SHOCK ABSORBERS

Abstract

The present invention provides a shock absorber capable of achieving a damping force characteristic such that a sprung side of a vehicle is stabilized regardless of a road surface. A shock absorber includes an inner tube, a piston, a first oil passage, a piston extension-side valve, a second oil passage, and a piston retraction-side valve. The shock absorber is configured to cause the piston extension-side valve or the piston retraction-side valve, whichever corresponds to a damping force with a higher frequency dependency, to match the other valve corresponding to a damping force with a lower frequency dependency.To achieve this, for example, the piston-extending-side valve or the piston-retracting-side valve, depending on which is set to a higher valve opening pressure (for example, the piston-extending-side valve), is provided with a valve opening promotion mechanism that aligns a valve opening timing of this valve with a valve opening timing of the other valve, which is set to a lower valve opening pressure (for example, the piston-retracting-side valve).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a shock absorber that reduces vibrations of a vehicle, for example a motor vehicle. TECHNICAL BACKGROUND

[0002] Vehicles, such as four-wheeled motor vehicles, are equipped with shock absorbers (dampers) between the sprung side of the vehicle body and each unsprung side of the wheels. A shock absorber disclosed in PTL 1 includes poppet valves provided on the bottom and top sides of a piston, respectively. The poppet valve on the bottom side of the piston is opened based on an increase in the differential pressure of an oil chamber on the top side of the piston versus an oil chamber on the bottom side of the piston when a rod moves to an extension side. The poppet valve on the top side of the piston is opened based on an increase in the differential pressure of the oil chamber on the bottom side of the piston versus the oil chamber on the top side of the piston when the rod moves to a retraction side. LIST OF REFERENCES PATENT LITERATURE

[0003] PTL 1: Japanese Patent Laid-Open No. 2020-34068 PRESENTATION OF THE INVENTIONTECHNICAL PROBLEM

[0004] When the shock absorber is then installed (implemented or used) in the vehicle, it should be adapted to that vehicle. In particular, the shock absorber undergoes adjustment (tuning) of its damping force so that the desired ride comfort can be achieved in the vehicle in which this shock absorber is installed. In this case, the shock absorber is adjusted towards the desired ride comfort mainly by adjusting the damping force in relation to the piston speed on the extension side and the retraction side. However, adjusting the damping force solely in relation to the piston speed on the extension side and the retraction side may lead to reduced ride comfort depending on the road surface conditions and achieve comfortable driving only on limited road surfaces.

[0005] One of the objects of the present invention is to provide a shock absorber capable of achieving such a damping force characteristic that a sprung side of a vehicle is stabilized regardless of a road surface. SOLUTION TO THE PROBLEM

[0006] According to the present invention, a shock absorber preferably comprises an inner tube in which a hydraulic fluid is enclosed, a piston slidably provided in the inner tube and dividing the interior of the inner tube into a first chamber and a second chamber, a first passage provided on the piston, a first valve configured to open and close the first passage, a second passage provided on the piston, and a second valve configured to open and close the second passage. One of the first valve and the second valve, whichever is set to a higher valve opening pressure, is provided with a valve opening promotion mechanism configured to align the valve opening timing of that valve with the valve opening timing of the other valve, which is set to a lower valve opening pressure.

[0007] Furthermore, a shock absorber according to the present invention preferably comprises an inner tube in which a hydraulic fluid is enclosed, a piston slidably provided in the inner tube and dividing the interior of the inner tube into a first chamber and a second chamber, a first passage provided on the piston, a first valve configured to open and close the first passage, a second passage provided on the piston, and a second valve configured to open and close the second passage. The shock absorber is configured to cause a frequency characteristic of the first valve or the second valve, whichever corresponds to a damping force with a higher frequency dependency, to match a frequency characteristic of the other valve corresponding to a damping force with a lower frequency dependency.

[0008] Further, a shock absorber according to the present invention preferably comprises an inner tube in which a hydraulic fluid is sealed, a piston slidably provided in the inner tube and dividing the interior of the inner tube into a first chamber and a second chamber, a first passage provided on the piston, a first valve configured to open and close the first passage, a second passage provided on the piston, and a second valve configured to open and close the second passage.The first valve or the second valve, whichever is set to a higher valve opening pressure, is provided with a slow-action valve subjected to a weaker preload force compared to the other valve set to a lower valve opening pressure and configured to open the first port or the second port when a piston speed is low.

[0009] Furthermore, a shock absorber according to the present invention preferably comprises an inner tube in which a hydraulic fluid is enclosed, a piston slidably provided in the inner tube and dividing the interior of the inner tube into a first chamber and a second chamber, an outer tube provided outside the inner tube and defining a storage chamber between the outer tube and the inner tube, a valve body provided between the storage chamber and the second chamber, a first passage provided on the piston, a first valve (for example, a piston extension valve) configured to open and close the first passage, an orifice plate provided on the first passage, a second passage provided on the piston, a second valve (for example, a piston retraction valve) configured to open and close the second passage, a third passage,provided on the valve body, a third valve (for example, a suction valve) configured to open and close the third channel, a fourth channel provided on the valve body, a fourth valve (for example, a body retraction valve) configured to open and close the fourth channel, and a second orifice provided on the fourth channel. The first valve or the fourth valve, depending on which is set to a higher valve opening pressure, is provided with a valve opening promotion mechanism configured to align a valve opening timing of this valve with a valve opening timing of the other valve, which is set to a lower valve opening pressure (for example, when the valve opening pressure of the first valve is greater than the fourth valve,the first valve is aligned with the valve opening time of the second valve).

[0010] According to one aspect of the present invention, a shock absorber may adopt a damping force characteristic such that a sprung side of a vehicle is stabilized regardless of the road surface. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a vertical cross-sectional view showing a shock absorber according to a first embodiment. Fig. 2 is an enlarged cross-sectional view of a piston, a first valve and a second valve in Fig. 1. Fig. 3 is an enlarged view of the Fig. 2 part marked (III). Fig. 4 is an exploded perspective view of the piston, the first valve and the like. Fig. 5 is a characteristic diagram showing the relationship between a piston speed and a damping force at the time of low-frequency vibration according to the first embodiment. Fig. 6 is a characteristic diagram showing the relationship between an extension / contraction ratio (a rebound / impact ratio) of the damping force and a frequency according to the first embodiment. Fig. 7 is a cross-sectional view in a similar position to Fig. 3, which shows a piston, a first valve and the like according to a modification. Fig. 8 is a cross-sectional view in a similar position to Fig. 3, which shows a piston, a first valve and the like according to a second embodiment. Fig. 9 is an exploded perspective view of the piston, the first valve and the like according to the second embodiment. Fig. 10 is a graph of characteristics showing the relationship between the piston speed and the damping force at the time of low-frequency vibration according to the second embodiment. Fig. 11 is a characteristic diagram showing the relationship between the extension / contraction ratio (the rebound / shock ratio) of the damping force and the frequency according to the second embodiment. Fig. 12 is a characteristic diagram showing the relationship between a damping force in an orifice area and the frequency. Fig. 13 is a characteristic diagram showing the relationship between a damping force in a valve area and the frequency. Fig. 14 is a graph showing characteristics of the relationship between piston speed and damping force according to a comparative example. Fig. 15 is a characteristic graph showing the relationship between the rebound / extension ratio (the rebound / shock ratio) of the damping force and the frequency according to the comparative example. Fig. 16 shows the hydraulic circuit diagrams of a single-tube shock absorber and a twin-tube shock absorber. Fig. Figure 17 is a diagram illustrating ride comfort (a vehicle behavior) in an ideal condition. Fig. Figure 18 is a diagram illustrating ride comfort (a vehicle behavior) that is to be improved. DESCRIPTION OF THE EMBODIMENTS

[0011] In the following description, a shock absorber according to an embodiment will be described with reference to the accompanying drawings, giving an example in which it is applied to a hydraulic shock absorber installed in a vehicle such as a four-wheeled motor vehicle.

[0012] The Fig. 1 to 6 show a first embodiment. In Fig. 1, a shock absorber 1 is, for example, a hydraulic shock absorber for a vehicle such as an automobile. The shock absorber 1, together with a suspension spring (not shown) formed of, for example, a coil spring, constitutes a suspension device for the vehicle. In the following description, the shock absorber 1 will be described with reference to one axial end side and one opposite axial end side of the shock absorber 1 as a "lower end" side and one "upper end" side, respectively, but the one axial end side and the opposite axial end side of the shock absorber 1 may be the "upper end" side and the "lower end" side, respectively.

[0013] The shock absorber 1 includes 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 in a bottomed tubular shape and forms the outer shell of the shock absorber 1. The lower end side of the outer tube 2, corresponding to one end side, is closed by welding a bottom cap 3, and the upper end side of the outer tube 2, corresponding to the opposite end side, is opened. At the upper end portion of the outer tube 2, for example, a plurality of crimped portions 2A are provided. The crimped portions 2A are formed by radially bending the outer tube 2 inward by crimping. The opening of the outer tube 2 at its upper end side is closed by a rod guide 8 and a rod seal 9.

[0014] The inner tube 4 is coaxially arranged within the outer tube 2. The inner tube 4, together with the outer tube 2, forms a double-tube shock absorber (a cylinder device). Oil fluid (hydraulic oil) as the hydraulic fluid is enclosed within the inner tube 4 and the outer tube 2. The oil fluid as the hydraulic fluid is not limited to oil, but may be, for example, water mixed with an additive. The lower end of the inner tube 4 is fixedly connected to the outer peripheral side of the valve body 12, and the upper end of the inner tube 4 is closed by the rod guide 8.

[0015] The inner tube 4 forms (defines) an annular storage chamber A between the inner tube 4 and the outer tube 2. Conversely, the outer tube 2 forms the storage chamber A between the outer tube 2 and the inner tube 4. Gas is enclosed in the storage chamber A together with the oil fluid, which is the hydraulic fluid. This gas can be, for example, air at atmospheric pressure or a compressed nitrogen gas. The storage chamber A acts as a reservoir or accumulator, balancing the inlet and outlet of the piston rod 10. The valve body 12 is provided between the bottom cap 3 and the inner tube 4 at a position on the lower end side of the inner tube 4.

[0016] The piston 5 is slidably arranged in the inner tube 4. The piston 5 divides the interior of the inner tube 4 into two chambers, namely a rod-side oil chamber B corresponding to a first chamber, and a bottom-side oil chamber C corresponding to a second chamber. A plurality of oil channels 5A and a plurality of oil channels 5B are provided on the piston 5. The oil channels 5A and 5B can establish communication between the rod-side oil chamber B and the bottom-side oil chamber C. Among the plurality of oil channels 5A and 5B, the first oil channels 5A are provided as a first channel in the Fig. 1 to 4 and the second oil channels 5B as a second channel in Fig. 4 shown.

[0017] The oil passages 5A and 5B form passages that allow the flow of hydraulic fluid (oil fluid) to be directed from one of the oil chambers B and C in the inner tube 4 to the other in accordance with the movement of the piston 5. In other words, the first oil passages 5A as the first passage and the second oil passages 5B as the second passage establish communication between the rod-side oil chamber B, which corresponds to the first chamber, and the bottom-side oil chamber C, which corresponds to the second chamber, in accordance with the movement of the piston 5. The first oil passages 5A and the second oil passages 5B are flow passages in which a flow of hydraulic fluid (oil fluid) is generated in accordance with the movement of the piston 5.

[0018] A valve 6 is provided on the piston 5. The valve 6 includes, for example, one or more discs (disk valve(s)). Specifically, the valve 6 serving as an extension-side (rebound-side) damping valve is provided on the underside of the piston 5. The extension-side valve 6 (hereinafter referred to as the piston extension-side valve 6) exerts a resistive force on the oil fluid flowing in the first oil passages 5A from the rod-side oil chamber B to the bottom-side oil chamber C when the piston 5 is displaced upward along the inner tube 4 during an extension stroke (a rebound stroke) of the piston rod 10. This generates a predetermined damping force during the extension stroke of the piston rod 10.

[0019] In other words, the piston extension-side valve 6 generates the damping force by controlling the flow of hydraulic fluid (oil fluid) generated in accordance with a sliding movement of the piston 5 in the inner tube 4. The piston extension-side valve 6 corresponds to a first valve that opens and closes the first oil passages 5A serving as the first passage. As shown in Fig. 16, which will be described later, the first oil passage 5A is provided with a piston-extension-side orifice plate 52 that functions as a throttle (orifice) when necessary. The piston-extension-side orifice plate 52, which corresponds to a first orifice plate, may be provided on the piston-extension-side valve 6 or on the seat side (the piston 5 side).

[0020] In addition to the piston-side extension valve 6, a valve 7 is provided on the piston 5. The valve 7 includes, for example, one or more discs (disk valve(s)). Specifically, the valve 7 serving as a retraction-side (shock-side) damping valve is provided on the upper side surface of the piston 5. The retraction-side valve 7 (hereinafter referred to as the piston retraction-side valve 7) exerts a resistive force on the oil fluid flowing in the second oil passages 5B from the bottom-side oil chamber C toward the rod-side oil chamber B when the piston 5 is displaced downward along the inner tube 4 during a retraction stroke (a shock stroke) of the piston rod 10. This generates a predetermined damping force during the retraction stroke of the piston rod 10.

[0021] In other words, the piston retraction-side valve 7 generates the damping force by controlling the flow of hydraulic fluid (oil fluid) generated in accordance with a sliding movement of the piston 5 in the inner tube 4. The piston retraction-side valve 7 corresponds to a second valve that opens and closes the second oil passages 5B, which serve as a second passage. As shown in Fig. 16, which will be described later, the second oil passage 5B is provided with a piston retraction-side orifice plate 53, which functions as a throttle (orifice) when necessary. The piston retraction-side orifice plate 53, which corresponds to a third orifice plate, may be provided on the piston retraction-side valve 7 or on the seat side (the piston 5 side).

[0022] The upper end sides (opening end sides) of the outer tube 2 and the inner tube 4 are closed by the rod guide 8 and the rod seal 9. The rod guide 8 is a guide member that slidably guides axial displacement of the piston rod 10. The rod guide 8 is formed as a tubular member having a predetermined shape by molding, cutting, or the like on, for example, a metal material or a rigid resin material, and is fitted to the upper end sides (opening end sides) of the outer tube 2 and the inner tube 4.

[0023] The rod seal 9 is provided between the upper surface of the rod guide 8 and the crimped portions 2A of the outer tube 2. The rod seal 9 includes a metallic ring plate 9A as the core metal. An elastic sealing material such as rubber is integrally molded onto the ring plate 9A by a process such as baking. The rod seal 9 separates (seals) fluid-tightly or airtightly between the outer tube 2 and the piston rod 10 by means of sliding contact of the inner circumference of the rod seal 9 with the outer circumference side of the piston rod 10.

[0024] The lower end side of the piston rod 10, which corresponds to the proximal end side, is inserted into the inner tube 4, and the upper end side of the piston rod 10, which corresponds to the distal end side, protrudes from the inner tube 4 via the rod guide 8. In other words, the piston rod 10 is coupled to the piston 5 and protrudes from the inner tube 4. The piston 5, the piston retraction-side valve 7, and the piston extension-side valve 6 are fixed to the lower end side of the piston rod 10. Therefore, a small-diameter portion 10A, which is smaller in diameter than the other portions, is provided at the lower end side of the piston rod 10. Then, an externally threaded portion 10B is provided at the end portion of the small-diameter portion 10A.A nut 11 for fastening the piston 5, the piston retraction-side valve 7 and the piston extension-side valve 6 to the piston rod 10 is attached to the externally threaded portion 10B by thread engagement.

[0025] The valve body 12, which corresponds to a bottom body, is provided on the lower end side of the inner tube 4 at a position between the inner tube 4 and the bottom cap 3. The valve body 12 is provided on the body side (the tube side) of the shock absorber 1. The valve body 12 separates (defines) the storage chamber A and the bottom-side oil chamber C between the bottom cap 3 and the inner tube 4. For this reason, the valve body 12 is provided between the storage chamber A and the bottom-side oil chamber C. A plurality of oil passages 12A and a plurality of oil passages 12B are provided on the valve body 12. The oil passages 12A and 12B can establish communication between the storage chamber A and the bottom-side oil chamber C.

[0026] The oil passages 12A and 12B form passages that allow the flow of hydraulic fluid (oil fluid) directed from the bottom-side oil chamber C in the inner tube 4 and the reservoir chamber A in the outer tube 2 toward the other chamber in accordance with a movement of the piston 5. In other words, the third oil passages 12A as a third passage and the fourth oil passages 12B as a fourth passage establish communication between the bottom-side oil chamber C, which corresponds to the second chamber, and the reservoir chamber A, which corresponds to a third chamber, in accordance with a movement of the piston 5. The oil passages 12A and the oil passages 12B are flow passages in which a flow of hydraulic fluid (oil fluid) is generated in accordance with a movement of the piston 5.

[0027] A valve 13 is provided on the valve body 12. The valve 13 includes, for example, one or more discs (disc valves). Specifically, the valve 13 serving as an extension-side damping valve is provided on the top of the valve body 12. The extension-side valve 13 (hereinafter referred to as the extension-side valve 13) exerts a resistive force on the oil fluid flowing in the third oil passages 12A from the storage chamber A side toward the bottom-side oil chamber C when the piston 5 is displaced upward during the extension stroke of the piston rod 10.

[0028] The body extension-side valve 13 corresponds to a third valve that opens and closes the third oil passage 12A serving as the third passage. As shown in Fig. 16, which will be described below, the third oil passage 12A is provided with a body extension-side orifice 56 that functions as a throttle (orifice) when necessary. The body extension-side orifice 56, which corresponds to a fourth orifice, may be provided on the body extension-side valve 13 or on the seat side (the valve body 12 side).

[0029] The body extension-side valve 13, which corresponds to the third valve, may be configured, for example, as a suction valve, which primarily functions as a check valve (one-way valve) and generates almost no damping force. In other words, the body extension-side check valve 13 may be configured as a check valve that opens when the piston 5 is displaced upward during the extension stroke of the piston rod 10 and is closed otherwise. The body extension-side valve 13 configured as such a check valve allows the oil fluid in the storage chamber A to flow through the interior of the oil passages 12A toward the bottom-side oil chamber C and prevents the oil fluid from flowing in the opposite direction.

[0030] In addition to the extension-side valve 13, a valve 14 is provided on the valve body 12. The valve 14 includes, for example, one or more discs (disc valves). Specifically, the valve 14 serving as a retraction-side damping valve is provided on the lower surface side of the valve body 12. The retraction-side valve 14 (hereinafter referred to as the retraction-side valve 14) exerts a resistive force on the oil fluid flowing in the fourth oil passages 12B from the bottom-side oil chamber C toward the storage chamber A when the piston 5 is displaced downward during the retraction stroke of the piston rod 10.

[0031] The body retraction-side valve 14 corresponds to a fourth valve that opens and closes the fourth oil passage 12B serving as the fourth passage. As shown in Fig. 16, which will be described below, the fourth oil passage 12B is provided with a body-retraction-side orifice plate 57 that functions as a throttle (orifice) when necessary. The body-retraction-side orifice plate 57, which corresponds to a second orifice plate, may be provided on the body-retraction-side valve 14 or on the seat side (the valve body 12 side).

[0032] Then, the vehicle travels at any speed on a road surface under various conditions. Therefore, the vehicle body receives various influences from the road surface. It is desired to maintain ride comfort that provides a sense of stability to a passenger under such diverse driving conditions. A commonly used hydraulic shock absorber is adjusted toward the desired ride comfort by adjusting the damping force with respect to the piston speed on the retraction side and the extension side. Generally, the damping force is adjusted in this way based on the characteristics in a relatively wide amplitude and low frequency range.

[0033] However, the hydraulic damping force exhibits frequency dependence. Therefore, when the input frequency undergoes various changes, the hydraulic shock absorber may not be able to generate an appropriate damping force by only adjusting the magnitude of the damping force with respect to the piston speed on the retraction side and the extension side based on the characteristics in a relatively large amplitude and low-frequency band. For example, adjusting the damping force alone may result in a tight feeling, as in Fig. 18(A). Alternatively, adjusting the damping force alone can lead to the occurrence of rocking, as shown in Fig. 18(B). As a result, when the vehicle is actually running, excellent road surface response cannot be achieved, and the stability perceived by the passenger may be impaired.

[0034] As described above, the vehicle body is subject to various influences from the road surface during driving. Furthermore, the magnitude of the unevenness of the road surface, the interval between bumps, and the like vary. Therefore, it is important to generate not only a damping force suitable for the piston speed, but also a damping force suitable for the input frequency. In particular, it is desirable to reduce the frequency dependence of the damping force to achieve stable ride comfort under various driving conditions. However, it is difficult to reduce the frequency dependence because, for example, a delay in the damping force occurs due to the compressibility of the hydraulic oil.

[0035] On the other hand, even with the frequency dependence exhibited by both the extension-side damping force and the retraction-side damping force, maintaining the ratio between them with respect to the input frequency can prevent a significant change in the balance between upward and downward movements of the sprung side, even when the road surface conditions change. In other words, as shown in Fig. 17, a state in which the flatness is constantly maintained (an ideal state) can be achieved, and an uncomfortable feeling when driving the vehicle can be reduced. Under these circumstances, the embodiment aims to solve the above-described problem by reducing the frequency dependence of the ratio between the extension-side damping force and the retraction-side damping force (hereinafter referred to as the "extension / retraction ratio of the damping force").

[0036] The following description describes a reason for the frequency dependence of the extension / retraction ratio of the damping force (= the extension-side damping force / the retraction-side damping force) and a method for reducing it.

[0037] A hydraulic shock absorber that provides damping force using a common valve stack includes a high retraction-side oil chamber (a high retraction-side chamber) and a low retraction-side oil chamber (a low retraction-side chamber) filled with hydraulic oil. Then, the hydraulic shock absorber includes flow channels through which the hydraulic oil moves between these oil chambers, and adjusts the differential pressure based on the areas of these flow channels, thereby achieving a desired damping force. The flow channels through which the hydraulic oil moves are roughly divided into two types. One of them is an orifice plate, which establishes communication over a constant area at all times regardless of the differential pressure between the oil chambers. The other is a valve formed by a valve body formed of stacked disc valves.

[0038] The valve blocks the flow channel by remaining closed until the differential pressure generated between the oil chambers upstream and downstream of the flow channel reaches a set pressure. When the differential pressure reaches or exceeds the set pressure, the valve opens, establishing communication between the upstream oil chamber and the downstream oil chamber. Therefore, in a state where the hydraulic shock absorber operates at a low speed (piston speed), the differential pressure described above is also low, so the valve is closed and the hydraulic oil flows only through the orifice. The differential pressure increases according to a further increase in piston speed from this state, and the valve is opened when a force derived from this differential pressure exceeds a valve closing force applied to the valve in advance (a preset).Then, as the differential pressure increases, the valve stroke also increases and the area of ​​the flow channel is enlarged.

[0039] As used herein, a region where the differential pressure is generated due to the orifice when the valve is closed is defined as the "orifice region," and a region where the valve is open is defined as the "valve region." In this case, the frequency characteristic of the damping force is different between the orifice region and the valve region. In particular, as shown in Fig. 12, the flow area in the throttle orifice region is small and maintained at a constant value, so that an increase in differential pressure contributes less to achieving a flow rate and is therefore likely to be converted not only into an outflow / inflow but also into a volume deformation of the hydraulic oil, which is accompanied by a large response delay and a reduction in the damping force corresponding to an increase in frequency. On the other hand, as shown in Fig. As shown in Figure 13, the response delay in the valve area can be slightly reduced and the damping force hardly varies depending on the frequency.

[0040] The damping force characteristics of a damper (shock absorber) used in a motor vehicle are in most cases adjusted to different characteristics on the extension side and the retraction side. To achieve such characteristics, the extension-side and retraction-side valves must be adjusted to different valve opening pressures and different valve opening heights corresponding to the differential pressure according to the respective stiffnesses and presettings. Furthermore, the extension-side and retraction-side sides are adjusted to different orifice areas. This results in a difference being created between the valve opening characteristics of the extension-side and retraction-side valves, i.e.the times at which the valves are opened, thereby creating a state in which one of the extension and retraction sides is located in the throttle orifice area and the other in the valve area depending on the piston speed, thereby creating the frequency dependency of the extension / retraction ratio of the damping force due to the difference in frequency characteristics between the throttle orifice area and the valve area described above.

[0041] Fig. Figure 14, for example, shows an example of the relationship between piston speed and damping force when the valve on the extension side is subjected to a significantly higher valve opening pressure than the retraction side. In such a case, the extension side maintains the characteristics of the throttle orifice region up to a higher piston speed than the retraction side, and the extension-side damping force in this region decreases according to an increase in frequency. On the other hand, the retraction side transitions to the valve region at a lower piston speed than the extension side, and therefore the damping force decreases less with respect to frequency.

[0042] Due to such a difference in the characteristics, the frequency dependence in the extension / retraction ratio of the damping force results. Fig. 15 is an example of the relationship between the extension / retraction ratio of the damping force (the extension-side damping force / retraction-side damping force) and the frequency under a similar condition as in Fig. 14, ie when the valve on the extending side is subjected to a significantly higher valve opening pressure than the retracting side. In this case, a characteristic curve 101 in Fig. 15 a change in the extension / retraction ratio of the damping force with respect to the frequency at a “piston speed a” in Fig. 14. Similarly, a characteristic curve 102 in Fig. 15 a change in the extension / retraction ratio of the damping force with respect to the frequency at a “piston speed a” in Fig. 14, and a characteristic curve 103 in Fig. Figure 15 shows a change in the extension / retraction ratio of the damping force with respect to the frequency at a “piston speed c” in Fig. 14 on.

[0043] As in Fig. For example, as shown in Figure 15, the extension / contraction ratio of the damping force changes more with respect to frequency when the piston speed is "piston speed b" than when the piston speed is "piston speed a" or "piston speed b." In such a case, the sense of stability felt by the passenger is impaired as described above. Therefore, the frequency dependence of the extension / contraction ratio can be reduced by opening the respective valves of the extension side and the retraction side at close timings.

[0044] However, when attempting to reduce the speed corresponding to the valve opening timing on a high-damping side (the extension side in this example) so that the valves on the extension and retraction sides can be opened at close timings, a common method of stacking poppet valves requires reducing the stiffness of the valve on the high-damping side to lower the valve opening pressure, and this may result in a reduction in the damping force after the valve opens and insufficient damping force in a medium to high speed range that should otherwise be exerted, for example, to dampen spring resonance.

[0045] In view of this, according to the embodiment, a valve opening promotion mechanism (a sub-valve) is provided for the extension-side valve or the retraction-side valve, whichever is set to a higher valve opening pressure. The valve opening promotion mechanism serves to align this valve with the piston speed at which the valve set to a lower valve opening pressure is opened. Due to this valve opening promotion mechanism, the embodiment can reduce the reduction in valve opening pressure while simultaneously reducing the speed corresponding to the valve opening timing of the valve, compared to the conventional poppet valve stacking method.Accordingly, the embodiment can reduce the reduction in damping force while reducing frequency dependence of the extension / retraction ratio of the damping force due to the reduced speed corresponding to the valve opening timing of the valve and the alignment with the valve opening timing of the valve set to a lower valve opening pressure.

[0046] In other words, by providing the valve opening promotion mechanism (the sub-valve), the embodiment can shift the valve opening timing to the low-speed side while maintaining the valve opening pressure of the valve on the extension side or the retraction side, whichever is set to a higher valve opening pressure, thereby aligning the valve opening timing of the extension side and the retraction side, while ensuring flexible adjustment of the damping force (of the valve set to a higher valve opening pressure), thereby reducing the frequency dependency of the extension / retraction ratio of the damping force. Therefore, the shock absorber 1 can realize ride comfort that is more robust against changes in road surface conditions and provides a sufficient sense of stability to the passenger compared to the prior art.In the following description, an embodiment for implementation is described in detail.

[0047] First, for each structure of dampers (shock absorbers), a valve is defined, which is intended to provide the mechanism for promoting valve opening.

[0048] Fig. 16(A) shows a hydraulic pressure circuit of a monotube damper 51, which is a monotube shock absorber. As shown in Fig. As shown in Fig. 16(A), the monotube damper 51 generates the damping force using the two valves 6 and 7 provided on the piston 5. Specifically, the monotube damper 51 includes the piston inlet-side valve 7 (the piston inlet valve) and the piston outlet-side valve 6 (the piston outlet valve) provided on the piston 5. In this case, the piston outlet-side orifice plate 52 (the piston outlet orifice plate) and / or the piston inlet-side orifice plate 53 (the piston inlet orifice plate) are provided, as needed, between the rod-side oil chamber B corresponding to an upper piston chamber and the bottom-side oil chamber C corresponding to a lower piston chamber.In the case of the monotube damper 51 configured in this way, the mechanism for promoting the valve opening can be provided on one of the two valves 6 and 7 of the piston 5, which is set to a higher valve opening pressure (for example, the valve 6 on the piston extension side).

[0049] Fig. Figure 16(B) shows a hydraulic pressure circuit of a twin-tube damper 54, which is a double-tube shock absorber. The shock absorber 1 according to the embodiment corresponds to the twin-tube damper 54. As shown in Fig. 16(B), the twin-tube damper 54 includes the four valves 6, 7, 13, and 14 on the piston 5 side and the body 55 side. Specifically, the twin-tube damper 54 includes the piston inlet-side valve 7 (the piston inlet valve) that contributes to the inlet-side damping force, and the piston outlet-side valve 6 (the piston outlet valve) that contributes to the outlet-side damping force, on the piston 5 side. In this case, the piston outlet-side orifice plate 52 (the piston outlet orifice plate) and / or the piston inlet-side orifice plate 53 (the piston inlet orifice plate) is provided between the rod-side oil chamber B corresponding to the upper piston chamber and the bottom-side oil chamber C corresponding to the lower piston chamber.

[0050] Furthermore, the twin-tube damper 54 includes, on the body 55 (valve body 12) side, the extension-side valve 13 (the body extension valve) that contributes to the extension-side damping force, and the retraction-side valve 14 (the body retraction valve) that contributes to the retraction-side damping force. In this case, the extension-side orifice plate 56 (the body extension orifice plate) and / or the retraction-side orifice plate 57 (the body retraction orifice plate) are provided between the bottom-side oil chamber C, corresponding to the lower piston chamber, and the accumulator chamber A, as needed.

[0051] In this example, the attempt to reduce the frequency dependence of the damping force extension / retraction ratio can be achieved by aligning the valve opening timings (piston speeds) of all valves. However, this is not realistic because the stiffness (valve stiffness) varies greatly between these valves. Given this, an efficient reduction of the damping force extension / retraction ratio is attempted primarily by aligning the valve opening timings of the valves that contribute to generating the damping force. For this reason, valve 13, which is formed from a suction valve that primarily functions as a check valve and generates almost no damping force, is ignored because it contributes little to the damping force characteristic. The valve opening timings of the remaining three valves, 6, 7, and 14, are adjusted according to the following concept.

[0052] First, the frequency dependence of the damping force is due to a reduction in response in the throttle orifice region. Therefore, the frequency dependence becomes prominent in a valve set to a high valve opening pressure and maintains the throttle orifice region until a further high piston speed is reached. Accordingly, a valve set to the highest valve opening pressure among the three valves 6, 7, and 14 is provided with a valve opening promotion mechanism and is set to open at a timing close to that of a less rigid valve set to a lower valve opening pressure.Specifically, the valve opening pressures between the piston retraction-side valve 7 and the body retraction-side valve 14, which contribute to the retraction-side damping force, and the piston extension-side valve 6, which contributes to the extension-side damping force, are compared.

[0053] For example, when the extension-side damping force is greater than the retraction-side damping force, that is, the valve opening pressure of the piston extension-side valve 6 is the highest, the piston extension-side valve 6 is provided with the valve opening promotion mechanism. This brings the valve opening timing of the piston extension-side valve 6 closer to the valve opening timing of the piston retraction-side valve 7 or the retraction-side valve 14, which contributes to the retraction-side damping force, depending on which of them is set to a lower valve opening pressure (in principle, the piston retraction-side valve 7 is selected from the perspective of the pressure balance ratio). Then, when the retraction-side damping force is greater than the extension-side damping force, that is,When the valve opening pressure of the inlet-side valve 14 is highest, the inlet-side valve 14 is provided with a valve opening promotion mechanism. This allows the inlet-side valve 14 to be opened at a time closer to the valve opening time of the outlet-side valve 6.

[0054] Hereinafter, a mechanism for promoting the valve opening 21 according to the first embodiment will be described with additional reference to FIG. Fig. 2 to 4 and Fig. 1. In the first embodiment, the valve opening promotion mechanism 21 is provided on the piston extension-side valve 6.

[0055] The piston extension-side valve 6 includes a low-speed valve 22 and a second-stage valve 24 as the main valve. The mechanism for promoting the valve opening 21 is formed by the low-speed valve 22. The low-speed valve 22 includes a low-speed disc 22A corresponding to a low-speed opening valve and a small-diameter disc 22B corresponding to a small-diameter valve. The low-speed disc 22A contacts a seat portion 5C provided at the openings of the first oil passages 5A of the piston 5. The low-speed disc 22A is formed as an annular plate with an insertion hole formed on its inner side. The low-speed disc 22A constituting the low-speed valve 22 is seated on and separated from a seat pressure receiving surface 5C1 of the seat portion 5C. As shown in Fig. 4, the seat portion 5C is not annular, but formed into a seat shape with a different diameter. A recessed portion (a space) that can function as an orifice plate can be provided on the seat portion 5C by stamping (punching or pressing) as needed, although not shown in the figure.

[0056] The small-diameter disc 22B is arranged on the rear surface (lower surface side) of the low-speed disc 22A. The outer diameter dimension of the small-diameter disc 22B is smaller than the outer diameter dimension of the seat portion 5C of the piston 5. The outer diameter dimension of the small-diameter disc 22B is smaller than that of the low-speed disc 22A. The small-diameter disc 22B is also formed as an annular plate with an insertion hole formed on its inner surface. The second-stage valve 24 is arranged on the rear surface (lower surface) of the small-diameter disc 22B. The outer diameter dimension of the second-stage valve 24 is the same as the outer diameter dimension of the low-speed disc 22A of the low-speed valve 22.The second-stage valve 24 is formed by stacking three discs 24A, 24B, and 24C, each of which is formed as an annular plate. A retainer 25 and a washer 26 are arranged on the rear surface of the second-stage valve 24. Then, the low-speed valve 22 (the low-speed disc 22A and the small-diameter disc 22B), the second-stage valve 24 (the discs 24A, 24B, and 24C), the retainer 25, and the washer 26 are secured to the piston rod 10 with a nut 11.

[0057] In this way, in the first embodiment, the small-diameter disc 22B is disposed between the low-speed disc 22A and the second-stage valve 24. Thus, the small-diameter disc 22B defines a space 27 between the low-speed disc 22A and the second-stage valve 24. Therefore, the rigidity of the low-speed valve 22 (the low-speed disc 22A) at the beginning of valve opening can be reduced by means of this space 27. In other words, the space 27 can promote the valve opening of the low-speed valve 22 (the low-speed disc 22A) when the piston speed remains low.

[0058] As a result, the valve rigidity of the piston-extension-side valve 6 can be reduced because only the low-speed valve 22 (the low-speed disc 22A) functions as the valve body in the region at the beginning of valve opening where the piston speed is low. Furthermore, in the region between medium and high speed where the low-speed valve 22 (the low-speed disc 22A) is in contact with the second-stage valve, the low-speed valve 24 also functions as the valve body, so that the valve rigidity is increased. The present configuration is characterized by having a characteristic of such nonlinear valve rigidity. The rigidity of the low-speed valve 22 is determined mainly based on the plate thickness of the low-speed disc 22A and the outer diameter of the small-diameter disc 22B. Therefore, the two parameters (i.e.,Therefore, the plate thickness of the slow-speed disc 22A and the outer diameter of the small-diameter disc 22B) are adjusted so that the valve opening timing of the piston-extension-side valve 6 (ie, the valve opening timing of the slow-speed valve 22) corresponds to the desired timing.

[0059] The size of the space 27 between the low-speed valve 22 (the low-speed disc 22A) and the second-stage valve 24 controls the timing (piston speed) at which the low-speed valve 22 (the low-speed disc 22A) contacts the second-stage valve 24. This means that an area in which the low-speed valve 22 (the low-speed disc 22A) becomes effective is determined by the size of the space 27 (the gap between the low-speed disc 22A and the second-stage valve 24).

[0060] Therefore, the size of the space 27 affects the damping force in the medium to high speed range. Another factor that controls the damping force in the medium to high speed range is the rigidity of the second-stage valve 24. Therefore, the rigidity of the second-stage valve 24 is adjusted so that the desired damping force can be achieved. The second-stage valve 24 may be configured such that the initial displacement is set to the piston-extension-side valve 6. Furthermore, the outer diameter of the second-stage valve 24 may vary along the way. In other words, the outer diameters of the discs 24A, 24B, and 24C constituting the second-stage valve 24 may be different from each other.

[0061] In any case, in the first embodiment, the piston-extension-side valve 6 is provided with the low-speed valve 22 (the low-speed disc 22A and the small-diameter disc 22B) operable as a valve-opening promotion mechanism 21. The valve-opening promotion mechanism 21 reduces the frequency dependence of the extension / contraction ratio of the damping force by making the frequency characteristics of the damping force generated by the piston-extension-side valve 6 and the frequency characteristics of the damping force generated by the piston-retraction-side valve 7 match each other. The valve-opening promotion mechanism 21 (the low-speed valve 22) makes the frequency characteristics of the damping force of the piston-extension-side valve 6 match the frequency characteristics of the damping force of the piston-retraction-side valve 7.In this case, the slow-speed valve 22 (the slow-speed disc 22A) is opened at a lower piston speed than the piston speed at which the piston-retraction-side valve 7 is opened. This means that the piston-extension-side valve 6 is opened when the piston speed is lower than that of the piston-retraction-side valve 7. Preferably, the setting is made such that the piston-retraction-side valve 7 and the piston-extension-side valve 6 are set to the same timing.

[0062] Fig. 5 illustrates the relationship between the piston speed and the damping force of the shock absorber 1 according to the first embodiment, that is, the characteristic of the damping force with respect to the piston speed at a low frequency in the shock absorber 1 having the valve opening promotion mechanism 21 provided for the piston extension-side valve 6. Fig. Figure 6 illustrates the relationship between the extension / retraction ratio of the damping force and the frequency, that is, a change in the extension / retraction ratio of the damping force with respect to the frequency at each of the three different “piston speed a”, “piston speed b” and “piston speed c” in Fig. 5. In this case, a characteristic curve 31 in Fig. 6 the change in the extension / retraction ratio of the damping force with respect to the frequency at the “piston speed a” in Fig. 5. Similarly, a characteristic curve 32 in Fig. 6 the change in the extension / retraction ratio of the damping force with respect to the frequency at the “piston speed b” in Fig. 5, and a characteristic curve 33 in Fig. 15 shows the change of the extension / retraction ratio of the damping force with respect to the frequency at the “piston speed c” in Fig. 5. As can be seen from a comparison between Fig. 6 and the drawing described above, Fig. As can be clearly seen from Figure 15, the provision of the valve opening promotion mechanism 21 can significantly reduce the variation in the extension / contraction ratio of the damping force with respect to frequency. As a result, the shock absorber 1 can realize ride comfort that is highly robust against changes in road surface conditions and sufficient to provide the passenger with a sense of stability, compared to a configuration without the valve opening promotion mechanism 21 (the low-speed valve 22).

[0063] In this way, the shock absorber 1 according to the first embodiment comprises the inner tube 4, the piston 5, the first oil passages 5A as the first passage, the piston extension-side valve 6 as the first valve, the second oil passages 5B as the second passage, and the piston retraction-side valve 7 as the second valve. Furthermore, the shock absorber 1 comprises the outer tube 2 and the valve body 12. Furthermore, the shock absorber 1 comprises the piston extension-side orifice plate 52 (see Fig. 16) as the first throttle orifice provided for the first oil passage 5A of the piston 5, the third oil passages 12A as the third passage, the body extension-side valve 13 as the third valve, the fourth oil passages 12B as the fourth passage, the piston retraction-side valve 14, and the piston retraction-side throttle orifice 57 (see Fig. 16) as a second throttle orifice provided for the fourth oil passage 12B of the valve body 12.

[0064] In addition, the shock absorber 1 is configured such that the frequency characteristic of the piston extension-side valve 6 or the piston retraction-side valve 7 (or the body retraction-side valve 14), whichever corresponds to a damping force with higher frequency dependence (for example, the piston extension-side valve 6), matches the frequency characteristic of the other, which corresponds to a damping force with lower frequency dependence (for example, the piston retraction-side valve 7).To achieve this, the piston-extending-side valve 6 or the piston-retracting-side valve 7, depending on which is set to a higher valve opening pressure (for example, the piston-extending-side valve 6), is provided with the valve opening promotion mechanism 21, which aligns the valve opening timing thereof with the valve opening timing of the other valve, which is set to a lower valve opening pressure (for example, the piston-retracting-side valve 7).Alternatively, the piston extension-side valve 6 or the body retraction-side valve 14, whichever is set to a higher valve opening pressure (for example, the piston extension-side valve 6), is provided with the valve opening promotion mechanism 21 that aligns its valve opening timing with the valve opening timing of the other valve that is set to a lower valve opening pressure (for example, the piston retraction-side valve 7).

[0065] In this case, the piston extension-side valve 6 or the piston retraction-side valve 7, whichever is set to a higher valve opening pressure (for example, the piston extension-side valve 6), is opened when the piston speed is lower compared to the other valve set to a lower valve opening pressure (for example, the piston retraction-side valve 7). Alternatively, the piston extension-side valve 6 or the body retraction-side valve 14, whichever is set to a higher valve opening pressure (for example, the piston extension-side valve 6), is opened when the piston speed is lower than that of the other valve set to a lower valve opening pressure (for example, the retraction-side valve 14).In other words, the valve opening promotion mechanism 21 opens the valve set to a higher valve opening pressure (for example, the piston extension-side valve 6) when the piston speed is lower compared to the valve set to a lower valve opening pressure (for example, the piston retraction-side valve 7 and / or the body retraction-side valve 14).

[0066] The mechanism for promoting valve opening 21 is constituted, for example, by the slow-action valve 22 (slow-action disc 22A and small-diameter disc 22B). In other words, the piston-extension-side valve 6 or the piston-retraction-side valve 7, whichever is set to a higher valve opening pressure (for example, the piston-extension-side valve 6), is provided with the slow-action valve 22, which has a weaker biasing force (a deformation resistance force, a counter-deformation force, a valve closing force, or a valve-holding force) compared to the other valve set to a lower valve opening pressure (for example, the piston-retraction-side valve 7 and / or the body-retraction-side valve 14). For example, when the piston extension side valve 6 is provided with the slow speed valve 22, the slow speed valve 22 opens the first oil passages 5A when the piston speed is low.For example, if the piston retraction-side valve 7 is equipped with the low-speed valve 22, the low-speed valve 22 opens the second oil passages 5B when the piston speed is low. As shown in FIGS. Fig. 2 and Fig. 3, the space 27 is defined between the slow speed valve 22 and the valve stacked on this slow speed valve 22 (ie, the second stage valve 24).

[0067] The shock absorber 1 according to the first embodiment is configured as described above, and its operation will be described below.

[0068] The shock absorber 1 is mounted such that, for example, the distal end side (upper end side) of the piston rod 10 is fixed to the body side of the vehicle (the motor vehicle), and the lower cap side 3, located at the proximal end side (lower end side) of the outer tube 2, is fixed to the wheel side (axle side) of the vehicle. Therefore, when vibration occurs while the vehicle is traveling, the shock absorber 1 dampens the vibration at that time by generating the damping force through, for example, the valves 6 and 7 of the piston 5 while extending / contracting the piston rod 10.

[0069] Specifically, when the piston rod 10 is in the retraction stroke, the inside of the bottom-side oil chamber C is placed in a higher pressure state than the rod-side oil chamber B. Then, the oil fluid (the hydraulic oil) in the bottom-side oil chamber C flows into the rod-side oil chamber B via the second oil passages 5B of the piston 5 and the piston-retraction-side valve 7, thereby generating the damping force. At this time, the oil fluid from the bottom-side oil chamber C flows into the storage chamber A via the fourth oil passages 12B of the valve piston 12 and the piston-retraction-side valve 14 in an amount corresponding to the volume of entry of the piston rod 10 into the inner tube 4. The gas trapped inside is compressed in the storage chamber A, and the amount corresponding to the volume of entry of the piston rod 10 is absorbed.

[0070] On the other hand, when the piston rod 10 is in the extension stroke, the inside of the rod-side oil chamber B is placed in a higher pressure state than the bottom-side oil chamber C. Then, the oil fluid (the hydraulic oil) in the rod-side oil chamber B flows into the bottom-side oil chamber C via the first oil passages 5A of the piston 5 and the piston extension-side valve 6, thereby generating the damping force. At this time, the oil fluid from the inside of the reservoir chamber A flows into the bottom-side oil chamber C via the third oil passages 12A of the valve bottom 12 and the body extension-side valve 13 (the check valve) in an amount corresponding to the discharge volume (the retraction volume) of the piston rod 10 discharging (retracting) from the inner tube 4.

[0071] According to the first embodiment, the piston-extension-side valve 6, which is the piston-extension-side valve 6 or the piston-retraction-side valve 7, which is the second-stage valve 24, which is the valve set to a higher valve opening pressure, is provided with the valve-opening-promoting mechanism 21 that synchronizes its valve opening timing with the valve opening timing of the piston-retraction-side valve 7, which is the other valve set to a lower valve opening pressure. This makes it possible, for example, to increase rigidity when the piston speed is further increased by the second-stage valve 24, while the low-speed valve 22 of the piston-extension-side valve 6 can be opened at a lower piston speed (compared to a prior art configuration without the valve-opening-promoting mechanism 21).As a result, the shock absorber 1 can ensure the damping force in the medium-to-high speed range on the extension side while reducing the frequency dependence of the extension / contraction ratio of the damping force. As a result, compared with the prior art technology (the configuration without the valve opening promotion mechanism 21), the shock absorber 1 can realize ride comfort that is more robust against changes in road conditions and sufficient to provide the passenger with a sense of stability. In summary, the shock absorber 1 can achieve such a damping force characteristic that the sprung side of the vehicle is stabilized regardless of the road surface, thereby allowing the passenger to continue riding the vehicle without feeling uncomfortable.

[0072] According to the first embodiment, the piston extension-side valve 6 is configured such that the frequency dependency of the damping force matches the piston retraction-side valve 7. In other words, the piston extension-side valve 6, which is the valve corresponding to a damping force with a higher frequency dependency, is configured to match the piston retraction-side valve 7, which is the valve corresponding to a damping force with a lower frequency dependency. This allows the shock absorber 1 to reduce the frequency dependency of the extension / retraction ratio of the damping force. As a result, the shock absorber 1 can realize ride comfort that is even more robust against changes in road surface conditions and sufficient to provide the passenger with a sense of stability.In summary, the shock absorber 1 can achieve such a damping force characteristic that the sprung side of the vehicle is stabilized regardless of the road surface, allowing the passenger to continue riding the vehicle without feeling uncomfortable.

[0073] According to the first embodiment, the piston extension-side valve 6, which is set to a higher valve opening pressure, is opened when the piston speed is lower than the piston retraction-side valve 7, which is set to a lower valve opening pressure. This allows the shock absorber 1 to achieve a high differential pressure by increasing the valve stiffness in the mid-to-high range while allowing the piston extension-side valve 6 to be opened at a low piston speed, thereby succeeding in reducing the frequency dependence of the extension / contraction ratio of the damping force by opening the piston extension-side valve 6 at a low piston speed while preventing a decrease in the damping force of the piston extension-side valve 6.

[0074] According to the first embodiment, the piston extension-side valve 6 is provided with the low-speed valve 22, which is subjected to a weaker preload force than the piston retraction-side valve 7 and opens the first oil passages 5A at low piston speeds. Therefore, the shock absorber 1 allows the valve opening initial characteristic of the piston extension-side valve 6 and its mid-to-high stiffness to be adjusted independently of each other, thereby ensuring the flexibility of adjusting the extension-side damping force while reducing the frequency dependence of the extension / retraction ratio of the damping force.

[0075] According to the first embodiment, the space 27 is defined between the low-speed valve 22 (the low-speed disc 22A) and the second-stage valve 24. This allows the low-speed valve 22 (the low-speed disc 22A) to be easily displaced (deformed) toward the space 27 side. This allows the low-speed valve 22 to be opened when the piston speed is low.

[0076] According to the first embodiment, the piston extension-side valve 6, which is the piston extension-side valve 6 or the retraction-side valve 14 set to a higher valve opening pressure, is provided with a valve opening promotion mechanism 21 that aligns its valve opening timing with the valve opening timing of the piston retraction-side valve 7, which is the other of the two valves set to a lower valve opening pressure. This makes it possible to increase the rigidity in the medium-to-high speed range while allowing the piston extension-side valve 6 to be opened at a low piston speed. As a result, the shock absorber 1 can ensure the damping force in the medium-to-high speed range on the extension side while reducing the frequency dependence of the extension / contraction ratio of the damping force.As a result, compared to the prior art (the configuration without the valve opening promotion mechanism 21), the shock absorber 1 can realize ride comfort that is more robust against changes in road conditions and sufficient to provide the passenger with a sense of stability. In summary, the shock absorber 1 can achieve damping force characteristics such that the sprung side of the vehicle is stabilized regardless of the road surface, allowing the passenger to continue riding the vehicle without discomfort.

[0077] The low-speed valve 22 according to the first embodiment defines the space 27 between the low-speed disc 22A and the second-stage valve 24, the size of which is determined based on the plate thickness of the small-diameter disc 22B. Reducing the space 27 between the small-diameter disc 22B and the second-stage valve 24 allows the piston-extension-side valve 6 to transition to a region where the valve rigidity is high at an earlier time (piston speed), resulting in the generation of a large damping force. However, the plate thickness of the small-diameter disc 22B is difficult to reduce by a predetermined thickness or more from the viewpoint of mass producibility and strength, and may limit the flexibility in generating the damping force.

[0078] In view of this, in a Fig. In the modification shown in Fig. 7, a clearance adjusting disc 42 is provided on a low-speed valve 41 between the small-diameter disc 22B and the second-stage valve 24. The clearance adjusting disc 42 serves to change the size of the clearance 27 between the radially inner side and the radially outer side. Then, the size of the clearance 27 is widened on the radially inner portion side and narrowed on the radially outer portion side by means of the clearance adjusting disc 42. In other words, in the modification, the low-speed valve 41 includes the clearance adjusting disc 42 as a fifth valve (a clearance adjusting valve) and the small-diameter disc 22B. The clearance adjusting disc 42 includes a protruding portion 42A that protrudes toward the low-speed disc 22A of the piston-extension-side valve 6 and is axially wider than the other portions.The small-diameter disc 22B is provided between the low-speed disc 22A of the piston-extension-side valve 6 and the clearance adjusting disc 42. The small-diameter disc 22B has a smaller diameter than the low-speed disc 22A and the clearance adjusting disc 42.

[0079] Thus, in the modification, the clearance adjustment disc 42, whose thickness varies on the radially outer side, is provided between the small-diameter disc 22B and the second-stage valve 24. This makes it possible to adjust the clearance 27 to a small size between the low-speed disc 22A and the second-stage valve 24 even if the plate thickness of the small-diameter disc 22B is thickened. As a result, the modification can improve the flexibility of damping force generation, while adjusting the plate thickness of the small-diameter disc 22B to a thickness sufficient to ensure mass producibility and strength.

[0080] In summary, the low-speed valve 41 according to the modification includes the clearance adjustment disc 42 in addition to the low-speed disc 22A and the small-diameter disc 22B. The clearance adjustment disc 42 includes the protrusion portion 42A projecting toward the low-speed disc 22A. This makes it possible to reduce the space 27 between the low-speed disc 22A of the piston-side valve 6 and the clearance adjustment disc 42 (the protrusion portion 42A) while increasing the plate thickness of the small-diameter portion 22B. As a result, the modification can both "ensure the mass producibility and strength of the small-diameter disc 22B" and, at the same time, "ensure the flexibility of adjusting the damping force of the piston-side valve 6."

[0081] The modification has been described with reference to the example in which the clearance adjusting washer 42 is configured to have the protrusion portion 42A. However, without being limited thereto, the clearance adjusting washer may, for example, have a different plate thickness between the radially inner portion and the radially outer portion. In other words, the clearance adjusting washer may be formed such that the plate thickness of the radially outer portion is thicker than the plate thickness of the radially inner portion. Further, the protrusion portion may be integrally formed with the washer by pressing, or it may be integrally formed with the washer by melting, and a member other than the washer may be fixed to a portion corresponding to the protrusion portion by welding.

[0082] Next, the Fig. 8 to 11 show a second embodiment. The second embodiment is characterized in that it is configured to include a first seat portion on which the low-speed valve is seated and separated, and a second seat portion on which the main valve (the second-stage valve) is seated and separated. The second embodiment will be described, indicating similar components to the above-described first embodiment by the same reference numerals, and omitting redundant descriptions thereof.

[0083] In the second embodiment, the piston-extension-side valve 6 includes a low-speed valve 61 and a second-stage valve 62 as the main valve. The mechanism for promoting the valve opening 21 is formed by the low-speed valve 61. In other words, the piston-extension-side valve 6 includes the low-speed valve 61, which is set to a low valve stiffness and opens at a low speed to contribute to the damping force in the low-speed range, and the second-stage valve 62, which is set to a higher stiffness than the low-speed valve 61 and contributes to the damping force in the medium-to-high-speed range. The low-speed valve 61 and the second-stage valve 62 are arranged in series in the hydraulic pressure circuit.

[0084] The low-speed valve 61 includes two low-speed discs 61A and 61B and a retainer 61C. The second-stage valve 62 includes four discs 62A, 62B, 62C, and 62D. The retainer 61C is provided between the low-speed disc 61B, which is located on the rear side (the lower surface side), and the disc 62A of the second-stage valve 62. In the second embodiment, the low-speed valve 61 and the second-stage valve 62 are seated on and separated from different seat portions 63 and 64, respectively. In particular, the piston 5 includes the inner seat portion 63 as a first seat portion on which the slow speed valve 61 is mounted and from which it is separated, and the outer seat portion 64 as a second seat portion located on the radially outer side of the inner seat portion 63 and on which the second stage valve 62 is mounted and from which it is separated.The inner seat portion 63, which the low-speed valve 61 contacts, is located on the radially inner side of the outer seat portion 64, which the second-stage valve 62 contacts. Both the inner seat portion 63 and the outer seat portion 64 have annular seat shapes.

[0085] The low-speed valve 61 is provided so that the piston-extension-side valve 6 can be opened from a wider low-speed range. Therefore, it is desirable that the height between a "seat surface 63A of the inner seat portion 63, onto which the low-speed valve 61 is seated and separated" and a "support surface 65A of a support member 65 with which the radially inner side of the low-speed valve 61 contacts" be as short as a manufacturing tolerance. Furthermore, the support surface 65A that contacts the radially inner side of the low-speed valve 61 is also used as a portion that supports the radially inner side of the second-stage valve 62.In other words, 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 of this low-speed valve 61. This defines a step H, which is the height difference, between the support surface 65A and a seat surface 64A of the outer seat portion 64.

[0086] Furthermore, a presetting (a preload or a preset force) may be applied to the second-stage valve 62. 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 a size equal to or larger than the thickness of the low-speed valve 61 (the two low-speed discs 61A and 61B and the holder 61C). In the low-speed disc 61 formed by the two low-speed discs 61A and 61B, the low-speed disc 61A contacting the inner seat portion 63 is formed as a slit disc with a pair of cutouts 61A1 on its outer peripheral edge. The cutouts 61A1 correspond to the first orifice (the piston extension-side orifice). The low-speed valve 61 contributes to the characteristics in the low-speed range.

[0087] The slit disc (the low-speed disc 61A) may be omitted depending on the vehicle specifications. Furthermore, for example, a disc having a diameter equal to that of the low-speed valve 61 (the low-speed valves 61A and 61B) or a valve having a different plate thickness between the radially inner portion and the radially outer portion (for example, the clearance adjustment valve 42 in Fig. 7) may be arranged on the back side (the lower surface) of the holder 61C to restrict the lift amount of the low-speed valve 61 (the low-speed discs 61A and 61B), although the illustration thereof is omitted.

[0088] Since the damping force in the low-speed range of the piston-extension-side valve 6 is increased, it is beneficial to increase the contribution of the damping force generated by the low-speed valve 61. To achieve this, the disc 62A contacting the outer seat portion 64 among the four discs 62A, 62B, 62C, and 62D constituting the second-stage valve 62 is configured as a slit disc with a pair of cutouts 62A1 provided on the outer peripheral edge thereof. In this case, the contribution of the second-stage valve 62 to the generation of the damping force in the low-speed range is reduced by ensuring a sufficient orifice area by means of the disc 62A (the slit disc).

[0089] The second-stage valve 62 plays a role in generating the damping force in the medium-to-high speed range of the piston-extension-side valve 6. Therefore, the rigidity of the second-stage valve 62 is adjusted based on parameters such as the number of stacked discs 62A, 62B, 62C, and 62D, the plate thickness, and the radial dimension of the retainer 25 on the rear side. Further, or alternatively, the second-stage valve 62 can be adjusted to be capable of achieving a desired characteristic by providing the second-stage valve 62 with a certain step to apply preload. The inner seat portion 63, on which the low-speed valve 61 is seated and from which it is separated, is not limited to the annular seat shape and may have a seat shape with a different diameter depending on a characteristic to be achieved in the low-speed range.

[0090] The second embodiment includes the low-speed valve 61 and the second-stage valve 62 described above, and its basic operation is not significantly different from the operation of the first embodiment described above. In other words, the second embodiment can also achieve a damping force characteristic such that the sprung side of the vehicle is stabilized regardless of the road surface, similar to the first embodiment. Fig. 10 illustrates the curve of the damping force as a function of the piston speed according to the second embodiment. Fig. Figure 11 illustrates the changes in the extension / retraction ratio of the damping force as a function of frequency for the three different Fig. 10 shown piston speeds (piston speed a, piston speed b, piston speed c and piston speed c). As can be seen from a comparison between Fig. 11 and the drawing described above, Fig. As can be clearly seen from Figure 15, the provision of the valve opening promotion mechanism 21 can significantly reduce the variation in the extension / contraction ratio of the damping force with respect to frequency. As a result, the shock absorber 1 can realize ride comfort that is further robust against changes in road surface conditions and sufficient to provide the passenger with a sense of stability, compared to the configuration without the valve opening promotion mechanism 21 (the low-speed valve 61).

[0091] The valve opening point of the valve cannot be precisely determined from the “damping force-piston speed line diagram” as shown in the examples in the drawings described above, Fig. 5 and Fig.10. In other words, although the point on the polygonal line of the extension-side damping force and the point on the polygonal line of the retraction-side damping force appear to be aligned on the "damping force-piston speed line diagram," the valve opening timings of the valves are not necessarily aligned. For example, the valve opening promotion mechanism according to the first embodiment has the characteristic that the valve stiffness is nonlinearly set to be low only in the low-speed range and high in the medium-to-high-speed range, and therefore, no clear valve opening point of the valve appears on the damping force-piston speed line diagram.Furthermore, in the case of such a configuration where 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, which is set to a higher valve opening pressure, appears on the line graph, 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 of the valve on the "damping force-piston speed line graph," and the valve opening point of the valve should be determined by a calculation based on the orifice, the pressure-receiving area of ​​the valve, and the valve stiffness, or by measuring the frequency characteristics at each piston speed to determine the valve opening point of the valve.In other words, the valve opening timing of the valve (the piston speed) is determined based on the differential pressure between the flows upstream and downstream of the valve, the valve stiffness, the set load, the pressure-absorbing area and the shape of the valve seat and should therefore be determined by calculation rather than being evident from the "damping force-piston speed diagram".

[0092] In the description of the first embodiment, it is assumed that the piston-extension-side valve 6 is the first valve and the piston-retraction-side valve 7 is the second valve. However, without being limited to this, for example, the piston-extension-side valve and the piston-retraction-side valve may be the second valve and the first valve, respectively. The same applies to the second embodiment and the modification.

[0093] In the description of the first embodiment, it was assumed that the body extension-side valve 13 is the third valve and the housing retraction-side valve 14 is the fourth valve. Without being limited to this, the housing extension-side valve and the housing retraction-side valve may be the fourth valve and the third valve, respectively. The same applies to the second embodiment and the modification.

[0094] The first embodiment was described using the example in which the shock absorber 1 is configured such that the piston extension-side valve 6 on the lower side of the piston 5 generates the damping force by applying the resisting force to the oil fluid (the hydraulic fluid) during the extension stroke of the piston rod 10, and the piston retraction-side valve 7 on the upper side of the piston 5 generates the damping force by applying the resisting force to the oil fluid (the hydraulic fluid) during the retraction stroke of the piston rod 10. However, without being limited to this, the shock absorber 1 may also be configured such that, for example, a check valve is used as the piston extension-side valve on the upper side of the piston, and the damping force is generated by the piston retraction-side valve provided as a fourth valve on the valve body during the retraction stroke of the piston rod.The same applies to the second embodiment and the modification.

[0095] The first embodiment has been described with reference to the example in which the shock absorber 1 is configured such that the piston extension-side valve 6, which is one of the piston extension-side valve 6 and the body retraction-side valve 14 set to a higher valve opening pressure, is provided with the valve opening promotion mechanism 21 that aligns its valve opening timing with the valve opening timing of the piston retraction-side valve 7, which is the other valve set to a lower valve opening pressure.However, without being limited to this, for example, in a case where the body retraction-side valve is the one of the piston extension-side valve and the body retraction-side valve that is set to a higher valve opening pressure, the body retraction-side valve may be provided with the valve opening promotion mechanism that aligns its valve opening timing with the valve opening timing of the piston extension-side valve, which is the other one that is set to a lower valve opening pressure. The same applies to the second embodiment and the modification.

[0096] The first embodiment was described using the example of the double-tube shock absorber 1 with the outer tube 2 and the inner tube 4. However, without being limited to this, the present invention can also be applied, for example, to a shock absorber formed from a single tubular member (cylinder). In this case, the valve opening promotion mechanism can be provided on the first valve or on the second valve attached to the piston, whichever is set for higher rigidity. The same applies to the second embodiment and the modification.

[0097] Each of the embodiments and the modification has been described with reference to the shock absorber mounted on a motor vehicle as a representative example of shock absorbers. However, the present invention can be applied, for example, to a shock absorber mounted on a railway train, without being limited thereto. Alternatively, the present invention can be applied to various types of shock absorbers used, for example, for various machines, structures, and buildings that become sources of vibration, without being limited to vehicles such as a motor vehicle and a railway train.

[0098] In addition, each of the embodiments and the modification is only an example, and it is understood that the configurations specified in the various embodiments and modifications may be partially replaced or combined.

[0099] According to the above-described embodiments and / or modifications (hereinafter simply referred to as "embodiments"), the first valve or the second valve, depending on which is set to a higher valve opening pressure, is provided with a valve opening promotion mechanism that aligns the valve opening timing of that valve with the valve opening timing of the other valve set to a lower valve opening pressure. This makes it possible to increase rigidity in the medium-to-high speed range, while allowing the valve set to a higher valve opening pressure to be opened at a further low piston speed. This allows the shock absorber to secure the damping force of the valve set at a higher valve opening pressure in the medium-to-high speed range while reducing the frequency dependence of the extension / contraction ratio of the damping force.As a result, compared to the configuration without the valve-opening promotion mechanism, the shock absorber can achieve ride comfort that is more robust against changes in road surface conditions and sufficient to provide the passenger with a sense of stability. In summary, the shock absorber can achieve damping force characteristics that stabilize the sprung side of the vehicle regardless of the road surface, allowing the passenger to continue driving the vehicle without discomfort.

[0100] According to the embodiments, the shock absorber is configured such that the frequency characteristic of the first valve or the second valve, whichever corresponds to a damping force with a higher frequency dependency, matches the frequency characteristic of the valve corresponding to a damping force with a lower frequency dependency. This allows the shock absorber 1 to reduce the frequency dependency of the extension / contraction ratio of the damping force. As a result, the shock absorber can realize ride comfort that is more robust against changes in road conditions and sufficient to provide the passenger with a sense of stability. In summary, the shock absorber can achieve such a damping force characteristic that the sprung side of the vehicle is stabilized regardless of the road surface, allowing the passenger to continue riding in the vehicle without feeling uncomfortable.

[0101] According to the embodiments, the first valve or the second valve, depending on which is set to a higher valve opening pressure, is opened at a lower piston speed compared to the valve set to a lower valve opening pressure. This makes it possible to increase rigidity in the medium to high speed range, while the valve set to a higher valve opening pressure can be opened at a further low piston speed. This allows the shock absorber to ensure the damping force of the valve set to a higher valve opening pressure in the medium to high speed range while reducing the frequency dependence of the extension / contraction ratio of the damping force.

[0102] According to the embodiments, the first valve or the second valve, depending on which is set to a higher valve opening pressure, is provided with the low-speed valve, which is subjected to a weaker preload force compared to the valve set to a lower valve opening pressure and opens the first channel or the second channel at a low piston speed. This makes it possible to increase the rigidity in the medium-to-high speed range, while the valve set to a higher valve opening pressure can be opened at a further low piston speed. This allows the shock absorber to reduce the frequency dependence of the extension / contraction ratio of the damping force while ensuring the flexibility of the damping force of the valve set to a higher valve opening pressure in the medium-to-high speed range.

[0103] According to the embodiments, the space is defined between the "low-speed valve" and the "valve stacked on the low-speed valve." This allows the low-speed valve to be easily displaced (deformed) toward the space side. This allows the low-speed valve to be opened when the piston speed is low.

[0104] According to the embodiments, the low-speed valve includes the fifth valve, whose protruding portion protrudes toward the second valve and is axially wider than the other portions, and the small-diameter disc between the second valve and the fifth valve. This makes it possible to reduce the space between the second valve and the fifth valve (the protruding portion) while simultaneously increasing the plate thickness of the small-diameter disc. This allows the shock absorber to both "ensure the mass producibility and strength of the small-diameter disc" and "ensure the flexibility of damping force adjustment."

[0105] According to the embodiments, the first valve or the fourth valve, depending on which is set to a higher valve opening pressure, is provided with a valve opening promotion mechanism that aligns its valve opening timing with the valve opening timing of the valve set to a lower valve opening pressure. This makes it possible to increase rigidity in the medium-to-high speed range, while allowing the valve set to open with a higher valve opening pressure at a further low piston speed. This allows the shock absorber to ensure the damping force of the valve set with a higher valve opening pressure in the medium-to-high speed range while reducing the frequency dependence of the extension / contraction ratio of the damping force.As a result, compared to the configuration without the valve opening promotion mechanism, the shock absorber can achieve ride comfort that is more robust against changes in road surface conditions and sufficient to provide the passenger with a sense of stability. In summary, the shock absorber can achieve damping force characteristics that stabilize the sprung side of the vehicle regardless of the road surface, allowing the passenger to continue driving the vehicle without discomfort.

[0106] This application claims priority under the Paris Convention to 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 in its entirety by reference into this application. LIST OF REFERENCE SYMBOLS 1 shock absorber 2 outer tube 4 inner tube 5 pistons 5A first oil channel (first channel) 5B second oil channel (second channel) 6 piston extension side valve (first valve) 7 piston retraction side valve (second valve) 12 valve bodies 12A third oil channel (third channel) 12B fourth oil channel (fourth channel) 13 body extension side valve (third valve) 14 body retraction valve (fourth valve) 21 Mechanism for promoting valve opening 22, 41, 61 Slow-speed valve 22B small diameter disc 42 Distance adjusting disc (fifth valve) 42A projection section 52 piston extension side throttle orifice (first throttle orifice) 57 Piston entry-side throttle orifice (second throttle orifice) A storage chamber B rod-side oil chamber (first chamber) C bottom oil chamber (second chamber) QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2020-34068

[0003] JP 2022-156052

[0106]

Claims

[1] Shock absorber, comprising: an inner tube in which a hydraulic fluid is enclosed; a piston slidably disposed in the inner tube and dividing the interior of the inner tube into a first chamber and a second chamber; a first channel provided on the piston; a first valve configured to open and close the first channel; a second channel provided on the piston; and a second valve configured to open and close the second channel, wherein the first valve or the second valve, depending on which is set to a higher valve opening pressure, is provided with a valve opening promotion mechanism configured to align a valve opening timing of that valve with a valve opening timing of the other valve, which is set to a lower valve opening pressure. [2] Shock absorber, comprising: an inner tube in which a hydraulic fluid is enclosed; a piston slidably disposed in the inner tube and dividing the interior of the inner tube into a first chamber and a second chamber; a first channel provided on the piston; a first valve configured to open and close the first channel; a second channel provided on the piston; and a second valve configured to open and close the second channel, wherein the shock absorber is configured to cause a frequency characteristic of the first valve or the second valve, whichever corresponds to a damping force with a higher frequency dependency, to match a frequency characteristic of the other valve corresponding to a damping force with a lower frequency dependency. [3] A shock absorber according to claim 1, wherein the first valve or the second valve, whichever is set to the higher valve opening pressure, is opened when the piston speed is lower compared to the other valve which is set to the lower valve opening pressure. [4] Shock absorber, comprising: an inner tube in which a hydraulic fluid is enclosed; a piston slidably disposed in the inner tube and dividing the interior of the inner tube into a first chamber and a second chamber; a first channel provided on the piston; a first valve configured to open and close the first channel; a second channel provided on the piston; and a second valve configured to open and close the second channel; wherein the first valve or the second valve, whichever is set to a higher valve opening pressure, is provided with a slow-action valve which is subjected to a weaker biasing force compared to the other valve which is set to a lower valve opening pressure, and is configured to open the first channel or the second channel when a piston speed is low. [5] A shock absorber according to claim 4, wherein a space is defined between the low-speed valve and a valve stacked on the low-speed valve. [6] The shock absorber according to claim 4, wherein the low-speed valve comprises a fifth valve having a protruding portion protruding toward the second valve and being axially wider than other portions, and a small-diameter disc disposed between the second valve and the fifth valve and having a smaller diameter than the second valve and the fifth valve. [7] Shock absorber, comprising: an inner tube in which a hydraulic fluid is enclosed; a piston slidably provided in the inner tube and dividing the interior of the inner tube into a first chamber and a second chamber; an outer tube provided outside the inner tube and forming a storage chamber between the outer tube and the inner tube; a valve body provided between the storage chamber and the second chamber; a first channel provided on the piston; a first valve configured to open and close the first channel; a first orifice plate provided on the first passage; a second channel provided on the piston; a second valve configured to open and close the second channel; a third channel provided on the valve body; a third valve configured to open and close the third channel; a fourth channel provided on the valve body; a fourth valve configured to open and close the fourth channel; and a second throttle orifice provided on the fourth channel, wherein the first valve or the fourth valve, depending on which is set to a higher valve opening pressure, is provided with a valve opening promotion mechanism configured to align a valve opening timing of that valve with a valve opening timing of the other valve, which is set to a lower valve opening pressure.

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