Method for producing a modal block and vehicle seat assembly

Abstract

A method (700) for manufacturing a modal block (40) for use with a vehicle seat (30) in a vehicle (10), the method comprising: Identifying (710) a frequency range of output frequencies of the vehicle (10); Determining (720) a natural frequency (51) of the vehicle seat (30); Designing (730) a modal block (40) configured to adjust the natural frequency of the vehicle seat (30); and Attaching (740) the modal block (40) between the vehicle (10) and the vehicle seat (30) to adjust the natural frequency (51) of the vehicle seat (30); wherein the modal block (40) comprises: a base (41) disposed on a lower portion of the vehicle base rail (32); a shoulder portion (43) located above the base (41) and having a surface below the seat rail (36); and an upper part (42) located within the seat rail (36); wherein the shoulder part (43) extends laterally from the base (41) and from a lower region of the upper part (42) to first stop surfaces (45); wherein upper projections (44) extend laterally outwardly from the upper part (42) to upper stop surfaces (47); wherein the modal block (40) is designed to contact the seat rail (36) at the first stop surface (45) and the upper stop surface (47) with a desired force.

Description

INTRODUCTION

[0001] The technical field relates generally to vehicle seats and, more specifically, to a modal block for adjusting the natural frequency of a vehicle seat, which also influences the amplitude and mode shape of the system in response.

[0002] Modern automobiles offer a range of features designed to enhance passenger comfort. These include adjustable seats that can be adapted to the occupants' needs, including adjustment of fore / aft position, seat height, tilt angle, lumbar support, and headrest height.

[0003] Often, the fore-and-aft position of a vehicle seat is adjusted by sliding the seat along a vehicle base rail from one fixed position to another. With such an arrangement, there is usually some clearance between the vehicle base rail and a rail connected to the vehicle seat. The vehicle seat has a natural frequency, which is a frequency or rate at which the seat naturally oscillates when disturbed. If the natural frequency of a vehicle seat matches a frequency radiated by another vehicle component, such as a component of the vehicle's internal combustion engine or the vehicle's tires, the vehicle seat may oscillate or vibrate at that frequency when the vehicle is operated.

[0004] DE 10 2013 208 003 A1 describes a longitudinal adjuster for a vehicle seat, comprising a lower rail and an upper rail guided therein for longitudinal displacement, as well as at least one bearing element arranged between the upper rail and the lower rail, which is in contact with the upper rail and the lower rail. At least one additional support element is provided, which is in contact with the upper rail and the lower rail.

[0005] JP 2016-130 056 A describes a vehicle seat support member structure that enables an improvement in the vibration absorption performance of a seat. A vibration damper is arranged between a movable rail side member and a seat body side member.

[0006] JP S54-113 198 A describes a device for attaching an object to an aircraft floor so that the object can be isolated from vibrations and distortions of the floor.

[0007] The document “MIL-STD-810H w / Change 1 2022-05-18. Environmental considerations and laboratory tests, paragraph 514.8 Annex A” describes technical information regarding various types of vibration tests.

[0008] It is desirable to provide modal blocks and methods for manufacturing modal blocks for adjusting the natural frequency of vehicle seats. Furthermore, other desirable features and characteristics of the present disclosure will become apparent from the following detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing introduction. DESCRIPTION

[0009] According to the invention, a method of manufacturing a modal block for use with a vehicle seat in a vehicle is provided. The method includes identifying a frequency range of output frequencies of the vehicle; determining a natural frequency of the vehicle seat; designing a modal block configured to adjust the natural frequency of the vehicle seat; and mounting the modal block between the vehicle and the vehicle seat to adjust the natural frequency of the vehicle seat. The modal block includes a base disposed on a lower portion of the vehicle base rail, a shoulder portion located above the base and having a surface below the seat rail, and an upper portion located within the seat rail. The shoulder portion extends laterally from the base and from a lower region of the upper portion to first stop surfaces.Upper projections extend laterally outward from the upper part to upper stop surfaces. The modal block is designed to contact the seat rail at the first stop surface and the upper stop surface with a desired force.

[0010] In certain embodiments, the method may further comprise mounting a vehicle base rail to the vehicle, and connecting the modal block between the vehicle and the vehicle seat comprises disposing the modal block between the vehicle base rail and the vehicle seat.

[0011] In certain embodiments, the method may further comprise coupling a seat rail to the vehicle seat, and connecting the modal block between the vehicle and the vehicle seat comprises disposing the modal block between the vehicle base rail and the seat rail.

[0012] In certain embodiments of the method, the seat rail is configured to slide in a longitudinal direction between fixed positions relative to the vehicle base rail, and wherein the modal block is fixed in position on the vehicle base rail.

[0013] In certain embodiments of the method, when the natural frequency is within the frequency range, the design of the modal block configured to adjust the natural frequency of the vehicle seat includes adjusting the natural frequency of the vehicle seat to a set natural frequency outside the frequency range.

[0014] In certain embodiments of the method, when the natural frequency is within the frequency range, the design of the modal block configured to adjust the natural frequency of the vehicle seat includes increasing the natural frequency of the vehicle seat to an increased natural frequency outside the frequency range.

[0015] In certain embodiments of the method, the design of the modal block configured to adjust the natural frequency of the vehicle seat includes reducing an amplitude at the natural frequency.

[0016] In certain embodiments of the method, the design of the modal block configured to adjust the natural frequency of the vehicle seat includes changing a mode shape of the vehicle seat.

[0017] According to the invention, a vehicle seat assembly is provided and includes a vehicle seat; a vehicle base rail; a seat rail attached to the vehicle seat and configured for movement relative to the vehicle base rail; and a modal block disposed between the vehicle base rail and the seat rail, the modal block configured to adjust a natural frequency of the vehicle seat assembly. The modal block includes a base disposed on a lower portion of the vehicle base rail, a shoulder portion located above the base and having a surface below the seat rail, and an upper portion located inboard of the seat rail. The shoulder portion extends laterally from the base and from a lower region of the upper portion to first stop surfaces. Upper projections extend laterally outwardly from the upper portion to upper stop surfaces.The modal block is designed to contact the seat rail at the first stop surface and the upper stop surface with a desired force.

[0018] In certain embodiments of the vehicle seat assembly, the modal block is configured to increase the natural frequency of the vehicle seat assembly to a desired set natural frequency.

[0019] In certain embodiments of the vehicle seat assembly, the modal block is configured to increase the natural frequency of the vehicle seat assembly in a longitudinal direction.

[0020] In certain embodiments of the vehicle seat assembly, the modal block is configured to increase the natural frequency of the vehicle seat assembly in a lateral direction.

[0021] In certain embodiments of the vehicle seat assembly, the modal block is configured to dampen vibrations of the vehicle seat assembly.

[0022] In certain embodiments of the vehicle seat assembly, the shoulder portion contacts the seat rail and is configured to increase the natural frequency of the vehicle seat assembly in the longitudinal direction.

[0023] In certain embodiments of the vehicle seat assembly, the upper portion is formed with outwardly extending projections that contact the seat track and are configured to increase the natural frequency of the vehicle seat assembly in a lateral direction.

[0024] In certain embodiments of the vehicle seat assembly, the modal block is fixed in position, and the vehicle seat and seat track are configured to move longitudinally to adjust a position of the vehicle seat.

[0025] In one example, a vehicle is provided that includes a vehicle body, a vehicle base rail coupled to the vehicle body, a seat rail mounted to a seat and configured for movement relative to the vehicle base rail, and a modal block disposed between the vehicle base rail and the seat rail, the modal block configured to adjust a natural frequency of the seat.

[0026] In certain embodiments of the vehicle, the modal block includes: a base disposed on a lower portion of the vehicle base rail; a shoulder portion located above the base and having a surface located below the seat rail; and an upper portion located within the seat rail.

[0027] In certain embodiments of the vehicle, the shoulder portion contacts the seat rail and is configured to increase the natural frequency of the seat in a longitudinal direction; and / or the upper portion is formed with outwardly extending projections that contact the seat rail and are configured to increase the natural frequency of the seat in a lateral direction. DESCRIPTION OF THE CHARACTERS

[0028] The present disclosure will now be described in conjunction with the following figures, wherein like numerals indicate like elements and wherein: Fig. 1 is a functional block diagram of a vehicle including a seat with a modal block according to an example; Fig. 2 is a side view of the vehicle seat, seat rail and vehicle base rail of Fig. 1, according to exemplary embodiments; Fig. 3 is an end view of the seat rail and the vehicle base rail of the Fig. 1 and Fig. 2 in engagement with a modal block according to exemplary embodiments; Fig. 4 is a sectional view of the seat rail, vehicle base rail and modal block of Fig. 3, according to exemplary embodiments; Fig. 5 and Fig. 6 are diagrams illustrating the adjustment of the natural frequency of a vehicle seat provided with different modal blocks in the transverse and longitudinal directions; and Fig. 7 is a flow diagram of a method of manufacturing a modal block for use with a vehicle seat in a vehicle. DETAILED DESCRIPTION

[0029] The following detailed description is merely exemplary and is not intended to limit the application and uses of the embodiments described herein. Furthermore, there is no intention to be bound by any express or implied theory presented in the preceding introduction, brief summary, or the following detailed description.

[0030] For the sake of brevity, conventional techniques related to signal processing, data transmission, signaling, control, and other functional aspects of the systems (and the individual operating components of the systems) are not described in detail here. Furthermore, the connecting lines depicted in the various figures are intended to represent exemplary functional relationships and / or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in an embodiment of the present disclosure.

[0031] The designs presented here are intended to improve the performance and durability of vehicle seats with respect to the output frequencies generated by the vehicle. Seat mechanisms have inherent backlash to ensure functionality and range adjustment. However, this backlash negatively impacts modal performance and can influence vibration amplitude. Backlash also affects the modal "shape," making it difficult to compensate for backlash damping.

[0032] The embodiments presented here provide for the addition of support devices, i.e., modal blocks, to the seating mechanism to control behavior or reduce play in the system. The modal block supports the components that move relative to each other to stabilize the mechanism. The modal blocks can provide additional support to improve modal behavior. The modal blocks can improve (reduce) amplitude. The modal blocks can change the "shape" of the mode. As described here, the modal blocks can be made of any material and, depending on the objective, a combination of materials. Furthermore, the modal blocks can be attached in any manner, e.g., by mechanical coupling, friction, adhesive, or other suitable means to support the features of the seating mechanism.

[0033] In Fig. 1, certain features of a vehicle 10 are illustrated in functional block diagram form. In certain examples, the vehicle 10 comprises an automobile. In various examples, the vehicle 10 may be any type of automobile, such as a sedan, station wagon, truck, or sport utility vehicle (SUV), and may have two-wheel drive (2WD) (i.e., rear-wheel drive or front-wheel drive), four-wheel drive (4WD), or all-wheel drive (AWD), and / or various other types of vehicles or mobile platforms in certain examples.

[0034] As in Fig. 1, the example vehicle 10 generally includes a body 14 and wheels 16. The body 14 substantially encloses the components of the vehicle 10. The body 14 may define an interior cabin 20 with a cabin floor 26. The wheels 16 are each rotatably connected to the vehicle 10 near a corner of the body 14.

[0035] The vehicle 10 further includes a steering wheel 24 and a vehicle seat 30 spaced longitudinally from the steering wheel 24. As indicated, vehicle base rails 32 may be secured to the cab floor 26. Further, seat rails 36 may be coupled to the seat 30 and cooperate with the vehicle base rails 32 to enable sliding engagement between the seat 30 and the cab floor 26 of the vehicle 10. As illustrated, a modal block 40 may be provided at a desired location between a vehicle base rail 32 and a seat rail 36. Depending on the desired effect, a modal block 40 may be provided on only one set of a vehicle base rail 32 and a seat rail 36 per seat 30, or on both sets of vehicle base rails 32 and seat rails 36 per seat 30. Additionally, more than one modal block 40 may be provided between a vehicle base rail 32 and a seat rail 36.The vehicle 10 may further include a motor (not shown) for adjusting the position of the seat 30 in the longitudinal direction, ie, rearward or forward between a front and a rear part of the vehicle 10.

[0036] Fig. Figure 2 illustrates the engagement and positioning of the seat 30, the seat rail 36 and the vehicle base rail 32.

[0037] As in Fig. 2, the vehicle base rail 32 extends from a front end 33 to a rear end 34. Furthermore, the seat rail 36 extends from a front end 37 to a rear end 38. The seat 30 and the seat rail 36 can move in a forward direction 21 to the front end 33 or in a rearward direction 22 to the rear end 34.

[0038] The modal block 40 is in the view of Fig. 2 hidden.

[0039] Fig. 3 is an end view showing a modal block 40 disposed between a vehicle base rail 32 and a seat rail 36, such as the vehicle base rail 32 and the seat rail 36 of Fig. 2. Fig. 4 is a sectional view of the modal block 40, the vehicle base rail 32 and the seat rail 36. Fig. 3 and Fig. 4 are taken along a longitudinal axis, with the left side direction 28 and the right side direction 29 perpendicular to the front direction 21 and rear direction 22 of Fig. 2 run.

[0040] As in the Fig. 3 and Fig. 4, the modal block includes a base portion 41 and an upper portion 42. In certain embodiments, a bottom surface of the base portion 41 may be secured to the base rail 32. In certain embodiments, the base portion 41 and the upper portion 42 may be integrally formed, i.e., one-piece. In certain embodiments, the base portion 41 and the upper portion 42 are separately formed and secured to one another. The base portion 41 and the upper portion 42 may be made of the same material or different materials. Furthermore, the material of the base portion 41 and the upper portion 42 may be selected to provide a desired degree of rigidity or flexibility.

[0041] As shown, the base part 41 is located at a height below the seat rail 36. The upper part 42 of the modal block 40 extends upward from the base part 41 and is located in a recess 39 between opposite sides of the seat rail 36.

[0042] Shoulder portions or lower projections 43 extend laterally from the base portion 41 and from a lower portion of the upper portion 42 to first stop surfaces 45. As illustrated, each first stop surface 45 has a horizontal component, meaning it is not vertical. In other words, each first stop surface 45 may be horizontal or diagonal. Furthermore, the lower projections 43 may extend laterally outwardly from the lower portion of the upper portion 42 to second stop surfaces 46. As illustrated, the second stop surfaces 46 may be vertical.

[0043] The upper projections 44 extend laterally outwardly from the upper part 42 to the upper stop surfaces 47. As shown, the upper stop surfaces 47 may be vertical.

[0044] As previously mentioned, the modal block 40 can be attached to the vehicle base rail 32. For example, the modal block 40 can be pressed into the vehicle base rail 32 and held in place by friction, glued to the vehicle base rail 32, mechanically coupled to the vehicle base rail 32, or attached to the vehicle base rail 32 in another suitable manner.

[0045] The modal block 40 is designed and shaped to contact the seat rail 36 at the first stop surface 45 and the upper stop surface 47 with a desired force.

[0046] Thereby, the rigidity of the seat 30 can be increased, ie the clearance between the seat 30 and the vehicle base rail 32 can be reduced.

[0047] More specifically, the stiffness of the seat 30 in the lateral direction 28 / 29 can be increased by exerting a greater radially outward force from the upper abutment surfaces 47 onto the seat rail 36. The stiffness of the seat 30 in the transverse direction 28 / 29 can be minimized by separating the upper part 42 of the modal block 40 from the seat rail 36. In other words, the upper part 42 must not touch the seat rail 36, thereby maximizing the clearance therebetween.

[0048] The rigidity of the seat 30 can be increased in the longitudinal direction 21 / 22 by exerting a larger, vertically upward force from the first stop surfaces 45 onto the seat rail 36.

[0049] Additionally, the modal block 40 can be designed and constructed to reduce the amplitude of the vibration of the seat 30 at a specific frequency, i.e., the modal block can dampen the vibration of the seat 30. The damping effect can be optimized by the choice of material for the modal block 40 as well as the shape of the modal block 40. For example, a more flexible material can provide greater damping than a rigid material. Furthermore, a modal block 40 designed to apply a selected force from a flexible material to the seat rail 36 can provide increased damping. To optimize damping and stiffness, the modal block 40 can be made of a more flexible material on at least one engagement surface and a stiffer material on another engagement surface.

[0050] In addition to adjusting the stiffness and / or damping through the structure of the modal block 40, the position of the modal block 40 and / or an arrangement of several modal blocks 40 for a single seat 30 can also be used to achieve the desired stiffness and / or damping in the transverse and longitudinal directions. While in Fig. For example, while Figure 1 shows a single modal block 40 near the rear end 34 of the vehicle base rail 32, the modal block 40 could also be positioned near the front end 33. Furthermore, multiple modal blocks 40 could be mounted on the vehicle base rail 32. Even when multiple modal blocks 40 are used, the design and construction of the individual modal blocks 40 can vary.

[0051] For example, one modal block 40 may have increased stiffness in the longitudinal direction, while another modal block 40 may have increased stiffness in the transverse direction. Likewise, one modal block 40 may dampen the amplitude by the desired amount, while another modal block 40 does not dampen the amplitude. While in certain embodiments, the modal block(s) 40 on the vehicle base rail 32 on the left side of the seat 30 may be arranged in the same manner as on the vehicle base rail 32 on the right side of the seat 30, in other embodiments, the two vehicle base rails 32 may be provided with modal blocks 40 of different structures or different arrangements of the modal blocks 40.

[0052] Fig. 5 is a diagram showing the frequency (X-axis in Hertz) and the oscillation amplitude (Y-axis is defined by the acceleration (dB ref. 1M / s 2) for a vehicle seat 30 in the lateral direction when provided with no modal block (50), with a modal block with a flexible base part and a rigid upper part (60) of one construction and shape, and with a modal block with a rigid base part and a rigid upper part (70) of the same construction and shape.

[0053] As shown, the vehicle seat 30 without the modal block (50) has a natural frequency 51 in the lateral direction of 18.70 Hz. When equipped with the modal block with a flexible base part and a rigid upper part, the vehicle seat 30 has an adjusted natural frequency 61 in the lateral direction of 19.38 Hz. When equipped with the modal block with a rigid base part and a rigid upper part, the vehicle seat 30 has an adjusted natural frequency 71 in the lateral direction of 19.54 Hz.

[0054] Fig. 6 is a diagram showing the frequency (X-axis in Hertz) and the oscillation amplitude (Y-axis is defined by the acceleration (dB ref. 1M / s 2 ) in the longitudinal direction for the same arrangement of vehicle seat 30 and modal block 40 from Fig. 5 shows, i.e. no modal block (50), a modal block with a flexible base part and a rigid upper part (60) of a specific construction and shape and a modal block with a rigid base part and a rigid upper part (70) of the same construction and shape. As shown, the vehicle seat 30 without the modal block (50) has a natural frequency 52 in the longitudinal direction of 17.49 Hz. When equipped with the modal block with a flexible base part and a rigid upper part (60), the vehicle seat 30 has an adjusted natural frequency 62 in the longitudinal direction of 17.83 Hz. When equipped with the modal block with a rigid base part and a rigid upper part (70), the vehicle seat 30 has an adjusted natural frequency 72 in the longitudinal direction of 17.93 Hz.

[0055] Thus, the natural frequency of a vehicle seat 30 in the transverse and longitudinal directions can be adjusted to a selected frequency through design, structure, shape and material selection.

[0056] Fig.7 shows a method 700 for manufacturing a modal block 40 for use with a vehicle seat 30. The method 700 includes, at operation 710, identifying a frequency range of vehicle output frequencies. For example, the operation of a vehicle may be observed and various output frequencies recorded. The output frequencies may originate from an engine, e.g., an internal combustion engine, from the tires contacting the road surface, or from other vehicle components. Alternatively, a processor may model expected output frequencies based on inputs related to a particular vehicle model.The processor may use or include any hardware, software, firmware, electronic control unit or component, processing logic, and / or processor unit, individually or in any combination, including, but not limited to: application-specific integrated circuits (ASICs), electronic circuits, a processor (collectively, dedicated, or as a group) and memory executing one or more software or firmware programs, combinational logic circuitry, and / or other suitable components that provide the described functionality. Furthermore, the processor may be implemented by any number of hardware, software, and / or firmware components configured to perform the specified functions. For example, an embodiment of the processor may use various integrated circuit components, e.g.,Memory elements, digital signal processing elements, logic elements, lookup tables, or similar that can perform a variety of functions.

[0057] Method 700 may continue with operation 720, where a natural frequency of the vehicle seat 30 is determined. For example, the processor may model a vehicle seat having a seat track, a vehicle base track, and a seat mechanism. In certain embodiments, method 700 includes mounting a vehicle base track to the vehicle and coupling a seat track to the vehicle seat such that the determination of the natural frequency of the vehicle seat 30 is based, in part, on the play of the seat track within the vehicle base track.

[0058] The method 700 includes, in operation 730, designing a modal block configured to adjust the natural frequency of the vehicle seat. For example, in certain embodiments, the natural frequency of the vehicle seat is within the frequency range of the vehicle's output frequencies. In such cases, the modal block is designed by the processor to adjust the natural frequency of the vehicle seat to an adjusted natural frequency outside the frequency range. For example, the modal block may be designed to raise the natural frequency of the vehicle seat to an elevated natural frequency that is greater than the frequency range. Alternatively or additionally, the modal block may be designed to reduce the vibration amplitude of the vehicle seat at the natural frequency and / or at the adjusted natural frequency. Additionally, the modal block may be designed to change the mode shape of the vehicle seat.

[0059] Method 700 may continue at operation 740 with attaching the modal block between the vehicle and the vehicle seat to adjust the natural frequency of the vehicle seat. For example, the modal block (or blocks) may be attached to the vehicle base rail between the vehicle base rail and the seat rail to allow longitudinal movement of the seat rail relative to the modal block and the vehicle base rail when a user adjusts the position of the vehicle seat.

[0060] Although at least one exemplary embodiment has been presented in the foregoing detailed description, it should be understood that numerous variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are merely examples and are not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the foregoing detailed description is intended to provide one skilled in the art with a convenient guide for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes in the function and arrangement of elements may be made without departing from the scope of the disclosure as set forth in the appended claims and their legal equivalents.

Claims

[1] A method (700) for manufacturing a modal block (40) for use with a vehicle seat (30) in a vehicle (10), the method comprising: Identifying (710) a frequency range of output frequencies of the vehicle (10); Determining (720) a natural frequency (51) of the vehicle seat (30); Designing (730) a modal block (40) configured to adjust the natural frequency of the vehicle seat (30); and Attaching (740) the modal block (40) between the vehicle (10) and the vehicle seat (30) to adjust the natural frequency (51) of the vehicle seat (30); wherein the modal block (40) comprises: a base (41) disposed on a lower portion of the vehicle base rail (32); a shoulder portion (43) located above the base (41) and having a surface below the seat rail (36); and an upper part (42) located within the seat rail (36); wherein the shoulder part (43) extends laterally from the base (41) and from a lower region of the upper part (42) to first stop surfaces (45); wherein upper projections (44) extend laterally outwardly from the upper part (42) to upper stop surfaces (47); wherein the modal block (40) is designed to contact the seat rail (36) at the first stop surface (45) and the upper stop surface (47) with a desired force. [2] The method of claim 1, further comprising: Attaching a vehicle base rail (32) to the vehicle (10), wherein connecting the modal block (40) between the vehicle (10) and the vehicle seat (30) comprises arranging the modal block (40) between the vehicle base rail (32) and the vehicle seat (30); and Coupling a seat rail (36) to the vehicle seat (30), wherein connecting the modal block (40) between the vehicle (10) and the vehicle seat (30) comprises disposing the modal block (40) between the vehicle base rail (32) and the seat rail (36), wherein the seat rail (36) is configured to slide in a longitudinal direction between fixed positions with respect to the vehicle base rail (32), and wherein the modal block (40) is fixed in position on the vehicle base rail (32). [3] The method of claim 1, wherein, when the natural frequency (51) is within the frequency range, the design of the modal block (40) configured to adjust the natural frequency (51) of the vehicle seat (30) comprises increasing the natural frequency (51) of the vehicle seat (30) to an increased natural frequency outside the frequency range. [4] The method of claim 1, wherein the design of the modal block (40) configured to adjust the natural frequency (51) of the vehicle seat (30) comprises reducing an amplitude at the natural frequency (51). [5] The method of claim 1, wherein the design of the modal block (40) configured to adjust the natural frequency (51) of the vehicle seat (30) comprises changing a mode shape of the vehicle seat (30). [6] A vehicle seating arrangement comprising: a vehicle seat (30); a vehicle base rail (32); a seat rail (36) attached to the vehicle seat (30) and configured for movement relative to the vehicle base rail (32); and a modal block (40) disposed between the vehicle base rail (32) and the seat rail (36), the modal block (40) configured to adjust a natural frequency (51) of the vehicle seat assembly; wherein the modal block (40) comprises: a base (41) disposed on a lower portion of the vehicle base rail (32); a shoulder portion (43) located above the base (41) and having a surface below the seat rail (36); and an upper part (42) located within the seat rail (36); wherein the shoulder part (43) extends laterally from the base (41) and from a lower region of the upper part (42) to first stop surfaces (45); wherein upper projections (44) extend laterally outwardly from the upper part (42) to upper stop surfaces (47); wherein the modal block (40) is designed to contact the seat rail (36) at the first stop surface (45) and the upper stop surface (47) with a desired force. [7] The vehicle seat assembly of claim 6, wherein the modal block (40) is configured to increase the natural frequency (51) of the vehicle seat assembly to a desired set natural frequency. [8] The vehicle seat assembly of claim 6, wherein the modal block (40) is configured to increase the natural frequency (51) of the vehicle seat assembly in a longitudinal direction and / or a transverse direction. [9] The vehicle seat assembly of claim 6, wherein the modal block (40) is configured to dampen the vibrations of the vehicle seat assembly.

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