Piston for oil-free piston air compressor and method for manufacturing the same

Abstract

The application discloses an oil-free piston air compressor piston and a manufacturing method thereof. The piston body of the oil-free piston air compressor piston comprises a metal body and a wear-resistant self-lubricating sleeve without welding lines. A piston ring is sleeved in a piston ring clamping groove on the outer circumferential wall of one end of the metal body. An internal thread structure on the inner wall of the wear-resistant self-lubricating sleeve is tightly screwed and positioned with an external thread structure on the outer circumferential wall of the other end of the metal body. The manufacturing method comprises the following steps: firstly, the metal body and the wear-resistant self-lubricating sleeve without welding lines are manufactured; secondly, the wear-resistant self-lubricating sleeve is preheated and expanded, and then is assembled to the outer side of the metal piston body; thirdly, the wear-resistant self-lubricating sleeve and the metal piston body assembly are processed with radial perforation after cooling; and finally, the piston ring and the piston rod are assembled. The metal body and the wear-resistant self-lubricating sleeve are combined firmly, the wear-resistant self-lubricating sleeve is not prone to wear and tear and cracking during long-term use, the service life of the oil-free piston air compressor piston is guaranteed, and the use cost is reduced.

Description

Technical Field

[0001] This invention relates to the technical field of an oil-free piston air compressor, and in particular to an oil-free piston air compressor piston and its manufacturing method. Background Technology

[0002] Oil-free reciprocating piston air compressors are widely used in clean air supply applications such as automotive, medical, food, electronics, and textiles. The piston and cylinder are the core friction pair, and traditional structures have the following drawbacks:

[0003] 1. The pistons are manufactured using a glue-bonding process, which is prone to bulging, resulting in low yield and high manufacturing costs. Poor adhesion of the self-lubricating material leads to delamination after 2-3 months of use, causing cylinder scoring during operation. Under high-temperature conditions, the coating softens and deforms, resulting in a short lifespan and frequent maintenance. Currently, glue-bonded pistons generally exhibit significant wear, abnormal noise, and high noise levels after 2-3 years of use, failing to meet the 8-year warranty requirement.

[0004] 2. The piston is made using an injection molding process. Because the plastic and the metal piston are not adhesive, multiple complex dovetail grooves need to be machined on the surface of the metal piston to prevent the plastic from falling off. This results in uneven wall thickness of the plastic coating. Under high temperature conditions, the plastic surface expands unevenly, leading to rapid piston wear. During the injection molding process, due to the influence of the piston body structure, the glue can only be injected from the side of the piston, resulting in obvious weld lines. The strength at the weld line is only 20% of the plastic's performance, making it prone to cracking under high and low temperature conditions.

[0005] Furthermore, pistons manufactured using either of the above two processes are single-use products. Once the coating is damaged, they must be scrapped, and the piston pump body cannot be repaired and used again. Summary of the Invention

[0006] To overcome the above-mentioned defects, the present invention provides an oil-free piston air compressor piston and its manufacturing method. The metal body and wear-resistant self-lubricating sleeve of the oil-free piston air compressor piston are firmly combined without weld lines, and are wear-resistant, friction-reducing, and stable and reliable in use.

[0007] The technical solution adopted by the present invention to solve its technical problem is as follows: an oil-free piston air compressor piston, comprising a piston body and piston rings. The piston body includes a metal body and a wear-resistant self-lubricating sleeve without weld lines. A piston ring groove is provided on the outer circumference of one end of the metal body, and the piston ring is fitted into the piston ring groove of the metal body in an embedded state. An external thread structure is formed on the outer circumference of the other end of the metal body. An internal thread structure is provided on the inner sidewall of the wear-resistant self-lubricating sleeve. The internal thread structure of the wear-resistant self-lubricating sleeve is tightly screwed and positioned with the external thread structure of the metal body.

[0008] As a further improvement of the present invention, a piston pin and a piston rod are also provided. An axially extending piston rod slot is provided on the inner side of the other end of the metal body. One end of the piston rod can be inserted into the piston rod slot. The metal body, the wear-resistant self-lubricating sleeve, and one end of the piston rod are respectively provided with a radially penetrating first piston pin hole, a second piston pin hole, and a third piston pin hole. The first piston pin hole, the second piston pin hole, and the third piston pin hole are directly opposite and connected. The piston pin can be fixedly inserted into the first piston pin hole, the second piston pin hole, and the third piston pin hole to fix the piston rod to the piston body.

[0009] As a further improvement of the present invention, the wear-resistant self-lubricating sleeve is a PEEK sleeve, a PTFE sleeve, a graphite-added PEEK sleeve, a graphite-added PTFE sleeve, a carbon fiber-added PEEK sleeve, or a carbon fiber-added PTFE sleeve.

[0010] As a further improvement of the present invention, the internal thread structure of the wear-resistant self-lubricating sleeve is a single-start or multi-start thread, the thread pitch is 0.5-5 mm, and the thread depth is 0.4-1.5 mm.

[0011] As a further improvement of the present invention, a plurality of vent holes are provided on the end face of one end of the metal body. The vent holes are connected to the piston rod slot. The piston body also includes a metal valve plate. The metal valve plate is installed on one end face of the metal body and covers the opening of one end of the vent hole. The metal valve plate can seal the opening of one end of the vent hole under the action of the air pressure inside the cylinder of the air compressor.

[0012] As a further improvement of the present invention, a threaded hole is provided at the center of the end face of one end of the metal body, and a screw and a set of anti-loosening washers are also provided. A connecting through hole is provided at the center of the metal valve plate. The screw passes through the loosening washer set and the connecting through hole of the metal valve plate and is screwed and fixed to the threaded hole at one end of the metal body. The metal valve plate can be deformed by the air pressure on both sides of the axis and repeatedly hit the end face of one end of the metal body.

[0013] As a further improvement of the present invention, at least one annular noise reduction groove is provided on the end face of one end of the metal body, and the metal valve plate covers the opening surface of the annular noise reduction groove.

[0014] A method for manufacturing an oil-free piston air compressor piston includes the following steps:

[0015] Step 1: Fabricate a metal body with piston rod slots and piston ring slots, and then machine an external thread structure on the outer circumference of the metal body;

[0016] Step 2: Use wear-resistant and self-lubricating materials to make wear-resistant and self-lubricating sleeves, and machine internal thread structure on the inner side of the wear-resistant and self-lubricating sleeves;

[0017] Step 3: Preheat and expand the wear-resistant self-lubricating sleeve;

[0018] Step 4: Install the preheated and expanded wear-resistant self-lubricating sleeve onto the outside of the metal piston body through thread engagement;

[0019] Step 5: Cool the wear-resistant self-lubricating sleeve assembled on the outside of the metal piston body, so that the wear-resistant self-lubricating sleeve is fixedly attached to the outer circumferential surface of the metal piston body.

[0020] Step 6: Machining radial perforations to form the first piston pin hole and the second piston pin hole on the wear-resistant self-lubricating sleeve and metal piston body assembly;

[0021] Step 7: Assemble the piston rings into the piston ring slots on the outer side of one end of the metal piston body;

[0022] Step 8: Insert one end of the piston rod into the piston rod slot at the other end of the metal piston body, and then insert the piston pin into the first piston pin hole, the second piston pin hole, and the third piston pin hole to assemble and position the piston rod with the piston body.

[0023] As a further improvement of the present invention, the temperature for preheating the wear-resistant self-lubricating sleeve in the third step is 100-300°C.

[0024] As a further improvement of the present invention, in the second step of processing the wear-resistant self-lubricating sleeve, injection-molded tubing material without weld lines or extruded profile tubing material without weld lines is used for circumferential outer surface finishing and internal hole tapping. The interference fit between the threads of its internal thread structure and the external thread structure on the metal piston body is 0 to 0.4 mm.

[0025] The beneficial effects of this invention are as follows: This invention assembles the wear-resistant self-lubricating sleeve onto the outer circumference of the metal body via threaded engagement. Preheating expansion allows the wear-resistant self-lubricating sleeve to be easily screwed onto the outer circumference of the metal body. After cooling, the wear-resistant self-lubricating sleeve shrinks, achieving an interference fit with the metal body and remaining fixed in place. This structure is simple, the wear-resistant self-lubricating sleeve is firmly bonded to the metal body, eliminating the need for complex injection molding molds and adhesives. Furthermore, the overall wall thickness of the wear-resistant self-lubricating sleeve is highly consistent, preventing uneven wall thickness under hot and cold environments, ensuring uniform wall thickness in any environment, and providing wear-resistant self-lubrication. The sheath is manufactured from weld-free tubing, preventing cracking of the wear-resistant self-lubricating sheath under high and low temperature conditions. Made from wear-resistant and self-lubricating materials, it offers wear-resistant and friction-reducing effects, resisting wear and damage even after long-term use. This ensures the long-term stability and reliability of the oil-free piston air compressor piston and guarantees the service life of the oil-free piston air compressor cylinder, meeting the 8-year warranty requirement. If wear occurs after long-term use, the wear-resistant self-lubricating sheath can be expanded by heating and then replaced. This allows the piston to be repaired by replacing the wear-resistant self-lubricating sheath, reducing piston usage costs. Attached Figure Description

[0026] Figure 1 This is a front view of the piston body of the present invention;

[0027] Figure 2 for Figure 1 Sectional view along line AA;

[0028] Figure 3 for Figure 2 Enlarged view of section B;

[0029] Figure 4 This is a front view of the piston body and piston ring assembly of the present invention;

[0030] Figure 5 for Figure 4 C-axis sectional view;

[0031] Figure 6 This is an exploded perspective view of the assembly principle of the piston body and metal valve plate of the present invention.

[0032] Figure 7 This is a cross-sectional view of the assembly principle of the piston body and metal valve plate of the present invention;

[0033] Figure 8 This is a schematic diagram of the piston structure of the present invention;

[0034] Figure 9 This is a diagram showing the piston of the present invention installed in the cylinder body. Detailed Implementation

[0035] To make the advantages, technical solutions, and innovations of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the protection scope of this invention.

[0036] Example: An oil-free piston air compressor piston includes a piston body 1 and piston rings 2. The piston body 1 includes a metal body 11 and a wear-resistant self-lubricating sleeve 12 without weld lines. A piston ring groove 111 is provided on the outer circumference of one end of the metal body 11. The piston ring 2 is fitted into the piston ring groove 111 of the metal body 11 in an embedded state. An external thread structure 112 is formed on the outer circumference of the other end of the metal body 11. An internal thread structure 121 is provided on the inner sidewall of the wear-resistant self-lubricating sleeve. The internal thread structure 121 of the wear-resistant self-lubricating sleeve 12 is tightly screwed and positioned with the external thread structure 112 of the metal body 11.

[0037] The metal body 11 of the piston body 1 and the wear-resistant self-lubricating sleeve 12 are connected by a tight threaded engagement to form an integral structure. This structure avoids the use of glue bonding and ensures that the wall thickness of the wear-resistant self-lubricating sleeve 12 is uniform. This ensures that the outer diameter of the piston body 1 remains consistent even when exposed to temperature changes during use, preventing bulging, deformation, or other issues. This ensures that the piston body 1 will not be damaged during long-term use and will not wear down the air compressor cylinder. Furthermore, this connection method between the metal body 11 and the wear-resistant self-lubricating sleeve 12 is simple in structure, has low production cost, and good bonding stability, thus reducing the production cost of the piston body 1. After the wear-resistant self-lubricating sleeve 12 wears out, it can be removed from the metal body 11 for replacement, so that the piston does not have to be scrapped due to the wear of the wear-resistant self-lubricating sleeve 12, thereby reducing the piston's operating cost.

[0038] The system also includes a piston pin 3 and a piston rod 4. The inner side of the other end of the metal body 11 is provided with an axially extending piston rod slot 113. One end of the piston rod 4 can be inserted into the piston rod slot 113. The metal body 11, the wear-resistant self-lubricating sleeve 12, and one end of the piston rod 4 are respectively provided with a radially penetrating first piston pin hole 114, a second piston pin hole 122, and a third piston pin hole 41. The first piston pin hole 114, the second piston pin hole 122, and the third piston pin hole 41 are directly opposite and connected. The piston pin 3 can be fixedly inserted into the first piston pin hole 114, the second piston pin hole 122, and the third piston pin hole 41 to fix the piston rod 4 to the piston body 1.

[0039] By setting a piston rod slot 113 on the metal body 11 to insert one end of the piston rod 4, and then using the piston pin 3 to rivet and fix the piston rod 4 to the piston body 1, the piston rod 4 and the piston body 1 are quickly assembled and the assembly is convenient. The outer circumference of both ends of the piston pin 3 is provided with radial protruding rings, and the inner sidewalls of both ends of the first piston pin hole 114 are provided with corresponding radial concave rings. After the piston pin 3 is riveted in, the radial protruding rings at both ends are stuck in the radial concave rings on the inner sidewalls of both ends of the first piston pin hole 114, thereby achieving axial positioning of the piston pin 3 and preventing the piston pin 3 from falling off due to vibration.

[0040] The wear-resistant self-lubricating sleeve is made of PEEK, PTFE, graphite-added PEEK, graphite-added PTFE, carbon fiber-added PEEK, or carbon fiber-added PTFE. The wear-resistant self-lubricating sleeve uses PEEK or PTFE as the main material, and graphite or carbon fiber can be added to effectively improve its wear resistance and lubrication. This type of wear-resistant self-lubricating sleeve can withstand high and low temperature environmental changes and is not easily damaged. Alternatively, the material can be a mixture of PEEK and PTFE as the main material, with a mixture of graphite and carbon fiber as an additive. Different performance characteristics of wear-resistant self-lubricating sleeves can be obtained through different component matching.

[0041] The internal thread structure 121 of the wear-resistant self-lubricating sleeve is a single-start or multi-start thread with a thread pitch of 0.5-5 mm and a thread depth of 0.4-1.5 mm. The external thread structure 112 on the outer circumference of the other end of the metal body 11 can be matched with the internal thread structure 121 of the wear-resistant self-lubricating sleeve.

[0042] The end face of one end of the metal body 11 is provided with a plurality of vent holes 115. The vent holes 115 are connected to the piston rod slot 113. The piston body 1 also includes a metal valve plate 5. The metal valve plate 5 is installed on one end face of the metal body 11. The metal valve plate 5 covers the opening of one end of the vent hole 115. The metal valve plate 5 can seal the opening of one end of the vent hole 115 under the action of the air pressure in the cylinder of the air compressor. By installing a metal valve plate 5 at one end of the metal body 11 of the piston body 1, and providing several vent holes 115 communicating with the piston rod slot 113 on the end face of one end of the metal body 11, a one-way channel is formed between the vent holes 115 and the metal valve plate 5. When the cylinder body 8 is in a compressed air state, the metal valve plate 5 closes the vent holes 115, so that the cylinder can work stably. When air needs to be introduced into the cylinder, the external piston can make the air flow into the cylinder quickly, reduce the air extraction resistance, increase the air intake speed, and thus improve the working efficiency of the air compressor cylinder.

[0043] The metal body 11 has a threaded hole 116 at the center of one end face, and also has a screw 6 and a set of anti-loosening washers 7. The metal valve plate 5 has a connecting through hole 51 at the center. The screw 6 passes through the loosening washer set and the connecting through hole 51 of the metal valve plate 5 and is screwed and fixed to the threaded hole 116 at one end of the metal body 11. The metal valve plate 5 can be deformed by the air pressure on both sides of the axis and repeatedly hit the end face of one end of the metal body 11. The metal valve plate 5 is locked to the end face of one end of the metal body 11 by screws 6. Since the metal valve plate 5 is relatively thin, it can deform under axial force. In order to improve the deformation ability of the metal valve plate 5, some grooves can be formed on the metal valve plate 5. These grooves are misaligned with the vent hole 115. This does not affect the sealing of the vent hole 115 and can also ensure that the metal valve plate 5 can deform smoothly. During the reciprocating motion of the piston rod 4 of the air compressor, the metal valve plate 5 continuously hits the end face of one end of the metal body 11, thereby forming the sealing and opening of the vent hole 115.

[0044] At least one annular noise reduction groove 117 is provided on the end face of one end of the metal body 11, and the metal valve plate 5 covers the opening surface of the annular noise reduction groove 117. By providing the annular noise reduction groove 117 on the end face of one end of the metal body 11, the contact area when the metal valve plate 5 hits the end face of the metal body is reduced, and an air cavity can be formed to buffer the metal valve plate 5, thereby reducing the noise generated by the metal valve plate 5 hitting the metal body 11.

[0045] A method for manufacturing an oil-free piston air compressor piston includes the following steps:

[0046] Step 1: Fabricate a metal body 11 with a piston rod slot 113 and a piston ring groove 111, and then machine an external thread structure 112 on the outer circumference of the metal body 11;

[0047] Step 2: Use wear-resistant and self-lubricating materials to make wear-resistant and self-lubricating sleeves. It is best to use injection-molded pipe material or extruded profile material without weld lines. After precision machining of the outer circumference, tap the inner side of the wear-resistant and self-lubricating sleeve to process the internal thread structure 121. The interference fit between the thread of the internal thread structure 121 and the external thread structure 112 on the metal piston body is 0 to 0.4 mm.

[0048] Step 3: Preheat and expand the wear-resistant self-lubricating sleeve at a temperature of 100-300℃.

[0049] Step 4: Install the preheated and expanded wear-resistant self-lubricating sleeve onto the outside of the metal piston body through thread engagement;

[0050] Step 5: Cool the wear-resistant self-lubricating sleeve assembled on the outside of the metal piston body, so that the wear-resistant self-lubricating sleeve is fixedly attached to the outer circumferential surface of the metal piston body.

[0051] Step 6: Machining radial perforations to form the first piston pin hole 114 and the second piston pin hole 122 on the wear-resistant self-lubricating sleeve and metal piston body assembly;

[0052] Step 7: Assemble the piston ring 2 into the piston ring groove 111 on the outer side of one end of the metal piston body;

[0053] Step 8: Insert one end of the piston rod 4 into the piston rod slot 113 at the other end of the metal piston body, and then insert the piston pin 3 into the first piston pin hole 114, the second piston pin hole 122 and the third piston pin hole 41 to achieve the assembly and positioning of the piston rod 4 and the piston body 1.

[0054] The metal body 11 can be machined or die-cast first, and then have an external thread structure 112 machined on its outer circumference. Using weld-line-free tubing to manufacture the wear-resistant self-lubricating sleeve reduces manufacturing costs and avoids weld lines on the side of the sleeve, improving its strength and preventing cracking during use. Alternatively, the wear-resistant self-lubricating sleeve can be injection molded and then have the threads and outer circumference machined. The specific manufacturing method can be selected according to needs. After the metal body 11 and the wear-resistant self-lubricating sleeve are processed, since both are ultimately... An interference fit is required. Therefore, the wear-resistant self-lubricating sleeve is first preheated to expand it. Then, in the expanded state, it can be smoothly assembled onto the metal body 11. After assembly, the wear-resistant self-lubricating sleeve cools and shrinks, firmly bonding to the surface of the metal body 11 without falling off. This assembly method avoids damage to the wear-resistant self-lubricating sleeve and is convenient and quick to assemble. After assembly, the two are firmly bonded. After assembling the wear-resistant self-lubricating sleeve onto the surface of the metal body 11, the first piston pin hole 114 and the second piston pin hole 122 are machined once to ensure that the two are coaxial and aligned, which facilitates the assembly of the piston pin rod 3.

Claims

1. An oil-free piston air compressor piston, comprising a piston body (1) and piston rings (2), characterized in that: The piston body includes a metal body (11) and a wear-resistant self-lubricating sleeve (12) without fusion lines. A piston ring groove (111) is provided on the outer circumference of one end of the metal body. The piston ring is fitted into the piston ring groove of the metal body in an embedded state. An external thread structure (112) is formed on the outer circumference of the other end of the metal body. An internal thread structure (121) is provided on the inner sidewall of the wear-resistant self-lubricating sleeve. The internal thread structure of the wear-resistant self-lubricating sleeve is tightly screwed and positioned with the external thread structure of the metal body.

2. The oil-free piston air compressor piston according to claim 1, characterized in that: It is also provided with a piston pin (3) and a piston rod (4). The inner side of the other end of the metal body is provided with an axially extending piston rod slot (113). One end of the piston rod can be inserted into the piston rod slot. The metal body, the wear-resistant self-lubricating sleeve and one end of the piston rod are respectively provided with a first piston pin hole (114), a second piston pin hole (122) and a third piston pin hole (41) that penetrate radially. The first piston pin hole, the second piston pin hole and the third piston pin hole are directly connected. The piston pin can be fixedly inserted into the first piston pin hole, the second piston pin hole and the third piston pin hole to fix the piston rod to the piston body.

3. The oil-free piston air compressor piston according to claim 1, characterized in that: The wear-resistant self-lubricating sleeve is a PEEK sleeve, a PTFE sleeve, a graphite-added PEEK sleeve, a graphite-added PTFE sleeve, a carbon fiber-added PEEK sleeve, or a carbon fiber-added PTFE sleeve.

4. The oil-free piston air compressor piston according to claim 1, characterized in that: The wear-resistant self-lubricating sleeve has an internal thread structure of single-start or multi-start thread, with a thread pitch of 0.5-5 mm and a thread depth of 0.4-1.5 mm.

5. The oil-free piston air compressor piston according to claim 2, characterized in that: The end face of one end of the metal body is provided with several vent holes (115), the vent holes are connected to the piston rod slot, the piston body also includes a metal valve plate (5), the metal valve plate is installed on one end face of the metal body, the metal valve plate covers the opening of one end of the vent hole, and the metal valve plate can seal the opening of one end of the vent hole under the action of the air pressure in the cylinder of the air compressor.

6. The oil-free piston air compressor piston according to claim 5, characterized in that: The metal body has a threaded hole (116) at the center of one end face, and also has a screw (6) and a set of anti-loosening washers (7). The metal valve plate has a connecting through hole (51) at the center. The screw passes through the loosening washer set and the connecting through hole of the metal valve plate and is screwed and fixed to the threaded hole at one end of the metal body. The metal valve plate can be deformed by the air pressure on both sides of the axis and repeatedly hit the end face of one end of the metal body.

7. The oil-free piston air compressor piston according to claim 6, characterized in that: At least one annular noise reduction groove (117) is provided on the end face of one end of the metal body, and the metal valve plate covers the opening surface of the annular noise reduction groove.

8. A method for manufacturing the piston of an oil-free piston air compressor as described in claims 1-7, characterized in that: Includes the following steps: Step 1: Fabricate a metal body with piston rod slots and piston ring slots, and then machine an external thread structure on the outer circumference of the metal body; Step 2: Use wear-resistant and self-lubricating materials to make wear-resistant and self-lubricating sleeves, and machine internal thread structure on the inner side of the wear-resistant and self-lubricating sleeves; Step 3: Preheat and expand the wear-resistant self-lubricating sleeve; Step 4: Install the preheated and expanded wear-resistant self-lubricating sleeve onto the outside of the metal piston body through thread engagement; Step 5: Cool the wear-resistant self-lubricating sleeve assembled on the outside of the metal piston body, so that the wear-resistant self-lubricating sleeve is fixedly attached to the outer circumferential surface of the metal piston body. Step 6: Machining radial perforations to form the first piston pin hole and the second piston pin hole on the wear-resistant self-lubricating sleeve and metal piston body assembly; Step 7: Assemble the piston rings into the piston ring slots on the outer side of one end of the metal piston body; Step 8: Insert one end of the piston rod into the piston rod slot at the other end of the metal piston body, and then insert the piston pin into the first piston pin hole, the second piston pin hole, and the third piston pin hole to assemble and position the piston rod with the piston body.

9. The method for manufacturing the piston of an oil-free reciprocating air compressor according to claim 8, characterized in that: In the third step, the temperature for preheating the wear-resistant self-lubricating sleeve is 100-300℃.

10. The method for manufacturing the piston of an oil-free reciprocating air compressor according to claim 8, characterized in that: In the second step of processing the wear-resistant self-lubricating sleeve, injection-molded tubing or extruded profile tubing without weld lines is used for circumferential outer surface finishing and internal hole tapping. The interference fit between the internal thread structure and the external thread structure on the metal piston body is 0 to 0.4 mm.

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