Fluid pressure shock absorber

Abstract

To improve the mountability of an attenuation valve capable of changing attenuation characteristics.SOLUTION: A hydraulic shock absorber 100 mounted on a vehicle is equipped with a cylinder tube 10, a rod 12 inserted in the cylinder tube 10 so as to move forward / backward, a piston 14 that is coupled to the rod 12 and divides the inside of the cylinder tube 10 into a bottom side chamber 1 and a rod side chamber 2, an attenuation valve 20 that adds resistance to a flow of a working fluid between the bottom side chamber 1 and the rod side chamber 2, and can change attenuation characteristics according to pilot pressure, and a solenoid valve 30 that switches the supply and interception of the pilot pressure to the attenuation valve 20. As the pilot pressure, the working fluid of the bottom side chamber 1 or the rod side chamber 2 is used.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In the fluid pressure shock absorber described in Patent Document 1, the piston rod has a rod portion extending to the outside of the cylinder, and a piston connected to the end of the rod portion and slidably moving within the cylinder, dividing the interior of the cylinder into a bottom-side chamber and a rod-side chamber. The rod portion has an internal rod space formed inside the rod portion and communicating with the bottom-side chamber of the cylinder, a first communication passage connecting the internal rod space with the rod-side chamber of the cylinder, and an orifice plug provided in the first communication passage and generating a damping force. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-206374 Summary of the Invention [Problem to be solved by the invention]

[0004] In the fluid pressure shock absorber described in Patent Document 1, when a damping valve capable of changing the damping characteristics is installed, it is possible to consider using a solenoid valve as the damping valve. However, when the working fluid passing through the damping valve is high-pressure and has a large flow rate, the damping valve becomes large, which makes it difficult to install the damping valve.

[0005] The present invention has been made in view of the above problems, and has an object to improve the mountability of a damping valve capable of changing damping characteristics. [Means for solving the problem]

[0006] The present invention is a fluid pressure shock absorber mounted on a vehicle, comprising: a cylinder tube; a rod inserted into the cylinder tube so as to be able to move back and forth; a piston connected to the rod and dividing the inside of the cylinder tube into a bottom side chamber and a rod side chamber; a damping valve that applies resistance to the flow of working fluid between the bottom side chamber and the rod side chamber and whose damping characteristics can be changed according to pilot pressure; and a solenoid valve that switches between supplying and blocking pilot pressure to the damping valve, wherein the working fluid in the bottom side chamber or the rod side chamber is used as the pilot pressure.

[0007] In this invention, the damping characteristics of the damping valve can be changed using the working fluid in the bottom-side chamber or the rod-side chamber as the pilot pressure, and the supply and cut-off of the pilot pressure is switched by the solenoid valve, so the damping valve does not become large, thereby improving the mountability of the damping valve capable of changing the damping force.

[0008] The present invention is also characterized in that the working fluid in the bottom-side chamber is used as the pilot pressure, and pressurized gas is sealed in the bottom-side chamber.

[0009] In this invention, since pressurized gas is sealed in the bottom side chamber, the bottom side chamber does not become negative pressure while the fluid pressure buffer is in operation, and therefore the damping valve can operate stably.

[0010] The present invention is also characterized in that a plurality of damping valves are provided in series, a plurality of solenoid valves are provided in parallel, and the plurality of solenoid valves switch between supplying and blocking pilot pressure to the plurality of damping valves, respectively.

[0011] The present invention is also characterized in that the damping valves include a first damping valve and a second damping valve that are arranged in parallel to each other and provide resistance to the flow of working fluid, and the first damping valve provides resistance only to the flow of working fluid from one of the bottom side chamber and the rod side chamber to the other.

[0012] These inventions make it possible to achieve optimal damping characteristics depending on the state of the vehicle.

[0013] The present invention is also characterized in that the fluid pressure shock absorber further comprises a pilot passage provided with a solenoid valve and guiding the working fluid in the bottom side chamber or the rod side chamber to the damping valve as pilot pressure, and a check valve guiding the pilot pressure from the downstream side of the damping valve in the pilot passage to the bottom side chamber or the rod side chamber.

[0014] In this invention, when the solenoid valve cuts off the supply of pilot pressure, the residual pressure in the pilot passage is released through the check valve, so that the damping valve can be switched smoothly.

[0015] In addition, the present invention is characterized in that the rod has a rod main body connected to the piston and slidably supported on the cylinder tube, a head portion exposed to the outside of the cylinder tube, and a rod internal space formed inside the rod main body, the rod internal space having a first space communicating with the bottom side chamber and a second space communicating with the rod side chamber, the damping valve and the solenoid valve are provided in the head portion, and the pilot pressure is supplied through the first space or the second space.

[0016] In this invention, it is possible to prevent gas from being mixed into the pilot fluid. [Effects of the Invention]

[0017] According to the present invention, it is possible to improve the mountability of a damping valve capable of changing the damping force. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a hydraulic circuit diagram of a hydraulic shock absorber according to an embodiment of the present invention. [Figure 2] 1 is a cross-sectional view of a fluid pressure shock absorber according to an embodiment of the present invention. [Figure 3] FIG. 10 is a fluid pressure circuit diagram of a fluid pressure shock absorber according to a modified example of the embodiment of the present invention. [Figure 4] FIG. 10 is a fluid pressure circuit diagram of a fluid pressure shock absorber according to a modified example of the embodiment of the present invention. [Figure 5]FIG. 10 is a fluid pressure circuit diagram of a fluid pressure shock absorber according to a modified example of the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, a fluid pressure shock absorber according to an embodiment of the present invention will be described with reference to the drawings.

[0020] The following describes a case where the fluid pressure shock absorber is a hydraulic shock absorber 100 mounted on a vehicle. The hydraulic shock absorber 100 is a device that is interposed, for example, between the body and axle of a vehicle, and generates a damping force to suppress vibration of the body.

[0021] 1, the hydraulic shock absorber 100 includes a cylindrical cylinder tube 10, a rod 12 that is inserted into the cylinder tube 10 so as to be able to move back and forth and that extends to the outside of the cylinder tube 10, and a piston 14 that is connected to the tip of the rod 12 and is able to slide along the inner circumferential surface of the cylinder tube 10. The hydraulic shock absorber 100 is mounted on a vehicle with the cylinder tube 10 on the upper side and the rod 12 on the lower side.

[0022] The interior of the cylinder tube 10 is divided into a bottom-side chamber 1 and a rod-side chamber 2 by the piston 14. Hydraulic oil is sealed in each of the bottom-side chamber 1 and the rod-side chamber 2 as a working fluid. Pressurized gas G is sealed in the bottom-side chamber 1 together with the hydraulic oil to compensate for volume changes in the cylinder tube 10 caused by the rod 12 moving in and out of the cylinder tube 10 and to provide a spring action. In this way, the hydraulic shock absorber 100 functions as an air suspension that can support the vehicle body by the spring action of the gas G. In this case, the hydraulic shock absorber 100 can generate a damping force and support the vehicle body without the need for a separate spring to support the vehicle body.

[0023] However, this is not limiting, and gas does not have to be sealed inside the cylinder tube 10. Also, a free piston may be provided movably inside the bottom-side chamber 1, separating the bottom-side chamber 1 into a liquid chamber in which hydraulic oil is sealed and an air chamber in which gas G is sealed. Also, an accumulator connected to the bottom-side chamber 1 may be provided outside the cylinder tube 10, and an air chamber may be provided in the accumulator.

[0024] The bottom-side chamber 1 and the rod-side chamber 2 are connected through a flow path 3. The hydraulic shock absorber 100 is provided with a damping valve 20 that is provided in the flow path 3 and applies resistance to the flow of hydraulic oil between the rod-side chamber 2 and the bottom-side chamber 1 to generate a damping force.

[0025] The flow path 3 is branched midway and has a first flow path 21 and a second flow path 22 which are parallel to each other. The damping valve 20 has a first damping valve 20A which is provided in the first flow path 21 and which applies resistance to the flow of hydraulic oil, and a second damping valve 20B which is provided in the second flow path 22 and which applies resistance to the flow of hydraulic oil. The first damping valve 20A and the second damping valve 20B are provided in parallel to each other.

[0026] The first flow path 21 is provided with a check valve 23 that allows hydraulic oil to flow only from the bottom-side chamber 1 to the rod-side chamber 2. Therefore, the first damping valve 20A applies resistance only to the flow of hydraulic oil from the bottom-side chamber 1 to the rod-side chamber 2. In this embodiment, the first damping valve 20A is, for example, a fixed orifice.

[0027] The second damping valve 20B applies resistance to the flow of hydraulic oil in both directions between the bottom-side chamber 1 and the rod-side chamber 2. The position of the second damping valve 20B changes in response to the pilot pressure, and the resistance applied to the flow of hydraulic oil passing through it differs in each position. In other words, the damping characteristics of the second damping valve 20B can be changed in response to the pilot pressure.

[0028] In this embodiment, the second damping valve 20B has two positions: a first throttling position 25A that applies a predetermined resistance to the flow of hydraulic oil passing through, and a second throttling position 25B that applies a resistance of a magnitude different from the resistance applied by the first throttling position 25A. In other words, the first throttling position 25A and the second throttling position 25B have different pressure loss characteristics with respect to the flow of hydraulic oil passing through.

[0029] The second damping valve 20B has a valve element (not shown) that switches its position, a spring 26 that serves as a biasing member that biases the valve element, and a pilot chamber 27 to which pilot pressure is supplied. The valve element of the second damping valve 20B is biased by the spring 26 so as to be in a first throttle position 25A. When pilot pressure is introduced into the pilot chamber 27, the valve element of the second damping valve 20B moves against the biasing force of the spring 26, and the second damping valve 20B is switched to the second throttle position 25B. When the supply of pilot pressure is cut off, the second damping valve 20B is switched to the first throttle position 25A by the biasing force of the spring 26.

[0030] When the hydraulic shock absorber 100 is contracted, the pressure in the bottom-side chamber 1 rises, and some of the hydraulic oil in the bottom-side chamber 1 opens the check valve 23 and passes through the first damping valve 20A to be led to the rod-side chamber 2, and the remainder passes through the second damping valve 20B to be led to the rod-side chamber 2. In this way, when the hydraulic shock absorber 100 is contracted, the hydraulic oil in the bottom-side chamber 1 passes through both the first damping valve 20A and the second damping valve 20B and is led to the rod-side chamber 2. For this reason, when the hydraulic shock absorber 100 is contracted, it generates a damping force according to the flow path resistance exerted as a whole by the first damping valve 20A and the second damping valve 20B.

[0031] When the hydraulic shock absorber 100 is extended, the pressure in the rod-side chamber 2 increases, and the hydraulic oil in the rod-side chamber 2 is guided to the bottom-side chamber 1 through the second damping valve 20B. On the other hand, the check valve 23 closes due to the increase in pressure in the rod-side chamber 2, and the hydraulic oil in the rod-side chamber 2 is not guided to the bottom-side chamber 1 through the first damping valve 20A. Therefore, during extension, the hydraulic shock absorber 100 generates a damping force corresponding to the flow path resistance exerted by the second damping valve 20B. Therefore, during compression, the hydraulic shock absorber 100 generates a larger damping force during extension than during compression, since the hydraulic oil is allowed to flow from the bottom-side chamber 1 to the rod-side chamber 2 through the first damping valve 20A. As a result, when the vehicle runs over a bump in the road surface, the hydraulic shock absorber 100 performs a relatively smooth compression operation and then generates a large damping force during extension, effectively damping vibrations input to the vehicle body from the road surface.

[0032] The first flow path 21, the first damping valve 20A, and the check valve 23 are not essential components, and the damping force may be generated only by the second damping valve 20B.

[0033] The hydraulic shock absorber 100 includes a solenoid valve 30 that switches between supplying and blocking pilot pressure to the second damping valve 20B. The solenoid valve 30 is provided in a pilot passage 33. The pilot passage 33 is provided by branching off from the flow path 3, and connects the bottom-side chamber 1 with the pilot chamber 27 of the second damping valve 20B. The pilot passage 33 may be configured to guide the hydraulic oil in the bottom-side chamber 1 as pilot pressure to the pilot chamber 27 of the second damping valve 20B, and may be directly connected to the bottom-side chamber 1, for example.

[0034] The solenoid valve 30 has two positions: a cutoff position 30A for cutting off the supply of pilot pressure, and a supply position 30B for supplying pilot pressure.

[0035] The operation of the solenoid valve 30 is controlled by an electrical signal input from a controller 35. The solenoid valve 30 has a valve body (not shown) that switches positions, a spring 31 as a biasing member that biases the valve body, and a solenoid 32 that moves the valve body against the biasing force of the spring 31 when current is applied.

[0036] The solenoid valve 30 has a valve element biased by a spring 31 so as to move to a shutoff position 30A. When the solenoid 32 is excited by the passage of current, the valve element moves against the biasing force of the spring 31, and the solenoid valve 30 switches to a supply position 30B. When the passage of current to the solenoid 32 is cut off, the solenoid valve 30 switches to the shutoff position 30A by the biasing force of the spring 31.

[0037] The vehicle is provided with a detector 34 that detects the weight of a load (load weight) loaded on the bed, and a signal detected by the detector 34 is output to a controller 35. When the load weight is less than a predetermined weight, the controller 35 cuts off the power to the solenoid 32 of the solenoid valve 30 based on the signal from the detector 34. On the other hand, when the load weight is equal to or greater than the predetermined weight, the controller 35 applies power to the solenoid 32 of the solenoid valve 30 based on the signal from the detector 34. In this way, when the load weight of the vehicle is light, the solenoid valve 30 is in the shutoff position 30A, the supply of pilot pressure to the second damping valve 20B is cut off, and the second damping valve 20B is in the first throttling position 25A. On the other hand, when the load weight of the vehicle is heavy, the solenoid valve 30 is in the supply position 30B, pilot pressure is supplied to the second damping valve 20B, and the second damping valve 20B is in the second throttling position 25B.

[0038] In a vehicle with a large maximum load weight, such as a dump truck, the weight of the entire vehicle including the load differs greatly between an empty state and a loaded state, and therefore the energy damped by the hydraulic shock absorber 100 also differs greatly. However, in this embodiment, the solenoid valve 30 changes the damping characteristics of the second damping valve 20B in accordance with the load weight of the vehicle, so that the hydraulic shock absorber 100 can exhibit optimal damping characteristics in accordance with the load weight of the vehicle.

[0039] In this embodiment, the hydraulic oil in the bottom-side chamber 1 is used as the pilot pressure for switching the position of the second damping valve 20B. Alternatively, the hydraulic oil in the rod-side chamber 2 may be used as the pilot pressure. However, when a wheel lands on the bottom of a depression in the road surface or when a wheel runs over a protrusion in the road surface while the vehicle is traveling, the hydraulic shock absorber 100 temporarily and suddenly contracts, which may cause the rod-side chamber 2 to become negative pressure. In contrast, the bottom-side chamber 1 supports the weight of the vehicle body and contains pressurized gas G, so that the pressure does not become negative while the hydraulic shock absorber 100 is operating. Therefore, it is preferable to use the hydraulic oil in the bottom-side chamber 1 as the pilot pressure.

[0040] As described above, in this embodiment, the solenoid valve 30 is used to switch between supplying and blocking pilot pressure to the pilot-driven second damping valve 20B, which has variable damping characteristics. In a large vehicle such as a dump truck, the hydraulic shock absorber 100 installed thereon is also large, so the flow rate of hydraulic oil passing through the second damping valve 20B is large. Furthermore, in a vehicle with a large maximum load weight, such as a dump truck, the overall vehicle weight is large, so the pressure of the hydraulic oil in the hydraulic shock absorber 100 that supports that weight is high. Furthermore, the hydraulic shock absorber 100 has gas G sealed in the cylinder tube 10, so that it also functions as an air suspension, and therefore the pressure of the hydraulic oil in the cylinder tube 10 is high. Thus, when the hydraulic shock absorber 100 is installed in a large vehicle such as a dump truck, the second damping valve 20B needs to be a valve that can switch the flow of high-pressure, high-flow hydraulic oil. If the second damping valve 20B itself is a solenoid valve, a large solenoid thrust is required to switch the position of the second damping valve 20B, which results in the solenoid provided in the second damping valve 20B becoming larger. Therefore, the second damping valve 20B is difficult to install in the hydraulic shock absorber 100.

[0041] In contrast, in this embodiment, the second damping valve 20B is of a pilot-driven type, and therefore does not become larger. Furthermore, the supply and cut-off of pilot pressure to the second damping valve 20B is switched by the solenoid valve 30, but the solenoid valve 30 is provided in a pilot passage 33, and the flow rate of pilot fluid flowing through the pilot passage 33 is small. In this way, the solenoid valve 30 is sufficient as long as it is a valve that can switch the flow of hydraulic oil at high pressure and low flow rate, and does not require a large solenoid thrust, so it can be made smaller. Therefore, the mountability of the second damping valve 20B in the hydraulic shock absorber 100 is improved, and ultimately the hydraulic shock absorber 100 can be made smaller.

[0042] Next, the structure of the hydraulic shock absorber 100 and an example of mounting the damping valve 20 and the solenoid valve 30 on the hydraulic shock absorber 100 will be described with reference to Fig. 2. Fig. 2 is a cross-sectional view of the hydraulic shock absorber 100.

[0043] The cylinder tube 10 is cylindrical with a bottom, and has a cylinder head 11 at its open end through which a rod 12 is slidably inserted. A mounting portion 10a for mounting the hydraulic shock absorber 100 to a vehicle is provided at the closed end of the cylinder tube 10 (the end opposite to the cylinder head 11).

[0044] The rod 12 has a rod body 51 connected to the piston 14 and slidably supported in the cylinder head 11 of the cylinder tube 10, and a head portion 52 exposed to the outside of the cylinder tube 10.

[0045] The rod body 51 has an internal rod space 40 that opens to the end face on the piston 14 side. The end of the rod body 51 is connected to the piston 14 by a bolt (not shown).

[0046] The head portion 52 is formed with a larger diameter than the rod body 51, and is always exposed to the outside of the cylinder tube 10 regardless of the stroke position of the hydraulic shock absorber 100. In other words, the head portion 52 is a portion of the rod 12 that does not slide relative to the cylinder head 11. The head portion 52 is formed, for example, separately from the rod body 51, and is connected to the end of the rod body 51 by welding or the like. Note that the rod body 51 and the head portion 52 may be formed integrally.

[0047] The head portion 52 is provided with a stopper portion 52a that determines the stroke end when the hydraulic shock absorber 100 is contracted, and a mounting portion 52b for mounting the hydraulic shock absorber 100 to a vehicle. The stopper portion 52a is provided with an annular cushion ring 53 that prevents collision between the cylinder head 11 and the rod 12 at the stroke end when the hydraulic shock absorber 100 is contracted.

[0048] A cylindrical pipe 43 is provided in the rod internal space 40. One end of the pipe 43 is inserted into an insertion hole 52c formed in the head portion 52, and the other end is inserted into an insertion hole 14a formed in the piston 14. In this manner, the pipe 43 is sandwiched between the head portion 52 and the piston 14.

[0049] By providing the pipe 43 in the rod intra-space 40, the rod intra-space 40 is partitioned into a first space 41, which is a hollow portion of the pipe 43, and an annular second space 42 partitioned by the outer circumferential surface of the pipe 43 and the inner circumferential surface of the rod main body 51. The first space 41 communicates with the bottom-side chamber 1 through a through-hole 14b formed in the piston 14. The second space 42 communicates with the rod-side chamber 2 through a plurality of through-holes 51a formed in the rod main body 51 of the rod 12. In this way, the rod intra-space 40 has the first space 41 communicating with the bottom-side chamber 1 and the second space 42 communicating with the rod-side chamber 2. The first space 41 and the second space 42 constitute a part of the flow path 3 connecting the bottom-side chamber 1 and the rod-side chamber 2.

[0050] The flow path 3, the first damping valve 20A, the second damping valve 20B, and the solenoid valve 30 are provided in the head portion 52 of the rod 12. A pilot passage 33 that introduces pilot pressure for driving the second damping valve 20B is also provided in the head portion 52. The pilot pressure is introduced from the bottom-side chamber 1 through the first space 41 and the pilot passage 33 to the second damping valve 20B. In this manner, the pilot pressure is introduced through the first space 41 and the pilot passage 33 provided in the head portion 52, and is extracted from the vertically below side of the gas G that accumulates on the vertically above side of the hydraulic shock absorber 100. This prevents the gas G from mixing with the pilot fluid, stabilizing the operation of the second damping valve 20B. In this manner, even if the air chamber in which the gas G is sealed is not partitioned by a free piston, extracting the pilot pressure from the vertically below side of the gas G prevents the gas G from mixing with the pilot fluid.

[0051] When the hydraulic oil in the rod side chamber 2 is used as the pilot pressure, the pilot pressure may be introduced into the pilot chamber 27 of the second damping valve 20B through a pilot passage provided in the second space 42 and the head portion 52.

[0052] According to the above embodiment, the following effects are achieved.

[0053] The damping characteristics of the second damping valve 20B can be changed using the hydraulic oil in the bottom-side chamber 1 as the pilot pressure, and the supply and cut-off of the pilot pressure is switched by the solenoid valve 30, so the second damping valve 20B does not become large. Therefore, it is possible to improve the mountability of the second damping valve 20B, which is capable of changing the damping force.

[0054] Modifications of the above embodiment will be described below. The following modifications are also within the scope of the present invention, and it is possible to combine the following modifications with the configuration of the above embodiment, or to combine the following modifications with each other.

[0055] (1) In the hydraulic shock absorber 101 shown in FIG. 3, a plurality of second damping valves 20B are provided in series in the second flow path 22, and a plurality of solenoid valves 30 are provided in parallel, and the plurality of solenoid valves 30 switch between supplying and blocking pilot pressure to the plurality of second damping valves 20B. The hydraulic shock absorber 100 according to the above embodiment has two patterns of damping characteristics. In contrast, the hydraulic shock absorber 101 according to this modification has four patterns of damping characteristics. Therefore, it is possible to achieve more optimal damping characteristics depending on the load weight of the vehicle.

[0056] (2) In the hydraulic shock absorber 102 shown in Fig. 4, the damping characteristics of the first damping valve 20A can also be changed in accordance with the pilot pressure. In other words, the first damping valve 20A has the same configuration as the second damping valve 20B of the hydraulic shock absorber 100 according to the above embodiment. In addition, two solenoid valves 30 are provided in parallel, and the two solenoid valves 30 switch between supplying and blocking pilot pressure to the first damping valve 20A and the second damping valve 20B, respectively. In this modified example as well, it is possible to achieve more optimal damping characteristics in accordance with the load weight of the vehicle.

[0057] Note that the hydraulic shock absorber 102 may have only one solenoid valve 30, and the first damping valve 20A and the second damping valve 20B may be operated by the pilot pressure guided through the single solenoid valve 30. Also, the check valve 23 provided in the first flow path 21 may be provided in the opposite direction. That is, the first damping valve 20A may be configured to provide resistance only to the flow of hydraulic oil from one of the bottom-side chamber 1 and the rod-side chamber 2 to the other. Furthermore, a check valve that allows hydraulic oil to flow only from the rod-side chamber 2 to the bottom-side chamber 1 may be provided in the second flow path 22 in which the second damping valve 20B is provided. In that case, the second damping valve 20B provides resistance only to the flow of hydraulic oil from the rod-side chamber 2 to the bottom-side chamber 1.

[0058] (3) The hydraulic shock absorber 103 shown in FIG. 5 is provided with a check valve 39 that guides pilot pressure from a downstream portion 33a of the pilot valve 30, which is located in the pilot passage 33 between the solenoid valve 30 and the second damping valve 20B, only to the bottom-side chamber 1. If pilot pressure remains in the downstream portion 33a of the pilot valve 30 in the pilot passage 33 when the solenoid valve 30 switches from the supply position 30B to the shutoff position 30A, the check valve 39 allows the residual pressure to be released to the bottom-side chamber 1 through the check valve 39 during the extension operation of the hydraulic shock absorber 103, so that the second damping valve 20B smoothly switches to the first throttle position 25A. Note that the check valve 39 may be provided so as to guide pilot pressure from the downstream portion 33a of the pilot valve 30 in the pilot passage 33 only to the rod-side chamber 2. In this case, the residual pressure in the downstream portion 33a is released to the rod-side chamber 2 through the check valve 39 during the contraction operation of the hydraulic shock absorber 103.

[0059] (4) In the above embodiment, the hydraulic shock absorber 100 is mounted on the vehicle with the cylinder tube 10 on the upper side and the rod 12 on the lower side. However, the hydraulic shock absorber 100 may be mounted on the vehicle with the cylinder tube 10 on the lower side and the rod 12 on the upper side. In this case, a free piston must be provided in the bottom-side chamber 1 to separate the liquid chamber in which hydraulic oil is sealed from the air chamber in which gas is sealed, so that the gas G in the bottom-side chamber 1 does not move upward. Alternatively, an accumulator connected to the bottom-side chamber 1 may be provided outside the cylinder tube 10, and an air chamber may be provided in the accumulator.

[0060] (5) In the above embodiment, the hydraulic shock absorber 100 is a single-rod type in which the tip of the rod 12 protrudes outside the cylinder tube 10, but it may also be a double-rod type in which both ends of the rod 12 protrude outside the cylinder tube 10.

[0061] The configuration, operation, and effects of each embodiment of the present invention will be described below.

[0062] Hydraulic shock absorbers 100 to 103 (fluid pressure shock absorbers) mounted on a vehicle include a cylinder tube 10, a rod 12 inserted into the cylinder tube 10 so as to be able to move back and forth, a piston 14 connected to the rod 12 and dividing the interior of the cylinder tube 10 into a bottom side chamber 1 and a rod side chamber 2, a damping valve 20 that applies resistance to the flow of hydraulic oil (working fluid) between the bottom side chamber 1 and the rod side chamber 2 and whose damping characteristics can be changed according to pilot pressure, and a solenoid valve 30 that switches between supplying and blocking pilot pressure to the damping valve 20, and the working fluid in the bottom side chamber 1 or the rod side chamber 2 is used as the pilot pressure.

[0063] In this configuration, the damping characteristics of the damping valve 20 can be changed using the hydraulic oil in the bottom-side chamber 1 or the rod-side chamber 2 as the pilot pressure, and the supply and cut-off of the pilot pressure is switched by the solenoid valve 30, so there is no need to increase the size of the damping valve 20. Therefore, it is possible to improve the mountability of the damping valve 20 that can change the damping force.

[0064] Moreover, the hydraulic oil in the bottom-side chamber 1 is used as the pilot pressure, and the bottom-side chamber 1 is filled with pressurized gas G.

[0065] In this configuration, pressurized gas G is sealed in the bottom side chamber 1, so the bottom side chamber 1 does not become negative pressure while the hydraulic shock absorber 100 is in operation, allowing the damping valve 20 to operate stably.

[0066] Furthermore, a plurality of damping valves 20 are provided in series, and a plurality of solenoid valves 30 are provided in parallel, and the plurality of solenoid valves 30 switch between supplying and blocking pilot pressure to the plurality of damping valves 20, respectively.

[0067] The damping valve 20 also includes a first damping valve 20A and a second damping valve 20B that are arranged in parallel to each other and provide resistance to the flow of hydraulic oil, and the first damping valve 20A provides resistance only to the flow of hydraulic oil from one of the bottom side chamber 1 and the rod side chamber 2 to the other.

[0068] These configurations make it possible to achieve optimal damping characteristics depending on the state of the vehicle.

[0069] In addition, the hydraulic shock absorbers 100 to 103 are further provided with a pilot passage 33 in which an electromagnetic valve 30 is provided and which guides the hydraulic oil in the bottom side chamber 1 or the rod side chamber 2 to the damping valve 20 as pilot pressure, and a check valve 39 which guides the pilot pressure from the downstream side of the electromagnetic valve 30 in the pilot passage 33 to the bottom side chamber 1 or the rod side chamber 2.

[0070] In this configuration, when the solenoid valve 30 cuts off the supply of pilot pressure, the residual pressure in the pilot passage 33 is released through the check valve 39, so that the damping valve 20 can be switched smoothly.

[0071] The rod 12 also has a rod main body 51 connected to the piston 14 and slidably supported on the cylinder tube 10, a head portion 52 exposed to the outside of the cylinder tube 10, and a rod internal space 40 formed inside the rod main body 51, the rod internal space 40 having a first space 41 communicating with the bottom side chamber 1 and a second space 42 communicating with the rod side chamber 2, the damping valve 20 and the solenoid valve 30 are provided in the head portion 52, and the pilot pressure is supplied through the first space 41 or the second space 42.

[0072] This configuration can prevent gas from being mixed into the pilot fluid.

[0073] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments. [Explanation of symbols]

[0074] 100, 101, 102, 103... Hydraulic shock absorber (fluid pressure shock absorber), 1... Bottom side chamber, 2... Rod side chamber, 10... Cylinder tube, 12... Rod, 14... Piston, 20... Damping valve, 20A... First damping valve, 20B... Second damping valve, 25A... First throttling position, 25B... Second throttling position, 27... Pilot chamber, 30... Solenoid valve, 30A... Shut-off position, 30B... Supply position, 33... Pilot passage, 39... Check valve, 40... Space inside rod, 41... First space, 42... Second space, 51... Rod body, 52... Head portion

Claims

1. A fluid pressure shock absorber mounted on a vehicle, A cylinder tube; a rod inserted into the cylinder tube so as to be able to move back and forth; a piston connected to the rod and dividing the interior of the cylinder tube into a bottom-side chamber and a rod-side chamber; a damping valve that applies resistance to the flow of working fluid between the bottom side chamber and the rod side chamber and has damping characteristics that can be changed in response to a pilot pressure; a solenoid valve that switches between supplying and blocking pilot pressure to the damping valve, A fluid pressure shock absorber, wherein the pilot pressure is the working fluid in the bottom side chamber or the rod side chamber.

2. 2. The fluid pressure shock absorber according to claim 1, The working fluid in the bottom-side chamber is used as the pilot pressure, A fluid pressure shock absorber characterized in that a pressurized gas is sealed in the bottom side chamber.

3. The fluid pressure shock absorber according to claim 1 or 2, The damping valve is provided in plurality in series, The solenoid valve is provided in plurality in parallel, A hydraulic shock absorber, wherein the plurality of solenoid valves respectively switch between supplying and blocking pilot pressure to the plurality of damping valves.

4. The fluid pressure shock absorber according to claim 1 or 2, The damping valve includes a first damping valve and a second damping valve that are provided in parallel with each other and provide resistance to the flow of the working fluid, The fluid pressure shock absorber is characterized in that the first damping valve applies resistance only to the flow of working fluid from one of the bottom side chamber and the rod side chamber to the other.

5. 5. A fluid pressure shock absorber according to claim 1, a pilot passage provided with the solenoid valve and guiding the working fluid in the bottom-side chamber or the rod-side chamber to the damping valve as a pilot pressure; a check valve that guides pilot pressure from the downstream side of the solenoid valve in the pilot passage to the bottom-side chamber or the rod-side chamber.

6. 6. A fluid pressure shock absorber according to claim 1, The rod is a rod body connected to the piston and slidably supported by the cylinder tube; a head portion exposed to the outside of the cylinder tube; a rod inner space formed inside the rod main body, the rod internal space has a first space communicating with the bottom side chamber and a second space communicating with the rod side chamber, the damping valve and the solenoid valve are provided in the head portion, A hydraulic shock absorber, wherein the pilot pressure is supplied through the first space or the second space.

7. A fluid pressure buffer according to claim 1, The damping valve applies resistance to the flow of working fluid in both directions between the bottom side chamber and the rod side chamber.

8. A fluid pressure buffer according to claim 1, The damping valve has a position that changes in response to a pilot pressure, and the resistance that it applies to the flow of the working fluid passing through the damping valve varies depending on the position.

9. A fluid pressure buffer according to claim 1, The hydraulic shock absorber is characterized in that the solenoid valve switches between supplying and blocking pilot pressure to the damping valve in accordance with the load weight of the vehicle.

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