JP4256229B2 - Pneumatic shock absorber - Google Patents

Description

  The present invention relates to a pneumatic shock absorber, and more particularly to an improvement of a pneumatic shock absorber that can be used as a vehicle suspension.

  Conventionally, as a pneumatic shock absorber for a vehicle, for example, a cylinder, a piston slidably inserted into the cylinder, a piston rod movably inserted into the cylinder via the piston, and a piston are provided. A device having a damping force generating element has been proposed.

In this proposal, a relief valve that opens a flow path when the vibration frequency is high is provided in a pneumatic shock absorber that exhibits a damping force characteristic that generates a large damping force according to the height of the input vibration. Thus, a mechanism for preventing an increase in damping force in a high frequency region is shown.
JP 2000-104778 A (from page 3, right column, line 41 to page 4, left column, line 22; FIGS. 2 and 3)

  The conventional pneumatic shock absorber as described above is very useful because it is lightweight and does not cause aeration because the working medium is gas. To use it as a vehicle suspension or the like as it is, the following There's a problem.

  That is, the pneumatic buffer uses a gas as a working medium, but the gas is more compressible than oil, and the flow rate of the pneumatic buffer is high because the flow rate through the flow path is limited. In the high-speed operating range, the gas acts as a spring, and the damping force generated by the pneumatic shock absorber reaches its peak.

  Further, the reaction force as a spring in which gas is generated increases exponentially with a change in the area of action, and the spring constant of the entire pneumatic shock absorber may exceed the suspension spring constant.

  This can be considered as an advantage because it increases the energy that can be stored as a shock absorber. However, when the shock absorber's expansion and contraction operation speed is large, the suspension spring constant and The spring reaction force increases, and the suspension amplitude decreases, that is, the displacement as the suspension decreases. This may cause the ride comfort of the vehicle to deteriorate.

  In the conventional pneumatic shock absorber, no consideration is given to the deterioration of the riding comfort of the vehicle.

  Therefore, the present invention was devised to improve the above-mentioned problems, and the object of the present invention is to increase the spring force generated by the gas as the working medium, which can be used particularly as a vehicle suspension. It is an object of the present invention to provide a pneumatic shock absorber that can suppress the above.

The first problem-solving means of the present invention includes a first chamber and a second chamber partitioned by a partition wall member, a flow channel communicating the first chamber and the second chamber, and a damping force provided in the middle of the flow channel. In a pneumatic shock absorber provided with a generating element and interposed between a vehicle body and an axle, a bypass path communicating between the first chamber and the second chamber, and opening and closing the bypass path in the middle of the bypass path In a pneumatic shock absorber having a normally closed valve that can open the bypass passage by a load , the valve is configured by a valve case and a spool. A hollow part and a hole communicating with the hollow part, which are formed in whole or in part, are formed, and the spool has a bottomed cylindrical shape, a port communicating with the inside and outside of the spool on the side part, and an opening side on the outer peripheral part The spool is energized from both ends thereof. The valve case is slidably inserted into the hollow portion of the valve case, and the two pressure chambers are separated by the spool in the hollow portion, and one pressure chamber is formed in the first chamber by a first passage provided in the valve case. The other pressure chamber communicates with the second chamber through a second passage provided in the valve case, and the spool is slid within the hollow portion with the pressure in the pressure chamber that becomes high when expanding and contracting at a predetermined operating speed or higher. By moving the valve case, the bypass passage is opened by making the hole of the valve case and the port of the spool or the hole of the valve case and the notch of the spool face each other.

Further, the second problem-solving means includes a first chamber and a second chamber partitioned by a partition wall member, a flow path communicating the first chamber and the second chamber, and generation of a damping force provided in the middle of the flow path. In the pneumatic shock absorber interposed between the vehicle body and the axle of the vehicle, the bypass path that communicates between the first chamber and the second chamber and the bypass path can be opened and closed in the middle of the bypass path A pneumatic shock absorber in which the valve opens the bypass path by a load, and the valve is configured by a valve case and a spool, and the entire bypass path is included in the valve case. Alternatively, a hollow portion and a hole communicating with the hollow portion are formed, and the spool has a bottomed cylindrical shape, a port communicating with the inside and outside of the spool on the side portion thereof, and an opening on the outer peripheral portion thereof from the opening side. A notch provided, and the spool is energized from both ends thereof. The valve case is slidably inserted into the hollow portion of the valve case, and the two pressure chambers are separated by the spool in the hollow portion, and one pressure chamber is formed in the first chamber by a first passage provided in the valve case. In addition to communication, the other pressure chamber communicates with the second chamber through a second passage provided in the valve case, resulting in a high pressure when the vehicle expands and contracts at a predetermined operating speed or higher in a vibration region below the unsprung resonance frequency. The bypass is opened by sliding the spool in the hollow portion with the pressure in the pressure chamber so that the hole of the valve case and the port of the spool or the hole of the valve case and the notch of the spool face each other.

The third problem-solving means is the first or second problem-solving means, wherein the first passage and the second passage cause a response delay in the air pressure that is applied to the respective pressure chambers. It is characterized by having.

Furthermore, a fourth problem solving means of the present invention is the first to third problem solving means, wherein the first chamber and the second chamber are separated by a cylinder and a piston slidably inserted into the cylinder. In addition, a piston rod is provided on one end side or both end sides of the piston, and the piston rod is used as a valve case.

  According to the invention of each claim, the pressure increase in the first chamber and the second chamber is suppressed even if the pneumatic shock absorber expands and contracts in a speed region equal to or higher than a predetermined operating speed. An increase in the spring reaction force can be effectively suppressed.

  Therefore, in this pneumatic shock absorber, it is possible to suppress an increase in the spring reaction force due to the gas compressibility both at the time of expansion and contraction, which means that the increase in the suspension spring constant is suppressed at the same time. This makes it possible to dramatically improve the ride comfort in the vehicle.

  In addition, the above-described bypass path is opened to suppress an excessive spring reaction force. At the same time, in the case of this pneumatic shock absorber, when it is extended at a speed higher than a predetermined operating speed, that is, in the vehicle In the operating speed region where the gas generates a spring reaction force that deteriorates the riding comfort, the bypass path is opened, so that the pressure drop in the extending second chamber is suppressed. When the pressure buffer is contracted from that state, the pressure increase in the second chamber is achieved early, so that a larger damping force can be obtained early. Conversely, even when the pneumatic buffer is contracted, Similar results can be obtained. In other words, the response of the damping force can be improved, and the function as a suspension can be improved.

  Further, in the pneumatic shock absorber according to the present invention, when the operating speed at the time of expansion / contraction is equal to or lower than a predetermined operating speed, the bypass path is in a cut-off state, so that even if the operating speed is low, sufficient A damping force can be generated. That is, when the pneumatic shock absorber according to the present invention is applied to a vehicle, it is possible to suppress vibration at the start of operation of the suspension of the vehicle.

Furthermore, since by actuating the valve by pressure to open the bypass passage, avoid upsizing of pneumatic shock absorber, further it is not necessary provided the power and air pressure source to the outside, consume power source of the vehicle It is economical because it is not necessary.

According to the first aspect of the present invention, since the spool valve is pressed with a simple and space-saving configuration such as a pressure chamber, an increase in the size of the pneumatic shock absorber can be avoided, and an external power supply or pneumatic pressure can be avoided. It is economical because no power source is required and the power source of the vehicle does not have to be consumed.

Furthermore, since the spool valve having the above shape is used, the flow passage area of the bypass passage can be changed according to the magnitude of the air pressure guided to each pressure chamber, that is, according to the speed at which the pneumatic shock absorber expands and contracts. Therefore, when the speed at which the pneumatic shock absorber expands and contracts changes, the damping characteristic of the damping force generated by the pneumatic shock absorber does not change abruptly. In other words, since it is possible to prevent the occurrence of an impact due to a sudden change in the attenuation characteristic, the riding comfort in the vehicle is also improved in this respect.

Further, according to the invention of claim 2 , since the bypass path remains blocked in the unsprung resonance frequency region in the vehicle, the damping force is generated only by the damping force generating element provided in the middle of the flow path. Thus, the pneumatic shock absorber can generate a high damping force. Therefore, if the damping force generating element is set so that sufficient damping force can be obtained in the unsprung resonance frequency region in the vehicle, even in the pneumatic buffer where the damping force decreases in inverse proportion to the vibration frequency, It is possible to efficiently suppress the vibration of the tire, which is an unsprung member in the vehicle, and at the same time, the spool valve is pressed with a simple and space-saving configuration called a pressure chamber. In addition, it is economical because it is not necessary to provide a power source or an air pressure source outside and the power source of the vehicle does not have to be consumed.

  Furthermore, since the spool valve having the above shape is used, the flow passage area of the bypass passage can be changed according to the magnitude of the air pressure guided to each pressure chamber, that is, according to the speed at which the pneumatic shock absorber expands and contracts. Therefore, when the speed at which the pneumatic shock absorber expands and contracts changes, the damping characteristic of the damping force generated by the pneumatic shock absorber does not change abruptly. In other words, since it is possible to prevent the occurrence of an impact due to a sudden change in the attenuation characteristic, the riding comfort in the vehicle is also improved in this respect.

According to the invention of claim 3 , since the first passage and the second passage have frequency characteristics, the vibration at the time of expansion / contraction of the pneumatic shock absorber is accelerated, that is, the vibration frequency is increased. Sometimes, a response delay can be generated in the air pressure applied to each pressure chamber. Therefore, for example, when a single impact, that is, a vibration in a transient contraction direction with a large operating speed is input to the pneumatic shock absorber, the pneumatic pressure guided to each pressure chamber is changed to the first or second passage. A response delay occurs due to the frequency characteristics of this, and the spool valve does not open the bypass path at the initial stage of vibration input, and the pneumatic shock absorber generates a large spring reaction force. Thereafter, with a slight delay, the pressure in the pressure chamber increases and the spool valve is moved to open the bypass. For this reason, in this pneumatic shock absorber, at the initial stage of vibration input, the pneumatic shock absorber can firmly support the vehicle body with a large spring reaction force, and can gently support the vehicle body with a slight delay, accumulating impact energy. The amount can be increased and the ride comfort can be improved.

According to the invention of claim 4 , since the valve is embodied in the piston rod, the piston rod is a relatively long member and is easy to form a hollow portion, so that it is easy to form the valve. In addition, there is an advantage that there is no interference with other members.

  Hereinafter, the pneumatic shock absorber according to the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic cross-sectional view showing the principle of the pneumatic shock absorber according to the first embodiment. FIG. 2 is a schematic cross-sectional view of the piston portion of the pneumatic shock absorber according to the first embodiment.

  Hereinafter, the pneumatic shock absorber in the present embodiment will be described in detail. As shown in FIG. 1, the pneumatic shock absorber includes a piston 1 as a partition member that is divided into a cylindrical cylinder 3 and a first chamber R1 and a second chamber R2. A piston rod 2 movably inserted into the cylinder 3 via the piston 1, a bypass passage B communicating the first chamber R1 and the second chamber R2, and a valve provided in the middle of the bypass passage B V, the flow paths L1 and L2 provided in the piston 1, and the damping force generation elements 11 and 12 provided in the middle of the flow paths L1 and L2, respectively. . Regarding the gas pressure sealed in the pneumatic shock absorber, specifically, depending on the vehicle model to which this pneumatic shock absorber is applied, it is set so as to exhibit the optimum damping force for that vehicle. do it.

  Hereinafter, each member will be described in detail. A piston 1 as a partition member is slidably inserted into the cylinder 3, and a tip of a piston rod 2 is connected to an upper end of the piston 1 in FIG. The piston 1 is provided with flow paths L1 and L2 and a bypass path B. The flow paths L1 and L2 are respectively provided with damping force generating elements 11 and 12, and a valve V is provided in the middle of the bypass path B. Is provided. The upper end in FIG. 1 of the cylinder 3 is sealed with a rod guide 6 that slidably supports the piston rod 2 and a seal member S, and the lower end is also sealed with a bottom member C. The inside of 3 is sealed. The rod guide 6 is fixed to the end of the cylinder 3, but is prevented from dropping from the cylinder 3 by the stop ring 7.

The valve V is set so as to be switchable between the cutoff position 17 and the two communication positions 16 and 18, and the cutoff position 17 closes the bypass passage B with the spring force of the biasing spring 19 and the biasing spring 20. Is set to a normally closed type. Further, the piston 1 is provided with a pressing means for switching the valve V to the communication position 16 and the communication position 18 by a pressure load. In the present embodiment, the pressing means is connected to the first chamber R1. A passage 22 for introducing air pressure and a passage 21 for introducing air pressure from the second chamber R2 are configured, and the valve V is shown in FIG. 1 against the spring force of the urging spring 19 by the air pressure guided to the passage 22. By pressing downward, the valve V can be switched to the communication position 18 to open the bypass path B. On the other hand, the valve V is resisted against the spring force of the urging spring 20 by the air pressure guided to the path 21. By pressing upward in FIG. 1, the valve V can be switched to the communication position 16 to open the bypass path B. Therefore, in the present embodiment, the air pressure is used as a pilot signal, and when the pilot signal supplied from the first chamber R1 is input, the bypass path B is opened and conversely supplied from the second chamber R2. When the pilot signal is input, the bypass path B is opened, and when the pilot signal is canceled, the bypass path B is blocked. Further, the valve V1 may be set so that the flow passage area of the bypass passage B is changed by the strength of the pilot signal. By doing so, the damping force can be changed by changing the pressure loss generated in the valve V. The valve V is set so that the gas can open the bypass passage B by adopting the communication position 16 or the communication position 18 when the operating speed when the pneumatic shock absorber is expanded or contracted exceeds a predetermined speed. ing. Specifically, the valve V is pushed downward in FIG. 1 by the air pressure supplied from the passage 22 when the operating speed when the pneumatic shock absorber is extended exceeds a predetermined value by the pressing means. When the bypass passage B is opened and the operating speed when the pneumatic shock absorber contracts exceeds a predetermined value, the valve V is pushed upward in FIG. When the operating speed at the time of expansion and contraction is below a predetermined value, the blocking position 17 is maintained and the bypass B is blocked. In this case, the operating speed when opening the bypass passage B is determined by the spring force of the urging springs 19 and 20, and the operating speed when opening the bypass path B, that is, the value of the predetermined operating speed is the compression of the gas. In consideration of the spring reaction force generated in the high-speed operating range of the pneumatic shock absorber due to the characteristics, the ride comfort in the vehicle on which the pneumatic shock absorber will be mounted is not deteriorated. An appropriate value is selected from the vehicle weight or the like of the vehicle.

  Incidentally, in the specific embodiment, the valve V is not disposed on the piston 1 but on the piston rod 2 connected to the piston 1 as shown in FIG. The piston rod 2 that continuously connects the piston 1 may be disposed at the front end portion or near the front end portion, and may be provided outside the cylinder 3 although not shown.

  As shown in FIG. 2, the valve V is formed as a spool valve. To explain a little, the piston rod 2 is formed with a hollow portion 2a that opens from the tip end side, and the hollow portion 2a. A spool valve 30 is slidably inserted therein. That is, the hollow portion 2a communicates with the second chamber R2. The spool valve 30 is formed in a bottomed cylindrical shape, and is provided with a port 30c that communicates an annular groove 30b formed in a side portion near the bottom and an inner periphery 30a of the spool valve 30, The outer peripheral portion of the spool valve 30 is constituted by an opening side, that is, a notch 30d provided from the lower end side in FIG. Further, the spool valve 30 includes an urging spring 19 carried by a stopper member 50 having a hole 50a in a shaft center portion provided in a lower part of the hollow portion 2a of the piston rod 2 in FIG. It is urged | biased from the both ends by the urging | biasing spring 20 carry | supported by the upper end in FIG. 2 of 2a, and is inserted in the hollow part 2a of the piston rod 2. FIG. The spool valve 30 partitions the hollow portion 2a of the piston rod 2 into a pressure chamber P1 and a pressure chamber P2. Specifically, the pressure chamber P1 is formed by a space partitioned by the upper portion of the hollow portion 2a in FIG. 2 and the spool valve 30, and the pressure chamber P2 is formed by the lower portion of the hollow portion 2a in FIG. 2 and the spool valve 30 and the stopper member 50. It is formed in the space partitioned by. The pressure chambers P1 and P2 do not necessarily have to be formed as partitioned spaces, and may be formed so that thrust by pressure is applied to the spool valve 30. Further, holes 2b and 2b communicating with the hollow portion 2a through an annular groove 2c provided in the hollow portion 2a are formed in the side portion of the piston rod 2, and the holes 2b and 2b are formed in the first chamber R1. Communicate. Therefore, the bypass passage B is constituted by the hole 2b, the hollow portion 2a, the annular groove 2c, and the hole 50a of the stopper member 50, and the second passage for introducing the air pressure to the pressure chamber P2 is a view of the hollow portion 2a. 2 is constituted by a portion below the stopper member 50 and a hole 50a of the stopper member 50. In this case, a part of the bypass passage B is the second passage, but a second passage for introducing air pressure to the pressure chamber P2 may be provided separately. Further, a through hole 2d serving as a first passage is provided on the upper end side of the hollow portion 2a. The through hole 2d communicates the first chamber R1 and the pressure chamber P1 in the hollow portion 2a, and the pressure chamber P1 is empty. It is possible to guide pressure.

  And the annular groove 30b connected to the port 30c of the spool valve 30 is such that the spool valve 30 is not loaded with the air pressure generated by the expansion and contraction of the air pressure buffer at a predetermined operating speed or higher in each of the pressure chambers P1 and P2. The piston rod 2 is in a position where it cannot be opposed to the annular groove 2c connected to the holes 2b, 2b of the piston rod 2 while being urged from both ends thereof by the respective biasing springs 19, 20 in the hollow portion 2a of the piston rod 2. In this case, since the side wall surface of the spool valve 30 is opposed to the annular groove 2c connected to the holes 2b and 2b, the valve V takes the blocking position 17, thereby The bypass path B composed of the hole 2b, the annular groove 2c, and the hollow portion 2a is in a blocked state.

Furthermore, when pneumatic pressure is supplied from the first chamber R1 to the pressure chamber P1 located above the hollow portion 2a in FIG. 2 through the through hole 2d, the spool valve 30 resists the spring force of the biasing spring 19. 2, the spool valve 30 moves downward in FIG. 2, and the annular groove 30b connected to the port 30c of the spool valve 30 is connected to the annular groove 2c connected to the holes 2b, 2b of the piston rod 2. When the valve V moves to a position where it can face, the valve V takes the communication position 18 and the bypass passage B enters the communication state. On the other hand, the pressure chamber P2 located below the hollow portion 2a in FIG. When pressure is supplied, the spool valve 30 is pressed upward in FIG. 2 against the spring force of the urging spring 20, the spool valve 30 moves upward in FIG. 2, and the holes 2 b and 2 b of the piston rod 2 are moved. Spool valve in the annular groove 2c connected to When 0 cutout 30d is moved to the opposite shell position, the valve V is bypass passage B becomes to take the communicating position 16 is the communicating state. Further, under the communication state, the flow area changes depending on the degree of overlap between the annular groove 2c and the annular groove 30b , and the degree of overlap between the annular groove 2c and the notch 30d, and gas flows between the annular groove 2c and the annular groove. The damping force can be generated by pressure loss when passing through 30b and passing through the annular groove 2c and the notch 30d. That is, the flow path area can be changed according to the magnitude of the air pressure guided to the pressure chamber P1 and the pressure chamber P2. Therefore, in the embodiment in which the valve V is embodied, the passage 22 for supplying air pressure described with reference to FIG. 1 becomes the through hole 2d and the pressure chamber P1, and the passage 21 includes the hole 50a and the hollow portion of the stopper member 50. This is the pressure chamber P2 in 2a.

  The holes 2b and 2b and the port 30c are opposed to each other, and the holes 2b and 2b and the notch 30d are opposed to each other to connect the bypass passage B. Since the bypass path B can be blocked by facing each other, the annular grooves 2c and 30b can be omitted. However, if the spool valve 30 rotates with respect to the piston rod 2, the hole 2b , 2b and the notches 30d may not be allowed to face the holes 2b and 2b. Therefore, it is preferable to provide the annular grooves 2c and 30b.

  That is, as described above, since the valve V is embodied in the piston rod 2, the piston rod is a relatively long member and can easily form a hollow portion, so that there is an advantage that it is easy to form the valve V. In addition, there is an advantage that there is no interference with other members. However, in the case where it is embodied in a portion other than the piston rod 2, a valve case having the configuration of the valve V formed on the piston rod 2 in FIG. A spool valve and each urging spring may be provided in the valve case. When a valve case is provided outside the cylinder 3 to form the valve V, the predetermined operating speed when the pneumatic shock absorber opens the bypass path is adjusted by replacing the biasing spring. Therefore, compared with the case where the valve V is formed in the piston rod, the biasing spring can be replaced without disassembling the pneumatic shock absorber itself. There is an advantage that the characteristics can be easily adjusted.

  In this specific valve V, the spool force when the spring force of the urging springs 19 and 20 and the neutral position of the spool valve 30, that is, the pneumatic pressure is not supplied to the pressure chambers P1 and P2. The operating speed when opening the bypass B, that is, a predetermined operating speed, is determined by the distance from the annular groove 30c and the notch 30d at the position of the valve 30 to the piston rod 2 to the annular groove 2c of the piston rod 2. The operating speed at the time of opening, that is, the value of the predetermined operating speed is determined by considering the spring reaction force generated in the high speed operating range of the pneumatic shock absorber due to the compressibility of the gas. It goes without saying that an appropriate value is selected from the vehicle weight of the vehicle so as not to deteriorate the ride comfort in the vehicle on which the vehicle will be mounted.

  In FIG. 2, the piston 1 is provided with a flow path L1 through which gas passes during the compression stroke of the pneumatic shock absorber and a flow path L2 through which gas passes during the expansion stroke. Leaf valves 32 and 33 are provided as damping force generating elements, respectively. Specifically, the valve stopper 28, the leaf valve 32, the piston 1, the leaf valve 33, and the valve stopper 29 are inserted in order from the top in FIG. Each member is fixed to the lower end portion side of the piston rod 2. The upper end in FIG. 2 of the flow path L1 is in contact with the lower surface in FIG. 2 of the leaf valve 32, but the lower end in FIG. There is a slight gap between them. On the other hand, the lower end of the flow path L2 in FIG. 2 is in contact with the upper surface of the leaf valve 33 in FIG. 2, but the upper end in FIG. There is a slight gap between them. As a result, the flow of gas from the second chamber R2 to the first chamber R1 is allowed in the flow path L1, but the reverse flow is blocked, while the flow from the first chamber R1 to the second flow path L2 is blocked. The flow of gas into the chamber R2 is allowed, but the reverse flow is blocked. Therefore, when the pneumatic shock absorber contracts, the gas passes through the flow path L1, and conversely, when it expands, the gas passes through the flow path L2. As described above, the damping force generation element may be a leaf valve, or a known damping force generation element may be applied. In the above description, each flow path is provided in the piston 1 serving as the partition wall member and the bypass path B is provided at the tip of the piston 1 or piston rod 2 serving as the partition wall member. As described above, the path B may be provided. A piston ring 70 is fitted on the outer periphery of the piston 1, and the piston 1 is slidably inserted into the cylinder 3 via the piston ring 70.

  In the above description, the pressing means is a passage or a pressure chamber. Although not shown, for example, a solenoid that is excited when the pressing means reaches a predetermined operating speed is spooled by this solenoid. Or other commonly used means may be used, but since the pressing means is formed with a simple and space-saving configuration such as a passage or a pressure chamber, the size of the pneumatic shock absorber is increased. This is economical because it is not necessary to provide a power source or an air pressure source outside, and the power source of the vehicle does not have to be consumed.

  Now, the operation of the pneumatic shock absorber configured as described above will be described with reference to FIG. When the piston rod 2 moves out of the cylinder 3, that is, when the pneumatic shock absorber extends, the first chamber R1 contracts, so that the air pressure in the first chamber R1 increases and the gas in the first chamber R1 increases. Tries to flow into the second chamber R2 through the flow path L2 and the bypass B provided in the piston 1. A damping force is generated by the damping force generating element 12 provided in the flow path L2, and at this time, the moving speed of the piston 1 with respect to the cylinder 3 is slow, and the operating speed of the pneumatic shock absorber is lower than a predetermined operating speed. In some cases, pneumatic pressure is applied to the valve V via the passage 22. Then, the valves V are respectively pressed, but the damping force and the spring reaction force generated by the pneumatic shock absorber, in other words, the internal pressure generated in the passage 22 is low, so that the blocking position 17 is taken. Specifically, pneumatic pressure is introduced into the pressure chamber P1 in FIG. 2 from the through hole 2d, and the spool valve 30 is moved downward in FIG. 2, but the spool valve 30 is energized by the spring force of the energizing spring 19. Accordingly, the annular groove 30b of the spool valve 30 cannot move until it faces the annular groove 2c, and as a result, the bypass path B remains blocked. Then, when the operating speed when the pneumatic shock absorber is extended is equal to or less than a predetermined value, the damping force generating element 12 generates a damping force.

  Further, when the moving speed of the piston 1 relative to the cylinder 3 is increased and the operating speed when the pneumatic shock absorber is extended becomes higher than a predetermined value, the pneumatic pressure applied to the valve V via the passage 22 is also increased. Get higher. Then, the valve V is pressed by the air pressure and takes the communication position 18 against the spring force of the biasing spring 19. Specifically, pneumatic pressure is introduced into the pressure chamber P1 in FIG. 2 from the through hole 2d, and the spool valve 30 is moved downward in FIG. The groove 30b faces the annular groove 2c. As a result, the bypass B is opened. Therefore, when the operating speed when the pneumatic shock absorber is extended is equal to or higher than a predetermined value, the damping force is generated not only by the damping force generating element 12 but also by the valve V. At this time, the bypass path B is also opened. Therefore, compared to the high gain damping force when the operating speed when the pneumatic shock absorber is extended is less than a predetermined value, the gas flow is greater when the operating speed is higher than the predetermined value. Since the road area increases as the bypass road B is opened, the generated damping force becomes a low gain. Here, the gain refers to a value obtained by dividing the generated damping force by the frequency, and indicates a change rate of the damping force with respect to the frequency.

  Conversely, when the piston rod 2 enters the cylinder 3, that is, when the pneumatic shock absorber contracts, the second chamber R2 contracts, so that the air pressure in the second chamber R2 increases and the second chamber R2 increases. The gas inside tends to flow into the first chamber R1 through the flow path L1 and the bypass path B provided in the piston 1. A damping force is generated by the damping force generating element 11 provided in the flow path L1, and at this time, the moving speed of the piston 1 with respect to the cylinder 3 is slow, and the operating speed when the pneumatic buffer is contracted is a predetermined operation. If it is lower than the speed, the air pressure is applied to the valve V via the passage 21. Each of the valves V is pressed, but the damping force and the spring reaction force generated by the pneumatic shock absorber, in other words, the internal pressure generated in the passage 21 is low, so that the blocking position 17 is taken. Specifically, the pneumatic pressure is guided from the second chamber R2 to the pressure chamber P2 in FIG. 2, and the spool valve 30 is moved upward in FIG. 2, but the spool valve 30 is attached by the spring force of the biasing spring 20. As a result, the notch 30d of the spool valve 30 cannot move until it faces the annular groove 2c, and as a result, the bypass path B remains blocked. Then, when the operating speed at the time of contraction of the pneumatic shock absorber is equal to or less than a predetermined value, a damping force is generated by the damping force generating element 11.

  Further, when the moving speed of the piston 1 with respect to the cylinder 3 increases and the operating speed when the pneumatic shock absorber contracts becomes higher than a predetermined value, the pneumatic pressure applied to the valve V via the passage 21 is also increased. Get higher. Then, the valve V is pressed by the air pressure and takes the communication position 16 against the spring force of the biasing spring 20. Specifically, the pneumatic pressure is guided from the second chamber R2 to the pressure chamber P2 in FIG. 2, and the spool valve 30 is moved upward in FIG. The notch 30d faces the annular groove 2c. As a result, the bypass B is opened. Therefore, when the operating speed at the time of contraction of the pneumatic shock absorber is equal to or higher than a predetermined value, a damping force is generated not only by the damping force generating element 11 but also by the valve V. At this time, the bypass path B is also opened. Therefore, compared to the high gain damping force when the operating speed when the pneumatic shock absorber is contracted is below a predetermined value, the gas flow is higher when the operating speed is above the predetermined value. Since the road area increases as the bypass road B is opened, the generated damping force becomes a low gain.

  Note that the volume of the piston rod 2 that is excessive or insufficient in the cylinder 3 when the pneumatic shock absorber expands or contracts enters or exits the cylinder 3 is compressible. Since compensation is performed by compression or expansion, it is not particularly necessary to form a compensation chamber.

  As described above, when the operating speed at the time of expansion / contraction of the pneumatic shock absorber is low, the bypass path B is shut off, and when the operating speed at the time of expansion / contraction of the pneumatic shock absorber is equal to or higher than a predetermined operating speed, the bypass is bypassed. Path B is opened. Here, since the gas of the working medium is a gas, the compressibility is extremely high as compared with a liquid such as oil. Therefore, as the operating speed at the time of expansion / contraction of the pneumatic buffer increases, the reaction force as a spring becomes exponential. However, in this pneumatic shock absorber, when the gas is extended at a speed higher than a predetermined operating speed, that is, the gas generates a spring reaction force that deteriorates the riding comfort in the vehicle. In the operating speed region, since the bypass passage B is opened, for example, the gas in the first chamber R1 on the contracting side passes through the bypass passage B as well as the passage L2, and the second chamber R2 on the expanding side. This increases the pressure in the first chamber R1 in the operating speed range in which the gas generates a spring reaction force that deteriorates the riding comfort of the vehicle. On the contrary, even when the pneumatic shock absorber expands after contracting, the gas flow is opposite to the above, but similarly, the pressure increase in the second chamber R2 is suppressed.

  Then, even if the pneumatic shock absorber expands and contracts in a speed range equal to or higher than a predetermined operating speed, the pressure increase in the first chamber R1 and the second chamber R2 is suppressed, so the spring reaction force caused by the gas compressibility Can be effectively suppressed.

  Therefore, in this pneumatic shock absorber, it is possible to suppress an increase in the spring reaction force due to the gas compressibility both at the time of expansion and contraction, which means that the increase in the suspension spring constant is suppressed at the same time. This makes it possible to dramatically improve the ride comfort in the vehicle.

  In addition, opening the bypass path described above to suppress excessive spring reaction force is simultaneously performed when the pneumatic shock absorber extends at a speed higher than a predetermined operating speed, that is, in the vehicle. In the operating speed region where the gas generates a spring reaction force that deteriorates the ride comfort, the bypass passage B is opened, so that the pressure drop in the second chamber R2 on the extending side is suppressed. When the pneumatic shock absorber contracts from that state, the pressure increase in the second chamber R2 is achieved early, so that a larger damping force can be obtained early, and conversely, the pneumatic shock absorber contracts. The same result can be obtained even in the case of extension after that. In other words, the response of the damping force can be improved, and the function as a suspension can be improved.

  Further, in the pneumatic shock absorber according to the present invention, when the operating speed at the time of expansion / contraction is equal to or lower than a predetermined operating speed, the bypass path is in a cut-off state, so that even if the operating speed is low, sufficient A damping force can be generated. That is, when the pneumatic shock absorber according to the present invention is applied to a vehicle, it is possible to suppress vibration at the start of operation of the suspension of the vehicle.

  Further, since the spool valve having the above-described shape is used, the flow path area of the bypass passage depends on the magnitude of the pneumatic pressure introduced into the passage, that is, according to the speed at which the pneumatic shock absorber, which is the speed of the piston with respect to the cylinder. Therefore, when the speed of expansion and contraction of the pneumatic shock absorber, which is the speed of the piston with respect to the cylinder, changes, the damping characteristic of the damping force generated by the pneumatic shock absorber does not change abruptly. In other words, since it is possible to prevent the occurrence of an impact due to a sudden change in the attenuation characteristic, the riding comfort in the vehicle is also improved in this respect.

  In the above description, the through hole 2d as the first passage of the piston rod 2 shown in FIG. 2 and the hole 50a forming a part of the second passage of the stopper member 50 are simply provided in the pressure chamber P1 and the pressure chamber P2, respectively. The through hole 2d and the hole 50a have so-called frequency characteristics due to the influence of the diameter and the axial length. Therefore, basically, the through-hole 2d and the hole 50a have the air pressure applied to the pressure chambers P1 and P2 when the vibration at the time of expansion and contraction of the pneumatic shock absorber is accelerated, that is, when the vibration frequency becomes high. Response delay can be generated. Therefore, for example, when a single impact, that is, a vibration in a transient contraction direction with a large operating speed is input to the pneumatic shock absorber, the pneumatic pressure guided to the pressure chamber P1 is determined by the frequency characteristics of the through hole 2d. A response delay occurs, and the spool valve 30 does not open the bypass B at the initial stage of vibration input, and the pneumatic shock absorber generates a large spring reaction force. Thereafter, with a slight delay, the pressure in the pressure chamber P1 increases and the spool valve 30 is moved downward in FIG. Therefore, in this pneumatic shock absorber, at the initial stage of the vibration input, the pneumatic shock absorber can firmly support the vehicle body with a large spring reaction force, and can gently support the vehicle body with a slight delay, accumulating impact energy. The amount can be increased and the ride comfort can be improved.

  Further, the frequency characteristics of the through hole 2d and the hole 50a are adjusted by setting the diameter and the axial length thereof, and the vibration frequency of the pneumatic shock absorber that prevents the pressure from propagating to the pressure chambers P1 and P2 is set in the spring of the vehicle. If it is set slightly lower than the lower resonance frequency, the bypass path B remains blocked in the unsprung resonance frequency region of the vehicle, so that the damping force generating elements 11, 12 provided in the middle of the flow paths L1, L2 are used. Therefore, the pneumatic shock absorber can generate a high damping force. Here, if the damping force generating elements 11 and 12 are set so that a sufficient damping force can be obtained in the unsprung resonance frequency region of the vehicle, the pneumatic shock absorber can reduce the damping force in inverse proportion to the vibration frequency. Even if it exists, it becomes possible to suppress efficiently the vibration of the tire which is an unsprung member in a vehicle. Needless to say, this can also be realized by adjusting the diameter and length of the passages 21 and 22 in FIG. Incidentally, the adjustment of the frequency characteristics of the through hole 2d and the hole 50a, and further the passages 21 and 22, includes the formation of a restriction such as an orifice in the middle.

  Further, in the present embodiment, the pneumatic shock absorber has been described as a so-called single rod type shock absorber, but it may be a so-called double rod type.

  This is the end of the description of the embodiment of the present invention, but the scope of the present invention is of course not limited to the details shown or described.

It is a schematic sectional drawing which shows in principle the pneumatic buffer in 1st Embodiment. It is a schematic sectional drawing of the piston part of the pneumatic shock absorber in 1st Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piston 2 Piston rod 2a Hollow part 2b Hole 2c, 30b Annular groove 2d 1st passage through-hole 3 Cylinder 11,12 Damping force generation element 16,18 Communication position 17 Blocking position 19,20 Energizing spring 21,22 Passage 30 Spool valve 30c Port 30d Notch 32, 33 Leaf valve as a damping force generation element 50 Stopper member 50a Hole which is a part of the second passage B Bypass passage L1, L2 Flow passage P1, P2 Pressure chamber R1 First chamber R2 Second Chamber V valve

Claims (4)

A vehicle body and an axle provided with a first chamber and a second chamber partitioned by a partition member, a flow channel communicating the first chamber and the second chamber, and a damping force generating element provided in the middle of the flow channel in pneumatic shock absorber which is interposed between the, has a bypass passage for communicating the first chamber and the second chamber, and a valve in the middle to the bypass path can be opened and closed a normally-closed bypass passage In the pneumatic shock absorber in which the valve opens the bypass passage by a load , the valve is configured by a valve case and a spool, and the hollow portion and the hollow form the whole or a part of the bypass passage in the valve case. The spool has a bottomed cylindrical shape, and includes a port communicating with the inside and outside of the spool on its side, and a notch provided on the outer periphery from the opening side. The hollow part of the valve case while urging from both ends The two pressure chambers are separated by the spool in the hollow portion, and one pressure chamber communicates with the first chamber through a first passage provided in the valve case, and the other The pressure chamber is communicated with the second chamber through a second passage provided in the valve case, and the spool is slid in the hollow portion with the pressure in the pressure chamber that becomes high when the pressure chamber expands and contracts at a predetermined operating speed or higher. The pneumatic shock absorber is characterized in that the bypass passage is opened by facing the hole of the spool and the port of the spool or the hole of the valve case and the notch of the spool. A vehicle body and an axle provided with a first chamber and a second chamber partitioned by a partition member, a flow channel communicating the first chamber and the second chamber, and a damping force generating element provided in the middle of the flow channel A pneumatic shock absorber interposed between the first chamber and the second chamber, and a normally closed valve capable of opening and closing the bypass passage in the middle of the bypass passage. In the pneumatic shock absorber in which the valve opens the bypass passage by a load, the valve is configured by a valve case and a spool, and the hollow portion and the hollow form the whole or a part of the bypass passage in the valve case. The spool has a bottomed cylindrical shape, and includes a port communicating with the inside and outside of the spool on its side, and a notch provided on the outer periphery from the opening side. The hollow part of the valve case while urging from both ends The two pressure chambers are separated by the spool in the hollow portion, and one pressure chamber communicates with the first chamber through a first passage provided in the valve case, and the other The pressure chamber communicates with the second chamber through a second passage provided in the valve case, and is spooled by the pressure in the pressure chamber that becomes a high pressure when expanding and contracting at a predetermined operating speed or higher in a vibration region below the unsprung resonance frequency in the vehicle. The pneumatic shock absorber is characterized in that the bypass passage is opened by sliding the valve in the hollow portion so that the hole of the valve case and the port of the spool or the hole of the valve case and the notch of the spool face each other. 3. The pneumatic shock absorber according to claim 1, wherein the first passage and the second passage have a frequency characteristic that causes a response delay in the air pressure applied to each pressure chamber . 4. The first chamber and the second chamber are separated by a cylinder and a piston slidably inserted into the cylinder, and a piston rod is provided on one or both ends of the piston, and the piston rod is used as a valve case. The pneumatic shock absorber according to any one of claims 1 to 3 .

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