JPH10220516A - Hydraulic shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To purse air in an upper oil chamber by forming a cylinder into a double-cylinder structure composed of an inner cylinder and an outer cylinder, forming a communicating passage for feeding air mixed in the upper oil chamber, to a lower oil chamber, between the inner and outer cylinders, and exhausting air mixed in the upper oil chamber to a reservoir chamber through the lower oil chamber. SOLUTION: In case of letting out air accumulated in an upper oil chamber 11 of a hydraulic shock absorber, a hollow piston rod 6 is first moved up. Pressure in the upper oil chamber 11 is therefore heightened to make oil in the upper oil chamber 11 flow to a lower oil chamber 8 through an expanding side oil passage 25a of a piston body 25 and an expanding side valve 26 and to guide the oil to the lower oil chamber 8 through a clearance between the hollow piston rod 6 and a bearing, a communicating passage between outer and inner cylinders 2, 3, and the like. Air is dispersed in the oil by vertically moving the hollow piston rod 6 several times and led to the lower oil chamber 8 gradually from the upper oil chamber 11 along with the oil every ascent of the hollow piston rod 6. The air is then led from the lower oil chamber 8 to a reservoir chamber 12 and purged to the atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement of a hydraulic shock absorber.

[0002]

2. Description of the Related Art As a hydraulic shock absorber, for example,
Japanese Unexamined Patent Publication No. 2-26093 discloses a “single-cylinder hydraulic shock absorber”. The above technology relates to a hydraulic shock absorber that can eliminate adverse effects due to air mixing in an oil liquid, eliminate product manufacturing errors due to this, and optimize shock characteristics. As shown in FIG. 1 of the publication,
A cylinder 10, a piston 20 movably inserted into the cylinder 10, a hollow rod 30 attached to the piston 20, upper and lower oil chambers 11 and 12 provided above and below the piston 20 in the cylinder 10, It has a tank chamber 32 provided in the rod 30, and a plurality of communication holes 34 opened in an intermediate portion of the hollow rod 30 to communicate the upper oil chamber 11 with the tank chamber 32.

[0003]

In the above technique, since the communication holes 34 are formed at a plurality of positions of the hollow rod 30, there is a possibility that the strength of the hollow rod 30 cannot be maintained. Further, if a spring seat, a bracket on the wheel side, or the like is attached to the outer surface of the cylinder 10 by welding or the like, the cylinder 10 may be distorted, and the piston 10 may not move smoothly. Therefore, an object of the present invention is to provide a hydraulic shock absorber that can maintain the strength of a hollow rod, smoothly move a piston, and remove air mixed with oil in a cylinder. It is in.

[0004]

According to a first aspect of the present invention, a cylinder having a double cylinder structure of an inner cylinder and an outer cylinder is provided to reduce air mixed in the upper oil chamber. A communication passage for feeding to the lower oil chamber is formed between the inner and outer cylinders so that air mixed in the upper oil chamber can be discharged to the reservoir chamber via the lower oil chamber.

[0005] Without opening a communication passage in the hollow rod,
The air collected in the upper oil chamber can be released while maintaining the strength of the hollow rod. Further, even if the parts are attached to the outer cylinder by machining or welding, the inner cylinder is not deformed, and the piston can be moved smoothly.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of a first embodiment of a hydraulic shock absorber according to the present invention at the time of extension. The hydraulic shock absorber 1 includes a cylinder 4 having a double structure including an outer cylinder 2 and an inner cylinder 3, A piston assembly 5 vertically inserted into the cylinder 4; a hollow piston rod 6 mounted on an upper part of the piston assembly 5; and a base valve assembly provided between the lower part of the hollow piston rod 6 and the piston assembly 5. 7, a lower oil chamber 8 formed below the piston assembly 5, and a cylinder 4 and a hollow piston rod 6 above the piston assembly 5.
It comprises an upper oil chamber 11 formed therebetween, and a reservoir chamber 12 formed above the base valve assembly 7 in the hollow piston rod 6.

The lower oil chamber 8 and the upper oil chamber 11 are filled with oil F, and the reservoir chamber 12 is filled with a gas G such as nitrogen gas having an atmospheric pressure or a pre-pressure applied to the upper part and an oil F in the lower part. ing. Reference numeral 13 denotes a mounting portion for connecting to a knuckle of a wheel (not shown); 14, a suspension spring; 15, a lower spring seat; 16, a bump stopper rubber;
Is a cone-shaped stopper rubber guide that encloses the bump stopper rubber 16, and 18 is a vehicle body mounting portion for mounting the hydraulic shock absorber 1 to the vehicle body.

FIG. 2 is an enlarged sectional view for explaining the structure of the first embodiment of the hydraulic shock absorber according to the present invention and the operation of the extension stroke. The piston assembly 5 includes a large-diameter portion 21a, a small-diameter portion 21b and A joint bolt 21 called a bottle neck member in which an oil passage 21c is formed in the shape of a bottle neck, and a cap nut 22 with a hole fitted to a small diameter portion 21b thereof in order;
Upper washer 23, check valve 24, piston body 25, extension side valve 26, lower washer 27, cap nut 22 with these holes, upper washer 23, check valve 24, piston body 25, extension side valve 26, lower washer 27 And a nut 28 for fixing the joint to the joint bolt 21. 29 is an O-ring,
It is a seal member when the large diameter portion 21a of the joint bolt 21 is fitted to the large diameter portion 6a formed on the inner surface of the lower end of the hollow piston rod 6.

The oil passage 21c of the joint bolt 21 is for flowing the oil in the reservoir chamber 12 to the lower oil chamber 8. The cap nut 22 with a hole is a female screw 22 that is screwed to a male screw portion 6b formed at the lower end of the hollow piston rod 6.
a is a part for attaching the piston assembly 5 to the hollow piston rod 6.

The check valve 24 is a valve that permits only the flow of oil from the lower oil chamber 8 to the upper oil chamber 11.
The piston body 25 is provided with an extension-side oil passage 2 serving as an oil passage.
5a and a contraction side oil passage 25b. 25c is the inner surface of the piston body 25, 25d is the piston ring mounted on the piston body 25, 25e is the inner surface 3 of the inner cylinder 3.
This is the outer surface of the piston ring 25d that fits with the a.

The base valve assembly 7 has a base valve body 31 fitted into the enlarged diameter portion 6a of the hollow piston rod 6 and fixed by pressing upward at the upper end of a joint bolt 21 of the piston assembly 5; A compression valve 32 provided at the upper end of the main body 31 to generate a damping force at the time of compression; a check valve 33 provided at the lower end of the base valve main body 31 to allow only the flow of oil from the reservoir chamber 12 to the lower oil chamber 8; And a bolt 34 and a nut 35 which are fixing members for fixing the contraction side valve 32 and the check valve 33 to the base valve body 31. Reference numerals 36 and 37 are washers. The base valve body 31 includes an extension-side oil passage 31a and a contraction-side oil passage 31.
b.

Next, the flow of oil during the extension operation of the hydraulic shock absorber 1 described above will be described. In FIG. 2, when the hollow piston rod 6 rises, the piston assembly 5 and the base valve assembly 7 rise, and the oil in the upper oil chamber 11 passes through the extension-side oil passage 25 a of the piston body 25 and passes through the extension-side valve 26. Push open to reach the lower oil chamber 8.
At this time, an extension-side damping force is generated.

Further, as the volume of the hollow piston rod 6 in the cylinder 4 decreases, the oil in the reservoir chamber 12 passes through the extension-side oil passage 31a of the base valve body 31, pushes the check valve 33 open, and opens the joint bolt. 21 to the lower oil chamber 8 through the oil passage 21c.

FIG. 3 is a cross-sectional view of the hydraulic shock absorber according to the first embodiment of the present invention when compressed, showing a state where the upper end of the cylinder 4 has hit the bump stopper rubber 16. At this time, as the volume of the hollow piston rod 6 in the cylinder 4 increases, the oil F in the reservoir chamber 12 increases.

FIG. 4 is an enlarged sectional view for explaining the operation of the compression stroke of the first embodiment of the hydraulic shock absorber according to the present invention. When the hollow piston rod 6 descends, the oil in the lower oil chamber 8 The check valve 24 is pushed open through the compression-side oil passage 25 b of the piston body 25 to reach the upper oil chamber 11.

The oil in the lower oil chamber 8 passes through the oil passage 21c of the joint bolt 21 as the volume of the hollow piston rod 6 in the cylinder 4 increases.
The contraction-side valve 32 is pushed open through the contraction-side oil passage 31 b of the base valve body 31 to reach the reservoir chamber 12. At this time, a damping force on the contraction side is generated.

The operation of the cylinder 4 of the hydraulic shock absorber 1 described above will now be described. FIG. 5 is an enlarged sectional view of a main part of the cylinder of the first embodiment of the hydraulic shock absorber according to the present invention,
The hydraulic shock absorber 1 is configured such that the cylinder 4 has a double cylinder structure of the outer cylinder 2 and the inner cylinder 3 so that the upper oil chamber 11
The communication passage 41 for sending the air A mixed into the lower oil chamber 8
It is formed between the inner cylinders 2 and 3.

In the figure, reference numeral 42 denotes a bearing, a housing 42a for fitting the outer surface to the inner surface 2a of the outer cylinder 2 and positioning the upper end of the inner cylinder 3, and a bush fitting to the inner surface of the housing 42a. 42b. Reference numeral 42c denotes a plurality of vertical grooves provided on the outer surface of the housing 42a, 43 denotes an oil seal, and 44 denotes an inner cylinder 3.
Reference numeral 44a denotes an oil passage, and reference numeral 45 denotes a bottom cover which is the bottom of the cylinder 4. 46 is a rebound rubber, 46a is a rubber stopper, and 46b is a ring.

During the assembly of the hydraulic shock absorber 1, the air A mixes with the oil F in the hydraulic shock absorber 1. Air A in lower oil chamber 8
Is the oil passage 2 of the upper piston assembly 5 shown in FIG.
There is no problem because it escapes to the reservoir chamber 12 via the base valve assembly 1c and the base valve assembly 7, but in FIG. 5, the air A accumulated in the upper oil chamber 11 cannot escape as it is.

Then, the air A accumulated in the upper oil chamber 11 is evacuated as follows. First, the hollow piston rod 6 is raised with respect to the cylinder 4. The pressure in the upper oil chamber 11 increases, and as described with reference to FIG. 2, the oil in the upper oil chamber 11 is supplied to the lower oil chamber 8 via the extension oil path 25 a of the piston body 25 and the opened extension valve 26. Flows to
As shown by the arrow in FIG. 5, the clearance passes through the gap between the hollow piston rod 6 and the bearing 42, the gap between the bearing 42 and the oil seal 43, the vertical groove 42c of the bearing 42, the communication passage 41, and the oil passage 44a of the positioning member 44. It reaches the oil chamber 8. Next, the hollow piston rod 6 is lowered with respect to the cylinder 4, and then the hollow piston rod 6 is raised again.

When this process is repeated several times, the air A is separated from the oil F at first, but the air A becomes fine bubbles and is gradually dispersed in the oil F. The oil is gradually sent from the upper oil chamber 11 to the lower oil chamber 8 together with F, and reaches the reservoir chamber 12 from the lower oil chamber 8.

As described above, by forming the cylinder 4 into a double cylinder structure of the inner cylinder 3 and the outer cylinder 2, the communication passage 4 for sending the air A mixed into the upper oil chamber 11 to the lower oil chamber 8.
1 is formed between the inner and outer cylinders 3 and 2 so that the air A mixed in the upper oil chamber 11 can be discharged to the reservoir chamber 12 through the lower oil chamber 8, so that a communication passage is opened in the hollow piston rod 6. Thus, the air A accumulated in the upper oil chamber 11 can be removed while maintaining the strength of the hollow piston rod 6.

Further, as shown in FIG.
Mounting portion 13 on the wheel side and the lower spring seat 1
In the case where the inner cylinder 3 is mounted, since the inner cylinder 3 is not affected by machining or welding, the inner cylinder 3 is not deformed, and the piston assembly 5 can move smoothly.

FIG. 6 is a view showing an assembly procedure of the first embodiment of the hydraulic shock absorber according to the present invention. When assembling the base valve assembly 7 and the piston assembly 5 to the hollow piston rod 6, first, the hollow piston The outer surface 31c of the base valve body 31 is fitted to the enlarged diameter portion 6a at the lower end of the rod 6, and the base valve assembly 7 is inserted to the depth of the enlarged diameter portion 6a.

Next, the enlarged diameter portion 6a of the hollow piston rod 6
The large-diameter portion 21a of the joint bolt 21 is fitted to the male screw portion, the female thread portion 22a of the cap nut 22 having a hole is screwed to the external thread portion 6b of the hollow piston rod 6, and the upper end 21d of the joint bolt 21 is connected to the base valve body. The base valve assembly 7 and the piston assembly 5 are assembled to the hollow piston rod 6 against the step 31d of the base 31.

At this time, the nut 2 of the piston assembly 5
After the nut 8 is loosened, the cap nut 22 with a hole may be fastened to the hollow piston rod 6 and then the nut 28 may be fastened. By fitting the large-diameter portion 21a of the joint bolt 21 to the hollow piston rod 6 in this manner, the assembling accuracy of the hollow piston rod 6 and the piston assembly 5 can be improved. By fitting the inner surface 25c of the piston body 25 to the small diameter portion 21b, the assembling accuracy of the joint bolt 21 and the piston body 25 and the outer surface 25e of the piston ring 25d attached to the piston body 25 and the inner cylinder shown in FIG. The fitting accuracy of the piston assembly 3 with the inner surface 3a is also improved, and the vertical movement of the piston assembly 5 in the inner cylinder 3 can be performed smoothly.

In FIG. 6, the hydraulic shock absorber has been assembled by sequentially assembling a plurality of parts constituting the piston portion and the base valve portion into the hollow piston rod. By providing an assembling unit that can be assembled by itself, for example, a plurality of piston assemblies 5 and base valve assemblies 7 are pre-assembled on a factory assembly line or the like, and these are assembled into the hollow piston rod 6. By assembling, assemblability can be improved.

FIG. 7 is a sectional view showing a second embodiment of the hydraulic shock absorber according to the present invention, and shows another embodiment of the piston assembly and the base valve assembly of the first embodiment. The same components as those of the first embodiment are denoted by the same reference numerals, and the detailed description is omitted. The valve assembly 47 includes a piston portion 51 and a base valve portion 52, and is formed by integrating the piston portion 51 and the base valve portion 52.

The piston part 51 is formed of a hollow piston rod 4
Large diameter portion 53 for caulking to the inner surface 48a of
a, a joint bolt 53 having a
4a is provided with a piston main body 54 mounted thereon. Note that 48
b is a swaged portion of the hollow piston rod 48, 53b is a small diameter portion of the joint bolt 53, 53c is an outer circumferential groove for swaging the joint bolt 53, and 53d is a joint bolt 5
3 is a flange portion, and 54b is an extension-side oil passage of the piston body 54.
4 c is a contraction-side oil passage of the piston main body 54, and 54 d is an inner surface of the piston main body 54.

The base valve portion 52 includes a base valve body 56 in which an outer surface 56a is fitted to an upper inner surface 53e of the joint bolt 53 and an upper end 53f of the joint bolt 53 is bent and fixed. Reference numeral 56b denotes an extension-side oil passage, and reference numeral 56c denotes a contraction-side oil passage.

FIG. 8 is a diagram showing an assembly procedure of a hydraulic shock absorber according to a second embodiment of the present invention.
7, the base valve part 52 is inserted into the upper inner surface 53e of the joint bolt 53 of the piston part 51, and the upper end 53f of the joint bolt 53 of the piston part 51 is bent. The base valve part 52 is attached to the piston part 51.

After the valve assembly 47 is assembled in this manner, the large diameter portion 53a of the joint bolt 53 is fitted to the inner surface 48a of the hollow piston rod 48, and the lower end 48c of the hollow piston rod 48 is connected to the joint bolt 53.
The valve assembly 47 is inserted until it hits the flange 53d.

Next, as shown in FIG. 7, the hollow piston rod 4 outside the outer peripheral groove 53c of the joint bolt 53
8. Caulking the outer surface to fix the valve assembly 47 to the hollow piston rod 48. By fitting the large-diameter portion 53a of the joint bolt 53 into the hollow piston rod 48 in this manner, the assembling accuracy of the hollow piston rod 48 and the valve assembly 47 can be improved. By fitting the inner surface 54d of the piston body 54 into the small diameter portion 53b, the assembling accuracy of the joint bolt 53 and the piston body 54 and the outer surface of the piston ring 54a of the piston body 54 and the inner surface 3a of the inner cylinder 3 are increased.
The assembling accuracy of the valve assembly 47 is also improved, and the up and down movement of the valve assembly 47 in the inner cylinder 3 can be performed smoothly. Also, by assembling the valve assembly 47 in advance, for example,
The ease of assembly of the hydraulic shock absorber 1 on the assembly line can be improved.

FIG. 9 is a sectional view showing a third embodiment of the hydraulic shock absorber according to the present invention, and shows an example in which a free piston is provided in the reservoir chamber of the first embodiment. The same components as those of the first embodiment are denoted by the same reference numerals, and the detailed description is omitted. This shows that a free piston 61 that can move up and down to separate oil F and gas G given a preload is provided in a reservoir chamber 12 provided in the hollow piston rod 6 of the hydraulic shock absorber 60. Reference numeral 62 denotes an O-ring. By providing the free piston 61 in the reservoir chamber 12 as described above, the hydraulic shock absorber 60 can be used even when it is turned upside down.

FIG. 10 is a sectional view showing a fourth embodiment of the hydraulic shock absorber according to the present invention, and shows an example in which an oil lock piece is provided below the cylinder of the first embodiment. The same components as those of the first embodiment are denoted by the same reference numerals,
Detailed description is omitted. The bottom cover 45 at the lower end of the hydraulic shock absorber 70
When the hydraulic shock absorber 70 is fully compressed, the hollow piston rod 6
The figure shows that an oil lock piece 71 for preventing bottom striking is provided.

The oil lock piece 71 has an outer diameter tapered portion 71a whose diameter increases downward from the upper end, and a cylindrical portion 71b following the outer diameter tapered portion 71a.
The lower portion 1b is fixed to the bottom lid 45 by welding. Outer diameter tapered portion 71a and cylindrical portion 7 of oil lock piece 71
1b can be fitted to the inner surface of the oil passage 21c of the joint bolt 21.

The operation of the oil lock piece 71 described above will now be described. FIG. 11 is a sectional view for explaining the operation of the fourth embodiment of the hydraulic shock absorber according to the present invention.
It will be described together with 0. First, in FIG. 10, the hollow piston rod 6 approaches the bottom cover 45 at the bottom of the cylinder 4,
While the hydraulic shock absorber 70 is being compressed, the oil in the lower oil chamber 8 is supplied to the oil passage 21c of the joint bolt 21, the contraction-side oil passage 31b of the base valve 31, and the reservoir chamber 12 in the same manner as shown in FIG. , The compression side oil passage 25 of the piston body 25
It passes through two paths, b → upper oil chamber 11.

In FIG. 11, when the hydraulic shock absorber 70 comes close to the maximum compression, the outer diameter tapered portion 71a of the oil lock piece 71 gradually fits into the oil passage 21c of the joint bolt 21 of the piston assembly 5, and the oil lock piece 71
As a result, the oil passage 21c is gradually narrowed, so that the resistance when the oil flows is increased, and the lowering of the hollow piston rod 6 is prevented.

Further, when the hollow piston rod 6 descends, the cylindrical portion 71 of the oil lock piece 71 is inserted into the oil passage 21c.
b is fitted, and the oil passage 21c is closed. Therefore, the oil stops flowing in the oil path, that is, the cylinder 4
The volume of oil that has entered the hollow piston rod 6 into the cylinder 4 cannot flow, and the hollow piston rod 6
Cannot enter, and further lowering of the hollow piston rod 6 is prevented.

As described above, since the oil lock piece 71 which can be fitted into the oil passage 21c provided at the lower portion of the hollow piston rod 6 at the time of the most compression of the hydraulic shock absorber 70 is provided at the lower portion of the cylinder, the bottom of the hollow piston rod 6 is provided. Thrust can be prevented.

In the second embodiment shown in FIG. 7 of the present invention, the base valve portion 52 is inserted into the upper inner surface 53e of the joint bolt 53, and the upper end 53f of the joint bolt 53 is bent. Although the base valve part 52 is attached to the piston part 51, the present invention is not limited to this. A female screw is formed on the upper inner surface of the joint bolt 53, and a screw is formed on the outer surface of the base valve body 56, and these are screwed together. A base valve part 52 may be attached to the piston part 51.

[0042]

According to the present invention, the following effects are exhibited by the above configuration. In the hydraulic shock absorber according to the first aspect, a communication passage for sending air mixed in the upper oil chamber to the lower oil chamber is formed between the inner and outer cylinders by using a double cylinder structure of the inner cylinder and the outer cylinder. In addition, since air mixed in the upper oil chamber can be discharged to the reservoir chamber through the lower oil chamber, a communication passage is not opened in the hollow piston rod, and the strength of the hollow piston rod is maintained while maintaining the strength of the hollow piston rod. The air accumulated in the air can be removed. Further, even if the parts are attached to the outer cylinder by machining or welding, the inner cylinder is not deformed, and the piston can be moved smoothly.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view for explaining the configuration of the first embodiment of the hydraulic shock absorber according to the present invention and the operation of the extension stroke;

FIG. 3 is a cross-sectional view of the hydraulic shock absorber according to the first embodiment of the present invention when compressed.

FIG. 4 is an enlarged cross-sectional view illustrating the operation of the compression stroke of the first embodiment of the hydraulic shock absorber according to the present invention.

FIG. 5 is an enlarged sectional view of a main part of a cylinder of the hydraulic shock absorber according to the first embodiment of the present invention.

FIG. 6 is an assembly procedure diagram of the first embodiment of the hydraulic shock absorber according to the present invention.

FIG. 7 is a cross-sectional view showing a second embodiment of the hydraulic shock absorber according to the present invention.

FIG. 8 is an assembly diagram of a hydraulic shock absorber according to a second embodiment of the present invention.

FIG. 9 is a sectional view showing a third embodiment of the hydraulic shock absorber according to the present invention.

FIG. 10 is a sectional view showing a fourth embodiment of the hydraulic shock absorber according to the present invention.

FIG. 11 is a cross-sectional view illustrating the operation of a hydraulic shock absorber according to a fourth embodiment of the present invention.

[Explanation of symbols]

1, 60, 70: hydraulic shock absorber, 2: outer cylinder, 3: inner cylinder, 4: cylinder, 5: piston (piston assembly), 6: hollow piston rod, 8: lower oil chamber, 1
DESCRIPTION OF SYMBOLS 1 ... Upper oil chamber, 12 ... Reservoir chamber, 41 ... Communication path, 45
... the bottom (bottom lid).

Claims (1)

[Claims] 1. A cylinder for generating a damping force is inserted into a cylinder having a bottom so as to be able to move up and down, the inside of the cylinder is divided into upper and lower oil chambers, and a hollow piston rod is attached to the piston from above. In a hydraulic shock absorber in which a reservoir chamber is formed in a piston rod and oil is taken in and out of the reservoir chamber in accordance with a change in volume of the cylinder, the cylinder has a double cylinder structure of an inner cylinder and an outer cylinder. As a result, a communication passage for sending air mixed into the upper oil chamber to the lower oil chamber is formed between the inner and outer cylinders, and the mixed air in the upper oil chamber can be discharged to the reservoir chamber via the lower oil chamber. A hydraulic shock absorber.