A hydraulic shock absorber piston unit and assembly method thereof

Abstract

The present invention discloses a hydraulic shock absorber piston unit and an assembly method thereof. The existing piston unit is easy to loosen or the initial pre-pressure of the spring is easy to change during assembly. In one direction of the piston of the present invention, a core valve assembly 1 is arranged in the mounting hole, and in another direction, a core valve assembly 2 is arranged in the mounting hole; the core valve assembly 1 and the core valve assembly 2 are both composed of a spring, a core valve, an adjusting screw, a locking screw and a washer; the spring and the core valve are both placed in the mounting hole; the adjusting screw and the core valve form a sliding pair, and are threadedly connected to the mounting hole, and its inner end face is in contact with the outer end face of the boss of the core valve; the washer and the locking screw are both sleeved on the core valve, and the washer is placed between the adjusting screw and the locking screw; radial clearances are provided between the central hole walls of the locking screw and the washer and the outer cylindrical surface of the core valve; the surface roughness of the outer end face of the adjusting screw, the inner end face of the locking screw and the two end faces of the washer is not greater than 3.2. During assembly of the present invention, the initial pre-pressure of the spring does not change, and the damping performance of the shock absorber is stable.

Description

Technical Field

[0001] The invention belongs to the technical field of oil pressure shock absorbers for rail vehicles, and in particular relates to an oil pressure shock absorber piston unit and an assembly method thereof, and is particularly suitable for double-circulation oil pressure shock absorbers of rail vehicles. Background Art

[0002] The common structure of the existing dual-circulation oil shock absorber is as follows: Figure 1 and Figure 2 As shown. Among them, Figure 1 It is a schematic diagram of the working state of each core valve assembly and the oil flow direction of the shock absorber during the stretching process. The end cover 1 is fixed to the cylinder body. The curved arrow represents the oil flow direction. At this time, the core valve assembly 1 21 and the core valve assembly 3 31 are opened, and the core valve assembly 2 22 and the core valve assembly 4 32 are closed; Figure 2 It is a schematic diagram of the working state of each core valve assembly and the oil flow direction of the shock absorber during the compression process. The curved arrow represents the oil flow direction. At this time, the core valve assembly 22 and the core valve assembly 4 32 are open, and the core valve assembly 1 21 and the core valve assembly 3 31 are closed. It can be seen that the main structural features of this shock absorber are: four sets of valve systems, in which the core valve assembly 1 21 and the core valve assembly 2 22 are arranged on the piston unit 2, and the core valve assembly 3 31 and the core valve assembly 4 32 are arranged on the bottom valve unit 3. The piston unit and the bottom valve unit are functional components of the shock absorber to establish the damping force.

[0003] A typical structure of the piston unit (glue coating) is shown in Figure 3 and Figure 4. It consists of the following components: piston 2-1, piston ring 2-2, core valve assembly 1 and core valve assembly 2; core valve assembly 1 and core valve assembly 2 are both composed of spring 2-3, core valve 2-4 and adjustment screw 2-5. The assembly of core valve assembly 1 and core valve assembly 2 is that spring 2-3, core valve 2-4 and adjustment screw 2-5 are sequentially installed into the mounting hole of piston 2-1, and an initial preload is given to spring 2-3 by adjusting the adjustment screw 2-5. Since the adjustment screw 2-5 is continuously adjustable, it can stop at any position of the threaded section of the mounting hole of the piston as needed. There is no blocking torque between the adjustment screw 2-5 and the mounting hole thread of the piston 2-1, and tightening cannot be achieved. When the piston is reciprocating, the core valve 2-4 is often in a repeated opening and closing state, giving the adjustment screw 2-5 a variable load impact, which will cause the position of the adjustment screw 2-5 to move, and the initial force value of the spring 2-3 will also change, affecting the performance of the shock absorber. Since there is a gap between the threads of the adjusting screw 2-5 and the mounting hole of the piston 2-1, which cannot be eliminated during the assembly process, in order to prevent the adjusting screw from loosening, the current measure is to pre-coat an anaerobic thread locker 2-8 on the thread surface of the adjusting screw 2-5, and fill the thread gap after the adjusting screw 2-5 is screwed into the mounting hole of the piston 2-1. The thread locker is cured to generate a locking force, which can prevent loosening. However, there are several factors that affect the bonding effect of the thread locker in this piston unit structure: 1. The metal bonding area must be clean and must not have grease or other chemical components that are not conducive to bonding; 2. The amount of glue between the thread pairs; 3. Whether the thread locker is fully cured in an anaerobic environment before the piston unit is installed in the shock absorber.

[0004] The working principle of the piston unit of the above-mentioned glue coating structure is shown in Figure 5 When there is a pressure difference P between the oil at the left and right ends of the piston 2-1, the oil on the right side is forced to flow to the left end through the core valve 2-4. When the flow rate is small, the oil flows to the left through the small flow channel 2-4-1 of the core valve 2-4. When the flow rate is large, the small flow channel 2-4-1 on the core valve 2-4 is limited, and the spring 2-3 is compressed. The two end surfaces of the core valve 2-4 and the adjusting screw 2-5 are separated from the contact state and produce relative displacement. Most of the oil flows to the left through the large flow channel 2-4-2 on the core valve 2-4. When the pressure difference P disappears, the core valve 2-4 is closed. It can be seen that the right end face of the core valve 2-4 frequently gives an axial impact force to the left end face of the adjusting screw 2-5. If the thread pair is poorly bonded and subjected to continuous impact, the solid glue between the threads is squeezed into powder and loses the locking effect. The adjusting screw 2-5 will change position due to the loss of locking, which will cause the damping force of the shock absorber to change. Once the thread locker fails, in addition to causing the threads to loosen, the dust produced by the thread locker will also contaminate the oil, causing fluctuations in the damping force. In severe cases, it will aggravate the wear of the oil seal and reduce the service life of the shock absorber.

[0005] In addition, the shock absorber needs to be maintained many times during its life cycle, that is, after a certain period of operation, the vehicle parts are inspected and repaired. For the hydraulic shock absorber, the overall components are decomposed into parts, the wearing parts are replaced, and the parts that meet the requirements are cleaned and assembled again. The performance and life need to be restored to the new factory state. The most prominent failure phenomenon reflected in the actual operation of the shock absorber that has been overhauled twice or multiple times is the change in the damping performance of the shock absorber, because the adjustment screws 2-5 cannot be tightened. Although many maintenance manufacturers have tried their best, they still cannot reduce or eliminate the occurrence of such failures.

[0006] After observation and analysis, it is found that in addition to meeting the "three elements" of bonding, the repaired shock absorber piston unit and the newly manufactured piston unit have another factor that affects bonding, that is, there is more or less thread glue remaining on the surface of the disassembled piston and the adjustment screw, which cannot be removed completely by physical or chemical methods. The existence of residual glue affects the secondary bonding strength. Therefore, the problem of weak bonding of the adjustment screw is almost a common phenomenon and cannot be eliminated.

[0007] In summary, as a chemical product, thread locker can only play an auxiliary locking role in threaded connection and tightening, and cannot guarantee the reliability of thread locking. In particular, the threaded connection of the oil pressure shock absorber after maintenance is more unreliable, causing changes in the shock absorber performance.

[0008] In view of the above problems, some technicians have proposed a solution, namely a mechanical locking piston unit, see Figure 6, it adopts a glue-free "double nut tightening" method. This is a mechanical locking method, which achieves the purpose of tightening by adjusting the torque between the screw 2-5 and the locking screw 2-6. However, this structure brings another problem: when the adjusting screw 2-5 completes the adjustment task, due to the axial and radial clearances (small clearances) between the internal and external threads, the adjusting screw 2-5 is subjected to the pressure of the spring 2-3 (transmitted through the core valve 2-4), forcing the left thread of the adjusting screw 2-5 to disengage from the right thread of the piston hole 2-1 (at this time, the right thread of the adjusting screw 2-5 is in contact with the left thread of the piston hole 2-1). When the locking screw 2-6 is screwed in, when the left end of the locking screw 2-6 is in contact with the right end of the adjusting screw 2-5, on the one hand, the locking screw 2-6 forces the right thread of the adjusting screw 2-5 to disengage from the left thread of the piston hole 2-1, generating an axial forward trend, and on the other hand, the locking screw 2- When the left end of 6 contacts the right end of the adjusting screw 2-5, internal friction is generated, and the locking screw 2-6 drives the adjusting screw 2-5 to rotate. When the left thread of the adjusting screw 2-5 contacts and engages with the right thread of the piston hole 2-1, the friction generated is greater than the friction between the locking screw 2-6 and the adjusting screw 2-5. The adjusting screw 2-5 will stop rotating. By increasing the torque of the locking screw 2-6, the adjusting screw 2-5 is "locked" to achieve the effect of "double nuts tightened". Before being "locked", the adjusting screw 2-5 is rotated together with the locking screw 2-6, causing axial displacement changes. After tightening, the initial preload of the spring 2-3 is likely to have changed, resulting in changes in the shock absorber performance. Summary of the invention

[0009] The purpose of the present invention is to address the deficiencies of the prior art and to provide an oil pressure shock absorber piston unit and an assembly method thereof.

[0010] The present invention adopts the following technical solution:

[0011] The present invention discloses a hydraulic shock absorber piston unit, which is composed of a piston, a core valve assembly 1 and a core valve assembly 2; the end surface of the piston is provided with two or more mounting holes evenly distributed along the circumferential direction; the mounting hole is composed of a small-diameter section and a large-diameter section coaxially arranged; the tail of the large-diameter section is provided with an internal thread; each mounting hole is divided into two different orientations, wherein the core valve assembly 1 is arranged in the mounting holes in one orientation, and the core valve assembly 2 is arranged in the mounting holes in the other orientation.

[0012] The core valve assembly 1 and the core valve assembly 2 are both composed of a spring, a core valve, an adjusting screw, a locking screw and a gasket. The spring and the core valve are both placed in the mounting hole, and the two ends of the spring are axially limited by the inner end face of the boss of the core valve and the transition step between the small-diameter section and the large-diameter section respectively; the center hole of the adjusting screw and the outer cylindrical surface of the core valve form a sliding pair; the outer thread of the adjusting screw is connected with the inner thread of the tail of the large-diameter section, and the inner end face of the adjusting screw contacts the outer end face of the boss of the core valve; the outer end face of the adjusting screw is provided with an adjusting tool action structure; a large flow channel is opened at the position of the core valve near the boss; the inner side of the large flow channel is connected with the side wall of the center hole of the core valve, and the outer side is covered by the adjusting screw; the washer and the locking screw are both sleeved on the outer cylindrical surface of the core valve, and the washer is arranged between the adjusting screw and the locking screw; a radial gap is provided between the hole wall of the center hole of the locking screw and the outer cylindrical surface of the core valve, and a radial gap is also provided between the hole wall of the center hole of the washer and the outer cylindrical surface of the core valve; the surface roughness of the outer end face of the adjusting screw, the inner end face of the locking screw and the two end faces of the washer is not greater than 3.2; the outer end face of the locking screw is provided with an adjusting tool action structure.

[0013] Preferably, the gasket is made of carbon steel or spring steel.

[0014] Preferably, the piston is provided with a central hole, and the outer cylindrical surface is provided with one or more annular grooves; a piston ring is provided in the annular groove, and the piston ring is made of a friction-reducing material.

[0015] Preferably, the friction reducing material is polytetrafluoroethylene or cast iron.

[0016] Preferably, the adjustment tool action structure on the outer end surface of the adjustment screw is at least two circular holes or waist-shaped holes evenly distributed along the circumferential direction.

[0017] Preferably, the adjustment tool action structure on the outer end surface of the locking screw is at least two slots evenly distributed along the circumferential direction.

[0018] Preferably, the oil pressure shock absorber piston unit of the present invention is used as a bottom valve unit of the oil pressure shock absorber.

[0019] Preferably, the assembly method of the oil pressure shock absorber piston unit is as follows:

[0020] The core valve assembly 1 is installed in the mounting hole of the piston in one direction, and the core valve assembly 2 is installed in the mounting hole in the other direction. The specific installation process of installing the core valve assembly 1 or installing the core valve assembly 2 is as follows: first, the spring, the core valve and the adjusting screw are installed into the mounting hole of the piston in sequence, and the adjusting screw is sleeved on the outer cylindrical surface of the core valve, and the outer thread of the adjusting screw is connected with the inner thread at the tail end of the large-diameter section of the mounting hole; the adjusting screw is screwed into the preset position by a special adjusting tool to ensure the initial preload of the spring, at which time the two ends of the spring are axially limited by the inner end face of the boss of the core valve and the transition step between the small-diameter section and the large-diameter section, and the inner end face of the adjusting screw is in contact with the outer end face of the boss of the core valve; then, a washer and a locking screw are sleeved on the outer cylindrical surface of the core valve, and the outer thread of the locking screw is connected with the inner thread at the tail end of the large-diameter section of the mounting hole; when the locking screw is screwed into the compression washer by a special adjusting tool Stop, so that the inner end face of the locking screw contacts the outer end face of the adjusting screw, and the outer end face of the washer contacts the inner end face of the locking screw; in the process of the locking screw pressing the washer, since the outer end face of the adjusting screw, the inner end face of the locking screw and the two end faces of the washer are all smoothed, the friction coefficient between the outer thread of the adjusting screw and the inner thread of the large-diameter section at the end of the piston's mounting hole is greater than the friction coefficient between the inner end face of the washer and the outer end face of the adjusting screw, as well as between the outer end face of the washer and the inner end face of the locking screw. Therefore, under the same positive pressure, the friction force between the outer thread of the adjusting screw and the inner thread of the large-diameter section at the end of the piston's mounting hole is greater than the friction force between the inner end face of the washer and the outer end face of the adjusting screw, as well as between the outer end face of the washer and the inner end face of the locking screw. No matter how much torque is applied to the locking screw, the locking screw cannot drive the adjusting screw to rotate, and the initial preload of the spring will not change.

[0021] The present invention has the beneficial effects:

[0022] 1. The present invention processes the end surfaces of the adjusting screw and the locking screw and adds a washer. After a tightening torque is applied to the adjusting screw, the locking screw axially presses the adjusting screw through the washer. Since the friction between the external thread of the adjusting screw and the internal thread of the tail of the large-diameter section of the mounting hole of the piston is greater than the friction between the inner end surface of the washer and the external end surface of the adjusting screw and the friction between the outer end surface of the washer and the inner end surface of the locking screw, no matter how much torque is applied to the locking screw, the locking screw cannot drive the adjusting screw to rotate, thereby ensuring that the initial preload of the spring does not change, ensuring the stability of the damping performance of the shock absorber, and avoiding the situation in which the initial preload of the spring changes due to the rotation of the adjusting screw in the existing "double-nut tightening" method.

[0023] 2. Compared with the existing "double nut tightening" method, the present invention can also improve the anti-loosening effect and further ensure the stability of the shock absorber performance.

[0024] 3. The present invention eliminates the thread gluing process, thereby reducing the risk of thread loosening due to insufficient or ineffective adhesive strength; reducing the risk of oil contamination due to residual glue or colloidal powder, which is beneficial to improving or extending the service life of the shock absorber. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural cross-sectional view of the dual-circulation oil pressure shock absorber during the stretching process;

[0026] Figure 2 It is a structural cross-sectional view of the dual-circulation oil pressure shock absorber during the compression process;

[0027] Figure 3 It is a structural cross-sectional view of the piston unit with glue applied on the surface of the adjusting screw;

[0028] Figure 4 The end face diagram of the piston unit with glue applied on the surface of the adjusting screw;

[0029] Figure 5 The working principle diagram of the piston unit with glue applied on the surface of the adjusting screw;

[0030] Figure 6 It is a structural cross-sectional view of a double-nut tight piston unit;

[0031] Figure 7 It is a structural cross-sectional view of the piston unit of the present invention;

[0032] Figure 8 It is a schematic end view of the piston unit of the present invention. DETAILED DESCRIPTION

[0033] The present invention is described in detail below with reference to the accompanying drawings.

[0034] Embodiment 1:

[0035] like Figure 7 and 8 As shown, a hydraulic shock absorber piston unit is composed of a piston 2-1, a core valve assembly 1 21 and a core valve assembly 22; the end surface of the piston 2-1 is provided with more than two mounting holes evenly distributed along the circumferential direction; the mounting holes are composed of a small-diameter section and a large-diameter section coaxially arranged; the tail of the large-diameter section is provided with an internal thread; each mounting hole is divided into two different orientations, and the core valve assembly 1 21 is arranged in the mounting holes in one orientation, and the core valve assembly 2 22 is arranged in the mounting holes in the other orientation.

[0036] The core valve assembly 1 21 and the core valve assembly 2 22 are both composed of a spring 2-3, a core valve 2-4, an adjusting screw 2-5, a locking screw 2-6 and a washer 2-7. The spring 2-3 and the core valve 2-4 are both placed in the mounting hole, and the two ends of the spring 2-3 are axially limited by the inner end face of the boss of the core valve 2-4 and the transition step between the small aperture section and the large aperture section, so that the spring 2-3 is provided with a pre-pressure; the center hole of the adjusting screw 2-5 and the outer cylindrical surface of the core valve 2-4 form a sliding pair, which is convenient for axial sliding and preventing oil leakage; the outer thread of the adjusting screw 2-5 is connected to the inner thread of the tail of the large aperture section, and the inner end face of the adjusting screw 2-5 contacts the outer end face of the boss of the core valve 2-4; the outer end face of the adjusting screw 2-5 is provided with an adjusting tool action structure, which is convenient for adjusting the axial position of the adjusting screw 2-5 in the mounting hole; the core valve 2 -4 is provided with a large flow channel 2-4-2 near the boss position; the inner side of the large flow channel 2-4-2 is connected with the side wall of the center hole of the core valve 2-4, and the outer side is covered by the adjusting screw 2-5; the washer 2-7 and the locking screw 2-6 are both sleeved on the outer cylindrical surface of the core valve 2-4, and the washer 2-7 is arranged between the adjusting screw 2-5 and the locking screw 2-6; a radial gap is provided between the wall of the center hole of the locking screw 2-6 and the outer cylindrical surface of the core valve 2-4 to ensure that there is no contact or interference between the two at any time; a radial gap is also provided between the wall of the center hole of the washer 2-7 and the outer cylindrical surface of the core valve 2-4 to ensure that there is no contact or interference between the two at any time. In order to prevent the locking screw 2-6 from driving the adjusting screw 2-5 to rotate together when tightening, causing the initial preload of the spring 2-3 to change, the surface roughness of the outer end face of the adjusting screw 2-5, the inner end face of the locking screw 2-6 and the two end faces of the washer 2-7 is not greater than 3.2, so as to ensure that the above end faces are smooth and reduce the friction between the two end faces in contact with each other; and the washer 2-7 must be made of hard material with a certain wear resistance, such as carbon steel, spring steel, etc. The outer end face of the locking screw 2-6 is provided with an adjustment tool action structure, which is convenient for applying torque when tightening.

[0037] As a more preferred embodiment, the core valve 2-4 is further provided with a small flow channel 2-4-1; the inner side of the small flow channel 2-4-1 is connected to the side wall of the center hole of the core valve 2-4.

[0038] The working principle of the piston unit of the oil pressure shock absorber in this embodiment is consistent with the working principle of the piston unit of the above-mentioned rubber coating structure, and will not be repeated here.

[0039] Embodiment 2:

[0040] Based on the first embodiment, the piston 2-1 is provided with a center hole, and the outer cylindrical surface is provided with one or more annular grooves; a piston ring 2-2 is provided in the annular groove, and the piston ring 2-2 is made of a friction-reducing material.

[0041] Embodiment three:

[0042] Based on the first or second embodiment, the adjusting tool action structure on the outer end surface of the adjusting screw 2-5 is at least two circular holes or waist-shaped holes evenly distributed along the circumferential direction.

[0043] Embodiment 4:

[0044] Based on the first or second embodiment, the adjustment tool action structure on the outer end surface of the locking screw 2-6 is at least two slots evenly distributed along the circumferential direction.

[0045] Embodiment five:

[0046] Based on any of the above embodiments, the assembly method of the oil pressure shock absorber piston unit is as follows:

[0047] The core valve assembly 1 21 is installed in one of the mounting holes of the piston 2-1, and the core valve assembly 2 22 is installed in the other mounting hole. The specific installation process of installing the core valve assembly 1 21 or installing the core valve assembly 2 22 is: sequentially install the spring 2-3, the core valve 2-4 and the adjusting screw 2-5 into the mounting hole of the piston 2-1, and the adjusting screw 2-5 is sleeved on the outer cylindrical surface of the core valve 2-4, and the external thread of the adjusting screw 2-5 is connected with the internal thread at the tail of the large-diameter section of the mounting hole; through a special adjustment tool (matching the adjustment tool action structure of the adjustment screw 2-5) Screw the adjusting screw 2-5 into the preset position to ensure the initial preload of the spring 2-3. At this time, the two ends of the spring 2-3 are axially limited by the inner end face of the boss of the core valve 2-4 and the transition step between the small-diameter section and the large-diameter section, and the inner end face of the adjusting screw 2-5 contacts the outer end face of the boss of the core valve 2-4. Then, the washer 2-7 and the locking screw 2-6 are sleeved on the outer cylindrical surface of the core valve 2-4, and the outer thread of the locking screw 2-6 is connected to the inner thread at the tail of the large-diameter section of the mounting hole. Use a special adjusting tool (matching the adjusting tool action structure of the locking screw 2-6) to tighten the locking screw. When the locking screw 2-6 is screwed into the compression washer 2-7, it stops, so that the inner end face of the locking screw 2-6 contacts the outer end face of the adjusting screw 2-5, and the outer end face of the washer 2-7 contacts the inner end face of the locking screw 2-6; in the process of the locking screw 2-6 compressing the washer 2-7, since the outer end face of the adjusting screw 2-5, the inner end face of the locking screw 2-6 and the two end faces of the washer 2-7 are all smoothed, the friction coefficient between the outer thread of the adjusting screw 2-5 and the inner thread at the tail of the large-diameter section of the mounting hole of the piston 2-1 is greater than the friction coefficient between the inner end face of the washer 2-7 and the outer end face of the adjusting screw 2-5 and the washer The friction coefficient between the outer end face of 2-7 and the inner end face of the locking screw 2-6. Therefore, under the same positive pressure condition, the friction between the outer thread of the adjusting screw 2-5 and the inner thread of the tail of the large-diameter section of the mounting hole of the piston 2-1 is greater than the friction between the inner end face of the washer 2-7 and the outer end face of the adjusting screw 2-5 and the friction between the outer end face of the washer 2-7 and the inner end face of the locking screw 2-6. No matter how much torque is applied to the locking screw 2-6, the locking screw 2-6 cannot drive the adjusting screw 2-5 to rotate, thereby ensuring that the initial preload of the spring 2-3 does not change.

[0048] Moreover, compared with the "double nut tightening" method, the present invention has a better anti-loosening effect, and the principle is consistent with the principle that the locking screw 2-6 cannot drive the adjusting screw 2-5 to rotate, that is, the adjusting screw 2-5 cannot drive the locking screw 2-6 to rotate.

[0049] After the piston unit of the oil pressure shock absorber of the present invention is assembled, it can be further assembled into the cylinder body of the oil pressure shock absorber for use.

Claims

1. A hydraulic shock absorber piston unit, comprising a piston, a core valve assembly 1 and a core valve assembly 2; the end surface of the piston is provided with two or more mounting holes evenly distributed along the circumferential direction; the mounting hole is composed of a small-diameter section and a large-diameter section coaxially arranged; the tail of the large-diameter section is provided with an internal thread; each mounting hole is divided into two different orientations, wherein the core valve assembly 1 is arranged in the mounting holes in one orientation, and the core valve assembly 2 is arranged in the mounting holes in the other orientation; the characteristics are: The core valve assembly 1 and the core valve assembly 2 are both composed of a spring, a core valve, an adjusting screw, a locking screw and a washer; the spring and the core valve are both placed in the mounting hole, and the two ends of the spring are axially limited by the inner end face of the boss of the core valve and the transition step between the small aperture section and the large aperture section respectively; the center hole of the adjusting screw and the outer cylindrical surface of the core valve form a sliding pair; the outer thread of the adjusting screw is connected to the inner thread of the tail of the large aperture section, and the inner end face of the adjusting screw contacts the outer end face of the boss of the core valve; the outer end face of the adjusting screw is provided with an adjusting tool action structure; the core valve is located near the boss A large flow channel is provided; the inner side of the large flow channel is connected to the side wall of the center hole of the core valve, and the outer side is covered by the adjusting screw; the washer and the locking screw are both sleeved on the outer cylindrical surface of the core valve, and the washer is arranged between the adjusting screw and the locking screw; a radial gap is provided between the hole wall of the center hole of the locking screw and the outer cylindrical surface of the core valve, and a radial gap is also provided between the hole wall of the center hole of the washer and the outer cylindrical surface of the core valve; the surface roughness of the outer end surface of the adjusting screw, the inner end surface of the locking screw and the two end surfaces of the washer is not greater than 3.2; the outer end surface of the locking screw is provided with an adjusting tool action structure; The piston is provided with a central hole, and the outer cylindrical surface is provided with one or more annular grooves; a piston ring is provided in the annular groove, and the piston ring is made of a friction-reducing material; The friction between the external thread of the adjusting screw and the internal thread at the tail of the large-diameter section of the mounting hole of the piston is greater than the friction between the inner end face of the washer and the outer end face of the adjusting screw and the friction between the outer end face of the washer and the inner end face of the locking screw; The core valve (2-4) is also provided with a small flow channel (2-4-1); the inner side of the small flow channel (2-4-1) is in communication with the side wall of the central hole of the core valve (2-4).

2. The oil pressure shock absorber piston unit according to claim 1, characterized in that: The material of the gasket is carbon steel or spring steel.

3. The oil pressure shock absorber piston unit according to claim 1, characterized in that: The friction-reducing material is polytetrafluoroethylene or cast iron.

4. A hydraulic shock absorber piston unit according to claim 1, 2 or 3, characterized in that: The adjusting tool action structure on the outer end surface of the adjusting screw is at least two circular holes or waist-shaped holes evenly distributed along the circumferential direction.

5. The oil pressure shock absorber piston unit according to claim 1, 2 or 3, characterized in that: The adjusting tool action structure on the outer end surface of the locking screw is at least two slots evenly distributed along the circumferential direction.

6. A hydraulic shock absorber piston unit according to claim 1, 2 or 3, characterized in that: Used as a bottom valve unit for hydraulic shock absorbers.

7. The method for assembling a hydraulic shock absorber piston unit according to claim 1, 2 or 3, characterized in that: The method is as follows: The core valve assembly 1 is installed in the mounting hole of the piston in one direction, and the core valve assembly 2 is installed in the mounting hole in the other direction. The specific installation process of installing the core valve assembly 1 or installing the core valve assembly 2 is as follows: first, the spring, the core valve and the adjusting screw are installed into the mounting hole of the piston in sequence, and the adjusting screw is sleeved on the outer cylindrical surface of the core valve, and the outer thread of the adjusting screw is connected with the inner thread at the tail end of the large-diameter section of the mounting hole; the adjusting screw is screwed into the preset position by a special adjusting tool to ensure the initial preload of the spring, at which time the two ends of the spring are axially limited by the inner end face of the boss of the core valve and the transition step between the small-diameter section and the large-diameter section, and the inner end face of the adjusting screw is in contact with the outer end face of the boss of the core valve; then, a washer and a locking screw are sleeved on the outer cylindrical surface of the core valve, and the outer thread of the locking screw is connected with the inner thread at the tail end of the large-diameter section of the mounting hole; when the locking screw is screwed into the compression washer by a special adjusting tool Stop, so that the inner end face of the locking screw contacts the outer end face of the adjusting screw, and the outer end face of the washer contacts the inner end face of the locking screw; in the process of the locking screw pressing the washer, since the outer end face of the adjusting screw, the inner end face of the locking screw and the two end faces of the washer are all smoothed, the friction coefficient between the outer thread of the adjusting screw and the inner thread of the large-diameter section at the end of the piston's mounting hole is greater than the friction coefficient between the inner end face of the washer and the outer end face of the adjusting screw, as well as between the outer end face of the washer and the inner end face of the locking screw. Therefore, under the same positive pressure, the friction force between the outer thread of the adjusting screw and the inner thread of the large-diameter section at the end of the piston's mounting hole is greater than the friction force between the inner end face of the washer and the outer end face of the adjusting screw, as well as between the outer end face of the washer and the inner end face of the locking screw. No matter how much torque is applied to the locking screw, the locking screw cannot drive the adjusting screw to rotate, and the initial preload of the spring will not change.

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