Camshaft with optimized quench layer shape

Abstract

This invention relates to a camshaft with an optimized hardened layer shape, comprising an integral hollow shaft body, an end-positioning shaft head section, multiple sets of support journal sections, multiple sets of cam assembly sections, a rear-end sealing shaft head section, and an auxiliary support section. The support journal sections have circumferential cooling oil channels arranged in a closed loop around the shaft body, which are connected to a central main oil channel. The outer surface of the support journal sections has multiple radial oil injection holes connected to the circumferential cooling oil channels. The cam assembly sections include at least two peach-shaped cams, each with a contoured closed-loop oil channel that conforms to the cam profile. These contoured closed-loop oil channels are arranged circumferentially around the cam profile and are connected to the central main oil channel through radial connecting holes. This invention achieves complete matching between the hardened layer and the working stress, solving the problems of mutual inductance interference and uneven layer depth in traditional quenching processes, thereby improving the wear resistance and fatigue resistance of the camshaft.

Description

Technical Field

[0001] This invention relates to the field of internal combustion engine camshaft manufacturing technology, specifically a camshaft with an optimized hardened layer shape. Background Technology

[0002] The camshaft is the core driving component of the valve train in an internal combustion engine, widely used in reciprocating piston internal combustion engines in passenger cars, commercial vehicles, construction machinery, and marine power systems. It drives the valves to open and close in a preset sequence through the rotational motion of the cam profile, directly determining the engine's valve timing accuracy, power output characteristics, fuel economy, and operational reliability. With the rapid development of high-power-density internal combustion engine technology, engine burst pressure and speed continue to increase. The camshaft's cam working surface and support journals must withstand higher contact stresses and alternating loads, placing more stringent requirements on the camshaft's surface wear resistance and fatigue resistance. Induction hardening, as the core process for camshaft surface strengthening, directly determines the camshaft's service life and the overall engine's operational stability through the distribution accuracy and forming quality of its hardened layer.

[0003] The existing induction hardening treatment of internal combustion engine camshafts typically uses a contour induction coil to simultaneously or segmentally induction heat the camshaft support journal and cam working surface, raising the surface temperature of the target area to the austenitizing temperature. Then, a quenching medium is sprayed onto the heated area through an external spraying device to achieve rapid cooling, thereby forming a martensitic hardened layer on the camshaft surface and improving surface hardness and wear resistance.

[0004] However, existing technical solutions cannot solve the problem of axial current leakage between adjacent journals and cam structure during induction hardening. This makes it difficult to independently heat and precisely control the temperature of each hardening area, making it difficult to achieve differentiated and precise control of the hardened layer depth based on the contact stress distribution during camshaft operation. Ultimately, this leads to a serious mismatch between the hardened layer distribution and the working stress distribution of the camshaft, resulting in the core problems of mutual inductance interference between adjacent areas and uneven hardened layer depth. This significantly reduces the wear resistance and fatigue resistance of the camshaft, making it unable to meet the long-term reliable operation requirements of high power density internal combustion engines. Summary of the Invention

[0005] The purpose of this invention is to provide a camshaft with an optimized hardened layer shape, which aims to improve the problem that existing technologies are unable to achieve differentiated and precise control of the hardened layer depth based on the contact stress distribution during the camshaft's operation.

[0006] The objective of this invention is achieved through the following technical solution: a camshaft with an optimized quenching layer shape, comprising an integral hollow shaft body, an end positioning shaft head section, multiple sets of support journal sections, multiple sets of cam sections, a rear sealing shaft head section, and an auxiliary support section;

[0007] The support journal section is provided with a circumferential cooling oil passage arranged in a closed loop along the circumference of the shaft body. The circumferential cooling oil passage is connected to the central main oil passage. The outer circular surface of the support journal section is provided with multiple radial oil injection holes that are connected to the circumferential cooling oil passage.

[0008] The cam assembly includes at least two peach-shaped cams. The interior of each peach-shaped cam is provided with a contoured closed-loop oil passage that matches the contour of the peach-shaped cam. The contoured closed-loop oil passage is arranged in a closed loop around the contour of the peach-shaped cam. The contoured closed-loop oil passage is connected to the central main oil passage through a radial connecting hole. The working surface of the peach-shaped cam is provided with multiple oil injection micro-holes that are connected to the contoured closed-loop oil passage.

[0009] As a further description of the above technical solution:

[0010] An axially connected oil passage is provided inside the transition section between adjacent peach-shaped cams in the cam group section. The axially connected oil passage connects the contour-following closed-loop oil passages of two peach-shaped cams in the same group to each other.

[0011] As a further description of the above technical solution:

[0012] The radial oil injection holes of the support journal section are evenly distributed along the circumference of the shaft body, and the oil injection micro-holes of the peach-shaped cam are only set on the lift and return working surfaces of the peach-shaped cam and are evenly distributed along the profile.

[0013] As a further description of the above technical solution:

[0014] The cross-section of the contour-following closed-loop oil channel is elliptical. The distance between it and the peach-shaped cam surface is largest at the tip of the peach-shaped cam, followed by the lift and return working surfaces of the peach-shaped cam, and smallest at the base circle of the peach-shaped cam, forming a gradient spacing structure that perfectly matches the contact stress distribution of the peach-shaped cam. The cross-section of the circumferential cooling oil channel is circular and is centrally arranged along the axial direction of the support journal section, maintaining a uniform radial distance from the outer circle surface of the support journal section, and forming a closed loop around the circumference of the shaft. The circumferential cooling oil channel and the contour-following closed-loop oil channel are used to introduce cooling medium in the quenching process to accurately control the hardened layer boundary and depth of the corresponding area of ​​the shaft. In the working state, they are used to introduce lubricating oil to achieve forced lubrication and cooling of the corresponding friction surfaces.

[0015] As a further description of the above technical solution:

[0016] The axial end faces of the support journal section and the end faces of the transition section between adjacent peach-shaped cams in the cam group section are all provided with dovetail-shaped mutual inductance isolation grooves arranged in a closed loop along the circumference of the shaft. The cross-section of the dovetail-shaped mutual inductance isolation groove is a dovetail-shaped structure with a narrow opening and a wide bottom. The groove is recessed inward along the axial direction of the shaft and is a closed loop around the circumference of the shaft without any breaks. It is used to block the axial current flow during the induction hardening process.

[0017] As a further description of the above technical solution:

[0018] The front positioning shaft head section is a coaxial stepped shaft structure. The front positioning shaft head section has an internal hexagonal forming hole inside. The bottom of the internal hexagonal forming hole has an oil inlet that communicates with the central main oil passage. The oil inlet of the internal hexagonal forming hole is surrounded by an annular hardened layer limiting groove. The outer circular surface of the mating section of the front positioning shaft head section is provided with a non-hardened protective ring.

[0019] As a further description of the above technical solution:

[0020] The rear sealing shaft head section is a coaxial stepped shaft structure. The interior of the rear sealing shaft head section is provided with a three-section riveted plug mounting hole that communicates with the central main oil passage. An oil passage pressure buffer chamber is provided between the three-section riveted plug mounting hole and the central main oil passage. The outer circular surface of the plug mounting area of ​​the rear sealing shaft head section is provided with a non-hardened protective ring band.

[0021] As a further description of the above technical solution:

[0022] The auxiliary support section includes a margin optical axis section. A bearing bushing is located on the outer side of the margin optical axis section. A locking washer is provided on the inner side of the bearing bushing. A locking nut is fixedly connected to the other end of the bearing bushing. The locking nut is threaded onto the fine-tooth external thread on the outer side of the margin optical axis section.

[0023] Compared with the prior art, the advantages of the present invention are as follows:

[0024] 1. Through the synergistic structure of dovetail-shaped mutual inductance isolation groove, gradient-spacing contoured closed-loop oil channel and circumferential cooling oil channel, the quenching process is driven to achieve precise temperature control in different zones. First, the dovetail groove blocks the axial flow of induced current to achieve independent heating of the target area. Then, the cooling medium is pumped into the two types of closed-loop oil channels through the central main oil channel. Differentiated inner wall cooling precisely controls the boundary and depth of the hardened layer, achieving a complete match between the hardened layer and the working stress. This solves the pain points of mutual inductance interference and uneven layer depth in traditional quenching, thereby improving the wear resistance and fatigue resistance of the camshaft.

[0025] 2. The integrated oil circuit structure, which connects the central main oil passage with the circumferential cooling oil passage and the contoured closed-loop oil passage, drives the precise oil supply of the entire shaft lubrication system. The central main oil passage delivers engine pressure lubricating oil, which is then evenly distributed throughout the shaft through the radial connecting holes and axial connecting oil passages. Finally, the lubricating oil is precisely sprayed to the corresponding friction pairs through the radial oil injection holes and oil injection micro-holes, achieving forced lubrication and cooling in high-stress areas. This effectively reduces the coefficient of friction and operating temperature rise, and improves the operating stability of the camshaft and the service life of the entire machine. Attached Figure Description

[0026] Figure 1This is a schematic diagram of the main body of an embodiment of a camshaft with an optimized quenching layer shape proposed in this invention;

[0027] Figure 2 This is a schematic diagram of the structure of an integral hollow shaft body with an optimized quenching layer shape for a camshaft proposed in this invention.

[0028] Figure 3 This is a schematic diagram of the front-end positioning shaft head section of a camshaft with an optimized quenching layer shape, as proposed in this invention.

[0029] Figure 4 This is a schematic diagram of the support journal section of a camshaft with an optimized quenching layer shape, as proposed in this invention.

[0030] Figure 5 This invention provides a schematic diagram of the structure of a cam segment of a camshaft with an optimized hardened layer shape. Figure 1 ;

[0031] Figure 6 This invention provides a schematic diagram of the structure of a cam segment of a camshaft with an optimized hardened layer shape. Figure 2 ;

[0032] Figure 7 This is a schematic diagram of the structure of the rear sealing shaft head section of a camshaft with an optimized quenching layer shape proposed in this invention.

[0033] Figure 8 This is a schematic diagram of the auxiliary support section of a camshaft with an optimized quenching layer shape, as proposed in this invention.

[0034] Labeling Explanation: 1. Integral Hollow Shaft; 2. Central Main Oil Passage; 3. Front Positioning Shaft Head Section; 301. Internal Hexagonal Formed Hole; 302. Oil Inlet; 303. Annular Hardened Layer Limiting Groove; 304. Non-Hardened Protective Ring Band One; 4. Supporting Journal Section; 401. Circumferential Cooling Oil Passage; 402. Radial Oil Injection Hole; 5. Cam Assembly Section; 501. Peach-Shaped Cam; 502. Contour Closed-Loop Oil Passage; 503. Radial Connecting Hole; 504. Oil Injection Micro-Orifice; 505. Axial Connecting Oil Passage; 6. Rear Sealed Shaft Head Section; 601. Three-Section Riveted Plug Mounting Hole; 602. Oil Passage Pressure Buffer Chamber; 603. Non-Hardened Protective Ring Band Two; 7. Auxiliary Support Section; 701. Excess Shaft Section; 702. Bearing Bushing; 703. Locking Washer; 704. Lock Nut; 8. Dovetail Type Mutual Inductance Isolation Groove. Detailed Implementation

[0035] The present invention will now be described in detail with reference to the accompanying drawings and embodiments:

[0036] like Figures 1 to 8The diagram shows an embodiment of a camshaft with an optimized hardened layer shape provided by the present invention. This embodiment provides a camshaft with an optimized hardened layer shape, including an integral hollow shaft body 1, which serves as the base bearing structure of the camshaft, providing an installation reference for all functional structures and ensuring the overall structural rigidity and rotational coaxiality of the shaft body. It also includes a front-end positioning shaft head section 3, which provides a precise installation positioning reference and mating interface for the timing transmission components, ensuring the assembly accuracy and transmission stability of the timing transmission. Multiple sets of support journal sections 4 provide rotational support references for the camshaft, bear the radial load during operation, and ensure the coaxiality and stability of the camshaft rotation. Multiple sets of cam groups 5 provide a drive reference for the engine valve train mechanism, precisely controlling the engine's valve timing phase. A rear-end sealed shaft head section 6 provides an installation positioning reference for signal disc accessories and provides forming space for the sealing of the end of the central main oil passage 2. It also includes an auxiliary support section 7, which provides additional rotational support for the long shaft body, reducing the risk of deflection and resonance during high-speed rotation and improving the rotational rigidity and operational stability of the shaft body.

[0037] The front-end positioning shaft head section 3 is a coaxial stepped shaft structure. The front-end positioning shaft head section 3 has an internal hexagonal forming hole 301, providing a dedicated torque transmission interface for the camshaft, suitable for extrusion molding processes. It also provides forming space for the oil inlet 302. The bottom of the internal hexagonal forming hole 301 has an oil inlet 302 connected to the central main oil passage 2. The central main oil passage 2 serves as the core transport channel for the camshaft quenching cooling medium and working lubricating oil, realizing the axial transport and distribution of the medium throughout the entire shaft range, providing a stable medium supply to each branch oil passage. The oil inlet 302 facilitates the transport of the quenching cooling medium. The connection between the engine lubricating oil and the central main oil passage 2 provides an input channel for the medium to enter the internal oil passage system. An annular hardened layer limiting groove 303 is provided around the oil inlet 302 of the internal hexagonal forming hole 301 to block the extension of the hardened layer to the oil inlet 302 area during the quenching process, avoiding the risk of stress concentration and cracking of the oil inlet 302 due to quenching. The outer circular surface of the mating section of the front positioning shaft head section 3 is provided with a non-hardened protective ring band 304 to reduce the heating temperature of the corresponding area during the quenching process, avoiding hardness changes and dimensional deformation of the front mating surface due to quenching, and ensuring the mating accuracy of the timing components.

[0038] The support journal section 4 is provided with a circumferential cooling oil channel 401 arranged in a closed loop along the circumference of the shaft. During the quenching process, a cooling medium is introduced to achieve constant temperature cooling of the inner wall of the support journal section 4. In the working state, it stores and distributes lubricating oil to provide a stable supply of lubricating oil to the radial oil injection holes 402. The circumferential cooling oil channel 401 is connected to the central main oil channel 2. The outer circular surface of the support journal section 4 is provided with multiple radial oil injection holes 402 that are connected to the circumferential cooling oil channel 401. In the working state, the lubricating oil is continuously sprayed onto the mating friction surface of the support journal and the bearing to form a stable lubricating oil film, thereby achieving forced lubrication and cooling of the friction pair. The radial oil injection holes 402 of the support journal section 4 are evenly distributed along the circumference of the shaft.

[0039] Cam assembly 5 includes at least two peach-shaped cams 501, serving as the core actuator for valve train operation. Through profile design, they achieve precise timing control of valve opening and closing, and bear the contact friction load with the tappets. The peach-shaped cams 501 have internal contoured closed-loop oil passages 502 that conform to their profile. During the quenching process, cooling medium is introduced to achieve differentiated constant-temperature cooling of the inner wall of the peach-shaped cams 501. In operation, they store and distribute lubricating oil, providing a stable lubricating oil supply to the oil injection micro-orifices 504. The contoured closed-loop oil passages 502 are arranged circumferentially along the profile of the peach-shaped cams 501. The contoured closed-loop oil passages 502 are connected to the central main oil passage 2 through radial connecting holes 503, enabling bidirectional flow of cooling medium and lubricating oil between the central main oil passage 2 and the contoured closed-loop oil passages 502, ensuring the smooth flow of the medium. To ensure uniformity and stability of the supply, the working surface of the peach-shaped cam 501 is equipped with multiple oil spray micro-holes 504 that are connected to the contoured closed-loop oil passages 502. During operation, the lubricating oil is precisely sprayed onto the mating friction surfaces of the cam and the tappet, forming a stable lubricating oil film. This achieves forced lubrication and cooling of the high-stress friction pair. The oil spray micro-holes 504 of the peach-shaped cam 501 are only set on the lift and return working surfaces of the peach-shaped cam 501 and are evenly distributed along the profile. The transition section between adjacent peach-shaped cams 501 in the cam group 5 is equipped with an axially connected oil passage 505 to achieve uniform flow and interconnection of cooling medium and lubricating oil between cams in the same group. This ensures the consistency of the quenching cooling effect and lubrication effect of the two cams. The axially connected oil passage 505 connects the contoured closed-loop oil passages 502 of the two peach-shaped cams 501 in the same group.

[0040] The cross-section of the contour-following closed-loop oil passage 502 is elliptical. The distance between it and the surface of the peach-shaped cam 501 is largest at the tip of the peach-shaped cam 501, followed by the lift and return working surfaces of the peach-shaped cam 501, and smallest at the base circle of the peach-shaped cam 501. This forms a gradient spacing structure that perfectly matches the contact stress distribution of the peach-shaped cam 501, matching the contact stress distribution during cam operation. In the quenching process, it achieves differentiated cooling of different areas of the cam, precisely controls the hardened layer depth of the corresponding area, and achieves a perfect match between the hardened layer and the working stress. The cross-section of the circumferential cooling oil passage 401 is circular and is centrally arranged along the axial direction of the support journal section 4, maintaining a uniform radial distance from the outer circular surface of the support journal section 4. It forms a closed loop around the circumference of the shaft. The circumferential cooling oil passage 401 and the contour-following closed-loop oil passage 502 are used to introduce cooling medium in the quenching process to precisely control the hardened layer boundary and depth of the corresponding area of ​​the shaft. In the working state, they are used to introduce lubricating oil to achieve forced lubrication and cooling of the corresponding friction surfaces.

[0041] The axial end faces of the journal section 4 and the end faces of the transition section between adjacent peach-shaped cams 501 in the cam group section 5 are provided with dovetail-shaped mutual inductance isolation grooves 8 arranged in a closed loop around the shaft body. The cross-section of the dovetail-shaped mutual inductance isolation groove 8 is a dovetail-shaped structure with a narrow opening and a wide bottom. The groove body is recessed inward along the axial direction of the shaft body and forms a closed loop around the shaft body without any breaks. It is used to block the axial current flow during the induction hardening process.

[0042] The rear sealing shaft head section 6 is a coaxial stepped shaft structure. The interior of the rear sealing shaft head section 6 is provided with a three-section riveted plug mounting hole 601 that communicates with the central main oil passage 2, providing a mating interface for the plug installation and riveting. The high-pressure seal at the end of the central main oil passage 2 is achieved through the riveting process, ensuring the sealing performance of the oil passage system. An oil passage pressure buffer chamber 602 is provided between the three-section riveted plug mounting hole 601 and the central main oil passage 2. During engine operation, it absorbs pressure fluctuations in the entire oil passage, maintains the stability of lubricating oil pressure in each oil passage, and avoids poor lubrication caused by oil pressure fluctuations. The outer circular surface of the plug mounting area of ​​the rear sealing shaft head section 6 is provided with a non-hardened protective ring band 603, which reduces the heating temperature of the corresponding area during the quenching process, avoids hardness changes and dimensional deformation in the plug mounting area due to quenching, and ensures the assembly accuracy and sealing effect of the plug riveting seal.

[0043] The auxiliary support section 7 includes a spare optical shaft section 701, which provides an installation reference for the auxiliary support structure, adapts to the installation space of the engine block, is compatible with accessory installation requirements, and improves the universal compatibility of the camshaft. A bearing bushing 702 is located on the outer side of the spare optical shaft section 701, providing a wear-resistant rotational mating interface for the auxiliary support, reducing friction and wear at the auxiliary support location, and extending the service life of the support structure. A retaining washer 703 is provided on the inner side of the bearing bushing 702 to achieve circumferential stopping and axial limiting of the bearing bushing 702, preventing the bearing bushing 702 from moving. 02 During operation, rotation and movement occur. To ensure the stability of the support structure, a locking nut 704 is fixedly connected to the other end of the bearing bushing 702, which realizes the axial locking and positioning of the bearing bushing 702, prevents the bearing bushing 702 from moving axially, and ensures the assembly reliability of the auxiliary support structure. The locking nut 704 is threaded on the fine-tooth external thread on the outer side of the allowable optical shaft section 701, providing a precise thread fit interface for the locking nut 704, improving the stability of the locking force and the anti-loosening effect, and ensuring the reliability of the locking and positioning.

[0044] Working principle: After the integral hollow shaft 1 is machined and formed, the shaft is clamped into the tooling fixture of the induction hardening equipment to complete the coaxial alignment of the shaft and the induction heating coil. At the same time, the oil inlet 302 of the front positioning shaft head section 3 and the plug mounting hole of the rear sealing shaft head section 6 are respectively sealed and connected to the inlet and outlet pipelines of the quenching cooling medium circulation system to complete the preparatory work for the quenching process.

[0045] The induction hardening equipment is started, and a high-frequency induced current with set parameters is passed into the induction heating coil to synchronously induction heat the outer surfaces of the support journal section 4 and the cam assembly section 5 of the shaft. During the heating process, the dovetail-shaped mutual inductance isolation groove 8 at the transition position between the support journal section 4 and the cam assembly section 5 continuously blocks the induced current from flowing along the shaft axis, limiting the induced current to form an eddy current heating effect only in the target heating area. The non-hardened protective ring band 304 on the outer circular surface of the front positioning shaft head section 3 and the annular hardened layer limiting groove 303 around the oil inlet 302 synchronously limit the temperature change range of the corresponding area. The non-hardened protective ring band 603 on the outer circular surface of the plug installation area of ​​the rear sealing shaft head section 6 synchronously limits the temperature change range of the corresponding area.

[0046] When the surface temperature of the target heating area of ​​the shaft reaches the austenitizing critical temperature, the quenching cooling medium circulation system is started. The low-temperature cooling medium is pumped into the central main oil passage 2 in the center of the shaft through the oil inlet 302. During the axial flow of the cooling medium along the central main oil passage 2, it enters the circumferential cooling oil passage 401 inside each support journal section 4 and the contour closed-loop oil passage 502 inside each peach-shaped cam 501 through the radial connecting hole 503. At the same time, the cooling medium is evenly distributed between the two contour closed-loop oil passages 502 in the same cam group section 5 through the axial connecting oil passage 505.

[0047] During the closed-loop flow of the cooling medium along the circumferential axis of the shaft in the circumferential cooling oil passage 401, the inner wall of the support journal section 4 is continuously cooled at a constant temperature, limiting the hardened layer of the support journal section 4 to only form in the area between the circumferential cooling oil passage 401 and the outer circular surface. During the closed-loop flow of the cooling medium along the profile of the peach-shaped cam 501 in the contour closed-loop oil passage 502, the inner wall of the peach-shaped cam 501 is subjected to differentiated constant-temperature cooling according to the gradient spacing of the peach tip section, the lift and return working surfaces, the base circle section and the profile surface, thereby controlling the hardened layer depth in different areas of the peach-shaped cam 501.

[0048] After the set duration of heat preservation and cooling is completed, the current supply to the induction heating coil is stopped, and the cooling medium is continuously circulated until the overall temperature of the shaft drops to room temperature. Then, the cooling medium in all oil passages inside the shaft is drained, the pipeline connection with the circulation system is disconnected, and the quenching process of the shaft is completed.

[0049] After the quenching process is completed, the shaft body is precision machined. A plug is pressed into the three-section riveting plug mounting hole 601 of the rear sealing shaft head section 6 and riveting seal is completed. On the remaining smooth shaft section 701 of the auxiliary support section 7, the stop washer 703 and the bearing bush 702 are sequentially installed. The locking nut 704 is screwed into the fine thread part of the remaining smooth shaft section 701 to complete the axial locking and positioning of the bearing bush 702. The pre-assembly preparation of the shaft body is completed.

[0050] The machined camshaft is assembled into the engine block, completing the docking assembly of the timing transmission mechanism and lubrication system. When the engine starts running, the pressure lubricating oil of the engine lubrication system is continuously pumped into the central main oil passage 2 through the oil inlet 302 at the bottom of the internal hexagonal forming hole 301 of the front positioning shaft head section 3. During the axial flow of the pressure lubricating oil along the central main oil passage 2, it enters the circumferential cooling oil passage 401 of each support journal section 4 and the contour closed-loop oil passage 502 of each peach-shaped cam 501 through the radial connecting hole 503.

[0051] The pressurized lubricating oil entering the circumferential cooling oil passage 401 is continuously sprayed onto the mating friction surface of the support journal and the bearing through the radially evenly distributed oil spray holes 402 on the outer circumferential surface of the support journal section 4, forming a lubricating oil film. The pressurized lubricating oil entering the contour closed-loop oil passage 502 is continuously sprayed onto the mating friction surface of the cam and the tappet through the evenly distributed oil spray micro-holes 504 on the lift and return working surfaces of the peach-shaped cam 501, forming a lubricating oil film and completing the forced lubrication of the corresponding friction pair.

[0052] During engine operation, the pressure lubricating oil in the central main oil passage 2 passes through the oil passage pressure buffer chamber 602 in the rear sealing shaft head section 6 to complete the pressure fluctuation compensation of the entire oil circuit, maintain the stability of the lubricating oil pressure in each oil passage, and the excess lubricating oil flows back to the engine oil pan through the cylinder block return oil passage to complete the circulation supply of lubricating oil.

[0053] After the engine stops, the lubrication system stops supplying pressurized lubricating oil, and the residual lubricating oil in each oil passage inside the shaft falls back into the central main oil passage 2, completing the entire working cycle.

Claims

1. A camshaft with an optimized hardened layer shape, comprising an integral hollow shaft body (1), characterized in that: The shaft body has a central main oil passage (2) that runs through the entire axial direction. The shaft body is provided with a front positioning shaft head section (3), multiple sets of support journal sections (4), multiple sets of cam sections (5), a rear sealing shaft head section (6), and an auxiliary support section (7) in sequence along the axial direction. The support journal section (4) is provided with a circumferential cooling oil passage (401) arranged in a closed loop along the circumference of the shaft body. The circumferential cooling oil passage (401) is connected to the central main oil passage (2). The outer circular surface of the support journal section (4) is provided with a plurality of radial oil injection holes (402) connected to the circumferential cooling oil passage (401). The cam segment (5) includes at least two peach-shaped cams (501). The interior of the peach-shaped cam (501) is provided with a contoured closed-loop oil passage (502) that matches the contour of the peach-shaped cam (501). The contoured closed-loop oil passage (502) is arranged in a closed loop around the contour of the peach-shaped cam (501). The contoured closed-loop oil passage (502) is connected to the central main oil passage (2) through a radial connecting hole (503). The working surface of the peach-shaped cam (501) is provided with multiple oil injection micro-holes (504) that are connected to the contoured closed-loop oil passage (502).

2. A camshaft with an optimized hardened layer shape according to claim 1, characterized in that: An axially connected oil passage (505) is provided inside the transition section between adjacent peach-shaped cams (501) in the cam group section (5). The axially connected oil passage (505) connects the contour-following closed-loop oil passages (502) of the two peach-shaped cams (501) in the same group to each other.

3. A camshaft with an optimized hardened layer shape according to claim 1, characterized in that: The radial oil injection holes (402) of the support journal section (4) are evenly distributed along the circumference of the shaft body, and the oil injection micro-holes (504) of the peach-shaped cam (501) are only set on the lifting and returning working surfaces of the peach-shaped cam (501) and are evenly distributed along the profile.

4. A camshaft with an optimized hardened layer shape according to claim 1, characterized in that: The cross-section of the contoured closed-loop oil channel (502) is elliptical. The distance between it and the surface of the peach-shaped cam (501) is the largest at the tip of the peach-shaped cam (501), the second largest at the lift and return working surfaces of the peach-shaped cam (501), and the smallest at the base circle of the peach-shaped cam (501), forming a gradient spacing structure that perfectly matches the contact stress distribution of the peach-shaped cam (501). The cross-section of the circumferential cooling oil channel (401) is circular. It is centrally arranged along the axial direction of the support journal section (4) and maintains a uniform radial distance from the outer circle surface of the support journal section (4). It is closed in a complete circle around the shaft. The circumferential cooling oil channel (401) and the contoured closed-loop oil channel (502) are used to introduce cooling medium in the quenching process to accurately control the hardened layer boundary and depth of the corresponding area of ​​the shaft. In the working state, they are used to introduce lubricating oil to achieve forced lubrication and cooling of the corresponding friction surface.

5. A camshaft with an optimized hardened layer shape according to claim 1, characterized in that: The axial end faces of the support journal section (4) and the end faces of the transition section between adjacent peach-shaped cams (501) in the cam group section (5) are provided with dovetail-shaped mutual inductance isolation grooves (8) arranged in a closed loop along the circumference of the shaft. The cross-section of the dovetail-shaped mutual inductance isolation groove (8) is a dovetail-shaped structure with a narrow opening and a wide bottom. The groove is recessed inward along the axial direction of the shaft and is closed in a closed loop around the circumference of the shaft without any breaks. It is used to block the axial current flow during the induction quenching process.

6. A camshaft with an optimized hardened layer shape according to claim 1, characterized in that: The front positioning shaft head section (3) is a coaxial stepped shaft structure. The front positioning shaft head section (3) is provided with an internal hexagonal forming hole (301). The bottom of the internal hexagonal forming hole (301) is provided with an oil inlet (302) that communicates with the central main oil passage (2). The oil inlet (302) of the internal hexagonal forming hole (301) is surrounded by an annular hardened layer limiting groove (303). The outer circular surface of the mating section of the front positioning shaft head section (3) is provided with a non-hardened protective ring band (304).

7. A camshaft with an optimized hardened layer shape according to claim 1, characterized in that: The rear sealing shaft head section (6) is a coaxial stepped shaft structure. The interior of the rear sealing shaft head section (6) is provided with a three-section riveted plug mounting hole (601) that communicates with the central main oil passage (2). An oil passage pressure buffer chamber (602) is provided between the three-section riveted plug mounting hole (601) and the central main oil passage (2). A non-hardened protective ring band two (603) is provided on the outer circular surface of the plug mounting area of ​​the rear sealing shaft head section (6).

8. A camshaft with an optimized hardened layer shape according to claim 1, characterized in that: The auxiliary support section (7) includes a margin optical axis section (701), on the outer side of the margin optical axis section (701) there is a bearing bushing (702), a stop washer (703) is provided on the inner side of the bearing bushing (702), and a locking nut (704) is fixedly connected to the other end of the bearing bushing (702), and the locking nut (704) is threadedly connected to the fine-tooth external thread on the outer side of the margin optical axis section (701).

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