Surface treatment process of crankshaft, crankshaft and compressor

Abstract

The invention discloses a surface treatment process of a crankshaft, the crankshaft and a compressor, and relates to the technical field of compressors, the surface treatment process of the crankshaft comprises the steps that the crankshaft made of carbon steel is subjected to manganese phosphate coating treatment, then the crankshaft subjected to coating treatment is coated with a solid lubricating coating, and finally the coated crankshaft is cured. The steel crankshaft subjected to the surface treatment process can form a surface structure layer with wear resistance on the surface, so that the wear resistance of the crankshaft is improved, and the reliability and the performance of the compressor are further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of compressors, and in particular to a surface treatment process of a crankshaft, a crankshaft and a compressor. Background Art

[0002] In the field of compressor manufacturing, the traditional processing method for crankshafts is to use die casting or pouring to form crankshaft castings. Die casting or pouring is generally only suitable for materials such as cast iron. However, due to the higher elastic modulus of steel, under the condition of achieving the same rigidity, the shaft diameter of steel crankshafts can be smaller than that of cast iron materials, thus improving the reliability of the compressor, improving performance, and reducing noise. Since the carbon content of steel crankshafts is lower than that of ductile iron, crankshafts are prone to wear and tear, and it is urgent to optimize the anti-wear performance of the crankshaft. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a surface treatment process for a crankshaft, which can improve the wear resistance of a steel crankshaft and improve product reliability.

[0004] The invention also provides a crankshaft and a compressor.

[0005] The surface treatment process of a crankshaft according to the first embodiment of the present invention comprises: performing a manganese phosphate coating treatment on a crankshaft made of carbon steel; coating the crankshaft after coating treatment with a solid lubricating coating; and curing the coated crankshaft.

[0006] The surface treatment process of the crankshaft according to the embodiment of the present invention has at least the following beneficial effects: By subjecting a crankshaft made of carbon steel to a manganese phosphate coating, then coating the crankshaft with a solid lubricating coating, and finally curing the crankshaft, the steel crankshaft after the above surface treatment process can form a surface structure layer with anti-wear, friction-reducing, and self-lubricating properties on the surface, thereby improving the anti-wear performance of the crankshaft, and further improving the reliability and performance of the compressor equipped with the crankshaft of this embodiment.

[0007] According to some embodiments of the present invention, the solid lubricating coating comprises PAI resin and metal sulfide, and the content of the PAI resin is greater than 70%.

[0008] According to some embodiments of the present invention, the S content of the solid lubricating coating is greater than 10% by weight.

[0009] According to some embodiments of the present invention, the solid lubricating coating further comprises epoxy resin, and the content of the epoxy resin is 1% to 3%.

[0010] According to some embodiments of the present invention, the solid lubricating coating has a thickness of 6 μm to 12 μm.

[0011] According to some embodiments of the present invention, before the step of applying a solid lubricating coating to the crankshaft after film treatment, the step includes: raising the temperature of the crankshaft to above 60°C.

[0012] According to some embodiments of the present invention, coating the crankshaft after film treatment with a solid lubricating coating comprises: installing the crankshaft on a tooling capable of achieving self-rotation; wherein the rotation speed is 1300 rpm to 1500 rpm; spraying the solid lubricating coating on the crankshaft; wherein the spraying air pressure is 0.2 MPa to 0.3 MPa, and the spraying distance is 100 mm to 150 mm.

[0013] According to some embodiments of the present invention, the manganese phosphate coating treatment of the crankshaft made of carbon steel includes: performing an immersion phosphating process on the crankshaft made of carbon steel; wherein the temperature of the immersion phosphating process is in the range of 80°C to 96°C.

[0014] According to some embodiments of the present invention, the thickness of the manganese phosphate film of the crankshaft is 2 μm to 4 μm.

[0015] According to some embodiments of the present invention, more than 95% of the phosphated crystals of the manganese phosphate film have a size ranging from 4 μm to 15 μm.

[0016] According to some embodiments of the present invention, the Mn content of the manganese phosphate film is greater than 20% by weight.

[0017] According to some embodiments of the present invention, the surface roughness of the crankshaft after film treatment is in the range of 2.0Rz to 4.0Rz.

[0018] According to some embodiments of the present invention, after the step of curing the coated crankshaft, the method further includes: polishing the cured crankshaft.

[0019] According to some embodiments of the present invention, the polishing step uses a horsehair brush and the polishing time is 2s to 4s.

[0020] According to some embodiments of the present invention, the curing time of the crankshaft is 60 min to 70 min, and the curing temperature is 180° C. to 190° C.

[0021] A crankshaft according to an embodiment of the second aspect of the present invention comprises a substrate and a manganese phosphate film covering the surface of the substrate, wherein the surface of the manganese phosphate film is coated with a solid lubricating coating.

[0022] The crankshaft according to the embodiment of the present invention has at least the following beneficial effects: By setting a manganese phosphate coating on the base surface of the crankshaft and applying a solid lubricating coating, a surface structure layer with anti-wear, friction-reducing and self-lubricating properties is formed on the crankshaft surface, thereby improving the anti-wear performance of the crankshaft and further improving the reliability and performance of the compressor equipped with the crankshaft of this embodiment.

[0023] According to some embodiments of the present invention, the solid lubricating coating comprises PAI resin and metal sulfide, and the content of the PAI resin is greater than 70%.

[0024] According to some embodiments of the present invention, the solid lubricating coating further comprises epoxy resin, and the content of the epoxy resin is 1% to 3%.

[0025] According to some embodiments of the present invention, the thickness of the manganese phosphate film of the crankshaft is 2 μm to 4 μm; the thickness of the solid lubricating coating is 6 μm to 12 μm.

[0026] According to some embodiments of the present invention, more than 95% of the phosphated crystals of the manganese phosphate film have a size ranging from 4 μm to 15 μm.

[0027] A compressor according to an embodiment of the third aspect of the present invention comprises the crankshaft described in the above embodiment.

[0028] The compressor according to the embodiment of the present invention has at least the following beneficial effects: The crankshaft of the second aspect embodiment is used, and a surface structure layer with anti-wear, friction-reducing and self-lubricating properties is formed on the surface of the crankshaft, thereby improving the anti-wear performance of the crankshaft and further improving the reliability and performance of the compressor.

[0029] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 A flow chart of a surface treatment process for a crankshaft according to an embodiment of the present invention; Figure 2 A flow chart of a surface treatment process for a crankshaft according to another embodiment of the present invention; Figure 3 This is an electron microscope SE inspection image of the crystal size of the manganese phosphate film of a crankshaft according to an embodiment of the present invention; Figure 4 A flow chart of a surface treatment process for a crankshaft according to another embodiment of the present invention; Figure 5A flow chart of a surface treatment process for a crankshaft according to another embodiment of the present invention; Figure 6 The present invention is a flow chart of a surface treatment process for a crankshaft according to another embodiment of the present invention. DETAILED DESCRIPTION

[0031] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0032] In the description of the present invention, it should be understood that descriptions involving orientation, such as orientation or positional relationship indicated as up, down, etc., are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0033] In the description of the present invention, "a plurality" means more than two. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0034] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0035] Refrigeration systems are installed in refrigeration equipment such as air conditioners and refrigerators to control the ambient temperature or the temperature inside the equipment. The refrigeration system includes components such as compressors, evaporators, condensers, and throttling devices. The compressor is the core component of the refrigeration system and is used to compress the refrigerant.

[0036] For a rotary compressor, it generally includes a compressor body and a liquid reservoir. The compressor body includes a compressor housing, a pump assembly, a motor assembly and other structures. The pump assembly and the motor assembly are installed in the compressor housing. The pump assembly includes a cylinder, a crankshaft and a roller. The motor assembly drives the crankshaft to rotate. The eccentric part of the crankshaft is sleeved with a roller, and it moves eccentrically in the inner cavity of the cylinder. Therefore, the crankshaft compresses and discharges the refrigerant entering the pump assembly during the rotation process.

[0037] The crankshaft is an important component of the compressor to achieve refrigerant compression. The service life of the crankshaft directly affects the reliability of the compressor. Due to the eccentric movement of the crankshaft during operation, the crankshaft rubs against the bearings and cylinders of the pump assembly for a long time, so the anti-wear performance of the crankshaft directly determines the service life of the crankshaft.

[0038] Reference Figure 1 As shown, a surface treatment process of a crankshaft according to an embodiment of the present invention comprises the following steps: S101: The crankshaft made of carbon steel is treated with a manganese phosphate coating. It is understandable that carbon steel is an iron-carbon alloy with a carbon content of 0.0218% to 2.11%. Carbon steel generally also contains small amounts of silicon, manganese, sulfur, and phosphorus. The higher the carbon content in carbon steel, the greater the hardness and the higher the strength, but the lower the plasticity. In an embodiment of the present invention, the material of the crankshaft is a carbon steel with a carbon content of 0.42% to 0.50%. For example, the carbon content of the crankshaft can be 0.42%, 0.45%, 0.48%, 0.50%, etc.; this embodiment uses No. 45 carbon steel as the base of the crankshaft. After the steel crankshaft is treated with a manganese phosphate coating, a manganese phosphate coating will be generated on the surface.

[0039] S102: Applying a solid lubricating coating to the crankshaft after coating treatment. By further applying a solid lubricating coating to the crankshaft covered with the manganese phosphate coating, a two-layer structure of the manganese phosphate coating and the solid lubricating coating is formed on the surface of the crankshaft. The solid lubricating coating is used on the outermost surface of the crankshaft to reduce the friction loss between the crankshaft and the bearing. Once the solid lubricating coating is worn, the manganese phosphate coating with a higher hardness on the inner side ensures that the base of the crankshaft is not worn.

[0040] S103: Curing the coated crankshaft. After curing the crankshaft, the manganese phosphate film, the solid lubricating coating and the crankshaft can be stably connected and are not easily peeled off, thereby forming a surface structure layer with anti-wear, anti-friction and self-lubricating properties on the crankshaft surface, improving the anti-wear performance and reliability of the crankshaft, reducing the wear problem of the crankshaft, improving product reliability, and thus improving the reliability and performance of the compressor.

[0041] Reference Figure 2 As shown, in a surface treatment process of a crankshaft according to an embodiment of the present invention, step S101 of performing manganese phosphate coating treatment on the crankshaft specifically includes: S201: Perform phosphating treatment on the crankshaft by immersion. It is understandable that the phosphating treatment by immersion can improve the uniformity of the manganese phosphide film formed on the crankshaft surface, thereby ensuring that the thickness and roughness of the manganese phosphide film are within the control range, which is beneficial to improving the adhesion effect of the fixed lubricating coating in the subsequent steps.

[0042] In one embodiment of the present invention, the temperature of the immersion phosphating process is in the range of 80°C to 96°C, for example, the temperature of the immersion phosphating process can be 80°C, 85°C, 90°C, 95°C, 96°C, etc. According to experimental analysis, the temperature of the process in the range of 80°C to 96°C can make the morphology of the phosphating crystals more uniform, which is beneficial to improving the quality of the manganese phosphide film, and further improving the wear resistance of the crankshaft.

[0043] It is understood that the thickness of the manganese phosphate coating of the crankshaft is 2 μm to 4 μm, for example, the thickness of the manganese phosphate coating can be 2 μm, 3 μm, 3.5 μm, 4 μm, etc. When the thickness of the manganese phosphate coating meets the above range, it can ensure that the manganese phosphate coating is bonded and does not fall off to achieve better wear resistance; if the thickness of the manganese phosphate coating is less than 2 μm, the wear resistance cannot meet the requirements, and once the outermost solid coating of the crankshaft is worn off, it is easy to wear the base of the crankshaft.

[0044] Reference Figure 3 As shown, Figure 3 This is the electron microscope SE inspection picture of the crystal size of manganese phosphate film. Figure 3 It can be seen that more than 95% of the phosphate crystals of the manganese phosphate film are in the range of 4μm to 15μm. It should be noted that the phosphate crystals are flat, and as shown in the figure, most of the phosphate crystals are in the above range. It can be understood that the experiment shows that when the phosphate crystal size is in the range of 4μm to 15μm, the manganese phosphate film can best combine with the crankshaft matrix and solid lubricant coating.

[0045] It is understood that the Mn content of the manganese phosphate film is greater than 20% by weight, for example, the Mn content can be 21%, 25%, 30%, 50%, etc. By controlling the Mn content, the wear resistance of the manganese phosphate film can be controlled to meet the requirements.

[0046] It is understandable that the surface roughness of the crankshaft after coating treatment is within the range of 2.0Rz to 4.0Rz, for example, the surface roughness may be 2.0Rz, 2.5Rz, 3.0Rz, 4.0Rz, etc. By designing the process parameters of the manganese phosphate coating treatment, such as controlling the concentration of the surface conditioning agent, so that the surface roughness of the treated crankshaft reaches the above parameter range, there is no need to perform a polishing step, which reduces the steps of the surface treatment process, optimizes the process flow, and improves the surface treatment efficiency.

[0047] In one embodiment of the present invention, the solid lubricating coating includes PAI resin and metal sulfide, and the PAI resin is polyamide-imide, and its physicochemical property is a type of polymer in which imide rings and amide bonds are regularly alternately arranged. In the composition of the solid lubricating coating of the embodiment of the present invention, the content of PAI resin is greater than 70%, for example, the content of PAI resin can be 71%, 75%, 80%, 90%, etc. The metal sulfide in the solid lubricating coating is used to provide lubricity to the coating, and the PAI resin is used to provide lubricity and wear resistance to the coating, and the PAI resin is also used to act as a binder between metal sulfides, so that the solid lubricant has better anti-friction and self-lubricating properties, thereby reducing the wear problem of the crankshaft and improving product reliability.

[0048] In another embodiment of the present invention, the solid lubricating coating further comprises epoxy resin, and the content of the epoxy resin is 1% to 3%, for example, the content of the epoxy resin is 1%, 2%, 3%, etc. It can be understood that the addition of epoxy resin can appropriately reduce the curing temperature of the solid lubricating coating without affecting the wear resistance of the fixed lubricating coating.

[0049] It is understandable that the S content of the solid lubricating coating is greater than 10% by weight, for example, the S content is 11%, 15%, 20%, 30%, etc. This embodiment controls the lubricity and wear resistance of the solid lubricating coating by controlling the S content.

[0050] It is understandable that the thickness of the solid lubricating coating is 6μm to 12μm, for example, 6μm, 7μm, 9μm, 10μm, 12μm, and so on. When the thickness of the solid lubricating coating meets the above range, the overall lubricity and wear resistance are the highest, and the material has the highest cost performance. If the thickness of the solid lubricating coating is greater than 12μm, the solid lubricating coating is too thick, it is difficult to ensure the uniformity of spraying, and the manufacturing difficulty increases exponentially, and the yield rate decreases; and the clearance with the bearing will also decrease, which will directly wear the solid lubricating coating, so the wear resistance will drop sharply. If the thickness of the solid lubricating coating is less than 6μm, the thickness of the fixed lubricating coating is too thin, which will directly wear the manganese phosphate film, thereby increasing the risk of matrix wear of the crankshaft.

[0051] It can be understood that, in this embodiment, the curing time of the crankshaft is 60 minutes to 70 minutes, for example, 60 minutes, 65 minutes, 68 minutes, 70 minutes, etc. The curing temperature is 180°C to 190°C, for example, 180°C, 183°C, 185°C, 190°C, etc. When the curing time and temperature meet the above parameter range, the adhesion performance of the manganese phosphate film and the solid lubricating coating is better, which can improve the bonding ability of the crankshaft and the surface structure layer, thereby improving the anti-wear performance of the crankshaft, reducing the wear problem of the crankshaft, and improving product reliability.

[0052] Reference Figure 4 As shown, the surface treatment process of a crankshaft according to another embodiment of the present invention, before the step S102 of coating the crankshaft with a solid lubricating coating after the film treatment, comprises: S401: Raise the temperature of the crankshaft to above 60°C. For example, raise the temperature of the crankshaft to 61°C, 65°C, 70°C or 80°C. Raising the temperature of the crankshaft before applying the solid lubricating coating is beneficial to improving the adhesion of the solid lubricating coating, thereby improving the connection strength between the manganese phosphate film and the solid lubricating coating, and further improving the anti-wear performance and lubrication performance of the crankshaft.

[0053] Reference Figure 5 As shown, in another embodiment of the crankshaft surface treatment process of the present invention, the step S102 of coating the crankshaft after the film treatment with a solid lubricating coating specifically includes: S501: The crankshaft is mounted on a fixture capable of self-rotation. The fixture can achieve stable rotation under the drive of the motor. The rotation speed is 1300 rpm to 1500 rpm, for example, the rotation speed can be 1300 rpm, 1350 rpm, 1400 rpm, 1500 rpm, etc.

[0054] S502: Spraying a solid lubricating coating onto the crankshaft. The spraying pressure is 0.2 MPa to 0.3 MPa, such as 0.2 MPa, 0.25 MPa, 0.27 MPa, and 0.3 MPa. The spraying distance is 100 mm, 120 mm, 140 mm, and 150 mm. The embodiment of the present invention adopts the above-mentioned surface treatment process steps to make the film thickness of the solid lubricating coating more uniform.

[0055] Reference Figure 6 As shown, the surface treatment process of a crankshaft in another embodiment of the present invention further includes, after the step S103 of curing the coated crankshaft: S601: Polish the solidified crankshaft. The surface roughness of the polished crankshaft is controlled within the range of 4.0Rz to 7.0Rz, which can meet the working condition requirements of the crankshaft, reduce the wear problem of the crankshaft, and improve product reliability.

[0056] In the embodiment of the present invention, the polishing step is performed using a horsehair brush, which is a brush made of processed horsehair and horse mane. Since yak hair is similar to horse hair, brushes made of yak hair are also collectively referred to as horsehair brushes. The horsehair brush is soft, antistatic, and has strong water absorption. The polishing time of this embodiment is 2s to 4s, for example, the polishing time can be 2s, 3s, 4s, etc.

[0057] In order to meet the operating requirements of the crankshaft, after polishing, the surface roughness of the crankshaft in the embodiment of the present invention is controlled within the range of 4.0Rz to 7.0Rz, the hardness is controlled to 4H, the roundness is less than or equal to 8μm, and the primary and secondary shaft runout is less than or equal to 4μm.

[0058] A crankshaft according to an embodiment of the present invention is manufactured according to the surface treatment process of the crankshaft in the above embodiment. The crankshaft in the embodiment of the present invention is manufactured using the surface treatment process of the crankshaft in the embodiment of the first aspect, and a surface structure layer with anti-wear, friction-reducing and self-lubricating properties is formed on the surface of the crankshaft, thereby improving the anti-wear performance of the crankshaft, and further improving the reliability and performance of the compressor equipped with the crankshaft of this embodiment.

[0059] Since the crankshaft of the embodiment of the present invention adopts all the technical solutions of the surface treatment process of the crankshaft in the above embodiment, it has at least all the beneficial effects brought by the technical solutions of the above embodiment, which will not be repeated here.

[0060] A crankshaft according to another embodiment of the present invention comprises a substrate and a manganese phosphate film covering the surface of the substrate, wherein the surface of the manganese phosphate film is coated with a solid lubricating coating. The manganese phosphate film, the solid lubricating coating and the substrate can be stably connected and are not easily peeled off, thereby forming a surface structure layer with anti-wear, friction-reducing and self-lubricating properties on the surface of the crankshaft, improving the anti-wear performance and reliability of the crankshaft, reducing the wear problem of the crankshaft, improving product reliability, and thereby improving the reliability and performance of the compressor.

[0061] It is understood that the solid lubricating coating includes PAI resin and metal sulfide, and the content of the PAI resin is greater than 70%. When the content of the PAI resin is set in the above range, it can provide lubricity and wear resistance for the solid lubricating coating, and can also act as a binder between metal sulfides, so that the solid lubricant has better wear reduction and self-lubricating properties.

[0062] It is understandable that the solid lubricating coating further includes epoxy resin, and the content of the epoxy resin is 1% to 3%. The addition of epoxy resin can appropriately reduce the curing temperature of the solid lubricating coating and improve the manufacturability of the solid lubricating coating without affecting the wear resistance of the fixed lubricating coating.

[0063] It is understandable that the thickness of the manganese phosphate film of the crankshaft is 2μm to 4μm. When the thickness of the manganese phosphate film meets the above range, it can ensure that the manganese phosphate film is bonded and does not fall off to achieve better wear resistance. The thickness of the solid lubricating coating is 6μm to 12μm. When the thickness of the solid lubricating coating meets the above range, the overall lubricity and wear resistance are the highest, and the material has the highest cost performance. If the thickness of the solid lubricating coating is greater than 12μm, the solid lubricating coating is too thick, it is difficult to ensure the uniformity of spraying, and the manufacturing difficulty increases exponentially and the yield rate decreases; and the gap with the bearing will also decrease, which will directly wear the solid lubricating coating, so the wear resistance will drop sharply. If the thickness of the solid lubricating coating is less than 6μm, the thickness of the fixed lubricating coating is too thin, which will directly wear the manganese phosphate film, thereby increasing the risk of matrix wear of the crankshaft.

[0064] A compressor according to an embodiment of the present invention includes the crankshaft according to the above embodiment, and the compressor may be a rotary compressor, a scroll compressor, etc., which is not specifically limited here. The compressor according to the embodiment of the present invention adopts the crankshaft according to the embodiment of the second aspect, and the surface of the crankshaft forms a surface structure layer with anti-wear, friction-reducing and self-lubricating properties, thereby improving the anti-wear performance of the crankshaft, thereby improving the reliability and performance of the compressor.

[0065] Since the compressor of the embodiment of the present invention adopts all the technical solutions of the crankshaft of the above embodiment, it has at least all the beneficial effects brought by the technical solutions of the above embodiment, which will not be repeated here.

[0066] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. The surface treatment process of the crankshaft is characterized by: The following steps are involved: Crankshafts made of carbon steel are treated with manganese phosphate coating; Applying a solid lubricating coating to the crankshaft after the coating treatment; The coated crankshaft is cured.

2. The surface treatment process of the crankshaft according to claim 1, characterized in that: The solid lubricating coating comprises PAI resin and metal sulfide, and the content of the PAI resin is greater than 70%.

3. The surface treatment process of the crankshaft according to claim 2, characterized in that: The S content of the solid lubricating coating is greater than 10% by weight.

4. The surface treatment process of the crankshaft according to claim 2 or 3, characterized in that: The solid lubricating coating further comprises epoxy resin, and the content of the epoxy resin is 1% to 3%.

5. The surface treatment process of the crankshaft according to claim 1, characterized in that: The solid lubricating coating has a thickness of 6 μm to 12 μm.

6. The surface treatment process of the crankshaft according to claim 1, characterized in that: Before the step of applying a solid lubricating coating to the crankshaft after the film treatment, the method comprises: The temperature of the crankshaft was raised to above 60°C.

7. The surface treatment process of the crankshaft according to claim 1 or 6, characterized in that: The method of coating the crankshaft after the film treatment with a solid lubricating coating comprises: The crankshaft is mounted on a tooling capable of realizing self-rotation; wherein the rotation speed is 1300 rpm to 1500 rpm; A solid lubricating coating is sprayed onto the crankshaft; wherein the spraying pressure is 0.2 MPa to 0.3 MPa, and the spraying distance is 100 mm to 150 mm.

8. The surface treatment process of the crankshaft according to claim 1, characterized in that: The method of subjecting the crankshaft made of carbon steel to manganese phosphate coating treatment comprises: The crankshaft made of carbon steel is subjected to an immersion phosphating process, wherein the temperature of the immersion phosphating process is in the range of 80°C to 96°C.

9. The surface treatment process of a crankshaft according to claim 1 or 8, characterized in that: The manganese phosphate film of the crankshaft has a thickness of 2 μm to 4 μm.

10. The surface treatment process of the crankshaft according to claim 1 or 8, characterized in that: More than 95% of the phosphated crystals of the manganese phosphate film have a size ranging from 4 μm to 15 μm.

11. The surface treatment process of a crankshaft according to claim 1 or 8, characterized in that: The Mn content of the manganese phosphate film is greater than 20% by weight.

12. The surface treatment process of the crankshaft according to claim 1, characterized in that: The surface roughness of the crankshaft after film treatment is in the range of 2.0Rz to 4.0Rz.

13. The surface treatment process of a crankshaft according to claim 1 or 8, characterized in that: After the step of curing the coated crankshaft, the method further comprises: The cured crankshaft is polished.

14. The surface treatment process of the crankshaft according to claim 13, characterized in that: The polishing step uses a horsehair brush and the polishing time is 2s to 4s.

15. The surface treatment process of the crankshaft according to claim 1, characterized in that: The curing time of the crankshaft is 60 minutes to 70 minutes, and the curing temperature is 180° C. to 190° C.

16. Crankshaft, characterized in that: The invention comprises a substrate and a manganese phosphate film covering the surface of the substrate, wherein the surface of the manganese phosphate film is coated with a solid lubricating coating.

17. The crankshaft according to claim 16, characterized in that: The solid lubricating coating comprises PAI resin and metal sulfide, and the content of the PAI resin is greater than 70%.

18. The crankshaft according to claim 17, characterized in that: The solid lubricating coating further comprises epoxy resin, and the content of the epoxy resin is 1% to 3%.

19. The crankshaft according to any one of claims 16 to 18, characterized in that: The thickness of the manganese phosphate film of the crankshaft is 2 μm to 4 μm; the thickness of the solid lubricating coating is 6 μm to 12 μm.

20. The crankshaft according to claim 16, characterized in that: More than 95% of the phosphated crystals of the manganese phosphate film have a size ranging from 4 μm to 15 μm.

21. A compressor, characterized in that: A crankshaft comprising any one of claims 16 to 20.

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