shock absorbers

Abstract

Shock absorbers, comprehensive: a cylinder (2) in which hydraulic fluid is contained in a closed manner; a piston (3) which is slidably fitted into the cylinder (2); a piston rod (4) having a first end coupled to the piston (3) and a second end extending outside the cylinder; a main valve (21) designed to generate a damping force by controlling a hydraulic fluid flow from an upstream chamber (2A) to a downstream chamber (2B) which is generated when the piston (3) moves in a first direction; a back pressure chamber (43) which is installed in the downstream chamber (2B) and exerts back pressure which acts on the main valve (21) in a valve closing direction; a sealing mechanism (38) which moves with a movement of an outer peripheral section of the main disk when the main valve (21) is open and defines the back pressure chamber (43); and a backpressure introduction path for introducing the hydraulic fluid from the upstream chamber into the backpressure chamber (43), wherein the opening of the main valve is controlled by means of the back pressure of the back pressure chamber (43), and characterized by the fact that the sealing mechanism (38) is designed to function as a valve that directs the hydraulic fluid in the chamber, which becomes a downstream chamber (2B) when the piston (3) moves in the first direction, into the counter-pressure chamber (43) when the piston (3) moves in a second direction.

Description

AREA OF INVENTION

[0001] The invention relates to a shock absorber that controls a hydraulic fluid flow produced by strokes of a piston rod and consequently generates a damping force. GENERAL STATE OF THE ART

[0002] Patent literature 1 discloses a hydraulic shock absorber in which, during a compression stroke of a piston rod, a check valve is opened to introduce pressure from a lower chamber of a cylinder into a back pressure chamber of an extension-side main valve. The shock absorber thus prevents a damping force from being released when the extension-side main valve is opened by the pressure of the lower chamber of the cylinder during the compression stroke. COUNTERPOINT LIST PATENT LITERATURE

[0003] Patent literature 1: JP 2005- 344 911 A

[0004] DE 11 2014 005 430 T5 discloses features that fall under the preamble of claim 1. DE 10 2015 216 508 A1, DE 10 2011 081 792 A1 and KR 10 2012 0 087 669 A are further prior art. BRIEF DESCRIPTION OF THE INVENTIONAL TECHNICAL TASK

[0005] The shock absorber disclosed in patent literature 1 introduces the hydraulic oil from an upstream chamber into the counter-pressure chamber during a reverse stroke, so that paths (channels) are formed by attaching a plurality of disks and a check valve. In such a case, the cylinder must have a large axial length (overall length), and the size of the shock absorber is increased accordingly. SOLUTION TO THE TASK

[0006] One object of the invention is to provide a shock absorber that can be miniaturized.

[0007] The shock absorber according to one embodiment of the invention comprises a cylinder containing hydraulic fluid in a closed manner; a piston slidably fitted within the cylinder; a piston rod having a first end coupled to the piston and a second end extending outside the cylinder; a main valve configured to generate a damping force by controlling a flow of hydraulic fluid from an upstream chamber to a downstream chamber, generated when the piston moves in a first direction; a backpressure chamber located in the downstream chamber, exerting backpressure on the main valve in a valve closing direction; and a sealing mechanism that moves with the movement of an outer peripheral section of the main disk when the main valve is open, thereby defining the backpressure chamber.and a backpressure inlet path for introducing the hydraulic fluid in the upstream chamber into the backpressure chamber. The shock absorber controls the opening of the main valve using the backpressure of the backpressure chamber. When the piston moves in a second direction, the sealing mechanism acts as a valve that introduces the hydraulic fluid from the chamber that becomes a downstream chamber when the piston moves in the first direction into the backpressure chamber.

[0008] One embodiment of the invention makes it possible to reduce the size of the shock absorber. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a cross-sectional view of a part of a shock absorber according to a first embodiment. Fig. 2 is an enlarged view of a main part from Fig. 1. Fig. Figure 3 is a cross-sectional view of a part of a shock absorber according to a second embodiment. Fig. Figure 4 is an enlarged view of a main part from Fig. 3. Fig. Figure 5 is an explanatory view of a third embodiment and corresponds to Fig. 2, which shows the first embodiment. DESCRIPTION OF EXECUTION FORMS (First embodiment)

[0009] A first embodiment of the invention is discussed with reference to the accompanying drawings.

[0010] A shock absorber 1 according to the first embodiment is a single-cylinder hydraulic shock absorber mounted between an unsprung (wheel) side and a sprung (vehicle body) side of a suspension system of a passenger car or the like. For the sake of simplicity, a vertical direction is assumed. Fig. 1 and Fig. 2 is designated as a vertical direction in the shock absorber 1 according to the first embodiment.

[0011] With reference to Fig. In Figure 1, a piston 3 is movably (slidably) fitted inside a cylinder 2. The piston 3 divides the interior of the cylinder 2 into two chambers: an upper chamber 2A and a lower chamber 2B. A shaft section 5 (small-diameter section) is coupled to the piston 3, forming the first end of a piston rod 4. The second end of the piston rod 4 is inserted into a rod guide and an oil seal (both not shown), which are mounted on an upper end section of the cylinder 2. The second end of the piston rod 4 extends from the cylinder 2.

[0012] A free piston, not shown, is provided inside cylinder 2. The free piston is vertically movable within cylinder 2. The free piston divides the interior of cylinder 2 into the lower chamber 2B of the cylinder on the side of piston 3 and a gas chamber, not shown, on the side of a lower section. Hydraulic oil is injected and enclosed as hydraulic fluid in the upper chamber 2A and the lower chamber 2B of the cylinder. High-pressure gas (nitrogen gas) is injected and enclosed as hydraulic fluid in the gas chamber.

[0013] The piston 3 is equipped with a multitude of extension-side paths 7 and compression-side paths 8 ( Fig. Figure 1 shows only one of each, which brings the upper chamber 2A and the lower chamber 2B of the cylinder into communication with each other. An extension-side main valve 21 is provided on one side of the lower end of the piston 3. The extension-side main valve 21 is located in the lower chamber 2B of the cylinder, which becomes a downstream chamber during an extension stroke. During the extension stroke, the extension-side main valve 21 controls a flow of hydraulic oil from the upper chamber 2A of the cylinder (upstream chamber) to the lower chamber 2B of the cylinder (downstream chamber), which is generated by an upward sliding movement of the piston 3 (one-sided), in order to produce an extension-side damping force.

[0014] Furthermore, a cylindrical counter-pressure chamber forming element 22 with a base is provided on the lower end of the piston 3. A substantially cylindrical inner peripheral section 23 is formed on an inner peripheral side of the counter-pressure chamber forming element 22. The shaft section 5 of the piston rod 4 is fitted into the inner peripheral section 23. The inner peripheral section 23 is held between an inner peripheral section 6 of the piston 3 and a washer 12 by an axial force generated by tightening a nut 11 mounted on the shaft section 5 (hereinafter referred to as the "axial force of the nut 11"). A washer 24, a retainer 26, and a washer 27 are also provided between the counter-pressure chamber forming element 22 and the washer 12, in that order starting from the top.The disc 24, the bracket 26 and the disc 27 are layered between the inner peripheral section 23 of the counter-pressure chamber forming element 22 and the washer 12 by the axial force of the nut 11.

[0015] An annular seat section 32 is provided on the outer peripheral side of the lower end section of the piston 3. An outer peripheral section of the extension-side main valve 21, which has a disc-like shape, sits on the seat section 32. The extension-side main valve 21 is not clamped on an inner peripheral section and is therefore simply supported by the bracket 33, which is mounted on the shaft section 5 of the piston rod 4. A small-diameter shaft section 34 is formed at an upper end section of the bracket 33. An inner peripheral surface of the extension-side main valve 21 is slidably fitted on the shaft section 34. An annular seat section 35 is formed on an outer peripheral side of the shaft section 34.The seat section 35 is in contact with a rear surface (opposite surface to a surface that sits on the seat section 32 of the piston 3) of the inner peripheral section of the extension-side main valve 21.

[0016] In other words, the inner peripheral section of the extension-side main valve 21 sits on the seat section 35 of the bracket 33 and is supported by the shaft section 34 of the bracket 33 so that it is movable in the vertical direction. A disc-like regulating element 36 is provided between the shaft section 34 of the bracket 33 and the inner peripheral section 6 of the piston 3. The regulating element 36 controls an upward movement of the inner peripheral section of the extension-side main valve 21. The seat section 35 of the bracket 33 is designed such that its outer diameter decreases towards a distal end (upper end).

[0017] With reference to Fig. 1 and Fig. 2 A ring-like seal 37 is rigidly fixed to the rear surface of the extension-side main valve 21. The seal 37 functions as a sealing mechanism comprising an elastic body made of rubber or the like. The seal 37 includes an outer peripheral sealing section 38 (sealing mechanism) that is in sliding contact with an inner peripheral surface 40 of a cylinder section 39 of the backpressure chamber forming element 22, and an inner peripheral sealing section 41 (locking element) that is in sliding contact with an outer peripheral surface 42 of the retaining element 33. A backpressure chamber 43 of the extension-side main valve 21 is defined and formed inside the backpressure chamber forming element 22.The seal 37 comprises an outer peripheral sealing section 38, an inner peripheral sealing section 41 and a base section 44, which is a base of the seal 37, which are formed in one piece.

[0018] The outer peripheral sealing section 38 is an annular wall extending downwards from the base section 44. The outer peripheral sealing section 38 has an outer and an inner diameter that increase downwards to a substantially conical shape. Due to this shape, the outer peripheral sealing section 38 absorbs the pressure of the backpressure chamber 43, so that it is pressed against the inner peripheral surface 40 of the cylindrical section 39 of the backpressure chamber forming element 22. During the extension stroke of the piston rod 4, the hydraulic oil in the upper chamber 2A of the cylinder (upstream chamber) is introduced into the backpressure chamber 43 through an extension-side backpressure inlet path, which will be discussed later. An annular gap 45 is formed between an outer peripheral section of the seal 37 and the cylindrical section 39 of the backpressure chamber forming element 22.The gap 45 has a wedge-shaped cross-section along a plane encompassing an axis of the piston rod 4 (hereinafter referred to as a "cross-section along the axis plane"). The gap 45 opens into (communicates with) the lower chamber 2B of the cylinder.

[0019] The inner peripheral sealing section 41 is an annular wall extending downwards from the base section 44. The inner peripheral sealing section 41 has an outer and an inner diameter that increase downwards to a substantially conical shape. Due to this shape, the inner peripheral sealing section 41 absorbs the pressure of the counter-pressure chamber 43, so that it is pressed against the outer peripheral surface 42 of the holder 33. An annular recessed section 50 is formed on an outer peripheral side of the inner peripheral sealing section 41. The shape (depth or the like) of the recessed section 50 makes it possible to adapt the inner peripheral sealing section 41 with respect to an area that absorbs the pressure of the counter-pressure chamber 43.

[0020] An inner peripheral surface of the inner peripheral section 23 of the counterpressure chamber forming element 22 is provided with an annular path 46 opening into an upper end surface of the inner peripheral section 23 and an annular path 47 opening into a lower end surface of the inner peripheral section 23. The upper path 46 and the lower path 47 communicate with each other via a groove-like path 14 extending in the vertical direction. The path 14 is formed in an outer peripheral surface of the shaft section 5 of the piston rod 4. A disk 48 is arranged between the inner peripheral section 23 of the counterpressure chamber forming element 22 and the support 33.The counterpressure chamber 43 is connected by a slot-like path 49 formed in the disk 48 and the lower path 46 of the inner peripheral section 23 of the counterpressure chamber forming element 22 in communication with the path 14 of the wave section 5.

[0021] The piston 3 is provided with a compression-side main valve 51 at one of its upper ends. The compression-side main valve 51 is located in the upper chamber 2A of the cylinder, which becomes the downstream chamber during a compression stroke. During the compression stroke, the compression-side main valve 51 controls a flow of hydraulic oil from the lower chamber 2B of the cylinder (upstream chamber) to the upper chamber 2A of the cylinder (downstream chamber), which is generated by the downward sliding movement of the piston 3, thereby producing a compression-side damping force.

[0022] A backpressure chamber forming element 52 is also provided on the upper end face of the piston 3. The backpressure chamber forming element 52 is a cylindrical housing element with a base. An essentially cylindrical inner peripheral section 53 is formed in an inner peripheral side of the backpressure chamber forming element 52. The shaft section 5 of the piston rod 4 is fitted into the inner peripheral section 53. The inner peripheral section 53 is held by the axial force of the nut 11 between the inner peripheral section 6 of the piston 3 and a washer 13. A washer 54, a retainer 56, and a washer 57 are provided between the backpressure chamber forming element 52 and the washer 13, in that order starting from the base.The disc 54, the bracket 56 and the disc 57 are layered between the inner peripheral section 53 of the counter-pressure chamber forming element 52 and the washer 13 by the axial force of the nut 11.

[0023] An annular seat section 62 is provided on an outer peripheral side of an upper end section of the piston 3. The outer peripheral section of the compression-side main valve 51, which has a disc-like shape, sits on the seat section 62. The compression-side main valve 51 is not clamped on an inner peripheral section of the seat section 62 and is simply supported by a bracket 63 mounted on the shaft section 5 of the piston rod 4. The bracket 63 has a lower end section in which a small-diameter shaft section 64 is formed. An inner peripheral surface of the compression-side main valve 51 is slidably fitted on the shaft section 64. An annular seat section 65 is formed on an outer peripheral side of the shaft section 64.The seat section 65 is in contact with a rear surface (opposite surface to a surface on which the seat section 62 of the piston 3 sits) of the inner peripheral section of the compression-side main valve 51.

[0024] In other words, the inner peripheral section of the compression-side main valve 51 sits on the seat section 65 of the bracket 63 and is supported by the shaft section 64 of the bracket 63, allowing it to move vertically. A disc-like regulating element 66 is provided between the shaft section 64 of the bracket 63 and the inner peripheral section 6 of the piston 3. The regulating element 66 controls a downward movement of the inner peripheral section of the compression-side main valve 51. The seat section 65 of the bracket 63 is designed such that its outer diameter decreases towards a distal end (lower end).

[0025] A ring-like seal 67 is rigidly fixed to a rear surface of the compression-side main valve 51. The seal 67 comprises an elastic body made of rubber or the like. The seal 67 includes an outer peripheral sealing section 68, which is in sliding contact with an inner peripheral surface 70 of a cylinder section 69 of the backpressure chamber forming element 52, and an inner peripheral sealing section 71 (locking element), which is in sliding contact with an outer peripheral surface 72 of the retainers 63. This forms a back pressure chamber 73 of the compression-side main valve 51 inside the back pressure chamber forming element 52. The seal 67 comprises the outer peripheral sealing section 68, the inner peripheral sealing section 71 and a base section 74, which is a base of the seal 67, which are formed in one piece.According to the present embodiment, the inner peripheral sealing section 71 (locking element) is rigidly fixed to the rear surface of the compression-side main valve 51. Alternatively, the inner peripheral sealing section 71 can be configured such that, for example, an O-ring is installed between the bracket 63 and the compression-side main valve 51, or that a seal is rigidly fixed to the inner peripheral side of the compression-side main valve 51, extending between the front and rear surfaces of the compression-side main valve 51.

[0026] The outer peripheral sealing section 68 is an annular wall extending upwards from the base section 74. The outer peripheral sealing section 68 has an outer and an inner diameter that increase upwards to a substantially conical shape. Due to this shape, the outer peripheral sealing section 68 absorbs the pressure of the backpressure chamber 73, so that it is pressed against the inner peripheral surface 70 of the cylindrical section 69 of the backpressure chamber forming element 52. During the compression stroke of the piston rod 4, the hydraulic oil in the lower chamber 2B of the cylinder (upstream chamber) is introduced into the backpressure chamber 73 through a compression-side backpressure inlet path, which will be discussed later. An annular gap 75 is formed between an outer peripheral section of the seal 67 and the cylindrical section 69 of the backpressure chamber forming element 52.The gap 75 has a wedge-shaped cross-section along the axial plane. The gap 75 opens into (communicates with) the upper chamber 2A of the cylinder.

[0027] The inner peripheral sealing section 71 is an annular wall extending upwards from the base section 74. The inner peripheral sealing section 71 has an outer and an inner diameter that increase upwards to a substantially conical shape. Due to this shape, the inner peripheral sealing section 71 absorbs the pressure of the counter-pressure chamber 73, so that it is pressed against the outer peripheral surface 72 of the holder 63. An annular recessed section 80 is formed on an outer peripheral side of the inner peripheral sealing section 71. The shape (depth or the like) of the recessed section 80 makes it possible to adapt the inner peripheral sealing section 71 with respect to an area that absorbs the pressure of the counter-pressure chamber 73.

[0028] An annular path 76 and an annular path 77 are provided in an inner peripheral surface of the inner peripheral section 53 of the counterpressure chamber forming element 52. Path 76 opens into a lower end surface of the inner peripheral section 53, and path 77 opens into an upper end surface of the inner peripheral section 53. The lower path 76 and the upper path 77 communicate with each other via path 14, which is formed in the outer peripheral surface of the shaft section 5 of the piston rod 4. A disk 78 is arranged between the inner peripheral section 53 of the counterpressure chamber forming element 52 and the support 63. The counterpressure chamber 73 communicates with the path 14 of the wave section 5 through a slot-like path 79 formed in the disk 78 and the lower path 76 of the inner peripheral section 53 of the counterpressure chamber forming element 52.

[0029] During the extension stroke of the piston rod 4, as the piston 3 moves upwards, the hydraulic oil in the upper chamber 2A of the cylinder (upstream chamber) is introduced into the back pressure chamber 43 of the extension-side main valve 21 through the extension-side back pressure introduction path, which includes a path 16 formed in an inner peripheral side of the disk 54, the path 77 formed in the back pressure chamber forming element 52, the path 14 formed in the shaft section 5 of the piston rod 4, and the path 49 formed in the disk 48.

[0030] During the compression stroke of the piston rod 4, as the piston 3 moves downwards, the hydraulic oil in the lower chamber 2B of the cylinder (upstream chamber) is introduced into the back pressure chamber 73 of the compression-side main valve 51 through the compression-side back pressure introduction path, which includes a path 18 formed in an inner peripheral side of the disk 24, the path 47 formed in the back pressure chamber forming element 22, the path 14 formed in the shaft section 5 of the piston rod 4, and the path 79 formed in the disk 78.

[0031] The following explanation concerns the operation of the first embodiment.

[0032] During the first extension stroke of the piston rod 4, the damping force is generated by controlling the flow of hydraulic oil from the upper chamber 2A of the cylinder (upstream chamber) to the lower chamber 2B of the cylinder (downstream chamber), which is generated by the sliding (upward) movement of the piston 3 within the cylinder 2. During the extension stroke, the hydraulic oil (pressure) in the upper chamber 2A of the cylinder is introduced into the backpressure chamber 43 of the extension-side main valve 21 via the extension-side backpressure inlet path.

[0033] In a region of extremely low speeds, where the piston 3 moves vertically at an extremely low speed during the extension stroke (hereinafter referred to as the vertical speed as a "piston speed"), the hydraulic oil in the upper chamber 2A of the cylinder flows through the path 16 formed in the inner peripheral side of the disk 54, the path 77 formed in the inner peripheral side 53 of the counter-pressure chamber forming element 52, the path 14 formed in the shaft section 5 of the piston rod 4, the path 47 formed in the inner peripheral section 23 of the counter-pressure chamber forming element 22, and the path 18 formed in the inner peripheral side of the disk 24 into the lower chamber 2B of the cylinder, thereby generating a damping force with opening characteristics.

[0034] When the extension-side main valve 21 is opened by an increase in piston speed, a damping force with valve properties corresponding to an opening degree of the extension-side main valve 21 is generated.

[0035] According to the first embodiment, during the compression stroke of the piston rod 4, which is a return stroke, the outer peripheral sealing section 38 (sealing mechanism) of the seal 37 absorbs the pressure of the lower chamber 2B of the cylinder, causing it to bend or deflect (lean) towards the inner peripheral side and disengage from contact (separably or selectively away from and into contact with). Consequently, the hydraulic oil (pressure) from the lower chamber 2B of the cylinder is introduced into the back pressure chamber 43. The outer peripheral sealing section 38 thus acts as a check valve. A force acting on the extension-side main valve 21 in a valve closing direction is then greater than a force acting on the extension-side main valve 21 in a valve opening direction.Therefore, it is possible to suppress the opening of the extension-side main valve 21 during the reverse stroke and to obtain a stable damping force.

[0036] During the compression stroke of the piston rod 4, which is the return stroke, hydraulic oil (pressure) is introduced into the lower chamber 2B of the cylinder through an outer periphery of the extension-side main valve 21 into the back pressure chamber 43. The inner periphery-side sealing section 41 (locking element) of the seal 37 absorbs the pressure of the back pressure chamber 43, so that it is pressed against the outer periphery surface 42 of the bracket 33. This prevents the hydraulic oil (pressure) introduced into the back pressure chamber 43 during the compression stroke (return stroke) from flowing into the extension-side path 7 through a gap between the inner periphery section of the simply supported extension-side main valve 21 and the bracket 33, and prevents the damping force from being released by the flow of hydraulic oil into the upper chamber 2A of the cylinder.

[0037] During the compression stroke of the piston rod 4, the damping force is generated by controlling the flow of hydraulic oil from the lower chamber 2B of the cylinder (upstream chamber) to the upper chamber 2A of the cylinder (downstream chamber), which is generated by the sliding (downward) movement of the piston 3 within the cylinder 2. During the compression stroke, the hydraulic oil (pressure) in the lower chamber 2B of the cylinder is introduced into the backpressure chamber 73 of the compression-side main valve 51 via the aforementioned compression-side backpressure inlet path.

[0038] In a region of extremely low speeds, where the piston 3 moves at an extremely low speed during the compression stroke, the hydraulic oil in the lower chamber 2B of the cylinder flows through the path 18 formed in the inner peripheral side of the disk 24, the path 47 formed in the inner peripheral section 23 of the counter-pressure chamber forming element 22, the path 14 formed in the shaft section 5 of the piston rod 4, the path 77 formed in the inner peripheral side 53 of the counter-pressure chamber forming element 52, and the path 16 formed in the inner peripheral side of the disk 54 into the upper chamber 2A of the cylinder, thereby generating a damping force with opening characteristics.

[0039] When the compression-side main valve 51 is opened by an increase in piston speed, a damping force with valve properties corresponding to an opening degree of the compression-side main valve 51 is generated.

[0040] According to the first embodiment, during the compression stroke of the piston rod 4, which is a return stroke, the outer peripheral sealing section 68 (movable element) of the seal 67 absorbs the pressure of the upper chamber 2A of the cylinder, causing it to bend or deflect (lean) towards the inner peripheral side. Subsequently, the hydraulic oil (pressure) in the upper chamber 2A of the cylinder is introduced into the counter-pressure chamber 73. Consequently, a force acting on the compression-side main valve 51 in a valve-closing direction is greater than a force acting on the compression-side main valve 51 in a valve-opening direction. Therefore, it is possible to suppress the opening of the compression-side main valve 51 during the return stroke and to obtain a stable damping force.

[0041] During the extension stroke of the piston rod 4, which is the return stroke, the hydraulic oil (pressure) in the upper chamber 2A of the cylinder is introduced through an outer periphery of the compression-side main valve 51 into the back pressure chamber 73, and the inner periphery-side sealing section 71 (locking element) of the seal 67 absorbs the pressure of the back pressure chamber 73, so that it is pressed against the outer periphery surface 72 of the bracket 63. This prevents the hydraulic oil (pressure) introduced into the back pressure chamber 73 during the extension stroke (return stroke) from flowing through a gap between the inner periphery section of the simply supported compression-side main valve 51 and the bracket 63 into a compression-side path 8, and prevents the damping force from being released by the flow of hydraulic oil into the lower chamber 2B of the cylinder.

[0042] As disclosed in patent literature 1, when paths (channels) are formed by arranging a plurality of disks and a check valve to introduce hydraulic oil from an upper chamber into a counter-pressure chamber during a reverse stroke, the axial length of the shaft section of a piston rod, and thus the total length of a cylinder, is increased, and accordingly the size of the shock absorber is increased.

[0043] In contrast, according to the first embodiment, the hydraulic fluid in chambers 2B and 2A, which become the upstream chambers during the return stroke of the piston rod 4, is introduced through the outer peripheries of the main valves 21 and 51 into the backpressure chambers 43 and 73. This eliminates the need to create the paths (channels) by installing the plurality of disks and the check valve, with the paths serving to introduce the hydraulic fluid from chambers 2B and 2A, which become the upstream chambers during the return stroke, into the backpressure chambers 43 and 73. This makes it possible to reduce the axial length of the shaft section 5 of the piston rod 4, and thus the overall length of the cylinder 2, and also to reduce the size of the shock absorber 1.

[0044] The first embodiment offers the following advantageous effects.

[0045] According to the first embodiment, a shock absorber comprises a cylinder containing hydraulic fluid in a closed manner; a piston slidably fitted within the cylinder; a piston rod having a first end coupled to the piston and a second end extending outside the cylinder; a main valve configured to generate a damping force by controlling a flow of hydraulic fluid from an upstream chamber to a downstream chamber, generated when the piston moves in a first direction; a backpressure chamber located in the downstream chamber, exerting backpressure on the main valve in a valve closing direction; and a sealing mechanism that moves with the movement of an outer peripheral section of the main disk when the main valve is open, thus defining the backpressure chamber.and a backpressure inlet path for introducing the hydraulic fluid from the upstream chamber into the backpressure chamber. The shock absorber controls the opening of the main valve using the backpressure of the backpressure chamber. When the piston moves in a second direction, the sealing mechanism acts as a valve, introducing the hydraulic fluid in the chamber that becomes a downstream chamber when the piston moves in the first direction into the backpressure chamber, thus introducing the hydraulic fluid into the chamber that becomes an upstream chamber during a return stroke of the piston rod. This eliminates the need to create the paths (channels) by arranging a multitude of disks and check valves, and makes it possible to reduce the axial length (overall length) of the cylinder and thus make the shock absorber smaller.

[0046] When the inner peripheral section of the main valve is clamped as disclosed in patent literature 1, the bending stiffness of the disk forming the main valve increases, making it difficult to reduce the damping force on the soft side. However, the first embodiment includes a simple (cantilever) support structure in which the main valve is not clamped on the inner peripheral side, allowing the main valve to open at a lower piston speed. This makes it possible to adjust the damping force on the soft side to a smaller value, thus improving the ride comfort of a vehicle. If the damping force to be generated on the soft side is the same, it is possible to use a main valve with a smaller outer diameter compared to the main valve clamped on the inner peripheral section.This makes it possible to reduce the cylinder's outer diameter and to make the shock absorber smaller.

[0047] According to the first embodiment, a blocking element is provided in the inner peripheral side of the main valve to prevent the flow of hydraulic fluid into the upstream chamber during the return stroke, when the piston slides in the second direction. This prevents the hydraulic fluid in the backpressure chamber from flowing through an inner peripheral side of the simply supported main valve into the upstream chamber and prevents the damping force from being released.

[0048] According to the first embodiment, a movable element is a seal that is integrally formed in an outer periphery of the main valve. This reduces the number of components and thus the number of assembly steps. According to the first embodiment, the movable element and the locking element are formed on the outer and inner peripheral sides of the seal, respectively. Furthermore, the main valve, the movable element, and the locking element are formed integrally. Therefore, by providing the locking element, it is possible to prevent an increase in the number of components.

[0049] The movable element and the locking element need not necessarily be formed on the outer and inner peripheral sides of a seal. The movable element and the locking element can be provided separately such that a movable element comprising a seal is provided on the outer peripheral side of the main valve, and a locking element comprising a seal is provided on the inner peripheral side of the main valve.

[0050] The locking element can be, for example, an O-ring or similar instead of a seal.

[0051] Although the first embodiment relates to the case in which the invention is applied to a single-cylinder hydraulic shock absorber, the invention can also be applied to a multi-cylinder hydraulic shock absorber in which a reservoir is formed between the cylinders 2 and an outer tube. In such a case, a free piston is not required, and a base valve is provided between the lower chamber 2B of the cylinder and the reservoir. Providing a plurality of cylinders makes it possible to further reduce the axial length of the cylinder 2. (Second embodiment)

[0052] A second embodiment is described below with reference to Fig. 3 and Fig. 4 explained. The following explanation mainly concerns differences compared to the first embodiment. Similar names and reference numerals denote parts common to the first embodiment, and repetitive descriptions are omitted.

[0053] The shock absorber 1 according to the first embodiment is a so-called conventional suspension damper with a single damping force characteristic with respect to piston speed. A shock absorber 81 according to the second embodiment is a so-called semi-active suspension damper comprising a damping force-variable mechanism 82. In this description, the shock absorber 81 according to the second embodiment, which includes the damping force-variable mechanism 82, is similar in its basic structure to a conventional semi-active suspension damper. Therefore, the basic structure of the semi-active suspension damper is not described in detail.

[0054] A main valve 21 of the second embodiment, located on the extension side, is simply supported by a bracket 33 mounted on a shaft section 84 of a piston housing 83. A seal 37 is rigidly fixed to a rear surface of the main valve 21 on the extension side. The seal 37 comprises an outer peripheral sealing section 38, which is in sliding contact with an inner peripheral surface 40 of a cylindrical section 39 of a backpressure chamber forming element 22. The seal 37 further comprises an inner peripheral sealing section 41, which is in sliding contact with an outer peripheral surface 42 of the bracket 33. Accordingly, an annular backpressure chamber 43 is formed inside the backpressure chamber forming element 22.In the first embodiment, the movement of the extension-side main valve 21 is regulated by the regulating element 36, which is provided between the shaft section 34 of the bracket 33 and the inner peripheral section 6 of the piston 3. The second embodiment regulates the movement of the extension-side main valve 21 instead by means of the inner peripheral section 6 of the piston 3.

[0055] The piston 3 is provided with an annular seat section 87 in an upper end section thereof. A disc valve 88, comprising a plurality of discs, is seated on the seat section 87. An annular valve element 89 is mounted on an upper end section of the shaft section 84 of the piston housing 83. A disc valve 90, mounted on the shaft section 84 of the piston housing 83, is provided in a lower end section of the valve element 89. The disc valve 90 sits on an annular seat section 91, which is provided in an outer peripheral edge section of the lower end section of the valve element 89, and on an annular seat section 92, which is provided in an inner peripheral side with respect to the seat section 91.

[0056] During a piston rod 4 extension stroke, the piston 3 moves (slides) upwards. Simultaneously with this movement of the piston 3, hydraulic oil in an upper chamber 2A of a cylinder (upstream chamber) is introduced into the backpressure chamber 43 of the extension-side main valve 21 through an extension-side backpressure inlet path comprising an opening 93 formed in the seat section 91 located on an outer peripheral side of the valve element 89, a path 94 located in the seat section 92 located on an inner peripheral side of the valve element 89, a path 95 formed in a lower end section of an inner peripheral section of the valve element 89, a path 14 formed in the shaft section 8 of the piston housing 83, and a path 49 formed in a disk 48.

[0057] An operation of the second embodiment will now be explained.

[0058] During an extension stroke of the piston rod 4, when hydraulic oil (hydraulic fluid) on the side of the upper chamber 2A of the cylinder is pressurized by the sliding movement of the piston 3 within a cylinder 2, the hydraulic oil in the upper chamber 2A of the cylinder (upstream chamber) is introduced into the backpressure chamber 43 through the aforementioned extension-side backpressure introduction path, while a valve body 96 is closed. Subsequently, the extension-side main valve 21 can be adjusted with respect to a set load (valve opening pressure) by controlling a thrust force (control current) of a solenoid coil 97 to vary the pressure of the backpressure chamber 43, i.e., the backpressure of the extension-side main valve 21.

[0059] During a compression stroke, hydraulic oil (hydraulic fluid) on the side of a lower chamber 2B of a cylinder is pressurized by the sliding movement of the piston 3 within the cylinder 2. The hydraulic oil in the lower chamber 2B of the cylinder then passes through a compression-side path 20 and opens the disc valve 88 to flow into the upper chamber 2A of the cylinder. At this point, a damping force with valve characteristics of the disc valve 88 is obtained. During the compression stroke, the valve body 98 is opened against the thrust of the solenoid 97 by controlling the thrust (control current) of the solenoid 97 to vary a set load (valve opening pressure) of a valve body 98. The hydraulic oil in the lower chamber 2B of the cylinder then passes through a path 99, a chamber 100, a path 101, and an annular path 102.The hydraulic oil further opens the disc valve 90, in which the path 94 (backpressure chamber inlet path) is formed, in order to flow into the upper chamber 2A of the cylinder. At this point, a damping force with valve characteristics of the disc valve 90 is obtained.

[0060] The second embodiment offers similar operation and similar advantageous effects as the first embodiment. (Third embodiment)

[0061] A third embodiment is now described with reference to Fig. 5 explained. The following explanation mainly concerns differences compared to the first embodiment. Similar names and reference numerals denote parts common to the first embodiment, and repetitive descriptions are omitted.

[0062] In the first embodiment, the outer peripheral sealing section 38 (sealing mechanism) of the seal 37 is brought into sliding contact with the inner peripheral surface 40 of the cylindrical section 39 of the backpressure chamber forming element 22, thereby forming the backpressure chamber 43 of the extension-side main valve 21. In contrast, according to the third embodiment, a valve seat 111 (sealing mechanism), as a cylinder-like cylindrical element, is brought into contact with a rear surface (opposite a surface on which a seat section 32 of a piston 3 sits) of an outer peripheral section of an extension-side main valve 21, thereby forming a backpressure chamber 43 of the first extension-side main valve 21.

[0063] A projecting section 112, extending towards an inner periphery, is provided in an upper end section of the valve seat 111. An annular seat section 113 is formed in an upper surface of an inner peripheral section of the projecting section 112. The seat section 113 is opposite the seat section 32 of the piston 3. An annular seat section 114 is formed in a lower surface of the inner peripheral section of the projecting section 112. The seat section 114 of the valve seat 111 sits on an outer peripheral edge section of a disk 115, which has elasticity. Due to the elasticity of the disk 115, the valve seat 111 is biased upwards, and the seat section 113 is pressed against the extension-side main valve 21.The disk 115 comprises an inner peripheral section that is layered between a support 33 and an inner peripheral section of a counterpressure chamber forming element 116 (cylindrical element) as a ring-like clamped circular plate.

[0064] The backpressure chamber forming element 116 is mounted on a shaft section 5 of a piston rod 4 by means of an axial force exerted by a nut 11. The valve seat 111 comprises an inner peripheral surface 118, which is in sliding contact with an outer peripheral end surface 117 of the backpressure chamber forming element 116. A gap between the outer peripheral end surface 117 of the backpressure chamber forming element 116 and the inner peripheral surface 118 of the valve seat 111 is sealed liquid-tight by means of an annular sealing section 119, which is provided on the outer peripheral end surface 117 of the backpressure chamber forming element 116.

[0065] During a stroke of the piston rod 4, hydraulic oil in an upper chamber 2A of a cylinder (upstream chamber) is introduced into the backpressure chamber 43 via a backpressure inlet path comprising a path 14 formed in the shaft section 5 of the piston rod 4, an annular path 120 formed in an inner peripheral surface of the backpressure chamber forming element 116, and a path 121 (cutout) formed in the inner peripheral section of the disk 115. An annular chamber 122 is formed between the disk 115 and the backpressure chamber forming element 116. The chamber 122 and the backpressure chamber 43 communicate with each other via a path 123 (cutout) formed in an outer peripheral section of the disk 115.

[0066] Operation of the third embodiment is discussed below.

[0067] During the extension stroke of the piston rod 4, the hydraulic oil (pressure) in the upper chamber 2A of the cylinder is introduced into the back pressure chamber 43 of the extension-side main valve 21 via the aforementioned extension-side back pressure introduction path. When the extension-side main valve 21 is opened by an increase in piston velocity, a damping force with valve characteristics corresponding to the opening degree of the extension-side main valve 21 is generated.

[0068] During a compression stroke of the piston rod 4, which is a return stroke, the valve seat 111 (sealing mechanism) absorbs pressure from a lower chamber 2B of the cylinder and moves (slides) downwards. The seat section 113 of the valve seat 111 is then separated from the extension-side main valve 21, which allows the hydraulic oil (pressure) in the lower chamber 2B of the cylinder to pass through an outer periphery of the extension-side main valve 21 into the back pressure chamber 43. Accordingly, a force acting on the extension-side main valve 21 in a valve-closing direction is greater than a force acting on the extension-side main valve 21 in a valve-opening direction. This makes it possible to suppress the opening of the extension-side main valve 21 during the return stroke and to maintain a stable damping force.

[0069] During the compression stroke of the piston rod 4, which is the return stroke, hydraulic oil (pressure) in the lower chamber 2B of the cylinder is introduced through the outer periphery of the extension-side main valve 21 into the back pressure chamber 43. A seal 124 (locking element) then absorbs the pressure of the back pressure chamber 43, pressing it against an outer peripheral surface 42 of the support 33. This prevents the hydraulic oil (pressure) introduced into the back pressure chamber 43 during the compression stroke (return stroke) from flowing into extension-side paths 7 through a gap between an inner peripheral section of the simply supported extension-side main valve 21 and the support 33, and prevents the damping force from being released by the flow of hydraulic oil into the upper chamber 2A of the cylinder.

[0070] The third embodiment offers the same operation and the same advantageous effects as the first embodiment.

[0071] The invention is not limited to the embodiments discussed above and can be modified in various ways. For example, the embodiments are explained in detail to facilitate understanding of the invention and therefore do not necessarily include all the previously mentioned configurations. It is possible to replace the configuration of one embodiment with the configuration of another embodiment, and also to add the configuration of one embodiment to the configuration of another embodiment. A part of the configuration of each embodiment can be added to, from, or replaced by another configuration. REFERENCE MARK LIST 1 shock absorber 2 cylinders 2A Upper chamber of the cylinder 2B Lower chamber of the cylinder 3 pistons 4 piston rod 21 Extension-side main valve 43 Counterpressure chamber 68 Outer peripheral sealing section (sealing mechanism)

Claims

[1] Shock absorber, comprising: a cylinder (2) in which hydraulic fluid is contained in a sealed manner; a piston (3) slidably fitted in the cylinder (2); a piston rod (4) having a first end coupled to the piston (3) and a second end extending outside the cylinder; a main valve (21) configured to generate a damping force by controlling a flow of hydraulic fluid from an upstream chamber (2A) to a downstream chamber (2B) generated when the piston (3) moves in a first direction; a back pressure chamber (43) disposed in the downstream chamber (2B) and exerting back pressure acting on the main valve (21) in a valve closing direction; a sealing mechanism (38) which moves with movement of an outer peripheral portion of the main disc when the main valve (21) is opened and defines the back pressure chamber (43); and a back pressure introduction path for introducing the hydraulic fluid of the upstream chamber into the back pressure chamber (43), wherein opening of the main valve is controlled by means of the back pressure of the back pressure chamber (43), and characterized by , that the sealing mechanism (38) is designed to act as a valve that directs the hydraulic fluid in the chamber, which becomes a downstream chamber (2B) when the piston (3) moves in the first direction, into the backpressure chamber (43) when the piston (3) moves in a second direction. [2] A shock absorber according to claim 1, wherein the sealing mechanism (38) is a flexible seal integrally provided on an outer periphery of the main valve (21). [3] A shock absorber according to claim 2, wherein the shock absorber comprises a cylinder-like housing member (22) with a bottom forming the back pressure chamber (43), and wherein the seal is provided so as to be capable of coming into contact with and disengaging from a cylindrical portion of the housing member (22). [4] Shock absorber according to claim 1, wherein the sealing mechanism comprises a cylindrical member (111) capable of coming into contact with and disengaging from the main valve (21), and wherein the back pressure chamber (43) is defined by the sealing mechanism (38) and a clamped circular plate provided to be slidable relative to an inner peripheral side of the cylindrical member (111). [5] A shock absorber according to any one of claims 1 to 3, wherein the main valve (21) is supported with an unconstrained inner peripheral side. [6] A shock absorber according to claim 5, wherein the inner peripheral side of the main valve (21) is provided with a blocking member (124) which blocks a flow of hydraulic fluid from the back pressure chamber (43) into the upstream chamber (2A) which is generated when the piston (3) moves in the second direction. [7] A shock absorber according to claim 6, wherein the locking member (124) is a seal provided integrally on the inner peripheral side of the main valve (21). [8] A shock absorber according to claim 6 or 7, wherein a ring-like recessed portion (50) is formed on an outer peripheral side of the locking member (124).

Images