JP7089403B2 - damper - Google Patents

Description

The present invention relates to a damper.

Dampers are widely used to suppress vibrations of vibration damping objects such as machines, structures, and vehicles. The damper comprises, for example, a cylinder, a piston that is slidably inserted into the cylinder and divides the inside of the cylinder into an extension side chamber and a compression side chamber, and a rod that is inserted into the cylinder and connected to the piston. It creates a pressure difference between the extension side chamber and the compression side chamber during expansion and contraction, and exerts a damping force that resists expansion and contraction.

Normally, the damper compensates for the volume change when the rod goes in and out of the cylinder and the volume change due to the temperature change of the working liquid in the case of the single rod type, and in the case of the double rod type, it depends on the temperature change of the working liquid. It is equipped with a reservoir to store gas and working fluid to compensate for volume changes.

In order for such a damper to exert the damping force as set regardless of the mounting posture to the vibration damping target, it is necessary to prevent the gas in the reservoir from entering the cylinder, and in that case, the reservoir is regarded as a gas. It is preferable to use an accumulator having a structure that separates the working liquid so that it does not mix with the working liquid.

For example, if there is a damper in which the accumulator is formed inside the rod, but there is not enough space for installation, the outer diameter of the damper is limited and the rod must be made smaller in diameter, and the capacity of the accumulator may not be secured (. For example, see Patent Document 1).

On the other hand, there is a damper in which an outer cylinder is provided on the outer periphery of the cylinder and the annular gap between the cylinder and the outer cylinder is used as an accumulator (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2004-116552 Japanese Unexamined Patent Publication No. 11-82605

By the way, when the damper is fully extended, it is necessary to take care so that the inside of the cylinder does not fall below the atmospheric pressure, and when the damper is fully contracted, the force (rod) that pushes the rod out of the cylinder by the pressure in the cylinder. It is necessary to take care not to make the reaction force excessive. In order to meet such a requirement, in a damper provided with an accumulator, the accumulator may apply prepressure to the extension side chamber and the compression side chamber in the cylinder.

However, the length and wall thickness of the cylinder and outer cylinder are uniquely determined by design according to the installation space and the vibration damping target. In this way, when trying to use the space between the cylinder and the outer cylinder as an accumulator, the volume of the accumulator is uniquely determined by design, so the rod reaction force is applied even if the damper is fully extended or contracted. It is very difficult to adjust the characteristics of the accumulator to be optimal.

Also, if you try to solve this problem by adopting a structure that provides a separate accumulator on the outside of the damper, the entire damper will become large and the shape will be asymmetrical, so when installing the damper in the installation space, etc. Installation work becomes very troublesome because it may cause interference with parts.

Therefore, an object of the present invention is to provide a damper in which the characteristics of the accumulator can be easily optimized and the installation work can be easily performed.

In order to achieve the above object, the present invention has a cylinder, a piston that is slidably inserted into the cylinder and divides the inside of the cylinder into an extension side chamber and a compression side chamber, and a piston that is inserted into the cylinder and has a piston. A damper having a rod connected to the piston and an outer cylinder arranged on the radially outer side of the cylinder to cover the cylinder and form a reservoir that is communicated in the cylinder between the cylinder and the cylinder. A tubular free piston that is slidably attached to either one and accommodated in the reservoir, and a tubular free piston that is attached to either the cylinder or the outer cylinder and slides on the inner circumference of the free piston. It is equipped with a stopper that forms an air chamber in contact with the free piston and a spring element that urges the free piston in the direction of expanding the air chamber. The working liquid is discharged from the cylinder to the reservoir, and the free piston approaches the stopper to reduce the volume of the air chamber by the body integral of the working liquid discharged to the reservoir. The volume of the working liquid discharged from the inside is supplied from the reservoir to the cylinder, and the free piston is separated from the stopper to expand the volume of the air chamber by the body integral of the working liquid supplied to the cylinder . Further, the damper of another invention includes a cylinder, a piston that is slidably inserted into the cylinder and divides the inside of the cylinder into an extension side chamber and a compression side chamber, and a rod that is inserted into the cylinder and connected to the piston. And the outer cylinder, which is arranged on the radial outer side of the cylinder and covers the cylinder to form a reservoir that communicates with the cylinder, and is slidably mounted on either the cylinder or the outer cylinder. A tubular free piston that is housed in the reservoir, and a stopper that is attached to either the cylinder or the outer cylinder and slides into contact with the inner circumference of the free piston to form an air chamber between the free piston. It is equipped with a spring element that urges the free piston in the direction of expanding the air chamber. It has a cylinder.

The damper configured in this way allows the reservoir to function as an accumulator, and the volume of the free piston that contributes to the accumulator volume due to movement in the reservoir can be arbitrarily set as long as it is allowed in the reservoir. In addition, the free piston, stopper and spring element that make the reservoir function as an accumulator are housed in the reservoir between the cylinder and the outer cylinder, so it is possible to avoid the damper becoming large and asymmetrical, and the damper is installed. It does not cause interference with other parts when it is installed in the space.

Further, the damper of another invention is provided with a damping passage that allows the flow of the working liquid from the cylinder to the reservoir and gives resistance to the flow of the working liquid, and the outlet end of the damping passage on the reservoir side and the head portion of the free piston. And may face each other. The damper configured in this way can prevent the working liquid discharged from the damping passage to the reservoir during the contraction operation as a jet and enter the cylinder portion, and can prevent the generation of air bubbles in the reservoir.

Further, the damper may include a guide portion in which the spring element is a coil spring and the free piston guides the outer periphery of the coil spring. In this case, the inner peripheral surface where the spring element and the stopper of the free piston are in sliding contact with each other. The free piston can move smoothly with respect to the cylinder over a long period of time.

Further, the damper may have a pair of sliders in which the spring element is mounted on both ends of the coil spring and is in sliding contact with either the cylinder or the outer cylinder. In this case, buckling during compression of the spring element may occur. It is prevented and the free piston can move smoothly in the axial direction with respect to the cylinder for a long period of time.

Further, the damper may apply an initial load to the free piston in a state where the spring element is maximally separated from the free piston and the stopper, and the damper configured in this way can exert a compression side damping force with good responsiveness. ..

According to the damper of the present invention, the characteristics of the accumulator can be easily optimized, and the installation work can be facilitated.

It is sectional drawing of the damper in one Embodiment. It is sectional drawing of the damper in the 1st modification of one Embodiment. It is sectional drawing of the damper in the 2nd modification of one Embodiment.

Hereinafter, the present invention will be described based on the embodiments shown in the figure. As shown in FIG. 1, the damper D1 in one embodiment includes a cylinder 1, a piston 2 that is slidably inserted into the cylinder 1 and divides the inside of the cylinder 1 into an extension side chamber R1 and a compression side chamber R2, and a cylinder. An outer cylinder 4 that is inserted into 1 and is connected to a piston 2 and an outer cylinder 4 that is arranged radially outside the cylinder 1 to form a reservoir R and slides on the outer periphery of the cylinder 1. A cylindrical free piston 5 that is freely mounted, a stopper 6 that is attached to the outer periphery of the cylinder 1 and is slidably contacted with the inner circumference of the free piston 5 to form an air chamber G between the free piston 5 and an air chamber. It is provided with a spring element S that urges the free piston 5 in the direction of expanding G.

Hereinafter, each part of the damper D1 will be described in detail. A valve case 7 is fitted to one end of the cylinder 1, and a rod guide 8 is fitted to the other end. Further, on the radial outer side of the cylinder 1, an outer cylinder 4 that covers the outer periphery of the cylinder 1 and forms a reservoir R that communicates with the cylinder 1 in the cylinder 1 is provided. One end of the outer cylinder 4 is closed by the cap 9, and the other end of the outer cylinder 4 is closed by the rod guide 8. The cylinder 1 is sandwiched by a rod guide 8 mounted on the outer cylinder 4 and a valve case 7 in contact with the cap 9, and is accommodated and fixed in the outer cylinder 4.

Further, the cylinder 1 has an outer peripheral small diameter portion 1a having a small outer diameter from the vicinity of the center to the left end in FIG. 1, and the outer diameter from the outer peripheral small diameter portion 1a to the outer diameter at the right end in FIG. 1 is larger than the outer peripheral small diameter portion 1a. And a step portion 1b is provided.

The piston 2 is slidably inserted into the cylinder 1, and the inside of the cylinder 1 is divided into an extension side chamber R1 and a compression side chamber R2. The extension side chamber R1 and the compression side chamber R2 are each filled with hydraulic oil as a hydraulic fluid. Although the hydraulic liquid is used as the hydraulic oil in this example, it may be used as another liquid such as water or an aqueous solution.

The piston 2 includes a rectifying passage 2a that communicates the extension side chamber R1 and the compression side chamber R2, and a check valve 2b that is installed in the rectification passage 2a and allows only the flow of hydraulic oil from the compression side chamber R2 to the extension side chamber R1. ing.

Further, the valve case 7 includes a small diameter portion 7a fitted in the cylinder 1 and a large diameter portion 7b fitted in the inner circumference of the outer cylinder 4. Further, the valve case 7 is provided in a suction passage 7c and a suction passage 7c which open from the left end in FIG. 1 of the small diameter portion 7a and communicate with the compression side chamber R2 and the reservoir R through the left end in FIG. 1 of the large diameter portion 7b. It is equipped with a check valve 7d that is installed and allows only the flow of hydraulic oil from the reservoir R to the compression side chamber R2.

Further, the rod guide 8 is annular and includes a small diameter portion 8a that fits inside the cylinder 1 and a large diameter portion 8b that fits into the inner circumference of the outer cylinder 4. Further, the rod guide 8 is provided in the discharge passage 8c and the discharge passage 8c which open from the right end in FIG. 1 of the small diameter portion 8a and communicate with the extension side chamber R1 and the reservoir R through the right end in FIG. 1 of the large diameter portion 8b. It is equipped with a damping valve 8d that allows only the flow of hydraulic oil from the extension side chamber R1 to the reservoir R and resists the flow of hydraulic oil that passes through it. Then, in the present embodiment, the damping passage DP is configured by the discharge passage 8c and the damping valve 8d.

One end of the rod 3 is movably inserted into the cylinder 1 through the rod guide 8 and connected to the piston 2, and the other end is projected to the outside of the cylinder 1. In this example, the damper D1 is a so-called single rod type damper in which the rod 3 is inserted only into the extension side chamber R1, but it is also inserted into the compression side chamber R2 and both ends of the rod 3 are on both ends of the cylinder 1. It may be a so-called double-rod type damper that protrudes outward from each other. The damper D1 is provided with brackets 3a and 9a on both the cap 9 and the other ends of the rod 3 so that the damper D1 can be connected to the vibration damping target.

The stopper 6 is annular and includes seal rings 6c and 6d mounted in the annular grooves 6a and 6b provided on the inner circumference and the outer circumference, respectively, and is fitted to the outer periphery of the outer peripheral small diameter portion 1a of the cylinder 1. The cylinder 1 is allowed to move in the axial direction. The stopper 6 is in contact with the step portion 1b provided on the cylinder 1, and the movement of the stopper 6 to the right in FIG. 1 is restricted with respect to the cylinder 1.

The free piston 5 is housed in the reservoir R, and has an annular head portion 5a that is in sliding contact with the outer periphery of the outer peripheral small diameter portion 1a of the cylinder 1 and a cylinder portion 5b extending to the right from the outer periphery of the right end in FIG. 1 of the head portion 5a. And a seal ring 5d mounted on the annular groove 5c provided on the inner circumference of the head portion 5a, and having a tubular shape. When the free piston 5 is mounted on the outer periphery of the outer peripheral small diameter portion 1a of the cylinder 1, the head portion 5a slides on the outer periphery of the outer peripheral small diameter portion 1a, and the inner circumference of the cylinder portion 5b slides on the outer periphery of the stopper 6. It is movable in the axial direction with respect to the cylinder 1 and the stopper 6. Further, an annular stopper collar 10 that abuts on the left end of FIG. 1 of the large diameter portion 8b of the rod guide 8 is mounted on the outer periphery of the outer peripheral small diameter portion 1a of the cylinder 1, and the free piston 5 hits the stopper collar 10. Upon contact, the movement of the free piston 5 to the left in FIG. 1 is restricted. Therefore, the stopper collar 10 determines the movement limit of the free piston 5 to the left in FIG. 1, but instead of the stopper collar 10, a C ring or a pin is attached to the outer periphery of the cylinder 1 to describe the free piston 5. The movement limit may be restricted.

Further, when the free piston 5 and the stopper 6 are mounted on the outer periphery of the cylinder 1 in this way, the air chamber G is formed on the outer periphery of the cylinder 1 between the free piston 5 and the stopper 6. The free piston 5 and the cylinder 1 are sealed by a seal ring 5d, the stopper 6 and the cylinder 1 are sealed by a seal ring 6c, and the free piston 5 and the stopper 6 are sealed by a seal ring 6d. The air chamber G is kept airtight. A gas is sealed in the air chamber G. The outer diameter of the free piston 5 is smaller than the inner diameter of the outer cylinder 4, and a gap is formed between the free piston 5 and the outer cylinder 4 to allow the passage of hydraulic oil.

Further, an annular recess 5e opened at the right end in FIG. 1 is provided on the inner circumference of the head portion 5a. The head portion 5a of the free piston 5 faces the left end of the large diameter portion 8b of the rod guide 8 in FIG. 1 and faces the outlet end on the reservoir R side of the damping passage DP.

The spring element S includes a coil spring 11 and a pair of sliders 12 and 13 fitted to both ends of the coil spring 11, respectively, and is interposed between the head portion 5a of the free piston 5 and the stopper 6. The free piston 5 is urged toward the left in FIG. 1, which is the direction in which the air chamber G is expanded. The spring element S is compressed from its natural length even when the free piston 5 is separated as much as possible, that is, even when the free piston 5 abuts on the stopper collar 10 and movement to the left in FIG. 1 is restricted. The free piston 5 is urged in the direction of expanding the air chamber G. In this way, the spring element S is interposed between the free piston 5 and the stopper 6 in a state where the free piston 5 is in contact with the stopper collar 10 and is compressed more than the natural length. In this state, the free piston S is interposed. An urging force called an initial load is applied to 5. Therefore, the spring element S always urges the free piston 5 in the direction of expanding the air chamber G.

The sliders 12 and 13 are both annular, and the flange portions 12a and 13a abutting on the ends of the coil spring 11 and the sliders 12a and 13a project from the inner circumferences of the flange portions 12a and 13a toward the coil spring 11 side. It is provided with fitting portions 12b and 13b that are fitted to the inner circumference. The sliders 12 and 13 have their inner circumferences in sliding contact with the outer circumference of the outer peripheral small diameter portion 1a of the cylinder 1, and are allowed to slide on the outer circumference of the cylinder 1 and move in the axial direction in the left-right direction in FIG. Cylinder. As described above, since the spring element S includes the sliders 12 and 13 that are in sliding contact with the outer periphery of the cylinder 1, the fitting portions 12b of the sliders 12 and 13 are located between the inner circumference of the coil spring 11 and the outer circumference of the cylinder 1. A gap corresponding to the thickness of 13b is formed. In this way, the sliders 12 and 13 prevent interference between the outer peripheral surface of the outer peripheral small diameter portion 1a, which is the sliding surface on which the free piston 5 of the cylinder 1 slides, and the coil spring 11. Further, the left end of the spring element S in FIG. 1 is inserted into the annular recess 5e of the head portion 5a of the free piston 5, and the coil spring 11 is guided by the head portion 5a when the coil spring 11 is contracted. Buckling is suppressed. Therefore, the head portion 5a of the free piston 5 functions as a guide portion for guiding the coil spring 11, and interference between the coil spring 11 and the inner circumference of the tubular portion 5b of the free piston 5 is prevented.

The damper D1 is configured as described above, and the operation of the damper D1 will be described below. First, the operation when the damper D1 is extended and operated will be described. When the damper D1 is extended and the piston 2 moves to the left in FIG. 1 with respect to the cylinder 1, the extension side chamber R1 is compressed and the volume of the compression side chamber R2 is expanded. Then, the hydraulic oil in the extension side chamber R1 to be compressed passes through the damping passage DP and moves to the reservoir R. Further, hydraulic oil is supplied from the reservoir R to the expanding compression side chamber R2 via the suction passage 7c.

Then, since the damping valve 8d gives resistance to the flow of hydraulic oil from the extension side chamber R1 to the reservoir R via the attenuation passage DP described above, the pressure in the extension side chamber R1 rises, while the compression side chamber R2 has. Equal to the pressure in the reservoir R. Therefore, there is a difference in pressure between the extension side chamber R1 and the compression side chamber R2, and the damper D1 exerts an extension side damping force in a direction that hinders the extension operation corresponding to the pressure difference.

When the damper D1 is extended, the amount of hydraulic oil in the reservoir R decreases because the volume of hydraulic oil that the rod 3 exits from the cylinder 1 is supplied into the cylinder 1, but the free piston 5 is the stopper 6. The volume of the air chamber G is expanded by the volume integral of the hydraulic fluid that is reduced away from the air chamber G. As described above, the volume at which the rod 3 exits from the cylinder 1 during the extension operation of the damper D1 is compensated for the free piston 5 moving in the reservoir R so as to expand the air chamber G.

The operation when the damper D1 contracts and operates will be described. When the damper D1 contracts and the piston 2 moves to the right in FIG. 1 with respect to the cylinder 1, the compression side chamber R2 is compressed and the volume of the extension side chamber R1 is expanded. Then, the hydraulic oil in the compressed side chamber R2 that is compressed pushes open the check valve 2b, passes through the rectifying passage 2a, and moves to the extension side chamber R1. Further, the hydraulic oil for the volume of the rod 3 entering the cylinder 1 becomes excessive in the cylinder 1, and the excess hydraulic oil is discharged to the reservoir R via the damping passage DP. Then, since the damping valve 8d provides resistance to the flow of hydraulic oil from the extension side chamber R1 to the reservoir R via the attenuation passage DP described above, the pressures of the extension side chamber R1 and the compression side chamber R2 both increase equally. .. In the present embodiment, the damper D1 is a single rod type damper, and since the pressure receiving area on the compression side chamber R2 side is larger than the pressure receiving area on the extension side chamber R1 side of the piston 2, it exerts a compression side damping force that hinders the contraction operation. do.

When the damper D1 is contracted, the rod 3 enters the cylinder 1, so that the volume of hydraulic oil that the rod 3 enters the cylinder 1 is discharged from the cylinder 1 to the reservoir R. Therefore, the amount of hydraulic oil increases in the reservoir R, but the free piston 5 approaches the stopper 6 and reduces the volume of the air chamber G by the volume of the increased hydraulic oil. As described above, the volume of the rod 3 entering the cylinder 1 during the contraction operation of the damper D1 is compensated for by the free piston 5 moving in the reservoir R so as to reduce the air chamber G.

The amount of hydraulic oil in the reservoir R is the smallest when the damper D1 is fully extended, and is the largest when the damper D1 is fully contracted. Therefore, in the free piston 5, when the damper D1 is fully extended, the head portion 5a is the farthest from the stopper 6 to maximize the volume of the air chamber G, and when the damper D1 is fully contracted, the head portion 5a is the most to the stopper 6. Get closer and minimize the volume of the air chamber G. The hydraulic oil in the reservoir R is pressurized via the free piston 5 by the elastic force exerted by the gas in the spring element S and the air chamber G. That is, the free piston 5, the stopper 6, the spring element S, and the cylinder 1 allow the reservoir R to function as an accumulator, constantly pressurizing the inside of the cylinder 1 communicating with the reservoir R, and the volume of the rod 3 entering and exiting the cylinder 1. Is compensated.

As described above, the damper D1 of the present invention is inserted into the cylinder 1, the piston 2 which is slidably inserted into the cylinder 1 and separates the extension side chamber R1 and the compression side chamber R2 into the cylinder 1, and the cylinder 1. The rod 3 connected to the piston 2 together with the outer cylinder 4 which is arranged outside the cylinder 1 and covers the cylinder 1 to form a reservoir R which is communicated with the cylinder 1 in the cylinder 1 and the cylinder 1. On the other hand, the air chamber G is between the tubular free piston 5 which is slidably mounted and accommodated in the reservoir R and the free piston 5 which is attached to the cylinder 1 and is slidably contacted with the inner circumference of the free piston 5. It has a stopper 6 for forming the air chamber G and a spring element S for urging the free piston 5 in the direction of expanding the air chamber G.

The damper D1 configured in this way allows the reservoir R to function as an accumulator, and arbitrarily sets the repelling volume of the free piston 5 that contributes to the accumulator volume due to movement in the reservoir R as long as it is allowed in the reservoir R. can. Therefore, in the damper D1 of the present invention, the accumulator volume can be adjusted so that the rod reaction force is appropriate from the maximum extension to the maximum contraction, and the accumulator characteristics can be tuned to be optimum for the damper D1.

Further, since the free piston 5, the stopper 6, and the spring element S that make the reservoir R function as an accumulator are housed in the reservoir R between the cylinder 1 and the outer cylinder 4, the damper D1 becomes large and has an asymmetric shape. This can be avoided, and interference with other parts does not occur when the damper D1 is attached to the installation space. From the above, according to the damper D1 of the present invention, the accumulator characteristics can be easily optimized and the installation work can be easily performed.

Further, in the damper D1 of the present invention, since the free piston 5 and the stopper 6 are mounted on the cylinder 1, the free piston 5 and the stopper 6 are aligned with the cylinder 1, so that the assembly property is good and the cylinder 1 is used. Therefore, in order to make the reservoir R function as an accumulator, it is possible to suppress an increase in the number of parts, so that the damper D1 becomes inexpensive.

In the present embodiment, a small outer peripheral diameter portion 1a is formed on the outer periphery of the cylinder 1 to provide a step portion 1b, and the step portion 1b is brought into contact with the stopper 6 to regulate the separation of the stopper 6 from the free piston 5. ing. Instead of forming the outer peripheral small diameter portion 1a and providing the step portion 1b, a C ring may be attached to the outer periphery of the cylinder 1 and the movement of the stopper 6 may be restricted by the C ring. However, when the cylinder 1 is processed to provide the outer peripheral small diameter portion 1a, there is an advantage that additional parts for restricting the movement of the stopper 6 are not required. Further, when the outer peripheral small diameter portion 1a is provided by grinding, it is not necessary to smooth the sliding surface of the free piston 5 in the cylinder 1.

Further, the damper D1 of the present embodiment is provided with a damping passage DP that allows the flow of hydraulic oil (working liquid) from the cylinder 1 to the reservoir R and gives resistance to the flow of the hydraulic oil (working liquid), and is a free piston. 5 has an annular head portion 5a that slides into contact with the cylinder 1 and a cylinder portion 5b that extends from the head portion 5a and slides into contact with the stopper 6, and has an outlet end on the reservoir R side of the damping passage DP and a head portion 5a of the free piston 5. Are facing each other. When the free piston 5 is mounted in the opposite direction to the arrangement shown in FIG. 1, that is, the head portion 5a is arranged to the right in FIG. 1 and the cylinder portion 5b is arranged to the left in FIG. Install in the opposite direction. In this case, since the stopper 6 and the cylinder portion 5b face the outlet end on the reservoir R side of the damping passage DP, the inside of the cylinder portion 5b in which the hydraulic oil that has passed through the damping passage DP during the contraction operation of the damper D1 becomes a pocket shape is formed. If it becomes a jet and flows vigorously, bubbles may be generated in the cylinder portion 5b. On the other hand, as shown in FIG. 1, in the damper D1 in which the head portion 5a faces the outlet end of the damping passage DP, the hydraulic oil (working liquid) discharged from the damping passage DP to the reservoir R at the time of contraction operation is jetted. Therefore, it can be prevented from entering the tubular portion 5b, and the generation of air bubbles in the reservoir R can be prevented. If there is a sufficient distance between the cylinder portion 5b and the outlet end of the damping passage DP and the hydraulic oil that has passed through the damping passage DP is sufficiently decelerated when entering the cylinder portion 5b, the speed is reduced sufficiently. The tubular portion 5b may be opposed to the outlet end on the reservoir R side of the damping passage DP.

Further, in the damper D1 of the present embodiment, since the spring element S is the coil spring 11 and the free piston 5 includes a guide portion (head portion 5a) for guiding the outer periphery of the coil spring 11, the spring element S. The interference between the free piston 5 and the inner peripheral surface with which the stopper 6 of the free piston 5 is in sliding contact is prevented. Therefore, the free piston 5 can smoothly move in the axial direction with respect to the cylinder 1 over a long period of time.

Further, the damper D1 of the present embodiment has a pair of sliders 12 and 13 in which the spring element S is mounted on both ends of the coil spring 11 and is in sliding contact with the cylinder 1, and the spring element S is buckled during compression. Is prevented. Therefore, the free piston 5 can smoothly move in the axial direction with respect to the cylinder 1 over a long period of time. As shown in FIG. 2, when the total length of the spring element S becomes long, a plurality of coil springs 18 and 19 are connected in series by an intermediate slider 20 that is in sliding contact with the outer periphery of the cylinder 1, and the coil spring 18 and the coil spring are connected. The sliders 12 and 13 may be attached to the ends not connected by the intermediate slider 20 of 19. By doing so, even if the total length of the spring element S is long, it is possible to prevent the coil springs 18 and 19 from bending toward the cylinder 1 and interfering with the outer periphery of the cylinder 1.

Further, in the damper D1 of the present embodiment, the initial load is applied to the free piston 5 with the spring element S in a state where the free piston 5 and the stopper 6 are separated from each other to the maximum extent. In the damper D1 configured in this way, since the inside of the reservoir R is constantly pressurized, the hydraulic oil can be sufficiently supplied from the reservoir R into the compression side chamber R2 which expands when the damper D1 is extended, and the hydraulic oil can be sufficiently supplied in the cylinder 1. Poor suction of hydraulic oil is less likely to occur. Therefore, even when the damper D1 is extended and then contracted, the inside of the cylinder 1 is rapidly boosted, so that the damper D1 can exert a compression side damping force with good responsiveness. Specifically, if a suction failure occurs in the cylinder 1 during the extension operation of the damper D1, the pressure in the cylinder 1 does not easily increase when the damper D1 shifts from the extension operation to the contraction operation, and the compression side damping force is exerted in time. A phenomenon called "running from" occurs, which is delayed, but as described above, when an initial load is applied to the free piston 5, the occurrence of "running from" can be suppressed.

Instead of the configuration of the damper D1 shown in FIG. 1, the free piston 14 and the stopper 15 may be mounted on the inner circumference of the outer cylinder 4 as in the damper D2 of the first modification shown in FIG. .. In this case, the stopper 15 is annular and includes seal rings 15c and 15d that are attached to the inner circumference of the outer cylinder 4 and are attached to the annular grooves 15a and 15b provided on the inner circumference and the outer circumference, respectively. The stopper 15 is restricted from moving to the right in FIG. 3 by a C ring 16 mounted on the inner circumference of the outer cylinder 4.

The free piston 14 has an annular head portion 14a that is in sliding contact with the inner circumference of the outer cylinder 4, a cylinder portion 14b extending from the inner circumference of the right end in FIG. 2 of the head portion 14a to the right in FIG. 3, and an inner circumference of the head portion 14a. It has a tubular shape with a seal ring 14d mounted on the annular groove 14c provided in the above. When the free piston 14 is mounted on the inner circumference of the outer cylinder 4, the head portion 14a slides on the inner circumference of the outer cylinder 4, the outer circumference of the cylinder portion 14b slides on the inner circumference of the stopper 15, and the outer cylinder 4 And it is movable in the axial direction with respect to the stopper 15. Further, a C ring 17 is mounted on the inner circumference of the outer cylinder 4 near the left end in FIG. 3, and when the free piston 14 abuts on the C ring 17, the free piston 14 moves to the left in FIG. Movement is restricted.

Further, when the free piston 14 and the stopper 15 are mounted on the outer periphery of the outer cylinder 4 in this way, an air chamber G is formed between the free piston 14 and the stopper 15 on the inner circumference of the outer cylinder 4. The free piston 14 and the outer cylinder 4 are sealed by a seal ring 14d, the stopper 15 and the outer cylinder 4 are sealed by a seal ring 15c, and the free piston 14 and the stopper 15 are sealed by a seal ring 15d. The air chamber G is kept airtight. A gas is sealed in the air chamber G. The inner diameter of the free piston 14 is smaller than the outer diameter of the cylinder 1, and a gap is formed between the free piston 14 and the cylinder 1 to allow the passage of hydraulic oil. Further, an annular recess 14e opened at the right end in FIG. 3 is provided on the inner circumference of the head portion 14a. The head portion 14a of the free piston 14 faces the left end of the large diameter portion 8b of the rod guide 8 in FIG. 1 and faces the outlet end on the reservoir R side of the damping passage DP.

The spring element S includes a coil spring 21 and sliders 22 and 23 that are fitted and mounted on the outer circumferences of both ends of the coil spring 21 and are in sliding contact with the inner circumference of the outer cylinder 4, and one end thereof is a free piston. It is inserted into the annular recess 14e of the head portion 14a of 14.

As described above, the damper D2 shown in FIG. 3 is inserted into the cylinder 1, the piston 2 which is slidably inserted into the cylinder 1 to partition the extension side chamber R1 and the compression side chamber R2 into the cylinder 1, and the cylinder 1. The outer cylinder 4 which is arranged outside the cylinder 1 and covers the cylinder 1 to form a reservoir R which is communicated with the cylinder 1 in the cylinder 1 and the rod 3 which is connected to the piston 2 at the same time. Between the tubular free piston 14 that is slidably mounted on the cylinder 4 and accommodated in the reservoir R and the free piston 14 that is attached to the outer cylinder 4 and is in sliding contact with the inner circumference of the free piston 14. It has a stopper 15 for forming the air chamber G and a spring element S for urging the free piston 14 in the direction of expanding the air chamber G.

Similar to the damper D1, the damper D2 configured in this way allows the reservoir R to function as an accumulator, and allows the free piston 14 to move away in the reservoir R, which contributes to the accumulator volume, in the reservoir R. It can be set arbitrarily as long as it is. Therefore, in the damper D2 of the present invention, the accumulator volume can be adjusted so that the rod reaction force is appropriate from the maximum extension to the maximum contraction, and the accumulator characteristics can be tuned to be optimum for the damper D2.

Further, since the free piston 14, the stopper 15, and the spring element S that make the reservoir R function as an accumulator are housed in the reservoir R between the cylinder 1 and the outer cylinder 4, the damper D2 becomes large and has an asymmetric shape. This can be avoided, and interference with other parts does not occur when the damper D2 is attached to the installation space. From the above, according to the damper D2 of the present invention, the accumulator characteristics can be easily optimized and the installation work can be easily performed.

Further, in the damper D2 of the present invention, since the free piston 14 and the stopper 15 are mounted on the outer cylinder 4, the free piston 14 and the stopper 15 are aligned with the outer cylinder 4, so that the assembling property is good and the outer cylinder is easy to assemble. Since 4 is used, it is possible to suppress an increase in the number of parts in order to make the reservoir R function as an accumulator, so that the damper D2 is inexpensive.

A large inner diameter portion having a large inner diameter is provided on a part of the inner circumference of the outer cylinder 4, and a free piston 14 and a stopper 15 are attached to the large inner diameter portion to form a boundary between the large inner diameter portions. The movement of the stopper 15 may be restricted by the stepped portion. Further, even in the damper D2, since the head portion 14a faces the outlet end on the reservoir R side of the damping passage DP, it is possible to prevent the generation of air bubbles in the reservoir R.

Further, in the damper D2 of the present embodiment, the spring element S is a coil spring 11, and the left end of the spring element S in FIG. 3 is inserted into the annular recess 14e of the head portion 14a of the free piston 14. When the spring 11 is contracted, the coil spring 11 is guided by the head portion 14a and buckling is suppressed. Therefore, even in this damper D2, since the free piston 14 has a guide portion (head portion 14a) that guides the inner circumference of the coil spring 11, the spring element S and the stopper 15 of the free piston 14 are in sliding contact with each other. Interference with the peripheral surface is prevented. Therefore, the free piston 14 can smoothly move in the axial direction with respect to the cylinder 1 over a long period of time.

Further, the spring element S in the damper D2 of the present embodiment has a pair of sliders 22 and 23 mounted on both ends of the coil spring 11 and slidably contacting the outer cylinder 4, and buckling of the spring element S during compression. Can be prevented. Therefore, the free piston 14 can smoothly move in the axial direction with respect to the cylinder 1 over a long period of time.

Further, even in the damper D2 of the present embodiment, if the spring element S applies the initial load to the free piston 14 in a state where the free piston 14 and the stopper 15 are separated to each other as much as possible, the initial load is applied in the cylinder 1. Poor suction of hydraulic oil is less likely to occur. Therefore, even when the damper D2 is extended and then contracted, the inside of the cylinder 1 is rapidly boosted, so that the damper D2 can exert a compression side damping force with good responsiveness.

Further, in the dampers D1 and D2 of the present embodiment, the spring elements S include the coil springs 11, 18 and 19, but instead, the free pistons 5 and 14 are operated by the pressure of the gas sealed in the air chamber G. The air spring to be urged may be used, or a combination of the coil spring and the air spring may be used as the spring element S. Further, the spring element S may be made of an elastic body such as rubber instead of the coil spring.

As described above, the dampers D1 and D2 are configured as uniflow type dampers in which hydraulic oil circulates in the order of reservoir R, compression side chamber R2, and extension side chamber R1 during expansion / contraction operation. May be done. In the case of a biflow type damper, for example, the extension side passage that abolishes the rectifying passage 2a and gives resistance to the flow of the hydraulic oil from the extension side chamber R1 to the compression side chamber R2 and the hydraulic oil from the compression side chamber R2 to the extension side chamber R1. A pressure side passage that gives resistance to the flow is provided in the piston 2, the damping passage DP of the rod guide 8 is abolished, and a damping passage that gives resistance to the flow of hydraulic oil from the compression side chamber R2 to the reservoir R is provided in the valve case 7. Just do it. In this case, if the head portions 5a and 14a of the free pistons 5 and 14 are arranged toward the valve case 7 side and face the outlet end on the reservoir R side of the damping passage, the generation of air bubbles in the reservoir R can be suppressed. .. The configuration of the biflow type damper described above is an example and may be another configuration, and the structure of the present invention that causes the reservoir R to function as an accumulator can be applied to various dampers.

Although the preferred embodiments of the present invention have been described in detail above, they can be modified, modified and modified as long as they do not deviate from the claims.

1 ... Cylinder, 2 ... Piston, 3 ... Rod, 4 ... Outer cylinder, 5,14 ... Free piston, 5a, 14a ... Head, 5b, 14b ... Cylinder Parts, 6,15 ... Stoppers, 11,18,19,21 ... Coil springs, 12,13,22,23 ... Sliders, D1, D2 ... Dampers, DP ... Damping passages, G ... air chamber, S ... spring element, R ... reservoir, R1 ... extension side chamber, R2 ... compression side chamber

Claims (6)

A cylinder, a piston that is slidably inserted into the cylinder and divides the inside of the cylinder into an extension side chamber and a compression side chamber, a rod that is inserted into the cylinder and is connected to the piston, and the cylinder. A damper having an outer cylinder arranged on the outer side in the radial direction and covering the cylinder to form a reservoir communicating with the cylinder in the cylinder.
A cylindrical free piston that is slidably attached to either the cylinder or the outer cylinder and is accommodated in the reservoir and faces the reservoir.
A stopper attached to either one of the cylinder and the outer cylinder and slidably contacting the inner or outer circumference of the free piston to form an air chamber between the free piston and the free piston.
It is equipped with a spring element that urges the free piston in a direction that expands the air chamber.
During the contraction operation of the damper, the volume of the working liquid in which the rod enters the cylinder is discharged from the cylinder to the reservoir, and the free piston approaches the stopper to be discharged to the reservoir. The volume of the air chamber is reduced by the volume of the working liquid,
During the extension operation of the damper, the volume of the working liquid from which the rod exits from the cylinder is supplied from the reservoir to the cylinder, and the free piston is separated from the stopper to be supplied to the cylinder. Increase the volume of the air chamber by the volume of the working liquid
A damper that is characterized by that. Cylinder and
A piston that is slidably inserted into the cylinder and divides the inside of the cylinder into an extension side chamber and a compression side chamber.
A rod inserted into the cylinder and connected to the piston,
An outer cylinder that is arranged radially outside the cylinder to cover the cylinder and form a reservoir that communicates with the cylinder and communicates with the cylinder.
A cylindrical free piston that is slidably mounted on either the cylinder or the outer cylinder and is housed in the reservoir.
A stopper attached to either one of the cylinder and the outer cylinder and slidably contacting the inner or outer circumference of the free piston to form an air chamber between the free piston and the free piston.
The free piston includes a spring element that urges the free piston in a direction of expanding the air chamber, and the free piston extends from the head portion and an annular head portion that is in sliding contact with either the cylinder or the outer cylinder. A damper characterized by having a cylinder portion that is in sliding contact with the stopper. It is provided with a damping passage that allows the flow of the working liquid from the cylinder to the reservoir and also provides resistance to the flow of the working liquid.
The damper according to claim 2, wherein the outlet end of the damping passage on the reservoir side and the head portion of the free piston face each other. The spring element is a coil spring.
The damper according to any one of claims 1 to 3, wherein the free piston has a guide portion for guiding the inner circumference or the outer circumference of the coil spring. The damper according to claim 4, wherein the spring element has a pair of sliders mounted on both ends of the coil spring and slidably contacting either one of the cylinder and the outer cylinder. The damper according to any one of claims 1 to 5, wherein the spring element applies an initial load to the free piston in a state where the free piston and the stopper are maximally separated from each other.

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