JPH06101735A - Hydraulic damper - Google Patents

Abstract

PURPOSE:To switch damping force from small to large in a stroke in a minimum length portion and prevent an adverse effect of switching of damping force in an extension stroke. CONSTITUTION:A hydraulic damper is provided with a disk valve 7 on a side of a piston and another disk valve 14 at the bottom. A control rod inner oil passage 19 is provided for communicating a lower chamber 3 with a reservoir chamber 11. An orifice 20 is formed at the opening of the control rod inner oil passage 19. At the time of a contraction stroke in a minimum length portion, damping force is generated in the orifice 20 and the disk valve 14 at the bottom. The damping force is generated in the disk valve 14 at the bottom after cut-off of the control rod inner oil passage 19. Accordingly, the damping force is switched from small to large. In an extension stroke, oil liquid through the disk valve 7 on the side of the piston flows irrespective of the cut-off state of the control rod inner oil passage 19 so that the damping force is generated. Consequently, predetermined magnitude of the damping force can be obtained without an effect of switching of the damping force in the contraction stroke.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic shock absorber used for a vehicle suspension device or the like.

[0002]

2. Description of the Related Art As an example of conventional hydraulic shock absorber
-91639 publication. This hydraulic shock absorber is a twin-tube type, in which a cylindrical piston rod whose one end is closed is attached to the piston, and a bypass passage that connects the upper and lower chambers of the piston is formed through the inside of this piston rod, and at the bottom of the cylinder. The control rod to be inserted into the piston rod is made upright, and a small diameter portion is formed in the middle of the control rod. In this hydraulic shock absorber, the fact that the bypass passage area is switched depending on the relative position of the control rod and the piston rod is utilized, and the magnitude of the damping force can be switched depending on the position of the piston rod.

[0003]

By the way, in the hydraulic shock absorber, in the minimum length side portion, the damping force is switched so that the damping force which has been small until then becomes large during the compression stroke (so-called hard state). During the extension stroke immediately after that, the predetermined damping force is maintained without being affected by the switching of the damping force, or at the maximum long side part, the damping force that was small until then is increased during the extension stroke. On the other hand, it may be desired to maintain a predetermined damping force without being affected by the switching of the damping force during the compression stroke immediately thereafter.

In response to this demand, in the above-mentioned hydraulic shock absorber, when the switching position of the opening area of the orifice is adjusted according to the displacement of the control rod, a small damping force is increased in one of the extension stroke and the contraction stroke. However, due to this switching position adjustment, the damping force characteristic in the other stroke immediately after that also becomes large, and it is not possible to individually change the extension stroke and contraction stroke switching positions. , The above request was not properly met.

According to the invention of claim 1, the damping force is changed from a small value to a large value in the contraction stroke in the minimum length side portion, while it is affected by the switching of the damping force in the contraction step during the extension stroke. It is an object of the present invention to provide a hydraulic shock absorber capable of ensuring a predetermined damping force.

The invention of claim 2 is made in view of the above-mentioned circumstances, and the damping force is changed from a small value to a large value in the expansion stroke in the maximum length side portion, while the expansion force is expanded in the compression stroke. An object of the present invention is to provide a hydraulic shock absorber capable of ensuring a predetermined damping force without being affected by switching of the damping force during a stroke.

The invention according to claim 3 is made in view of the above circumstances, and the damping force is changed from a small value to a large value in the contraction stroke in the minimum length side portion, while the contraction is caused in the extension stroke. A damping force of a predetermined magnitude can be ensured without being affected by the switching of the damping force during the stroke, and the damping force is changed from a small value to a large value during the extension stroke in the maximum length side portion,
An object of the present invention is to provide a hydraulic shock absorber capable of ensuring a damping force of a predetermined magnitude without being affected by the switching of the damping force during the extension stroke during the contraction stroke.

[0008]

In order to achieve the above object, the invention of claim 1 is a cylinder in which an oil liquid is sealed,
A piston defining the inside of the cylinder into one oil chamber and the other oil chamber; a piston rod having one end connected to the piston and the other end protruding from the one oil chamber to the outside of the cylinder;
An insertion hole formed in the piston rod in the axial direction and having one end side opened to the other oil chamber, and the piston or the piston rod is provided with the oil liquid between the one oil chamber and the other oil chamber. A piston part communication passage that allows a flow and generates a damping force with respect to the flow of the oil liquid from at least the one oil chamber to the other oil chamber, and the piston rod that is connected to the other oil chamber and into the cylinder. Reservoir for compensating the volume of entry or exit of the oil, a defining member provided in the cylinder to define between the reservoir and the other oil chamber, and the other oil chamber provided in the defining member And a reservoir to allow the flow of the oil liquid and to generate a damping force only for the flow of the oil liquid from the other oil chamber to the reservoir chamber; It can be inserted into the insertion hole, and the other end The control rod fixed to the cylinder side and one side opened inside the control rod open to the reservoir and the other side opens to a side surface at a position separated from the fixed end of the control rod by a predetermined distance. It is characterized in that the oil passage is constituted by an oil passage which is cut off by a position, and the passage area which communicates between the one oil chamber and the other oil chamber through the insertion hole is always zero or constant.

In order to achieve the above object, a second aspect of the present invention is a cylinder in which an oil liquid is sealed, a piston defining the inside of the cylinder into one oil chamber and the other oil chamber, and one end side of which is the piston. A piston rod connected to the piston and having the other end protruding from the one oil chamber to the outside of the cylinder; an insertion hole formed in the piston rod in the axial direction and having one end open to the other oil chamber; and the insertion hole. A bypass passage that communicates the one oil chamber and the other oil chamber via the piston or the piston rod, and allows the flow of the oil liquid between the one oil chamber and the other oil chamber, A piston part communication passage that generates a damping force only for the flow of oil liquid from the one oil chamber to the other oil chamber, and the piston rod entering into the cylinder connected to the other oil chamber or Lisa to compensate the volume of exit And a defining member that is provided in the cylinder and that defines between the reservoir and the other oil chamber, and a flow of oil liquid between the other oil chamber and the reservoir that is provided on the defining member. And a defining member communication passage that generates a damping force with respect to the flow of oil liquid from at least the other oil chamber to the reservoir chamber, and one end is inserted into the insertion hole in the piston rod, and the other end is on the cylinder side. A control rod fixed to the control rod, and a bypass passage area reducing portion which is provided on one end side of the control rod and reduces the passage area of the bypass passage when the piston rod extends for a predetermined length or more. Is characterized by.

In order to achieve the above-mentioned object, a third aspect of the invention is to provide a cylinder in which an oil liquid is sealed, a piston defining the inside of the cylinder into one oil chamber and the other oil chamber, and one end of which is the piston. A piston rod connected to the piston and having the other end protruding from the one oil chamber to the outside of the cylinder; an insertion hole formed in the piston rod in the axial direction and having one end open to the other oil chamber; and the insertion hole. A bypass passage that communicates the one oil chamber and the other oil chamber via the piston or the piston rod, and allows the flow of the oil liquid between the one oil chamber and the other oil chamber, A piston part communication passage that generates a damping force only for the flow of oil liquid from the one oil chamber to the other oil chamber, and the piston rod entering into the cylinder connected to the other oil chamber or Lisa to compensate the volume of exit And a defining member that is provided in the cylinder and that defines between the reservoir and the other oil chamber, and a flow of oil liquid between the other oil chamber and the reservoir that is provided on the defining member. And a defining member communication passage that generates a damping force only for the flow of the oil liquid from the other oil chamber to the reservoir chamber, and one end is inserted into the insertion hole in the piston rod and the other end is the cylinder. Side fixed to the control rod, one side opened inside the control rod to the reservoir and the other side opened to the side surface at a position separated from the fixed end of the control rod by a predetermined distance, and communicated by the position of the piston rod. An oil passage to be shut off and a bypass passage provided on one end side of the control rod for reducing the passage area of the bypass passage when the piston rod extends for a predetermined length or more. The passage area reducing portion and the other end side of the bypass passage area reducing portion of the control rod have a constant passage area for communicating between the one oil chamber and the other oil chamber through the insertion hole. It is characterized by having done.

[0011]

According to the first aspect of the present invention, in the contraction stroke, when the oil passage in the control rod is in a state before being shielded, the oil liquid in the other oil chamber is resistant to the one oil chamber through the piston communication passage without resistance. Simultaneously with the flow, a relatively small damping force is generated and flows into the reservoir chamber via the oil passage in the control rod and the communication passage of the defining member. When the contraction process further proceeds, the oil passage in the control rod is blocked, and a relatively large damping force is generated and flows only through the defining member communication passage.

In the extension stroke, regardless of the state of the oil passage in the control rod, the oil liquid flows from the reservoir chamber to the other oil chamber through the partition member communicating passage without resistance, and at the same time to the one oil chamber. A damping force is generated and flows through the piston communication passage.

Therefore, the damping force increases at the portion where the oil passage in the control rod is shielded during the contraction stroke, but the damping force does not change depending on the state of the oil passage in the control rod during the extension stroke.

According to the second aspect of the invention, in the extension stroke, until the passage area of the bypass passage is reduced by the control rod, the oil liquid flows from the reservoir chamber to the other oil chamber without resistance to the defining member communication passage. Simultaneously with the flow through the piston part, a relatively small damping force is generated and flows into one of the oil chambers via the piston part communication passage and the bypass passage. When the extension stroke further progresses, the passage area of the bypass passage is reduced by the bypass passage area reducing portion, and a relatively large damping force is generated to flow.

In the contraction stroke, the oil liquid in the other oil chamber flows into the one oil chamber through the piston communication passage without resistance regardless of the passage area of the bypass passage. At the same time, the oil liquid in the other oil chamber generates a damping force and flows into the reservoir chamber via the partition member communicating passage.

Therefore, the damping force becomes high in the portion where the passage area of the bypass passage is reduced by the bypass passage area reducing portion during the extension stroke, but the damping force changes regardless of the passage area of the bypass passage during the contraction stroke. do not do.

According to the third aspect of the present invention, in the compression stroke, in a state where the oil passage in the control rod is not shielded, the oil liquid in the other oil chamber passes through the piston portion communication passage and the bypass passage to the one oil chamber. At the same time, the fluid flows to the reservoir chamber through the oil passage in the control rod and the communicating passage for the defining member, and a relatively small damping force is generated and flows. When the contraction process further proceeds, the oil passage in the control rod is blocked, and a relatively large damping force is generated and flows only through the defining member communication passage.

In the extension stroke, until the passage area of the bypass passage is reduced by the control rod, the oil liquid flows from the reservoir chamber to the other oil chamber without resistance through the defining member communication passage and the oil passage in the control rod. Simultaneously with the flow, a relatively small damping force is generated and flows into one of the oil chambers through the passage of the piston portion and the passage of the bypass passage.
When the extension stroke further progresses, the passage area of the bypass passage is reduced by the bypass passage area reducing portion, and a relatively large damping force is generated to flow.

Therefore, the damping force increases at the portion where the oil passage in the control rod is shielded during the contraction stroke, but the damping force does not change during the extension stroke depending on the state of the oil passage in the control rod. Further, during the extension stroke, the damping force increases at the portion where the passage area of the bypass passage is reduced by the bypass passage area reducing portion, but during the contraction stroke, the damping force does not change regardless of the passage area of the bypass passage.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A hydraulic shock absorber according to a first embodiment of the present invention will be described below with reference to FIG. In the figure, cylinder 1 is a cylinder
It is stored in 50. The inside of the cylinder 1 is the upper chamber 2,
A piston 4 defining a lower chamber 3 is slidably inserted into the two chambers, and this hydraulic shock absorber is of a twin tube type.

The piston 4 is formed with first and second piston part communication passages 5 and 6 which are piston part communication passages that connect the upper chamber 2 and the lower chamber 3 to each other. First piston communication passage 5
A piston-side disc valve 7 is arranged on the piston 4 so as to face the lower chamber-side opening of the piston 4 so that a damping force is generated by receiving the oil liquid from the first piston-port communication passage 5 during the extension stroke. Has become. A piston-side one-way valve 8 is provided on the piston 4 so as to face the upper chamber side opening of the second piston part communication passage 6, and the piston 4 from the lower chamber 3 via the second piston part communication passage 6 While allowing the flow of the oil liquid to the chamber 2 without resistance, the flow in the opposite direction is regulated.

A cylindrical piston rod 9 whose one end is closed is attached to the piston 4 with the opening side facing the defining member 10. A defining member 10 is provided on the bottom of the cylinder, and the defining member 10 serves as a defining member communication passage that connects the lower chamber 3 with the reservoir chamber 11 formed between the cylinder 1 and the cylindrical body. First and second defining member communication passages 12, 13 are formed. A bottom side disc valve 14 is disposed in the defining member 10 so as to face the reservoir chamber side opening of the first defining member communicating passage 12, and the disc valve 14 from the first defining member communicating passage 12 is provided during the contracting stroke. It receives the oil liquid and generates a damping force. The defining member 10 is provided with a bottom side one-way valve 15 so as to face the lower chamber side opening of the second defining member communication passage 13, and the reservoir via the second defining member communication passage 13 is provided. The flow of the oil liquid from the chamber 11 to the lower chamber 3 is allowed without any resistance, while the flow in the opposite direction is regulated.

A hole 10a is formed at the center of the defining member 10, and the control rod 16 is inserted into the hole 10a and is attached to the defining member 10 in an upright state. The control rod 16 has a portion (base end portion) 17 inserted into the hole 10a, one end side of which projects toward the reservoir chamber 11 side and the other end side of which projects toward the lower chamber 3 side. Part 17
The a is inserted into the insertion hole 9a of the piston rod 9, and its cross section has the shape shown in FIG. The tip side of the lower chamber side protruding portion 17a is reduced in diameter to form a small diameter portion 18 for guiding the piston rod 9.

An oil passage 19 in the control rod is formed in the base end portion 17 and opens in a portion spaced apart from the defining member 10 by a predetermined distance to connect the lower chamber 3 and the reservoir chamber 11 to each other. The passage in the opening portion of the oil passage 19 in the control rod on the lower chamber 3 side is narrowed to form an orifice 20, and a damping force is generated by the passage of the oil liquid through the orifice 20 during the compression stroke. Has become.

The operation of the hydraulic shock absorber thus configured will be described. As shown in FIG. 1, when the lower end of the piston rod 9 is located at the height of the small diameter portion 18, during the contraction stroke,
Until the piston rod 9 blocks the orifice 20, the lower chamber 3 passes through the orifice 20 and the first defining member communication passage 12.
The oil liquid flows from the reservoir chamber 11 into the reservoir chamber 11, and the orifice 20 and the bottom side disc valve 14 generate a damping force. When the movement of the piston rod 9 further advances and the piston rod 9 blocks the orifice 20, the flow of the oil liquid through the oil passage 19 inside the control rod is stopped thereafter, and only the first defining member communicating passage 12 passes. The oil liquid flows from the lower chamber 3 to the reservoir chamber 11, whereupon the bottom disc valve 14 generates a damping force. In this case, the damping force has a higher value than the damping force when the oil liquid flows through the orifice 20 described above (shows a so-called hard state characteristic).

During the extension stroke with the piston rod 9 blocking the orifice 20, first, with the piston rod 9 blocking the orifice 20, the upper chamber 2 to the lower chamber 3 pass through the first piston communicating passage 5. The oil liquid flows and the piston side disc valve 7 generates a damping force. The piston rod 9 moves away from the orifice 20
Even if 20 is opened, this damping force will be continuously generated only by the piston side disc valve 7, and the characteristic of the soft state will be exhibited.

In this way, the damping force is switched from a small value to a large value by opening and closing the orifice 20 during the compression stroke in the minimum length side portion, and at the time of the extension stroke, damping is performed without being affected by the switching of the damping force during the compression stroke. The force can be reduced to maintain the soft state characteristics.

The control rod 17 is inserted in the insertion hole 9a.
The oil liquid in the insertion hole 9a circulates through the clearance between the insertion hole 9a and the control rod 17 when entering and exiting, and at this time, a damping force is generated but can be ignored.

In the above embodiment, the insertion hole 9a is provided in the lower chamber 3
Although it was communicated with only the side hole of the piston rod, a lateral hole (similar to the lateral hole 30 in Fig. 2) that serves as an orifice is provided on the side surface of the piston rod.
A bypass passage may be provided to connect the upper chamber 2 and the lower chamber 3 with each other via 9a. In this case, even if the control rod 17 enters and exits the insertion hole 9a, the exit area is kept constant (the minimum passage area in the bypass passage is always constant), and the control rod 17 is generated through the bypass passage. The damping force is almost constant.

Next, a second embodiment of the present invention will be described with reference to FIGS.
It will be described based on. It should be noted that the parts and members shown in FIG.

A lateral hole 30 that connects the insertion hole 9a of the piston rod 9 and the upper chamber 2 is formed in a portion of the piston rod 9 opposite to the defining member 10 with respect to the first piston portion communication passage 5. A bypass passage that connects the upper chamber 2 and the lower chamber 3 is formed through the insertion hole 9a. A notch 31 extending in the longitudinal direction is formed on the outer peripheral side of the lower chamber side protrusion 17a of the control rod 16. Small-diameter portion 18 connected to the lower chamber side protrusion 17a
A gap is formed between the piston rod 9 and the piston rod 9, and in this embodiment, the small diameter portion 18 constitutes a gap forming portion. A shaft-shaped shielding portion 32 that is connected to the small-diameter portion 18 and is located in the lateral hole 30 to shield the lateral hole 30.
(Bypass passage area reduction unit) is provided.

On the reservoir chamber side protruding portion 17b of the base end portion 17,
A sub valve 33 is provided so as to generate a damping force by receiving the oil liquid from the oil passage 19 in the control rod during the contraction stroke.

The operation of the hydraulic shock absorber thus configured will be described. As shown in FIG. 2, when the lower end portion of the piston rod 9 is positioned at the height of the small diameter portion 18, during the contraction stroke,
Until the piston rod 9 blocks the orifice 20, the oil liquid flows from the lower chamber 3 to the reservoir chamber 11 through the orifice 20, the sub valve 33, and the first defining member communication passage 12 via the oil passage 19 in the control rod, The orifice 20, the sub-valve 33 and the bottom disc valve 14 generate a damping force. Then, when the piston rod 9 moves further and the piston rod 9 blocks the orifice 20, thereafter, the flow of the oil liquid through the oil passage 19 in the control rod is stopped, and only the first defining member communication passage 12 is provided. The oil liquid flows from the lower chamber 3 to the reservoir chamber 11 via the bottom disc valve 14 at this time. In this case, the damping force has a higher value than the damping force when the oil liquid flows through the orifice 20 described above (a characteristic indicating a so-called hard state is obtained).

During the extension stroke with the piston rod 9 blocking the orifice 20, first, with the piston rod 9 blocking the orifice 20, the lateral hole 30 and the small diameter portion 18 are provided.
Alternatively, the damping force (soft state) is passed through the bypass passage A formed by the gap between the notch 31 and the piston rod 9.
And the oil liquid flows, and at the same time, the oil liquid in the reservoir chamber 11 flows into the lower chamber 3 via the second partition member communication passage 13 without resistance. This state is continued even if the piston rod 9 is separated from the position of the orifice 20 and the orifice 20 is opened, and the characteristic of showing the soft state during the extension stroke in the minimum length side portion can be maintained.

In this way, the damping force is switched from a small value to a large value by opening and closing the orifice 20 during the compression stroke in the minimum length side portion, and at the time of the extension stroke, damping is performed without being affected by the switching of the damping force during the compression stroke. The force can be set to a small value to maintain the characteristic indicating the soft state.

Further, as shown in FIG. 2, the piston rod 9
When the extension stroke is carried out with the lower end portion of the valve being positioned at the height of the small diameter portion 18, the oil liquid flows through the bypass passage A as described above. Then, after the lateral hole 30 reaches the shield portion 32, the bypass passage A is shielded, and the oil liquid flows from the upper chamber 2 to the lower chamber 3 through the first piston portion communication passage 5, and at that time, on the piston side. The disc valve 7 generates a damping force.
For this reason, the damping force can be switched from a small value to a large value by the positional displacement of the lateral hole 30 with respect to the large diameter portion in the expansion stroke in the maximum length side portion.

During the contraction stroke from the state where the lateral hole 30 is located in the shielding portion 32, the lower chamber 3 is passed through the orifice 20 and the sub valve 33 via the oil passage 19 in the control rod and the first defining member communicating passage 12. Oil flows from the reservoir chamber 11 to the reservoir chamber 11, and the bottom side disc valve 14, the orifice 20, and the sub-valve 33 generate a damping force. At the same time, the oil liquid in the lower chamber 3 resists via the second piston portion communication passage 6. Instead, it flows to upper chamber 2. This state is maintained even after the horizontal hole 30 is separated from the shielding portion 32, and the characteristic indicating the soft state can be maintained.

In this way, the damping force is switched from a small value to a large value in accordance with the shielding state of the lateral hole 30 with respect to the piston rod 9 during the extension stroke at the maximum length side portion, and at the time of the contraction stroke, the damping force at the extension stroke is also set. It is possible to maintain the characteristic indicating the soft state by setting the damping force to a small value without being affected by the switching.

Next, a third embodiment of the present invention will be described with reference to FIG. The same parts and members as those shown in FIGS. 1, 2 and 4 are designated by the same reference numerals, and the description thereof will be omitted.

This hydraulic shock absorber is a double piston type in which the sub piston 40 is arranged on the piston 4. Between the piston 4 and the sub-piston 40, a piston chamber 41 formed by the piston 4, the sub-piston 40 and the cylinder 1 is formed.
And a lateral piston hole 42 that communicates with the lateral hole 30.

The sub-piston 40 has an upper chamber 2 and a piston chamber 41.
And the first and second sub-piston section communication passages 43, 44 that communicate with
Are formed. A first sub-piston side disc valve 45 is arranged in the sub-piston 40 so as to face the opening of the first sub-piston part communication passage 43 on the piston chamber side. It receives the oil liquid from 43 and generates a damping force.
A second sub-piston side disc valve 46 is provided in the sub-piston 40 so as to face the upper chamber side opening of the second sub-piston portion communication passage 44, and the second sub-piston portion communication passage is provided during the compression stroke. It receives the oil liquid from 44 and generates a damping force.

The operation of the hydraulic shock absorber thus configured will be described. As shown in FIG. 3, when the lower end of the piston rod 9 is located at the height of the small diameter portion 18, during the compression stroke,
Until the piston rod 9 blocks the orifice 20, the oil liquid flows from the lower chamber 3 to the reservoir chamber 11 through the orifice 20, the sub valve 33, and the first defining member communication passage 12 via the oil passage 19 in the control rod, The orifice 20, the sub-valve 33 and the bottom disc valve 14 generate a damping force. Then, when the piston rod 9 moves further and the piston rod 9 blocks the orifice 20, thereafter, the flow of the oil liquid through the oil passage 19 in the control rod is stopped, and only the first defining member communication passage 12 is provided. The oil liquid flows from the lower chamber 3 to the reservoir chamber 11 through which the bottom disc valve 14 generates a damping force. In this case, the damping force has a higher value than the damping force when the oil liquid flows through the orifice 20 described above (shows a so-called hard state characteristic).

During the expansion stroke with the piston rod 9 blocking the orifice 20, first, with the piston rod 9 blocking the orifice 20, the oil liquid passes through the first sub-piston communicating passage 43 to the piston chamber 41 side. On the other hand, the oil liquid flows through the bypass passage B formed by the piston lateral hole 42, the lateral hole 30, and the gap between the small diameter portion 18 or the cutout portion 31 and the piston rod 9, and the first sub-piston. The side disc valve 45 generates a damping force. This state will continue even if the piston rod 9 moves away from the position of the orifice 20 and the orifice 20 opens, and is affected by the switching of the damping force during the compression stroke during the expansion stroke in the minimum length side portion. Damping force characteristics without
In addition, by setting the value of the damping force of the first sub-piston side disc valve 45 to a small value, it is possible to obtain a characteristic indicating a soft state during the extension stroke in the minimum length side portion.

In this way, the damping force is changed from a small value to a large value by opening and closing the orifice 20 during the contraction stroke in the minimum length side portion, and the damping force is contracted during the extension stroke and affected by the switching of the damping force during the stroke. It is possible to obtain the characteristics of the soft state by setting a small value.

As shown in FIG. 3, during the extension stroke with the lower end of the piston rod 9 positioned at the height of the small diameter portion 18, as described above, the oil liquid passes through the first sub-piston communicating passage 43 and the piston While flowing to the chamber 41 side, the oil liquid flows through the bypass passage B, and the first sub-piston side disc valve 45 generates a damping force. Then, after the lateral hole 30 reaches the shield portion 32, the bypass passage B is shielded,
The oil liquid flows to the piston chamber 41 side through the first sub-piston portion communication passage 43, while flowing to the lower chamber 3 through the first piston portion communication passage 5, and the first sub-piston side disc valve 45 attenuates. A force is generated, and further, the piston side disc valve 7 generates a damping force, and a large damping force can be obtained as compared with before the lateral hole 30 reaches the shield portion 32.

When the contraction stroke is performed from the state where the lateral hole 30 is located in the large diameter portion, the oil passage in the control rod is
Oil flows from the lower chamber 3 to the reservoir chamber 11 through the orifice 20, the sub-valve 33, and the first defining member communication passage 12 via 19, and the lateral hole 30, the lateral piston hole 42, and the second sub-piston part communication passage. Oil flows through the passage 44 and the orifice
20, the sub-valve 33, the bottom side disc valve 14 and the second sub-piston side disc valve 46 generate a damping force, and this state continues even after the lateral hole 30 is separated from the shielding portion 32 and remains in the soft state. The characteristics shown can be obtained.

In this manner, the damping force is switched from a small value to a large value in accordance with the shielding state of the lateral hole 30 with respect to the piston rod 9 during the extension stroke in the maximum length side portion, and the damping force during the extension stroke during the contraction stroke. A characteristic indicating a soft state can be obtained with a small value without being affected by the switching of the damping force.

In the second and third embodiments, the damping force is increased in the maximum length side portion of the extension stroke and the minimum length side portion of the contraction stroke, but only in the maximum length side portion of the extension stroke. In order to increase the damping force, in the second embodiment, the enlarged diameter portion of the base end portion 17 of the control rod 16 is made to have the same small diameter as the small diameter portion 18, and the control internal oil passage 1
9, the orifice 20 and the like may be eliminated.

In this way, during the extension stroke, the oil liquid remains in the upper chamber 2 until the bypass passage A is blocked.
Flows into the lower chamber 3 through the first piston communication passage 5 and the bypass passage A, and a damping force (soft state) is generated in the bypass passage A and the piston side disc valve 7. After that, when the bypass passage A is shielded, the oil liquid flows only through the first piston part communication passage 5, and the damping force (hard state) is generated only by the piston side disc valve 7. During the contraction stroke, regardless of the state of the bypass passage A, the oil liquid flows from the lower chamber 3 to the upper chamber 2 through the second piston portion communication passage 6 without resistance, and at the same time, the oil liquid flows from the lower chamber 3 to the reservoir. Room
11 to the first defining member communication passage 12 provided in the defining member 10.
Through the bottom disc valve 14 to generate a damping force.

[0051]

According to the invention of claim 1, the damping force becomes high at the portion where the oil passage in the control rod is shielded during the contraction stroke, but at the extension stroke the damping force depends on the state of the oil passage in the control rod. Does not change, so
Since the damping force can be increased when contracting more than a predetermined position in the contraction stroke, full bottom (minimum length) is prevented, and at the same time, returning to the intermediate position is not prevented.

According to the second aspect of the invention, the damping force becomes high at the portion where the passage area of the bypass passage is reduced by the bypass passage area reducing portion during the extension stroke, but it does not depend on the passage area of the bypass passage during the contraction stroke. The damping force does not change. Therefore, it is possible to increase the damping force when extending beyond a predetermined position in the extension stroke, so it is possible to prevent full stroke (maximum length), and at the same time, return to the intermediate position. Does not prevent things.

According to the third aspect of the present invention, the damping force increases at the portion where the oil passage in the control rod is shielded during the contraction stroke, but the damping force changes depending on the state of the oil passage in the control rod during the extension stroke. do not do. Further, during the extension stroke, the damping force increases at the portion where the passage area of the bypass passage is reduced by the bypass passage area reducing portion, but during the contraction stroke, the damping force does not change regardless of the passage area of the bypass passage. Therefore, since the damping force can be increased when contracting more than a predetermined position in the contraction stroke, full bottom (minimum length) and full stroke (maximum length) can be prevented, and at the same time, the intermediate position Does not prevent you from returning.

[Brief description of drawings]

FIG. 1 is a sectional view showing a hydraulic shock absorber according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a hydraulic shock absorber according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a hydraulic shock absorber according to a third embodiment of the present invention.

FIG. 4 is a cross-sectional view taken along the line DD of FIGS. 2 and 3.

[Explanation of symbols]

 1 Cylinder 2 Upper Chamber 3 Lower Chamber 4 Piston 5 First Piston Port Communication Path 6 Second Piston Port Communication Path 7 Piston Side Disc Valve 9 Piston Rod 9a Insertion Hole 10 Definition Member 11 Reservoir Chamber 12 First Definition Member passage 13 Second defining member passage 14 Bottom side disc valve 19 Oil rod inside control rod 20 Orifice 32 Shield 50 Cylindrical body A Bypass passage B Bypass passage

Claims (3)

[Claims] 1. A cylinder in which an oil liquid is sealed, a piston defining the inside of the cylinder into one oil chamber and the other oil chamber,
A piston rod having one end connected to the piston and the other end protruding from the one oil chamber to the outside of the cylinder; and an insertion hole formed in the piston rod in the axial direction and having one end open to the other oil chamber, Provided on the piston or piston rod, allowing the flow of the oil liquid between the one oil chamber and the other oil chamber, and at least damping force with respect to the oil liquid flow from the one oil chamber to the other oil chamber. And a reservoir connected to the other oil chamber for compensating the volume of the piston rod entering or leaving the cylinder, and the reservoir provided in the cylinder and the other of A partition member that defines the space between the oil chambers and an oil liquid that is provided in the partition member and allows the flow of the oil liquid between the other oil chamber and the reservoir, and the oil liquid from the other oil chamber to the reservoir chamber. Only for the flow of A bounding member communicating path for generating 衰力,
A control rod, one end of which is insertable into an insertion hole in the piston rod and the other end of which is fixed to the cylinder side, and one side of which is provided inside the control rod and which opens to the reservoir and the other side of which is the control rod. An oil passage that opens at a position spaced apart from the fixed end by a predetermined distance and is cut off by the position of the piston rod, and communicates between the one oil chamber and the other oil chamber via the insertion hole. A hydraulic shock absorber characterized in that the passage area of the passage is always zero or constant. 2. A cylinder in which an oil liquid is sealed, a piston defining the inside of the cylinder into one oil chamber and the other oil chamber,
A piston rod having one end connected to the piston and the other end protruding from the one oil chamber to the outside of the cylinder; and an insertion hole formed in the piston rod in the axial direction and having one end open to the other oil chamber, A bypass passage that connects the one oil chamber and the other oil chamber through an insertion hole, and the piston or the piston rod, which is provided in the oil passage between the one oil chamber and the other oil chamber. A piston part communication passage which allows and generates a damping force only for the flow of oil liquid from the one oil chamber to the other oil chamber, and the piston rod into the cylinder connected to the other oil chamber. Reservoir for compensating the volume of entry or exit of the oil, a defining member provided in the cylinder to define between the reservoir and the other oil chamber, and the other oil chamber provided in the defining member Oil between the reservoir and the reservoir A defining member communicating passage that allows the flow and generates a damping force with respect to the flow of the oil liquid from at least the other oil chamber to the reservoir chamber; one end is inserted into the insertion hole in the piston rod, and the other end is the cylinder. A control rod fixed to the side of the control rod, and a bypass passage area reducing portion which is provided at one end of the control rod and reduces the passage area of the bypass passage when the piston rod extends for a predetermined length or more. A hydraulic shock absorber characterized in that 3. A cylinder in which an oil liquid is sealed, a piston defining the inside of the cylinder into one oil chamber and the other oil chamber,
A piston rod having one end connected to the piston and the other end protruding from the one oil chamber to the outside of the cylinder; and an insertion hole formed in the piston rod in the axial direction and having one end open to the other oil chamber, A bypass passage that connects the one oil chamber and the other oil chamber through an insertion hole, and the piston or the piston rod, which is provided in the oil passage between the one oil chamber and the other oil chamber. A piston part communication passage which allows and generates a damping force only for the flow of oil liquid from the one oil chamber to the other oil chamber, and the piston rod into the cylinder connected to the other oil chamber. Reservoir for compensating the volume of entry or exit of the oil, a defining member provided in the cylinder to define between the reservoir and the other oil chamber, and the other oil chamber provided in the defining member Oil between the reservoir and the reservoir A defining member communicating passage that allows the flow and generates a damping force only for the flow of the oil liquid from the other oil chamber to the reservoir chamber; one end is inserted into the insertion hole in the piston rod, and the other end is A control rod fixed to the cylinder side, and one side opened inside the control rod to the reservoir and the other side opened to a side face at a position separated from the fixed end of the control rod by a predetermined distance,
An oil passage which is cut off by the position of the piston rod, and a bypass passage area which is provided at one end side of the control rod and reduces the passage area of the bypass passage when the piston rod extends for a predetermined length or more. On the other end side of the reducing portion and the bypass passage area reducing portion of the control rod, the passage area communicating between the one oil chamber and the other oil chamber through the insertion hole is always constant. Characteristic hydraulic shock absorber.