Patent Application
20180162188
The present invention relates to a suspension device and an accumulator.
Hitherto, as a suspension device that suppresses a change in posture of a vehicle, JP 1993-213040 A discloses a structure in which a hydraulic damper is interposed between a vehicle body and each of left and right vehicle wheels, each hydraulic damper includes a cylinder, a piston slidably inserted into the cylinder to define an extension side chamber and a compression side chamber inside the cylinder, and a piston rod connected to the piston, the extension side chamber of one hydraulic damper communicates with the compression side chamber of the other hydraulic damper through a first passage with a damping valve, the compression side chamber of one hydraulic damper communicates with the extension side chamber of the other hydraulic damper through a second passage with a damping valve, and the accumulator is connected in the course of each of the passages through the damping valve.
In the suspension device, when the hydraulic dampers extend and contract in the same phase, the hydraulic fluid becomes excessive or deficient inside the cylinders of both hydraulic dampers by the volumes of the piston rods advancing and retracting into and from the cylinders and thus the accumulators absorb the excessive hydraulic fluid and supply the hydraulic fluid by the deficient amount. On the contrary, when the hydraulic dampers extend and contract in the opposite phases, the amount of the hydraulic fluid flowing out of the cylinder becomes larger than that of a case where the hydraulic dampers extend and contract in the same phase and thus the amount of the hydraulic fluid absorbed or supplied into the cylinders by the accumulators increases.
Thus, when the hydraulic dampers extend and contract in the opposite phases, a change in volume of the gas chamber inside each accumulator increases compared to a case where the hydraulic dampers extend and contract in the same phase. Accordingly, a gas spring reactive force of each accumulator increases and the amount of the hydraulic fluid passing through each damping valve increases. As a result, each hydraulic damper exerts a large damping force to suppress the rolling of the vehicle body. Meanwhile, when the hydraulic dampers extend and contract in the same phase, the amount of the hydraulic fluid flowing into or out of each accumulator decreases. Accordingly, the gas spring reactive force of each accumulator decreases and the amount of the hydraulic fluid passing through each damping valve decreases. As a result, when the hydraulic dampers extend and contract in the same phase, the damping force generated in each hydraulic damper decreases compared to a case where the hydraulic dampers extend and con tract in the opposite phases. Accordingly, it is possible to prevent a problem in which a vibration input to the vehicle wheel due to the unevenness on the road is transmitted to the vehicle body.
In order to improve the roll stiffness of the vehicle by the suspension device, a pressure inside the accumulator may be set to be high. In order to increase the pressure inside the accumulator, specifically, a sealing pressure of a gas charged into the gas chamber may be increased or the volume of the gas chamber may be decreased. In this way, the roll stiffness increases and the gas spring reactive force of the accumulator increases. Accordingly, since the damping force increases when the hydraulic dampers extend and contract in the same phase or only one of them extends and contracts or when the oil temperature increases, the riding comfort in the vehicle deteriorates and the vehicle height variation increases.
Further, when the sealing pressure of the gas charged into the gas chamber is increased or the volume of the gas chamber is decreased, a high pressure acts on the seal of the hydraulic damper and the free piston in the case of a structure in which the gas chamber and the liquid chamber of the accumulator are defined by the free piston. As a result, there is a possibility that the deterioration of the seal therebetween is accelerated and the durability is impaired.
Here, the invention is contrived to solve the above-described problems, an object of the invention is to provide a suspension device capable of improving roll stiffness without deteriorating the durability of a seal and the riding comfort of a vehicle, and another object of the invention is to provide an accumulator in which characteristics of a gas spring reactive force with respect to an inflow liquid amount change.
In order to attain the above-described object, a suspension device of the invention includes: a pair of liquid pressure dampers; a first passage which communicates an extension side chamber of one liquid pressure damper with a compression side chamber of the other liquid pressure damper; a second passage which communicates a compression side chamber of one liquid pressure damper with an extension side chamber of the other liquid pressure damper; and an accumulator which is provided in the course of each of the first passage and the second passage, in which each accumulator includes a hollow casing, a first free piston which is slidably inserted into the casing to define a liquid chamber and a gas chamber inside the casing, and a second free piston which is slidably inserted into the casing to define a first gas chamber and a second gas chamber inside the gas chamber, and a pressure receiving area near the first gas chamber in the second free piston is set to be smaller than a pressure receiving area near the second gas chamber.
Hereinafter, embodiments of the invention will be described with reference to the drawings. A suspension device 1 of an embodiment of the invention includes a pair of liquid pressure dampers DL and DR, a first passage P1 which connects an extension side chamber EL of one liquid pressure damper DL and a compression side chamber CR of the other liquid pressure damper DR, a second passage P2 which connects a compression side chamber CL of one liquid pressure damper DL and an extension side chamber ER of the other liquid pressure damper DR, an accumulator AL which is connected to the first passage P1, and an accumulator AR which is connected to the second, passage P2 and is used so that the liquid pressure damper DL is interposed between a vehicle body and a left front wheel axle and the liquid pressure damper DR is interposed between the vehicle body and a right front wheel axle of, for example, a four-wheeled vehicle.
First, the liquid pressure dampers DL and DR include, as illustrated in
Then, the liquid pressure dampers DL and DR are respectively connected to the first passage P1 and the second passage P2. Specifically, the first passage P1 connects the extension side chamber EL of one liquid pressure damper DL and the compression side chamber CR of the other liquid pressure damper DR and the second, passage 92 at the other side connects the compression side chamber CL of one liquid pressure damper DL and the extension side chamber ER of the other liquid pressure damper DR. That is, the first passage P1 and the second passage P2 connect crosswise the extension side chambers EL and ER and the compression side chambers CL and CR of the pair of liquid pressure dampers DL and DR.
Further, in this case, the first passage P1 is provided with damping valves 5 and 6 and the second passage P2 is also provided with damping valves 7 and 8. Thus, the flow of the hydraulic fluid passing through the damping valves 5, 6, 7, and 8 gets a resistance when the hydraulic fluid is extruded from the inside of the cylinders 2L and 2R of the liquid pressure dampers DL and DR into the first passage P1 and the second passage P2 or the hydraulic fluid is supplied into the cylinders 2L and 2R. In addition, as illustrated in
One accumulator AL is connected to the first passage P1 through a first junction JL connected between the damping valves 5 and 6 in the course of the first passage P1. The first junction JL is provided with a first valve component V1 which gives a resistance to the flow of the hydraulic fluid from the first passage P1 to the accumulator AL. The first valve component V1 is constricted to give a resistance to the bidirectional flow of the hydraulic fluid, but may be choked. Further, as illustrated in
The other accumulator AR is connected to the second passage P2 through a second junction JR connected between the damping valves 7 and 8 in the course of the second passage P2. The second junction JR is provided with a second valve component V2 which gives a resistance to the flow of the hydraulic fluid from the second passage P2 to the accumulator AR. The second valve component V2 is constricted to give a resistance to the bidirectional flow of the hydraulic fluid in this case, but may be choked. Further, as illustrated in
Each of the accumulators AL and AR includes, as illustrated in
The casing 10 has a cylindrical shape, its inner periphery is provided with a small-diameter portion 10a and a large-diameter portion 10b having an inner diameter larger than that of the small-diameter portion 10a, and a step portion 10c is formed at the boundary between the small-diameter portion 10a and the large-diameter portion 10b. Further, the casing 10 is provided with a ventilation hole 10d which is opened from the vicinity of the step portion 10c of the small-diameter portion 10a to communicate with the outside.
Further, the bottom portion of the lower end of the casing 10 in
The first free piston 11 is slidably inserted into the small-diameter portion 10a of the casing 10 and defines a liquid chamber L at a lower side and a gas chamber G at an upper side in
The second free piston 12 is slidably inserted into the large-diameter portion 10b of the casing 10 and defines the first gas chamber G1 and the second gas chamber G2 inside the gas chamber G. The first gas chamber G1 is formed between the first free piston 11 and the second free piston 12 and the second gas chamber G2 is formed at an upper position in
Specifically, the second free piston 12 is formed as a bottomed cylinder and includes a small piston portion 12a which is slidably inserted into the small-diameter portion 10a, a large piston portion 12b which is slidably inserted into the large-diameter portion and has an outer diameter larger than that of the small piston portion 12a, an annular concave portion 12c which is provided at the outer periphery between the small piston portion 12a and the large piston portion 12b, and a check valve 12e which is provided in a bottom portion 12d.
Then, the second free piston 12 defines the first gas chamber G1 with respect to the first free piston 11 inside the small-diameter portion 10a by the insertion of the small piston portion 12a into the small-diameter portion 10a. Further, the second free piston 12 defines the second gas chamber G2 at an upper position in
Further, a seal ring 12f which slides on the inner peripheral surface of the small-diameter portion 10a is attached to the outer periphery of the small piston portion 12a and a seal ring 12g which slides on the inner peripheral surface of the large-diameter portion 10b is attached to the outer periphery of the large piston portion 12b. Thus, the first gas chamber G1 and the second gas chamber G2 are closely sealed so as not to communicate with each other.
Then, when a gas is injected from the gas inlet 10f while the first free piston 11 and the second free piston 12 are inserted into the casing 10, a gas can be charged into the second gas chamber G2 and a gas can be also charged into the first gas chamber G1 through the check valve 12e.
Further, when the second free piston 12 moves inside the casing 10 downward in
In addition, since the second free piston 12 is provided with the annular concave portion 12c, the annular concave portion 12c is normally opened to the atmosphere by the ventilation hole 10d. However, when the annular concave portion 12c is not provided, the ventilation hole 10d may be opened to the step portion 10c. In this case, since the space K is formed between the large piston portion 12b of the second free piston 12 and the step portion 10c of the casing 10, a negative pressure or a high pressure is not formed in the space K when the ventilation hole 10d is provided as described above and thus the movement of the second free piston 12 is not disturbed.
Further, in the suspension device 1 of the embodiment, an annular cushion 14 is attached to an end near the second free piston 12 in the first free piston 11. Accordingly, even when the first free piston 11 and the second free piston 12 collide with each other, the cushion 14 softens an impact caused by the collision therebetween and thus suppresses a striking sound. In addition, the cushion 14 may be provided at an end near the first free piston 11 in the second free piston 12 and may be formed in an arbitrary shape other than the annular shape.
The suspension device 1 has the above-described configuration and the operation thereof will be described. First, a case in which the liquid pressure dampers DL and DR extend and contract in the same phase, that is, the displacement phases of the pistons 3L and 3R with respect to the cylinders 2L and 2R are the same in the liquid pressure dampers DL and DR will be described.
When the liquid pressure dampers DL and DR extend at the same speed, the volumes of the extension side chambers EL and ER of the liquid pressure dampers DL and DR decrease and the volumes of the compression side chambers CL and CR thereof increase. Then, the hydraulic fluid flowing out of the extension side chamber EL of one liquid pressure damper DL flows into the compression side chamber CR in which the volume of the other liquid pressure damper DR increases through the first passage P1. Further, the hydraulic fluid flowing out of the extension side chamber ER of the other liquid pressure damper DR flows into the compression side chamber CL in which the volume of one liquid pressure damper DL increases through the second passage P2.
However, in the liquid pressure dampers DL and DR, since the volumes increasing in the compression side chambers CL and CR in relation to the volumes decreasing in the extension side chambers EL and ER increase by the volumes in which the piston rods 4L and 4R are retracted from the cylinders 2L and 2R, the hydraulic fluid inside the compression side chambers CL and CR is deficient.
Thus, the hydraulic fluid of the deficient volume is supplied from the other accumulator AR of the compression side chamber CL of one liquid pressure damper DL and from one accumulator AL of the compression side chamber CR of the other liquid pressure damper DR.
In contrast, when the liquid pressure dampers DL and DR are compressed at the same speed, the volumes of the extension side chambers EL and ER of the liquid pressure dampers DL and DR increase and the volumes of the compression side chambers CL and CR thereof decrease. Then, the hydraulic fluid flowing out of the compression side chamber CL of one liquid pressure damper DL flows into the extension side chamber ER in which the volume of the other liquid pressure damper DR increases through the second passage P2. Further, the hydraulic fluid flowing out of the compression side chamber CR of the other liquid pressure damper DR flows into the extension side chamber EL in which the volume of one liquid pressure damper DL increases through the first passage P1.
However, in the liquid pressure dampers DL and DR, since the volumes decreasing in the compression side chambers CL and CR in relation to the volumes increasing in the extension side chambers EL and ER increase by the volumes in which the piston rods 4L and 4R enter the cylinders 2L and 2R, the hydraulic fluid inside the compression side chambers CL and CR becomes excessive.
Thus, the hydraulic fluid of the excessive volume is absorbed to the other accumulator AR of one liquid pressure damper DL and to one accumulator AL of the other liquid pressure damper DR.
Next, a case in which the liquid pressure dampers DL and DR extend and contract in the opposite phases, that is, the displacement phases of the pistons 3L and 3R with respect to the cylinders 2L and 2R are completely opposite in the liquid pressure dampers DL and DR will be described.
When one liquid, pressure damper DL extends and the other liquid pressure damper DR is reversely compressed at the same speed as that of one liquid pressure damper DL, the volume of the extension side chamber EL of the liquid pressure damper DL decreases, the volume of the compression side chamber CL increases, the volume oi the extension side chamber ER of the liquid pressure damper DR increases, and the volume of the compression side chamber CR decreases.
In this case, all the volumes of the extension side chamber EL of the liquid pressure damper DL and the compression side chamber CR of the other liquid pressure damper DR connected to each other by the first passage P1 decrease, and the hydraulic fluid flowing out of the extension side chamber EL of the liquid pressure damper DL and the compression side chamber CR of the liquid pressure damper DR is absorbed to one accumulator AL.
Further, all the volumes of the compression side chamber CL of the liquid pressure damper DL and the extension side chamber ER of the liquid pressure damper DR connected to each other by the second passage P2 increase, and the hydraulic fluid flowing into the compression side chamber CL of the liquid pressure damper DL and the extension side chamber ER of the liquid pressure damper DR is supplied from the other accumulator AR. The amount of the hydraulic fluid flowing into one accumulator AL and the amount of the hydraulic fluid flowing out of the other accumulator AR increase compared to a case where the liquid pressure dampers DL and DR extend and contract in the same phase.
In contrast, when the liquid pressure dampers DL and DR extend and contract reversely, the hydraulic fluid is supplied from one accumulator AL connected to the first passage P1 to the liquid pressure dampers DL and DR. Further, the hydraulic fluid extruded from the liquid pressure dampers DL and DR is absorbed by the other accumulator AR connected to the second passage P2. Also, the amount of the hydraulic fluid flowing out of one accumulator AL and the amount of the hydraulic fluid flowing into the other accumulator AR increase compared to a case where the liquid pressure dampers DL and DR extend and contract in the same phase.
Here, the damping force of one liquid pressure damper DL is proportional to the differential pressure between the extension side chamber EL and the compression side chamber CL and the damping force of the other liquid pressure damper DR is also proportional to the differential pressure between the extension side chamber ER and the compression side chamber CR.
As described above, when the liquid pressure dampers DL and DR extend and contract in the opposite phases, the amount of the hydraulic fluid exchanged by one accumulator AL, the other accumulator AR, and the liquid pressure dampers DL and DR increases compared to a case where the liquid pressure dampers DL and DR extend and contract in the same phase. Further, the gas spring reactive force of the accumulator which receives the hydraulic fluid among one accumulator AL and the other accumulator AR increases when the hydraulic fluid inflow amount increases and the pressure loss in the first valve component V1 and the second valve component V2 also increases when the passing flow amount increases.
Thus, the differential pressure of the extension side chambers EL and ER and the compression side chambers CL and CR of the liquid pressure damper DL when the liquid pressure dampers DL and DR extend and contract in the opposite phases becomes larger than the differential pressure of the extension side chambers EL and ER and the compression side chambers CL and CR of the liquid pressure damper DL when the liquid pressure dampers DL and DR extend and contract in the same phase. Thus, the damping forces generated by the liquid pressure dampers DL and DR when the liquid pressure dampers DL and DR extend and contract in the opposite phases become larger than the damping forces generated by the liquid pressure dampers DL and DR when the liquid pressure dampers DL and DR extend and contract in the same phase. Thus, according to the suspension device 1, when the vehicle body rolls so that the liquid pressure dampers DL and DR extend and contract in the opposite phases, it is possible to suppress the rolling of the vehicle body by improving the damping forces.
Additionally, in the description above, a case in which the liquid pressure dampers DL and DR extend and contract in the same phase and in the opposite phases and the piston speed is the same has been described, but the damping forces generated by the liquid pressure dampers DL and DR change depending on the amount of the hydraulic fluid supplied and discharged by the accumulators AL and AR. Thus, when only one of the liquid pressure dampers DL and DR extends and contracts or the liquid pressure dampers DL and DR extend and contract while being displaced in the phase from each other, the liquid pressure dampers DL and DR exhibit the damping forces in response to the amount of the hydraulic fluid supplied and discharged by the accumulators AL and AR. Thus, in such a case, the liquid pressure dampers DL and DR generate the intermediate damping forces between a case where the liquid pressure dampers extend and contract in the same phase and a case where the liquid pressure dampers extend and contract in the opposite phases.
As for the arrangement of the liquid pressure dampers DL and DR on the vehicle, a case in which the liquid pressure dampers DL and DR are respectively disposed between the vehicle body and the left and right wheels of the vehicle to suppress the rolling of the vehicle body has been described, but when the liquid pressure dampers DL and DR are respectively disposed between the vehicle body and the front and rear wheels of the vehicle, the damping force increases when the pitching of the vehicle body occurs and thus the pitching of the vehicle body can be suppressed. Further, when the liquid pressure dampers DL and DR are respectively disposed between the vehicle body and the right front wheel and between the vehicle body and the left rear wheel or between the vehicle body and the left front wheel and between the vehicle body and the right rear wheel, the damping force increases when the rolling or the pitching of the vehicle body occurs and thus both the rolling and the pitching of the vehicle body can be suppressed.
Next, the operations of the accumulators AL and AR will be described in detail. In the accumulators AL and AR, characteristics of the gas spring reactive force change in response to the amount of the hydraulic fluid flowing into the liquid chamber L. Hereinafter, a change in characteristic of the gas spring reactive force will be described in detail.
In an initial state where the hydraulic fluid is not supplied from the liquid pressure dampers DL and DR to the liquid chambers L of the accumulators AL and AR, as illustrated in
Then, when the hydraulic fluid flows into the liquid chambers L of the accumulators AL and AR, the first free piston 11 is pressed by the inflow hydraulic fluid and is moved upward in
Here, the pressure inside the first gas chamber G1 is indicated by Pg1, the pressure inside the second gas chamber G2 is indicated by Pg2, the pressure receiving area of the second free piston 12 receiving the pressure of the first gas chamber G1 is indicated by A1, and the pressure receiving area of the second free piston 12 receiving the pressure of the second gas chamber G2 is indicated by A2. The above-described state is maintained until the pressure Pg1 of the first gas chamber G1 satisfies the condition of Pg1≥Pg2·A2/A1 before the compression of the first free piston 11.
Meanwhile, when the amount of the hydraulic fluid flowing into the liquid chamber L increases and the movement amount of the first free piston 11 increases so that the first gas chamber G1 is further compressed, the above-described condition is satisfied. Then, a force of pressing the second free piston 12 upward by the pressure of the first gas chamber G1 exceeds a force of pressing the second free piston downward by the pressure of the second gas chamber G2 so that the second free piston 12 also moves upward in
Further, when the amount of the hydraulic fluid flowing into the liquid chamber L increases, the movement amount of the first free piston 11 increases to further compress the first gas chamber G1 so that the first free piston 11 and the second free piston 12 contact to be integrated with each other and move upward in
When the liquid pressure dampers DL and DR are stopped so that, the operations of the accumulators AL and AR also end, the hydraulic fluid which flows into the liquid chamber by the operations of the liquid pressure dampers DL and DR is discharged from the liquid chamber L and the second free piston 12 returns to an initial position in which the large piston portion 12b contacts the step portion 10c of the casing 10. Further, the first free piston 11 also returns to an initial position as illustrated in
In the accumulators AL and AR, when the hydraulic fluid inflow amount becomes small, only the first gas chamber G1 is set to be effective. Further, when the inflow amount becomes an intermediate amount, both the first gas chamber G1 and the second gas chamber G2 are set to be effective. Furthermore, when the inflow amount becomes large, only the second gas chamber G2 is set to be effective. In an area in which only the first gas chamber G1 is effective and the amount of the hydraulic fluid to the liquid chamber L is small, the characteristics of the gas spring reactive forces exerted by the accumulators AL and AR are set such that the gas spring reactive forces become extremely small when the inflow amount in this area is small and the gas spring reactive forces largely increase when the amount of the hydraulic fluid to the liquid chamber L increases to a certain degree. In an area in which both the first gas chamber G1 and the second gas chamber G2 are effective and the amount of the hydraulic fluid to the liquid chamber L becomes an intermediate amount, the characteristics of the gas spring reactive forces exerted by the accumulators AL and AR are obtained such that the gas spring reactive force having a gradient decreasing with respect to an increase in amount of the hydraulic fluid increases since the volume of the effective gas chamber G increases. In an area in which only the second gas chamber G2 is effective and the amount of the hydraulic fluid to the liquid chamber L is large, the characteristics of the gas spring reactive forces exerted by the accumulators AL and AR increase compared to a case having an intermediate gradient with respect to an increase in amount of the hydraulic fluid since the volume of the effective gas chamber G decreases. In this way, in the accumulators AL and AR, the effective volume of the gas chamber G apparently changes with respect to the hydraulic fluid inflow amount. For this reason, the characteristics in which the gas spring reactive force with respect to the hydraulic fluid inflow amount increases in proportional to the square of the hydraulic fluid are not obtained and a gas spring reactive force increase rate with respect to the hydraulic fluid inflow amount changes and decreases at a halfway position.
Thus, since the amount of the hydraulic fluid flowing into and out of the accumulators AL and AR is small when the liquid pressure dampers DL and DR extend and contract in the same phase or only one of them extends and contracts, the gas spring reactive forces exerted by the accumulators AL and AR become extremely small as described above. Thus, in the suspension device 1, when the liquid pressure dampers DL and DR extend and contract in the same phase or only one of them extends and contracts, the damping forces exerted by the liquid pressure dampers DL and DR become extremely small. On the contrary, since the amount of the hydraulic fluid flowing into and out of the accumulators AL and AR increases when the liquid pressure dampers DL and DR extend and contract in the opposite phases, the gas spring reactive forces exerted by the accumulators AL and AR increase as described above. Thus, the gas spring reactive forces increase as described above. In the suspension device 1, when the liquid pressure dampers DL and DR extend and contract in the opposite phases, the damping forces exerted by the liquid pressure dampers DL and DR can be further increased.
That is, even when the pressures of the first gas chamber G1 and the second gas chamber G2 are set to exert large gas spring reactive forces at the amount of the hydraulic fluid flowing into the accumulators AL and AR when the liquid pressure dampers DL and DR extend and contract in the opposite phases, the gas spring reactive forces are suppressed to be small at the amount of the hydraulic fluid flowing into the accumulators AL and AR when the liquid pressure dampers DL and DR extend and contract in the same phase or only one of them extends and contracts. When the pressures of the first gas chamber G1 and the second gas chamber G2 are set in this way, the suspension device 1 can exert a large damping force and suppress the rolling of the vehicle when the liquid pressure dampers DL and DR extend and contract in the opposite phases and thus the roll stiffness of the vehicle increases. Even when the pressures of the first gas chamber G1 and the second gas chamber G2 are set in this way, the gas spring reactive forces of the accumulators AL and AR are suppressed to be small when the hydraulic fluid inflow amount is small. Thus, in the suspension device 1, even when the roll stiffness of the vehicle is increased, the damping force does not become excessive and the riding comfort of the vehicle is not deteriorated when the liquid pressure dampers DL and DR extend and contract in the same phase.
Further, even when the temperature of the hydraulic fluid increases and the volume of the hydraulic fluid increases, only the first free piston 11 moves and this movement is absorbed by the first gas chamber G1. Accordingly, a change in gas spring reactive force of each of the accumulators AL and AR becomes small. Thus, since a change in gas spring reactive force of each of the accumulators AL and AR with respect to an increase in temperature of the liquid inside the liquid pressure dampers DL and DR is small, a change in vehicle height may be small.
Further, the pressure receiving area of the second free piston 12 receiving the pressure of the second gas chamber G2 is larger than the pressure receiving area of the first free piston 11 receiving the pressure of the liquid chamber L. Accordingly, even when the roil stiffness is high, the set pressures of the first gas chamber G1 and the second gas chamber G2 can be smaller than those of the accumulators of the conventional suspension device. Thus, since an excessively high pressure does not act on the seal rings 11b, 12f, and 12g provided at the cuter peripheries of the first free piston 11 and the second free piston 12 inside the accumulators AL and AR, such deterioration does not occur at an early timing and the durability is not deteriorated.
Further, since the accumulators AL and AR of the suspension device 1 are provided with the check valve 12e allowing only the flow of the gas from the second gas chamber G2 to the first gas chamber G1, a gas can be also simply injected into the first gas chamber G1 when a gas is injected into the second gas chamber G2. Further, when the pressure of the gas sealed in the first gas chamber G1 becomes lower than the pressure of the second gas chamber G2, a gas is charged from the second gas chamber G2 into the first gas chamber G1 through the check valve 12e. Accordingly, since a decrease in pressure of the first gas chamber G1 is prevented, the operations of the accumulators AL and AR and the operation of the suspension device 1 are maintained for a long period of time. In addition, the check valve 12e can be also omitted, the operations of the accumulators AL and AR and the suspension device 1 are not influenced, and the effect of the invention does not disappear. Further, when the check valve 12e is not provided, the set pressure inside the first gas chamber G1 may be different from the set pressure inside the second gas chamber G2.
Further, in the accumulators AL and AR, the casing 10 includes the small-diameter portion 10a and the large-diameter portion 10b and the second free piston 12 includes the small piston portion 12a slidably inserted into the small-diameter portion 10a and the large piston portion 12b slidably inserted into the large-diameter portion 10b. Then, the space K formed between the casing 10 and the second free piston 12 is opened to the atmosphere. In this way, since the space K formed between the casing 10 and the second free piston 12 is opened to the atmosphere, a high pressure or a negative pressure is not formed inside the space K even when the space K is compressed and expanded when the second free piston 12 moves inside the casing 10. Thus, the accumulators AL and AR can be smoothly operated while the movement of the second free piston 12 is not disturbed by the compression and the expansion of the space K. Thus, it is possible to prevent a bad influence in which the damping force increases in a situation in which the damping forces generated by the liquid pressure dampers DL and DR of the suspension device 1 need to be decreased. Even when a gas leaks from the first gas chamber G1 or the second gas chamber G2 to the space K, the space K is opened to the atmosphere. For this reason, a high pressure is not formed inside the space K due to the leakage of the gas into the space K and the movement of the second free piston 12 is not disturbed by the leakage of the gas.
Since the concave portion 11a is provided at the opposing end of the first free piston 11 with respect to the second free piston 12 in the accumulators AL and AR, the first free piston 11 can contact the second free piston 12. In this way, when the amount of the liquid flowing into the liquid chamber L increases, only the second gas chamber G2 becomes effective and the characteristics of the gas spring reactive force are changed at a halfway position so that a gas spring reactive force increase rate with respect to the amount of the liquid flowing into the accumulators AL and AR increases. In addition, the concave portion may be provided at the opposing end of the second free piston 12 with respect to the first free piston 11 and may be provided at both the first free piston 11 and the second free piston 12. Further, one or both of the opposing ends of the first free piston 11 with respect to the second free piston 12 may be provided with a protrusion 15 or the like instead of the concave portion as illustrated in
Since the cushion 14 is provided at the opposing end of the first free piston 11 with respect to the second free piston 12 of each of the accumulators AL and AR, the cushion 14 softens an impact caused by the collision therebetween and thus can suppress a striking sound. Further, the cushion may be provided at the opposing end of the second free piston 12 with respect to the first free piston 11 and may be provided at both the first free piston 11 and the second free piston 12.
While the preferred embodiments of the invention have been described in detail, modifications, changes, and replacements can be made without departing from the scope of the claims.
This application claims priority based on Japanese Patent Application No. 2015-147372 filed on Jul. 27, 2015, the contents of which are incorporated herein by reference in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-147372 | Jul 2015 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/069743 | 7/4/2016 | WO | 00 |
