JP2011012738A - Shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shock absorber certainly which proportionally changes a damping force in a low-speed area with respect to a piston speed.SOLUTION: This shock absorber 1 includes: a cylinder 2; a piston 3 slidably inserted into the cylinder 2 and partitioning the inside of the cylinder 2 into two operation chambers R1, R2; and a rod 4 connected to the piston 3 and movably inserted into the cylinder 2. In the shock absorber, a choke cylinder 5 is provided for forming a choke passage C by fitting around the periphery of the cylinder 2.

Description

  Conventionally, in this type of shock absorber, for example, a cylinder, a piston that partitions two working chambers filled with hydraulic oil in the cylinder, and one end connected to the piston are movably inserted into the cylinder. There is a rod provided with a rod, a port provided in the piston for communicating the working chambers, and a leaf valve for opening and closing the port.

  When such a shock absorber expands and contracts, a leaf valve provides resistance to the flow of hydraulic oil that passes through the ports and moves back and forth between the working chambers, creating a pressure difference between the working chambers and generating a damping force. , Especially when the shock absorber is used for damping the car body of an automobile, the piston speed is low in the area where the piston speed is low. In many cases, the damping coefficient is increased so that the damping force rises with respect to the expansion / contraction speed.

  In order to realize the above-described damping characteristic (characteristic of change in damping force with respect to piston speed), for example, in a region where the piston speed is low, the leaf valve is set not to open the port, and the leaf valve or leaf valve In general, resistance is given to the flow of hydraulic oil at an orifice formed by a notch provided in a valve seat to be detached and attached.

  In such a shock absorber, when the piston speed is low, a damping characteristic that is a square characteristic peculiar to the orifice is exhibited, and the damping force change is large with respect to the piston speed change when the piston speed is in the low speed region, When the piston speed goes out of the low speed range and becomes medium speed, the leaf valve is separated from the annular valve seat, so the damping characteristic in the medium speed area becomes a port characteristic, which is very different from the damping characteristic in the low speed area, and the damping characteristic changes rapidly. Will end up.

  In order to alleviate the sudden change in the damping characteristics as described above, there is a shock absorber in which the damping force is linearly changed with respect to the piston speed when the piston speed is in a low speed region. A notch is provided in a part of a plurality of sub leaf valves stacked on a leaf valve seated on a valve seat, and a choke passage is configured by closing most of the notches with other sub leaf valves, or a rod Is provided with a passage that communicates the working chambers and accommodates a collar that forms a choke passage in the passage (see, for example, Patent Documents 1, 2, and 3).

JP 2005-48912 A JP 11-294515 A JP-A-11-166574

  However, the shock absorber configured as described above is not particularly problematic, but it may be pointed out that there are the following problems.

  Here, strictly speaking, the choke has not only the characteristic of the choke that causes a pressure loss proportional to the choke passage length, but also the characteristic of an orifice that is inversely proportional to the square of the passage cross-sectional area. If it is small, the pressure loss due to the orifice characteristic becomes large, and the orifice characteristic becomes dominant compared with the choke characteristic.

  For this reason, in order to make the choke characteristic dominant compared to the orifice characteristic, it is necessary to secure a long choke path length to increase the effect of the choke characteristic or to increase the passage cross-sectional area to reduce the effect of the orifice characteristic. However, it is difficult to secure the length of the choke path with a conventional shock absorber that forms a choke path with the leaf valve and sub-leaf valve, or forms a choke path in the collar housed in the rod, and secures the cross-sectional area of the path. Is difficult as well, and there is a problem that it is difficult to change the damping force linearly with respect to the piston speed in the low speed region.

  Therefore, the present invention was devised to improve the above-described problems, and the object of the present invention is to reliably change the damping force in the low speed region in proportion to the piston speed. Is to provide a shock absorber.

  In order to achieve the above-described object, the problem-solving means of the present invention includes a cylinder, a piston that is slidably inserted into the cylinder and defines two working chambers in the cylinder, and a piston that is coupled to the piston. A shock absorber provided with a rod that is movably inserted includes a choke cylinder that is fitted to the outer periphery of the cylinder to form a choke passage.

  According to the shock absorber of the present invention, it is possible to ensure a long choke passage length and a large passage cross-sectional area, so that it is possible to reliably exert a damping force that varies in proportion to the piston speed.

It is a longitudinal cross-sectional view of the shock absorber in one embodiment of the present invention. It is DD sectional drawing of the cylinder and chalk cylinder in the buffer of one Embodiment of this embodiment. It is EE sectional drawing of the cylinder and chalk cylinder in the buffer of one Embodiment of this embodiment. It is FF sectional drawing of the cylinder and choke cylinder in the buffer of one embodiment of this invention. (A) It is a side view of the cylinder in the buffer of this embodiment. (B) It is a side view of the inner cylinder in the choke cylinder of the shock absorber according to the embodiment. (C) It is a side view of the outer cylinder in the chalk cylinder of the buffer of one embodiment of the present invention. It is a longitudinal cross-sectional view of the buffer in the modification of one embodiment of this invention. (A) It is a side view of the cylinder in the buffer of the modified example of this Embodiment. (B) It is a side view of the inner cylinder in the choke cylinder of the shock absorber of the modification of this embodiment. (C) It is a side view of the outer cylinder in the choke cylinder of the shock absorber of one modification of this embodiment.

  Hereinafter, the present invention will be described based on an embodiment shown in the drawings. As shown in FIG. 1, the shock absorber 1 in one embodiment includes a cylinder 2, a piston 3 that is slidably inserted into the cylinder 2 and divides the two working chambers R <b> 1 and R <b> 2 in the cylinder 2, A rod 4 is connected to the piston 3 and is movably inserted into the cylinder 2, and a choke cylinder 5 that is fitted to the outer periphery of the cylinder 2 to form a choke passage C is provided.

  The working chambers R1 and R2 are filled with a liquid such as hydraulic oil, and the flow of the liquid that passes through the choke passage C during expansion and contraction is resisted. In addition, the shock absorber 1 includes an outer shell 6 that covers the outer periphery of the choke cylinder 5. A reservoir R is formed between the choke cylinder 5 and the outer shell 6, and liquid and gas are contained in the reservoir R. Is filled.

  Hereinafter, each part will be described in detail. As shown in FIG. 1, the cylinder 2 is accommodated in the outer shell 6 together with the choke cylinder 5, and an annular rod guide 7 fitted to the upper end of the outer shell 6 in FIG. 1. And a cap 8 that closes the lower end of the outer shell 6 in FIG. 1 and is fixed together with the choke cylinder 5 in the outer shell 6.

  When the cylinder 2 is accommodated and fixed in the outer shell 6 in this way, an annular gap is provided between the outer shell 6 and the choke cylinder 5 fitted to the outer periphery of the cylinder 2, and the reservoir R Is formed. Further, a partition member 9 is interposed between the lower end of the cylinder 2 and the cap 8, and the reservoir R and the inside of the cylinder 2 are partitioned by the partition member 9.

  A piston 3 is slidably inserted into the cylinder 2, and two working chambers R 1 and R 2 are formed in the cylinder 2. The piston 3 is provided with passages 3a and 3b communicating the working chamber R1 and the working chamber R2, the passage 3a is provided with a damping valve 3c, and the passage 3b is provided with a check valve 3d. ing. In this embodiment, the damping valve 3c provided in the passage 3a gives resistance to the flow while permitting only the flow of liquid from the working chamber R1 to the working chamber R2. On the other hand, The check valve 3d allows only a liquid flow from the working chamber R2 toward the working chamber R1. Accordingly, both the passages 3a and 3b are set to be one-way, and the damping valve 3c is a leaf valve in the illustrated case, but another damping valve such as a poppet valve may be employed. A damping valve may be provided instead of the check valve 3d.

  Further, the partition member 9 is provided with passages 9a and 9b communicating the reservoir R with the lower working chamber R2 in FIG. 1, and only the flow from the reservoir R to the working chamber R2 is allowed in the passage 9a. The check valve 9c is provided, and the passage 9b is provided with a damping valve 9d that allows only the flow from the working chamber R2 to the reservoir R and provides resistance to the flow.

  Specifically, the choke cylinder 5 includes an inner cylinder 10 and an outer cylinder 11. As shown in FIGS. 1 to 5, the inner cylinder 10 includes a rectangular choke notch 10 a having a longitudinal direction along the axial direction. The inner cylinder 10 is fitted and fixed to the outer periphery of the cylinder 2 to fix the cylinder 2. It covers the outer periphery. Note that the cylinder 2 may be fixed by being press-fitted into the inner cylinder 10, or the cylinder 2 and the inner cylinder 10 may be integrated by shrink fitting.

  Further, a through hole 2a is provided above the cylinder 2 in FIG. 1 and is opposed to the working chamber R1, and the working chamber R1 and the choke notch 10a are arranged by facing the through hole 2a and the choke notch 10a. Is in communication.

  Further, the outer cylinder 11 is fitted to and fixed to the outer periphery of the inner cylinder 10 and covers the choke notch 10a. Further, the outer cylinder 11 is provided with a through hole 11a on the lower side in FIG. 1. This through hole 11a faces the reservoir R and also faces the choke notch 10a, and the choke notch 10a, the reservoir R, Is communicated. The through hole 11a is provided at a position where the shock absorber 1 is not disposed above the liquid level in the reservoir R even when the shock absorber 1 is expanded or contracted.

  As described above, the inner cylinder 10 is sandwiched between the cylinder 2 and the outer cylinder 11, so that the choke notch 10a is covered with the cylinder 2 and the outer cylinder 11 except for the portion where the through hole 2a and the through hole 11a face each other. It is closed and functions as a choke passage C. The choke notch 10a forming the choke passage C does not have to have a linear shape that connects the through hole 2a and the through hole 11a. For example, the choke notch 10a has a shape that follows the circumference of the inner cylinder 10 in a spiral shape, a circumferential direction, The shape may be zigzag in the axial direction, and the shape can be freely set according to the length required for the choke passage C and the cross-sectional area of the passage.

  Further, the overall length of the outer cylinder 11 may be shorter than that of the inner cylinder 10, and at least the lower end of the outer cylinder 11 only needs to be lower than the liquid level in the reservoir R. In such a case, since the lower part of the choke notch 10a is not covered by the outer cylinder 11, it is not necessary to install the through hole 11a in the outer cylinder 11.

  Since the choke cylinder 5 fitted to the cylinder 2 can freely form the choke path C on the outer periphery of the cylinder 2 from the through hole 2a to the through hole 11a, the choke path length is compared with a conventional shock absorber. Since the passage cross-sectional area can also secure a long passage width around the cylinder 2, the effect of the choke characteristics in the choke passage C can be increased as compared with the conventional shock absorber. As well as reducing the effectiveness of the orifice characteristic, the choke characteristic can be relatively increased to make the choke characteristic effective.

  The operation of the shock absorber 1 configured as described above will be described. First, when the piston 3 moves upward in FIG. 1 with respect to the cylinder 2, that is, when the shock absorber 1 is in the extension stroke, the volume of the working chamber R1 decreases as the piston 3 moves. The amount of liquid becomes excessive in the working chamber R1. When the speed at which the shock absorber 1 extends, that is, when the piston speed is in the low speed region, the damping valve 3c does not open or is opened, but in this low speed region, it is given to the liquid flow through the choke passage C. A resistance larger than the resistance is provided, and the excess liquid in the working chamber R1 is discharged to the reservoir R through the choke passage C. On the other hand, as the piston 3 moves upward in FIG. 1 with respect to the cylinder 2, the check valve 9c provided in the partition member 9 opens to the working chamber R2 where the volume increases and the liquid is insufficient. Insufficient liquid is supplied from the reservoir R through the passage 9a.

  On the other hand, when the shock absorber 1 is in the extension stroke and the piston speed goes out of the low speed region and becomes the medium high speed region, the flow rate flowing out from the working chamber R1 increases and it becomes difficult to pass through the choke passage C. Since the valve 3c opens or the degree of valve opening increases, the resistance in the damping valve 3c becomes smaller than the resistance of the choke passage C, so that the liquid moves from the working chamber R1 to the working chamber R2 via the passage 3a, and the rod 3 The liquid is supplied from the reservoir R to the working chamber R2 through the passage 9a in accordance with the volume of the gas discharged from the cylinder 2.

  Thus, when the shock absorber 1 is in the extension stroke and the piston speed is in the low speed region, a damping force that varies in proportion to the piston speed is generated mainly by the choke passage C, and the piston speed becomes medium. When in the high speed region, a damping force is mainly generated by the damping valve 3c.

  Subsequently, when the piston 3 moves downward in FIG. 1 with respect to the cylinder 2, that is, when the shock absorber 1 is in the contraction stroke, the volume of the working chamber R2 decreases as the piston 3 moves, The liquid in the working chamber R2 opens the check valve 3d and moves to the working chamber R1. When the piston speed is in the low speed region, even if the damping valve 9d is not opened or opened, a resistance larger than the resistance given to the liquid flow through the choke passage C is given in this low speed region. In the inside, since the liquid of the volume of the rod 3 entering the cylinder 2 becomes excessive, the excess liquid is discharged to the reservoir R through the choke passage C.

  On the other hand, when the shock absorber 1 is in the contraction stroke and the piston speed goes out of the low speed region and becomes the middle high speed region, the flow rate flowing out from the working chamber R1 increases and becomes difficult to pass through the choke passage C. Since the valve 9d opens or the degree of valve opening increases and the resistance in the damping valve 9d becomes smaller than the resistance of the choke passage C, the liquid not only moves from the working chamber R2 to the working chamber R1, but also the excess amount. The liquid is discharged from the working chamber R2 to the reservoir R through the passage 9b, and resistance is given to the flow at the time of discharge by the damping valve 9d.

  As described above, in the shock absorber 1, a damping force is mainly generated by the choke passage C when the piston speed is in the low speed region in both the expansion and contraction strokes. Since the choke passage C can ensure a long choke passage length and a large passage cross-sectional area as described above, it can surely exert a damping force that varies in proportion to the piston speed.

  In the above-described embodiment, the choke passage C communicates with the working chamber R1 and the reservoir R, and the liquid passing through the choke passage C is always in one direction from the working chamber R1 toward the reservoir R. Since it flows, there is no delay in the pressure in the cylinder 2 when the operation of the shock absorber 1 is switched from expansion to contraction, and the operation is performed when the operation of the shock absorber 1 is switched from contraction to expansion. Since there is no delay in the pressure in the chamber R1, even if the choke passage length is increased, the damping force generation response of the shock absorber 1 is not impaired.

  In addition, a passage communicating with the reservoir R in parallel with the choke passage C is provided, and a damping valve that allows only a flow from the working chamber R1 to the reservoir R is provided in the passage, and the piston 3 is connected to the working chamber R2 from the working chamber R2. Only the passage that allows only the flow of liquid toward the working chamber R1 is provided, and only the passage that allows only the flow of liquid from the reservoir R to the working chamber R2 is provided in the partition member 9, so that the liquid is in the working chamber R2, the working chamber. Even when configured as a uniflow-type shock absorber that circulates sequentially through R1 and the reservoir R, the flow of the liquid passing through the choke passage C is one-way, so that the above-described damping force generation responsiveness can be achieved even with this setting. There is no loss.

  In addition, it is impossible to receive the advantage that the damping force generation response is not impaired, but it is also possible to employ a configuration in which the working chambers R1 and R2 are communicated with each other through the choke passage C. When the piston speed is in the low speed region in both the expansion and contraction strokes, a damping force is mainly generated by the choke passage C, and the effect of being able to reliably exhibit a damping force that changes proportionally with respect to the piston speed is lost. There is nothing.

  When the choke passage C is formed, the choke cylinder 5 is formed as a single cylinder, and a groove or a recess functioning as a choke passage is provided on the inner circumference of the choke cylinder or the outer circumference of the cylinder, and fitted into the cylinder 2. However, as in the present embodiment, the choke cylinder 5 is composed of the inner cylinder 10 and the outer cylinder 11, and the choke passage C is formed by the choke notch 10a. The choke characteristics can be set accurately and easily.

  In addition, since the choke passage C can be formed by fitting the choke cylinder 5 to the cylinder 2 and the cylinder 2 and the choke cylinder 5 only need to ensure strength, the shock absorber 1 is not enlarged more than necessary. . In this case, the shock absorber 1 is a double-tube shock absorber in which the reservoir R is formed by providing the outer shell 6 on the outer periphery of the choke tube 5, but the through hole 2a facing the working chamber R1 in the cylinder 2 is used. In addition, when the other passage hole facing the working chamber R2 is provided and the choke passage C communicates with the working chambers R1 and R2, the shock absorber 1 may be a single tube type instead of a double tube type. Good.

  Furthermore, like the shock absorber 12 in one modification of the embodiment shown in FIGS. 6 and 7, the cylinder 13 is provided with a plurality of notches 13a for communicating the choke passage C1 with the working chamber R1, and the choke The choke cylinder 14 forming the passage C1 may be constituted by the inner cylinder 15 in which the choke notch 15a is provided over the entire length, and the outer cylinder 16 having no through holes or notches.

  The structure of each part in the shock absorber 12 other than the cylinder 13 and the choke cylinder 14 is the same as the structure of each part of the shock absorber 1 in the above-described embodiment. Since the description common to both members is duplicated, only the same reference numerals are given and the detailed description is omitted.

  In the shock absorber 12 in this modified example, a plurality of cutouts 13a formed by cutting out from the upper end in FIGS. 6 and 7 of the cylinder 13 are provided in the circumferential direction of the cylinder 13, and the circumference between the cutouts 13a is arranged. The distance L, which is the directional distance, is shorter than the circumferential width of the choke cutout 15 a provided in the inner cylinder 15. Further, in this case, the plurality of notches 13a are provided in the circumferential direction with equal intervals, and the total distance L2 of the circumferential distance between the notches 13a and the circumferential distance between the notches 13a, and the width of the choke notch 15a. The circumferential distance W is equal. In this case, the notch 13a is formed by notching the upper end of the cylinder 13. However, the notch 13a may be formed by drilling from the side of the cylinder 13 to have a hole shape.

  Further, in this case, the inner cylinder 15 is provided with a choke cutout 15a over the entire length in the axial direction, and the cross-sectional shape thereof is set to a C-shape with the choke cutout 15a being divided.

  When the inner cylinder 15 is fitted to the outer periphery of the cylinder 13 so that the notch 13a and the choke notch 15a can face each other, the interval L between the notches 13a is shorter than the circumferential width of the choke notch 15a. Therefore, no matter what the relative positions of the inner cylinder 15 and the cylinder 13 in the circumferential direction are, one or more cutouts 13a are always communicated with the choke cutout 15a. Further, a plurality of notches 13a are provided side by side in the circumferential direction at equal intervals, and the circumferential direction is the total distance L2 of the circumferential distance of the notches 13a and the circumferential distance between the notches 13a and the width of the choke notch 15a. Since the distance W is equal, the overlapping area of the notch 13a and the choke notch 15a is constant regardless of the relative position of the inner cylinder 15 and the cylinder 13 in the circumferential direction, and the working chamber R1 and the choke passage C are constant. There is an advantage that the connection area is always constant.

  Further, the outer cylinder 16 is a cylinder having no through-holes and notches. When the outer cylinder 16 is fitted to the outer periphery of the inner cylinder 15 fitted to the cylinder 13, the choke notch 15a becomes the notch 13a. 6 and the cylinder 13 and the outer cylinder 16 except for the lower end in FIG. The partition member 9 fitted to the lower end of the cylinder 13 in FIG. 6 has an outer diameter that does not block the lower end of the choke cutout 15a. Therefore, the lower end of the choke notch 15a communicates with the reservoir R regardless of the circumferential relative position of the outer cylinder 16 and the inner cylinder 15.

  That is, the choke notch 15a is sandwiched between the cylinder 13 and the outer cylinder 16 to form the choke passage C1, and the choke passage C1 communicates the working chamber R1 and the reservoir R.

  Thus, even in the shock absorber 12, since the other configuration is the same as that of the shock absorber 1, the liquid flow during expansion and contraction is the same as that of the shock absorber 1 described above, and the piston speed is low in both expansion and contraction strokes. In this case, a damping force is mainly generated by the choke passage C1. The choke passage C1 can be freely formed on the outer periphery of the cylinder 13 by the choke cylinder 14 fitted to the cylinder 13, so that the length of the choke passage can be ensured longer than that of the conventional shock absorber. In addition, since the passage cross-sectional area can secure a long passage width around the cylinder 2, it is only possible to increase the effectiveness of the choke characteristics in the choke passage C as compared with the conventional shock absorber. In addition, the effectiveness of the orifice characteristic can be reduced, the choke characteristic can be relatively increased, and the effect of the choke characteristic can be made dominant.

  Therefore, even in the shock absorber 12 in one modified example, a long choke path length can be secured and a large passage cross-sectional area can be secured, so that a damping force that varies proportionally with respect to the piston speed is reliably exhibited. can do.

  Further, the interval L between the notches 13a is shorter than the circumferential width of the choke notch 15a, and the lower end of the choke notch 15a communicates with the reservoir R. There is no need for positioning and fitting, and the assembling work becomes very simple.

  Furthermore, when a plurality of cutouts 13a are provided, the total distance L2 of the circumferential distance of the cutouts 13a and the circumferential distance between the cutouts 13a and the circumferential distance W as the width of the choke cutout 15a can be made equal. Whatever the relative positions of the cylinder 15 and the cylinder 13 in the circumferential direction, the connection area between the working chamber R1 and the choke passage C is always constant.

  In the above description, the shock absorbers 1 and 12 are described as single rod type shock absorbers, but the shock absorbers 1 and 12 may be double rod type shock absorbers.

  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.

1, 12 Shock absorber 2, 13 Cylinder 2a Through hole 3 Piston 3a, 3b Passage 3c Damping valve 3d Check valve 4 Rod 5, 14 Choke cylinder 6 Outer tube 7 Rod guide 8 Cap 9 Partition members 9a, 9b Passage 9c Check Valve 9d Damping valve 10, 15 Inner cylinder 10a, 15a Choke notch 11, 16 Outer cylinder 11a, 16a Through hole 13a Notch C, C1 Choke passage R Reservoir R1, R2 Working chamber

Claims (8)

A shock absorber comprising a cylinder, a piston slidably inserted into the cylinder and defining two working chambers in the cylinder, and a rod connected to the piston and movably inserted into the cylinder. A shock absorber comprising a choke cylinder which is fitted to an outer periphery of the choke to form a choke passage. The choke cylinder includes an inner cylinder that includes a choke notch and is fitted to the outer periphery of the cylinder, and an outer cylinder that is fitted to the outer circumference of the inner cylinder and covers the notch, and the choke passage is formed by the choke notch. The shock absorber according to claim 1. The shock absorber according to claim 1, wherein the choke passage communicates the working chambers. The shock absorber according to claim 1 or 2, further comprising a reservoir communicated with one of the working chambers via a passage, wherein the choke passage communicates the other of the working chambers with the reservoir. Provided with a plurality of cutouts arranged in the circumferential direction at one end of the cylinder, the circumferential interval between the cutouts is made narrower than the circumferential width of the choke cutout, and one or more of the cutouts are opposed to the choke cutout The shock absorber according to any one of claims 2 to 4, wherein the choke passage and the working chamber communicate with each other. Provided with a plurality of notches arranged at equal intervals in the circumferential direction at one end of the cylinder, and the choke notch width is made equal to the circumferential distance between the notches, the circumferential distance between the notches, and the width of the choke notch. The shock absorber according to any one of claims 2 to 4, wherein one or more of the cutouts are opposed to the cutout for communicating the choke passage and the working chamber. The choke tube is formed between the choke tube and an outer shell provided on the outer periphery of the choke tube, the choke notch is formed over the entire axial length of the inner tube, and the choke notch end communicates with the reservoir. The shock absorber according to any one of claims 4 to 6. The shock absorber according to any one of claims 4 to 7, wherein a flow passing through the choke passage is set to a one-way flow from the working chamber to the reservoir during the expansion and contraction operation.

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