Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60N—SEATS SPECIALLY ADAPTED FOR VEHICLES; VEHICLE PASSENGER ACCOMMODATION NOT OTHERWISE PROVIDED FOR
  • B60N2/00—Seats specially adapted for vehicles; Arrangement or mounting of seats in vehicles
  • B60N2/02—Seats specially adapted for vehicles; Arrangement or mounting of seats in vehicles the seat or part thereof being movable, e.g. adjustable
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60N—SEATS SPECIALLY ADAPTED FOR VEHICLES; VEHICLE PASSENGER ACCOMMODATION NOT OTHERWISE PROVIDED FOR
  • B60N2/00—Seats specially adapted for vehicles; Arrangement or mounting of seats in vehicles
  • B60N2/02—Seats specially adapted for vehicles; Arrangement or mounting of seats in vehicles the seat or part thereof being movable, e.g. adjustable
  • B60N2/22—Seats specially adapted for vehicles; Arrangement or mounting of seats in vehicles the seat or part thereof being movable, e.g. adjustable the back-rest being adjustable
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60N—SEATS SPECIALLY ADAPTED FOR VEHICLES; VEHICLE PASSENGER ACCOMMODATION NOT OTHERWISE PROVIDED FOR
  • B60N2/00—Seats specially adapted for vehicles; Arrangement or mounting of seats in vehicles
  • B60N2/24—Seats specially adapted for vehicles; Arrangement or mounting of seats in vehicles for particular purposes or particular vehicles
  • B60N2/42—Seats specially adapted for vehicles; Arrangement or mounting of seats in vehicles for particular purposes or particular vehicles the seat constructed to protect the occupant from the effect of abnormal g-forces, e.g. crash or safety seats
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60N—SEATS SPECIALLY ADAPTED FOR VEHICLES; VEHICLE PASSENGER ACCOMMODATION NOT OTHERWISE PROVIDED FOR
  • B60N2/00—Seats specially adapted for vehicles; Arrangement or mounting of seats in vehicles
  • B60N2/64—Back-rests or cushions
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60N—SEATS SPECIALLY ADAPTED FOR VEHICLES; VEHICLE PASSENGER ACCOMMODATION NOT OTHERWISE PROVIDED FOR
  • B60N2/00—Seats specially adapted for vehicles; Arrangement or mounting of seats in vehicles
  • B60N2/64—Back-rests or cushions
  • B60N2/66—Lumbar supports
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60N—SEATS SPECIALLY ADAPTED FOR VEHICLES; VEHICLE PASSENGER ACCOMMODATION NOT OTHERWISE PROVIDED FOR
  • B60N2/00—Seats specially adapted for vehicles; Arrangement or mounting of seats in vehicles
  • B60N2/68—Seat frames

Definitions

• the present invention relates to a seat structure suitable for use in vehicles such as automobiles, aircraft, trains, and ships, and a torsion bar suitable for use in this seat structure.
• Patent Documents 1 and 2 a seat structure in which a pelvis support member that comes into contact with the upper part of the pelvis of a seated person is provided on the backrest.
• This pelvis support member is connected to a torsion bar via a link member and is biased forward with a predetermined elastic force, and input vibrations cause the pelvis support member to move back and forth along with the up and down movement of the seat, which works synergistically so that it easily follows the rotational movement of the pelvis that accompanies the input vibrations and is highly effective in reducing vibrations that people find unpleasant.
• an impact force greater than a predetermined level is input, the pelvis presses the pelvis support member in a backward rotational direction, and the pelvis is displaced so that it rides on the pelvis support member, absorbing the impact force.
• the seat structures disclosed in Patent Documents 1 and 2 have improved vibration absorption and shock absorption characteristics by using a pelvis support member, and can achieve a comfortable ride with less fatigue.
• the movement of a seated person while riding in a vehicle is affected by complex factors such as the direction of travel of the vehicle and up and down vibrations caused by unevenness of the road surface. Therefore, the body of the seated person, especially the upper body, is affected by input vibrations not only in the up and down and front and rear directions, but also in the left and right directions and the rotational direction (yaw direction) around the trunk.
• the pelvis support members disclosed in Patent Documents 1 and 2 are not sufficient to deal with such movements, and there is room for improvement.
• the structure since the front edge of the seat abuts against the back side of the thigh near the back of the knee, it is desirable that the structure has a predetermined supportability, but does not exert too strong a pressure force and has excellent followability to the movement of the legs.
• the applicant has proposed a mechanism in which the front frame is supported swingably by a torsion bar that spans the left and right direction of the seat, as shown in Patent Document 3.
• the entire front frame swings back and forth evenly in the left-right direction, the movement of one leg causes the part supporting the other leg to move in the same way. For example, if one leg sinks, the entire front frame sinks, reducing the support for the other leg.
• the support will be higher.
• the torsion bar that elastically supports the pelvis support member and the front frame is incorporated into the seat structure, it is necessary to prevent breakage, and so conventionally the torsion bar is housed in a pipe, but housing it in a pipe increases the number of parts, which hinders weight reduction.
• the present invention has been made in consideration of the above, and aims to provide a seat structure that improves support for the pelvis and thighs and increases posture stability when seated. It also aims to provide a torsion bar that is suitable for use in seat structures, has excellent bending properties, and can contribute to reducing the weight of the seat structure.
• the present invention provides A seat structure having a seat portion and a backrest
• the present invention provides a seat structure in which a body support mechanism is provided on at least one of the seat and the backrest, the body support mechanism including a support plate whose longitudinal direction is arranged along the left-right direction of the seat or the backrest, and an elastic support mechanism which biases the support plate in a direction to bring it closer to a body part of the seated occupant and supports the support plate so that it can be displaced in a rotational direction around a central position in the longitudinal direction.
• the elastic support mechanism includes: A pair of arm members provided at a predetermined interval in the left-right direction on a frame constituting the seat portion or the backrest; a torsion bar used as a rotation shaft for rotatably supporting each base portion of the pair of arm members on the frame, It is preferable that the tip end of each of the pair of arm members is rotatably supported by the support plate.
• the tip ends of the pair of arm members are connected to the support plate via link plates.
• the body support mechanism is preferably configured such that, when the spring constant obtained from the load-deflection characteristics obtained by pressing the support plate is k1, the spring constant in the displacement range up to the equilibrium point when seated is k2, the spring constant in a predetermined displacement range from the equilibrium point is k3, and the spring constant in a displacement range beyond the predetermined displacement range from the equilibrium point is k3, the spring constant k2 is the largest among the spring constants k1, k2 and k3, the body support mechanism is supported by a spring force of spring constant k2 at the equilibrium point when seated, and a spring force of spring constant k1 or k3 acts when vibration is input.
• the support plate is formed in a shape such that each end portion in the longitudinal direction is located forward of a central portion in the longitudinal direction.
• the body support mechanism is configured as a pelvis support mechanism in which the support plate is disposed at a pelvis corresponding portion of the backrest, It is preferable that the support plate constituting the pelvic support mechanism has a lower edge that is below a position on the pelvis of the seated person corresponding to at least the upper part of the sacrum and does not contact the seat, and an upper edge that is above the position corresponding to at least the upper part of the sacrum and in a range up to a position corresponding to the fourth lumbar vertebra.
• the body support mechanism is preferably configured as a thigh support mechanism in which the support plate is disposed at a position corresponding to the thighs near the front edge of the seat.
• a seat net is hung across the cushion frame constituting the seat with a predetermined tension
• a backrest net is hung across the back frame constituting the backrest with a predetermined tension.
• the seat net and the backrest net are three-dimensional knitted fabrics knitted using synthetic resin multifilaments or monofilaments.
• the torsion bar is heat-treated, a hard layer having an average hardness higher than that of other layers on a center side of a cross section taken along a radial direction perpendicular to the longitudinal direction; From the hard layer toward the surface side, there are a flat hardness layer having a substantially constant hardness, a soft layer having a gradually decreasing hardness, and a decarburized layer, It is preferable that the flat hardness layer, the soft layer and the decarburized layer are formed in a ring shape along the outer periphery of a cross section along the radial direction and surround the hard layer, forming a multi-layer structure.
• the hard layer is preferably formed within a range of a distance of 30 to 70% of the radius of the torsion bar from the center of a cross section perpendicular to the longitudinal direction of the torsion bar. It is preferable that the width of the ring of the flat hardness layer corresponds to 5 to 40% of the radius of the torsion bar, and the width of the ring of the soft layer corresponds to 15 to 60% of the radius of the torsion bar. It is preferable that the width of the ring of the decarburized layer corresponds to 1% or less of the radius of the torsion bar.
• a torsion bar used as a spring material in a seat structure which is incorporated in a seat portion or a backrest and arranged to elastically support the seat portion or the backrest, It is manufactured by heat treatment, a hard layer having an average hardness higher than that of other layers on a center side of a cross section taken along a radial direction perpendicular to the longitudinal direction; From the hard layer toward the surface side, there are a flat hardness layer having a substantially constant hardness, a soft layer having a gradually decreasing hardness, and a decarburized layer,
• the torsion bar has a multi-layer structure in which the flat hardness layer, the soft layer and the decarburized layer are formed in a ring shape along the outer periphery of a cross section along the radial direction and surround the hard layer.
• the hard layer is preferably formed within a range of a distance of 30 to 70% of the radius of the torsion bar from the center of a cross section perpendicular to the longitudinal direction of the torsion bar. It is preferable that the width of the ring of the flat hardness layer corresponds to 5 to 40% of the radius of the torsion bar, and the width of the ring of the soft layer corresponds to 15 to 60% of the radius of the torsion bar. It is preferable that the width of the ring of the decarburized layer corresponds to 1% or less of the radius of the torsion bar.
• the seat structure of the present invention has, as a body support mechanism, a support plate arranged so that its longitudinal direction is aligned with the left-right direction of the seat or backrest, and which is biased in a direction to bring it close to the body parts of the seated person, and this support plate is supported by an elastic support mechanism so that it can be displaced in a rotational direction around a central position in the longitudinal direction.
• a pelvis support mechanism at the part of the backrest corresponding to the pelvis, the physiological curvature of the spine is more easily maintained, the shoulder blades are more easily abutted against the upper part of the backrest, and a stable seated posture is more easily maintained.
• the support plate moves in the same direction following the pelvis.
• the back of the seated person can respond to various vehicle movements, not just up and down and front and back, and the pelvis and shoulder blades are prevented from moving too far away from the backrest while riding, improving posture stability, reducing the effects of vibrations transmitted from the vehicle body to the seated person, suppressing increased sympathetic nerve activity, and contributing to maintaining a more relaxed riding posture.
• the body support mechanism is provided as a thigh support mechanism near the front edge of the seat, it is more responsive to the movement of each leg, improving thigh support.
• the torsion bar of the present invention has high bending properties, there is no need to house the torsion bar inside a covering pipe as in the past, and it can be placed as is, which contributes to reducing the weight of the seat structure.
• FIG. 1(a) is a perspective view showing a seat structure according to one embodiment of the present invention
• FIG. 1(b) is a perspective view showing the internal structure with a seat net and a backrest net removed.
• FIG. 2(a) is a perspective view of the pelvis support mechanism used in the above embodiment as viewed from the rear direction
• FIG. 2(b) is a rear view of the pelvis support mechanism.
• FIG. 3 is a plan view of the seat structure showing the movement of the pelvis support mechanism.
• FIG. 4 is a graph showing the load-deflection characteristics of the pelvis support mechanism.
• FIG. 5(a) is a diagram showing the state of a vibration experiment, and FIGS.
• FIG. 5(b) and 5(c) are diagrams showing the state of an experiment relating to the evaluation of physiological indices.
• FIG. 6 is a graph showing the transmissibility of vertical vibration occurring in the seat in a vibration experiment.
• FIG. 7 is a graph showing the transmissibility of vibration in the left-right direction occurring in the backrest in a vibration experiment.
• FIG. 8 is a graph showing the transmissibility of vibration in the front-rear direction occurring in the backrest in a vibration experiment.
• Figure 9(a) is a diagram showing the dynamic body pressure distribution in the backrest of the seat structure of the comparative example when vertical vibrations are input at 5 Hz using a single-axis vibrator
• Figure 9(b) is a diagram showing the dynamic body pressure distribution in the backrest of the seat structure of the embodiment when vertical vibrations are input at 5 Hz using a single-axis vibrator
• Figure 9(c) is a diagram showing the dynamic body pressure distribution in the backrest of the seat structure of the comparative example when left-right vibrations are input at 5 Hz using a six-axis vibrator
• Figure 9(d) is a diagram showing the dynamic body pressure distribution in the backrest of the seat structure of the embodiment when left-right vibrations are input at 5 Hz using a six-axis vibrator.
• FIG. 10 is a graph showing the measurement results of blood pressure and heart rate.
• 11(a) and (b) are graphs showing power spectra (logarithmic representation) for ECG, PPG, APW temporal data, APW back data, APW lumbar data, and APW buttocks data, where FIG. 11(a) is a graph analyzing measurement data for a comparative example seat structure, and FIG. 11(b) is a graph analyzing measurement data for a seat structure according to an embodiment.
• FIG. 12(a) and (b) are graphs showing time waveforms of ECG, PPG, APW left head data, APW back data, APW lumbar data, and APW buttocks data, and show data measured with the comparative example seat structure in FIG. 12(a) and data measured with the seat structure of the embodiment in FIG. 12(b).
• FIG. 13 is a diagram for explaining the posture of a human dummy when seated in the seat structure according to the embodiment.
• 14(a) and (b) are diagrams for explaining the fatigue test method.
• FIG. 15 is a graph showing the hardness distribution in a cross section along the diameter direction when the center position of the torsion bars A and B is set to 0 mm.
• FIG. 15 is a graph showing the hardness distribution in a cross section along the diameter direction when the center position of the torsion bars A and B is set to 0 mm.
• FIG. 16( a ) shows the hardness distribution shown in color coding on a cross section along the diameter direction of torsion bar A
• FIG. 16 ( b ) shows the hardness distribution shown in color coding on a cross section along the diameter direction of torsion bar B
• FIG. 17 is a graph showing the fatigue test results.
• FIG. 18 is a graph showing the results of a bending test with downward restriction.
• FIG. 19 is a graph showing the results of a bending test with vertical restriction.
• FIG. 20(a) is a photograph showing the appearance of torsion bar A after a bending test with vertical restriction has been performed
• FIG. 20(b) is a photograph showing the appearance of torsion bar B after a bending test with vertical restriction has been performed.
• FIG. 21(a) and (b) show the measured spring constant and the calculated spring constant for different effective lengths of the torsion bar A, where (a) is the data for an effective length of 150 mm, and (b) is the data for an effective length of 174 mm.
• FIG. 22(a) is a scanning electron microscope photograph showing the state of the fracture surface of torsion bar A that fractured in the torsion test
• FIG. 22(b) is a scanning electron microscope photograph showing the state of the fracture surface of torsion bar B that fractured in the torsion test.
• FIG. 23 is a conceptual diagram showing a high-frequency induction heating device that heat-treated the torsion bar used in the experiment.
• FIG. 24 is a perspective view showing a frame structure of a seat structure according to another embodiment of the present invention.
• a seat structure 1 of this embodiment includes a seat portion 2 and a backrest 3.
• This seat structure 1 is an automobile seat, and the backrest 3 is supported relative to the seat portion 2 so as to be recliningable.
• the seat 2 has a cushion frame 20 having a pair of side frames 21, 22 arranged at a predetermined distance from each other in the left-right direction of the seat structure 1, a front frame 23 arranged between the front parts of the pair of side frames 21, 22, and a rear frame 24 arranged between the rear parts of the pair of side frames 21, 22.
• a base net 2a is hung between the pair of side frames 21, 22, and a seat net 2b is arranged to cover the upper part of the base net 2a and to be hung across the pair of side frames 21, 22 and the front frame 23.
• the seat net 2b is hung across the cushion frame 20 in this way, forming a tension structure arranged with a predetermined tension.
• the backrest 3 has a back frame 30 which has a pair of side frames 31, 32 arranged at a predetermined distance in the left-right direction of the seat structure 1, an upper frame 33 arranged between the upper parts of the pair of side frames 31, 32, and a lower frame 34 arranged between the lower parts of the pair of side frames 31, 32.
• a base net 3a is hung between the pair of side frames 31, 32 and a backrest net 3b is arranged to cover the upper part and hang across the pair of side frames 31, 32 and the upper frame 33.
• the backrest net 3b is also hung across the back frame 30 and is a tension structure arranged with a predetermined tension.
• the seat net 2b and backrest net 3b are preferably made of three-dimensional knitted fabric.
• the three-dimensional knitted fabric is formed by connecting a pair of ground knitted fabrics arranged at a distance from each other with a connecting thread.
• the thickness of the ground thread forming the ground knitted fabric is selected so that it can provide the necessary stiffness for the three-dimensional knitted fabric and does not make the knitting work difficult.
• monofilament can be used as the ground thread
• multifilament can also be used from the viewpoint of texture and softness of the surface feel.
• multifilament yarn can be used as the connecting yarn, it is preferable to use monofilament yarn since it is easier to obtain the desired elasticity.
• Various materials can be used for the yarns or connecting yarns that form the ground fabric of the three-dimensional knitted fabric, but preferably they are made of synthetic resin, such as polyester fibers represented by polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polyamide fibers represented by nylon 6 and nylon 66, polyolefin fibers represented by polyethylene and polypropylene, or a combination of two or more of these fibers. Because three-dimensional knitted fabrics are constructed in this way, they have the characteristics of high surface rigidity and a low coefficient of friction.
• PET polyethylene terephthalate
• PBT polybutylene terephthalate
• nylon 6 and nylon 66 polyamide fibers represented by nylon 6 and nylon 66
• polyolefin fibers represented by polyethylene and polypropylene
• the pelvis support mechanism 4 which is a body support mechanism, is supported by either the cushion frame 20 that constitutes the seat portion 2 or the back frame 30 that constitutes the backrest 3. As shown in Figures 2 and 3, the pelvis support mechanism 4 has an elastic support mechanism 40 including a pair of arm members 41, 42 and torsion bars 44, 45 that are provided at a predetermined distance in the left-right direction of the seat structure 1, and a support plate 43 that is supported by this elastic support mechanism 40.
• the pair of arm members 41, 42 are rotatably supported on the lower parts of the side frames 31, 32.
• L-shaped brackets 35, 36 are fixed to the inside of the lower parts of the side frames 31, 32 with bolts or the like.
• connect plates 311, 321 are also fixed to the inside of the lower parts of the side frames 31, 32.
• the bases 41a, 42a of the arm members 41, 42 are positioned between the L-shaped brackets 35, 36 and the bent surfaces 31a, 32a formed by bending the lower parts of the connect plates 311, 321 inward, via bushes 35b, 36b.
• the lower surfaces 35a, 36a of the L-shaped brackets 35, 36 and the bases 41a, 42a of the arm members 41, 42 have insertion holes, and the lower parts 44a, 45a of the torsion bars 44, 45, which are arranged with the vertical direction as the longitudinal direction, are inserted into these insertion holes in a non-rotatable manner and connected to the bushes 35b, 36b.
• the torsion bars 44, 45 function as rotation shafts that rotatably support the bases 41a, 42a of the arm members 41, 42 on the lower parts of the side frames 31, 32.
• the upper parts 44b, 45b of the torsion bars 44, 45 are fixed to appropriate positions on the upper part of the back frame 30 via the fixing bushes 37, 38.
• the arm members 41, 42 are arranged so that the tip ends 41b, 42b extend toward the center of the backrest 3, and the tip ends 41b, 42b are supported on the back side of the support plate 43 via link plates 48, 49 (described later) at a predetermined interval in the left-right direction of the backrest 3.
• the support plate 43 is formed in a roughly rectangular shape and is arranged in such a manner that its longitudinal direction is along the left-right direction of the backrest 3 and its width direction is along the up-down direction of the backrest 3.
• a mounting bracket 431 having a predetermined length along the longitudinal direction of the support plate 43 is fixed to the back of the support plate 43, and a roughly U-shaped cross-section having opposing surfaces 431a, 431b at the top and bottom is provided near each end of the mounting bracket 431.
• Axle members 432, 433 are arranged between the opposing surfaces 431a, 431b.
• Link plates 48, 49 are hung between the shaft members 432, 433 and the connecting shafts 46, 47 provided at the tips 41b, 42b of the arm members 41, 42 to connect the two. Two link plates 48, 49 are used on the top and bottom, and the tips 41b, 42b of the arm members 41, 42 are placed between them.
• the support plate 43 can be displaced in the rotational direction around the center position C in the longitudinal direction in a plan view (when viewed from above the backrest 3) as shown in FIG. 3. Therefore, when the position of the pelvis of the seated person moves left and right or in a rotational direction around the trunk, the support plate 43 will move in the same direction, and the link plates 48, 49 will move in the rotational direction accordingly.
• the central portion 43a is flat, which is a range of a predetermined length including the central position C in the longitudinal direction, and the ends 43b and 43c on both sides are located forward of the central portion 43a, and are formed with inclined surfaces 43d and 43e that are inclined diagonally forward from the boundaries with the central portion 43a of a predetermined length toward the ends 43b and 43c.
• the central portion 43a and the inclined surfaces 43d and 43e of the support plate 43 are closer to the shape of the pelvis of the seated person, and the support area is increased.
• the support plate 43 is disposed with its width oriented along the vertical direction of the backrest 3, but the lower edge 43f is provided below a position corresponding to at least the upper part of the sacrum of the pelvis when in a seated position, and in a range that does not contact the seat 2.
• the upper edge 43g varies depending on the position of the lower edge 43f and the width of the support plate 43 (the length between the lower edge 43f and the upper edge 43g), but is provided so as to be at least above a position corresponding to the upper part of the sacrum, and preferably up to a position corresponding to the fourth lumbar vertebra. This allows the support plate 43 to support the part of the seated person's pelvis that corresponds to the pelvis.
• the physiological curvature of the spine makes it easier for the shoulder blades to come into contact with the upper part of the backrest 3, and the backrest 3 becomes a support structure centered on the pelvis and shoulder blades. If the position of the upper edge 43g of the support plate 43 is higher than the position corresponding to the fourth lumbar vertebra, it may become difficult to maintain the physiological curvature of the spine, so it is preferable to keep it within the above range.
• the backrest net 3b is arranged to be hung across the pair of side frames 31, 32 and the upper frame 33 of the back frame 30.
• the backrest net 3b is cut at a position above the pelvis support mechanism 4.
• the backrest net 3b is arranged to cover the front surface of the support plate 43 of the pelvis support mechanism 4, and the cushioning properties of the backrest net 3b reduce the impact of the support plate 43.
• the support plate 43 is biased in a direction that protrudes forward by the torsion bars 44, 45, so that the tension acts on the backrest net 3b covering the front surface of the support plate 43, and it also has the function of suppressing sagging and wrinkles when hung across the back frame 30.
• the torsion bars 44, 45 are arranged with their torsion angles adjusted so that, in the normal state, they bias the tip ends 41b, 42b of the arm members 41, 42 in a direction that protrudes forward. It is preferable to use heat-treated torsion bars 44, 45, and further, as shown in Figures 15 and 16(b), a hard layer (T1) with a relatively higher average hardness than other layers is formed at the center by quenching and tempering as a hardness distribution in a cross section along the radial direction perpendicular to the longitudinal direction, and a multi-layer structure of four layers in total is formed from this hard layer (T1) toward the surface side, with a flat hardness layer (T2), a soft layer (T3), and a decarburized layer (T4).
• the flat hardness layer (T2), the soft layer (T3), and the decarburized layer (T4) are formed in a ring shape along the outer periphery of the cross section along the radial direction, and surround the
• the hard layer (T1) has a martensite structure and preferably has a Vickers hardness of 550 Hv or more, and more preferably 570 Hv or more.
• the hard layer (T1) is preferably formed within a distance of 30 to 70% of the radius of the torsion bars 44, 45 from the center of the torsion bars 44, 45, and more preferably within a distance of 35 to 65%.
• the flat hardness layer (T2) has a substantially constant hardness within its range, and in the graph of FIG. 15, it appears as a substantially horizontal change, and indicates a range in which there is a plateau-like step shape between the hard layer (T1) and the soft layer (T3). Since the hardness is substantially constant, it is preferable that the hardness difference within the range of the flat hardness layer (T2) is within 20 Hv, preferably within 10 Hv.
• the hardness of the flat hardness layer (T2) is slightly lower than that of the hard layer (T1), and is preferably in the range of 500 to 600 Hv in Vickers hardness. More preferably, it is in the range of 550 to 570 Hv.
• the width of the ring of the flat hardness layer (T2) is preferably 5 to 40% of the radius of the torsion bars 44, 45, and more preferably 20 to 30%.
• the soft layer (T3) is formed so that its hardness gradually decreases toward the surface. It is preferably formed so that its hardness gradually decreases in the range of 600 to 350 Hv, and more preferably in the range of 570 to 420 Hv.
• the ring width of the soft layer (T3) is preferably equivalent to 15 to 60% of the radius of the torsion bars 44, 45, and more preferably equivalent to 45 to 55%. Having a ring-shaped soft layer (T3) contributes to durability against torsion and reduces notch sensitivity due to minor scratches on the surface.
• the decarburized layer (T4) is the layer formed on the outermost surface and has the lowest hardness, and the width of this ring is equivalent to 1% or less of the radius of the torsion bar. This layer contributes to improving bending characteristics, but if it is too wide (formed deep from the surface), it will affect durability, so it is preferable to keep it in the range of 1 to 10 ⁇ m.
• the torsion bars 44, 45 have a flat hardness layer (T2), a soft layer (T3), and a decarburized layer (T4) surrounding the central hard layer (T1) in a ring shape, which provides a balance between hardness and bending characteristics, provides the desired durability, and suppresses breakage when an impact load is applied.
• the heat treatment for imparting the above characteristics to the torsion bars 44 and 45 is carried out as follows.
• the heat treatment is preferably carried out by high-frequency induction heating.
• Figure 23 shows the high-frequency induction heating device used for the heat treatment of the torsion bars A and B in the experimental example described later.
• the torsion bar (workpiece) to be heat treated is placed in the coil of the high-frequency induction heating device.
• a torsion bar used as a spring material that is incorporated into the seat 2 or backrest 3 of the seat structure 1 of an automobile and is arranged with one end fixed to one of the frames to elastically support the seat 2 or backrest 3, a torsion bar with a diameter of about 5 to 20 mm is used.
• the diameter is 7.8 mm.
• the frequency during high-frequency induction heating is preferably 100 kHz or less, more preferably in the range of 10 to 40 kHz, and even more preferably in the range of 20 to 30 kHz.
• the quenching process involves first rapidly heating the material to a temperature higher than the A1 transformation point, followed by rapid cooling.
• the material is rapidly heated to 200-400°C, preferably 220-350°C, followed by rapid cooling.
• rapid heating is preferably performed at a rate of 300°C/sec or higher, more preferably 400°C/sec or higher
• rapid cooling is preferably performed at a rate of 300°C/sec or higher, more preferably 800°C/sec or higher.
• the rapid cooling process is performed within 1 second, preferably 0.4 to 0.8 seconds. This results in the multi-layered torsion bars 44, 45 that have the above-mentioned characteristics, but it is important not to raise the tempering temperature too high and to perform rapid cooling as quickly as possible.
• the pelvis presses the support plate 43 of the pelvis support mechanism 4.
• the support plate 43 is biased forward, that is, in a direction approaching the pelvis, which is a body part, by the torsion bars 44, 45 via the arm members 41, 42, and therefore presses the pelvis and supports it when the person sits.
• This makes it easier to maintain the physiological curvature of the spine, and makes it easier for the shoulder blades to abut against the upper part of the backrest 3 when the person sits.
• it becomes easier to maintain a stable seated posture and the transmission of input vibrations in the up and down direction to the person is suppressed.
• the support plate 43 can follow that movement (the dashed line in Figure 3 shows the movement of the support plate 43), so that support of the pelvis can be maintained even when such a movement occurs. Therefore, even when the input vibration acts in the left-right direction, the vibration transmitted to the back of the person sits on the seat is suppressed.
• the spring force of the torsion bars 44 and 45 acts, creating a phase difference and even an opposite phase, which dampens the vibration.
• the seat structure 1 of this embodiment has the pelvis support mechanism 4 of the above-mentioned structure, which stabilizes the seated posture and makes it easier to suppress the transmission of input vibrations, thereby contributing to increased comfort when riding.
• the torsion bars 44, 45 were 7.8 mm in diameter and 500 mm in length, and had a four-layered structure as shown in Fig. 15 and Fig. 16(b).
• the seat structure of the comparative example does not have a pelvis support mechanism 4, but has a lumbar support that supports the first to third lumbar vertebrae, and has pads on the sides, and the sides bulge slightly forward compared to the seat structure 1 of this embodiment, placing emphasis on side support.
• the other structures, including the frame shape, base nets 2a, 3a, seat net 2b, and backrest net 3b, are the same as those of the seat structure 1 of this embodiment.
• the subjects were five men in their 20s to 60s.
• (Static load characteristics) 4 is a diagram showing the static load characteristics of the pelvis support mechanism 4. This shows the load-deflection characteristics when the center of the support plate 43 of the pelvis support mechanism 4 is pressed by 50 mm with a pressure plate having a diameter of 100 mm.
• the pelvis support mechanism 4 has four different spring constants, k1 to k4.
• the spring constant k1 0.3 kg/mm is applied due to the tension of the backrest net 3b associated with the rearward displacement of the support plate 43 up to a displacement of approximately 31 mm (the displacement range from when the person sits down to the equilibrium point).
• the spring constant switches from k1 to k2: 2 kg/mm. This is the point at which the arm members 41, 42 twist from the state in which the support plate 43 has been displaced due to the rotation of the link plates 48, 49, and the spring force of the torsion bars 44, 45 begins to act.
• the specified displacement range where the spring constant k2 acts becomes the equilibrium point when the person sits down, supporting the back of the person sitting down.
• the vibration input was a sine wave with an amplitude displacement of 2 mmp-p in both the up-down direction (log sweep: 0.5-15 Hz (1-axis exciter)), and a sine wave with an amplitude displacement of 10 mmp-p in both the left-right direction (log sweep: 0.5-6 Hz (6-axis exciter)).
• the front-back direction was obtained by measuring the acceleration of the vibration in the front-back direction caused by the vibration input in the up-down direction.
• the acceleration sensors used were Rion seat acceleration pickup PV-62 and Rion acceleration pickup PV-85. One was placed at the location corresponding to the ischial tuberosity to detect acceleration at the seat, and the other was placed at the location corresponding to the fusion of the fifth lumbar vertebra and the sacrum to detect acceleration at the backrest.
• FIGS. 6 to 8 show the results of an experiment on a male subject (in his 30s) weighing 75 kgf and standing 177 cm tall, when vibration was applied in the vertical direction by a one-axis vibration exciter.
• 6 shows the vibration transmissibility due to the vertical vibration acceleration in the seat and the vertical vibration acceleration on the platform of the vibrator.
• the seat structure 1 of this embodiment has reduced acceleration in the resonance frequency bands of 1 to 4.5 Hz and 6.5 to 8 Hz, and it can be seen that the vertical vibration transmitted from the spine to the head and the vibration that resonates with the internal organs are reduced.
• Figure 7 shows the vibration transmissibility due to the left-right vibration acceleration measured on the backrest and the up-down vibration acceleration on the platform of the vibrator.
• the seat structure 1 of this embodiment has a significantly improved left-right vibration transmissibility of 1 to 5 Hz, as well as an improved left-right vibration transmissibility of 6 to 8 Hz, indicating that the support plate 43 of the pelvis support mechanism 4 has high left-right compliance and is effective in absorbing vibrations.
• Figure 8 shows the vibration transmissibility based on the forward/backward vibration acceleration measured on the backrest and the vertical vibration acceleration on the platform of the vibrator.
• the seat structure 1 of this embodiment has a higher forward/backward acceleration at 4 to 6 Hz compared to the seat structure of the comparative example. This shows that the vertical vibration acceleration is converted to the forward/backward direction by the pelvis support mechanism 4, and this phenomenon contributes to the reduction of the vertical vibration acceleration in the seat shown in Figure 6.
• the seat structure 1 of this embodiment has a resonance frequency of 5 Hz (gain is 2.0), but enters the damping range from 6.5 Hz, and vibration is quickly suppressed by the mass of the trunk and the phase difference (opposite phase).
• the seat structure 1 of this embodiment uses a three-dimensional knitted fabric as the seat net 2b of the seat 2, but as described above, the surface of the three-dimensional knitted fabric has low friction and is prone to producing a movement that dampens vibrations converted in the front-back direction by a phase difference (opposite phase).
• Figure 9 shows the dynamic body pressure distribution when vibration was applied at 5 Hz (subject: male in his 30s, weighing 75 kgf and standing 177 cm tall).
• (a) and (b) show the dynamic body pressure distribution when vertical vibration was applied using a one-axis vibrator
• (c) and (d) show the dynamic body pressure distribution when horizontal vibration was applied using a six-axis vibrator.
• 9(a) and (c) show a seat structure of a comparative example, in which the support pressure is high from the first lumbar vertebra to the third lumbar vertebra. Comparing Fig. 9(a) with the dynamic body pressure distribution of the seat structure 1 of this embodiment in Fig. 9(b), it can be seen that the peak value of the support pressure is higher in Fig. 9(a).
• the pelvis support mechanism 4 supports the vicinity of the fourth and fifth lumbar vertebrae, and the support pressure is high in the vicinity of the pelvis and shoulder blades.
• the seat structure of the comparative example has a load concentrated near the lumbar, and the pressure value is high at about 70 mm from the spine, which means that back slap, a phenomenon in which the backrest hits the center of the back, is likely to occur.
• the seat structure 1 of this embodiment has a pelvis support mechanism 4, so the support pressure in the sacrum is high, and as described above, the shoulder blades are likely to come into contact with the backrest 3, and the pressure value is high at a distance of 75 mm or more from the spine. Therefore, while the seat structure of the comparative example is structured to maintain posture using the erector spinae muscles, the seat structure 1 of this embodiment is structured to maintain posture using the skeleton.
• the movement of the shoulder blades is small in response to input vibration, but as shown in the vibration experiment above, the vibration is converted to the front-back direction, so that an inverted pendulum movement in which the pelvis swings back and forth with the shoulder blades as the fulcrum is likely to occur.
• the rocking motion in the front-back direction be a maximum of 50 mm, and even with such a rocking motion, the phase difference and opposite phase occur, as described above, and the rocking motion can be quickly attenuated. This reduces the acceleration in the vertical direction and also reduces the rocking motion of the head.
• FIG. 5(b) shows the state in which the subject sat in the seat structure of the comparative example
• FIG. 5(c) shows the state in which the subject sat in the seat structure 1 of the present embodiment
• FIG. 5(b) shows the measurement positions of each physiological index, all of which are positions seen from the front of the body.
• the measurement positions in FIG. 5(c) are the same as those in FIG. 5(b).
• the APW was measured at four points, the left head, the back, the third to fourth lumbar vertebrae, and the ischial tuberosity.
• the ECG, PPG, and APW were continuously measured for 6 minutes at a sampling frequency of 1000 Hz while the subject sat in each seat structure, and the brachial blood pressure and the heart rate were measured twice before the start of the 6-minute continuous measurement and once after the 6-minute continuous measurement was completed.
• the electrocardiogram sensor used was a Vitrode (registered trademark) F150M manufactured by Nihon Kohden Corporation
• the fingertip volume pulse wave sensor was a finger clip probe SR-5C manufactured by Amco Corporation
• the APW sensor was an acoustic pulse wave detection sensor used in a drowsy driving warning device (Sleep Buster (registered trademark)) manufactured by Delta Touring Corporation.
• Data was recorded on LabChart V8 using a high sensitivity amplifier AB-611J manufactured by Nihon Kohden Corporation and a PowerLab (registered trademark) 8/30 (ML870) manufactured by ADI Instruments. Blood pressure and heart rate were measured using a UM-211 manufactured by A&D MEDICAL.
• Figure 11 is a graph showing the power spectrum (logarithmic) for ECG, PPG, APW temporal data, APW back data, APW lumbar data, and APW buttocks data.
• the ECG, PPG, APW left temporal data, and APW back data were nearly equivalent when measured with the comparative seat structure in Figure 11(a) and when measured with seat structure 1 of this embodiment in Figure 11(b), with little difference between them.
• FIG. 12 shows the time waveforms of ECG, PPG, APW left head data, APW back data, APW lumbar data, and APW buttock data.
• the APW lumbar data and APW buttock data have almost the same amplitude as the APW left head and back data, whereas in the comparative seat structure, the amplitude of the time waveform of the APW lumbar data is very small, and the time waveform of the buttock data also has parts where the amplitude is small due to the effect.
• the comparative seat structure may have a stronger support pressure on the lumbar region, which may increase sympathetic nerve activity and reduce the diameter of blood vessels.
• the above experimental results show that the data of the subjects measured with the seat structure of the comparative example shows an increase in sympathetic nerve activity, whereas the data of the subjects measured with the seat structure 1 of the present embodiment shows parasympathetic nerve activity.
• This is thought to be related to the fact that the seat structure of the comparative example has high support for the lower back and sides of the body, which makes it easy to breathe thoracically when seated, whereas the seat structure 1 of the present embodiment has high support for the pelvis and shoulder blades, which makes it easy to breathe abdominally.
• the seat structure 1 of this embodiment is suitable for suppressing blood flow obstruction in the lumbar region, for assuming a posture that accepts circulatory fluctuations in blood flow rate due to increased parasympathetic nerve activity, and is expected to be highly effective in suppressing the progression of fatigue. Therefore, the enhanced state of the sympathetic and parasympathetic nerves is kept in a balanced and antagonistic state, and the autonomic nerves are easily kept in a moderate state of activation, making it suitable as a driver's seat.
• Figure 13 shows the seated posture of the human dummy set in the seat structure 1 of this embodiment. It also shows the assumed position of the human dummy when the frame of the seat structure of the comparative example is aligned in the same position as the frame of the seat structure 1 of this embodiment. Comparing the two, the torso angle is 22 degrees in the seat structure of the comparative example, while it is 30 degrees in the seat structure 1 of this embodiment.
• the eye point has moved 55.6 mm backward and 64.5 mm downward compared to the seat structure of the comparative example.
• the WL and TL directions of the hip point are the same, so the difference is due to the difference in the torso angle and the spring structure of the backrest.
• the angle between the scythe angle and the torso angle is 115 degrees, which is a layout that makes abdominal breathing easy.
• the backrest 3 is supported by the surface of the tension structure, the base net 3a and the backrest net 3b, and the pelvis is supported by the pelvis support mechanism 4, so the degree of deformation freedom between the waist and chest is high, that is, the degree of freedom of the bending point when bending over is high, so individual differences in physique can be effectively absorbed.
• Torsion bar experiment A torsion bar in which almost the entire area of the structure in the cross section along the radial direction is martensite (hereinafter, “torsion bar A”) and a multi-layered torsion bar in which a hard layer (T1) is formed on the center side of the cross section along the radial direction, and a flat hardness layer (T2), a soft layer (T3), and a decarburized layer (T4) are formed in this order toward the surface side (hereinafter, "torsion bar B”) were manufactured. Both torsion bars A and B have a diameter of 7.8 mm.
• Torsion bar A was rapidly heated to 900°C in about 1 second so that it was hardened to the center, and then rapidly cooled to below 200°C in about 0.5 seconds.
• Torsion bar B was hardened under the same conditions as torsion bar A, and then further subjected to low-temperature heat treatment in which it was rapidly heated to about 260°C in about 0.5 seconds, and then rapidly cooled to below 200°C in about 0.5 seconds.
• FIG. 15 is a graph showing the hardness distribution of the cross section along the diameter direction when the center position of the torsion bars A and B is 0 mm, and Figures 16(a) and (b) show the hardness distribution shown by color coding in the cross section along the diameter direction.
• the torsion bar A has a small layer of low hardness within a range of 0.8 mm from the surface, but most of the range has a hardness of 680 Hv to about 700 Hv.
• the area of 3 mm radius from the center was a martensite structure with a hardness of more than about 700 Hv.
• the torsion bar B has a roughly circular hard layer (T1) with a diameter of about 4 mm formed in the center, a ring-shaped flat hardness layer (T2) with a width of about 1 mm formed on the outside of the hard layer (T1) so as to surround the hard layer (T1), a ring-shaped soft layer (T3) with a width of about 2 mm formed on the outside of that, and a decarburized layer (T4) with a width of about several ⁇ m formed on the outer surface of that.
• T1 hard layer
• T2 ring-shaped flat hardness layer
• T3 ring-shaped soft layer
• T4 decarburized layer
• the radius of the hard layer (T1) was about 51%
• the width of the flat hardness layer (T2) was about 25%
• the width of the soft layer (T3) was about 51%
• the width of the decarburized layer (T4) was less than about 0.3%.
• the hardness of the hard layer (T1) was approximately 590 Hv
• the flat hardness layer (T2) was approximately 550 to 570 Hv
• the soft layer (T3) was approximately 420 to 570 Hv.
• torsion bar A achieved 1 million cycles at a torsion angle of 20.75 degrees
• torsion bar B achieved 1 million cycles at a torsion angle of 16.75 degrees.
• the difference in torsion angle is the difference in surface hardness.
• the torsion bar B has a torsion angle of 55.83 degrees when the length is 500 mm.
• FIG 22 (a) is a photograph of the fracture surface of torsion bar A with martensitic structure taken with a scanning electron microscope. The observation positions are a, b, and c shown in the photograph of the fracture surface at the top left, with a being the surface side, c being the center side, and b being a position between the two. The two microscope photographs at each observation position are shown at the top right and bottom.
• Torsion bar A with martensitic structure shows a lot of grain boundary fracture near the surface, and dimples can be observed near the center. Brittle fracture occurred on the surface, followed by ductile fracture, resulting in a fracture form similar to that of carburized quenching.
• Figure 22 (b) is a photograph of the fracture surface of the multi-layered torsion bar B taken with a scanning electron microscope.
• the observation positions are a, b, and c shown in the photograph of the fracture surface at the top left, with a and c both being on the surface side and b being on the center side.
• the two microscope photographs at each observation position are shown at the top right and bottom.
• the surface layer especially at position c
• the center side of b is dominated by martensite structure.
• the areas between b and c and between a and b correspond to the hardness plateau layer (T2) that appears in the above-mentioned plateau shape where the two phases of ferrite structure and martensite structure are in balance, and are the critical phases of the two structures. It is assumed that the presence of this critical phase creates a synergistic effect, resulting in performance similar to that of dual-phase steel. Therefore, dimples caused by the presence of ferrite structure in the surface layer can be seen in the intermediate hardness flat layer (T2) and the central hard layer (T1), which is thought to be the reason why brittle fracture did not occur.
• Figs. 17 and 21 show that although there is a difference in hardness between the martensite torsion bar A and the multi-layered torsion bar B, the fifth power law can be applied to the S-N curve for durability prediction in both cases.
• 17 to 20 show that while torsion bar A has sufficient characteristics as a spring by increasing only its hardness, torsion bar B not only has the characteristics as a spring, but also has a good balance between hardness and bending characteristics, making it suitable as a structural member.
• the multi-layered torsion bar B in this experimental example is used as the torsion bars 44, 45 used in the pelvis support mechanism 4, which is the body support mechanism of the above embodiment.
• the torsion bars 44, 45 in the above embodiment are arranged near the side frames 31, 32 of the back frame 30 that constitutes the backrest 3. For this reason, it is important that the load-bearing strength is high so that the torsion bars 44, 45 do not easily break when an impact load is input, and it is preferable to use a multi-layered torsion bar B that exhibits high bending characteristics. This eliminates the need to house the torsion bars inside a covering pipe as in the past, and they can be arranged as is, which contributes to reducing the weight of the seat structure 1.
• the strength of the seat structure 1 including the back frame 30 can be improved, which in turn contributes to reducing the weight of the frame materials that constitute the back frame 30, etc.
• the torsion bar that has been subjected to the above-mentioned heat treatment is not limited to being incorporated into the back frame 30 and elastically supporting the backrest 3, as in the seat structure 1 of the above-mentioned embodiment, but can also be incorporated into the seat portion 2 of the seat structure 1 and used to elastically support a frame or cushion member provided in the seat portion.
• Fig. 24 shows the frame structure of a seat structure 1' according to another embodiment of the present invention.
• the backrest 3 is provided with a pelvis support mechanism 4 of the same structure as in the above embodiment, but the seat portion 2 is provided with a thigh support mechanism 4000, which is a body support mechanism.
• the front bracket 230 and the rear bracket 240 are disposed below the front frame 23 and the rear frame 25, respectively, and the torsion bars 4440, 4450 constituting the elastic support mechanism 4400 are hung along the front-to-rear direction of the seat 2 near the side frames 21, 22 of the front bracket 230 and the rear bracket 240.
• the torsion bars 4440, 4450 are arranged so that the rear ends 4441, 4451 are fixed ends and the front ends 4442, 4452 are movable ends.
• the bases of the arm members 4410, 4420 are connected to the front ends 4442, 4452, respectively, and the arm members 4410, 4420 can rotate in the vertical direction around the torsion bars 4440, 4450 as the rotation axis.
• the arm members 4410, 4420 are positioned so that their tips extend to the center of the front edge of the seat 2, and are rotatably connected to link plates 4480, 4490 similar to those in the above embodiment.
• the link plates 4480, 4490 are provided on the back side of the support plate 4430. Therefore, the support plate 4430 is provided at a position corresponding to the area of the thigh near the knee, that is, in the area corresponding to the thigh near the front edge of the seat 2.
• the support plate 4430 is formed in a roughly rectangular shape and is positioned so that its length is aligned with the left-right direction of the seat 2 and its width is aligned with the front-rear direction of the seat 2.
• the connecting structure of the arm members 4410, 4420 and the link plates 4480, 4490 is exactly the same as the structure adopted in the pelvis support mechanism 4 of the above embodiment.
• the torsion bars 4440, 4450 urge the support plate 4430 upward, i.e., in a direction approaching the back of the thighs of the seated person.
• the elastic force of the torsion bars 4440 and 4450 allows the support plate 4430 to follow any posture changes that cause the thighs of both legs to displace up and down almost evenly.
• the vibration absorption characteristics can be improved, contributing to improved ride comfort.
• the thigh support mechanism of this embodiment can follow various posture changes of the thighs and provide high support.
• the support plate 4430 has a flat central portion 4431, which is a range of a predetermined length including the central position C in the longitudinal direction, and has inclined surfaces 4434, 4435 such that the ends 4432, 4433 on both sides of the central portion 4431 are higher than the central portion 4431.
• This can suppress left-right positional shifting of the thigh near the back of the knee, and improves followability by following the shape of the thigh.
• the support plate 4430 of this embodiment has the same shape as the support plate 43 of the above embodiment, but the surface corresponding to the body part of the seated person is oriented in a different direction by about 90 degrees, but it can be shaped to match the shape of the thigh. For example, it is also possible to make the inclination angle of the inclined surfaces 4434, 4435 steeper.
• elastic support mechanisms 40, 4400 are incorporated into both the backrest 3 and the seat 2, which are configured as a pelvis support mechanism 4 and a thigh support mechanism 4000, respectively, providing two body part support mechanisms; however, it is also possible to have a mechanism that does not include the pelvis support mechanism 4 and only has the thigh support mechanism 4000 of the seat 2. In that case, the unique advantages of the pelvis support mechanism 4 described in the above embodiment will be lost, but it is possible to improve the supportability of the thighs.

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• Mechanical Engineering (AREA)
• Seats For Vehicles (AREA)
• Chair Legs, Seat Parts, And Backrests (AREA)

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  • 2024-05-31 JP JP2025524926A patent/JPWO2024248158A1/ja active Pending
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