High frequency direct current quenching coil for rack bar

Abstract

To provide a direct current quenching coil for a rack bar capable of cooling a dielectric coil during application of a high frequency current and simultaneously injecting quenching water toward the rack bar without increasing the number of components.SOLUTION: There is provided a high-frequency direct-energization quenching coil 3 for a rack bar 1 being a rack bar direct current quenching coil that directly heats a surface of the rack bar 1 to be quenched and performs a high frequency induction heating of the surface by a direct current quenching coil 10 disposed along the surface. Therein: the direct current quenching coil 10 is formed by a metal additive manufacturing method; a cavity 25 is provided inside; and a large number of quenching liquid jet water passages 5 that pass through the cavity 25 of the direct current quenching coil 10 and pass quenching liquid are provided; and the cavity 25 serves as a cooling water flow passage through which cooling water for cooling the direct-energization quenching coil 10 passes.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a direct current hardening coil used for surface hardening of a rack bar. [Background technology]

[0002] Some automobile steering shafts have a rack bar formed on them. The rack bar of the handle shaft needs to be hardened to improve its wear resistance. One method for hardening the surface of the rack bar is induction hardening using a direct current hardening coil. Figure 8 shows a conventional direct current hardening coil used for this induction hardening.

[0003] A conventional direct current hardening coil includes a rectangular cylindrical induction coil 11 supported horizontally on a base. The induction coil 11 also serves as a quenching jacket and has numerous quenchant ejection holes 12 on its top surface. A pressure equalizing plate 13 is disposed inside the induction coil 11. The pressure equalizing plate 13 has numerous quenchant passage holes 14. A first contact 15 is attached to the top surface of one end of the induction coil 11, and a lead 16 is attached to the bottom surface of the other end. A second contact 17 is disposed at the other end of the induction coil 11, and a lead 18 is also attached to its bottom surface.

[0004] The rack bar W to be hardened is placed on the contacts 15, 17, straddling them, and is pressed down by a work holder from above the contacts 15, 17, so that the undersides of both ends are pressed against the contacts 15, 17. When the high-frequency power supply connected to the leads 16, 18 is activated, a high-frequency current flows through the induction coil 11 to the surface layer of the lower surface of the rack bar W, and the surface layer is heated by electrical current. The high-frequency current flowing through the induction coil 11 also heats the surface layer of the lower surface of the rack bar W.

[0005] When the lower surface layer of the rack bar W is heated to a predetermined quenching temperature, quenching liquid is introduced into the induction coil 11. As a result, quenching liquid is ejected upward from the quenching liquid ejection holes 12 of the induction coil 11, and the lower surface layer of the rack bar W is rapidly cooled to form a predetermined quenched structure.

[0006] However, since there are many quenching liquid ejection holes on the surface of the induction coil 11, it is not possible to provide a cooling water pipe inside the induction coil 11 to cool the induction coil itself, which causes the induction coil 11 to overheat and shortens its lifespan. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Utility Model Application Publication No. 6-23194 Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, Patent Document 1 describes that the induction coil has a cylindrical main body, a partition plate that divides the inside of the main body into a work side and an opposite side, a coolant inlet hole provided in the main body to circulate coolant in the space on the work side within the main body, and a number of quenching liquid ejection pipes that penetrate the space on the work side of the main body to eject the quenching liquid introduced into the space on the opposite side of the main body onto the work side of the main body.

[0009] In Patent Document 1, a partition plate is required to separate the inside of the induction coil body into a work side and an opposite side, which increases the number of parts and increases costs.

[0010] The present invention allows the rack bar side of the induction coil, where heat generation is concentrated, to be cooled while high-frequency current is being passed through it, and also allows quenching water to be sprayed toward the rack bar at the same time. Furthermore, the rack bar can be rapidly cooled by spraying quenching liquid at reduced water pressure onto the rack bar using multiple quenching liquid spray channels. Furthermore, the present invention provides a direct current hardening coil for the rack bar, which can be processed within the induction coil using metal additive manufacturing technology without increasing the number of parts. [Means for solving the problem]

[0011] An aspect for solving the above-described problems is a rack bar direct current hardening coil that directly heats the surface of a rack bar to be hardened by electrical current and high-frequency induction heats the surface by an induction coil arranged along the surface, the induction coil being made by metal additive manufacturing and having a cavity therein, with multiple quenching liquid ejection channels penetrating the cavities of the induction coil through which quenching liquid passes, and the cavities serving as cooling water flow channels through which cooling water passes for cooling the induction coil.

[0012] According to this embodiment, the induction coil is made by metal additive manufacturing, has a cavity inside, and has a number of quenching liquid jetting channels that pass through the cavities of the induction coil and allow quenching liquid to flow through them, and the cavities are high-frequency direct current hardening coils of the rack bar that serve as cooling water flow channels through which cooling water flows to cool the induction coil.Therefore, the quenching liquid jetting channels and cooling water flow channels can be provided separately without increasing the number of parts, and the induction coil and rack bar can be cooled.

[0013] In this embodiment, the quenching liquid jetting channel and the cooling water flow channel are both independent within the induction coil, and it is preferable that the part of the cavity excluding the quenching liquid jetting channel is a high-frequency direct current hardening coil of the rack bar which serves as the cooling water flow channel.

[0014] According to this embodiment, the quenching liquid jetting channel and the cooling water flow channel are both independent within the induction coil, and the part of the cavity excluding the quenching water jetting channel is the high-frequency direct current quenching coil of the rack bar, which serves as the cooling water flow channel. Therefore, quenching liquid and cooling water can be flowed at the same time, and the rack bar can be cooled appropriately while cooling the induction coil.

[0015] In this embodiment, the quenching liquid jetting waterway is preferably a high-frequency direct current hardening coil of a rack bar having a trumpet shape in which the diameter of the water inlet is larger than the diameter of the water outlet.

[0016] According to this embodiment, the quenching liquid jetting waterway is a high-frequency direct current hardening coil with a rack bar that is trumpet-shaped, with the diameter of the water inlet being larger than the diameter of the water outlet. Therefore, in the induction coil where current is concentrated, current also concentrates in the quenching liquid jetting waterway inside the induction coil, but by making the water inlet trumpet-shaped, it is possible to prevent cracks and the like from occurring.

[0017] This embodiment is a rack bar high frequency direct current hardened coil in which the center of the top surface of the induction coil is lowest and the height increases toward the ends.

[0018] According to this embodiment, the thermal energy applied to the rack bar during hardening is not concentrated too much in the center and is approximately equal to the thermal energy applied to the ends, so that the hardening temperature of the entire rack bar can be made uniform. [Effects of the Invention]

[0019] According to the high-frequency direct current hardening coil of this embodiment, the cooling water for cooling the induction coil and the quenching liquid for cooling the rack bar are separated inside the device, so that the induction coil can be cooled while high-frequency current is being passed through, and the rack bar can also be cooled appropriately regardless of the cooling status of the induction coil, so that the induction coil will not overheat, and when the rack bar is heated to the specified quenching temperature, the quenching liquid is sprayed onto the rack bar, which rapidly cools the surface layer of the lower surface of the rack bar and forms the specified quenched structure. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 2 is a perspective view of a rack bar to be hardened by the induction hardening coil of the present invention. [Figure 2] 1 is a schematic cross-sectional view of an apparatus using a high-frequency direct current hardening coil for a rack bar according to the present invention. [Figure 3] 1 is a cross-sectional perspective view of a high-frequency direct current hardening coil for a rack bar according to the present invention. FIG. [Figure 4] 1 is a cross-sectional view of a high-frequency direct current hardening coil for a rack bar according to the present invention. [Figure 5] 1 is a cross-sectional view of a high-frequency direct current hardening coil mounting portion for a rack bar according to the present invention. [Figure 6] 1 is a perspective view showing a cooling water supply port of a high-frequency direct current hardening coil for a rack bar according to the present invention, and the inside of the circle is an enlarged view of an R-shape. FIG. [Figure 7] 1 is a schematic diagram of a manufacturing system for manufacturing a high-frequency direct current hardening coil for a rack bar according to the present invention. [Figure 8] FIG. 1 is a side view of a conventional direct current hardening coil. DETAILED DESCRIPTION OF THE INVENTION

[0021] Prior to describing the embodiments of the present invention, a rack bar to be hardened by the hardening apparatus of the present invention will be described. FIG. 1 is a perspective view of a rack bar to be hardened by the hardening device of the present invention. The rack bar 1 to be hardened by the hardening device is a long bar used as a steering shaft for an automobile. One side of the rack bar 1 is chamfered, and a rack 2 is formed in the chamfered portion. The rack bar hardening device described below hardens the rack bar 1 shown in Figure 1, and performs high-frequency direct current hardening on the rack 2 portion of the rack bar 1.

[0022] As shown in FIG. 2, the high-frequency direct current hardening coil 3 of the present invention is used for hardening the rack bar 1.

[0023] As shown in Figures 2 to 6, the direct current hardening coil 10 provided in the high-frequency direct current hardening coil 3 of the present invention has a main body 4 made of a steel pipe with a rectangular cross section and a bottom 40. The main body 4 is fixed horizontally on a base with one side facing upward. Both ends of the main body 4 are closed, and a number of quenching liquid ejection holes 62 are opened at a predetermined pitch on an upper surface 61. In addition, contacts 20, 21 are protruding from both ends.

[0024] A cavity 25 is provided inside the main body 4. A large number of quenching liquid jet channels 5 for passing quenching liquid are provided, vertically penetrating the cavity 25. Cooling water for cooling the direct current hardening coil 10 can be passed through the cavity 25.

[0025] When a high-frequency power supply (not shown) connected to the lead 58 is turned on, a high-frequency current flows through the main body 4 to the surface layer of the lower surface of the rack bar 1, and the surface layer is electrically heated. The high-frequency current flowing through the main body 4 also heats the surface layer of the lower surface of the rack bar 1.

[0026] The high-frequency direct current hardening coil 3 becomes hot due to the high-frequency current. Therefore, in order to cool the high-frequency direct current hardening coil 3, cooling water is supplied from a cooling water supply source (not shown) to the cavity 25 via a cooling water supply port 30 and a cooling water supply channel 31 shown in Fig. 6, thereby cooling the high-frequency direct current hardening coil 3. The cooling water that has cooled the high-frequency direct current hardening coil 3 is discharged from a cooling water discharge port (not shown) of the high-frequency direct current hardening coil 3.

[0027] When the surface layer of the lower surface of the rack bar 1 is heated to a predetermined quenching temperature by high-frequency current, quenching liquid flows from a quenching liquid supply source (not shown) through the quenching liquid supply port 22 shown in Fig. 2 into the quenching liquid reservoir chamber 32. At this time, the quenching liquid is under high pressure, and the water pressure of the quenching liquid is reduced by a pressure equalizing plate 35 installed in the quenching liquid reservoir chamber 32. The pressure equalizing plate 35 has a large number of holes 37 penetrating it, through which the quenching liquid passes, and the water pressure of the quenching liquid can be reduced by the quenching liquid passing through the large number of holes 37.

[0028] The lower part of the quenching liquid jetting waterway 5 is connected to the quenching liquid reservoir chamber 32, and the quenching liquid that flows into the quenching liquid reservoir chamber 32 passes through the quenching liquid jetting waterway 5 and is jetted onto the rack bar 1, causing the rack bar 1 to be rapidly cooled.

[0029] 4, the connection 52 between the main body 4 and the bottom 40 is rounded. As shown in FIG. 6, the step 60 on the top surface 61 of the main body 4 is also rounded. The rounded shape is used to prevent stress concentration and damage to the high-frequency direct current hardening coil 3. The quenching liquid jet channel 5 has a trumpet-shaped inlet on the side of the quenching liquid reservoir 32. This trumpet-shaped inlet 54 prevents cracks and damage to the high-frequency direct current hardening coil 3, on which high-frequency current is concentrated.

[0030] 2 and 6, the upper surface 61 of the direct current hardening coil 10 is lowest in the longitudinal center and becomes higher toward the ends. As a result, the thermal energy applied to the rack bar 1 during hardening is not concentrated too much in the center and is approximately equal to the thermal energy applied to the ends, so that the hardening temperature of the entire rack bar 1 can be made uniform.

[0031] The cavity 25 in the high-frequency direct current hardening coil 3, the R-shape of the connection portion 52, the R-shape of the step 60, and the trumpet-shaped portion 54 of the quenching liquid jet channel 5 are manufactured using metal lamination technology. Metal additive manufacturing is a technology that builds up layers of metal powder to create three-dimensional shapes. Metal materials used in metal 3D printers include steel, aluminum, titanium, and copper, but in this embodiment, steel-based powder was used.

[0032] In the direct current hardened coil manufactured by metal additive manufacturing according to this embodiment, a powder bed method is used to create a metal body with the desired three-dimensional structure (a three-dimensional structure). First, slice data is created by slicing three-dimensional computer-aided design (CAD) data of the desired metal body. Based on the slice data for each layer created, a laser is irradiated using a metal additive manufacturing device (not shown), forming metal layers by sintering metal powder layer by layer. The above procedure is then repeated to finally create a three-dimensional metal body.

[0033] As shown in FIG. 7, the specific manufacturing system 56 includes a CAD device 41, a data conversion device 42, and a manufacturing device 43.

[0034] The CAD device 41 is, for example, a 3D-CAD device capable of three-dimensionally displaying images on a screen. In this embodiment, the CAD device 41 includes a computer and software installed on the computer. A designer of the high-frequency direct current hardening coil 3 operates the CAD device 41 to create CAD data for producing the high-frequency direct current hardening coil 3. The CAD data created by the CAD device 41 is output to a data conversion device 42.

[0035] The data conversion device 42 is provided as a device for converting CAD data into data for operating the manufacturing device 43. In this embodiment, the data conversion device 42 includes a computer and software installed on the computer.

[0036] The data conversion device 42 divides a three-dimensional image of the high-frequency direct current hardening coil 3 specified by, for example, CAD data into a plurality of layer images obtained by slicing the high-frequency direct current hardening coil 3 at predetermined intervals along the vertical direction of the high-frequency direct current hardening coil 3, and stores data of the plurality of layer images. The predetermined intervals correspond to the thickness of one layer of metal powder to be layered in the manufacturing device 43, and are, for example, approximately several tens of μm. The data of the plurality of layer images is provided to the manufacturing device 43.

[0037] The manufacturing apparatus 43 is an apparatus for melting and sintering metal powder. In this embodiment, the manufacturing apparatus 43 forms the high-frequency direct current hardened coil 3 by, for example, selective laser melting. In this embodiment, the manufacturing apparatus 43 has a laser light source 44, a control unit 45, a movable table 46, and a powder supply unit 47.

[0038] The laser light source 44 is provided to apply thermal energy to the metal powder. The laser beam from the laser light source 44 may be irradiated at a desired position on the metal powder by displacing the laser light source 44 itself using a driving device (not shown), or the laser light source 44 may be fixed and irradiated at a desired position using a galvanometer mirror. The laser light source 44 is controlled by a control unit 45.

[0039] The control unit 45 includes a CPU, RAM, ROM, etc., and receives data from the data conversion device 42. The control unit 45 controls the laser light source 44, the movable table 46, and the powder supply unit 47. More specifically, the control unit 45 determines the irradiation dose of the laser beam on a predetermined location on the metal powder based on the image data received from the data conversion device 42, and irradiates the predetermined location on the metal powder with the laser beam based on the determined irradiation dose. The irradiation dose of the laser beam may be set by the data conversion device 42.

[0040] By using this metal additive manufacturing technology, it is possible to use 3D-CAD data to simultaneously form the quenching liquid jetting channel 5 inside the direct current hardening coil 10. In addition, the 3D-CAD data is used to manufacture the cavity 25 inside the direct current hardening coil 10, the R-shape of the connecting portion 52, the R-shape of the step 60, the trumpet-shaped portion 54 of the quenching liquid jetting channel 5, and the like.

[0041] In this way, by manufacturing a high-frequency electromagnetic coil using metal additive manufacturing technology, it is possible to separate the flow channels for the quenching liquid and the cooling water without using any extra parts, so that the quenching liquid and the cooling water can be used at the appropriate timing to appropriately cool the direct current hardened coil 10 and the rack bar 1. Furthermore, it is now possible to process the cavity 25 in the direct current hardened coil 10, the R-shape of the connecting portion 52, the R-shape of the step 60, the trumpet-shaped 54 of the quenching liquid jet channel 5, and the like, which were previously not possible to process, thereby extending the life of the direct current hardened coil 10. [Explanation of symbols]

[0042] 1 rack bar 2 racks 3 High frequency direct current hardening coil 4 Main unit 5 Quenching liquid jet channel 10 Direct current hardening coil 22 Quenching water supply port 25 Cavity 30 Cooling water supply port 31 Cooling water supply channel 32 Quenching liquid storage chamber 35 Pressure equalizer 37 holes 54 Trumpet shape 61 Top surface 62 Quenching liquid nozzle

Claims

1. A rack bar direct current hardening coil in which the surface of a rack bar to be hardened is directly heated by current and the surface is high-frequency induction heated by an induction coil arranged along the surface, The induction coil is made by a metal additive manufacturing method, has a cavity therein, and has a number of quenching liquid jet channels that pass through the cavity of the induction coil, The cavity serves as a cooling water flow channel for passing cooling water to cool the induction coil.

2. The high-frequency direct current hardening coil for a rack bar as described in claim 1, characterized in that the quenching liquid jet channel and the cooling water flow channel are both independent within the induction coil, and the part of the cavity excluding the quenching liquid jet channel becomes the cooling water flow channel.

3. 3. The high frequency direct current hardening coil for a rack bar according to claim 1, wherein the quenching liquid jet channel has a trumpet shape with a water inlet diameter larger than a water outlet diameter.

4. 4. The high frequency direct current hardened coil of rack bar according to claim 3, wherein the central part of the top surface of the induction coil is lowest and the coil becomes higher towards the ends.

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