System with adjustable stiffness and method

Abstract

Systems and methods for varying the stiffness of a structural member. A vehicle seat includes the structural member. The structural member has two walls. A connector extends between the walls and has three sections, with one section extending between the other two. The connectors are arranged between the other two sections of the connector and the two walls of the structural member. The connectors can be adjustable to vary the tension in the connector and the stiffness of the structural member.

Description

The present description relates generally to vehicle seats having a frame of structural members, and more particularly to structural seat members having adjustable stiffness.A vehicle seat is designed for structural integrity and performance under a wide range of expected and potential loading scenarios that may occur during operation of the vehicle. Various seat design parameters impact both the structural integrity and the kinematic response of the occupants. When a vehicle in which an occupant is seated experiences a sudden and rapid forward acceleration, the occupant's head may tilt rearward, followed by a reverse tilt rearward in response thereto. The seat and its head restraint may help minimize tilting motion and thus affect the passenger's kinematic response.Design parameters for a desired performance may be determined during product development by modeling and testing. Once determined, the components of the seat may be tailored to the particular seat and vehicle combination. For each application, certain components of the seat are unique and generally cannot be reusable for other applications without design changes.WO 2018 / 139 385 A1 describes a vehicle seat back frame structure to ensure the rigidity of an upper cross member and at the same time to prevent detachment of the connection at a connection part of a closed cross-sectional structure of the upper cross member. The vehicle seat-backrest frame structure is provided with:resin side frames; and an upper cross member extending between the upper portions of the side frames. The upper cross member includes a first member and a second member disposed below the first member. An opening is provided in a lower portion of the first member, and the first member has a horizontal cross-sectional surface shape that is open downward. Moreover, an opening is provided in an upper portion of the second member, and the second member has a horizontal cross-sectional area shape that is open upward. The opening of the first member and the opening of the second member are connected to each other while facing each other, thereby forming a closed cross-sectional area structure.DE 198 17 503 C1 describes reinforcing or stiffening elements in a motor vehicle seat having a seat frame which consists of a base frame and of reinforcing or stiffening elements which are adjustable in their position with respect to the base frame for changing the strength properties of the seat frame, and indeed, if appropriate, according to characteristics of the user. This allows adaptation to be carried out after completion of the seat to characteristic values of the actual user, while conventional seats or seat frames are always designed to be definitive and invariable.Accordingly, it is desirable to provide vehicle seats with structural elements that meet a number of different performance requirements. Moreover, the structural elements of the vehicle seats can preferably be reused in a plurality of applications without requiring redesign. Other desirable features and characteristics of the present invention will become apparent from the following detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing introduction.Systems and methods are provided for varying the stiffness of a structural member.The system according to the invention comprises a vehicle seat and a structural element of the vehicle seat. The structural member has a first wall and a second wall. A connector extends between the first wall and the second wall and has a first portion, a second portion, and a third portion, the second portion extending between the first portion and the third portion. A first connector is disposed between the first portion of the connector and the first wall of the structural member. A second connector is disposed between the third portion of the connector and the second wall. At least one of the first connector and the second connector is adjustable to change the tension in the second portion of the connector and the stiffness of the structural member.In one embodiment, a head restraint of the vehicle seat is coupled to the structural member and a frame is included in the vehicle seat, the structural member comprising a portion of the frame.In another embodiment, the structural member includes a channel forming a pocket and the connector is disposed in the pocket.In a further embodiment, the structural element comprises a web and a third wall. The structural member includes a channel forming a pocket. The first wall includes a first leg of the channel. The second wall includes the web. The third wall consists of a second leg of the channel. The web extends between the first leg and the second leg and forms a C-shape. The connecting piece is connected to the first leg, to the web and to the second leg.In a further embodiment, the vehicle seat has a backrest and the structural element has an upper cross member of the backrest.In another embodiment, a head restraint on the vehicle seat is included, wherein at least one of the first connector and the second connector is configured to adjust the stiffness to balance a response of the head restraint to expected forces with a response of the head restraint to restoring forces.In another embodiment, the connector comprises a stamped part and is arranged to extend along the structural member.In another embodiment, the structural element includes a channel configured to provide the stiffness of the structural element. The structural member includes an angle extending from the channel and configured to increase stiffness. The connecting piece is designed to increase the rigidity.In another embodiment, the connectors are configured to place the connector in either the tension and a compressive force.In another embodiment, the connectors are threaded fasteners.In another embodiment, an adjustable stiffness system includes a vehicle seat having a frame. A structural element of the frame of the vehicle seat has two walls. A connector extends between the walls. The connector has three sections, with a central section extending between the other two outer sections. One outer portion is arranged along one wall of the structural element and the other outer portion is arranged along the other wall of the structural element. A connector is disposed between a portion of the connector and a wall of the structural member. Another connector is disposed between another portion of the connector and another wall of the structural member. At least one connector is adjustable to vary the tension in the central portion of the connector and the stiffness of the structural member.In another embodiment, a headrest is mounted on the vehicle seat. A duct connects the headrest to the frame at the structural element.In another embodiment, the structural member includes a channel having an opening. The channel forms a pocket and the connector is disposed in the pocket.In another embodiment, the structural member comprises a web and a third wall and includes a channel forming a pocket. Two walls form legs of the channel and another forms the web. The web extends between the legs, so that the legs and the web form a C-shape. The connecting piece is connected to the legs and to the web.In a further embodiment, the vehicle seat has a backrest, and the structural element is arranged in the backrest and comprises an upper cross member of the frame.In another embodiment, a head restraint is included on the vehicle seat. Both connectors are configured to adjust the stiffness to balance a response of the headrest to expected forces with a response of the headrest to restoring forces.In a further embodiment, the connecting piece is a metal stamped part and is arranged such that it extends along the structural element in the horizontal direction.In a further embodiment, the structural element comprises a channel which ensures the rigidity of the structural element. The structural member includes an angle extending from the channel to increase stiffness. The joint increases rigidity in addition to increasing the angle.A method according to the invention for providing adjustable stiffness is also provided. The method comprises constructing a vehicle seat and providing a structural element in the vehicle seat. The structural member has a first wall and a second wall. The method further comprises stretching a connector between the first wall and the second wall. The connector includes a first portion, a second portion, and a third portion, the second portion extending between the first portion and the second portion. The method further comprises adding a first connector between the first portion of the connector and the first wall of the structural member. The method further includes adding a second connector between the third portion of the connector and the second wall. The method further comprises adjusting at least one of the first connector and the second connector. The tension in the second portion of the connector and the stiffness of the structural member are varied.In one embodiment, a headrest is provided on the vehicle seat. A balance between an expected force on the headrest and a repulsive force from the headrest is evaluated. Based on the evaluation of the equilibrium, an output stiffness of the structural element is determined. A basic design of the structural member is created to provide the output stiffness. The output stiffness is adjusted with the joint to provide the varying stiffness of the structural member. The base design is reused in various applications requiring different stiffnesses provided by adjusting the output stiffness.The exemplary embodiments are described below in connection with the following drawing figures, wherein like numerals designate like elements, and wherein: FIG. 1 is a schematic illustration of a vehicle seat; FIG. 2 is a schematic perspective view of a frame of the seat of FIG. 1 ; FIG. 3 is a perspective view of a structural member of the seat of FIG. 1 ; FIG. 4 is a schematic cross-sectional view of the structural member of FIG. 3 with adjustable stiffening; FIG. 5 is a perspective view of the adjustable stiffener of FIG. 4 ; and FIG. 6 is a schematic cross-sectional view of the structural member of FIG. 3 with another adjustable stiffener.Referring now to FIG. 1, an example of a vehicle 20 is shown having a body 22 on which a seat 24 is mounted. Generally, the seat 24 includes a seat bottom 26, a seat back 28, and a head restraint 30. For example, one or more shafts 32 connect the head restraint 30 to a structural member 34 in a chassis 36 of the seat back 28 and support the head restraint 30. the structural member 34 may be referred to as a structural portion, a structure, a beam, or a chassis portion in a number of embodiments. In all cases, the structural member 34 is a member of the chassis 36 that provides molding and support capabilities.The head restraint 30 may be subjected to loads during operation of the vehicle 20. For example, the occupant 38 or a portion of the occupant 38, such as his head, may move rearward during a rear impact and apply a force 40 (expected force) to the head restraint 30. The force 40 is transmitted via the shaft(s) 32 to the frame 36 on the structural element 34. This results in a moment 42 on the structural element 34. the structural element 34 or a part thereof can elastically deform, e.g. by twisting, bending or other yielding. The deformation is elastic and corresponds approximately to the winding of a spring. The deformation allows the head restraint 30 to move in a rearward direction 44 so that the occupant does not encounter a hard stop. When the force 40 decreases, the system springs back and the structural member 34 returns to its original state, thereby moving the headrest 30 in a forward direction 46 due to the resiliency. The head restraint 30 may also apply a force 48 (restoring force) to the occupant 38 when moving to its normal position.During the development of the vehicle 20 and seat 24, the parameters of the elastic deformation of the structural member 34 can be evaluated for the expected load from the forces 40. The assessment can be carried out with the aid of commercially available modelling software and / or by tests in practice. The stiffness can be evaluated, wherein the stiffness is a measure of the resistance that the structural element 34 opposes the elastic deformation. The design of the structural member 34 may be based on having sufficient rigidity such that under the expected force (force 40), the amount of elastic deformation is limited to limit the amount of movement of the occupant 38 or a portion of the occupant 38 such that the headrest 30 fulfills its intended restraint function. Moreover, the structural member 34 may be configured with a sufficiently low stiffness to avoid excessive restoring force loading in the form of the restoring force (force 48) applied to the occupant 38. In equilibrium adjustment, the structural stiffness of the structural member 34 is specific to the vehicle 20 / seat 24 combination. In other seats and / or other vehicles, different stiffness of the structural member 34 may be desirable based on the respective evaluation.In Fig. 2, the frame 36 of the seat 24 is shown without its padding and fabric covering. The structural member 34 is formed in the shape of an upper cross member at the upper side of the frame 36 of the seat back 28. In this embodiment, the structural member 34 spans between two side members 50, 52. the structural member 34 is attached to the side members 50, 52, such as by welding, fastening, or other method. In some embodiments, the structural member 34 may be formed as a single piece with one or both side members 50, 52. The frame 36 also includes a lower cross member 54 in the seat back 28 and a strut 56 extending between the side members 50, 52, respectively. In other embodiments, the chassis 36 of the seat back 28 may include a different number of structural elements.Reference is made to FIG. 3 which shows the structural element 34 isolated from the seat frame 36 and viewed from a rear perspective. The structural member 34 is shown without an adjustable stiffness system, which is described further below. The structural element 34 is designed as a stamped part, for example made of steel, with openings 60, 62 for receiving the shaft(s) 32. The structural member 34 extends between a right end 64 connected to the side member 50 and a left end 65 connected to the side member 52, as shown in FIG. 2. The structural member 34 is generally formed as an upper channel 66 that is generally "C" shaped and an integrated lower angle 68 that is generally angular. A variety of materials and methods are available for the production of the structural member, and the general shape is not limited to a C shape, but may take any shape that enables the intended performance.In this non-limiting example, the upper channel 66 and the lower angle 68 have a common leg 70. the upper channel 66 has a rearward open side 67 and includes the leg 70 and a leg 72 connected to the leg 70 by a web 74. Leg 72 includes a return 76 that extends over an upper portion of open side 67 to increase stiffness. In embodiments, the legs 70, 72 and the web 74 may be referred to generally as walls. The legs 70 and 72 are generally horizontally disposed and the web 74 is generally vertically disposed in terms of their similarity to walls. The upper channel 66 defines a pocket 69 which is surrounded on three sides (the walls) by the legs 70, 72 and the web 74. The lower angle 68 includes the leg 70 and another leg 78, and the shapes and features of the portions of the structural member 34 are combined to achieve the desired parameters such as strength, stiffness, and size. The upper channel 66 provides rigidity and the lower angle 68 increases the rigidity of the structural member 34.FIG. 4 shows a cross section, in particular of the upper channel 66 of the structural element 34, with an adjustable stiffness system 80. The adjustable stiffness system 80 includes a connector 82 and fasteners 83-85. The link 82 is a form of adjustable stiffness adjustable by the fasteners 83-85. In the present embodiment, the connecting piece 82 is designed as a bracket and is illustrated in a perspective view in FIG. 5. In other embodiments, the connector 82 may be configured as a cable, strap, spring, or any element or number of elements that may be coupled to the elements of the upper channel 66 to apply tension or other force and / or compressive force thereto. In the present embodiment, the fasteners 83-85 are threaded fasteners such as bolts. The fastening means 83-85 are not limited to screw or bolt type fastenings, but can be implemented as any means for changing the tension within the adjustable stiffness system 80, said means being considered here as fastening means, which can also be referred to as connectors. For example, connectors such as straps, clamps, actuators, sliders, or other devices may be used. In some embodiments, some of the fasteners / connectors may be fixed means (such as welds) without variability, with variable tension provided by other of the fasteners / connectors.As shown in FIG. 5, the connector 82 is formed as a stamped part having five portions 91-95 each substantially planar and bent at different angles relative to their adjacent portions 91-95. The connector 82 is sized to be received in the pocket 69. The portions 91, 93 and 95 are fastening portions and each is formed to be joined to the structural member 34. Portions 91, 93 and 95 each include a number of apertures which may be threaded or include threaded members to receive connectors such as fasteners 83-85. The portion 91 is shaped to be positioned along the leg 72 of the upper channel 66 within the pocket 69. The portion 93 is shaped to be positioned along the web 74 of the upper channel 66 in the pocket 69. The portion 95 is shaped to be positioned along the leg 70 of the upper channel 66 in the pocket 69. The portions 92, 94 are formed as stress / compressive force portions for transmitting forces between their respective mounting portions. The portion 92 extends between the portions 91 and 93 and the portion 94 extends between the portions 93 and 95.As shown in FIG. 4, fastener 83 extends through leg 72 and engages portion 91, fastener 84 extends through web 74 and engages portion 93, and fastener 85 extends through leg 70 and engages portion 95, with connector 82 disposed in pocket 69. In this embodiment, the fasteners 83, 84, 85 are threaded into their respective portions 91, 93, 95. Fasteners 83 may be tightened (increase in torque) to pull portion 91 toward leg 72, and loosened (decrease in torque) to allow portion 91 to move away from leg 72, or reverse torque may be applied to compress portion 92. The fastener 84 may be tightened to pull the portion 93 toward the web 74, and may be loosened to allow the portion 93 to move away from the web 74, or reverse torque may be applied to compress the portions 92, 94. The fastener 85 may be tightened to pull the portion 95 toward the leg 70, and may be loosened to allow the portion 95 to move away from the leg 70, or reverse torque may be applied to compress the portion 94. By adjusting the tension / compression force in the sections 92, 94, the stiffness / spring rate of the adjustable stiffness system 80 and the structural member 34 is adjusted.In embodiments, the fasteners 83-85 form a set that is disposed at a common location along the horizontal length of the structural member 34. Any number of fastener sets may be disposed along the entire length of the structural member 34 between the right end 64 and the left end 65, depending on factors such as the overall length and the force levels involved.In certain embodiments, an increase in torque across fasteners 83 and / or fasteners 84 increases the tension in portion 92 of connector 82. An increase in the torque on the fastening means 85 and / or the fastening means 83 increases the tension in the section 94. an increase in the tension in the section 92 and / or in the section 94 increases the rigidity of the structural element 34. reducing the torque on the fastening means 83 and / or on the fastening means 84 reduces the tension in the section 92. a reduction in the torque on the fastening means 84 and / or the fastening means 85 reduces the tension in the section 94. decreasing tension in the section 92 and / or in the section 94 reduces the rigidity of the structural element 34. Either tension or compression force alters the spring rate of the adjustable stiffness system 80 and the structural member 34.In one example, the fastener 84 may be fully tightened by pulling the portion 93 against the web 74, and the fasteners 83, 85 may be adjusted to achieve the desired stiffness. After adjustment, fasteners 83- 85 may be secured, e.g., by lock nuts (not shown) or by another securing device such as pins, welds, clips, etc. In this way, the response of head restraint 30 to force 40 and the magnitude of generated force 48 may be varied and tuned to the particular application. Therefore, the structural member 34 can be reused in a variety of applications requiring different degrees of rigidity without having to be remodeled.To determine the adjustment of the fastener 83-85, the balance between the expected force and the restoring force may be evaluated by first determining a result of the output stiffness required for the application of the seat 24 in the vehicle 20 and for a basic construction of the structural member 34. This may be done by applying a load to the structural member 34 and / or by performing detailed analysis for certain expected load cases using commercially available modeling software and / or by performing tests for the response of the head restraint 30 and the effects on the occupant 38. If the resulting level of stiffness does not result in the desired results, a stiffness determination is made to determine whether a stiffer system (to improve performance in response to the expected force) or a softer system (to improve response to the restoring force) results in the desired performance in terms of the effect on the occupant 38. The basic construction of the structural member 34 is then reusable in various applications by incorporating the adjustable stiffness system 80. The applied tension / compression force (e.g., by fasteners 83-85) adjusts the stiffness / spring rate of adjustable stiffness system 80, thereby allowing structural member 34 to be tuned to the particular application. Depending on the evaluation of the stiffness, more or less stress or compressive force is applied to the system. As needed, certain attachment points may slip, remain in tension, or transition to compressive force. The evaluation of the stiffness may be repeated to obtain an optimized preload for performance improvement. Experimental Evaluation (DOE) can be used to determine Min / Max values, which stiffness / spring rate represents the optimal solution. The DOE evaluation may include, but is not limited to, the range of material properties of the structural member 34 and other components of the seat 24. Material tolerances, geometric variations, occupant placement variations, and connectors such as foam and trim may be considered in the evaluation. The results of the variation are then used to determine the optimal stiffness value of the structural member 34 required to reduce the standard deviations and achieve the desired performance. The number of additional connections, the geometry and / or the materials can be taken into account. Depending on the result of the evaluation, an increase or decrease of the adjustable stiffness is carried out.FIG. 6 shows an embodiment of a connector 100 having a "Z" shaped portion with portions 101-103. The connector 100 is disposed in the pocket 69, a fastener 104 extends through the leg 72 and engages the portion 101, and a fastener 106 extends through the leg 70 and engages the portion 103. The portion 102 extends between the portions 101 and 103. In this embodiment, the fasteners 104, 106 are threaded into their respective portions 101, 103. The fastener 104 may be tightened to pull the portion 101 toward the leg 72, and loosened to allow the portion 101 to move away from the leg 72. The fastener 106 may be tightened to pull the portion 103 toward the leg 72, and may be loosened to allow the portion 103 to move away from the leg 70.An increase in torque at fasteners 104 and / or fasteners 106 increases the tension in portion 102 of connector 100. Reducing the torque on the fastener 104 and / or the fastener 106 reduces the tension in the portion 102 of the connector 100 or compresses the portion 102. An increase in tension or compressive force in portion 102 increases the stiffness of structural member 34. a decrease in tension or compressive force in portion 102 decreases the stiffness of structural member 34. connector 100 may be a stamped part, or portion 102 may be a cable or other structure in which tension may be varied. By adjusting the tension / compression force of the portion 102, the stiffness / spring rate of the selectively adjustable stiffness system 80 is adjusted.Accordingly, adjustable stiffness systems and methods enable tuning of a structural member to achieve desired performance of a headrest.List of reference characters20 Vehicle 22 Body 24 Seat 26 Seat bottom 28 Seat back 30 Headrest 32 Shafts 34 Structural element 36 Frame 38 Occupant 40 Force 42 Moment 44 Direction 46 Forward direction 48 Force 50 Side elements 52 Side elements 54 Lower cross member 56 Strut 60 Openings 62 Openings 64 Right end 65 Left end 66 Channel 67 Open side 68 Lower angle 69 Pocket 70 Leg 72 Leg 74 Web 76 Return 78 Further leg 80 Adjustable stiffness system 82 Connecting piece 83 Fastening means 84 Fastening means 85 Fastening means 91 First portion 92 Second portion 93 Third portion 94 Fourth portion 95 Fifth portion 100 Connecting piece 101- 103 Portions 104, 106 Fastening means

Claims

An adjustable stiffness system (80), the system (80) comprising: a vehicle seat (24); a structural member (34) of the vehicle seat (24), the structural member (34) having a first wall and a second wall; a connector (82) extending between the first wall and the second wall, the connector (82) having a first portion (91), a second portion (92), and a third portion (93), the second portion (92) extending between the first portion (91) and the third portion (93); a first connector (83-85) disposed between the first portion (91) of the connector (82) and the first wall of the structural member (34); and a second connector (83-85) disposed between the third portion (93) of the connector (82) and the second wall, wherein at least one of the first connector (83-85) and the second connector (83-85) is adjustable to change the tension in the second portion (92) of the connector (82) and the stiffness of the structural member (34).The system (80) of claim 1, comprising: a head restraint (30) of the vehicle seat (24) coupled to the structural member (34); and a frame (36) in the vehicle seat (24), wherein the structural member (34) comprises a portion of the frame (36).The system (80) of claim 1, wherein: the structural member (34) comprises a channel (66) forming a pocket (69), and the connector (82) is disposed in the pocket (69).The system (80) of claim 1, comprising a web (79) and a third wall, wherein: the structural member (34) has a channel (66) forming a pocket (69), the first wall comprises a first leg (70) of the channel (66), the second wall comprises the web (79), the third wall consists of a second leg (72) of the channel (66), the web (79) extends between the first leg (70) and the second leg (72) and forms a C-shape, and the connector (82) is connected to the first leg (70), to the web (79) and to the second leg (72).The system (80) of claim 1, wherein: the vehicle seat (24) includes a back (28), and the structural member (34) includes an upper cross member of the back (28).The system (80) of claim 1, comprising a head restraint (30) on the vehicle seat (24), wherein at least one of the first connector (83-85) and the second connector (83-85) is configured to adjust the stiffness to balance a response of the head restraint (30) to expected forces with a response of the head restraint (30) to restoring forces.The system (80) of claim 1, wherein the connector (82) comprises a stamping and is arranged to extend along the structural member (34).The system (80) of claim 1, wherein: the structural member (34) comprises a channel (66) configured to provide the structural member (34) with the stiffness, the structural member (34) has an angle extending from the channel (66) and configured to increase the stiffness, and the connector (82) is configured to increase the stiffness.A method of providing adjustable stiffness, the method comprising: constructing a vehicle seat (24); providing a structural member (34) in the vehicle seat (24), the structural member (34) having a first wall and a second wall; stretching a connector (82) between the first wall and the second wall, the connector (82) having a first portion (91), a second portion (92), and a third portion (93), the second portion (92) extending between the first portion (91) and the second portion (92); adding a first connector (83-85) between the first portion (91) of the connector (82) and the first wall of the structural member (34); adding a second connector (83-85) between the third portion (93) of the connector (82) and the second wall; and adjusting at least one of the first connector (83-85) and the second connector (83-85), wherein the stress in the second portion (92) of the connector (82) and the stiffness of the structural member (34) are varied.The method of claim 9, comprising: providing a head restraint (30) on the vehicle seat (24); evaluating a balance between an expected force on the head restraint (30) and a repulsive force from the head restraint (30); determining an output stiffness of the structural member (34) based on the evaluating the balance; creating a base configuration of the structural member (34) to provide the output stiffness; adjusting the output stiffness with the connector (82) to provide the varying stiffness of the structural member (34); and re-using the base configuration in different applications that require different stiffnesses provided by adjusting the output stiffness.

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