Shock absorber

Abstract

To provide a shock absorber that is compact, light-weight, and reducible in manufacturing cost, and can improve mountability to a vehicle.SOLUTION: A shock absorber D comprises: a cylinder 1; a cylindrical piston rod 2 which is inserted into the cylinder 1 movably in an axial direction; a piston 3 which is coupled to the piston rod 2 and is inserted into the cylinder 1 movably in the axial direction, and also partitions the inside of the cylinder 1 into an expansion-side chamber R1 and a compression-side chamber R2; a cap 10 which closes a compression-side chamber-side end of the cylinder 1; a cylindrical inner rod 4 which extends from the cap 10 to be inserted into the pressure-side chamber R2, and is fitted slidably in the piston rod 2; a main damping passage M which gives resistance to a flow of fluid flowing forth and back between the expansion-side chamber R1 and the compression-side chamber R2; a bypass passage B which bypasses the main damping passage to link the expansion-side chamber R1 and the compression-side chamber R2 through the inside of the piston rod 2 and the inside of the inner rod 4; and a damping force adjustment valve 21 which is provided in the bypass passage B.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a shock absorber.

Background Art

[0002] A shock absorber is used, for example, interposed between the vehicle body and the wheels of a saddle-riding type vehicle, and suppresses vibrations of the vehicle body and the wheels with the damping force generated during expansion and contraction.

[0003] Such a shock absorber includes, for example, a cylinder, a piston movably inserted into the cylinder and partitioning the inside of the cylinder into an extension chamber and a compression chamber filled with hydraulic oil, a piston rod movably inserted into the cylinder and connected to the piston, a tank for storing hydraulic oil, a hard-side damping element provided on the piston for communicating the extension chamber and the compression chamber and providing resistance to the flow of the hydraulic oil passing therethrough, a bypass passage bypassing the hard-side damping element and communicating the extension chamber and the compression chamber, and a solenoid valve and a soft-side damping element provided in series in the bypass passage (see, for example, Patent Document 1).

[0004] In the shock absorber configured as described above, by adjusting the opening area of the bypass passage with the solenoid valve, the distribution ratio of the flow rate of the hydraulic oil passing through the hard-side damping element and the soft-side damping element is adjusted, and a wide damping force adjustment range can be obtained to output an optimal damping force for suppressing vibrations of the vehicle.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In a conventional shock absorber, an outer shell is provided on the outer periphery of a cylinder, a bypass passage is provided between the cylinder and the outer shell to communicate an extension chamber and a compression chamber outside the cylinder, and a solenoid valve and a soft-side damping element are provided in the bypass passage.

[0007] In this way, in the conventional shock absorber, since a large-diameter outer shell covering the cylinder is required for forming the bypass passage, there are problems that the shock absorber becomes large-sized, the weight increases, and the manufacturing cost also increases. When the shock absorber becomes large-sized, it may be difficult to mount it on some vehicles due to the narrow mounting space, and the increase in weight leads to an increase in fuel consumption, so weight reduction of the shock absorber is required.

[0008] Therefore, an object of the present invention is to provide a shock absorber that is small-sized, lightweight, can reduce manufacturing costs, and can improve mountability on a vehicle.

Means for Solving the Problems

[0009] To solve the above problems, the shock absorber of the present invention includes a cylinder, a cylindrical piston rod movably inserted axially in the cylinder, a piston connected to the piston rod and movably inserted axially in the cylinder to partition the inside of the cylinder into an extension chamber and a compression chamber, a cap closing the compression chamber side end of the cylinder, a cylindrical inner rod extending from the cap and inserted into the compression chamber and slidably fitted into the piston rod, a main damping passage that provides resistance to the flow of liquid flowing back and forth between the extension chamber and the compression chamber, a bypass passage that bypasses the main damping passage and communicates the extension chamber and the compression chamber through the inside of the piston rod and the inside of the inner rod, and a damping force adjustment valve provided in the bypass passage.

[0010] In the shock absorber configured in this way, the bypass passage bypasses the main damping passage and communicates the extension chamber and the compression chamber through the inside of the piston rod and the inside of the inner rod inserted into the piston rod. Since the bypass passage is provided inside the cylinder, a large-diameter outer shell covering the cylinder is not required for forming the bypass passage.

[0011] Further, the cross-sectional area of the annular gap between the inner circumference of the cylinder and the outer circumference of the piston rod may be made larger than the cross-sectional area of the inner rod. According to the shock absorber configured in this way, during the extension operation, the liquid moves from the extension side chamber to the compression side chamber, and during the contraction operation, the liquid moves from the compression side chamber to the extension side chamber. Therefore, the flow of the liquid is the same as that of the conventional shock absorber, and it becomes easy to set the damping force characteristics.

[0012] Furthermore, the shock absorber may include a tank for storing the liquid, a discharge passage communicating the compression side chamber and the tank, a suction passage communicating the tank and the compression side chamber, a compression side damping valve provided in the discharge passage to resist the flow of the liquid from the compression side chamber to the tank, and a suction side valve provided in the suction passage to allow the flow of the liquid from the tank to the compression side chamber.

[0013] According to the shock absorber configured in this way, not only can the damping force be adjusted up and down while ensuring the damping force adjustment range by adjusting the flow rate distribution ratio between the main damping passage and the bypass passage by the damping force adjustment valve, but also since the compression side damping valve is provided in the discharge passage and the suction side valve is provided in the suction passage, the pressure in the compression side chamber can be increased above the tank pressure during the contraction operation to generate a higher damping force than before.

Advantages of the Invention

[0014] According to the shock absorber of the present invention, it can be made small and lightweight, the manufacturing cost can be reduced, and the mountability on a vehicle can be improved.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0016] Hereinafter, the present invention will be described based on the embodiments shown in the drawings. As shown in FIG. 1, in one embodiment, a shock absorber D includes a cylinder 1, a cylindrical piston rod 2 movably inserted axially into the cylinder 1, a piston 3 connected to the piston rod 2 and movably inserted axially into the cylinder 1 and partitioning the inside of the cylinder 1 into an extension chamber R1 and a compression chamber R2, a cap 10 closing the compression chamber side end of the cylinder 1, a cylindrical inner rod 4 extending from the cap 10, inserted into the compression chamber R2, and slidably fitted into the piston rod 2, a main damping passage M that provides resistance to the flow of liquid flowing back and forth between the extension chamber R1 and the compression chamber R2, a bypass passage B that bypasses the main damping passage and communicates the extension chamber R1 and the compression chamber R2 through the inside of the piston rod 2 and the inside of the inner rod 4, and a damping force adjustment valve 21 provided in the bypass passage B.

[0017] And although not shown in the drawings, this shock absorber D is interposed between the vehicle body and the rear wheel in a saddle-type vehicle such as a motorcycle and is used to suppress the vibrations of the vehicle body and the rear wheel. Note that the shock absorber D may be used to suppress vibrations other than those of saddle-type vehicles.

[0018] Hereinafter, each part of the shock absorber D will be described in detail. As shown in FIG. 1, the cylinder 1 is cylindrical, with the upper end in FIG. 1 closed by a rod guide 17 and the lower end in FIG. 1 closed by a cap 10. A screw portion 1a is provided at a position slightly above the lower end of the cylinder 1 in FIG. 1, and the cap 10 is screwed to the screw portion 1a and attached to the lower end of the cylinder 1 in FIG. 1.

[0019] Also, the rod guide 17 fitted to the inner circumference of the upper end of the cylinder 1 in FIG. 1 is annular, and includes an annular seal ring 17a that closely adheres to the inner circumference of the cylinder 1 on the outer circumference, an annular seal ring 17b that slidably contacts the outer circumference of the piston rod 2 on the inner circumference, and an annular bush 17c. Further, the rod guide 17 is restricted from moving upward in FIG. 1 with respect to the cylinder 1 by a C-ring 24 attached to the inner circumference of the upper end of the cylinder 1 in FIG. 1.

[0020] In this way, the piston rod 2 movably inserted into the cylinder 1 is inserted through the seal ring 17b and the bush 17c of the rod guide 17 attached to the inner circumference of the cylinder 1. The rod guide 17 supports the piston rod 2 with the bush 17c and guides the axial movement of the piston rod 2 with respect to the cylinder 1, and seals the outer circumference of the piston rod 2 with the seal ring 17b. Further, a seal ring 17a is closely attached and sealed to the inner circumference of the cylinder 1 to prevent leakage of liquid from between the rod guide 17 and the cylinder 1. The upper end in FIG. 1, which is the tip of the piston rod 2, protrudes outward from the upper end in FIG. 1 of the cylinder 1 through the inner circumference of the rod guide 17.

[0021] The piston rod 2 is cylindrical, and has a small-diameter portion 2a provided at the lower end in FIG. 1 with an outer diameter smaller than that of the upper part and having a piston 3 attached to the outer circumference, a screw portion 2b provided on the outer circumference of the lower end in FIG. 1 of the small-diameter portion 2a, and a through-hole 2c penetrating the side portion above the small-diameter portion 2a in the radial direction in FIG. 1. Further, a bracket 6 connectable to the vehicle body in a saddle-type vehicle is attached to the upper end in FIG. 1 of the piston rod 2.

[0022] A piston 3 attached to the piston rod 2 is movably inserted into the cylinder 1 in the axial direction, and the inside of the cylinder 1 is partitioned by the piston 3 into an extension chamber R1 above the piston 3 and a pressure chamber R2 below the piston 3. The extension chamber R1 and the pressure chamber R2 are filled with a liquid such as hydraulic oil. In this embodiment, the liquid is hydraulic oil, but other liquids such as water and aqueous solutions may also be used. Since the through-hole 2c of the piston rod 2 opens above the small-diameter portion 2a to which the piston 3 is attached and faces the extension chamber R1 in FIG. 1, the inside of the piston rod 2 communicates with the extension chamber R1 through the through-hole 2c.

[0023] The piston 3 is annular and is mounted on the outer periphery of the small-diameter portion 2a of the piston rod 2, and includes an extension-side port 3a and a compression-side port 3b that respectively communicate with the extension-side chamber R1 and the compression-side chamber R2 in parallel. At the lower end of the piston 3 in FIG. 1, an extension-side main damping valve 13 that is annular and mounted on the outer periphery of the small-diameter portion 2a and opens and closes the extension-side port 3a is laminated. Also, at the upper end of the piston 3 in FIG. 1, a compression-side main damping valve 14 that is annular and mounted on the outer periphery of the small-diameter portion 2a and opens and closes the compression-side port 3b is laminated. The piston 3, the extension-side main damping valve 13, and the compression-side main damping valve 14 are fitted on the outer periphery of the small-diameter portion 2a of the piston rod 2 and are fixed to the piston rod 2 by a piston nut 15 screwed to the lower end of the small-diameter portion 2a.

[0024] In the shock absorber D of the present embodiment, the extension-side main damping valve 13 is formed by laminating a plurality of annular plates at the lower end of the piston 3 in FIG. 1. The inner peripheral side is fixed, and when the outer peripheral side is deflected by the pressure in the extension-side chamber R1, it is a laminated leaf valve that opens the extension-side port 3a. The extension-side main damping valve 13 can open and close the extension-side port 3a, and when the shock absorber D extends, it opens the valve to provide resistance to the flow of the liquid passing from the extension-side chamber R1 to the compression-side chamber R2 through the extension-side port 3a, and when the shock absorber D contracts, it closes the valve to block the extension-side port 3a. Note that the extension-side main damping valve 13 may be any damping valve that can provide resistance to the flow of the liquid from the extension-side chamber R1 to the compression-side chamber R2 and exert a damping force that prevents the extension of the shock absorber D when the shock absorber D extends. Therefore, it may be a damping valve other than the laminated leaf valve.

[0025] On the other hand, in the shock absorber D of the present embodiment, the compression-side main damping valve 14 is configured by stacking a plurality of annular plates on the upper end of the piston 3 in FIG. 1. The inner peripheral side is fixed, and when the outer peripheral side is deflected by the pressure in the compression-side chamber R2, it is a laminated leaf valve that opens the compression-side port 3b. The compression-side main damping valve 14 can open and close the compression-side port 3b, and when the shock absorber D contracts, it opens the valve to provide resistance to the flow of the liquid passing from the compression-side chamber R2 to the extension-side chamber R1 through the compression-side port 3b. When the shock absorber D extends, it closes the valve to block the compression-side port 3b. Note that the compression-side main damping valve 14 may be any damping valve that can provide resistance to the flow of the liquid from the compression-side chamber R2 to the extension-side chamber R1 and exert a damping force that prevents the contraction of the shock absorber D when the shock absorber D contracts. Therefore, it may be a damping valve other than the laminated leaf valve. Also, although not shown, an orifice is provided in parallel with the extension-side main damping valve 13 and the compression-side main damping valve 14. The orifice is formed, for example, by a notch provided in the annular plate constituting the extension-side main damping valve 13 and the compression-side main damping valve 14, or by an indentation provided in the valve seat of the piston 3 where the annular plate seats and disengages.

[0026] In this way, the extension-side port 3a and the compression-side port 3b in the piston 3 communicate the extension-side chamber R1 and the compression-side chamber R2. Also, with respect to the flow of the liquid passing through the extension-side port 3a and the compression-side port 3b and flowing back and forth between the extension-side chamber R1 and the compression-side chamber R2, when the extension-side main damping valve 13 and the compression-side main damping valve 14 are closed, resistance is provided by the orifice. When the extension-side main damping valve 13 and the compression-side main damping valve 14 are open, the extension-side main damping valve 13 provides resistance to the flow of the liquid passing through the extension-side port 3a, and the compression-side main damping valve 14 provides resistance to the flow of the liquid passing through the compression-side port 3b. In the present embodiment, these extension-side port 3a, compression-side port 3b, orifice, extension-side main damping valve 13, and compression-side main damping valve 14 constitute the main damping passage M that provides resistance to the flow of the liquid moving between the extension-side chamber R1 and the compression-side chamber R2. Note that the main damping passage M may be configured with only a single passage and a bidirectional valve such as an orifice or a choke provided in the passage that provides resistance to the flow of the liquid reciprocating between the extension-side chamber R1 and the compression-side chamber R2.

[0027] The cap 10 has a cylindrical portion 10a and a bottom portion 10b that closes the lower end of the cylindrical portion 10a, and is formed in a bottomed cylindrical shape. The lower end of the cylinder 1 is inserted into the cylindrical portion 10a, and the screw portion 10a1 on the inner periphery of the cylindrical portion 10a is screwed to the screw portion 1a on the outer periphery of the cylinder 1 and fixed to the cylinder 1.

[0028] More specifically, as shown in FIG. 1, the cylindrical portion 10a includes a screw portion 10a1 provided on the inner periphery of the upper end and an annular sealing groove 10a2 provided on the inner periphery and below the screw portion 10a1. A sealing ring 20 that adheres to the outer periphery of the cylinder 1 is accommodated in the sealing groove 10a2 provided on the inner periphery of the cylindrical portion 10a, and the space between the cap 10 and the cylinder 1 is sealed.

[0029] Subsequently, the bottom portion 10b of the cap 10 has a recess 10b1 at the center of the upper end in FIG. 1, and the lower end of the cylindrical inner rod 4 in FIG. 1 is inserted into the recess 10b1. A retaining ring 5 for preventing the inner rod 4 from coming out of the recess 10b1 is provided in the recess 10b1, and the inner rod 4 is held by the cap 10. Further, a sealing ring 16 that adheres to the outer periphery of the inner rod 4 is provided in the recess 10b1, and the space between the cap 10 and the inner rod 4 is sealed.

[0030] In this way, the inner rod 4 extends from the bottom 10b of the cap 10 and is inserted into the compression chamber R2, and is slidably inserted into the piston rod 2. More specifically, the outer diameter of the inner rod 4 is smaller than the inner diameter of the piston rod 2, and the inner rod 4 is slidably inserted into a cylindrical bush 2d mounted on the inner circumference of the lower end of the small-diameter portion 2a of the piston rod 2 in FIG. 1. Therefore, when the piston rod 2 is displaced relative to the cylinder 1, the piston rod 2 is also displaced relative to the inner rod 4 held by the cap 10. Further, the inner rod 4 is loosely fitted in the recess 10b1 and is held by the cap 10 by the retaining ring 5, but a slight radial runout at the upper end in FIG. 1 is allowed, and when inserted into the piston rod 2, it can smoothly move forward and backward in the piston rod 2 following the piston rod 2. The inside of the inner rod 4 communicates with the extension chamber R1 through the inside of the piston rod 2 and the through hole 2c, and forms a rod inner passage Pr together with the inside of the piston rod 2.

[0031] Note that the cross-sectional area of the annular gap between the inner circumference of the cylinder 1 and the outer circumference of the piston rod 2 is larger than the cross-sectional area of the inner rod 4, that is, the cross-sectional area of the cut surface formed by cutting the inner rod 4 horizontally.

[0032] Also, a bracket 10c is provided at the lower end of the bottom 10b of the cap 10 downward in FIG. 1, and the lower end of the shock absorber D can be connected to a swing arm that holds the rear wheel in a saddle-type vehicle via the bracket 10c. In the present embodiment, the piston rod 2 is described as being connected to the vehicle body of the saddle-type vehicle and the cap 10 is described as being connected to the rear wheel of the saddle-type vehicle. Conversely, the piston rod 2 may be connected to the rear wheel of the saddle-type vehicle and the cap 10 may be connected to the vehicle body of the saddle-type vehicle.

[0033] Furthermore, the cap 10 includes a tank holding portion 10d that extends radially from the side of the bottom portion 10b and holds a tank 18 disposed parallel to the cylindrical portion 10a. The tank 18 is cylindrical, and its lower end is integrally connected to the tank holding portion 10d, and houses a bladder 19 inside. The interior of the tank 18 is partitioned into a liquid chamber L filled with liquid by the bladder 19 and a gas chamber G filled with gas. In the gas chamber G, gas is enclosed such that at least the pressure inside the gas chamber G is equal to or greater than atmospheric pressure when the shock absorber D is fully extended. Note that the partition between the liquid chamber L and the gas chamber G inside the tank 18 may be formed by using an elastic partition such as a bladder or a diaphragm, or alternatively, by using a free piston.

[0034] In addition, in the present embodiment, as shown in FIG. 1, the cap 10 includes a passage Pc inside the cap that opens from the lower end in FIG. 1 of the recess 10b1 in the bottom portion 10b and leads to an end portion 10b2 facing the pressure side chamber R2 of the bottom portion 10b, and a discharge passage EP and a suction passage SP that open from the end portion 10b2 of the bottom portion 10b and lead to the liquid chamber L of the tank 18.

[0035] One end of the passage Pc inside the cap communicates with the extension side chamber R1 through the passage Pr inside the rod, and the other end communicates with the pressure side chamber R2, and together with the passage Pr inside the rod, forms a bypass path B that bypasses the main damping passage M and communicates the extension side chamber R1 and the pressure side chamber R2.

[0036] Furthermore, on the bottom portion 10b of the cap 10, a damping force adjustment valve 21, an extension side low-speed valve 22, and a compression side low-speed valve 23 disposed in the middle of the passage Pc inside the cap that constitutes a part of the bypass path B, a compression side damping valve 30 disposed in the middle of the discharge passage EP, and a suction check valve 31 as a suction side valve disposed in the middle of the suction passage SP are provided.

[0037] The damping force adjustment valve 21 is installed in series with the extension side low-speed valve 22 and the compression side low-speed valve 23 with respect to the bypass path B, and the extension side low-speed valve 22 and the compression side low-speed valve 23 are installed in parallel with each other with respect to the bypass path B.

[0038] In this embodiment, the damping force adjustment valve 21 includes a valve body 21a that can open and close a cap internal passage Pc forming part of the bypass passage B, a spring 21b that biases the valve body 21a to close, and a solenoid 21c that is attached to the side of the bottom 10b and can generate a thrust force to push the valve body 21a in the opening direction against the biasing force of the spring 21b. The degree of valve opening can be adjusted according to the amount of current supplied to the solenoid 21c, and it is an electromagnetic valve that closes when the current to the solenoid 21c is cut off. Note that although the damping force adjustment valve 21 is an electromagnetic valve whose valve opening degree can be adjusted in this way, it may also be an electromagnetic valve whose opening pressure can be adjusted, or a damping force adjustment valve that manually adjusts the valve opening degree or the opening pressure.

[0039] The extension-side low-speed valve 22 is a damping valve that opens to resist the flow of liquid from the extension-side chamber R1 to the compression-side chamber R2 and closes to block the passage for the flow of liquid from the compression-side chamber R2 to the extension-side chamber R1. Its opening pressure is lower than that of the extension-side main damping valve 13, and it becomes a valve that opens prior to the extension-side main damping valve 13 to generate a damping force when the extension speed of the shock absorber D is low.

[0040] The compression-side low-speed valve 23 is a damping valve that opens to resist the flow of liquid from the compression-side chamber R2 to the extension-side chamber R1 and closes to block the passage for the flow of liquid from the extension-side chamber R1 to the compression-side chamber R2. Its opening pressure is lower than that of the compression-side main damping valve 14, and it becomes a valve that opens prior to the compression-side main damping valve 14 to generate a damping force when the contraction speed of the shock absorber D is low.

[0041] In this embodiment, an extension-side low-speed valve 22 that allows only the flow of liquid from the extension-side chamber R1 to the compression-side chamber R2 and provides resistance to the flow of the liquid passing therethrough, and a compression-side low-speed valve 23 that allows only the flow of liquid from the compression-side chamber R2 to the extension-side chamber R1 and provides resistance to the flow of the liquid passing therethrough are provided in the cap internal passage Pc. These extension-side low-speed valve 22 and compression-side low-speed valve 23 are used as low-speed valves. However, a valve that can provide resistance to the flow of liquid reciprocating between the extension-side chamber R1 and the compression-side chamber R2 may be used as the low-speed valve.

[0042] The compression-side damping valve 30 is provided in the discharge passage EP. It is a damping valve that opens to provide resistance to the flow of liquid from the compression-side chamber R2 to the tank 18 and closes to block the discharge passage EP against the flow of liquid from the tank 18 to the compression-side chamber R2. The suction check valve 31 as the suction-side valve is provided in the suction passage SP. It opens to allow the flow of liquid from the tank 18 to the compression-side chamber R2 with almost no resistance to the flow of the liquid, and closes to block the suction passage SP against the flow of liquid from the compression-side chamber R2 to the tank 18. Thus, the suction-side valve of this embodiment is the suction check valve 31 provided in the discharge passage SP that allows only the flow of liquid from the tank 18 to the compression-side chamber R2. However, it may be a damping valve provided in the discharge passage SP that provides resistance to the flow of liquid from the tank 18 to the compression-side chamber R2.

[0043] The shock absorber D of this embodiment is configured as described above, and the operation of the shock absorber D will be described below. When the shock absorber D extends, the piston rod 2 withdraws from the cylinder 1 and the piston 3 compresses the extension chamber R1. Then, the liquid in the extension chamber R1 passes through an orifice (not shown) in the main damping passage M and the extension-side main damping valve 13 in the main damping passage M, or passes through the bypass passage B partially formed by the piston rod 2 and the inner rod 4 and then passes through the extension-side low-speed valve 22 to move to the compression chamber R2. Further, since the amount of liquid insufficient in the cylinder 1 is the difference between the displacement volume of the piston rod 2 withdrawn from the cylinder 1 and the displacement volume of the inner rod 4 withdrawn from the piston rod 2, the insufficient liquid is supplied into the cylinder 1 from the tank 18 through the suction passage SP when the suction check valve 31 opens. As described above, since the cross-sectional area of the annular gap between the inner periphery of the cylinder 1 and the outer periphery of the piston rod 2 is larger than the cross-sectional area of the inner rod 4, when the shock absorber D extends, the liquid always moves from the extension chamber R1 to the compression chamber R2 through the main damping passage M or the bypass passage B.

[0044] Regarding the flow of the liquid from the extension chamber R1 to the compression chamber R2, resistance is applied by the main damping passage M or the extension-side low-speed valve 22. Due to this resistance, the shock absorber D generates a damping force that hinders the extension operation. Regarding the resistance applied when the liquid passes through the main damping passage M, when the extension speed of the shock absorber D is in the low-speed range, the extension-side main damping valve 13 does not open and resistance is applied to the flow of the liquid by an orifice (not shown). When the extension speed of the shock absorber D is in the high-speed range, the extension-side main damping valve 13 opens and resistance is applied to the flow of the liquid by the extension-side main damping valve 13. Then, when the energization amount to the damping force adjustment valve 21 is changed, the distribution ratio of the liquid passing through the main damping passage M and the extension-side low-speed valve 22 during the extension operation of the shock absorber D changes.

[0045] Specifically, when the shock absorber D extends, the liquid passes through the main damping passage M and the extension-side low-speed valve 22 when the damping force adjustment valve 21 opens. However, when the damping force adjustment valve 21 closes, the bypass passage B is blocked, so the liquid cannot pass through the extension-side low-speed valve 22 and moves from the extension-side chamber R1 to the compression-side chamber R2 only through the main damping passage M. Also, when a current is supplied to the damping force adjustment valve 21 to open it and the amount of current supplied is increased, the opening degree of the damping force adjustment valve 21 increases and the flow rate of the liquid passing through the bypass passage B increases. Therefore, the proportion of the liquid passing through the extension-side low-speed valve 22 increases, and the proportion of the liquid passing through the main damping passage M decreases. Thus, the damping force characteristic generated by the shock absorber D during the extension operation when the extension speed is in the low-speed range can be changed, as shown in FIG. 2, by adjusting the amount of current supplied to the damping force adjustment valve 21, from the soft characteristic mainly generated by the extension-side low-speed valve 22 shown by the dashed line in FIG. 2 to the hard characteristic mainly generated by the main damping passage M shown by the solid line in FIG. 2. Further, when the extension speed is in the high-speed range during the extension operation, the extension-side main damping valve 13 fully opens regardless of the opening degree of the damping force adjustment valve 21, and the liquid preferentially passes through the main damping passage M. Therefore, the shock absorber D generates a damping force by the extension-side main damping valve 13. When the suction-side valve is a damping valve instead of the suction check valve 31, when the liquid moves from the tank 18 into the cylinder 1 through the suction passage SP, resistance is applied to the flow of the liquid to reduce the pressure in the compression-side chamber R2, and a higher damping force can be generated.

[0046] On the contrary, during the contraction operation of the shock absorber D, the piston rod 2 penetrates into the cylinder 1 and the piston 3 compresses the pressure side chamber R2. Then, the liquid in the pressure side chamber R2 passes through an orifice (not shown) in the main damping passage M and the pressure side main damping valve 14 in the main damping passage M, or passes through the bypass passage B partially formed by the piston rod 2 and the inner rod 4, and then moves to the extension side chamber R1 through the pressure side low-speed valve 23. Also, since the amount of liquid in the cylinder 1 becomes excessive by subtracting the displacement volume of the inner rod 4 entering the piston rod 2 from the displacement volume of the piston rod 2 entering the cylinder 1, the excessive liquid passes through the pressure side damping valve 30 from the pressure side chamber R2 and is discharged from the pressure side chamber R2 into the tank 18. As described above, since the cross-sectional area of the annular gap between the inner periphery of the cylinder 1 and the outer periphery of the piston rod 2 is larger than the cross-sectional area of the inner rod 4, when the shock absorber D contracts, the liquid always becomes excessive in the cylinder 1 and moves from the cylinder 1 to the tank 18.

[0047] Regarding the flow of the liquid from the pressure side chamber R2 to the extension side chamber R1, resistance is applied by the main damping passage M or the pressure side low-speed valve 23. Regarding the flow of the liquid from the pressure side chamber R2 to the tank 18, resistance is applied by the pressure side damping valve 30, and a pressure side damping force is generated due to each of the above resistances. Regarding the resistance applied when the liquid passes through the main damping passage M, when the contraction speed of the shock absorber D is in the low-speed range, the pressure side main damping valve 14 does not open and resistance is applied to the liquid flow by an orifice (not shown). When the contraction speed of the shock absorber D is in the high-speed range, the pressure side main damping valve 14 opens and resistance is applied to the liquid flow by the pressure side main damping valve 14. Then, when the energization amount to the damping force adjustment valve 21 is changed, the distribution ratio of the liquid passing through the main damping passage M and the pressure side low-speed valve 23 during the contraction operation of the shock absorber D changes.

[0048] Specifically, when the shock absorber D contracts, when the damping force adjustment valve 21 opens, the liquid passes through the main damping passage M and the pressure-side low-speed valve 23. However, when the damping force adjustment valve 21 closes, the bypass passage B is blocked, so the liquid cannot pass through the pressure-side low-speed valve 23 and moves from the pressure-side chamber R2 to the extension-side chamber R1 only through the main damping passage M. Also, when a current is supplied to the damping force adjustment valve 21 to open it and the amount of current supplied is increased, the opening degree of the damping force adjustment valve 21 increases and the flow rate of the liquid passing through the bypass passage B increases. Therefore, the proportion of the liquid passing through the pressure-side low-speed valve 23 increases, and the proportion of the liquid passing through the main damping passage M decreases. Thus, when the contraction operation is in the low-speed range, the damping force characteristic generated by the shock absorber D, as shown in FIG. 2, can be changed within the range from the soft characteristic of applying resistance to the liquid flowing from the pressure-side chamber R2 to the extension-side chamber R1 by the pressure-side low-speed valve 23 shown by the broken line in FIG. 2 to the hard characteristic of applying resistance by the main damping passage M shown by the solid line in FIG. 2 by adjusting the amount of current supplied to the damping force adjustment valve 21. Also, when the contraction operation is in the high-speed range, regardless of the opening degree of the damping force adjustment valve 21, the pressure-side main damping valve 14 opens wide, and the liquid flowing from the pressure-side chamber R2 to the extension-side chamber R1 preferentially passes through the pressure-side main damping valve 14. Therefore, the shock absorber D generates a damping force by the pressure-side main damping valve 14. Furthermore, during the contraction operation of the shock absorber D, the excessive liquid in the cylinder 1 passes through the pressure-side damping valve 30 and goes from the pressure-side chamber R2 to the tank 18. Therefore, the pressure of the pressure-side chamber R2 can be increased to a pressure higher than the tank pressure by the pressure-side damping valve 30, and the shock absorber D can generate a higher damping force on the pressure side than before.

[0049] Note that in the shock absorber D of this embodiment, the extension-side low-speed valve 22 and the pressure-side low-speed valve 23 are provided as low-speed valves. However, it is also possible to abolish the extension-side low-speed valve 22 and the pressure-side low-speed valve 23 and adjust the damping force by changing the opening degree of the damping force adjustment valve 21.

[0050] As described above, the shock absorber D of the present embodiment includes a cylinder 1, a cylindrical piston rod 2 that is inserted into the cylinder 1 so as to be axially movable, a piston 3 that is connected to the piston rod 2 and is inserted into the cylinder 1 so as to be axially movable and partitions the inside of the cylinder 1 into an extension chamber R1 and a compression chamber R2, a cap 10 that closes the compression chamber side end of the cylinder 1, a cylindrical inner rod 4 that extends from the cap 10 and is inserted into the compression chamber R2 and slidably fits into the piston rod 2, a main damping passage M that provides resistance to the flow of liquid flowing back and forth between the extension chamber R1 and the compression chamber R2, a bypass passage B that bypasses the main damping passage and communicates the extension chamber R1 and the compression chamber R2 through the inside of the piston rod 2 and the inside of the inner rod 4, and a damping force adjustment valve 21 provided in the bypass passage B.

[0051] In the shock absorber D configured as described above, the bypass passage B bypasses the main damping passage M and communicates the extension chamber R1 and the compression chamber R2 through the inside of the piston rod 2 and the inside of the inner rod 4 inserted into the piston rod 2. Since the bypass passage B is provided inside the cylinder 1, a large-diameter outer shell covering the cylinder 1 is not required for forming the bypass passage B. Therefore, according to the shock absorber D of the present embodiment, since the outer shell is not required, it can be made small and lightweight, the manufacturing cost can be reduced, and it can be mounted on a vehicle with a limited mounting space, so the mountability on the vehicle can also be improved.

[0052] Further, in the shock absorber D of the present embodiment, the cross-sectional area of the annular gap between the inner periphery of the cylinder 1 and the outer periphery of the piston rod 2 is larger than the cross-sectional area of the inner rod 4. According to the shock absorber D configured as described above, during the extension operation, the liquid moves from the extension chamber R1 to the compression chamber R2, and during the contraction operation, the liquid moves from the compression chamber R2 to the extension chamber R1. Therefore, the flow of the liquid is the same as that of a conventional shock absorber, and the setting of the damping force characteristics is also easy.

[0053] Furthermore, the shock absorber D of the present embodiment includes a tank 18 for storing a liquid, a discharge passage EP that communicates the pressure chamber R2 and the tank 18, a suction passage SP that communicates the tank 18 and the pressure chamber R2, a pressure-side damping valve 30 provided in the discharge passage EP that provides resistance to the flow of the liquid from the pressure chamber R2 to the tank 18, and a suction check valve (suction-side valve) 31 provided in the suction passage SP that allows the flow of the liquid from the tank 18 to the pressure chamber R2.

[0054] According to the shock absorber D configured in this way, not only can the damping force be adjusted up and down while securing the damping force adjustment range by adjusting the flow rate distribution ratio between the main damping passage M and the bypass passage B by the damping force adjustment valve 21, but also the pressure-side damping valve 30 is provided in the discharge passage EP and the suction check valve (suction-side valve) 31 is provided in the suction passage SP. Therefore, during the contraction operation, the pressure in the pressure chamber R2 can be increased above the tank pressure to generate a higher damping force than before. As described above, according to the shock absorber D of the present embodiment, a high damping force can be exerted during the contraction operation while securing the damping force adjustment range.

[0055] Also, in the shock absorber D of the present embodiment, an extension-side low-speed valve 22 and a pressure-side low-speed valve 23 that are provided in series with the damping force adjustment valve 21 in the bypass passage B and provide resistance to the flow of the liquid moving between the extension chamber R1 and the pressure chamber R2 are provided. According to the shock absorber D configured in this way, by opening the damping force adjustment valve 21 to activate the extension-side low-speed valve 22 and the pressure-side low-speed valve 23 in the bypass passage B, the damping force in the low-speed range of the expansion and contraction speed can be adjusted up and down, and a damping force suitable for traveling on a good road with few unevennesses where the saddle-riding type vehicle does not vibrate at high speeds can be generated.

[0056] As described above, the preferred embodiments of the present invention have been described in detail, but modifications, deformations, and changes are possible without departing from the scope of the claims.

Explanation of Reference Numerals

[0057] 1... cylinder, 2... piston rod, 3... piston, 4... inner rod, 10... cap, 18... tank, 30... compression side damping valve, 31... suction check valve (suction side valve), B... bypass passage, D... shock absorber, EP... discharge passage, M... main damping passage, R1... extension side chamber, R2... compression side chamber, SP... discharge passage

Claims

1. A cylinder, a cylindrical piston rod inserted axially movably into the cylinder, a piston connected to the piston rod and inserted axially movably into the cylinder, partitioning the inside of the cylinder into an extension chamber and a compression chamber, a cap closing the compression chamber side end of the cylinder, a cylindrical inner rod extending from the cap, inserted through the compression chamber, and slidably fitted into the piston rod, a main damping passage that provides resistance to the flow of liquid flowing back and forth between the extension chamber and the compression chamber, a bypass passage that bypasses the main damping passage and communicates the extension chamber and the compression chamber through the inside of the piston rod and the inside of the inner rod, and a damping force adjustment valve provided in the bypass passage. A shock absorber characterized by the above.

2. The cross-sectional area of the annular gap between the inner circumference of the cylinder and the outer circumference of the piston rod is larger than the cross-sectional area of the inner rod. The shock absorber according to claim 1, characterized by the above.

3. A tank for storing liquid, a discharge passage communicating the compression chamber and the tank, a suction passage communicating the tank and the compression chamber, a compression side damping valve provided in the discharge passage to provide resistance to the flow of liquid from the compression chamber to the tank, and a suction side valve provided in the suction passage to allow the flow of liquid from the tank to the compression chamber. The shock absorber according to claim 1 or 2, characterized by the above.

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