JP2015021602A - Shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shock absorber capable of suppressing generation of a hammering sound caused by collision of a free piston and a housing, and improving a riding quality of a vehicle.SOLUTION: A shock absorber D includes a cylinder 1, a piston 2 defining an expansion-side chamber R1 and a compression-side chamber R2, a housing 6 forming a pressure chamber C, a free piston 9 slidably inserted into the housing 6 and partitioning the pressure chamber C into an expansion-side pressure chamber 7 and a compression-side pressure chamber 8, and a spring element 12 for positioning the free piston 9 on a neutral position with respect to the housing 6, and exhibiting a biasing force for suppressing displacement from the neutral position, of the free piston 9. The shock absorber is further provided with a compression-side elastic member 13 brought into contact with the housing 6 when the free piston 9 is displaced by a prescribed compression-side displacement amount or more to close an orifice hole 11, or an expansion-side elastic member 40 closing an expansion-side passage 10 when the free piston 9 is displaced by a prescribed expansion-side displacement amount or more.

Description

  The present invention relates to an improvement of a shock absorber.

  Conventionally, in this type of shock absorber, a cylinder, a piston that is slidably inserted into the cylinder, and divides the cylinder into an extension side chamber and a pressure side chamber, and an extension side chamber and a pressure side chamber provided in the piston communicate with each other. A damping passage, a housing attached to the tip of the piston rod to form a pressure chamber, a free piston that is slidably inserted into the pressure chamber and divides the pressure chamber into an expansion side pressure chamber and a pressure side pressure chamber, and free Some are configured to include a coil spring for energizing the piston, an extension side passage that communicates the extension side chamber and the extension side pressure chamber, and a pressure side passage that communicates the pressure side chamber and the pressure side pressure chamber.

  In the shock absorber configured as described above, the pressure chamber is divided into an expansion side pressure chamber and a pressure side pressure chamber by a free piston, and the extension side chamber and the pressure side chamber are directly connected to each other via the extension side passage and the pressure side passage. However, when the free piston moves, the volume ratio between the expansion side chamber and the compression side chamber changes, and the liquid in the pressure chamber moves into and out of the expansion side chamber and the compression side chamber according to the amount of movement of the free piston. In addition, the extension side chamber and the pressure side chamber behave as if they are communicated with each other via the extension side passage and the pressure side passage.

  For this reason, this shock absorber can generate a high damping force for low-frequency vibration input, and can generate a low damping force for high-frequency vibration input. It is possible to generate a high damping force in a scene where the input vibration frequency of the vehicle is low, and reliably generate a low damping force in a scene where the input vibration frequency is high such that the vehicle passes through the road surface unevenness. Comfort can be improved (for example, refer patent document 1).

JP 2008-215462 A

  However, in the conventional shock absorber, when the free piston is displaced in the direction of compressing the pressure side pressure chamber, the free piston is brought into contact with a step provided on the inner periphery of the housing to restrict the movement limit of the free piston. In addition, when the free piston is displaced in the direction of compressing the expansion side pressure chamber, the upper end of the free piston cylinder abuts against the flange of the inner cylinder that constitutes the housing, thereby restricting the movement limit of the free piston. Therefore, when the free piston collides with the housing vigorously, a hitting sound is generated, and this hitting sound reverberates through the vehicle body, causing the passenger to perceive abnormal noise and impairing the ride comfort in the vehicle. There is.

  Therefore, the present invention was devised in order to improve the above-described problems, and the object of the present invention is to suppress the generation of hitting sound due to the collision between the free piston and the housing, and to improve the riding comfort in the vehicle. It is to provide a shock absorber that can be improved.

  In order to solve the above-described object, the problem-solving means in the present invention includes a cylinder, a piston that is slidably inserted into the cylinder and divides the cylinder into an extension side chamber and a pressure side chamber, the extension side chamber, and the above A damping passage communicating with the pressure side chamber, a housing forming a pressure chamber, a free piston that is slidably inserted into the housing and divides the pressure chamber into an extension side pressure chamber and a pressure side pressure chamber, and An extension side passage communicating the extension side chamber and the extension side pressure chamber, an orifice hole provided in the housing for communicating the pressure side chamber and the pressure side pressure chamber, and the free piston in a neutral position with respect to the housing And a spring element that exerts an urging force that suppresses displacement from the neutral position of the free piston and is mounted on the free piston. A pressure-side elastic member that contacts the housing and closes the orifice hole when the free piston is displaced by a predetermined amount or more in the direction of compressing the pressure-side pressure chamber from the neutral position with respect to the housing; Features.

  In order to solve the above-described object, another problem-solving means in the present invention includes a cylinder, a piston that is slidably inserted into the cylinder, and divides the cylinder into an extension side chamber and a pressure side chamber, and the above A damping passage communicating the extension side chamber and the pressure side chamber, a housing forming a pressure chamber, and a free inserted into the housing to slidably divide the pressure chamber into an extension side pressure chamber and a pressure side pressure chamber A piston, an extension passage for communicating the extension side chamber and the extension side pressure chamber, an orifice hole provided in the housing for communicating the pressure side chamber and the pressure side pressure chamber, and the free piston to the housing. A shock absorber comprising a spring element that is positioned at a neutral position and that exerts an urging force that suppresses displacement from the neutral position of the free piston. An extension side elastic member is provided that closes the extension side passage when the free piston is displaced by a predetermined extension side displacement amount or more in the direction of compressing the extension side pressure chamber from the neutral position with respect to the housing. It is characterized by.

  In this shock absorber, when the freepist is displaced by a predetermined amount or more on the compression side in the direction of compressing the compression side pressure chamber or the expansion side pressure chamber, or when it is displaced by a predetermined amount or more on the expansion side, the compression side elastic member or the expansion side elastic member Contacts the housing and closes the orifice hole or the extension side passage. When the orifice hole is closed in this way, the pressure side pressure chamber is compressed against the displacement of the free piston, the internal pressure rises, and the displacement in the direction of compressing the pressure side pressure chamber of the free piston is suppressed, Collision between the free piston and the housing is prevented. Also, when the expansion side passage is closed, the expansion side pressure chamber is compressed and the internal pressure rises against the displacement of the free piston, and the displacement of the free piston in the direction of compressing the expansion side pressure chamber is suppressed. Thus, the collision between the free piston and the housing is prevented.

  According to the shock absorber of the present invention, it is possible to provide a shock absorber capable of suppressing the occurrence of a hitting sound due to a collision between the free piston and the housing and improving the riding comfort in the vehicle.

It is a longitudinal cross-sectional view of the shock absorber in one embodiment. It is a longitudinal cross-sectional view of the shock absorber in one modification of one embodiment. It is a longitudinal cross-sectional view of the buffering device in the other modification of one Embodiment. It is a longitudinal cross-sectional view of the buffering device in another modification of one Embodiment.

  Hereinafter, the present invention will be described with reference to the drawings. As shown in FIG. 1, a shock absorber D according to an embodiment of the present invention is slidably inserted into a cylinder 1 and the cylinder 1 and divides the cylinder 1 into two extension side chambers R1 and a pressure side chamber R2. The piston 2, the damping passages 4 and 5 communicating with the extension side chamber R1 and the pressure side chamber R2, the housing 6 forming the pressure chamber C, and the pressure chamber C are slidably inserted into the housing 6. A free piston 9 that partitions the expansion side pressure chamber 7 and the compression side pressure chamber 8, an expansion side passage 10 that communicates the expansion side chamber R1 and the expansion side pressure chamber 7, and a pressure side chamber R2 and a pressure side pressure provided in the housing 6. An orifice hole 11 that communicates with the chamber 8, a spring element 12 that positions the free piston 9 in a neutral position with respect to the housing 6 and that exerts a biasing force that suppresses displacement from the neutral position of the free piston 9; Emissions 9 is configured to include a compression side elastic member 13 for closing the orifice hole 11 in contact with the housing 6 when displaced neutral position predetermined pressure side displacement amount or more to the pressure side the pressure chamber side from the housing 6.

  The shock absorber D includes a piston rod 3 that is movably inserted into the cylinder 1. One end of the piston rod 3 is connected to the piston 2, and the upper end that is the other end is not shown. The cylinder 1 is slidably supported by an annular rod guide that seals the upper end of the cylinder 1. Note that the lower end of the cylinder 1 is sealed by a bottom member (not shown).

  The extension side chamber R1, the pressure side chamber R2, and the pressure chamber C are filled with a liquid such as hydraulic oil. Although not shown, the cylinder 1 slides on the inner periphery of the cylinder 1 in the lower part of the figure. A sliding partition is provided in contact with the pressure side chamber R2 and the gas chamber. In addition to the hydraulic fluid, for example, a liquid such as water or an aqueous solution can be used as the liquid filled in the extension side chamber R1, the pressure side chamber R2, and the pressure chamber C.

  Since the shock absorber D is a single rod type in which the piston rod 3 is inserted only into the expansion side chamber R1, the volume of the piston rod 3 that goes in and out of the cylinder 1 as the shock absorber D expands and contracts is as follows. The volume of the gas in the gas chamber G expands or contracts and the sliding partition wall 17 moves in the vertical direction in FIG. For compensation of the volume by which the piston rod 3 advances and retreats to and from the cylinder 1, in addition to providing the gas chamber G in the cylinder 1, a reservoir may be provided in the cylinder 1 or outside the cylinder 1. In this case, an outer cylinder that covers the outer periphery of the cylinder 1 is provided to form a double cylinder type shock absorber that forms a reservoir between the cylinder 1 and the outer cylinder, and a tank is provided separately from the cylinder 1 A reservoir may be formed. When a reservoir is provided, a partition member that partitions the pressure side chamber R2 and the reservoir in order to increase the pressure in the pressure side chamber R2 during the contraction operation of the shock absorber D, and a partition member that is provided on the partition member and heads from the pressure side chamber R2 toward the reservoir. A base valve that provides resistance to the flow of liquid may be provided. Further, the shock absorber D may be set to a double rod type instead of a single rod type.

  Hereinafter, each part of the shock absorber D will be described in detail. The piston 2 is connected to one end 3a which is a lower end in FIG. 1 of a piston rod 3 which is movably inserted into the cylinder 1, and the piston rod 3 is an annular rod (not shown) fixed to the upper end of the cylinder 1 in the drawing. It protrudes outward through the inner circumference of the guide. The piston rod 3 and the rod guide (not shown) are sealed by a seal member (not shown), and the cylinder 1 is kept in a liquid-tight state.

  Further, the piston 2 is provided with damping passages 4 and 5 that connect the expansion side chamber R1 and the pressure side chamber R2, and a leaf valve V2 in which the lower end of the damping passage 4 in FIG. The upper end of the damping passage 5 in FIG. 1 is opened and closed by a leaf valve V1 stacked on the upper side of the piston 2 in FIG. The leaf valve V2 is annular and attached to the one end 3a of the piston rod 3 together with the piston 2, so that the liquid extends through the damping passage 5 during the expansion stroke of the shock absorber D in which the piston 2 moves upward in FIG. When it flows from the side chamber R1 toward the pressure side chamber R2, it bends and opens the attenuation passage 5 and gives resistance to the flow of the liquid, and closes the attenuation passage 5 against the reverse flow. The damping passage 5 is set as a one-way passage that allows only the flow from the extension side chamber R1 to the compression side chamber R2. On the other hand, the leaf valve V1 is annular and is attached to the one end 3a of the piston rod 3 together with the piston 2, so that the liquid passes through the damping passage 4 during the contraction stroke of the shock absorber D in which the piston 2 moves downward in FIG. When the fluid flows from the chamber R2 toward the extension side chamber R1, it bends to open the attenuation passage 4 and provides resistance to the flow of the liquid, and closes the attenuation passage 4 against the reverse flow. The damping passage 4 is set as a one-way passage that allows only the flow from the compression side chamber R2 to the extension side chamber R1. That is, the leaf valve V2 functions as an expansion-side attenuation valve that provides resistance to the flow of liquid flowing through the attenuation passage 5 during the expansion stroke, and the leaf valve V1 provides resistance to the flow of liquid that flows through the attenuation passage 4 during the contraction stroke. Functions as a compression side damping valve. As described above, when a plurality of attenuation passages 4 and 5 are provided, the attenuation passage may be set to be one-way so that the liquid flows only during the extension stroke or during the contraction stroke. The passage may allow bidirectional flow and provide resistance to the flow of liquid passing therethrough. Various damping valves such as a poppet valve, an orifice, and a choke can be used as a damping valve that serves as a damping passage that gives resistance to the flow of liquid passing through the damping passage. The damping passages 4 and 5 can be provided in addition to the piston 2.

  Subsequently, in the case of this embodiment, the pressure chamber C is formed by a hollow housing 6 that is screwed into a screw portion 3b provided on the outermost outer periphery of the one end 3a of the piston rod 3. The piston 2 and the leaf valves V1 and V2 also function as a piston nut that fixes the one end 3a of the piston rod 3.

  The pressure chamber C formed in the housing 6 is a free piston 9 that is slidably inserted into the pressure chamber C. The expansion side pressure chamber 7 at the upper side in FIG. 1 and the pressure side pressure chamber at the lower side in FIG. 1, and the free piston 9 can be displaced in the vertical direction in FIG. 1 with respect to the housing 6 in the pressure chamber C.

  Specifically, the housing 6 includes a nut portion 20 that is screwed into a screw portion 3 b formed at one end 3 a of the piston rod 3, a cylindrical portion 22 that is suspended from the outer periphery of the nut portion 20, and an end portion of the cylindrical portion 22. In FIG. 1, a bottomed cylindrical housing cylinder 21 having a bottom 23 that closes the lower end is provided, and a pressure chamber C is defined in the compression side chamber R2.

  The nut portion 20 includes a screw cylinder 20a that is screwed onto the outer periphery of the screw portion 3b of the piston rod 3, and a flange 20b that is provided on the outer periphery of the screw cylinder 20a and protrudes outward.

  The housing cylinder 21 has a bottomed cylindrical shape as described above, and is integrated with the nut portion 20 by caulking the upper end opening in FIG. 1 toward the outer periphery of the flange 20b of the nut portion 20. . More specifically, the housing cylinder 21 includes a cylindrical portion 22 that hangs down from the flange 20b, and a bottom portion 23 that closes the end of the cylindrical portion 22, and has a bottomed cylindrical shape. The cylindrical portion 22 is formed on the nut portion side between the large-diameter portion 22a slidably contacting the free piston 9, the small-diameter portion 22b on the counter-nut portion side, and the large-diameter portion 22a and the small-diameter portion 22b. The step part 22c formed in this is provided. In addition, when the nut portion 20 and the housing cylinder 21 are integrated, other processing directions such as welding and screwing can be adopted in addition to the caulking processing. Further, the outer peripheral cross-sectional shape of at least a part of the cylindrical portion 22 of the housing cylinder 21 is a shape other than a circle so as to be gripped by a tool (not shown) and matches the tool, for example, a shape in which a part is notched. Or a hexagonal shape, and the housing 6 is rotated in the circumferential direction by gripping the outer periphery of the cylindrical portion 22 with a tool, and a predetermined tightening torque is applied to the nut portion 20 to screw into the screw portion 3b. You can wear it.

  In addition, the bottom 23 of the housing cylinder 21 is provided with an orifice hole 11 penetrating the bottom 23 in the axial direction, and the pressure side chamber R2 is communicated with the pressure chamber C through the orifice hole 11. Further, the cylinder portion 22 is provided with a variable orifice 22d that opens from the outer periphery and communicates with the inner periphery of the inner diameter large diameter portion 22b, and the pressure chamber C and the pressure side chamber R2 communicate with each other through the variable orifice 22d. .

  The expansion side pressure chamber 7 communicates with the expansion side chamber R1 by an expansion side passage 10 that leads from the side of the piston rod 3 facing the expansion side chamber R1 to the end of the one end 3a. The extension side passage 10 is composed of a horizontal hole 10a that opens from the side facing the extension side chamber R1 of the piston rod 3, and a vertical hole 10b that opens from the end of one end 3a and communicates with the horizontal hole 10a.

  The free piston 9 inserted into the pressure chamber C includes a sliding contact cylinder 30 that is in sliding contact with the inner diameter large diameter portion 22a of the cylindrical portion 22 of the housing cylinder 21, a bottom portion 31 that closes the lower end of the sliding contact cylinder 30, and A through hole 31 a provided in the bottom 31 and an annular groove 31 b provided in the bottom 31 so as to surround the through hole 31 a are provided.

  The compression-side elastic member 13 is formed of an elastic material such as synthetic resin or rubber, and includes a flange 13a fitted in an annular groove 31b provided at the lower end of the bottom 31 of the free piston 9 in FIG. It is comprised with the bottomed cylindrical cushion 13b which protrudes from the periphery and protrudes in the pressure side pressure chamber 8. As shown in FIG. The cushion 13b may be solid rather than cylindrical, but material costs can be reduced by making it cylindrical.

  Furthermore, in order to apply an urging force that suppresses the displacement of the free piston 9 relative to the housing 6, the flange 20 b of the nut portion 20 and the upper end of the bottom portion 31 of the free piston 9 are provided in the extension side pressure chamber 7. Coil springs as spring elements 12 between the flange portion 13a of the compression-side elastic member 13 in the compression-side pressure chamber 8 and fitted in the annular groove 31b of the bottom portion 31 and the bottom portion 31, respectively. A certain extension side coil spring 34 and compression side coil spring 35 are both interposed in a compressed state. Thus, the free piston 9 is sandwiched from above and below by the extension side coil spring 34 and the compression side coil spring 35 and is positioned at a predetermined neutral position in the pressure chamber C. When the free piston 9 is displaced from the neutral position, the extension side coil The spring 34 and the compression side coil spring 35 exert an urging force to return the free piston 9 to the neutral position. The neutral position does not indicate the axial center of the pressure chamber C, but a position where the free piston 9 is positioned by the spring element 12.

  When the free piston 9 is sandwiched between the extension side coil spring 34 and the compression side coil spring 35 in this way, the flange 13a of the compression side elastic member 13 is pressed toward the bottom 31 of the free piston 9, so the free piston 9 and the compression side elastic member 13 can be moved together in the housing 6. In addition, as the spring element 12, it is only necessary to position the free piston 9 at the neutral position and to exert an urging force, so that other than the coil spring may be employed. For example, an elastic body such as a disc spring is used. The free piston 9 may be elastically supported.

  Further, the through hole 31 a provided in the bottom 31 of the free piston 9 is closed by the compression side elastic member 13, so that the compression side chamber C is divided into the expansion side pressure chamber 7 and the compression side pressure chamber 8 by the free piston 9. Can do. In the case of the shock absorber D of this embodiment, the flange 13a is fitted in the annular groove 31b, so that the compression side elastic member 13 is not positioned in the radial direction with respect to the free piston 9 so as not to be displaced. Therefore, it is considered that the compression side elastic member 13 is not displaced with respect to the free piston 9 and the extension side pressure chamber 7 and the compression side pressure chamber 8 are not communicated with each other.

  Although the through hole 31a can be eliminated, the inside of the cushion 13b of the compression side elastic member 13 communicates with the expansion side pressure chamber 7 through the through hole 31a of the bottom 31 of the free piston 9, and thus into the shock absorber D. When the liquid is injected, no gas is left in the cushion 13b, and bubbles are left in the shock absorber D, so that the responsiveness of the generation of the damping force is not deteriorated.

  Returning, the sliding cylinder 30 of the free piston 9 is provided with an annular recess 30a formed in the outer periphery along the circumferential direction and a through hole 30b that opens from the lower end and communicates with the annular recess 30a. Is in the neutral position, the annular recess 30a faces the variable orifice 22d formed in the cylindrical portion 22 of the housing 6, so that the pressure side chamber R2 and the pressure side pressure chamber 8 communicate with each other through the orifice hole 11, and the through hole 30b and annular The pressure side chamber R2 communicates with the pressure side pressure chamber 8 also by the recess 30a and the variable orifice 22d.

  The variable orifice 22d provides resistance to the flow of liquid passing therethrough to cause a predetermined pressure loss, and generates a differential pressure between the pressure side chamber R2 and the pressure side pressure chamber 8. .

  In addition, the orifice hole 11 provided in the bottom 23 of the housing cylinder 21 also functions as a constriction passage, which gives a resistance to the flow of liquid passing therethrough and causes a predetermined pressure loss. A differential pressure is generated between the pressure side pressure chamber 8 and the pressure side pressure chamber 8.

  When the free piston 9 is displaced from the neutral position in the direction of compressing the expansion side pressure chamber 7 or the compression side pressure chamber 8, the degree of lap between the variable orifice 22d and the annular recess 30a gradually increases as the displacement progresses. When the pressure decreases and eventually displaces to the vicinity of the stroke end, the variable orifice 22d does not face the annular recess 30a and is closed by the sliding contact cylinder 30. In this state, the pressure side pressure chamber 8 is closed to the orifice hole 11. Only the pressure side chamber R2 is communicated. Therefore, when the free piston 9 is displaced from the neutral position and the variable orifice 22d begins to be closed by the free piston 9, the total flow area of the passage communicating the pressure side chamber R2 and the pressure side pressure chamber 8 starts to decrease, and the free piston 9 Further displacement of the piston 9 toward the stroke end can be suppressed.

  In this way, the expansion side chamber R1 and the expansion side pressure chamber 7 are communicated with each other by the expansion side flow channel 10, and the pressure side chamber R2 and the pressure side pressure chamber 8 are communicated with each other through the pressure side flow channel formed by the variable orifice 22d and the orifice hole 11. Since the volume of the expansion side pressure chamber 7 and the compression side pressure chamber 8 changes as the free piston 9 is displaced in the housing 6, the above-described expansion side flow path 10, expansion side pressure is applied to the shock absorber D. A channel composed of the chamber 7, the pressure side pressure chamber 8, and the pressure side channel apparently communicates the extension side chamber R 1 and the pressure side chamber R 2, and the extension side chamber R 1 and the pressure side chamber R 2 are connected to the attenuation passage 4 and the attenuation passage 5. In addition, communication is also performed by the above-described apparent flow path.

  The amount of displacement from the neutral position at which the free piston 9 begins to close the variable orifice 22d can be arbitrarily set, and the expansion side pressure chamber located above the free piston 9 in FIG. 1 starting to close the variable orifice 22d. The displacement amount from the neutral position to the 7 side and the displacement amount from the neutral position to the pressure side pressure chamber 8 side of the free piston 9 starting to close the variable orifice 22d in FIG. 1 are set differently. Also good. In this embodiment, two variable orifices 22d are provided, but the number thereof is arbitrary, and an annular recess communicated with the pressure side chamber R2 is provided on the inner periphery of the cylindrical portion 22, A variable orifice communicating with the pressure side pressure chamber 8 may be provided in the free piston 9.

  Further, when the free piston 9 is displaced from the neutral position by a predetermined pressure side displacement amount or more, the bottom portion of the cushion 13b of the compression side elastic member 13 comes into contact with the bottom portion 23 of the housing 6 to close the orifice hole 11. The pressure side displacement amount can be arbitrarily set as long as it is within the range of the displacement amount that can be stroked when the free piston 9 is displaced from the neutral position in the direction of compressing the pressure side pressure chamber 8.

  Next, the basic operation of the shock absorber D will be described. When the shock absorber D exhibits an extension operation in which the piston 2 moves upward in FIG. 1 with respect to the cylinder 1, the extension side chamber R1 is compressed by the piston 2 and the compression side chamber R2 is expanded, so that the pressure in the extension side chamber R1 is increased. At the same time, the pressure in the pressure side chamber R2 decreases and a differential pressure is generated between the two, so that the liquid in the expansion side chamber R1 moves to the pressure side chamber R2 through the damping passage 5, and the pressure on the expansion side is higher than the pressure side pressure chamber 8. Since the pressure in the chamber 7 is increased and the free piston 9 is displaced in the housing 6 in a direction in which the compression side pressure chamber 8 is compressed, the expansion side flow path 5, the expansion side pressure chamber 7, the pressure side pressure chamber 8, and the pressure side flow path It moves to the pressure side chamber R2 through the apparent flow path.

  On the other hand, when the shock absorber D exhibits a contraction operation in which the piston 2 moves downward in FIG. 1 with respect to the cylinder 1, the compression side chamber R2 is compressed by the piston 2 and the expansion side chamber R1 is expanded. At the same time as the pressure in R2 increases, the pressure in the expansion side chamber R1 decreases and a differential pressure occurs between the two, and the liquid in the compression side chamber R2 moves to the expansion side chamber R1 through the damping passage 4 and from the expansion side pressure chamber 7 Since the pressure of the pressure side pressure chamber 8 is increased and the free piston 9 is displaced in the direction of compressing the expansion side pressure chamber 7 in the housing 6, the expansion side flow path 10, the expansion side pressure chamber 7, the pressure side pressure chamber 8 and It moves to the extension side chamber R1 through the apparent flow path consisting of the pressure side flow path.

  Here, when the piston speed in the shock absorber D is the same regardless of whether the vibration frequency input to the shock absorber D, that is, the expansion and contraction vibration frequency of the shock absorber D is low or high, the low The amplitude of the shock absorber D at the time of high frequency vibration input is larger than the amplitude of the shock absorber D at the time of high frequency vibration input. Thus, when the frequency of the vibration input to the shock absorber D is low, the amplitude is large, so that the flow rate of the liquid flowing between the expansion side chamber R1 and the compression side chamber R2 increases in one expansion / contraction cycle. Although the displacement of the free piston 9 increases substantially in proportion to the flow rate, the free piston 9 is biased by the spring element 12, so that when the displacement of the free piston 9 increases, the spring element received by the free piston 9 The energizing force from 12 also increases, and accordingly, a differential pressure is generated between the pressure in the expansion side pressure chamber 7 and the pressure in the compression side pressure chamber 8, and the differential pressure between the expansion side chamber R1 and the expansion side pressure chamber 7 and the pressure side chamber R2 The differential pressure in the pressure side pressure chamber 8 is reduced, and the flow rate passing through the apparent flow path is reduced. Since the flow rate of the attenuation passage 4 or the attenuation passage 5 is increased by the small flow rate passing through the apparent flow path, the damping force generated by the shock absorber D is maintained high.

  Conversely, when high-frequency vibration is input to the shock absorber D, the amplitude is smaller than when low-frequency vibration is input, so the flow rate of the liquid flowing between the expansion-side chamber R1 and the compression-side chamber R2 in one expansion / contraction cycle is small, and the free piston 9 The moving displacement is also reduced. Then, the biasing force is also reduced from the spring element 12 received by the free piston 9. Accordingly, the pressure in the expansion side pressure chamber 7 and the pressure in the compression side pressure chamber 8 become substantially equal, and the differential pressure between the expansion side chamber R1 and the expansion side pressure chamber 7 and the differential pressure between the compression side chamber R2 and the compression side pressure chamber 8 are low frequency. It becomes larger than that at the time of vibration input, and the flow rate passing through the above apparent flow path is increased compared to that at the time of low frequency vibration input. Since the flow rate of the damping passage 4 or the damping passage 5 decreases as the flow rate passing through the apparent flow path increases, the damping force generated by the shock absorber D is the damping force when the low frequency vibration is input. Smaller than.

  Thus, the shock absorber D can generate a large damping force for vibrations in the low frequency range, and can reduce the damping force for vibrations in the high frequency range, depending on the input vibration frequency. A damping force suitable for the vehicle can be generated.

  Further, when the free piston 9 is displaced from the neutral position until the variable orifice hole 22d is closed, the flow resistance of the pressure side passage gradually increases from the start of closing the variable orifice 22d until it is completely closed. The moving speed of the piston 9 toward the stroke end side is reduced, and the moving amount of the liquid between the extension side chamber R1 and the pressure side chamber R2 through the apparent flow path is also reduced. The amount of liquid passing through 5 increases, and the generated damping force of the shock absorber D gradually increases regardless of the vibration frequency. Therefore, when the displacement from the neutral position of the free piston 9 is large and closes the variable orifice 22d, the displacement of the free piston 9 toward the stroke end is suppressed, and the shock absorber D is low when high-frequency vibration is input. It is prevented that the damping force is suddenly switched from a state where the damping force is generated to a high damping force, and it is not necessary for the passenger to perceive a shock due to a change in the damping force.

  Further, when the free piston 9 is displaced by a predetermined amount or more downward in FIG. 1 where the compression side pressure chamber 8 is compressed, the bottom portion of the cushion 13b in the compression side elastic member 13 provided on the free piston 9 comes into contact with the bottom portion 23 of the housing 6. The orifice hole 11 is closed while suppressing further displacement of the free piston 9 downward in FIG.

  When the orifice hole 11 is closed, the communication between the pressure-side pressure chamber 8 and the pressure-side chamber R2 is cut off, and the pressure-side pressure chamber 8 is compressed in response to further displacement of the free piston 9 downward in FIG. The pressure rises to suppress the downward displacement of the free piston 9 in FIG. 1 and the collision between the free piston 9 and the housing 6 is prevented. When the compression side elastic member 13 closes the orifice hole 11, the variable orifice 22d may be in a state where the compression side chamber R2 and the compression side pressure chamber 8 communicate with each other so as to face the annular recess 30a. In this case, since the variable orifice 22d is effective even if the orifice hole 11 is closed, the free piston 9 can be displaced in the direction of compressing the pressure side pressure chamber 8 while compressing the cushion 13b. When the displacement progresses, the variable orifice 22d is also cut off, the communication between the pressure side pressure chamber 8 and the pressure side chamber R2 is cut off, and the displacement of the free piston 9 in the direction of compressing the pressure side pressure chamber 8 beyond that is prevented. . Therefore, the collision between the free piston 9 and the housing 6 is prevented.

  From the above, according to the shock absorber D of the present invention, the collision between the free piston 9 and the housing 6 can be prevented, the occurrence of the hitting sound of both can be suppressed, and the vehicle occupant can be prevented from perceiving the hitting sound. Riding comfort in the vehicle can be improved without causing the passenger to feel uneasy or uncomfortable.

  In order to integrate the free piston 9 and the pressure side elastic member 13, the pressure side elastic member 13 can be disposed without interfering with the inner peripheral side of the pressure side coil spring 35 by using the pressure side coil spring 35.

  In addition, as described above, when the free piston 9 is displaced in the direction of compressing the pressure side pressure chamber 8, the pressure side elastic member 13 is brought into contact with the housing 6 so as to close the orifice hole 11. Although the displacement in the direction in which the compression side pressure chamber 8 is compressed is suppressed, as shown in FIG. 2, the extension side elastic member 40 is provided, and the free piston 9 compresses the extension side pressure chamber 7 from the neutral position. When the displacement is greater than or equal to the extension side displacement amount, the extension side elastic member 40 is brought into contact with the lower end surface in FIG. You may make it suppress the displacement of the direction which compresses the side pressure chamber 7. FIG.

  The expansion side elastic member 40 includes a flange 40a and a cushion 40b that rises from the flange 40a and protrudes into the expansion side pressure chamber 7 through the through hole 31a. The flange 40a is fitted in the annular groove 31b of the free piston 9, the flange 13a of the compression side elastic member 13 is overlapped under the flange 40a, and the flange 40a and the flange 13a are sandwiched between the compression side coil spring 35 and the free piston 9. Thus, the extension side elastic member 40 and the compression side elastic member 13 are fixed to the free piston 9.

  By doing in this way, the expansion side elastic member 40 can be easily fixed to the free piston 9 together with the compression side elastic member 13. The cushions 13b and 40b may be solid instead of cylindrical, but the material cost can be reduced by making them cylindrical.

  When the free piston 9 is displaced from the neutral position by a predetermined extension side displacement amount or more, the top of the cushion 40b of the extension side elastic member 40 comes into contact with the distal end surface of the piston rod 3 and the vertical hole 10b of the extension side passage 10 is reached. If the free piston 9 is displaced from the neutral position in the direction of compressing the expansion side pressure chamber 7, the expansion side displacement amount is arbitrarily set within the range of the displacement amount that can be stroked. can do.

  Therefore, in the case of this shock absorber D, when the free piston 9 is displaced downward in FIG. 2 where the compression side pressure chamber 8 is compressed, the compression side elastic member 13 not only prevents the collision between the free piston 9 and the housing 6. 2, when the free piston 9 compresses the expansion side pressure chamber 7 upward in FIG. 2 by a predetermined amount or more, the expansion side passage 10 is closed and the communication between the expansion side pressure chamber 7 and the expansion side chamber R1 is cut off. Therefore, with respect to the further displacement of the free piston 9 upward in FIG. 2, the expansion side pressure chamber 7 is compressed and the internal pressure rises, and the upward displacement of the free piston 9 in FIG. 2 is suppressed. The collision between the free piston 9 and the housing 6 is prevented. In addition, when the expansion side elastic member 40 closes the expansion side passage 10, the variable orifice 22d may be in a state where the compression side chamber R2 and the compression side pressure chamber 8 communicate with each other so as to face the annular recess 30a. The orifice hole 11 may be closed.

  From the above, according to the shock absorber D of the present invention, the collision between the free piston 9 and the housing 6 can be prevented, the occurrence of the hitting sound of both can be suppressed, and the vehicle occupant can be prevented from perceiving the hitting sound. Riding comfort in the vehicle can be improved without causing the passenger to feel uneasy or uncomfortable.

  In order to integrate the free piston 9 and the expansion side elastic member 40, the expansion side coil spring 34 and the compression side coil spring 35 are used so that the expansion side coil spring 34 and the compression side coil spring 35 are connected to the inner peripheral side thereof. The extension side elastic member 40 and the compression side elastic member 13 can be arranged without interfering with each other.

  Further, when the extension side elastic member 40 is fixed to the free piston 9, in the case of the free piston 9, as shown in FIG. 3, the through hole 31a is surrounded on the extension side pressure chamber side of the bottom 31 of the free piston 9. An annular groove 31c is provided, and the flange 40a is fitted into the annular groove 31c of the free piston 9, and the flange 40a is sandwiched between the free piston 9 and the extension side coil spring 34, whereby the free piston 9 is elastically extended. The member 40 may be fixed.

  Further, as shown in FIG. 4, the annular groove 31b is abolished, and the flange 40a and the flange 13a of the extension side elastic member 40 and the compression side elastic member 13 are overlapped and fitted into the annular groove 31c. The extension side elastic member 40 and the compression side elastic member 13 may be fixed to the free piston 9 by sandwiching the extension side coil spring 34 and the free piston 9.

 In the above description, the present invention has been described with reference to an example in which the compression side elastic member 13 is provided. However, in FIG. 3, only the annular groove 31c is provided in the bottom 31 of the free piston 9, and the compression side elastic member 13 and the through hole 31a are provided. In the case where only the expansion side elastic member 40 is provided by eliminating the annular groove 31b and the free piston 9 is displaced by a predetermined amount or more in the direction of compressing the expansion side pressure chamber 7, the expansion side passage 10 is expanded. If the elastic member 40 closes the communication between the expansion side pressure chamber 7 and the expansion side chamber R1 to prevent the free piston 9 and the housing 6 from colliding with each other, the shock absorber D is extended during the expansion operation. Generation of a hitting sound can be suppressed, the vehicle occupant can be prevented from perceiving the hitting sound, the passenger can be prevented from feeling uneasy or uncomfortable, and the riding comfort in the vehicle can be improved.

 This is the end of the description of the embodiment of the present invention, but the scope of the present invention is of course not limited to the details shown or described.

  The shock absorber of the present invention can be used for vehicle vibration control.

DESCRIPTION OF SYMBOLS 1 Cylinder 2 Piston 3 Piston rod 4, 5 Damping passage 6 Housing 7 Extension side pressure chamber 8 Pressure side pressure chamber 9 Free piston 10 Extension side passage 11 Orifice hole 12 Spring element 13 Pressure side elastic member 13a, 40a Flange 13b, 40b Cushion 31a Through Hole 34 Extension side coil spring 35 Pressure side coil spring 40 Extension side elastic member C Pressure chamber D Shock absorber R1 Extension side chamber R2 Pressure side chamber

Claims (6)

A cylinder, a piston that is slidably inserted into the cylinder and divides the cylinder into an extension side chamber and a pressure side chamber, a damping passage that communicates the extension side chamber and the pressure side chamber, and a housing that forms a pressure chamber; A free piston that is slidably inserted into the housing and divides the pressure chamber into an extension-side pressure chamber and a compression-side pressure chamber; an extension-side passage that communicates the extension-side chamber and the extension-side pressure chamber; An orifice hole provided in the housing for communicating the pressure side chamber and the pressure side pressure chamber, and the free piston is positioned at a neutral position with respect to the housing, and the displacement from the neutral position of the free piston is suppressed. A shock absorber provided with a spring element that exerts a force, wherein the free piston is attached to the free piston, and the free piston is located from the neutral position with respect to the housing. Serial When displaced in a direction to compress than a predetermined pressure side displacement a compression side pressure chamber cushioning device characterized by comprising a pressure side elastic member for closing the orifice in contact with the housing. A cylinder, a piston that is slidably inserted into the cylinder and divides the cylinder into an extension side chamber and a pressure side chamber, a damping passage that communicates the extension side chamber and the pressure side chamber, and a housing that forms a pressure chamber; A free piston that is slidably inserted into the housing and divides the pressure chamber into an extension-side pressure chamber and a compression-side pressure chamber; an extension-side passage that communicates the extension-side chamber and the extension-side pressure chamber; An orifice hole provided in the housing for communicating the pressure side chamber and the pressure side pressure chamber, and the free piston is positioned at a neutral position with respect to the housing, and the displacement from the neutral position of the free piston is suppressed. A shock absorber provided with a spring element that exerts a force, wherein the free piston is attached to the free piston, and the free piston is located from the neutral position with respect to the housing. When displaced predetermined extension side displacement amount or more in a direction to compress the KiShingawa pressure chamber buffering apparatus comprising the extension side elastic member for closing the extension side passage. An extension side elastic member that is attached to the free piston and closes the extension side passage when the free piston is displaced from the neutral position to the extension side in a direction to compress the extension side pressure chamber by a predetermined extension side displacement amount or more. The shock absorber according to claim 1, further comprising: The spring element is housed in the pressure side pressure chamber and interposed between the free piston and the housing; and the spring element is housed in the extension side pressure chamber and between the free piston and the housing. An extension side coil spring interposed between
The compression-side elastic member rises from the inner periphery of the flange between the free piston and the compression-side coil spring, protrudes into the compression-side pressure chamber, and closes the orifice hole at the bottom when contacting the housing. With a bottomed cylindrical cushion,
4. The shock absorber according to claim 1, wherein the free piston includes a through hole that communicates the inside of the cushion to the extension side pressure chamber. 5. A piston rod that is inserted into the cylinder and to which the piston and the housing are attached;
The extension side passage is provided in the piston rod, opens at the tip of the piston rod, and communicates with the extension side pressure chamber.
When the free piston is mounted on the free piston and is displaced by a predetermined extension side displacement amount or more in the direction of compressing the extension side pressure chamber from the neutral position with respect to the housing, the tip end surface of the piston rod comes into contact with the housing. The shock absorber according to claim 2, 3 or 4, further comprising an expansion-side elastic member that closes the expansion-side passage. The extension side elastic member rises from an inner periphery of the flange between the free piston and the compression side coil spring, protrudes through the through hole, protrudes into the extension side pressure chamber, and contacts the piston rod. 6. The shock absorber according to claim 2, further comprising a crested cylindrical cushion that closes the extension-side passage at the top.

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