Shock absorber

Abstract

Provided is a shock absorber with which it is possible to obtain damping force characteristics that are stable on the sprung of a vehicle regardless of the road surface. A damper is provided with an inner cylinder, a piston, a first oil passage, a piston extension-side valve, a second oil passage, and a piston contraction-side valve. Among the piston extension-side valve and the piston contraction-side valve, the valve having a large frequency dependency of damping force matches the valve having a small frequency dependency of damping force. Therefore, for example, in one of the piston extension-side valve and the piston contraction-side valve having a high valve-opening pressure (for example, the piston extension-side valve), a valve-opening promotion mechanism is provided that coincides with the valve-opening timing of one of the valve having a low valve-opening pressure (for example, the piston contraction-side valve).

Description

Technical Field

[0001] The present disclosure relates, for example, to a shock absorber for reducing vibrations of vehicles such as automobiles. Background Art

[0002] In vehicles such as four-wheel automobiles, a shock absorber (damper) is provided between the vehicle body (above the spring) side and each wheel (below the spring) side. The shock absorber described in Patent Document 1 is provided with disk valves on the lower surface side and the upper surface side of the piston, respectively. The disk valve on the lower surface side of the piston opens based on an increase in the differential pressure between the oil chamber on the upper surface side of the piston and the oil chamber on the lower surface side of the piston when the rod moves toward the extending side. The disk valve on the upper surface side of the piston opens based on an increase in the differential pressure between the oil chamber on the lower surface side of the piston and the oil chamber on the upper surface side of the piston when the rod moves toward the contracting side.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2020-34068 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] However, when a shock absorber is mounted (introduced, adopted) on a vehicle, it needs to be suitable for that vehicle. That is, the shock absorber adjusts the damping force (in Japanese: 減衰力) to obtain the desired riding comfort in the mounted vehicle. In this case, the desired riding comfort is mainly approached by adjusting the damping force with respect to the piston speed on the extending side and the contracting side. However, by only adjusting the damping force with respect to the piston speed on the extending side and the contracting side, the riding comfort may deteriorate due to the road surface condition, and the road surface on which the vehicle can travel without a sense of incongruity may be limited.

[0008] One object of the present invention is to provide a shock absorber capable of obtaining stable damping force characteristics above the spring of the vehicle regardless of the road surface.

[0009] Means for Solving the Problems

[0010] The present invention is preferably a shock absorber including: an inner cylinder in which a working fluid is enclosed; a piston slidably disposed in the inner cylinder and partitioning the inside of the inner cylinder into a first chamber and a second chamber; a first passage provided in the piston; a first valve for opening and closing the first passage; a second passage provided in the piston; and a second valve for opening and closing the second passage, and a valve opening promoting mechanism is provided in the valve having the higher valve opening pressure among the first valve and the second valve to coincide with the valve opening timing of the valve having the lower valve opening pressure.

[0011] In addition, the present invention is preferably a buffer, which comprises: an inner cylinder, which is sealed with a working fluid; a piston, which is slidably arranged in the inner cylinder and divides the inner cylinder into a first chamber and a second chamber; a first passage, which is arranged in the piston; a first valve, which opens and closes the first passage; a second passage, which is arranged in the piston; and a second valve, which opens and closes the second passage, and the buffer is constructed so that the frequency characteristics of the valve with a larger frequency dependence of the attenuation force between the first valve and the second valve are consistent with the frequency characteristics of the valve with a smaller frequency dependence of the attenuation force.

[0012] In addition, the present invention is preferably a buffer, which comprises: an inner tube, which is sealed with a working fluid; a piston, which is slidably arranged in the inner tube and divides the inner tube into a first chamber and a second chamber; a first passage, which is arranged on the piston; a first valve, which opens and closes the first passage; a second passage, which is arranged on the piston; and a second valve, which opens and closes the second passage, and a low-speed valve is arranged in the valve on the side with a higher valve opening pressure among the first valve and the second valve. The low-speed valve has a smaller force than the valve on the side with a lower valve opening pressure, and opens the first passage or the second passage when the piston speed is low.

[0013] Furthermore, the present invention is preferably a buffer, which comprises: an inner cylinder, which is sealed with a working fluid; a piston, which is slidably disposed in the inner cylinder and divides the inner cylinder into a first chamber and a second chamber; an outer cylinder, which is disposed outside the inner cylinder and forms a storage chamber between the inner cylinder and the outer cylinder; a valve body, which is disposed between the storage chamber and the second chamber; a first passage, which is disposed on the piston; a first valve (for example, a piston extension valve) which opens and closes the first passage; a first throttle hole, which is disposed on the first passage; a second passage, which is disposed on the piston; a second valve (for example, a piston extension valve) which opens and closes the first passage a pressure regulating valve for opening and closing the second passage; a third passage, which is arranged on the valve body; a third valve (for example, a suction valve) for opening and closing the third passage; a fourth passage, which is arranged on the valve body; a fourth valve (for example, a main pressure regulating valve) for opening and closing the fourth passage; and a second throttle hole arranged on the fourth passage, in which a valve opening promotion mechanism is arranged in the valve with a higher valve opening pressure between the first valve and the fourth valve, so as to coincide with the valve opening timing of the valve with a lower valve opening pressure (for example, when the valve opening pressure is the first valve>the fourth valve, the valve opening timing of the first valve is made consistent with that of the second valve).

[0014] According to one embodiment of the present invention, it is possible to obtain a stable damping force characteristic on the sprung portion of a vehicle regardless of the road surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a longitudinal sectional view showing the shock absorber according to the first embodiment.

[0016] Figure 2 Yes means Figure 1 An enlarged cross-sectional view of the piston, the first valve, and the second valve.

[0017] Figure 3 yes Figure 2 Enlarged view of part (III).

[0018] Figure 4 It is an exploded perspective view showing the piston, the first valve, etc.

[0019] Figure 5 This is a characteristic diagram showing the relationship between the piston speed and the damping force during low-frequency excitation according to the first embodiment.

[0020] Figure 6 3 is a characteristic diagram showing the relationship between the extension-compression ratio (expansion-contraction ratio) of the damping force and the frequency according to the first embodiment.

[0021] Figure 7 The piston, the first valve, etc. according to the modified example are shown in FIG. Figure 3 Cross-section at the same location.

[0022] Figure 8 The piston, the first valve, etc. according to the second embodiment are shown in FIG. Figure 3 Cross-section at the same location.

[0023] Fig. 9 It is an exploded perspective view showing a piston, a first valve, etc. according to the second embodiment.

[0024] Fig.10 This is a characteristic diagram showing the relationship between the piston speed and the damping force during low-frequency excitation according to the second embodiment.

[0025] Fig.11 : This is a characteristic diagram showing the relationship between the extension-compression ratio (expansion-contraction ratio) of the damping force and the frequency according to the second embodiment.

[0026] Fig.12 It is a characteristic line diagram showing the relationship between the damping force and the frequency in the orifice area.

[0027] Fig.13 It is a characteristic line diagram showing the relationship between the damping force and the frequency in the valve area.

[0028] Fig.14 It is a characteristic diagram showing the relationship between the piston speed and the damping force based on the comparative example.

[0029] Fig.15 3 is a characteristic diagram showing the relationship between the elongation-compression ratio (expansion-contraction ratio) and the frequency of the damping force according to the comparative example.

[0030] Fig.16This is a hydraulic circuit diagram of a single-tube shock absorber (mono-tube damper) and a multi-tube shock absorber (twin-tube damper).

[0031] Fig.17 This is an illustration for explaining the ideal riding comfort (vehicle behavior).

[0032] Fig.18 This is an explanatory diagram for explaining the ride comfort (vehicle behavior) to be improved. DETAILED DESCRIPTION

[0033] Hereinafter, a case where the shock absorber according to the embodiment is used for a hydraulic shock absorber assembled in a vehicle such as a four-wheel vehicle will be described with reference to the drawings as an example.

[0034] Figures 1 to 6 The first embodiment is shown. Figure 1 In the embodiment, the buffer 1 is, for example, a hydraulic buffer for a vehicle such as an automobile. The buffer 1, for example, constitutes a suspension device for a vehicle together with a suspension spring (not shown) composed of a coil spring. In the following description, one axial end side of the buffer 1 is set as the "lower end" side, and the other axial end side is set as the "upper end" side for description, but the one axial end side of the buffer 1 may be set as the "upper end" side, and the other axial end side may be set as the "lower end" side.

[0035] The buffer 1 is configured to include an outer tube 2, an inner tube 4, a piston 5, a piston rod 10, and a valve body 12. The outer tube 2 is provided outside the inner tube 4. The outer tube 2 is formed into a bottomed cylindrical shape, and constitutes the outer shell of the buffer 1. The lower end side of the outer tube 2, which is one end side, is closed by welding the bottom cover 3, and the upper end side, which is the other end side, is open. A plurality of rivet portions 2A formed by bending radially inward by riveting processing, for example, are provided at the upper end portion of the outer tube 2. The upper end side opening of the outer tube 2 is closed by a rod guide 8 and a rod seal 9.

[0036] The inner tube 4 is coaxially disposed in the outer tube 2. The inner tube 4 and the outer tube 2 together constitute a multi-tube type buffer (cylinder device). Oil (working oil) as a working fluid (working liquid) is sealed in the inner tube 4 and the outer tube 2. The oil as the working liquid is not limited to oil, and may be, for example, water mixed with an additive. The lower end side of the inner tube 4 is fitted and mounted on the outer peripheral side of the valve body 12, and the upper end side is closed by the rod guide 8.

[0037] The inner cylinder 4 forms (is divided into) an annular storage chamber A between the outer cylinder 2. In other words, the storage chamber A is formed between the outer cylinder 2 and the inner cylinder 4. In the storage chamber A, a gas is sealed together with oil as a working fluid. The gas may be, for example, air at atmospheric pressure or compressed nitrogen. The storage chamber A as a reservoir compensates for the entry and exit of the piston rod 10. The valve body 12 is located at the lower end side of the inner cylinder 4 and is provided between the bottom cover 3 and the inner cylinder 4.

[0038] The piston 5 is slidably disposed in the inner tube 4. The piston 5 divides (divides (in Japanese: draws)) the inner tube 4 into two chambers, namely, a rod side oil chamber B which is a first chamber and a bottom side oil chamber C which is a second chamber. The piston 5 is provided with a plurality of oil passages 5A and 5B which can communicate between the rod side oil chamber B and the bottom side oil chamber C. In addition, the first oil passage 5A as a first passage among the plurality of oil passages 5A and 5B is as follows: Figures 1 to 4 As shown, the second oil passage 5B as the second passage is as shown in FIG. Figure 4 shown.

[0039] The oil passages 5A and 5B constitute passages that allow the working fluid (oil) to flow from one of the oil chambers B and C in the inner tube 4 to the other chamber by the movement of the piston 5. That is, the first oil passage 5A as the first passage and the second oil passage 5B as the second passage allow the rod side oil chamber B, which will become the first chamber, to communicate with the bottom side oil chamber C, which will become the second chamber, by the movement of the piston 5. The first oil passage 5A and the second oil passage 5B are flow passages that generate the flow of the working fluid (oil) by the movement of the piston 5.

[0040] The piston 5 is provided with a valve 6 composed of, for example, one or more disks (disk valves). That is, a valve 6 serving as a damping valve on the extension side is provided on the lower side of the piston 5. The valve 6 on the extension side (hereinafter referred to as the piston extension side valve 6) applies resistance to the oil flowing from the rod side oil chamber B to the bottom side oil chamber C in the first oil passage 5A when the piston 5 slides upward along the inner tube 4 during the extension stroke of the piston rod 10. As a result, a predetermined damping force is generated during the extension stroke of the piston rod 10.

[0041] That is, the piston extension side valve 6 controls the flow of the working fluid (oil) generated by the sliding of the piston 5 in the inner tube 4 to generate a damping force. The piston extension side valve 6 is equivalent to the first valve that opens and closes the first oil passage 5A as the first passage. Fig.16 As shown, in the first oil passage 5A, a piston extension side throttle hole 52 serving as a throttle portion (opening) is provided as required. The piston extension side throttle hole 52 corresponding to the first throttle hole may be provided on the piston extension side valve 6 or on the seat side (piston 5 side).

[0042] A valve 7 composed of, for example, one or more disks (disk valves) is provided on the piston 5 separately from the piston extension side valve 6. That is, the valve 7 serving as a damping valve on the reduction side (contraction side) is provided on the upper side surface of the piston 5. The valve 7 on the reduction side (hereinafter referred to as the piston contraction side valve 7) applies resistance to the oil flowing from the bottom side oil chamber C to the rod side oil chamber B in the second oil passage 5B when the piston 5 slides downward along the inner tube 4 during the reduction stroke (contraction stroke) of the piston rod 10. As a result, a predetermined damping force is generated during the reduction stroke of the piston rod 10.

[0043] That is, the piston retraction side valve 7 controls the flow of the working fluid (oil) generated by the sliding of the piston 5 in the inner tube 4 to generate a damping force. The piston retraction side valve 7 is equivalent to a second valve that opens and closes the second oil passage 5B as the second passage. Fig.16 As shown, in the second oil passage 5B, a piston retraction side orifice 53 serving as a throttling portion (opening) is provided as required. The piston retraction side orifice 53 corresponding to the third orifice may be provided on the piston retraction side valve 7 or on the seat side (piston 5 side).

[0044] The upper end sides (opening end sides) of the outer tube 2 and the inner tube 4 are sealed by the rod guide 8 and the rod seal 9. The rod guide 8 is a guide member that slidably guides the piston rod 10 to be displaced in the axial direction. The rod guide 8 is a cylindrical body formed into a predetermined shape by, for example, forming or cutting a metal material, a hard resin material, etc., and is fitted and provided on the upper end sides (opening end sides) of the outer tube 2 and the inner tube 4.

[0045] The rod seal 9 is provided between the upper surface of the rod guide 8 and the rivet portion 2A of the outer tube 2. The rod seal 9 has a metallic annular plate 9A as a core. An elastic sealing material such as rubber is integrally formed on the annular plate 9A by a method such as sintering. The inner periphery of the rod seal 9 is in sliding contact with the outer periphery of the piston rod 10, thereby sealing the outer tube 2 and the piston rod 10 in a liquid-tight and air-tight manner (seal).

[0046] The lower end side of the piston rod 10, which becomes the base end side, is inserted into the inner tube 4, and the upper end side, which becomes the front end side, protrudes to the outside of the inner tube 4 via the rod guide 8. That is, the piston rod 10 is connected to the piston 5 and extends to the outside of the inner tube 4. The piston 5, the piston retraction side valve 7, and the piston extension side valve 6 are installed on the lower end side of the piston rod 10. Therefore, a small diameter portion 10A having a smaller diameter than other parts is provided on the lower end side of the piston rod 10. In addition, an external thread portion 10B is provided at the end of the small diameter portion 10A, and a nut 11 for fixing the piston 5, the piston retraction side valve 7, and the piston extension side valve 6 to the piston rod 10 is screwed into the external thread portion 10B.

[0047] A valve body 12 is provided at the lower end side of the inner tube 4, which is located between the inner tube 4 and the bottom cover 3 and serves as the bottom body. The valve body 12 is provided on the main body side (tube side) of the shock absorber 1. The valve body 12 is divided (partitioned) into a reservoir chamber A and a bottom oil chamber C between the bottom cover 3 and the inner tube 4. Thus, the valve body 12 is provided between the reservoir chamber A and the bottom oil chamber C. The valve body 12 is provided with a plurality of oil passages 12A and 12B that can communicate the reservoir chamber A with the bottom oil chamber C.

[0048] The oil passages 12A and 12B constitute passages that allow the working fluid (oil) to flow from one of the bottom oil chamber C in the inner tube 4 and the storage chamber A in the outer tube 2 to the other chamber by the movement of the piston 5. That is, the third oil passage 12A as the third passage and the fourth oil passage 12B as the fourth passage allow the bottom oil chamber C, which will become the second chamber, to communicate with the storage chamber A, which will become the third chamber, by the movement of the piston 5. The oil passages 12A and 12B are flow passages that generate the flow of the working fluid (oil) by the movement of the piston 5.

[0049] The valve body 12 is provided with a valve 13 composed of, for example, one or more disks (disk valves). That is, the valve 13 serving as a damping valve on the extension side is provided on the upper surface side of the valve body 12. The valve 13 on the extension side (hereinafter referred to as the main body extension side valve 13) applies resistance to the oil flowing in the third oil passage 12A from the reservoir chamber A side to the bottom side oil chamber C when the piston 5 slides upward during the extension stroke of the piston rod 10.

[0050] The main body extension side valve 13 corresponds to a third valve that opens and closes the third oil passage 12A as the third passage. Fig.16 As shown, in the third oil passage 12A, a main body extension side throttle hole 56 serving as a throttle portion (opening) is provided as required. The main body extension side throttle hole 56 corresponding to the fourth throttle hole can be provided on the main body extension side valve 13 or on the seat side (valve body 12 side).

[0051] In addition, the main body extension side valve 13 as the third valve can be configured as a suction valve, for example, which is mainly used as a check valve (check valve) and generates almost no damping force. That is, the main body extension side valve 13 can be configured as a check valve that opens when the piston 5 slides upward during the extension stroke of the piston rod 10, and closes the valve otherwise. The main body extension side valve 13 that becomes such a check valve allows the oil in the storage chamber A to flow into the bottom side oil chamber C in the oil path 12A, and prevents the oil from flowing in the opposite direction.

[0052] In the valve body 12, a valve 14 composed of, for example, one or more disks (disk valve) is provided separately from the main body extension side valve 13. That is, the valve 14 serving as the attenuation valve on the contraction side is provided on the lower surface side of the valve body 12. The valve 14 on the reduction side (hereinafter referred to as the main body contraction side valve 14) applies resistance to the oil flowing in the fourth oil passage 12B from the bottom side oil chamber C toward the storage chamber A side when the piston 5 slides downward during the reduction stroke of the piston rod 10.

[0053] The main body contraction side valve 14 corresponds to the fourth valve that opens and closes the fourth oil passage 12B serving as the fourth passage. As will be described later Fig.16 As shown, in the fourth oil passage 12B, a main body contraction side throttle hole 57 serving as a throttle portion (opening) is provided as needed. The main body contraction side orifice 57 corresponding to the second orifice can be provided either on the main body contraction side valve 14 or on the seat side (valve body 12 side).

[0054] However, an automobile travels at an arbitrary speed on roads with various road surface conditions. Therefore, the vehicle body receives inputs from various road surfaces. Under such various driving conditions, it is desired to maintain the riding comfort that provides a sense of stability to the occupants. Here, in a general oil damper, the magnitude of the damping force relative to the piston speed is mainly adjusted on the contraction side and the extension side to approach the desired riding comfort. Usually, such adjustment of the damping force is performed based on the characteristics in a relatively large amplitude and low frequency band.

[0055] However, the oil damping force exhibits frequency dependence. Therefore, by only adjusting the magnitude of the damping force relative to the piston speed based on the characteristics in a relatively large amplitude and low frequency band on the contraction side and the extension side, it may be impossible for the oil damper to generate an appropriate damping force when the input frequency varies in various ways. For example, by only adjusting the damping force, there may be a feeling of tightness (Japanese: 突っ張り感) as shown in (A) of Fig.18 . In addition, by only adjusting the damping force, there may be a wobbling (Japanese: ヒョコつき) as shown in (B) of Fig.18 . As a result, during actual driving, due to the road surface, good behavior may not be obtained, and there is a concern about impairing the stability felt by the occupants.

[0056] As described above, the vehicle body in motion receives various inputs from the road surface. In addition, the size of the road surface undulations, the intervals between the unevenness, etc. are various. Therefore, it is important not only to make the damping force relative to the piston speed appropriate but also to make the damping force relative to the input frequency appropriate. In particular, in order to obtain stable riding comfort under various driving conditions, it is desired to reduce the frequency dependence of the damping force. However, reducing the frequency dependence causes delays in the damping force due to the compressibility of the working oil, etc., and is difficult.

[0057] On the other hand, even if the extension-side damping force and the contraction-side damping force each have frequency dependencies, as long as their ratio does not change with respect to the input frequency, or as long as the change is small, the balance of the up-and-down motion on the spring will not change significantly even if the road surface condition changes. Fig.17 As shown, a state with a constant sense of flatness (ideal state) can be obtained, which can reduce the sense of discomfort during driving. Therefore, in the embodiment, the above-mentioned problem is solved by reducing the frequency dependence of the ratio of the extension side damping force to the contraction side damping force (hereinafter referred to as the "extension-pressure ratio of the damping force").

[0058] The following describes the cause of the frequency dependency of the extension-pressure ratio (=extension-side damping force / contraction-side damping force) of the damping force and a method for reducing it.

[0059] The hydraulic shock absorber that provides damping force by general valve stacking has a high-pressure side oil chamber (high-pressure side chamber) and a low-pressure side oil chamber (low-pressure side chamber) filled with working oil. In addition, a flow path for the working oil to move between these oil chambers is set, and the differential pressure is adjusted by the area of ​​the flow path to obtain the desired damping force. The flow path for the working oil to move is generally divided into two types. One of them is a throttle hole that is always connected with a constant area regardless of the pressure difference between the oil chambers. The other is a valve composed of a valve body based on a stacked disk valve.

[0060] The valve closes the flow path by closing the valve until the differential pressure generated between the upstream oil chamber and the downstream oil chamber of the flow path reaches a set size. In addition, if the differential pressure becomes greater than the set size, the valve opens and the upstream oil chamber is connected to the downstream oil chamber. Therefore, when the speed of the hydraulic buffer stroke (piston speed) is low, the differential pressure is also low, so the valve closes and the working oil only passes through the throttle hole. From this state, the piston speed increases further, thereby increasing the differential pressure. If the load based on the differential pressure exceeds the valve closing load (preset) previously assigned to the valve, the valve opens. Thereafter, as the differential pressure increases, the valve opening also increases, and the flow path area expands.

[0061] Here, the area where the differential pressure is generated based on the orifice when the valve is closed is defined as the "orifice area", and the area where the valve is open is defined as the "valve area". In this case, the frequency characteristics of the damping force are different in the orifice area and the valve area. Specifically, Fig.12 As shown, in the throttle area, the flow area is small and constant, so it is difficult to obtain the flow rate relative to the increase in differential pressure, and it is easy to convert not only the inflow and outflow but also the volume deformation of the working oil. Therefore, as the response delay is large and the frequency increases, the damping force decreases. Fig.13 As shown, in the valve region, the response delay is easily alleviated, and the change in damping force due to frequency is hardly seen.

[0062] Generally, the damping force characteristics of the damper (shock absorber) used in automobiles almost always provide different characteristics on the extension side and the contraction side. In order to obtain such characteristics, in addition to setting different throttle hole areas on the extension side and the contraction side, the valve opening heights corresponding to the valve opening pressure and differential pressure need to be set to different values ​​for the extension side valve and the contraction side valve according to their respective rigidities and presets. Therefore, the valve opening characteristics of the valves on the extension side and the contraction side, that is, the timing of valve opening, differ. Therefore, depending on the piston speed, one of the extension side and the contraction side becomes the throttle hole area and the other becomes the valve area. Due to the difference in the frequency characteristics of the throttle hole area and the valve domain shown above, the extension-pressure ratio of the damping force has frequency dependence.

[0063] For example, Fig.14 This example shows the relationship between piston speed and damping force when a significantly higher valve opening pressure is applied to the valve on the extension side relative to the contraction side. In this case, the extension side becomes a throttle area relative to the contraction side, and the damping force on the extension side of this area decreases as the frequency increases until a higher piston speed. On the other hand, the contraction side shifts to the valve area at a lower piston speed relative to the extension side, and the decrease in damping force relative to the frequency is small.

[0064] Due to such a difference in characteristics, the extension-compression ratio (extension-contraction ratio) of the damping force has frequency dependency. Fig.15 Representation and Fig.14 In the same case, the relationship between the expansion pressure ratio of the damping force (expansion side damping force / contraction side damping force) and the frequency is given when a significantly higher valve opening pressure is applied to the valve on the expansion side relative to the contraction side. Fig.15 The characteristic line 101 in Fig.14 The change in the elongation-compression ratio of the damping force at the "piston speed a" relative to the frequency. Similarly, Fig.15 The characteristic line 102 in FIG. Fig.14 The characteristic line 103 shows the change of the elongation-compression ratio of the damping force at the "piston speed b" with respect to the frequency. Fig.14 Change in the elongation-compression ratio of the damping force at the "piston speed c" relative to the frequency.

[0065] like Fig.15 As shown in FIG. 1 , for example, at “piston speed b”, the change in the extension-pressure ratio of the damping force relative to the frequency becomes larger than at “piston speed a” and “piston speed c”. In such a case, as described above, the sense of stability felt by the occupant is reduced. Therefore, by making the valve opening timing of each valve on the extension side and the contraction side close to each other, the frequency dependence of the extension-pressure ratio can be reduced.

[0066] However, in a general disc valve stacking method, if the valve opening timing on the high attenuation side (the extension side in this example) is to be slowed down in order to make the valve opening timings of the extension side and the contraction side close, it is necessary to reduce the rigidity of the valve on the high attenuation side and lower the valve opening pressure, which reduces the damping force after the valve is opened, and there is a concern that the damping force in the medium and high speed range that is originally required, such as suppressing the resonance on the spring, will be insufficient.

[0067] Therefore, in the embodiment, a valve opening promotion mechanism (sub-valve) is provided in the valve on the side with higher valve opening pressure between the extension side and the contraction side, which is consistent with the piston speed of the valve opening on the side with lower valve opening pressure. By means of the valve opening promotion mechanism, it is possible to suppress the decrease in valve opening pressure while slowing down the valve opening timing compared with the stacking method of the general disc valve. Therefore, by slowing down the valve opening timing and making it consistent with the valve opening timing of the valve on the side with lower valve opening pressure, it is possible to reduce the frequency dependence of the extension pressure ratio of the damping force and suppress the decrease in the damping force.

[0068] That is, in the embodiment, by providing a valve opening promotion mechanism (auxiliary valve), the valve opening pressure of the valve with a larger valve opening pressure on the extension side and the contraction side can be maintained while the valve opening timing can be moved to the low speed side. Therefore, the valve opening timing on the extension side and the contraction side can be made consistent on the basis of ensuring the adjustment freedom of the damping force (on the side with a larger valve opening pressure), and the frequency dependence of the damping force on the extension pressure ratio can be reduced. As a result, compared with the previous technology, it is possible to achieve a ride comfort that is more robust to changes in road conditions and provides a sense of stability to the occupants. The following is a detailed description of the structure that achieves these.

[0069] First, the valve to be provided with the valve opening promotion mechanism is defined according to the structure of the damper (shock absorber).

[0070] Fig.16 (A) shows the hydraulic circuit of the single tube damper 51 which is a single tube type buffer. Fig.16 As shown in (A), the single-tube damper 51 generates damping force by two valves 6 and 7 provided on the piston 5. That is, the single-tube damper 51 is provided with a piston contraction side valve 7 (piston contraction valve) and a piston extension side valve 6 (piston extension valve) on the piston 5. In this case, as required, a piston extension side throttle hole 52 (piston extension throttle hole) and / or a piston contraction side throttle hole 53 (piston contraction throttle hole) are provided between the rod side oil chamber B which becomes the piston upper chamber and the bottom side oil chamber C which becomes the piston lower chamber. In the case of such a single-tube damper 51, the valve opening promotion mechanism can be provided in the valve having a higher valve opening pressure among the two valves 6 and 7 of the piston 5 (for example, the piston extension side valve 6).

[0071] Fig.16(B) shows the hydraulic circuit of the twin-tube damper 54 as a multi-tube damper. The damper 1 of the embodiment corresponds to the twin-tube damper 54. Fig.16 As shown in (B), the twin-tube damper 54 has four valves 6, 7, 13, and 14 on the piston 5 side and the body 55 side. That is, the twin-tube damper 54 is provided with a piston contraction side valve 7 (piston contraction valve) that contributes to the contraction side damping force and a piston extension side valve 6 (piston extension valve) that contributes to the extension side damping force on the piston 5 side. In this case, as needed, a piston extension side orifice 52 (piston extension orifice) and / or a piston contraction side orifice 53 (piston contraction orifice) are provided between the rod side oil chamber B that becomes the piston upper chamber and the bottom side oil chamber C that becomes the piston lower chamber.

[0072] In addition, the twin-tube damper 54 is provided with a main body extension side valve 13 (main body extension valve) contributing to the extension side damping force and a main body contraction side valve 14 (main body contraction valve) contributing to the contraction side damping force on the main body 55 (valve body 12) side. In this case, a main body extension side orifice 56 (main body extension orifice) and / or a main body contraction side orifice 57 (main body contraction orifice) are provided between the bottom side oil chamber C, which becomes the piston lower chamber, and the reservoir chamber A as needed.

[0073] Here, in the case of reducing the frequency dependence of the extension pressure ratio of the damping force, it is sufficient to make the valve opening timing (piston speed) of all valves consistent. However, the rigidity (valve rigidity) of each valve is greatly different, so it is not realistic. Therefore, by mainly making the valve opening timing of the valve that contributes to the generation of the damping force consistent, the reduction of the extension pressure ratio of the damping force is achieved. Therefore, for the main body extension side valve 13, it becomes a suction valve that mainly functions as a one-way valve and hardly generates damping force. Since its contribution to the damping force characteristics is small, it is ignored, and the valve opening timing of the remaining three valves 6, 7, and 14 is adjusted by the following idea.

[0074] First, the frequency dependence of the damping force is caused by the reduction of responsiveness in the throttle area. Therefore, the frequency dependence becomes significant in a valve whose valve opening pressure is high and the throttle area continues to a higher piston speed. Therefore, for the valve with the highest valve opening pressure among the three valves 6, 7, and 14, a valve opening promotion mechanism is provided to approach the valve opening timing of the valve with low rigidity and low valve opening pressure. Specifically, the valve opening pressure of the piston contraction side valve 7 and the main body contraction side valve 14 that contribute to the contraction side damping force is compared with the valve opening pressure of the piston extension side valve 6 that contributes to the extension side damping force.

[0075] For example, when the extension-side damping force is greater than the contraction-side damping force, that is, when the valve opening pressure of the piston extension-side valve 6 is the maximum, a valve opening promotion mechanism is provided in the piston extension-side valve 6. Thus, the valve opening timing of the piston extension-side valve 6 is brought close to the valve opening timing of the valve with the smaller valve opening pressure (in principle, the piston contraction-side valve 7 according to the pressure balance relationship) between the piston contraction-side valve 7 and the main body contraction-side valve 14 that contribute to the contraction-side damping force. Next, when the contraction-side damping force is greater than the extension-side damping force, that is, when the valve opening pressure of the main body contraction-side valve 14 is the maximum, a valve opening promotion mechanism is provided in the main body contraction-side valve 14. Thus, the valve opening timing of the main body contraction-side valve 14 is brought close to the valve opening timing of the piston extension-side valve 6.

[0076] Then, except Figure 1 In addition, refer to Figures 2 to 4 Next, the valve opening promotion mechanism 21 of the first embodiment will be described. In the first embodiment, the valve opening promotion mechanism 21 is provided in the piston extension side valve 6.

[0077] The piston extension side valve 6 includes a low-speed valve 22 and a second-stage valve 24 as a main valve. The valve opening promotion mechanism 21 is composed of the low-speed valve 22. The low-speed valve 22 includes a low-speed disc 22A corresponding to the low-speed valve opening valve and a small-diameter disc 22B corresponding to the small-diameter valve. The low-speed disc 22A contacts the seat portion 5C of the opening of the first oil passage 5A provided in the piston 5. The low-speed disc 22A is formed as an annular plate having an insertion hole provided inside. The low-speed disc 22A constituting the low-speed valve 22 is seated or seated on the seat pressure surface 5C1 of the seat portion 5C. Figure 4 As shown, the seat portion 5C is not a circular ring but a seat shape with different diameters. In addition, although not shown in the figure, a concave portion (gap) that becomes a throttle hole can be provided in the seat portion 5C by embossing (embossing processing, punching processing) as needed.

[0078] A small-diameter disk 22B having an outer diameter smaller than that of the seat portion 5C of the piston 5 is arranged on the back side (lower surface side) of the low-speed disk 22A. The outer diameter of the small-diameter disk 22B is smaller than that of the low-speed disk 22A. The small-diameter disk 22B is also formed as an annular plate having an insertion hole provided inside. A second-stage valve 24 is arranged on the back side (lower surface) of the small-diameter disk 22B. The outer diameter of the second-stage valve 24 is the same as that of the low-speed disk 22A of the low-speed valve 22. The second-stage valve 24 is formed by stacking three disks 24A, 24B, and 24C each formed as an annular plate. A retainer 25 and a washer 26 are arranged on the back side of the second-stage valve 24. In addition, the low-speed valve 22 (low-speed disk 22A, small-diameter disk 22B), the second-stage valve 24 (disks 24A, 24B, 24C), the retainer 25, and the washer 26 are fastened to the piston rod 10 by a nut 11.

[0079] As described above, in the first embodiment, the small-diameter disk 22B is disposed between the low-speed disk 22A and the second-stage valve 24. Thus, the gap 27 is provided between the low-speed disk 22A and the second-stage valve 24 via the small-diameter disk 22B. Therefore, the rigidity of the low-speed valve 22 (low-speed disk 22A) at the initial stage of valve opening can be reduced by the gap 27. That is, the valve opening of the low-speed valve 22 (low-speed disk 22A) can be promoted from a lower piston speed by the gap 27.

[0080] As a result, regarding the piston extension side valve 6, in the area where the piston speed is low at the initial stage of valve opening, only the low-speed valve 22 (low-speed disk 22A) functions as a valve body, so the valve rigidity can be reduced. In addition, in the medium and high speed range where the low-speed valve 22 (low-speed disk 22A) contacts the second-stage valve 24, the second-stage valve 24 also becomes a valve body, so the valve rigidity becomes high. Such nonlinear valve rigidity characteristics are the characteristics of this structure. The rigidity of the low-speed valve 22 is mainly determined by the plate thickness dimension of the low-speed disk 22A and the outer diameter dimension of the small-diameter disk 22B. Therefore, the two parameters (i.e., the plate thickness dimension of the low-speed disk 22A and the outer diameter dimension of the small-diameter disk 22B) are adjusted so that the valve opening timing of the piston extension side valve 6 (i.e., the valve opening timing of the low-speed valve 22) becomes the desired timing.

[0081] The size of the gap 27 between the low speed valve 22 (low speed disk 22A) and the second stage valve 24 controls the timing (piston speed) at which the low speed valve 22 (low speed disk 22A) contacts the second stage valve 24. Therefore, the range in which the low speed valve 22 (low speed disk 22A) becomes effective is determined by the size of the gap 27 (the distance between the low speed disk 22A and the second stage valve 24).

[0082] Therefore, the damping force in the middle and high speed range is affected. In addition, as a factor that controls the damping force in the middle and high speed range, there is the rigidity of the second stage valve 24. Therefore, the rigidity of the second stage valve 24 is adjusted to obtain the desired damping force. The second stage valve 24 can also be configured to apply initial deflection to the piston extension side valve 6. In addition, the second stage valve 24 can also change its outer diameter midway. That is, the outer diameters of the disks 24A, 24B, and 24C constituting the second stage valve 24 can also be different.

[0083] In summary, in the first embodiment, a low-speed valve 22 (low-speed disk 22A and small-diameter disk 22B) serving as a valve opening promotion mechanism 21 is provided on the piston extension side valve 6. The valve opening promotion mechanism 21 makes the frequency characteristics of the damping force generated by the piston extension side valve 6 consistent with the frequency characteristics of the damping force generated by the piston retract side valve 7, thereby reducing the frequency dependence of the damping force on the extension pressure ratio. The valve opening promotion mechanism 21 (low-speed valve 22) makes the frequency characteristics of the damping force of the piston extension side valve 6 consistent with the frequency characteristics of the damping force of the piston retract side valve 7. In this case, the low-speed valve 22 (low-speed disk 22A) opens at a piston speed lower than the piston speed at which the piston retract side valve 7 opens. As a result, the piston extension side valve 6 opens at a lower piston speed than the piston retract side valve 7. Preferably, adjustment is performed so that the piston retract side valve 7 and the piston extension side valve 6 are opened at the same time.

[0084] Figure 5 The relationship between the piston speed and the damping force of the shock absorber 1 according to the first embodiment, that is, the characteristics of the damping force with respect to the piston speed at a low frequency of the shock absorber 1 provided with the valve opening promotion mechanism 21 in the piston extension side valve 6 is shown. Figure 6 The relationship between the elongation-compression ratio of the attenuation force and the frequency is shown, that is, Figure 5 The change in the elongation-compression ratio of the damping force relative to the frequency at three different "piston speed a", "piston speed b", and "piston speed c" in FIG. In this case, Figure 6 The characteristic line 31 in Figure 5 The change in the elongation-compression ratio of the damping force at the "piston speed a" relative to the frequency. Similarly, Figure 6 The characteristic line 32 in FIG. Figure 5 The change in the elongation-compression ratio of the damping force at the "piston speed b" with respect to the frequency is shown by the characteristic line 33. Figure 5 Change of the elongation-compression ratio of the damping force at the "piston speed c" with respect to the frequency. Figure 6 and the aforementioned Fig.15 It can be seen that the extension-pressure ratio of the damping force relative to the change in frequency can be significantly reduced by providing the valve opening promotion mechanism 21. As a result, compared with a structure without the valve opening promotion mechanism 21 (low-speed valve 22), it is possible to achieve a ride comfort that is more robust to changes in road conditions and provides a sense of stability to the occupants.

[0085] As described above, the shock absorber 1 of the first embodiment includes the inner tube 4, the piston 5, the first oil passage 5A as the first passage, the piston extension side valve 6 as the first valve, the second oil passage 5B as the second passage, and the piston retraction side valve 7 as the second valve. In addition, the shock absorber 1 includes the outer tube 2 and the valve body 12. Furthermore, the shock absorber 1 has a piston extension side throttle hole 52 (see FIG. 1 ) as the first throttle hole provided in the first oil passage 5A of the piston 5. Fig.16), the third oil passage 12A as the third passage, the main body extension side valve 13 as the third valve, the fourth oil passage 12B as the fourth passage, the main body contraction side valve 14, the main body contraction side throttle hole 57 as the second throttle hole provided in the fourth oil passage 12B of the valve body 12 (refer to Fig.16 ).

[0086] On this basis, the frequency characteristic of the valve (for example, the piston extension side valve 6) having a larger frequency dependence of the damping force among the piston extension side valve 6 and the piston retract side valve 7 (or the main body retract side valve 14) is made to coincide with the frequency characteristic of the valve (for example, the piston retract side valve 7) having a smaller frequency dependence of the damping force. Therefore, in the valve (for example, the piston extension side valve 6) having a higher valve opening pressure among the piston extension side valve 6 and the piston retract side valve 7, a valve opening promotion mechanism 21 is provided, which coincides with the valve opening timing of the valve (for example, the piston retract side valve 7) having a lower valve opening pressure. In addition, in the valve (for example, the piston extension side valve 6) having a higher valve opening pressure among the piston extension side valve 6 and the main body retract side valve 14, a valve opening promotion mechanism 21 is provided, which coincides with the valve opening timing of the valve (for example, the piston retract side valve 7) having a lower valve opening pressure.

[0087] In this case, the valve with a higher valve opening pressure (for example, the piston extension side valve 6) of the piston extension side valve 6 and the piston retract side valve 7 opens when the piston speed is low compared with the valve with a lower valve opening pressure (for example, the piston retract side valve 7). In addition, the valve with a higher valve opening pressure (for example, the piston extension side valve 6) of the piston extension side valve 6 and the main body retract side valve 14 opens when the piston speed is low compared with the valve with a lower valve opening pressure (for example, the main body retract side valve 14). That is, the valve opening promotion mechanism 21 opens the valve with a higher valve opening pressure (for example, the piston extension side valve 6) when the piston speed is low compared with the valve with a lower valve opening pressure (for example, the piston retract side valve 7 and / or the main body retract side valve 14).

[0088] The valve opening promotion mechanism 21 is composed of, for example, a low-speed valve 22 (a low-speed disk 22A and a small-diameter disk 22B). That is, in the valve on the side with a higher valve opening pressure (for example, the piston extension side valve 6) of the piston extension side valve 6 and the piston contraction side valve 7, a low-speed valve 22 is provided, and the low-speed valve 22 has a smaller acting force (deformation resistance, anti-deformation force, valve closing force, force to maintain the valve closed) than the valve on the side with a lower valve opening pressure (for example, the piston contraction side valve 7 and / or the main body contraction side valve 14). For example, when the low-speed valve 22 is provided in the piston extension side valve 6, the low-speed valve 22 opens the first oil circuit 5A when the piston speed is low. For example, when the low-speed valve 22 is provided in the piston contraction side valve 7, the low-speed valve 22 opens the second oil circuit 5B when the piston speed is low. Figure 2 as well as Figure 3As shown, a gap 27 is formed between the low-speed valve 22 and the valve stacked on the low-speed valve 22 (ie, the second-stage valve 24 ).

[0089] The shock absorber 1 according to the first embodiment has the above-described structure, and its operation will be described below.

[0090] For example, the front end side (upper end side) of the piston rod 10 of the shock absorber 1 is attached to the body side of the vehicle (car), and the bottom cover 3 side, which is the base end side (lower end side) of the outer tube 2, is attached to the wheel side (axle side) of the vehicle. Thus, when vibration is generated during the running of the vehicle, the piston rod 10 is extended and contracted, and the damping force is generated by the valves 6 and 7 of the piston 5, etc., to damp the vibration at that time.

[0091] That is, when the piston rod 10 is in the retracting stroke, the bottom oil chamber C becomes a higher pressure state than the rod oil chamber B. And the oil (pressure oil) in the bottom oil chamber C flows into the rod oil chamber B via the second oil passage 5B of the piston 5 and the piston retracting side valve 7, generating a damping force. At this time, the oil equivalent to the volume of the piston rod 10 entering the inner tube 4 flows from the bottom oil chamber C via the fourth oil passage 12B of the valve body 12 and the main body retracting side valve 14 into the storage chamber A. In the storage chamber A, the gas sealed inside is compressed, and the volume of the piston rod 10 entering is absorbed.

[0092] On the other hand, when the piston rod 10 is in the extension stroke, the rod side oil chamber B becomes a higher pressure state than the bottom side oil chamber C. Then, the oil (pressure oil) in the rod side oil chamber B flows into the cylinder bottom side oil chamber C via the first oil passage 5A of the piston 5 and the piston extension side valve 6, generating a damping force. At this time, the oil equivalent to the amount of the entry volume (the amount of the exit volume) of the piston rod 10 entering (exiting) from the inner tube 4 flows from the reservoir chamber A into the bottom side oil chamber C via the third oil passage 12A of the valve body 12 and the main body extension side valve 13 (check valve).

[0093] Here, according to the first embodiment, in the piston extension side valve 6 having the second stage valve 24 as the valve with high valve opening pressure among the piston extension side valve 6 and the piston retraction side valve 7, a valve opening promotion mechanism 21 is provided, which is consistent with the valve opening timing of the piston retraction side valve 7 as the valve with low valve opening pressure. Therefore, for example, (compared with the conventional structure without the valve opening promotion mechanism 21), the low speed valve 22 of the piston extension side valve 6 can be opened at a low piston speed, and the rigidity in the state where the piston speed becomes high can be further improved by the second stage valve 24. Thus, the damping force in the middle and high speed range of the extension side can be ensured on the basis of reducing the frequency dependence of the extension pressure ratio of the damping force. Therefore, compared with the conventional technology (structure without the valve opening promotion mechanism 21), it is possible to achieve a riding comfort that is more robust to changes in road conditions and provides a stable feeling to the occupants. That is, a stable damping force characteristic of the sprung vehicle can be obtained regardless of the road surface, and the occupants can continue to ride the vehicle without feeling uncomfortable.

[0094] According to the first embodiment, the piston extension side valve 6 is configured so that the frequency dependence of the damping force is equivalent to that of the piston retraction side valve 7. That is, the piston extension side valve 6, which is a valve having a large frequency dependence of the damping force, is configured to be consistent with the piston retraction side valve 7, which is a valve having a small frequency dependence of the damping force. Therefore, the frequency dependence of the extension-pressure ratio of the damping force can be reduced. As a result, a ride comfort that is more robust to changes in road conditions and provides a sense of stability to the occupants can be achieved. That is, a stable damping force characteristic on the sprung portion of the vehicle can be obtained regardless of the road surface, and the occupants can continue to ride the vehicle without feeling any discomfort.

[0095] According to the first embodiment, the piston extension side valve 6, which is a valve having a high valve opening pressure, opens when the piston speed is low, compared to the piston retraction side valve 7, which is a valve having a low valve opening pressure. Therefore, while the piston extension side valve 6 is opened at a low piston speed, the valve rigidity in the medium and high speed range can be increased to obtain a large differential pressure. Therefore, while suppressing the reduction of the damping force of the piston extension side valve 6, the frequency dependence of the damping force on the extension pressure ratio can be reduced by opening the piston extension side valve 6 at a low piston speed.

[0096] According to the first embodiment, the piston extension side valve 6 is provided with a low speed valve 22, which has a smaller force than the piston retracting side valve 7 and opens the first oil passage 5A when the piston speed is low. Therefore, the initial characteristics of the piston extension side valve 6 and the rigidity in the medium and high speed range can be adjusted independently, so that the frequency dependence of the extension pressure ratio of the damping force can be reduced while ensuring the degree of freedom of adjustment of the extension side damping force.

[0097] According to the first embodiment, the gap 27 is formed between the low speed valve 22 (low speed disk 22A) and the second stage valve 24. Therefore, the low speed valve 22 (low speed disk 22A) is easily displaced (deformed) toward the gap 27. Thus, the low speed valve 22 can be opened when the piston speed is low.

[0098] According to the first embodiment, in the piston extension side valve 6, which is the valve with a high valve opening pressure in the piston extension side valve 6 and the main body contraction side valve 14, there is provided a valve opening promotion mechanism 21 which is consistent with the valve opening timing of the piston contraction side valve 7, which is the valve with a low valve opening pressure. Therefore, it is possible to improve the rigidity in the medium and high speed range while the piston extension side valve 6 opens the valve at a low piston speed. Thus, it is possible to ensure the damping force in the medium and high speed range on the extension side on the basis of reducing the frequency dependence of the extension pressure ratio of the damping force. Therefore, compared with the prior art (a structure without a valve opening promotion mechanism 21), it is possible to achieve a ride comfort that is more robust to changes in road conditions and provides a sense of stability to the occupants. That is, it is possible to obtain a stable damping force characteristic on the sprung portion of the vehicle regardless of the road surface, and the occupants can continue to ride the vehicle without feeling any discomfort.

[0099] In addition, the low speed valve 22 of the first embodiment determines the size of the gap 27 between the low speed disk 22A and the second stage valve 24 according to the plate thickness of the small diameter disk 22B. And by reducing the gap 27 between the small diameter disk 22B and the second stage valve 24, the piston extension side valve 6 is shifted from an earlier timing (piston speed) to a region with high valve rigidity, and a large damping force can be generated. However, from the viewpoint of mass production and strength, it is difficult to reduce the plate thickness of the small diameter disk 22B by more than a certain amount, which may become a restriction on the degree of freedom of damping force generation.

[0100] Therefore, in Figure 7 In the modified example shown, the low speed valve 41 is provided with a clearance adjustment disk 42 between the small diameter disk 22B and the second stage valve 24, and the clearance adjustment disk 42 makes the interval of the clearance 27 different on the inner diameter side and the outer diameter side. Moreover, the clearance adjustment disk 42 makes the size of the clearance 27 larger on the inner diameter side and smaller on the outer diameter side. That is, in the modified example, the low speed valve 41 includes the clearance adjustment disk 42 and the small diameter disk 22B as the fifth valve (clearance adjustment valve). The clearance adjustment disk 42 has a protrusion 42A, which protrudes toward the low speed disk 22A of the piston extension side valve 6 and has an axial width larger than other parts. The small diameter disk 22B is provided between the low speed disk 22A of the piston extension side valve 6 and the clearance adjustment disk 42. The diameter of the small diameter disk 22B is smaller than the diameters of the low speed disk 22A and the clearance adjustment disk 42.

[0101] As described above, in the modified example, the gap adjustment disk 42 whose thickness varies on the radially outer side is provided between the small-diameter disk 22B and the second-stage valve 24. Thus, even if the plate thickness of the small-diameter disk 22B is increased, the gap 27 between the low-speed disk 22A and the second-stage valve 24 can be set smaller. Therefore, the plate thickness of the small-diameter disk 22B can be set to a thickness that can ensure mass productivity and strength, and the degree of freedom in generating the damping force can be increased.

[0102] That is, the low speed valve 41 of the modified example is provided with a clearance adjustment disk 42 in addition to the low speed disk 22A and the small diameter disk 22B. Moreover, the clearance adjustment disk 42 has a protrusion 42A protruding toward the low speed disk 22A. Therefore, the plate thickness of the small diameter disk 22B can be increased, and the clearance 27 between the low speed disk 22A and the clearance adjustment disk 42 (protrusion 42A) of the piston extension side valve 6 can be reduced. Thus, it is possible to achieve both "ensuring the mass production and strength of the small diameter disk 22B" and "ensuring the degree of freedom in adjusting the damping force of the piston extension side valve 6".

[0103] In addition, in the modification, the case where the protrusion 42A is provided on the gap adjustment disk 42 is described as an example. However, the present invention is not limited thereto, and the gap adjustment disk may have different plate thicknesses at the inner diameter portion and the outer diameter portion, for example. That is, the gap adjustment disk may have a plate thickness at the outer diameter portion greater than that at the inner diameter portion. In addition, the protrusion may be formed integrally with the disk by stamping, or may be formed integrally with the disk by welding a component different from the disk to a portion corresponding to the protrusion.

[0104] then, Figures 8 to 11 The second embodiment is characterized in that a first seat portion for the low-speed valve to be unseated or seated and a second seat portion for the main valve (second-stage valve) to be unseated or seated are provided. In addition, in the second embodiment, the same reference numerals are given to the same components as those in the first embodiment, and their descriptions are omitted.

[0105] In the second embodiment, the piston extension side valve 6 includes a low-speed valve 61 and a second-stage valve 62 as a main valve. The valve opening promotion mechanism 21 is composed of the low-speed valve 61. That is, the piston extension side valve 6 is composed of the low-speed valve 61, which has low valve rigidity and contributes to the damping force in the low-speed range of the valve opening from the low speed, and the second-stage valve 62, which has high rigidity compared with the low-speed valve 61 and contributes to the damping force in the medium and high speed range. The low-speed valve 61 and the second-stage valve 62 are arranged in series in the hydraulic circuit.

[0106] The low-speed valve 61 is composed of two low-speed disks 61A and 61B and a retainer 61C. The second-stage valve 62 is composed of four disks 62A, 62B, 62C, and 62D. The retainer 61C is provided between the low-speed disk 61B arranged on the back side (lower surface side) and the disk 62A of the second-stage valve 62. In the second embodiment, the seats 63 and 64 that are seated or unseated by the low-speed valve 61 and the second-stage valve 62 are different. That is, the piston 5 is provided with an inner seat 63 as a first seat portion on which the low-speed valve 61 is seated or unseated, and an outer seat 64 as a second seat portion located radially outward of the inner seat 63 and on which the second-stage valve 62 is seated or unseated. The inner seat 63 that the low-speed valve 61 contacts is arranged on the inner diameter side of the outer seat 64 that the second-stage valve 62 contacts. Both the inner seat 63 and the outer seat 64 are annular seat shapes.

[0107] The low speed valve 61 is provided for the purpose of opening the valve from a lower speed range when the piston extension side valve 6 is extended. Therefore, the height of the "seat surface 63A of the inner seat portion 63 where the low speed valve 61 is unseated or seated" and the "support surface 65A of the support portion 65 abutted by the inner diameter side of the low speed valve 61", that is, the step difference (Japanese: ) (height difference) is preferably as small as possible as allowed by manufacturing variations. In addition, the support surface 65A that the inner diameter side of the low-speed valve 61 abuts is also used as a portion that supports the inner diameter side of the second-stage valve 62. That is, the low-speed valve 61 is first stacked on the support surface 65A, and then the second-stage valve 62 is arranged on the back side of the low-speed valve 61. Therefore, a step H as a height difference is provided between the support surface 65A and the seat surface 64A of the outer seat portion 64.

[0108] Furthermore, the second-stage valve 62 is sometimes also given a preset (pre-pressure, preset load). In this case, the size of the step H between the support surface 65A and the seat surface 64A of the outer seat portion 64 is set to be greater than the thickness of the low-speed valve 61 (two low-speed disks 61A, 61B and the retainer 61C). The low-speed disk 61A in contact with the inner seat portion 63 of the two low-speed disks 61A and 61B constituting the low-speed valve 61 is a slit disk having a pair of cutouts 61A1 provided on the outer peripheral edge. The cutout 61A1 corresponds to the first throttle hole (throttle hole on the piston extension side). The low-speed valve 61 contributes to the characteristics of the low-speed range.

[0109] In addition, depending on the requirements of the vehicle, the slit disk (low-speed disk 61A) may not be provided. In addition, although not shown in the figure, a disk having the same diameter as the low-speed valve 61 (low-speed disk 61A, 61B) or a valve having different plate thicknesses at the inner diameter portion and the outer diameter portion (for example, a disk having the same diameter as the low-speed valve 61 (low-speed disk 61A, 61B) may be arranged on the back side (lower surface) of the retainer 61C, for example, to limit the lift amount of the low-speed valve 61 (low-speed disk 61A, 61B). Figure 7 clearance adjustment disk 42).

[0110] As the damping force in the low speed range of the piston extension side valve 6, it is desired to increase the contribution of the damping force generated by the low speed valve 61. Therefore, the disk 62A in contact with the outer seat portion 64 among the four disks 62A, 62B, 62C, and 62D constituting the second stage valve 62 is a slit disk having a pair of cutouts 62A1 provided on the outer peripheral edge. In this case, the second stage valve 62 ensures a sufficient orifice area by the disk 62A (slit disk), thereby reducing the contribution of the damping force in the low speed range.

[0111] The second stage valve 62 has the function of generating a damping force in the middle and high speed range of the piston extension side valve 6. Therefore, the rigidity of the second stage valve 62 is adjusted by parameters such as the number of stacked sheets of the disks 62A, 62B, 62C, and 62D, the plate thickness, and the diameter size of the retainer 25 on the back side. In addition, it is also possible to adjust the desired characteristics by giving a preload by giving a step difference to the second stage valve 62. In addition, the inner seat portion 63 of the low speed valve 61 is not limited to a circular ring-shaped seat shape, and can also be set to a seat shape with different diameters according to the characteristics of the low speed range to be obtained.

[0112] The second embodiment includes the low speed valve 61 and the second stage valve 62 as described above, and its basic operation is not particularly different from that of the first embodiment. That is, the second embodiment can also obtain a stable damping force characteristic of the sprung vehicle regardless of the road surface, similarly to the first embodiment. Fig.10 The characteristics of the damping force with respect to the piston speed according to the second embodiment are shown. Fig.11 express Fig.10 The change in the elongation-compression ratio of the damping force relative to the frequency at three different piston speeds (piston speed a, piston speed b, piston speed c). Fig.11 and the aforementioned Fig.15 It can be seen that the elongation-pressure ratio of the damping force relative to the change in frequency can be significantly reduced by providing the valve opening promotion mechanism 21. As a result, compared with a structure without the valve opening promotion mechanism 21 (low-speed valve 61), it is possible to achieve a ride comfort that is more robust to changes in road conditions and provides a sense of stability to the occupants.

[0113] In addition, according to the aforementioned Figure 5 As well as the above Fig.10The "damping force-piston speed line diagram" shown in the figure cannot strictly determine the valve opening point. That is, even if the inflection point of the damping force on the extension side and the inflection point of the damping force on the contraction side appear to be consistent on the "damping force-piston speed line diagram", the valve opening timing is not necessarily consistent. For example, in the valve opening promotion mechanism 21 of the first embodiment, since the valve rigidity is made nonlinear and the valve rigidity is only reduced in the low-speed range, and the rigidity is increased in the medium and high-speed range, a clear valve opening point does not appear on the damping force-piston speed line diagram. In addition, in the case of a structure such as the low-speed valve 61 and the second-stage valve 62 are arranged in series as in the second embodiment, the valve opening point of the second-stage valve 62 with a high valve opening pressure appears on the line diagram, but the valve opening point of the low-speed valve 61 does not appear clearly. Therefore, it is difficult to determine the valve opening point on the "damping force-piston speed line diagram". In order to determine the valve opening point, it is necessary to calculate it based on the throttle hole, the valve pressure area, and the valve rigidity, or to calculate the valve opening point by measuring the frequency characteristics at each piston speed. That is, the valve opening timing (piston speed) is determined by the differential pressure between the upstream and downstream of the valve, the valve rigidity, the setting load, the pressure-bearing area, and the seat shape. Therefore, it needs to be determined by calculation rather than based on the "damping force-piston speed diagram".

[0114] In the first embodiment, the piston extension side valve 6 is set as the first valve, and the piston retracting side valve 7 is set as the second valve. However, the present invention is not limited thereto. For example, the piston extension side valve may be set as the second valve, and the piston retracting side valve may be set as the first valve. This is also the same for the second embodiment and the modified example.

[0115] In the first embodiment, the main body extension side valve 13 is set as the third valve, and the main body contraction side valve 14 is set as the fourth valve. However, the present invention is not limited thereto. For example, the main body extension side valve may be set as the fourth valve, and the main body contraction side valve may be set as the third valve. This is also the same for the second embodiment and the modified example.

[0116] In the first embodiment, the following case is used as an example for explanation: in the extension stroke of the piston rod 10, the piston extension side valve 6 on the lower side of the piston 5 applies resistance to the oil (working fluid) to generate a damping force, and in the reduction stroke of the piston rod 10, the piston contraction side valve 7 on the upper side of the piston 5 applies resistance to the oil (working fluid) to generate a damping force. However, this is not limited to this. For example, the piston extension side valve on the upper side of the piston may be set as a check valve, and the damping force may be generated in the reduction stroke of the piston rod by the main body contraction side valve as the fourth valve provided on the valve body. This is also the same for the second embodiment and the modified example.

[0117] In the first embodiment, the following case is used as an example for explanation: in the piston extension side valve 6, which is the valve with a high valve opening pressure between the piston extension side valve 6 and the main body retraction side valve 14, a valve opening promotion mechanism 21 is provided, which is consistent with the valve opening timing of the piston retraction side valve 7, which is the valve with a low valve opening pressure. However, this is not limited to this. For example, in the case where the valve with a high valve opening pressure between the piston extension side valve and the main body retraction side valve is the main body retraction side valve, a valve opening promotion mechanism can also be provided in the main body retraction side valve, which is consistent with the valve opening timing of the piston extension side valve, which is the valve with a low valve opening pressure. This is also the same for the second embodiment and the modified example.

[0118] In the first embodiment, a multi-tube type shock absorber 1 composed of an outer tube 2 and an inner tube 4 is described as an example. However, the present invention is not limited to this, and can also be applied to a shock absorber composed of a single-tube tube member (cylinder). In this case, a valve opening promotion mechanism can be provided in the valve with higher rigidity among the first valve and the second valve provided in the piston. This is also the same for the second embodiment and the modified example.

[0119] In addition, in each embodiment and modification, as a representative example of the buffer, a buffer installed in a car is described. However, it is not limited to this, for example, it can also be applied to a buffer installed in a railway vehicle. In addition, it is not limited to vehicles such as automobiles and railway vehicles, and it can be applied to various buffers used in various machines, structures, buildings, etc. that become vibration sources.

[0120] Furthermore, each embodiment and modification example are merely examples, and it is of course possible to partially replace or combine the structures shown in different embodiments and modification examples.

[0121] According to the above-described embodiments and / or variations (hereinafter referred to as "embodiments"), a valve opening promotion mechanism is provided in the valve on the side with higher valve opening pressure among the first valve and the second valve, which is consistent with the valve opening timing of the valve on the side with lower valve opening pressure. Therefore, the valve on the side with higher valve opening pressure can open the valve at a lower piston speed while improving the rigidity in the medium and high speed range. As a result, the damping force in the medium and high speed range of the valve on the side with higher valve opening pressure can be ensured on the basis of reducing the frequency dependence of the extension-pressure ratio of the damping force. Therefore, compared with a structure in which no valve opening promotion mechanism is provided, a ride comfort that is more robust to changes in road conditions and provides a sense of stability to the occupants can be achieved. That is, a stable damping force characteristic on the sprung portion of the vehicle can be obtained regardless of the road surface, and the occupants can continue to ride the vehicle without feeling any discomfort.

[0122] According to the embodiment, the frequency characteristic of the valve with a larger frequency dependence of the damping force of the first valve and the second valve is configured to be consistent with the frequency characteristic of the valve with a smaller frequency dependence of the damping force. Therefore, the frequency dependence of the extension-pressure ratio of the damping force can be reduced. As a result, a riding comfort that is more robust to changes in road conditions and provides a sense of stability to the occupants can be achieved. In other words, a damping force characteristic that is stable on the sprung portion of the vehicle can be obtained regardless of the road surface, and the occupants can continue to ride the vehicle without feeling any discomfort.

[0123] According to the embodiment, the valve with a higher valve opening pressure among the first valve and the second valve opens at a lower piston speed than the valve with a lower valve opening pressure. Therefore, the valve with a higher valve opening pressure can open at a lower piston speed while improving the rigidity in the medium and high speed range. Thus, the damping force in the medium and high speed range of the valve with a higher valve opening pressure can be ensured on the basis of reducing the frequency dependence of the extension pressure ratio of the damping force.

[0124] According to the embodiment, a low-speed valve is provided in the valve with a higher valve opening pressure in the first valve and the second valve. The low-speed valve has a smaller force than the valve with a lower valve opening pressure, and opens the first passage or the second passage when the piston speed is low. Therefore, the valve with a higher valve opening pressure can open the valve at a lower piston speed while improving the rigidity in the medium and high speed range. Thus, the frequency dependence of the extension-pressure ratio of the damping force can be reduced while ensuring the degree of freedom of the damping force in the medium and high speed range of the valve with a higher valve opening pressure.

[0125] According to the embodiment, a gap is formed between the "low speed valve" and the "valve stacked on the low speed valve". Therefore, the low speed valve is easily displaced (deformed) toward the gap side. Thus, the low speed valve can be opened when the piston speed is low.

[0126] According to the embodiment, the low-speed valve includes: a fifth valve having a protruding portion protruding toward the second valve and having a larger axial width than other portions; and a small-diameter disk between the second valve and the fifth valve. Therefore, the plate thickness of the small-diameter disk can be increased, and the gap between the second valve and the fifth valve (protruding portion) can be reduced. Thus, it is possible to achieve both "ensuring mass production and strength of the small-diameter disk" and "ensuring the degree of freedom in adjusting the damping force".

[0127] According to the embodiment, a valve opening promotion mechanism that is consistent with the valve opening timing of the valve with a low valve opening pressure is provided in the valve with a higher valve opening pressure among the first valve and the fourth valve. Therefore, the valve with a higher valve opening pressure can open the valve at a lower piston speed while improving the rigidity in the medium and high speed range. As a result, the damping force in the medium and high speed range of the valve with a higher valve opening pressure can be ensured on the basis of reducing the frequency dependence of the extension-pressure ratio of the damping force. Therefore, compared with a structure in which a valve opening promotion mechanism is not provided, a ride comfort that is more robust to changes in road conditions and provides a sense of stability to the occupants can be achieved. That is, a stable damping force characteristic of the sprung vehicle can be obtained regardless of the road surface, and the occupants can continue to ride the vehicle without feeling any discomfort.

[0128] This application claims priority based on Japanese Patent Application No. 2022-156052 filed on September 29, 2022. The entire disclosure of Japanese Patent Application No. 2022-156052 filed on September 29, 2022, including the specification, claims, drawings, and abstract, is incorporated herein by reference in its entirety.

[0129] Description of Reference Numerals

[0130] 1: Buffer; 2: Outer tube; 4: Inner tube; 5: Piston; 5A: First oil circuit (first passage); 5B: Second oil circuit (second passage); 6: Piston extension side valve (first valve); 7: Piston contraction side valve (second valve); 12: Valve body; 12A: Third oil circuit (third passage); 12B: Fourth oil circuit (fourth passage); 13: Main body extension side valve (third valve); 14: Main body contraction side valve (fourth valve); 21: Valve opening promotion mechanism; 22, 41, 61: Low-speed valve; 22B: Small-diameter disk; 42: Clearance adjustment disk (fifth valve); 42A: Protrusion; 52: Piston extension side throttle hole (first throttle hole); 57: Main body contraction side throttle hole (second throttle hole); A: Storage chamber; B: Rod side oil chamber (first chamber); C: Bottom side oil chamber (second chamber).

Claims

1. A buffer, comprising: An inner cylinder, in which a working fluid is sealed; A piston is slidably disposed in the inner cylinder and divides the inner cylinder into a first chamber and a second chamber; A first passage, disposed on the piston; a first valve for opening and closing the first passage; a second passage, disposed in the piston; as well as The second valve opens and closes the second passage. A valve opening promotion mechanism is provided in the valve having a higher valve opening pressure among the first valve and the second valve, and the valve opening promotion mechanism matches the valve opening timing with the valve having a lower valve opening pressure.

2. A buffer, comprising: An inner cylinder, in which a working fluid is sealed; A piston is slidably disposed in the inner cylinder and divides the inner cylinder into a first chamber and a second chamber; A first passage, disposed on the piston; a first valve for opening and closing the first passage; a second passage, disposed in the piston; as well as The second valve opens and closes the second passage. The damper is configured so that the frequency characteristic of the valve having greater frequency dependency of the damping force of the first valve and the second valve matches the frequency characteristic of the valve having less frequency dependency of the damping force.

3. The buffer according to claim 1, wherein: The valve having a higher valve opening pressure among the first valve and the second valve opens when the piston speed is lower than that of the valve having a lower valve opening pressure.

4. A buffer, comprising: An inner cylinder, in which a working fluid is sealed; A piston is slidably disposed in the inner cylinder and divides the inner cylinder into a first chamber and a second chamber; A first passage, disposed on the piston; a first valve for opening and closing the first passage; a second passage, disposed in the piston; as well as The second valve opens and closes the second passage. A low-speed valve is provided in the valve with a higher valve opening pressure of the first valve and the second valve. The low-speed valve has a smaller force than the valve with a lower valve opening pressure and opens the first passage or the second passage when the piston speed is low.

5. The buffer according to claim 4, wherein: A gap is formed between the low-speed valve and a valve stacked on the low-speed valve.

6. The buffer according to claim 4, wherein: The low speed valve includes: a fifth valve having a protruding portion protruding toward the second valve and having an axial width greater than other portions; and a small diameter disk located between the second valve and the fifth valve and having a smaller diameter than the second valve and the fifth valve.

7. A buffer, comprising: An inner cylinder, in which a working fluid is sealed; A piston is slidably disposed in the inner cylinder to divide the inner cylinder into a first chamber and a second chamber; An outer cylinder is arranged outside the inner cylinder and forms a storage chamber between the outer cylinder and the inner cylinder; a valve body, disposed between the storage chamber and the second chamber; A first passage, disposed on the piston; a first valve for opening and closing the first passage; A first throttle hole is disposed in the first passage; a second passage, disposed in the piston; a second valve, for opening and closing the second passage; a third passage, disposed in the valve body; a third valve, for opening and closing the third passage; a fourth passage, disposed in the valve body; a fourth valve, for opening and closing the fourth passage; as well as A second throttle hole is provided in the fourth passage, A valve opening promotion mechanism is provided in the valve having a higher valve opening pressure among the first valve and the fourth valve, and the valve opening timing of the valve opening promotion mechanism is matched with that of the valve having a lower valve opening pressure.

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