder 2, which will be described below. A rod seal 4 made of an elastic material is attached to the inner peripheral side of the cover member 3, and this rod seal 4 seals between the piston rod 7, which will be described later, and the cover member 3.The inner cylinder 5 as a first cylinder is coaxially provided in the outer cylinder 2, and the other end side (the lower end side) of this inner cylinder 5 is fixed to the above-described side of the bottom cover 2B in the inserted state via a bottom valve 5A. The rod guide 9 is fixed to the inner periphery of the one end side (the upper end side) of the inner cylinder 5 by fitting thereto. Hydraulic oil (oil liquid) as the hydraulic liquid is sealingly contained in the inner cylinder 5. As the hydraulic fluid, not only the oil fluid but also, for example, water having an additive mixed therein may be used.Between the inner cylinder 5 and the outer cylinder 2, an annular storage chamber A is formed in which gas is sealed together with the above-described hydraulic oil. This gas may be air in the atmospheric pressure state or gas such as compressed nitrogen gas may be used as it. At the time of compression (a compression stroke) of the piston rod 7, the gas in the storage chamber A is compressed so as to equalize a volume corresponding to an entry of this piston rod 7.The first piston 6 is slidably inserted in the inner cylinder 5. This first piston 6 divides the inside of the inner cylinder 5 (the first cylinder) into two chambers, a bottom-side chamber B and a rod-side chamber C. Further, oil passages 6A and 6B capable of communication between the bottom-side chamber B and the rod-side chamber C are formed on the first piston 6. Further, on the upper end face of the first piston 6, a compression side poppet valve 6C is disposed. The compression-side poppet valve 6C generates a predetermined damping force by applying a resistance force to the hydraulic oil flowing in the oil passage 6A when the first piston 6 is slidably displaced downward by the compression of the piston rod 7. On the other hand, on the lower end surface of the first piston 6, an extension-side poppet valve 6D is disposed. The extension-side poppet valve 6D generates a predetermined damping force by applying a resistance force to the hydraulic oil flowing in the oil passage 6B when the first piston 6 is slidably displaced upward by the extension of the piston rod 7.The other end side (lower end side) of the piston rod 7 is coupled to the first piston 6. More specifically, the lower end side of the piston rod 7 is inserted into the inner cylinder 5 and fixed to the inner circumferential side of the first piston 6 by a nut 8 or the like. Further, the upper end side of the piston rod 7 protrudes outward in an extensible and compressible manner via the rod guide 9, the lid part 3 and the like. On the piston rod 7, an annular groove 7A is formed at a position spaced a predetermined distance from the position where the first piston 6 is fixed. In this annular groove 7A, a stopper ring 19 described below is fixed in an externally fitted state.The rod guide 9 is provided on the upper end side corresponding to the one end side of the inner cylinder 5 (the first cylinder), and forms a closing member that closes the inner cylinder 5 with the piston rod 7 inserted therethrough. The rod guide 9 has a stepped cylindrical shape and is fixed by fitting to the upper end face of the outer cylinder 2 and the upper end face of the inner cylinder 5. Due to this configuration, the rod guide 9 serves to position the upper portion of the inner cylinder 5 at the center of the outer cylinder 2 and also to axially slidably guide (guide) the piston rod 7 by passing the piston rod 7 through the inner circumferential side thereof. Further, the rod guide 9 constitutes a support structure that supports the cover member 3 from the inside when this cover member 3 is tightly squeezed from the outside by the squeezing portion 2A of the outer cylinder 2.The rod guide 9 is formed into a stepped cylindrical shape defined by a large diameter portion 9A and a small diameter portion 9B. The large diameter portion 9A is located on the upper side and fittingly inserted on the inner circumferential side of the outer cylinder 2. The small diameter portion 9B is located on the lower side of this large diameter portion 9A and is fitted on the inner circumferential side of the inner cylinder 5. A cylindrical guide portion 10 is disposed on the inner circumferential side of the small diameter portion 9B. The guide portion 10 axially slidably guides the piston rod 7 through the inside of the inner cylinder 5. The spring member 21 may be fixed to the small diameter portion 9B of the rod guide 9 or by being press-fitted into the inner cylinder 5.On the other hand, the large diameter portion 9A of the rod guide 9 includes an annular oil storage chamber 9C provided on the upper surface of the large diameter portion 9A facing the cover member 3. The oil reservoir chamber 9C surrounds the piston rod 7. when the hydraulic oil (or gas mixed into this hydraulic oil) in the rod-side chamber C escapes, for example, via a small space between the piston rod 7 and the guide portion 10, this oil reservoir chamber 9C serves to provide a space for temporarily storing this leaked hydraulic oil and the like.Further, at the large diameter portion 9A of the rod guide 9, a communication passage (not shown) is provided which continuously communicates with the reservoir chamber A on the outer cylinder 2 side, and this communication passage serves to guide the hydraulic oil (including the gas) stored in the oil reservoir chamber 9C to the reservoir chamber A on the outer cylinder 2 side. In the oil reservoir chamber 9C, a check valve (not shown) is disposed. When the leaked oil in the oil storage chamber 9C increases and overflows therefrom, this check valve serves to flow this overflowing hydraulic oil toward the communication passage of the rod guide 9 (the reservoir chamber A) and prevent flow in the opposite direction.Next, the configuration of the stopper mechanism 11 that is a characteristic feature of the present embodiment will be described.The stopper mechanism 11 is configured to operate when the piston rod 7 extends and moves toward the one end portion in the inner cylinder 5. More specifically, the stopper mechanism 11 is provided in the inner cylinder 5 and configured to operate in a manner described below when the piston rod 7 extends from the outer cylinder 2 and the inner cylinder 5 and moves toward the end portion (a fully extended position) in the inner cylinder 5, thereby stopping the extension operation of the piston rod 7 so as to prevent the piston rod 7 from exceeding a full extension limit value while applying stepwise damping (hydraulic resistance) to this extension operation.The stopper mechanism 11 includes a second cylinder 12, a second piston 18, the spring member 21 (a recoil spring), and a passage area changing mechanism 22. The second piston 18 is located on the rod guide 9 side with respect to the first piston 6, and is provided on the outer circumferential side of the piston rod 7. The spring member 21 is provided between the second cylinder 12 and the rod guide 9. The passage area changing mechanism 22 changes the passage area of a first communication passage 13.The second cylinder 12 is arranged movably relative to the piston rod 7. On the other hand, the second cylinder 12 is mounted on the lower end portion of the spring member 21 and can move vertically in the inner cylinder 5 according to the expansion and compression of the spring member 21. Further, the second cylinder 12 divides the inside of the rod-side chamber C into a chamber C 1 on the first piston 6 side and a chamber C 2 on the rod guide 9 side as a chamber on the closing member side. The second cylinder 12 is made of, for example, an oil-resistant, wear-resistant, and elastic resin material. The second cylinder 12 may be made of a metallic material without being limited to the resin material. However, in the case where the second cylinder 12 is made of the metallic material, a piston ring made of resin or the like should be provided between the second cylinder 12 and the inner cylinder 5.As illustrated in FIGS. 2 to 4, 8 and the like, the second cylinder 12 includes an annular bottom portion 12A and a cylindrical cylinder portion 12B. The bottom portion 12A is located on the upper end side (the one end side) in the inner cylinder 5. the cylinder portion 12B extends around this bottom portion 12A toward the lower end side (the other end side). A fitting portion 12C extending toward the upper end side is provided on the radially inner side of the bottom portion 12A.The bottom portion 12A is formed as an annular member whose outer diameter is slightly smaller than the inner diameter of the inner cylinder 5 and whose inner diameter is slightly larger than the inner diameter of the piston rod 7. Internal passages 12A 1 are provided at three portions on the inner peripheral portion of the bottom portion 12A at peripheral intervals (see FIGS. 3 and 4 ). The internal passages 12A 1 form a part of the first communication passage 13 which will be described below. On the other hand, second communication passages 14 described below are provided at three portions on the outer peripheral portion of the bottom portion 12A at circumferential intervals. Further, an annular valve seat 12A 2 is formed on the lower surface of the bottom portion 12A. An upper surface 17A of an annular valve element 17 described below abuts on the annular valve seat 12A2 so that the valve can be opened and closed.The cylinder portion 12B is formed as a cylindrical member whose outer diameter is slightly smaller than the inner diameter of the inner cylinder 5. further, the inner circumferential surface of the cylinder portion 12B includes a small diameter portion 12B 1, a large diameter portion 12B 2, and a mounting groove portion 12B 3. The small diameter portion 12B 1 is disposed at the upper end portion. The large diameter portion 12B 2 is disposed on the lower end side with respect to this small diameter portion 12B 1, and is formed to have a larger diameter than the small diameter portion 12B 1. The attachment groove portion 12B 3 is located between the small diameter portion 12B 1 and the large diameter portion 12B 2, and is formed to have a larger diameter than the large diameter portion 12B 2. The annular valve element 17 is disposed on the inner circumferential side of the small diameter portion 12B 1. An annular member 16, which will be described below, is fitted to the inner circumferential side of the attachment groove portion 12B 3.On the other hand, throttle oil grooves 15 described below are provided at three portions on the inner circumferential side of the large diameter portion 12B 2 at circumferential intervals. In addition, a gradually widening cone surface portion 12B 4 is formed at the lower end portion of the large diameter portion 12B 2. This cone surface portion 12B 4 serves to smoothly guide the second piston 18 that moves upward together with the piston rod 7 upon extension of this piston rod 7 into the large diameter portion 12B 2.The fitting portion 12C is formed by dividing a cylindrical body extending from the radially inner side of the bottom portion 12A toward the upper end side into a plurality of pieces, e.g., three pieces, in the circumferential direction with large clearances therebetween. Therefore, the fitting portion 12C can be elastically deformed radially. Further, an engaging portion 12C 1 is provided at the upper end portion of the fitting portion 12C so as to protrude radially outward. The engaging portion 12C 1 engages with the other end portion of the spring member 21 from the inner circumferential side. Due to this configuration, the second cylinder 12 can move axially in the inner cylinder 5 together with the lower end portion (the free end) of the spring member 21.Then, the first communication passage 13, the second communication passages 14, and the throttle oil grooves 15 are provided on the second cylinder 12. These passages will now be described.As illustrated in FIGS. 8 and 9, the first communication passage 13 serves to communicate between the inside of the second cylinder 12 and the chamber C 2 on the rod guide 9 side. The first communication passage 13 is formed as a passage extending through each of the inner passages 12A 1 provided on the bottom portion 12A of the second cylinder 12, the small diameter portion 12B 1 and the large diameter portion 12B 2 of the cylinder portion 12B, and between an inner circumferential surface 16A of the annular member 16 described later and the outer circumferential surface of the piston rod 7. In the first communication passage 13, the range of the passage for the hydraulic oil is controlled (adjusted) by the passage range changing mechanism 22 described below. Further, the first communication passage 13 is blocked when the second piston 18, which will be described later, abuts against a lower surface 16C of the annular member 16 (see FIG. 11 ).The second communication passages 14 are for continuously establishing communication between the rod guide 9 side chamber C 2 and the first piston 6 side chamber C 1 in the rod side chamber C corresponding to the rod guide 9 side in the inner cylinder 5. The second communication passages 14 are formed between the inner periphery of the inner cylinder 5 and the outer periphery of the second cylinder 12. More specifically, the second communication passages 14 include a plurality of recessed grooves, such as three recessed grooves, which are provided in an axially extending manner on the outer circumferential surfaces of the bottom portion 12A and the cylinder portion 12B of the second cylinder 12 and are formed between the second cylinder 12 and the inner circumferential surface of the inner cylinder 5.The second communication passages 14 function as a throttle that limits the flow rate of the hydraulic oil to a small amount when the hydraulic oil flows between the chamber C 2 on the rod guide 9 side and the chamber C 1 on the first piston 6 side. Due to this configuration, when the first communication passage 13 is blocked, the movement of the second cylinder 12 can be restricted to a small movement (the state illustrated in FIG. 11 ). On the other hand, the second communication passages 14 secure the flow of the hydraulic oil, so that the second cylinder 12 can move toward the first piston 6 side even when the first communication passage 13 is blocked.The throttle oil grooves 15 form a part of the passage area changing mechanism 22 described below, and are provided on the way of the first communication passage 13. More specifically, the throttle oil grooves 15 are disposed at a plurality of portions, such as three portions, on the large diameter portion 12B 2 of the cylinder portion 12B constituting the second cylinder 12 at circumferential intervals. As shown in FIG. 2, each of the throttle oil grooves 15 is formed into a wide and deeply indented large flow passage 15A on the side of the lower cone face portion 12B 4 and a narrow and flatly indented small flow passage 15B on the upper side of the large diameter portion 12B 2. In other words, each of the throttle oil grooves 15 is formed such that the groove width and the groove depth gradually decrease from the lower side toward the upper side. Due to this configuration, each of the throttle oil grooves 15 can gradually reduce the flow rate of the hydraulic oil because the second piston 18, which will be described below, is inserted into the large-diameter portion 12B 2 of the cylinder portion 12B 2 and moves from the large flow passage 15A toward the small flow passage 15B.When the second piston 18 reaches the large flow passage 15A, a passage is formed between each of the throttle oil grooves 15 and the outer circumferential surface of this second piston 18. A value obtained by adding the passage areas of these large flow passages 15A at the three portions is set to a larger value than the passage areas of a throttle passage 17C of the annular valve element 17. due to this configuration, as illustrated in FIG. 10, fluid in a chamber C 3 formed by the inside of the second cylinder 12 and the second piston 18 formed when the second piston 18 reaches the large flow passages 15A flows to the chamber C 1 on the first piston 6 side via the large flow passages 15A, and therefore, the resistance force can be prevented from excessively increasing. Therefore, the throttle oil grooves 15 can generate the resistance force together with the throttle passage 17C of the annular valve element 17 against the piston rod 7 during the extension stroke.The annular member 16 is fixed to the fixing groove portion 12B 3 of the cylinder portion 12B constituting the second cylinder 12 in the inserted state. The annular member 16 is constituted by an annular member having a rectangular cross section, the inner diameter dimension of which is set to a larger dimension than the outer diameter dimension of the piston rod 7. due to this configuration, the annular member 16 forms a part of the first communication passage 13 between the inner circumferential surface 16A and the outer circumferential surface of the piston rod 7. in this case, the diameter dimension of the inner circumferential surface 16A of the annular member 16 is set to a dimension sufficiently larger than the dimension of the outer diameter of the piston rod 7 so that the hydraulic oil can smoothly flow (not to generate high flow resistance) between the chamber C 1 on the first piston 6 side and the chamber C 2 on the rod guide 9 side.Further, as illustrated in FIG. 8, a lower surface 17B of the annular valve element 17 described below abuts / moves away from an upper surface 16B of the annular element 16. On the other hand, as shown in FIG. 11, the lower surface 16C of the annular member 16 forms a valve seat against which an upper surface 18A of the second piston 18 abuts so that the valve can be opened and closed. In a blocked state in which the upper surface 18A of the second piston 18 abuts against the lower surface 16C of the annular member 16 (a valve-closed state), the first communication passage 13 is blocked.The annular valve element 17 is disposed between the piston rod 7 and the small diameter portion 12B 1 of the cylinder portion 12B constituting the second cylinder 12, and is provided without any space generated so as not to cause a flow of the hydraulic fluid between the piston rod 7 and the inner periphery of the annular valve element 17. On the other hand, the annular valve element 17 is movable relative to the piston rod 7 by abutting against the bottom portion 12A of the second cylinder 12 or the upper surface 16B of the annular valve seat 16 due to the movement of the piston rod 7. As shown in FIGS. 5 to 7, the annular valve member 17 is constituted by an annular member having a rectangular cross section, and includes the upper surface 17A and the lower surface 17B. In addition, the throttle passage 17C is provided on the upper surface 17A of the annular valve element 17. The throttle passage 17C extends radially, thereby having a small passage area. Large passages 17D are provided at a plurality of portions, such as four portions, on the lower surface 17B side at circumferential intervals to allow the hydraulic fluid to flow without resistance.The inner diameter dimension of the annular valve element 17 is set to a dimension slightly larger than the outer diameter dimension of the piston rod 7. Due to this configuration, the annular valve element 17 moves in a direction indicated by an arrow a (downward) following the piston rod 7, and abuts the lower surface 17B with the upper surface 16B of the annular element 16, as illustrated in FIG. 8, during the compression stroke of the piston rod 7. On the other hand, the annular valve element 17 moves in a direction indicated by an arrow b (upward) following the piston rod 7, and brings the upper surface 17A into abutment with the annular valve seat 12A 2 of the bottom portion 12A during the extension stroke of the piston rod 7, as illustrated in FIG. 9.On the other hand, the outer diameter dimension of the annular valve element 17 is set to a dimension slightly smaller than the inner diameter dimension of the small diameter portion 12B 1. This configuration allows the hydraulic oil to flow without applying high resistance thereto because an annular passage is generated between the annular valve element 17 and the small-diameter portion 12B 1.The lower surface 17B of the annular valve member 17 may abut and separate from the upper surface 16B of the annular member 16. As illustrated in FIG. 9, the annular valve element 17 can increase the flow resistance against the hydraulic oil in the first communication passage 13 due to the throttle passage 17C by bringing the upper surface 17A into abutment with the annular valve seat 12A 2 of the bottom portion 12A when the piston rod 7 extends in the direction indicated by the arrow b. Further, as illustrated in FIG. 8, when the piston rod 7 is compressed in the direction indicated by the arrow a, the upper surface 17A of the annular valve element 17 moves away from the annular valve seat 12A 2 of the bottom portion 12A, whereby the hydraulic oil can flow in the first communication passage 13 due to each of the large passages 17D with low resistance.In this way, the annular valve element 17 can flow the hydraulic oil from the chamber C 1 on the first piston 6 side to the chamber C 2 on the rod guide 9 side due to each of the large passages 17D as indicated by an arrow D in FIG. 8. On the other hand, as indicated by an arrow F in FIG. 9 and an arrow H in FIG. 10, when the hydraulic oil flows from the chamber C 2 on the rod guide 9 side to the chamber C 1 on the first piston 6 side, a substantially blocked state is established because the hydraulic oil flows only through the throttle passage 17C for securing the minimum passage area to prevent the occurrence of a hydraulic blockage.Due to this configuration, the annular valve element 17 constitutes, together with the annular valve seat 12A 2, a check valve that allows the flow of the hydraulic oil from the chamber C 1 on the first piston 6 side toward the chamber C 2 on the rod guide 9 side and suppresses the flow in the opposite direction.The second piston 18 is disposed between the first piston 6 and the second cylinder 12, and is provided on the outer circumferential side of the piston rod 7. The second piston 18 is provided so as to be able to move along with the movement of the piston rod 7 to be fitted into the cylinder portion 12B of the second cylinder 12. The second piston 18 is integrally connected to the outer circumferential side of the piston rod 7 at the outer circumferential side of the piston rod 7 using the stopper ring 19 fitted into the annular groove 7A of this piston rod 7.The second piston 18 has a vertically extending rectangular shape in cross section, and the upper surface 18A thereof forms a valve body that abuts / moves away (seats / separates) from the lower surface 16C of the annular member 16. In other words, the second piston 18 is inserted into the large-diameter portion 12B 2 of the cylinder portion 12B of the second cylinder 12 when the piston rod 7 moves in the extending direction by a distance corresponding to a predetermined amount or longer. When the piston rod 7 continues to extend, the second piston 18 brings the upper surface 18A thereof into abutment with the lower surface 16C of the annular member 16, thereby blocking the first communication passage 13.Also, a chamfered portion 18B is provided around the upper surface 18A. The chamfered portion 18B gradually decreases in diameter toward the upper side. This chamfered portion 18B serves to smoothly guide the second piston 18 into the large diameter portion 12B 2 of the cylinder portion 12B when the piston rod 7 extends, in cooperation with the tapered surface 12B 4 of the cylinder portion 12B.Further, an annular piston ring 20 is provided which is externally mounted on the outer circumferential side of the second piston 18. This piston ring 20 serves to seal between the large-diameter portion 12B 2 and the second piston 18 so as to restrict the flow of the hydraulic oil by bringing its outer circumferential surface into sliding contact with the inner circumferential surface of the large-diameter portion 12B 2 when the second piston 18 enters the large-diameter portion 12B 2 of the cylinder portion 12B.The spring member 21 constitutes the recoil spring and is provided on the outer circumferential side of the piston rod 7 in the inner cylinder 5. Further, the spring member 21 is disposed between the rod-side space C, i.e., the second cylinder 12 and the rod guide 9. Further, the spring member 21 comprises a vertically extendable and compressible compression coil spring whose upper end portion is fixed to the rod guide 9, for example. On the other hand, the fitting portion 12C of the second cylinder 12 is integrally fitted into the lower end portion of the spring member 21. Thereby, the spring member 21 can axially position the second cylinder 12 in the rod-side chamber C unless the piston rod 7 is extended far. The spring member 21 constituting the recoil spring serves to suppress, for example, rolling of the vehicle body when cornering by limiting the extension of the piston rod 7. The spring member 21 may be configured such that the upper end portion thereof is fixed to the inner cylinder 5.The passage area changing mechanism 22 is provided in the first communication passage 13 of the second cylinder 12. The passage area changing mechanism 22 serves to decrease the passage area of the first communication passage 13 during the extension stroke of the piston rod 7 and increase the passage area of the first communication passage 13 during the compression stroke of the piston rod 7. The passage area changing mechanism 22 is constructed using the valve structure formed by the bottom portion 12A of the second cylinder 12 and the annular valve element 17, the valve structure formed by the annular element 16 and the second piston 18, and the valve structure formed by each of the throttle oil grooves 15 and the second piston 18. Further, the passage area changing mechanism 22 positions the second cylinder 12 using the spring member 21 to allow the annular valve member 17 to seat on / separate from the bottom portion 12A (the annular valve seat 12A 2) of the second cylinder 12 and allow the second piston 18 to be inserted into / extracted from the second cylinder 12. In this way, the spring member 21 forms a part of the passage area changing mechanism 22.The hydraulic shock absorber 1 according to the present embodiment is configured in the above-described manner. Subsequently, the hydraulic shock absorber 1 is mounted on the vehicle such that the upper end side of the piston rod 7 and the bottom cover 2B side (the lower end side) of the outer cylinder 2 are attached to the body side and the axle side (both not shown) of the automobile. Thereby, when vibration occurs during running of the automobile, a pressure-side damping force and an extension-side damping force are generated by the poppet valves 6C and 6D of the first piston 6 and the like when the piston rod 7 axially springs / extends into and out of the inner cylinder 5 and the outer cylinder 2, and thereby can absorb the vertical vibration of the vehicle in a damping manner.In the hydraulic shock absorber 1, it is now difficult to limit the full extension movement of the piston rod 7 and control an operation of switching the piston rod 7 from the full extension movement to the retraction movement, and this difficulty results in achieving no stable resistance force and decreasing riding comfort. However, in the present embodiment, the hydraulic shock absorber 1 can stably control the resistance force at the time of fully extending the piston rod 7 and the compression operation from the fully extended state.More specifically, the hydraulic shock absorber 1 according to the present invention performs the control of the resistance force in compression of the piston rod 7, the control of the resistance force in extension of the piston rod 7 toward the fully extended position, and the control of the switching operation from the fully extended position to the compression operation, and these control methods will be described with reference to Figs. 8 to 11.First, in FIG. 8, the normal compression stroke of the piston rod 7 is shown independently of the full extension of the piston rod 7. During the compression stroke, the piston rod 7 moves in the direction indicated by the arrow a. At this time, when moving together with the piston rod 7 in the direction indicated by the arrow a (downward), the lower surface 17B abuts on the upper surface 16B of the annular member 16.As a result, the first communication passage 13 can allow the hydraulic oil to flow from the chamber C 1 on the first piston 6 side into the chamber C 2 on the rod guide 9 side via the passage defined by the space between the large diameter portion 12B 2 of the cylinder portion 12B constituting the second cylinder 12 and the outer circumferential surface of the piston rod 7, the passage defined by the space between the inner circumferential surface 16A of the annular member 16 and the outer circumferential surface of the piston rod 7, each of the large passages 17D of the annular valve member 17, the passage defined by the space between the small diameter portion 12B 1 and the annular valve member 17, and each of the inner passages 12A 1 of the bottom portion 12A as indicated by the arrow D, is defined.In this case, since the annular valve element 17 moves away from the annular valve seat 12A 2 of the bottom portion 12A and the second piston 18 does not enter the large-diameter portion 12B 2, the first communication passage 13 is in a fully opened state in which the hydraulic oil flowing therein experiences a minimum resistance. The first communication passage 13 allows the hydraulic oil in this fully opened state to flow therethrough as a passage having a large passage area. Moreover, the hydraulic oil may also flow from the chamber C 1 on the first piston 6 side to the chamber C 2 on the rod guide 9 side through each of the second communication passages 14 as indicated by an arrow E, although the amount of the hydraulic oil is small. In addition, the hydraulic oil may also flow through the first communication passage 13 in the fully opened state and each of the second communication passages 14 during the normal extension stroke (not shown) of the piston rod 7.Therefore, the hydraulic shock absorber 1 can generate a stable damping force by means of the poppet valves 6C and 6D of the first piston 6 and the bottom valve 5A during the compression stroke and the extension stroke in normal times regardless of the complete extension movement of the piston rod 7, thereby achieving excellent ride comfort.FIGS. 9 to 11 show the extension stroke when the piston rod 7 extends largely in the direction of the fully extended position. During this extension stroke, the piston rod 7 moves upward in the direction indicated by the arrow b, and the hydraulic oil flows from the chamber C 2 on the rod guide 9 side to the chamber C 1 on the first piston 6 side via the first communication passage 13 and each of the second communication passages 14.FIG. 9 shows a stroke in a first stage, in which the piston rod 7 largely extends during the extension stroke of the piston rod 7. During the extension stroke in this first stage, the piston rod 7 moves in the direction indicated by the arrow b. At this time, the annular valve element 17 moves together with the piston rod 7 in the direction indicated by the arrow b (upward), and the upper surface 17A thereof abuts against the annular valve seat 12A 2 of the lower portion 12A of the second cylinder 12. The resistance against the flow of the hydraulic oil can be increased by the throttle passage 17C with the upper surface 17A of the annular valve element 17 abutting against the annular valve seat 12A 2 of the bottom portion 12A.More specifically, as indicated by the arrow F in FIG. 9, the hydraulic oil flowing in the first communication passage 13 flows at the flow rate restricted by the throttle passage 17C. Moreover, the hydraulic oil may also flow from the chamber C 2 on the rod guide 9 side to the chamber C 1 on the first piston 6 side through each of the second communication passages 14 as indicated by an arrow G, although the flow rate thereof is small. As a result, when the piston rod 7 extends, a resistance force corresponding to the first stage can be applied.FIG. 10 shows an extension stroke when the resistance against the hydraulic oil flowing in the first communication passage 13 gradually increases in the extension stroke of the piston rod 7. During the extension stroke in this second stage, the second piston 18 is inserted into the large-diameter portion 12B 2 of the cylinder portion 12B constituting the second cylinder 12. At the time of this insertion of the second piston 18, the taper surface portion 12B 4 is formed on the opening side of the cylinder portion 12B, and the chamfered portion 18B is formed on the second piston 18. Therefore, this taper surface portion 12B 4 and the chamfered portion 18B guide the second piston 18 by contacting each other, whereby the second piston 18 can be smoothly inserted into the large-diameter portion 12B 2 even when the second piston 18 and the large-diameter portion 12B 2 of the cylinder portion 12B are not aligned with each other.When the second piston 18 is inserted into the large diameter portion 12B 2 of the cylinder portion 12B 2, this second piston 18 covers each of the throttle oil grooves 15 from the inner circumferential side, and therefore, the passage area of the first communication passage 13 is narrowed due to the throttle oil grooves 15 at the three portions. In other words, as indicated by the arrow H, the hydraulic oil flowing in the first communication passage 13 is guided to the outside of the first piston 6 side chamber C 1 through each of the throttle oil grooves 15. In this case, the second piston 18 moves from the large flow passage 15A toward the small flow passage 15B of each of the throttle oil grooves 15 along with the movement of the piston rod 7 in the direction indicated by the arrow b. As a result, the hydraulic shock absorber 1 can gradually narrow the first communication passage 13, thereby smoothly increasing the resistance force.FIG. 11 shows an extension stroke when the first communication passage 13 is blocked to prevent the piston rod 7 from exceeding the full extension limit in the extension stroke of the piston rod 7. During the extension stroke in this third stage, the second piston 18 inserted into the large-diameter portion 12B 2 of the cylinder portion 12B constituting the second cylinder 12 moves together with the piston rod 7 in the direction indicated by the arrow b, and abuts the annular member 16 in the fully extended position of the piston rod 7. Therefore, the upper surface 18A of the second piston 18 abuts against the lower surface 16C of the annular member 16 and blocks the passage between the inner circumferential surface 16A of the annular member 16 and the piston rod 7. as a result, the hydraulic shock absorber 1 can block the first communication passage 13 and thereby restrict the movement of the second cylinder 12, i.e., the extension of the piston rod 7 to a slight extension realized by each of the second communication passages 14.In addition, when the piston rod 7 is switched from the fully extended position to the compression operation, the hydraulic shock absorber 1 may allow the second piston 18 to move toward the opening side of the second piston 12 by flowing the hydraulic oil via the second communication passages 14. Consequently, when the piston rod 7 is compressed from the fully extended state, the hydraulic shock absorber 1 can control the resistance force against the movement of the piston rod 7 to a small force by flowing the hydraulic oil via the first communication passage 13 and the second communication passages 14.In this way, according to the present embodiment, the stopper mechanism 11 that operates when the piston 7 extends and moves toward the upper end portion in the inner cylinder 5 is provided movably relative to the piston rod 7, and includes the second cylinder 12 including the bottom portion 12A on the upper end side in the inner cylinder 5 and the cylinder portion 12B extending from this bottom portion 12A to the lower end side, and the second piston 18 provided so as to be able to move along with the movement of the piston rod 7 to be fitted into the second cylinder 12. Further, the spring member 21 is provided between the second cylinder 12 and the rod guide 9.Therefore, the hydraulic shock absorber 1 can control the piston rod 7 to be prevented from exceeding the full limit of extension by means of the second cylinder 12 and the second piston 18 provided on the lower end side of the spring member 21. As a result, the hydraulic shock absorber 1 can stabilize the resistance force upon extension of the piston rod 7, thereby achieving excellent ride comfort.The first communication passage 13 that communicates between the inside of the second cylinder 12 and the chamber C 2 on the rod guide 9 side is provided on the second cylinder 12. In this first communication passage 13, the passage area changing mechanism 22 is provided. The passage area changing mechanism 22 decreases the passage area of the first communication passage 13 during the extension stroke of the piston rod 7 and increases the passage area of the first communication passage 13 during the compression stroke of the piston rod 7. as a result, the hydraulic shock absorber 1 can prevent the piston rod 7 from exceeding the full extension limit due to the high resistance force during the extension stroke of the piston rod 7. On the other hand, the hydraulic shock absorber 1 can stabilize the control by prioritizing the damping force on the first piston 6 side during the compression stroke of the piston rod 7, and thereby also obtains excellent ride comfort.The passage area changing mechanism 22 is formed as a check valve. As a result, the passage area changing mechanism 22 can flow the hydraulic oil from the chamber C 1 on the first piston 6 side toward the chamber C 2 on the rod guide 9 side and suppress the flow in the opposite direction.The second communication passages 14 that establish the constant communication between the rod guide 9 side (the chamber C 2) and the first piston 6 side (the chamber C 1) in the inner cylinder 5 are provided on the second cylinder 12. Due to this determination, the hydraulic shock absorber 1 can allow the hydraulic oil to flow between the rod guide 9 side and the first piston 6 side in the inner cylinder 5 via the second communication passages 14 when the piston rod 7 is switched to the compression operation even when the first communication passage 13 is blocked when the piston rod 7 is in the fully extended position. As a result, the hydraulic shock absorber 1 can reduce the resistance force to a small force when the piston 7 is compressed from the fully extended state.The second communication passages 14 are formed between the inner periphery of the inner cylinder 5 and the outer periphery of the second cylinder 12. Consequently, the second communication passages 14 can be easily formed only by forming grooves on the outer periphery of the second cylinder 12.The second cylinder 12 is made of the resin material and therefore can be not only easily manufactured but also reduce weight.The embodiment has been described with reference to the example in which the inner passages 12A 1 of the bottom portion 12A form the second cylinder 12, the second communication passages 14, and the throttle oil grooves 15 are provided at three portions, respectively. However, the present invention is not limited thereto, and may be configured in a manner such that, for example, the inner(s) passage(s) 12A 1, the second(s) communication passage(s) 14, and the throttle oil groove(s) 15 are provided at one portion, two portions, or four or more portions, respectively.Further, the embodiment has been described with reference to the example in which the second piston 18 is fixed to the piston rod 7 via the stopper ring 19. However, the present invention is not limited thereto, and may be configured in a manner that an annular fitting portion protruding radially inward is provided on the second piston, and the second piston is fixed to the piston rod 7 by fitting this fitting portion into the annular groove 7A of the piston rod 7.The embodiment has been described with reference to the example in which the second cylinder 12 is entirely made of the resin material. However, the present invention is not limited thereto, and may be configured in a manner such that, for example, most of the second cylinder is formed of a metallic material and a resin ring member is attached to the outer circumferential side of the metallic second cylinder.On the other hand, the embodiment has been described with reference to the example in which the throttle oil grooves 15 each having the gradually decreasing groove width and groove depth from the lower side to the upper side are provided at the large diameter portion 12B 2 of the cylinder portion 12B constituting the second cylinder 12. However, the present invention is not limited thereto, and the throttle oil grooves 15 may be removed in a case where, for example, the large-diameter portion of the cylinder portion is formed in a tapered manner such that the diameter dimension decreases from the lower side (the opening side) to the upper side (the deep side). In other words, the throttle passage may be formed between the conical surface and the second piston.Further, the embodiment has been described taking the example of the two-tube shock absorber including the outer cylinder 2 and the inner cylinder 5. However, the present invention is not limited thereto, and may also be applied to a single-tube shock absorber provided by slidably inserting the piston into a single cylinder.Further, the embodiment has been described taking the hydraulic shock absorber 1 mounted on each of the wheel sides of the four-wheeled automobile as a representative example. However, the present invention is not limited thereto, and may be embodied by, for example, a hydraulic shock absorber for use in a two-wheeled vehicle, or may be used for a cylinder device for use in various types of machines, buildings, or the like other than a vehicle.Possible configurations as a cylinder device based on the above-described embodiments include the following examples.A first configuration of a cylinder device includes a first cylinder that sealingly contains hydraulic fluid, a first piston that is slidably fitted into the first cylinder and defines an interior of this first cylinder into a rod-side chamber and a bottom-side chamber, a piston rod coupled to the first piston, a closing member that is provided on an end side of the first cylinder and is configured to close the first cylinder with the piston rod inserted therethrough, and a stopper mechanism configured to operate when the piston rod extends and moves toward an end portion within the first cylinder. The stopper mechanism includes a second cylinder provided movably relative to the piston rod and including a bottom portion on the one end side of the first cylinder and a cylinder portion extending from this bottom portion to the other end side, and a second piston provided so as to be able to move with movement of the piston rod to be fitted into the second cylinder. A spring element is provided between the second cylinder and the closing element.As a second configuration of the cylinder device, in the first configuration, a first communication passage is provided on the second cylinder. The first communication passage is configured to communicate between the inside of the second cylinder and a chamber on the closing member side. In this first communication passage, a passage area changing mechanism is provided. The passage area changing mechanism is configured to reduce the passage area of the first communication passage during an extension stroke of the piston rod and increase the passage area of the first communication passage during a compression stroke of the piston rod.As a third configuration of the cylinder device, in the second configuration, the passage area changing mechanism is a check valve.As a fourth configuration of the cylinder device, in the first or second configuration, a second communication passage is provided on the second cylinder. The second communication passage is configured to establish continuous communication between the closing member side and the first piston side in the first cylinder.As a fifth configuration of the cylinder device, in the third configuration, the second communication passage is formed between an inner periphery of the first cylinder and an outer periphery of the second cylinder.As a sixth aspect of the cylinder device, in the first to fourth aspects, the second cylinder is made of a resin material.The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail in order to facilitate better understanding of the present invention, and the present invention is not necessarily limited to the configuration including all the features described. Further, a part of the configuration of one embodiment may be replaced with the configuration of another embodiment. Further, a certain embodiment may also be implemented by a configuration of another embodiment added to the configuration of this embodiment. Moreover, each of the embodiments may also be implemented by a different configuration that is added, deleted, or replaced with respect to a part of the configuration of this embodiment.LIST OF REFERENCE CHARACTERS1 Hydraulic shock absorber (cylinder device) 5 Inner cylinder (first cylinder) 6 First piston 7 Piston rod 9 Rod guide (closing member) 11 Stopper mechanism 12 Second cylinder 12A Bottom portion 12B Cylinder portion 13 First communication passage 14 Second communication passage 18 Second piston 21 Spring member 22 Passage area changing mechanism B Bottom-side chamber C Rod-side chamber C 1 First piston C 2 Rod guide-side chamber (closing member-side chamber)

Claims

A cylinder device comprising: a first cylinder (5) that sealingly contains hydraulic fluid; a first piston (6) slidably fitted in the first cylinder (5) and defining an inner side of this first cylinder (5) into a rod-side chamber (C) and a bottom-side chamber (B); an oil passage (6A) provided on the first piston (6) and configured to establish communication between the rod-side chamber (C) and the bottom-side chamber (B); a poppet valve (6D) configured to suppress movement of the hydraulic fluid flowing in the oil passage (6A) to generate a damping force; a piston rod (7) coupled to the first piston (6); a closing member (9) provided on one end side of the first cylinder (5) and configured to close the first cylinder (5) with the piston rod (7) inserted therethrough; and a stopper mechanism (11) configured to operate when the piston rod (7) extends and moves toward an end portion inside the first cylinder (5), the stopper mechanism (11) comprising a second cylinder (12) provided movably relative to the piston rod (7), the second cylinder (12) having a bottom portion (12A) on the one end side of the first cylinder (5) and a cylinder portion (12B) extending from the bottom portion (12A) toward the other end side of the first cylinder (5), and a second piston (18) provided to be movable with movement of the piston rod (7), A spring member (21) for fitting into the second cylinder (12), and a spring member (21) is provided between the second cylinder (12) and the closing member (9), characterized in that a first communication passage (13) is provided on the second cylinder (12), the first communication passage (13) is configured to communicate between an inside of the second cylinder (12) and a chamber (C2) on the closing member (9) side, and in that a passage area changing mechanism (22) is provided in this first communication passage (13), the passage area changing mechanism (22) is configured to decrease a passage area of the first communication passage (13) during an extension stroke of the piston rod (7) and increase the passage area of the first communication passage (13) during a compression stroke of the piston rod (7), and the passage area changing mechanism (22) is a check valve.The cylinder device according to claim 1, wherein a second communication passage (14) is provided on the second cylinder (12), the second communication passage (14) being configured to constantly establish communication between the closing member (9) side and the first piston side in the first cylinder (5).The cylinder device according to claim 2, wherein the second communication passage (14) is formed between an inner periphery of the first cylinder (5) and an outer periphery of the second cylinder (12).The cylinder device according to any one of claims 1 to 3, wherein the second cylinder (12) is formed of a resin material.

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