Processing Technology of a Cam Plate for an Electric Limited Slip Differential

Abstract

The present invention discloses a processing technology for a cam plate used in an electric limited-slip differential: S1, preparing raw materials required for processing the cam plate; the raw materials include the following components: C: 0.01-0.40 wt%; Mo: 0.3-1.6 wt%; Mn: 0.05-0.30 wt%; lubricant: 0.3-0.9 wt% and the balance being iron; S2, pressing the raw materials to form a green blank of the cam plate; the green blank includes a cam surface and a bearing mating surface opposite to the cam surface; there is a boss formed during the pressing process on the bearing mating surface, and there is a concave surface left on the cam surface when the boss is formed by pressing; S3, sucking the green blank by a magnetic method to remove the boss on the bearing mating surface; S4, sintering the green blank at a high temperature; S5, densifying the bearing mating surface after sintering; S6, performing carbonitriding to form a first hardened layer and a second hardened layer on the cam surface and the bearing mating surface respectively; S7, removing part of the second hardened layer by finish machining to form a third hardened layer; thus obtaining the cam plate. The processing technology for the cam plate provided by the present invention has a lower cost and a shorter processing cycle.

Description

Technical Field

[0001] The present invention relates to the technical field of automotive parts, and particularly relates to a processing technology for a cam plate used in an electric limited slip differential. Background Art

[0002] The working principle of a limited slip differential is as follows: (1) The mechanical self-locking differential was developed by automotive technologists when electronic technology was not yet developed. It operates entirely by mechanical structure. Although the structure is reliable, its functions are relatively single, and some structures also have higher requirements for driving skills. Common types include friction plate type, cam slider type, and Torsen type mechanical limited slip differentials; (2) The friction plate type self-locking differential uses the friction plates inside the differential to prevent slipping during differential rotation. Its structure is simple and is widely used in cars and other vehicle models. In addition, there are also cone plate type limited slip differentials with a similar working principle, as well as LSDs that combine the two characteristics, all of which belong to the type that is sensitive to torque; (3) Cam slider type limited slip differential: This type of limited slip differential uses inertial swinging of the slider to achieve self-locking, so a large speed difference between the two wheels is required. It belongs to the speed-sensitive type LSD (there is also a viscous coupling LSD of the same type, which is now rarely used); The cam slider type LSD has limited usage conditions (it may already be stuck in the mud at this time). Its advantage is strong locking ability and is mostly used in hardcore SUVs, pickups and other vehicle models.

[0003] The conventional limited slip differential uses a mechanical inertial locking differential, which has a simple structure, is stable and reliable, but has a high control difficulty. The locking function cannot be manually controlled. When it is changed to an electronic differential, the key part, the cam plate, is not easy to process. Special steel is often used for processing. Because it needs to operate well under magnetic control, there are requirements for magnetic attraction reaction. At the same time, for the long-term operation of the cam plate and the ejector rod, the parts are also required to have high strength and wear resistance, so they can only be made of special steel.

[0004] However, when manufacturing cam plates with existing special steel, there are problems such as high cost, long development and processing cycles; when using powder metallurgy parts for production, on the one hand, it is necessary to take into account the excellent magnetic properties of powder metallurgy parts, and on the other hand, it is necessary to have high strength and wear resistance, and there are conflicts in the performance guarantee aspect. For example, high strength and high wear resistance require high alloying elements and carbon equivalent in the material, but in this case, the magnetic properties of the parts will decline and cannot be unified. Summary of the Invention

[0005] The object of the present invention is to propose a processing technology for a cam plate used in an electric limited slip differential to solve the problems of high cost and long processing cycle existing in the existing cam plate manufacturing process, as well as the problem that the strength, wear resistance and magnetic properties of the parts cannot be taken into account at the same time.

[0006] The present invention is realized through the following technical solutions:

[0007] A processing technology for a cam plate used in an electric limited-slip differential, characterized in that the technology comprises the following steps:

[0008] S1. Raw material batching: Prepare the raw materials required for processing the cam plate; the raw materials include the following components: C: 0.01 - 0.40 wt%; Mo: 0.3 - 1.6 wt%; Mn: 0.05 - 0.30 wt%; lubricant: 0.3 - 0.9 wt% and the balance is iron.

[0009] S2. Compression molding: Press the raw materials in a molding die to form a green blank of the cam plate; the green blank of the cam plate includes: a cam surface and a bearing mating surface opposite to the cam surface; there is a boss formed during the pressing process on the bearing mating surface; there is a concave surface left on the cam surface when the boss is formed by pressing.

[0010] S3. Rough machining of the green blank: Absorb the green blank of the cam plate by magnetic means, and then remove the boss on the bearing mating surface.

[0011] S4. Sintering: Place the rough-machined green blank of the cam plate in a sintering furnace for high-temperature sintering under a protective atmosphere.

[0012] S5. Local densification treatment: Extrude and densify the bearing mating surface of the cam plate after sintering.

[0013] S6. Carbonitriding treatment: Perform carbonitriding heat treatment on the cam plate to form a first hardened layer on the cam surface and a second hardened layer on the bearing mating surface.

[0014] S7. Finish machining: Remove part of the second hardened layer by finish machining to ensure the magnetic properties of the cam plate, and a third hardened layer is formed after removal; finally, the cam plate for the electric limited-slip differential is processed through the above process.

[0015] Specifically, there is a magnetic attraction part on the bearing mating surface to ensure the magnetic properties of the cam plate. After the carbonitriding treatment in step S6, a second hardened layer will be formed on the entire surface of the bearing mating surface, which will have a certain impact on the magnetic properties of the cam plate. Therefore, after the finish machining in step S7, the hardened layer material at the magnetic attraction part is removed to ensure the magnetic properties of the cam plate. Among them: the third hardened layer is the second hardened layer after removing part of the material, that is, the second hardened layer after being reduced.

[0016] Further, a processing technology for a cam plate used in an electric limited-slip differential: The raw materials described in step S1 include the following components: C: 0.05 - 0.40 wt%; Mo: 0.5 - 1.6 wt%; Mn: 0.10 - 0.30 wt%; lubricant: 0.3 - 0.5 wt% and the balance is iron.

[0017] Further, a processing technology for a cam plate used in an electric limited-slip differential: Step S2, pressing and forming: Press the above raw materials in a forming press of 500 - 1000T to obtain a green cam plate blank.

[0018] The green cam plate blank includes: a cam surface and a bearing mating surface opposite to the cam surface; there is a boss formed during the pressing process on the bearing mating surface; there is a concave surface left on the cam surface when the boss is formed by pressing.

[0019] The local density of the concave surface is 7.15 - 7.30 g / cm 3 ; the density of the green cam plate blank except the concave surface is 7.0 - 7.1 g / cm 3 .

[0020] Further, a processing technology for a cam plate used in an electric limited-slip differential: Step S3, rough machining of the green blank: Absorb the green cam plate blank by a magnetic fixture, and then remove the boss on the bearing mating surface by a roll pressing method.

[0021] Further, a processing technology for a cam plate used in an electric limited-slip differential: The sintering temperature in step S4 is 1100 - 1140 °C, and the sintering time is 20 - 40 minutes.

[0022] Further, a processing technology for a cam plate used in an electric limited-slip differential: The protective atmosphere described in step S4 is a mixed gas of nitrogen and hydrogen, and the volume ratio of nitrogen to hydrogen is (4 - 25):1.

[0023] Further, a processing technology for a cam plate used in an electric limited-slip differential: Step S5, local densification treatment: After sintering, extrude and densify the bearing mating surface of the cam plate by a press of 300 - 500T; the density of the surface layer of the bearing mating surface after densification is 7.15 - 7.30 g / cm 3 .

[0024] Specifically, the surface layer refers to the part within 0.2 mm thickness from the surface of the bearing mating surface, and its density is 7.15 - 7.30 g / cm 3 .

[0025] Further, a processing technology for a cam plate used in an electric limited-slip differential: Step S6, carbonitriding treatment: The cam plate is subjected to carbonitriding heat treatment at 800-930 °C, a first hardened layer with a thickness of 0.2-0.4 mm is formed on the cam surface, and a second hardened layer with a thickness of 0.2-0.4 mm is formed on the bearing mating surface; the hardness of the first hardened layer and the second hardened layer > 57 HRC.

[0026] Advantages of the present invention:

[0027] (1) In the processing technology for the cam plate used in the electric limited-slip differential provided by the present invention, a magnetic method is adopted to absorb and fix the green blank of the cam plate during green blank processing, and then the green blank is processed. It can effectively avoid cracks generated during the processing of the part green blank, greatly improve the processing efficiency and tool life, and significantly reduce the production cost. The magnetic absorption method adopted in the process of the present invention can avoid the risk of clamping and damaging the part and causing cracks in the part due to the low strength of the green blank compared with the traditional three-jaw type fixture.

[0028] (2) Through the improvement of the raw material formula, the present invention uses a raw material formula with low alloy and low carbon content to make the cam plate, which can ensure the magnetic properties of the processed parts; at the same time, the present invention controls the pressing density of the key parts to improve the strength of the parts in the functional area.

[0029] (3) In the processing technology of the present invention, a local extrusion densification process is adopted for the bearing mating surface, which increases the fatigue strength of the bearing mating surface; the process of the present invention also adopts carbonitriding for surface treatment to form a hardened layer on the cam surface and the bearing mating surface, improving the wear resistance of the cam plate parts.

[0030] (4) The present invention also adopts a process of precision machining to remove the excess hardened layer at the magnetic absorption part of the cam plate, further improving the magnetic properties of the parts. The processing technology of the present invention has a low cost and a short processing cycle. Using the process of the present invention, a cam plate for an electric limited-slip differential that takes into account wear resistance and part magnetic properties can be processed. Description of the drawings

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0032] Figures 1-2 It is a schematic structural diagram of the green blank of the cam plate formed by pressing in the present invention;

[0033] Figure 3It is a sectional view of the cam plate formed by processing the present invention, and Figure 3 a first hardened layer obtained after being processed through step S6 is formed on the cam surface;

[0034] Figure 4 It is a sectional view of the cam plate formed by processing the present invention, and Figure 4 a second hardened layer obtained after being subjected to carbonitriding treatment through step S6 is formed on the bearing mating surface;

[0035] Figure 5 It is a sectional view of the cam plate formed by processing the present invention, and Figure 5 a third hardened layer obtained after being removed through finish machining in step S7 is formed on the bearing mating surface.

[0036] Markings in the figure: 1 green body of cam plate, 1-1 cam surface, 1-2 bearing mating surface, 1-1-1 concave surface, 1-1-2 first hardened layer, 1-2-1 convex platform, 1-2-2 second hardened layer, 1-2-3 third hardened layer. Specific Embodiments

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way limits the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0038] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "top", "bottom", etc. is 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 thus cannot be understood as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. Moreover, the terms "first", "second", etc. are used to distinguish similar objects and do not have to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein.

[0039] Embodiment 1

[0040] A processing technology for a cam plate used in an electric limited-slip differential is provided, characterized in that the technology includes the following steps:

[0041] S1. Raw material batching: Prepare the raw materials required for processing the cam plate; the raw materials include the following components: C: 0.1 wt%; Mo: 0.3 wt%; Mn: 0.2 wt%; lubricant: 0.7 wt% and the balance is iron.

[0042] S2. Compression molding: Press the raw materials in a 500T molding press to obtain a green cam plate 1 (as Figures 1-2 shown);

[0043] Among them: the green cam plate 1 includes: a cam surface 1-1 and a bearing mating surface 1-2 opposite to the cam surface 1-1; there is a boss 1-2-1 formed during the pressing process on the bearing mating surface 1-2; the cam surface 1-1 has a concave surface 1-1-1 left when forming the boss 1-2-1, and the local density of the concave surface 1-1-1 is 7.15 - 7.30 g / cm 3 , and the density of the part of the green cam plate 1 other than the concave surface 1-1-1 is 7.0 - 7.1 g / cm 3 ;

[0044] S3. Green blank rough machining: Absorb and fix the green cam plate 1 through a magnetic fixture, and then remove the boss 1-2-1 on the bearing mating surface 1-2 by roll pressing;

[0045] S4. Sintering: Place the rough-machined green cam plate 1 in a sintering furnace and sinter it at 1120 °C for 30 minutes under a mixed atmosphere of nitrogen and hydrogen;

[0046] S5. Local densification treatment: After sintering, extrude and densify the bearing mating surface 1-2 of the cam plate with a 300T press; after densification, the density of the surface layer of the bearing mating surface 1-2 is 7.15 - 7.30 g / cm 3 ;

[0047] S6. Carbonitriding treatment: Perform carbonitriding heat treatment on the cam plate at 880 °C to form a first hardened layer 1-1-2 with a thickness of 0.3 mm on the cam surface 1-1 and a second hardened layer 1-2-2 with a thickness of 0.3 mm on the bearing mating surface 1-2 (as Figures 3-4 shown);

[0048] S7. Finish machining: Finish machining to remove the second hardened layer 1-2-2 at the magnetically attracted part on the bearing mating surface 1-2. After removal, it is used to ensure the magnetic performance of the cam plate. After removing part of the second hardened layer 1-2-2, a third hardened layer 1-2-3 is formed (asFigure 5 As shown in the figure, the hardness of the first hardened layer 1-1-2 and the second hardened layer 1-2-2 > 57 HRC; finally, the cam plate for the electric limited-slip differential is obtained through the processing steps S1 to S7 above.

[0049] Through the improvement of the raw material formula, the present invention uses a raw material formula with low alloy and low carbon content to make the cam plate, which can ensure the magnetic properties of the processed cam plate parts; and the present invention has a finishing step in the process to remove the hardened layer on the magnetic adsorption part of the bearing mating surface, further ensuring the magnetic properties while ensuring the wear resistance of the parts.

[0050] Example 2

[0051] Provide a processing technology for a cam plate for an electric limited-slip differential, characterized in that the technology includes the following steps:

[0052] S1. Raw material batching: Prepare the raw materials required for processing the cam plate; the raw materials include the following components: C: 0.01 wt%; Mo: 1.5 wt%; Mn: 0.05 wt%; lubricant: 0.3 wt% and the balance is iron.

[0053] S2. Compression molding: Press the raw materials in a 1000T molding press to obtain the green cam plate 1 (as Figures 1-2 shown);

[0054] Among them: the green cam plate 1 includes: a cam surface 1-1 and a bearing mating surface 1-2 opposite to the cam surface 1-1; a boss 1-2-1 formed during the pressing process is provided on the bearing mating surface 1-2; the cam surface 1-1 has a concave surface 1-1-1 left when forming the boss 1-2-1, and the local density of the concave surface 1-1-1 is 7.15 - 7.30 g / cm 3 , and the density of the part of the green cam plate 1 other than the concave surface 1-1-1 is 7.0 - 7.1 g / cm 3 ;

[0055] S3. Green blank rough machining: Absorb and fix the green cam plate 1 through a magnetic fixture, and then remove the boss 1-2-1 on the bearing mating surface 1-2 by roll pressing;

[0056] S4. Sintering: Place the rough machined green cam plate 1 in a sintering furnace and sinter it at 1100 °C for 40 minutes in a mixed atmosphere of nitrogen and hydrogen;

[0057] S5. Local densification treatment: After sintering, the bearing mating surface 1-2 of the cam plate is extruded and densified by a 500T press; after densification, the density of the surface layer of the bearing mating surface 1-2 is 7.15 - 7.30 g / cm 3 ;

[0058] S6. Carbonitriding treatment: The cam plate is subjected to carbonitriding heat treatment at 800 °C, a first hardened layer 1-1-2 with a thickness of 0.4 mm is formed on the cam surface 1-1, and a second hardened layer 1-2-2 with a thickness of 0.4 mm is formed on the bearing mating surface 1-2 (as Figures 3-4 shown);

[0059] S7. Finish machining: The second hardened layer 1-2-2 at the magnetic attraction part on the bearing mating surface 1-2 is removed by finish machining, and after removal, it is used to ensure the magnetic properties of the cam plate. After removing part of the second hardened layer 1-2-2, a third hardened layer 1-2-3 is formed (as Figure 5 shown); Finally, the cam plate for the electric limited-slip differential is obtained through the above steps S1 - S7.

[0060] Example 3

[0061] A processing technology for a cam plate for an electric limited-slip differential is provided, characterized in that the technology includes the following steps:

[0062] S1. Raw material batching: Prepare the raw materials required for processing the cam plate; the raw materials include the following components: C: 0.3 wt%; Mo: 0.9 wt%; Mn: 0.3 wt%; lubricant: 0.5 wt% and the balance is iron;

[0063] S2. Compression molding: Compress the raw materials in an 800T molding press to obtain a green cam plate 1 (as Figures 1-2 shown);

[0064] Among them: The green cam plate 1 includes: a cam surface 1-1 and a bearing mating surface 1-2 opposite to the cam surface 1-1; a boss 1-2-1 formed during the pressing process is provided on the bearing mating surface 1-2; a concave surface 1-1-1 left when forming the boss 1-2-1 is provided on the cam surface 1-1, and the local density of the concave surface 1-1-1 is 7.15 - 7.30 g / cm 3 , and the density of the part of the green cam plate 1 other than the concave surface 1-1-1 is 7.0 - 7.1 g / cm 3 ;

[0065] S3. Rough machining of the green blank: The green cam plate 1 is fixed by magnetic clamping, and then the boss 1-2-1 on the bearing mating surface 1-2 is removed by rolling

[0066] S4, Sintering: Under a mixed atmosphere of nitrogen and hydrogen, place the green blank 1 of the cam plate after rough machining into a sintering furnace and sinter it at a high temperature of 1140 °C for 10 minutes;

[0067] S5, Local densification treatment: After sintering, extrude and densify the bearing mating surface 1-2 of the cam plate with a 400T press; after densification, the density of the surface layer of the bearing mating surface 1-2 is 7.15 - 7.30 g / cm 3 ;

[0068] S6, Carbonitriding treatment: Perform carbonitriding heat treatment on the cam plate at 930 °C, form a first hardened layer 1-1-2 with a thickness of 0.2 mm on the cam surface 1-1, and form a second hardened layer 1-2-2 with a thickness of 0.2 mm on the bearing mating surface 1-2 (as Figures 3-4 shown);

[0069] S7, Finish machining: Remove the second hardened layer 1-2-2 at the magnetic attraction part on the bearing mating surface 1-2 during finish machining. After removal, it is used to ensure the magnetic properties of the cam plate. After removing part of the second hardened layer 1-2-2, a third hardened layer 1-2-3 is formed (as Figure 5 shown); Finally, the cam plate for an electric limited-slip differential is obtained through the above steps S1 - S7.

[0070] The above are the preferred embodiments of the present invention, which are only used to explain the present invention and are not used to limit the present invention. Any obvious changes or variations derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A processing technology for a cam plate used in an electric limited slip differential, characterized in that, The process includes the following steps: S1. Raw material batching: Prepare the raw materials required for processing the cam plate; the raw materials include the following components: C: 0.01 - 0.40 wt%; Mo: 0.3 - 1.6 wt%; Mn: 0.05 - 0.30 wt%; Lubricant: 0.3 - 0.9 wt% and the balance is iron; S2. Compression molding: Press the raw materials in a molding die to obtain a green cam plate (1); the green cam plate (1) includes: a cam surface (1-1) and a bearing mating surface (1-2) opposite to the cam surface (1-1); a boss (1-2-1) formed during the pressing process is provided on the bearing mating surface (1-2); a concave surface (1-1-1) left when forming the boss (1-2-1) is provided on the cam surface (1-1); S3. Green blank rough machining: Absorb the green cam plate (1) by magnetic means, and then remove the boss (1-2-1) on the bearing mating surface (1-2); S4. Sintering: Place the rough machined green cam plate (1) in a sintering furnace for high-temperature sintering under a protective atmosphere; S5. Local densification treatment: Extrude and densify the bearing mating surface (1-2) of the cam plate after sintering; S6. Carbonitriding treatment: Perform carbonitriding heat treatment on the cam plate to form a first hardened layer (1-1-2) on the cam surface (1-1) and a second hardened layer (1-2-2) on the bearing mating surface (1-2); S7. Finish machining: Remove part of the second hardened layer (1-2-2) by finish machining to ensure the magnetic properties of the cam plate, and a third hardened layer (1-2-3) is formed after removal; finally, a cam plate for an electric limited-slip differential is obtained.

2. The processing technology of a cam plate for an electric limited-slip differential according to claim 1, characterized in that, The raw materials described in step S1 include the following components: C: 0.05 - 0.40 wt%; Mo: 0.5 - 1.6 wt%; Mn: 0.10 - 0.30 wt%; Lubricant: 0.3 - 0.5 wt% and the balance is iron.

3. The processing technology of a cam plate for an electric limited slip differential according to claim 1, characterized in that, Step S2. Compression molding: Press the raw materials in a molding press with a pressure of 500 - 1000T to obtain a green cam plate (1); The green cam plate (1) includes: a cam surface (1-1) and a bearing mating surface (1-2) opposite to the cam surface (1-1); a boss (1-2-1) formed during the pressing process is provided on the bearing mating surface (1-2); a concave surface (1-1-1) left when forming the boss (1-2-1) is provided on the cam surface (1-1); The local density of the concave surface (1-1-1) is 7.15 to 7.30 g / cm 3 ; the density of the green cam plate (1) except for the concave surface (1-1-1) is 7.0 to 7.1 g / cm 3 .

4. The processing technology of a cam plate for an electric limited slip differential according to claim 1, characterized in that, Step S3. Green blank rough machining: Absorb the green cam plate (1) by a magnetic fixture, and then remove the boss (1-2-1) on the bearing mating surface (1-2) by roll pressing.

5. The processing technology of a cam plate for an electric limited-slip differential according to claim 1, characterized in that, The sintering temperature in step S4 is 1100 - 1140 °C, and the sintering time is 20 - 40 minutes.

6. The processing technology of a cam plate for an electric limited-slip differential according to claim 1, characterized in that, The protective atmosphere described in step S4 is a mixed gas of nitrogen and hydrogen, and the volume ratio of nitrogen to hydrogen is (4 - 25):

1.

7. The processing technology of a cam plate for an electric limited slip differential according to claim 1, characterized in that, Step S5, local densification treatment: After sintering, the bearing mating surface (1-2) of the cam plate is extruded and densified by a press of 300-500T; after densification, the density of the surface layer of the bearing mating surface (1-2) is 7.15-7.30 g / cm 3 .

8. The processing technology of a cam plate for an electric limited-slip differential according to claim 1, characterized in that, Step S6, carbonitriding treatment: The cam plate is subjected to carbonitriding heat treatment at 800 - 930 °C, a first hardened layer (1-1-2) with a thickness of 0.2 - 0.4 mm is formed on the cam surface (1-1), and a second hardened layer (1-2-2) with a thickness of 0.2 - 0.4 mm is formed on the bearing mating surface (1-2); The hardness of the first hardened layer (1-1-2) and the second hardened layer (1-2-2) > 57 HRC.

Images