Vehicle seat frame and vehicle seat

Abstract

To provide a vehicle seat frame which can ensure a necessary part strength of a frame while saving a weight of the frame.SOLUTION: A vehicle seat frame F comprises a frame member molded by use of a high-tensile steel plate. The frame member has: a non-heat treatment part in which heat treatment for strength adjustment is not performed; a high strength part in which heat treatment for strength improvement is performed, and which has a strength higher that the non-heat treatment part; and a low strength part in which heat treatment for strength degradation is performed, and which has a strengh lower than the non-heat treat ment part. The high strength part is a part which is heated to a prescribed temperature or higher, and thereafter, is cooled at a prescribed cooling velocity or more. The low strength part is a part which is heated to the prescribed temperature or higher, and thereafter, is cooled at a velocity lower than the prescribed cooling velocity.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a vehicle seat frame, and more particularly to a vehicle seat frame made of a thin, lightweight material. [Background technology]

[0002] Vehicle seat frames (hereinafter referred to as "seat frames"), which form the framework of vehicle seats, are required to be lightweight, but even when the weight is reduced, the strength of the seat frame must be maintained or improved.

[0003] Therefore, in the invention described in Patent Document 1, the frame members constituting the seat frame formed from general steel or the entire seat frame are subjected to heat treatment by induction hardening, liquid carburizing or gas carburizing to improve the strength of the seat frame formed from general steel.

[0004] In addition, in the invention described in Patent Document 2, a reinforcing portion is provided in the thin-walled steel, and a high-hardness portion is provided in the thin-walled steel by heat treatment. Furthermore, in the invention described in Patent Document 2, the shape of the force transmission path formed by the reinforcing portion and the high-hardness portion is made approximately truss-shaped, thereby improving the strength of the seat frame. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5657271 [Patent Document 2] Patent No. 5565785 Summary of the Invention [Problem to be solved by the invention]

[0006] To further reduce weight, high-tensile steel sheets are sometimes used as thin, lightweight materials for the frame materials that make up the seat frame, but high-tensile steel sheets are more difficult to form than regular steel. Even when using such high-tensile steel plates, if heat treatment is performed on frame members that require strength or on the entire seat frame, as in the invention described in Patent Document 1, distortion due to the heat treatment may become large, which may result in a decrease in product precision. Furthermore, when a reinforcing portion is provided in a thin-walled steel as in the invention described in Patent Document 2, the weight of the reinforcing portion increases, which is a problem in terms of weight reduction.

[0007] The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a vehicle seat frame that can reduce the weight of the frame while partially adjusting the strength of the frame. [Means for solving the problem]

[0008] The above problem is solved by a vehicle seat frame according to the present invention, which is provided with a frame member formed using a high-tensile steel plate, a seat back frame, a seat cushion frame, and a connecting bracket connecting the seat back frame and the seat cushion frame, the seat back frame being made up of an upper frame, a lower frame, and a side frame, the side frame having a plurality of through holes and a plurality of airbag mounting holes for mounting an airbag unit, the side frame and the lower frame being welded together at a weld; The frame member is divided into a non-heat-treated portion that is not subjected to heat treatment for strength adjustment, and a high-strength portion that is subjected to heat treatment for strength improvement and has a higher strength than the non-heat-treated portion. ,of Yes The high strength portion is provided above the welded portion. This is solved by The above problem is solved by the vehicle seat according to the present invention. To According to a vehicle seat comprising: a seat body having a seat cushion and a seat back; a reclining mechanism that rotatably connects the seat back to the seat cushion; a height link mechanism that connects the seat body to a vehicle floor so that the seat body can be raised and lowered; a rail mechanism that is attached to the vehicle floor and supports the seat body so that it can move forward and backward; and a vehicle seat frame that is a skeleton of the vehicle seat and has a frame member formed using a high-tensile steel plate, the vehicle seat frame having a seat back frame, a seat cushion frame, and a connecting bracket that connects the seat back frame and the seat cushion frame, and the seat cushion is mounted on the seat cushion frame that forms the skeleton. The seat back is constructed by covering a cushion pad placed on the seat back frame with a skin material, the seat back frame has an upper frame on an upper side, left and right side frames arranged to be connected to left and right ends of the upper frame, respectively, and a lower frame installed on lower ends of the left and right side frames, the side frames are provided with a plurality of through holes, the side frames and the lower frame are welded at welded parts, the frame members have non-heat-treated parts that are not subjected to heat treatment for strength adjustment, and high-strength parts that are heat-treated and have higher strength than the non-heat-treated parts, the high-strength parts are installed above the welded parts This is solved by

[0009] In the vehicle seat frame, the metal structure of a portion of the frame member formed using high-tensile steel plate is structured according to the conditions during heat treatment, so that the strength of that portion differs from the strength of the other portions. Therefore, in the vehicle seat frame, the strength of the same frame member can be partially changed without changing the shape or material. This makes it possible to partially adjust the strength of the frame member while achieving weight reduction by using a thin-walled, lightweight material for the frame member.

[0010] In the above vehicle seat frame, A reclining mechanism is provided to rotatably connect the seat back frame to the seat cushion frame, and the high strength portion is provided to avoid a mounting portion of the reclining mechanism. good 。

[0011] In the above vehicle seat frame, The high strength portion is provided so as to avoid the airbag mounting hole. It is acceptable to 。

[0012] In the above vehicle seat frame, The high-strength portion is provided between the airbag mounting hole and the mounting portion of the reclining mechanism. good 。

[0013] In the above vehicle seat frame, The high-strength portion is provided between the welded portion and the airbag mounting hole. It is acceptable to 。

[0014] In the vehicle seat frame described above, the frame member may include a low-strength portion that is formed by heat treatment for reducing strength and has a lower strength than a portion that is not subjected to heat treatment for reducing strength. According to the above configuration, it is possible to provide a portion of the frame member that constitutes the vehicle seat frame with reduced strength without changing the shape or material of the frame member, thereby facilitating deformation of the portion of the frame member that is heat-treated under predetermined conditions.

[0015] In the vehicle seat frame described above, the low-strength portion may be a portion that has been heated to a predetermined temperature or higher and then cooled at a rate slower than a predetermined cooling rate. According to the above configuration, the strength of a portion of the frame member that constitutes the vehicle seat frame, which is heated under predetermined conditions and then slowly cooled, can be made weaker than the remaining portion. In this way, by controlling the cooling rate in the heat treatment of the frame member, it is possible to provide the frame member with a portion that is partially weaker in strength.

[0016] In the vehicle seat frame, the metal structure of the low strength portion may include pearlite. Note that pearlite is a general term for a state in which ferrite and cementite coexist, and is, for example, a ferrite-based structure with cementite in a layered form. According to the above configuration, by partially providing the frame member with a portion containing pearlite, which has a metal structure with low hardness, it is possible to provide the frame member with a portion having low strength.

[0017] In the vehicle seat frame, the low-strength portion may be provided at least in a connection portion between a seat back frame and a seat cushion frame, a lower portion of a side frame constituting the seat back frame, or a rear portion of a cushion side frame constituting the seat cushion frame. The connection portion may be integral with the cushion side frame. According to the above configuration, the low strength portion functions as a weak portion, thereby enabling energy to be efficiently absorbed during a vehicle collision.

[0018] In the vehicle seat frame described above, the heat treatment may be performed with the frame members assembled. According to the above configuration, the magnitude of distortion caused by the heat treatment can be reduced compared to when the heat treatment is performed before assembly.

[0019] In the vehicle seat frame described above, the high-strength portion may be provided along a connection portion between a seat side surface and a seat rear surface in the side frame of the seat back frame. According to the above configuration, the strength of the seat back frame can be improved against forces acting on the rear of the seat.

[0020] In the above-mentioned vehicle seat frame, the side frames of the seatback frame may be formed with a plurality of holes for mounting an airbag, and the high-strength portion may be arranged to extend in the fore-and-aft direction of the seat between the plurality of holes. According to the above configuration, the strength of the side frames of the seatback frame can be improved against forces applied in the front-rear direction of the seat, thereby suppressing deformation of the side frames of the seatback frame.

[0021] In the above-mentioned vehicle seat frame, the high-strength portion may have a first region provided along the connection between the seat side surface and the seat rear surface in the side frame of the seatback frame, and a plurality of second regions provided between the plurality of holes so as to extend in the fore-and-aft direction of the seat. According to the above configuration, the strength of the side frames of the seat back frame can be improved over a wide range on the side surfaces of the seat.

[0022] In the above-mentioned vehicle seat frame, the welding marks may be at least one of welding marks between the upper frame of the seatback frame and the side frame of the seatback frame, or welding marks between the lower frame of the seatback frame and the side frame of the seatback frame. According to the above configuration, the strength of the side frames of the seatback frame can be improved over a wide range in the up-down direction of the seat.

[0023] In the vehicle seat frame described above, the high-strength portion may be provided in a portion where the upper frame of the seatback frame and the side frame of the seatback frame overlap each other. According to the above configuration, the strength of the joint between the upper frame and the side frame of the seat back frame can be improved. [Effects of the Invention]

[0024] According to the present invention, it is possible to reduce the weight of a vehicle seat frame while ensuring the strength of necessary portions of the vehicle seat frame. According to the present invention, deformation of a portion of a vehicle seat frame that has been heat treated under predetermined conditions can be suppressed. According to the present invention, by controlling the cooling rate during heat treatment of a portion of a vehicle seat frame, it is possible to provide a portion of the vehicle seat frame with high strength. According to the present invention, by partially providing the vehicle seat frame with a portion in which the metal structure is martensite, which has high hardness, the vehicle seat frame can be provided with a portion with high strength. According to the present invention, the rigidity of the welded areas of the upper frame and side frame of the seatback frame, which are prone to stress concentration during a vehicle collision, and the welded areas of the lower frame and side frame of the seatback frame are increased, thereby suppressing deformation of the vehicle seat frame. According to the present invention, it is possible to provide a frame member that constitutes a vehicle seat frame with a portion having a lower strength without changing the shape or material of the frame member. According to the present invention, by controlling the cooling rate during heat treatment of the frame member, it is possible to provide the frame member with a portion having a low strength. According to the present invention, by partially providing the frame member with a portion in which the metal structure contains pearlite, which has low hardness, it is possible to provide the frame member with a portion having low strength. According to the present invention, energy during a vehicle collision can be efficiently absorbed. According to the present invention, the magnitude of distortion caused by heat treatment can be reduced compared to when heat treatment is performed before assembly. According to the present invention, the strength of the seatback frame can be improved against forces acting on the rear of the seat. According to the present invention, the strength of the side frames of the seatback frame can be improved against forces applied in the front-rear direction of the seat. According to the present invention, the strength of the side frames of the seat back frame can be improved over a wide range on the side surfaces of the seat. According to the present invention, the strength of the side frames of the seatback frame can be improved over a wide range in the up-down direction of the seat. According to the present invention, the strength of the joint between the upper frame and the side frame of the seat back frame can be improved. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a perspective view of a vehicle seat according to an embodiment of the present invention; [Figure 2] FIG. 2 is a perspective view of a seat frame that serves as a framework of the vehicle seat. [Figure 3] FIG. 2 is a diagram illustrating the relationship between heat treatment conditions and metal structure. [Figure 4] 3 is an enlarged view of a main part of FIG. 2, showing an example of a heat treatment location in the joint between the upper frame and the side frame. FIG. [Figure 5] 3 is an enlarged view of a main part of FIG. 2, showing another example of a heat treatment location in the joint between the upper frame and the side frame. FIG. [Figure 6] 6 is a cross-sectional view taken along the line VI-VI in FIG. 5, showing a heat treatment location in the joint between the upper frame and the side frame. [Figure 7] 3 is an enlarged view of a main part of FIG. 2, showing an example of a heat treatment location in the joint between the side frame and the lower frame. FIG. [Figure 8] 10A and 10B are diagrams showing an example of heat-treated locations on a connecting bracket. [Figure 9] 10A and 10B are diagrams illustrating examples of heat treatment locations on a seat back frame and a cushion frame. [Figure 10] FIG. 2 is a perspective view of a seat back frame of a rear seat. [Figure 11] 10 is an enlarged view of a main part of FIG. 9, showing a perspective view of a heat treatment location in a joint portion of a frame skeleton part. FIG. [Figure 12] FIG. 10 is a perspective view of a vehicle seat frame according to a modified example of the present invention. [Figure 13] 10A and 10B are diagrams illustrating heat treatment locations of a vehicle seat frame according to a modified example. [Figure 14] 14 is a view taken along an arrow XIV in FIG. 12. [Figure 15] 13 is a view taken along an arrow XV in FIG. 12. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, a vehicle seat and a seat frame that forms the framework of the vehicle seat according to an embodiment of the present invention will be described with reference to FIGS.

[0027] This embodiment relates to a vehicle seat frame including frame members formed using high-tensile steel plate, in which the metal structure of a portion of the frame member is structured according to the conditions at the time of heat treatment, and the strength of the portion is different from the strength of the other portions. Note that, hereinafter, the side of the seat back of the vehicle seat on which an occupant sits is referred to as the front side of the seat, and the opposite side is referred to as the rear side of the seat.

[0028] As shown in Figures 1 and 2, the vehicle seat S of this embodiment is mainly composed of a seat body having a seat cushion 1 and a seat back 2, a reclining mechanism 20 that rotatably connects the seat back 2 to the seat cushion 1, a height link mechanism 21 that connects the seat body to the vehicle floor so that it can be raised and lowered, and a rail mechanism 40 that is attached to the vehicle floor and supports the seat body so that it can move back and forth.

[0029] The seat cushion 1 is a seating portion that supports an occupant from below. As shown in Figures 1 and 2, the seat cushion 1 is configured by placing a cushion pad 1a on a cushion frame 10 that serves as a skeleton, and covering the cushion pad 1a with a cover material 1b.

[0030] The seat back 2 is a backrest portion that supports the back of the occupant from behind. The seat back 2 is configured by covering a cushion pad 2a placed on a seat back frame 30 that serves as a skeleton with a skin material 2b.

[0031] The vehicle seat frame F is the skeleton of the vehicle seat S. As shown in FIG. 2 , the vehicle seat frame F includes a cushion frame 10, a seat back frame 30, and a connecting bracket 50 that connects the cushion frame 10 and the seat back frame 30.

[0032] As shown in FIG. 2, the cushion frame 10 is a substantially rectangular frame-like body that serves as the framework of the seat cushion 1. The cushion frame 10 includes cushion side frames 11 arranged on the left and right sides, a plate-like pan frame 12 connecting the front portions of each cushion side frame 11, and a pipe-like rear connecting frame 13 connecting the rear portions of each cushion side frame 11. The cushion frame 10 also includes three elastic springs 14 that are hooked to the pan frame 12 and the rear connecting frame 13 and extend in a snake-like shape, and a submarine pipe that is arranged below the pan frame 12 and connects each cushion side frame 11.

[0033] The cushion side frame 11 is a sheet metal member that extends in the front-rear direction of the seat and has a generally U-shaped vertical cross section. A reclining mechanism 20 is attached to the rear portion of the cushion side frame 11, and a rail mechanism 40 is attached to its lower portion via a height link mechanism 21.

[0034] The reclining mechanism 20 can be switched between a locked state, in which the rotational movement of the seat back 2 is locked, and an unlocked state. When the seat back 2 is locked in an upright position, the reclining mechanism 20 is unlocked by operating the reclining operation lever, and the upright position of the seat back 2 can be adjusted.

[0035] The height link mechanism 21 has the function of adjusting the height of the seat body. The height link mechanism 21 has two links attached to the front and rear sides of the seat between the cushion frame 10 and the rail mechanism 40, and the height adjustment mechanism is realized by the operation of these links. Note that two links are provided for each of the left and right cushion side frames 11.

[0036] The rail mechanism 40 is mainly composed of left and right lower rails 41 that are fixed to the vehicle floor and extend in the fore-and-aft direction of the seat, left and right upper rails 42 that are supported slidably along the lower rails 41, a locking member that locks the upper rails 42 so that they cannot slide, and a rail operating lever that releases the locked state of the locking member.

[0037] The lower rails 41 are long hollow bodies and are arranged on the left and right sides with a gap in the seat width direction. The lower rails 41 are formed with a storage space that has a generally convex cross section along the seat front-rear direction.

[0038] The upper rail 42 is formed of a long body that is inserted into the accommodation space of the lower rail 41 and slides along the lower rail 41. As shown in FIG. 2, a link that connects to the cushion frame 10 via a rail connecting bracket 45 is connected to the upper portion of the upper rail 42.

[0039] Next, the configuration of the seat back frame 30 will be described in detail. As shown in Figure 2, the seatback frame 30 comprises an upper frame 31 which is a hollow cylinder formed in an approximately inverted U shape on the upper side, left and right side frames 32 which are arranged and connected to the left and right ends of the upper frame 31, respectively, and a lower frame 33 which is installed on the lower ends of the left and right side frames 32. The seat back frame 30 also includes elastic springs 34 mounted on the inner surfaces of the left and right side frames 32 , and an upper cross frame 36 mounted on the inner surface of the curved portion of the upper frame 31 .

[0040] The left and right side frames 32 are formed by bending a metal plate member inward laterally to form a generally U-shape. The left and right side frames 32 extend in the vertical direction and are spaced apart in the horizontal direction while being generally parallel to each other. The side frame 32 is formed with airbag mounting holes 82a, 82b, and through-holes 82c, which are holes for mounting an airbag unit. The airbag unit includes an airbag body, a webbing that guides the airbag in the deployment direction, an airbag mounting plate, etc. For example, the airbag mounting holes 82a and 82b are locations where the webbing of the airbag is mounted, and the through-holes 82c are locations where bolts extending from the airbag module are inserted. A bead portion is formed around the through hole 82c. In particular, a substantially U-shaped bead portion 83 is formed between the airbag mounting holes 82a and 82b in front of the seat from the through hole 82c.

[0041] The right side frame 32 is positioned so that the inner side surface of the upper end portion thereof abuts against the right end portion of the upper frame 31. Then, the upper end portion of the right side frame 32 and the right end portion of the upper frame 31 are fixed by welding. Similarly, the left side frame 32 is disposed so that the inner side surface of the upper end portion thereof abuts against the left end portion of the upper frame 31. Then, the upper end portion of the left side frame 32 and the left end portion of the upper frame 31 are fixed by welding. The welding may be performed by various welding methods such as laser welding or arc welding.

[0042] As shown in FIG. 2, the lower frame 33 has a central portion of the frame extending in the left-right direction, and end portions formed by bending the portions extending left and right from the central portion of the frame so as to face each other.

[0043] The inner surface of the right end portion of the lower frame 33 is disposed so as to abut against the right side frame 32. The lower end portion of the right side frame 32 and the right end portion of the lower frame 33 are fixed by welding. Similarly, the inner surface of the left end portion of the lower frame 33 is disposed so as to abut against the left side frame 32. The lower end portion of the left side frame 32 and the left end portion of the lower frame 33 are fixed by welding.

[0044] A shaft through-hole that penetrates in the left-right direction is provided at the end of the side frame 32. A connecting shaft 35 is fitted through the reclining mechanism 20, the connecting bracket 50 that connects the reclining mechanism 20 and the cushion frame 10, and the lower end of the left and right side frames 32, respectively, to secure each part. The connecting shaft 35 serves as a rotation axis when the seat back frame 30 is rotated by the reclining mechanism 20 .

[0045] In the seat frame according to this embodiment, frame components formed primarily using high-tensile steel plates (e.g., 440 MPa material) are assembled by welding or the like, and then heat treatment is performed to adjust the hardness of portions of the seat frame where strength is to be adjusted. In this embodiment, the heat treatment is performed by heating with a laser and cooling the heated portion, but the present invention is not limited to this. The frame members mentioned above are elements that make up the seat frame. For example, the components that make up the seatback frame 30, the components that make up the cushion frame 10, and the brackets that connect the seatback frame 30 and the cushion frame 10 are examples of the frame members mentioned above.

[0046] Specifically, heat treatment (strength-enhancing heat treatment) is performed on the periphery of the welded portion between the upper frame 31 and the side frame 32 and the periphery of the welded portion between the side frame 32 and the lower frame 33 to increase strength. The strength-enhancing heat treatment is performed by controlling the cooling rate in the heating treatment and the subsequent cooling treatment. The areas where the metal structure has changed as a result of the strength-enhancing heat treatment are referred to as high-strength areas.

[0047] Furthermore, in the seat frame according to this embodiment, heat treatment (strength-reducing heat treatment) is performed to reduce the strength of parts of the connecting bracket 50 that connects the cushion frame 10 and the seatback frame 30, the areas around the lower ends of the left and right side frames 32 that constitute the seatback frame 30, and the areas around the rear ends of the cushion side frames 11 that constitute the cushion frame 10. The strength-reducing heat treatment is performed by controlling the cooling rate in the heating treatment and the subsequent cooling treatment. The areas where the metal structure has changed as a result of the strength-reducing heat treatment are referred to as low-strength parts. The relationship between the heat treatment conditions and the change in the structure of the steel will be explained below.

[0048] Figure 3 shows the classification of metal structures that change from austenite depending on the cooling rate after steel is heated to above the A1 transformation point (heated to 1000°C in the example shown in Figure 3) to create an austenite structure (S2).

[0049] As shown in Figure 3, when austenitic steel at 1000°C is cooled at a cooling rate (critical cooling rate) that reduces the temperature to 540°C or less within 2 seconds (for example, cooling curve C1), the austenitic structure transitions to a martensite structure (S1).

[0050] Furthermore, as shown in Figure 3, when austenitic steel at 1000°C is cooled at a rate slower than 540°C within 2 seconds (for example, cooling curve C2 or C3), the metal structure transitions to include a pearlite structure (S3, S4). In this case, when the cooling curve is C2, a martensite structure and a pearlite structure are mixed (S3), but when the cooling rate is slower and cooling is performed using cooling curve C3, a pearlite structure is obtained (S4).

[0051] The hardness of the metal structure is martensite (S1) > martensite + pearlite (S3) > pearlite (S4).

[0052] Furthermore, methods for cooling steel that has been heated until it changes to an austenite structure may include spraying dry ice powder onto the heat treatment area, spraying cooled air onto the heat treatment area, spraying dry mist onto the heat treatment area, etc. Among these, cooling with dry mist is preferred in order to achieve a cooling rate equal to or higher than the critical cooling rate. For example, in the cooling process using dry mist, low-temperature dry mist made by adding a small amount of moisture to cooling air may be used. In this case, it is preferable that the particle size of the mist is about 30 μm. By using the above-mentioned low-temperature dry mist in the rapid cooling process of quenching, it is possible to reduce the amount of water used for cooling while still achieving effective cooling. This allows quenching to be performed around components such as electronic devices that are at risk of damage due to water. Furthermore, since the amount of water used for cooling can be reduced and there is no need to employ a large-scale waterproofing mechanism, the cost of the quenching process can be reduced.

[0053] In this embodiment, when the strength is increased by heat treatment, the cooling rate is controlled so that the metal structure of the heat-treated area becomes martensite, whereas when the strength is decreased by heat treatment, the cooling rate is controlled so that the metal structure of the heat-treated area contains pearlite.

[0054] Next, specific heat treatment locations in the vehicle seat frame F according to this embodiment will be described with reference to Figures 4 to 7. First, specific examples of locations where high-strength portions are formed by applying heat treatment to a part of the vehicle seat frame F to increase its strength will be described.

[0055] 4 is an enlarged view of a main portion of FIG. 2, and is a perspective view showing an example of a high-strength portion formed at the joint between the upper frame 31 and the side frame 32. In FIG. 4, the upper frame 31 and the upper cross frame 36 are welded (arc welded) at welded portion 60a. The upper frame 31 and the side frame 32 are welded (laser welded) at welded portions 60b and 60c. Note that the welding method is an example and is not limited to the welding method shown in the present embodiment.

[0056] 4 is provided in an area including at least a portion of the welded portions 60a, 60b, and 60c of the upper frame 31 and the side frame 32. The high-strength portion 61 may be provided over the entire circumference of the cross section of the upper frame 31 and the side frame 32, or may be provided in a portion of the cross section.

[0057] The high-strength portion 61 is subjected to the following heat treatment for strength enhancement. Specifically, in the heat treatment for strength enhancement, steel is heated to 1000°C to form an austenite structure, and then rapidly cooled to 540°C or below within two seconds to transform it into a martensite structure. This makes the high-strength portion 61 that has been subjected to the heat treatment for strength enhancement higher in hardness than a portion that has not been subjected to the heat treatment for strength enhancement. This makes it possible to locally improve the strength of the joint between the upper frame 31 and the side frame 32.

[0058] Next, another example of the high-strength portion formed at the joint between the upper frame 31 and the side frame 32 will be described with reference to Figures 5 and 6. Figure 5 is an enlarged view of the main part of Figure 2, and is a perspective view showing another example of the high-strength portion formed at the joint between the upper frame 31 and the side frame 32. Figure 6 is a cross-sectional view taken along line VI-VI of Figure 5, and is a cross-sectional view of the high-strength portion formed at the joint between the upper frame 31 and the side frame 32.

[0059] 5 and 6, the high-strength portion 61a has a narrower range than the high-strength portion 61 shown in Fig. 4. In other words, the high-strength portion 61a is provided in an area that includes the welded portion between the upper frame 31 and the side frame 32, but does not include the welded portion between the upper cross frame 36 and the upper frame 31. Also, as shown in Fig. 6, the high-strength portion 61a may be provided on the front side of the seat in the cross section between the upper frame 31 and the side frame 32, and may not be provided on the rear side of the seat.

[0060] The high-strength portion 61a is also heat-treated to improve its strength so that its metal structure becomes martensite. As a result, in the example shown in Figures 5 and 6, it is possible to locally improve the strength of the area around the joint between the upper frame 31 and the side frame 32 on the front side of the seat, where stress is concentrated during a vehicle collision.

[0061] Next, as shown in Fig. 7, the high-strength portion may be provided, for example, at the joint between the side frame 32 and the lower frame 33. Fig. 7 is an enlarged view of the main part of Fig. 2, and is a perspective view showing an example of the high-strength portion formed at the joint between the side frame 32 and the lower frame 33. In Fig. 7, the side frame 32 and the lower frame 33 are welded (laser welded) at weld 70.

[0062] The high-strength portion 71 shown in Fig. 7 is provided in an area including the welded portion 70 between the side frame 32 and the lower frame 33. Here, the high-strength portion 71 is subjected to a strength-enhancing heat treatment in which steel that has been heated to 1000°C to become an austenitic structure is rapidly cooled to 540°C or less within two seconds to change it to a martensite structure. This makes the hardness of the high-strength portion 71 higher than that of a portion that has not been subjected to the strength-enhancing heat treatment, thereby improving the strength of the joint between the side frame 32 and the lower frame 33.

[0063] Next, with reference to FIGS. 8 and 9, specific examples of low-strength portions of the frame members that make up the vehicle seat frame F that are formed by heat treatment to reduce the strength will be described.

[0064] 8, a low-strength portion 54 is provided in a portion of the connecting bracket 50 that connects the cushion frame 10 and the seatback frame 30. The connecting bracket 50 is formed with bolt fastening holes 52 and 53 through which bolts that fasten the cushion side frame 11 and the connecting bracket 50 are inserted, and a shaft through-hole 51 for the connecting shaft 35. The reclining mechanism 20 is attached to the connecting shaft 35, and the seatback frame 30 is connected to the connecting bracket 50 via the reclining mechanism 20.

[0065] 8, a low-strength portion having a lower strength than the surrounding area is provided between the portion to which the cushion frame 10 is connected and the portion to which the seatback frame 30 is connected. That is, in the connecting bracket 50 shown in FIG. 8, a low-strength portion 54 having a metal structure that is lower in hardness than the surrounding area, for example, a pearlite structure, is formed between the shaft through-hole 51 and the bolt fastening hole 53 by heat treatment.

[0066] The low-strength portion 54 is subjected to the following heat treatment for reducing strength. That is, in the heat treatment for reducing strength, steel that has been heated to 1000°C by a laser to form an austenite structure is slowly cooled at a cooling rate slower than the critical cooling rate, for example, by natural cooling (self-cooling), to change it to a pearlite structure. When using a high-tensile steel plate of 780 material (tensile strength of 780 MPa) or higher, the strength of the connecting bracket 50 can be partially reduced by the heat treatment for strength reduction described above, which reduces the hardness of the low-strength portion 54 compared to the metal structure of the portion that has been heat-treated for strength improvement and the other portion that has not been heat-treated. In the event of a vehicle collision, the low-strength portion 54, which becomes a weak portion, deforms, thereby reducing stress concentration on the seat back frame 30. In other words, the low-strength portion 54 functions as a weak portion, allowing the impact of a vehicle collision to be efficiently absorbed.

[0067] 9, low-strength portions 72 may be provided around the lower ends of the side frames 32 that constitute the seatback frame 30. Here, the lower ends of the side frames 32 refer to the ends of the side frames 32 that are closer to the joints with the lower frame 33. The low-strength portions 72 are also formed by the same heat treatment for reducing strength as described above. In this way, by providing the low-strength portions 72 around the lower ends of the side frames 32 and causing the low-strength portions 54 to deform as weak portions during a vehicle collision, it is possible to efficiently absorb the impact during a vehicle collision.

[0068] As shown in FIG. 9, a low-strength portion 73 may be provided around the rear end of the cushion side frame 11 constituting the cushion frame 10. Here, the rear end of the cushion side frame 11 refers to the end of the cushion side frame 11 on the seat rear side. The low-strength portion 73 is also formed by performing the same heat treatment for reducing strength as described above. In this way, by providing the low-strength portion 73 around the lower end of the side frame 32 and causing the low-strength portion 73 to deform as a weak portion during a vehicle collision, the impact during a vehicle collision can be efficiently absorbed. Note that if any one of the above-described low-strength portions 54, 72, and 73 is formed, the other low-strength portions do not need to be formed.

[0069] In the vehicle seat frame according to the above embodiment, the heat-treated portion is heated with a laser to a predetermined temperature (above the A1 transformation point, for example, 1000°C) to form an austenitic structure, and the subsequent cooling rate is controlled to cause the heat-treated portion to transition to a metal structure with a different strength. This makes it possible to differentiate the strength of the heat-treated portion of the vehicle seat frame from other portions without changing the shape, material, etc. of the vehicle seat frame. Furthermore, in the vehicle seat frame according to the above embodiment, when the frame members constituting the vehicle seat frame are assembled by welding or the like, the strength of the target portion for which strength is to be adjusted (i.e., the strength adjustment portion in the frame complete product) can be adjusted by controlling the cooling rate after heat treatment.

[0070] Furthermore, in the vehicle seat frame according to the above embodiment, a target portion of the vehicle seat frame is heated to 1000°C or higher by a laser, and then cooled at a predetermined cooling rate or higher (e.g., 230°C per second or higher) to transition the heat-treated portion from an austenite structure to a martensite structure, for example. This makes it possible to increase the strength of the target portion without changing the shape, thickness, adding reinforcing members, changing materials, etc. In this way, a seat frame formed using high-tensile steel plate can partially achieve strength equivalent to that of ultra-high-tensile steel plate (980 MPa or higher).

[0071] Furthermore, in the vehicle seat frame according to the above embodiment, after heating with a laser, cooling is performed at a rate less than a predetermined cooling rate (for example, natural cooling). By transitioning the heat-treated area from an austenite structure to a pearlite structure, for example, it is possible to reduce the strength of necessary areas without changing the shape, thickness, processing such as unevenness or notches, or changing materials.

[0072] Furthermore, the process of forming high-strength and low-strength portions in the seat frame by heat treatment can be carried out even after the frame members are assembled, allowing for a high degree of flexibility in the manufacturing process. Furthermore, when the frame members that make up the seat frame are welded using a laser, the heat treatment areas can be heated using laser welding equipment, jigs, and manufacturing lines, which reduces manufacturing costs and facilitates mass production.

[0073] Furthermore, in the vehicle seat frame according to the above embodiment, it is easy to ensure flat surfaces for mounting parts, and since there are no protruding surfaces or notches, the shape can be made compact.

[0074] Furthermore, there are no particular restrictions on the parts whose strength is adjusted by the heat treatment according to the present invention, and they may be either pipes or pressed products.

[0075] Furthermore, in the vehicle seat frame according to this embodiment, the oxide coating left after laser heating remains as a trace of processing, and even if the oxide coating is painted over to remove the traces, they can still be confirmed using an electron microscope or a handheld electrical current meter.

[0076] <Other embodiments> The vehicle seat frame according to the present invention can be applied not only to front seats but also to rear seats in the same manner.

[0077] Here, Fig. 10 shows a perspective view of a rear back frame 100 for the rear seat. Fig. 11 shows an enlarged view of the main part of Fig. 10, showing the heat treatment points in the joints of the frame skeleton parts.

[0078] As shown in Figure 10, the rear back frame 100 comprises a square bar-shaped skeletal frame (e.g., skeletal frames 101, 102, 103) that forms the skeleton of the rear back frame 100, and a plate-shaped pan frame (e.g., rear pan frame 105) that forms the surface of the rear back frame 100. A skeletal frame (for example, skeletal frame 101) that serves as the horizontal skeleton of the seat back frame and a skeletal frame (for example, skeletal frames 102, 103) that serves as the vertical skeleton of the seat back frame are welded together. In the example shown in FIG. 10, the frame is laser welded, but the frame may be joined by other welding methods such as arc welding.

[0079] FIG. 11 shows an enlarged view of the joint XI between the skeletal frame 101 and the skeletal frame 103 of the rear back frame 100 shown in FIG. 11, the flange portions 103a of the skeletal frames 101 and 103 are welded at weld portions 110a. The flange portions 103b of the skeletal frames 101 and 103 are welded at weld portions 110b. The skeletal frames 101 and 103 are welded to the recessed portions 103c of the skeletal frames 103 at weld portions 110c.

[0080] 11, in the rear back frame 100 according to one embodiment of the present invention, a heat treatment for improving strength is performed on the high-strength portion 120 at the ridge line portion of the skeleton frame 103 constituting the rear back frame 100. For example, in the heat treatment for improving strength, steel that has been heated to 1000°C to form an austenite structure is rapidly cooled to 540°C or lower within two seconds to change it to a martensite structure. This makes the high-strength portion 120 harder than the metal structure of the portion that has been subjected to heat treatment for reducing strength or the other portion that has not been subjected to heat treatment, thereby improving the strength of the skeleton frame 103. Furthermore, the strength of the skeleton frames other than the skeleton frame 103 and the pan frame may also be partially adjusted by heat treatment for increasing strength or heat treatment for decreasing strength.

[0081] In the above embodiment, as shown in Fig. 2, the vehicle seat S is configured to include the height link mechanism 21 and the rail mechanism 40, but these components are not essential. For example, the base member fixed to the vehicle floor and the cushion frame 10 (cushion side frame 11) may be directly connected. Also, the connecting bracket 50 may be formed integrally with the cushion side frame 11 to reduce the number of parts.

[0082] [Modification of seat back frame] Next, a vehicle seat frame F1 according to a modified example of the present invention will be described with reference to Figures 12 to 15. The vehicle seat frame F1 differs from the vehicle seat frame F mainly in the configuration of the side frames 32 and the locations to be heat treated. Below, the vehicle seat frame F1 will be described mainly in terms of the differences from the vehicle seat frame F.

[0083] As shown in FIGS. 12 and 13, the side frames 32 of the vehicle seat frame F1 are joined to the upper frame 31 at welded portions 80 and 81. As shown in FIG. The welded portions 80 are substantially U-shaped welded portions provided at two locations on the upper end portions of the side frames 32. The welded portions 80 join the upper end portions of the side frames 32 and the upper frame 31 together. Additionally, welded portion 81 is a linear welded portion provided below welded portion 80. Welded portion 81 joins the lower end of upper frame 31 and side frame 32 together.

[0084] As shown in FIG. 15, the side frames 32 of the vehicle seat frame F1 are joined to the lower frame 33 at welded portions 85a, 85b, 85c, and 85d. In the vehicle seat frame F1, the upper frame 31, the side frames 32, and the lower frame 33 are welded together by laser welding, but other welding methods such as arc welding may also be used.

[0085] Furthermore, in the vehicle seat frame F1, like the vehicle seat frame F, the side frames 32 are formed with airbag mounting holes 82a, 82b, and through-holes 82c, which are holes for mounting an airbag unit. The airbag unit includes an airbag body, a webbing that guides the airbag in the deployment direction, an airbag mounting plate, etc. For example, the airbag mounting holes 82a and 82b are locations where the webbing of the airbag is mounted, and the through-hole 82c is a location where a bolt extending from the airbag module is inserted.

[0086] Next, with reference to FIGS. 13 to 15, the heat treatment portions of the vehicle seat frame F1 will be described.

[0087] As shown in Figures 13 to 15, in the vehicle seat frame F1, high-strength portions 84d and 84e (corresponding to the first region) are formed by hardening to improve strength along the connection portion 32c, which is the ridge portion connecting the seat side surface 32a and the seat rear surface 32b in the side frame 32. Here, the high-strength portion 84d is formed in an upper portion of the connecting portion 32c, at a position facing the welded portion 81. For example, the high-strength portion 84d is formed above the airbag mounting hole 82a. Further, the high-strength portion 84e is formed in a position below the connecting portion 32c, at which the high-strength portion 84e at least partially overlaps the welded portion 85a. For example, the high-strength portion 84e is formed below the airbag mounting hole 82b. In this way, by forming the high-strength portions 84d and 84e in the side frames 32, the strength of the side frames 32 can be improved against forces acting on the rear of the seat. In the vehicle seat frame F1, the high-strength portion 84d and the high-strength portion 84e are formed to be spaced apart from each other, but they may be joined together to form one body.

[0088] In addition, in the vehicle seat frame F1, a high-strength portion 84a (corresponding to the second region) is formed by hardening the region extending from near the high-strength portion 84c to the front of the seat between the airbag mounting hole 82b and the through-hole 82c to improve strength. In addition, in the vehicle seat frame F1, an airbag mounting hole 82b (corresponding to the second region) is formed by hardening the region extending from near the high-strength portion 84c to the front of the seat between the airbag mounting hole 82a and the through-hole 82c to improve strength. In this way, by forming the high-strength portions 84a and 84b in the side frames 32, the strength of the side frames 32 can be improved against forces applied in the front-rear direction of the seat, thereby suppressing deformation of the side frames 32.

[0089] Furthermore, a high-strength portion 84c is formed by performing quenching for improving strength on a region (third region) connecting the sheet front ends of the high-strength portion 84a and the high-strength portion 84b. In this way, by hardening in different directions, the strength can be improved in a well-balanced manner over a wide range of the seat side surface 32a of the side frame 32. In the vehicle seat frame F, the rigidity around the through hole 82c is increased by providing a bead portion 83 in front of the through hole 82c. On the other hand, in the vehicle seat frame F1, the rigidity around the through hole 82c can be increased in the same way as the bead portion 83 by providing a substantially U-shaped hardened portion made up of high-strength portion 84a, high-strength portion 84b, and high-strength portion 84c in front of the through hole 82c.

[0090] In the vehicle seat frame F1, the seat side surface 32a of the side frame 32 is reinforced with high-strength portions 84a, 84b, 84c, 84d, and 84e, thereby improving the strength of a wide range of the seat side surface 32a.

[0091] 13 to 15, high-strength portion 84a and high-strength portion 84b are formed at positions spaced apart from high-strength portion 84d and high-strength portion 84e. However, high-strength portion 84a and high-strength portion 84d, and high-strength portion 84b and high-strength portion 84e may be connected.

[0092] In the vehicle seat frame F1, the high-strength portion 84d is formed along (substantially parallel to) the welded portion 81, and the high-strength portion 84e is formed overlapping the welded portion 85a extending in the seat up-down direction. In this way, by forming the high-strength portions 84d and 84e along the connecting portion 32c, the strength of the side frame 32 can be improved over a wide range from the top to the bottom.

[0093] Furthermore, in the vehicle seat frame F1, the high-strength portion 84d is provided in the portion where the side frame 32 and the upper frame 31 overlap. This makes it possible to improve the strength of the joint portion between the upper frame 31 and the side frame 32.

[0094] In the above embodiment, a vehicle seat used in an automobile was described as a specific example, but the present invention is not limited to this and may also be applied to vehicle seats for trains, buses, etc., as well as seats for vehicles such as airplanes and ships.

[0095] In the above embodiment, the high-tensile steel plate may be a steel plate having a tensile strength of, for example, 340 MPa or more, but the definition of the high-tensile steel plate is not limited to the above.

[0096] In this embodiment, the vehicle seat frame according to the present invention has been mainly described. However, the above embodiment is merely an example for facilitating understanding of the present invention and is not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit thereof, and of course, the present invention also includes equivalents thereof. [Explanation of symbols]

[0097] 1 seat cushion 1a, 2a cushion pad 1b,2b Skin material 2 seat backs 10 Cushion Frame 11 Cushion side frame 12 Pan Frame 13 Rear connecting frame 14,34 Elastic spring 20 Reclining mechanism 21 Height link mechanism 30 Seat back frame 31 Upper frame 32 Side frame 32a Seat side 32b Rear of seat 32c connection 33 Lower frame 35 Connecting shaft 36 Upper cross frame 40 Rail mechanism 41 Lower rail 42 Upper Rail 45 Rail connection bracket 50 Connecting bracket 51 Shaft through hole 52,53 Bolt fastening holes 61,61a,71,120 High strength part 54,72,73 Low strength part 60a, 60b, 60c, 70, 110a, 110b, 110c welded parts 80 Welded Section 81 Welded parts 82a Airbag mounting hole 82b Airbag mounting hole 82c through hole 83 Bead section 84a High strength part (2nd area) 84b High strength part (2nd area) 84c High strength part (3rd area) 84d High strength part (1st area) 84e High strength part (1st area) 85a Welded section 85b Welded section 85c weld 85d weld 100 rear back frame 101, 102, 103 Skeletal frame 103a, 103b flange part 103c Recess 105 rear pan frame C1,C2,C3 cooling curve Front vehicle seat frame F1 car seat frame S vehicle seat

Claims

1. A vehicle seat frame including a frame member formed using a high-tensile steel plate, the vehicle seat frame comprising: a seat back frame; Seat cushion frame, a connecting bracket that connects the seat back frame and the seat cushion frame, The seat back frame is made up of an upper frame, a lower frame, and a side frame, The side frame is formed with a plurality of through holes and a plurality of airbag mounting holes for mounting an airbag unit, The side frame and the lower frame are welded to each other at welded joints, The frame member is a non-heat-treated portion that is not subjected to heat treatment for strength adjustment; a high-strength portion that has been subjected to heat treatment for improving strength and has a strength higher than that of the non-heat-treated portion; The vehicle seat frame is characterized in that the high-strength portion is provided above the welded portion.

2. A reclining mechanism is provided that rotatably connects the seat back frame to the seat cushion frame, 2. The vehicle seat frame according to claim 1, wherein the high-strength portion is provided so as to avoid a mounting portion of the reclining mechanism.

3. A vehicle seat frame as described in Claim 1, characterized in that the high-strength portion is arranged to avoid the airbag mounting hole.

4. A vehicle seat frame as described in Claim 2, characterized in that the high-strength portion is provided between the airbag mounting hole and the mounting portion of the reclining mechanism.

5. A vehicle seat frame as described in claim 1, characterized in that the high-strength portion is provided between the welded portion and the airbag mounting hole.

6. 6. The vehicle seat frame according to claim 1, wherein the high-strength portion is provided along a connecting portion between a seat side surface and a seat rear surface in the side frame of the seat back frame.

7. A vehicle seat, a seat body including a seat cushion and a seat back; a reclining mechanism that rotatably connects the seat back to the seat cushion; a height link mechanism that connects the seat body to the vehicle floor so that the seat body can be raised and lowered; a rail mechanism attached to a vehicle floor and supporting the seat body so that the seat body can move back and forth; a vehicle seat frame that is a skeleton of the vehicle seat and has a frame member formed using a high-tensile steel plate, the vehicle seat frame includes a seat back frame, a seat cushion frame, and a connecting bracket that connects the seat back frame and the seat cushion frame, The seat cushion is configured by covering a cushion pad placed on the seat cushion frame, which serves as a skeleton, with a skin material, The seat back is configured by covering a cushion pad placed on the seat back frame with a skin material, the seat back frame has an upper frame on an upper side, left and right side frames disposed so as to be connected to left and right end portions of the upper frame, respectively, and a lower frame disposed between lower end portions of the left and right side frames, The side frame is provided with a plurality of through holes, The side frame and the lower frame are welded to each other at welded joints, The frame member is a non-heat-treated portion that is not subjected to heat treatment for strength adjustment; a high-strength portion that has been heat-treated and has a strength higher than that of the non-heat-treated portion, The vehicle seat, wherein the high-strength portion is provided above the welded portion.

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