Seat load sensor

Abstract

To provide a technique for preventing exposure of a load sensor for a seat from a seat surface.SOLUTION: This description discloses a load sensor for a seat that detects a load acting on a seat surface. The load sensor for the seat may include: a force receiving portion that is placed on the seat surface, and receives the load acting on the seat surface; and a detection unit that is disposed on the force receiving portion across a seat cloth constituting the seat surface, and detects the load received by the force receiving portion.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a load sensor for a seat that detects a load acting on a seat surface. [Background technology]

[0002] There is known a technology for detecting the load acting on the seat surface from a passenger seated in a seat of a moving body such as an automobile. For example, a sensor such as a mobile floor reaction force measuring device described in Cited Document 1 is used as a seat load sensor for detecting the load. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-158404 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a moving body such as an automobile, the seats on which passengers sit are made of a flexible fabric to improve seating comfort. Therefore, if the relatively rigid parts or wiring of the sensor are exposed from the seat surface, the seating comfort may be reduced and the appearance may be deteriorated. This may have a negative effect on the commercial value of the seat or the product in which the seat is installed.

[0005] This specification provides a technique for suppressing exposure of a seat load sensor from a seat surface. [Means for solving the problem]

[0006] This specification discloses a seat load sensor that detects a load acting on a seat surface. The seat load sensor may include a force receiving part that is placed on the seat surface and receives the load acting on the seat surface, and a detection part that is disposed in front of the force receiving part across a seat fabric that constitutes the seat surface and detects the load received by the force receiving part.

[0007] According to the above configuration, the force receiving portion is exposed from the seat surface, while the detection portion is not exposed from the seat surface. This makes it possible to reduce exposure of the seat load sensor and the wiring extending from the sensor. In the above configuration, the detection portion detects the load received by the force receiving portion by converting it into a measurable physical quantity such as a displacement, a resistance change, or a voltage change. This allows the detection portion to properly detect the load without being exposed from the seat surface.

[0008] The force receiving portion may be displaced upon receiving the load, and the detection portion may detect the load received by the force receiving portion using the displacement of the force receiving portion. With this configuration, the detection portion can detect the load received by the force receiving portion by measuring the displacement of the force receiving portion.

[0009] The force receiving portion may have a shape that is plane-symmetrical with respect to a plane perpendicular to a first direction along the sheet surface, thereby making it possible to equalize the detection performance for a load when the force receiving portion receives a load in one direction along the first direction and when the force receiving portion receives a load in the other direction along the first direction.

[0010] The force receiving portion may have a shape that is perpendicular to the first direction and plane-symmetrical with respect to a plane perpendicular to a second direction along the sheet surface. With this configuration, similar to the case where a load is received along the first direction, the force receiving portion can have the same detection performance for a load when the force receiving portion receives a load in one direction along the second direction and when the force receiving portion receives a load in the other direction along the second direction.

[0011] The force receiving portion may have a partially spherical shape. With this configuration, it is possible to prevent the detection performance for a load from varying depending on the direction of the load.

[0012] The force receiving portion may have a shape such that a displacement caused by a load in a first direction along the sheet surface is larger than a displacement caused by a load in a second direction perpendicular to the first direction and along the sheet surface. With this configuration, a load in the first direction can be selectively detected.

[0013] The detection unit may include a pressure-sensitive conductive elastomer arranged along the displacement direction of the force receiving unit. With this configuration, the displacement of the force receiving unit can be detected by identifying the resistance value of the pressure-sensitive conductive elastomer that varies due to the expansion and contraction of the pressure-sensitive conductive elastomer.

[0014] The seat cushion may further include a rigid member disposed between the detection unit and the seat fabric, the rigid member having a higher rigidity than the seat fabric. With this configuration, the displacement of the force receiving unit can be appropriately transmitted to the detection unit.

[0015] This specification further discloses a load sensor system including any one of the seat load sensors described above. The load sensor system may include a plurality of seat load sensors, each of which is any one of the seat load sensors described above, arranged side by side in a first direction along a seat surface, and a control unit connected to the plurality of seat load sensors and capable of selectively acquiring detection results of one or more of the plurality of seat load sensors.

[0016] According to this configuration, it is possible to obtain detection results from each of the multiple load sensors individually, and thus it is possible to appropriately identify what type of load is being applied to what position on the seat surface. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a plan view showing a part of a seat surface in the first embodiment. [Diagram 2] 1 is a schematic vertical sectional view of a load sensor according to a first embodiment of the present invention; [Diagram 3] FIG. 4 is a plan view of a displacement portion of the first embodiment. [Figure 4] FIG. 4 is a bottom view of the displacement portion of the first embodiment. [Diagram 5] 3 is a vertical sectional view showing a state in which the load sensor of the first embodiment is displaced under a load. FIG. [Figure 6] FIG. 11 is a schematic vertical sectional view of a load sensor according to a second embodiment. [Figure 7] FIG. 11 is a plan view showing a part of a seat surface on which a load sensor of a third embodiment is arranged. [Figure 8] FIG. 13 is a schematic elevational sectional view of a load sensor according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] (First embodiment) A load sensor system 2 of a first embodiment will be described with reference to Figs. 1 to 5. As shown in Fig. 1, the load sensor system 2 includes a plurality of load sensors 10 and a control unit 80. The load sensors 10 are attached to the seat surface (i.e., the seat surface) of a seat of an automobile or the like, and detect the load applied to the seat surface by a passenger. As shown in Fig. 1, in a plan view of the seat surface (i.e., when viewed from above), the plurality of load sensors 10 are arranged at equal intervals in each of the X direction (i.e., the vehicle width direction) and the Y direction (i.e., the vehicle front-rear direction) of Fig. 1 along the seat surface. Note that, although only one load sensor 10 is indicated by a reference number in Fig. 1, the plurality of load sensors 10 have the same shape and function.

[0019] As shown in Figures 2 and 3, the load sensor 10 includes a force receiving portion 12, a detection portion 18, a rigid member 40, and a substrate 42. The force receiving portion 12 is exposed upward (i.e., in the direction toward the passenger) from a seat fabric 100 that constitutes the seat surface. Note that in Figure 2, the force receiving portion 12 is not shown in cross section, but in a side view. The same is true for Figures 5, 6, and 8. The seat fabric 100 is made of materials used for automobile seats, such as leather and cloth. The force receiving portion 12 is fixed to the seat fabric 100. The force receiving portion 12 has a hemispherical shape. Therefore, the force receiving portion 12 is not axially aligned with the seat fabric 100, and the force receiving portion 12 is not axially aligned with the seat fabric 100. YZ The force receiving portion 12 is plane-symmetrical with respect to the plane and plane-symmetrical with respect to the XZ plane. The lower surface of the force receiving portion 12, i.e., the surface that contacts the seat fabric 100, has a planar shape. The force receiving portion 12 is made of, for example, a resin or the like that has a rigidity that does not deform even when a passenger sits on the seat surface.

[0020] A rigid member 40 is disposed below the force receiving portion 12 with the seat fabric 100 sandwiched therebetween. The rigid member 40 has a flat plate shape. The rigid member 40 has approximately the same dimensions as the lower surface of the force receiving portion 12. The rigid member 40 faces the entire surface of the lower surface of the force receiving portion 12 with the seat fabric 100 sandwiched therebetween. The rigid member 40 is made of an insulating material that is more rigid than the seat fabric 100 and has a rigidity that does not deflect due to the load of the occupant.

[0021] The detection unit 18 is attached to the lower surface of the rigid member 40. The detection unit 18 includes a plurality of (four in this embodiment) displacement units 30, 32, 34, 36 and a support unit 44. The displacement units 30, 32, 34, 36 are made of a pressure-sensitive conductive elastomer. The pressure-sensitive conductive elastomer is a material in which conductive particles such as carbon and metal powder are uniformly mixed into a highly insulating rubber material. The displacement units 30, 32, 34, 36 change their resistance values ​​as they deform.

[0022] The displacement portions 30, 32, 34, 36 have a cylindrical shape. The displacement portions 30, 32 are disposed adjacent to each other in the X direction. The displacement portions 30, 32 are disposed at an interval. The displacement portions 30, 32 are disposed symmetrically with respect to the YZ plane passing through the apex of the force receiving portion 12. As shown in FIG. 3, the displacement portions 34, 36 are disposed adjacent to each other in the Y direction. The displacement portions 34, 36 are disposed at an interval. The displacement portions 34, 36 are disposed symmetrically with respect to the XZ plane passing through the apex of the force receiving portion 12.

[0023] The displacement sections 30, 32, 34, and 36 are supported by a support section 44. The support section 44 has a cylindrical shape with a plurality of openings for arranging the displacement sections 30, 32, 34, and 36. The diameter of the support section 44 is the same as the diameter of the lower surface of the force receiving section 12. The support section 44 is made of a material having a lower rigidity than the displacement sections 30, 32, 34, and 36 and having insulating properties that do not contain conductive particles. The support section 44 may be made of a material having the same rigidity as the displacement sections 30, 32, 34, and 36.

[0024] A substrate 42 is disposed on the lower surface of the detection unit 18. The substrate 42 has a flat plate shape with higher rigidity than the displacement units 30, 32, 34, and 36. Electrical wiring connected to the displacement units 30, 32, 34, and 36 is arranged on the substrate 42. A plurality of load sensors 10 are disposed on the substrate 42.

[0025] Although not shown in the figure, the seat is filled with a sponge material below the seat fabric 100. Therefore, the rigid member 40, the detection unit 18, and the substrate 42, which are arranged below the seat fabric 100, are surrounded by the sponge material.

[0026] (Load detection method by the load sensor 10) Next, a method of detecting a load by the load sensor 10 will be described with reference to Figures 1, 3, and 4. As shown in Figure 3, the displacement units 30, 32 arranged side by side in the X direction are connected in series by a wiring 50. Similarly, the displacement units 34, 36 arranged side by side in the Y direction are connected in series by a wiring 52. As shown in Figure 4, the displacement units 30, 32 are connected to a power source (e.g., a vehicle battery) 102 by wirings 50a, 50b. Similarly, the displacement units 34, 36 are connected to a power source (e.g., a vehicle battery) 102 by wirings 52a, 52b.

[0027] In the above configuration, as shown in FIG. 5, when the force receiving section 12 receives a load in the X direction, one of the displacement sections 32 located in the direction in which the load is applied is compressed, and the other displacement section 30 is stretched. As a result, the resistance values ​​of the displacement sections 30 and 32 change. This causes the voltage of the wiring 50 between the displacement sections 30 and 32 to change. When the force receiving section 12 is aligned in the X direction and receives a load in the opposite direction to the load direction in FIG. 5, the displacement section 30 is compressed and the displacement section 32 is stretched. As a result, a difference occurs in the resistance values ​​of the displacement sections 30 and 32, and the voltage of the wiring 50 between the displacement sections 30 and 32 changes. Similarly, when the force receiving section 12 receives a load in the Y direction, the displacement sections 34 and 36 are deformed, causing a difference in the resistance values ​​of the displacement sections 34 and 36, and the voltage of the wiring 52 changes.

[0028] In addition, when the force receiving portion 12 receives a load in the Z direction, the displacement portions 30, 32, 34, and 36 are compressed or stretched in the same manner. As a result, the resistance values ​​of the displacement portions 30 and 32 change in the same manner. Therefore, no difference occurs between the resistance values ​​of the displacement portions 30 and 32. Therefore, the voltage of the wiring 50 does not change. On the other hand, the resistance values ​​of the displacement portions 30 and 32 change, so that the current values ​​of the wirings 50, 50a, and 50b change. Similarly, the current values ​​of the wirings 52, 52a, and 52b change due to the change in the resistance values ​​of the displacement portions 34 and 36. With this configuration, it is possible to detect how the force receiving portion 12 is displaced, that is, the magnitude and direction of the load received by the force receiving portion 12, by detecting the voltage value of the wirings 50 and 52, the current value of any of the wirings 50, 50a, and 50b, and the current value of any of the wirings 52, 52a, and 52b. With this configuration, it is possible to detect loads in the three directions of X, Y, and Z by using the load sensor 10.

[0029] (Wiring of load sensor system 2) Next, the wiring of the load sensor system 2 will be described. As shown in Fig. 1, the multiple load sensors 10 aligned in the X direction are connected to a common power supply wiring 20, a ground wiring 22, an X-direction output wiring 24, a Y-direction output wiring 26, and a common select signal wiring 28. That is, the power supply wiring 20, the ground wiring 22, the X-direction output wiring 24, the Y-direction output wiring 26, and the common select signal wiring 28 are arranged in the same number as the number of the load sensors 10 aligned in the Y direction.

[0030] The power supply wiring 20 electrically connects the power supply 102 to the wirings 50a and 52a. The ground wiring 22 grounds the wirings 50b and 52b. The X-direction output wiring 24 is a wiring for outputting the voltage value of the wiring 50 and the current value of any of the wirings 50, 50a, and 50b in order to detect the displacement of the force receiving unit 12 in the X direction. The Y-direction output wiring 26 is a wiring for outputting the voltage value of the wiring 52 and the current value of any of the wirings 52, 52a, and 52b in order to detect the displacement of the force receiving unit 12 in the Y direction. The common select signal wiring 28 will be described later.

[0031] The load sensors 10 arranged in the Y direction are connected to a shared X-direction select signal wiring 14 and a Y-direction select signal wiring 16. That is, the X-direction select signal wiring 14 and the Y-direction select signal wiring 16 are arranged in the same number as the number of the load sensors 10 arranged in the X direction. The X-direction select signal wiring 14 and the Y-direction select signal wiring 16 are controlled by the control unit 80 together with the common select signal wiring 28.

[0032] The control unit 80 is included in a control device that controls components (e.g., an engine) other than the load sensor system 2 mounted on the vehicle, such as an ECU of the vehicle. In a modified example, the control unit 80 may be arranged exclusively for the load sensor system 2. The control unit 80 includes a CPU, a memory, and the like. The control unit 80 stores a computer program for controlling the load sensor system 2. The control unit 80 is connected to each of the X-direction output wiring 24, the Y-direction output wiring 26, the X-direction select signal wiring 14, the Y-direction select signal wiring 16, and the common select signal wiring 28. The control unit 80 switches each of the X-direction select signal wiring 14, the Y-direction select signal wiring 16, and the common select signal wiring 28 between on and off. The X-direction select signal wiring 14, the Y-direction select signal wiring 16, and the common select signal wiring 28 are maintained in the off state until they are switched to the control unit.

[0033] The control unit 80 switches the X-direction select signal wiring 14, the Y-direction select signal wiring 16, and the common select signal wiring 28 on and off according to a computer program stored in the control unit 80. First, the control unit 80 switches one or more of the common select signal wirings 28 arranged in the X direction from off to on. Next, the control unit 80 switches one or more of the select signal wirings of the multiple X-direction select signal wirings 14 and the multiple Y-direction select signal wirings 16 from off to on. As a result, the control unit 80 acquires, from at least one of the X-direction output wiring 24 and the Y-direction output wiring 26, the current value and the voltage value output from one or more load sensors 10 connected to the common select signal wiring 28 switched on among the multiple load sensors 10, and at least one select signal wiring switched on among the X-direction select signal wiring 14 and the Y-direction select signal wiring 16.

[0034] The control unit 80 stores in advance at least one of a database and a formula for calculating the load from the current value and the voltage value output from the load sensor 10. The database and the formula are created in advance based on the results of experiments or simulations and stored in the control unit 80. The control unit 80 identifies the load applied to the load sensor 10 using the acquired current value and voltage value and at least one of the database and the formula. With this configuration, it is possible to individually acquire detection results from each of the multiple load sensors 10. This makes it possible to appropriately identify which position on the seat surface and in which direction the load is applied.

[0035] In the above load sensor 10, the force receiving portion 12 is exposed from the seat surface, while the detection portion 18 is not exposed from the seat surface. This makes it possible to reduce the exposure of the load sensor 10. In some cases, a seat is designed to sink when a passenger sits on it, taking into consideration seating comfort. In the above configuration, the detection portion 18 detects the vertical displacement of the force receiving portion 12. This allows the detection portion 18 to properly detect the load, even if the detection portion 18 is not exposed from the seat surface.

[0036] The force receiving section 12 has a hemispherical shape. This allows the force receiving section 12 to behave in accordance with a load in one direction along the X direction and in the other direction along the X direction. This allows the displacement of the force receiving section 12 when a load of a specific magnitude in one direction along the X direction is received and the displacement of the force receiving section 12 when a load of a specific magnitude in the other direction along the X direction is received to be uniform. Similarly, the displacement of the force receiving section 12 can be made uniform even when a load is applied along the Y direction. In addition, it is possible to avoid a situation in which the displacement of the force receiving section 12 is significantly different between the load in the X direction and the load in the Y direction. This allows the ranges of the voltage value and the current value output from the load sensor 10 to be suppressed from fluctuating significantly between the load in the X direction and the load in the Y direction.

[0037] The displacement portions 30, 32, 34, and 36 are made of a pressure-sensitive conductive elastomer. With this configuration, the displacement of the force-receiving portion 12 can be detected by identifying the resistance value of the pressure-sensitive conductive elastomer that varies with the expansion and contraction of the pressure-sensitive conductive elastomer.

[0038] Moreover, the load sensor 10 is disposed between the detection unit 18 and the seat fabric 100, and includes a rigid member 40 having a higher rigidity than the seat fabric 100. With this configuration, the displacement of the force receiving unit 12 can be appropriately transmitted to the detection unit 18.

[0039] (Second Example) The difference from the first embodiment will be described with reference to FIG. 6. In the load sensor 10 of the second embodiment, a support portion 44 having a lower rigidity than the displacement portions 30, 32, 34, 36 is arranged between the displacement portions 30, 32, 34, 36 and the seat fabric 100 instead of the rigid member 40. As a result, a gap CL is arranged between the seat fabric 100 and the displacement portions 30, 32, 34, 36. In this configuration, a minute displacement of the load sensor 10 causes the support portion 44 to deform, while the displacement portions 30, 32, 34, 36 are not deformed. This makes it possible to avoid detecting a minute load applied to the force receiving portion 12. In a modified example, the rigid member 40 may be arranged between the support portion 44 and the seat fabric 100.

[0040] (Third Example) Differences from the first embodiment will be described with reference to FIG. 7. The load sensor 10 of the third embodiment differs from the force receiving portion 12 in the configuration of the force receiving portion 112. The force receiving portion 112 has a semi-cylindrical shape extending in the X direction. The length of the force receiving portion 112 in the X direction is sufficiently longer than the length in the Y direction. In this configuration, the force receiving portion 112 is X While it is displaced greatly by the load in the direction, Y For the direction X The amount of displacement is small compared to the direction. X In this case, the load sensor 10 may include the displacement portions 30 and 32 aligned in the X direction, but may not include the displacement portions 34 and 36 aligned in the Y direction.

[0041] (Fourth Example) Differences from the first embodiment will be described with reference to FIG. 8. In the load sensor 10 of the fourth embodiment, the shape of the displacement portions 230, 232 is different from the shape of the displacement portions 30, 32 of the first embodiment. The displacement portions 230, 232 are arranged at an incline with respect to the Z direction. With this configuration, the displacement portions 230, 232 can be arranged along the direction of the load of the force receiving portion 12. This makes it possible to prevent the displacement portions 230, 232 from buckling due to the displacement of the force receiving portion 12. The displacement portions 34, 36 may also have a similar configuration.

[0042] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples exemplified above.

[0043] For example, the load sensor 10 of the first embodiment does not need to have the displacement parts aligned in either one of the displacement parts 30, 32 aligned in the X direction and the displacement parts 34, 36 aligned in the Y direction. The same applies to the second and fourth embodiments.

[0044] Furthermore, for example, instead of the displacement sections 30, 32, 34, 36, the detection section 18 may be provided with a load-bearing section in which a quantitatively measurable physical quantity, such as a current value, a voltage value, or a resistance value, changes depending on the load received by the force-receiving section 12.

[0045] The technical elements described in this specification or drawings have technical utility either alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful. [Explanation of symbols]

[0046] 2: Load sensor system 10: Load sensor 12: Force receiving part 14: X-direction select signal wiring 16: Y-direction select signal wiring 18: Detection unit 20: Power wiring 22: Ground wiring 24: X-direction output wiring 26: Y-direction output wiring 28: Common select signal wiring 30, 32, 34, 36: Displacement section 40: Rigid member 42: Substrate 80: Control section 100: Seat fabric

Claims

1. A seat load sensor that detects a load acting on a seat surface, a force receiving portion that is placed on the seat surface and receives the load acting on the seat surface; a detection unit disposed across the seat fabric constituting the seat surface from the force receiving unit and configured to detect the load received by the force receiving unit, The force receiving portion is The sheet has a shape that is plane-symmetrical with respect to a plane perpendicular to a first direction along the sheet surface, The sheet has a shape that is perpendicular to the first direction and is symmetrical with respect to a plane perpendicular to a second direction along the sheet surface, It has a partial spherical shape, The force receiving portion is displaced by receiving the load, The detection portion detects a load applied to the force receiving portion by using a displacement of the force receiving portion.

2. A seat load sensor that detects a load acting on a seat surface, a force receiving portion that is placed on the seat surface and receives the load acting on the seat surface; a detection unit disposed across the seat fabric constituting the seat surface from the force receiving unit and configured to detect the load received by the force receiving unit, the force receiving portion has a shape such that a displacement caused by a load in a first direction along the sheet surface is larger than a displacement caused by a load in a second direction perpendicular to the first direction and along the sheet surface, The force receiving portion has a semi-cylindrical shape extending in the first direction.

3. The seat load sensor according to claim 1 , wherein the detection portion comprises a pressure-sensitive conductive elastomer that expands and contracts in a vertical direction.

4. The detection unit includes a pair of pressure-sensitive conductive elastomers each of which expands and contracts in a vertical direction and is disposed adjacent to each other with a gap therebetween, 3. The load sensor for a seat according to claim 1, wherein the pair of pressure-sensitive conductive elastomers are disposed at an incline with respect to the up-down direction so that a distance between their upper ends is smaller than a distance between their lower ends.

5. The seat load sensor according to claim 1 , further comprising a rigid member disposed between the detection portion and the seat fabric, the rigid member having a rigidity higher than that of the seat fabric.

6. The seat load sensor according to claim 1 , further comprising a support member disposed between the detection portion and the seat fabric, the support member having a lower rigidity than the detection portion.

7. a plurality of seat load sensors, each of which is the seat load sensor according to any one of claims 1 to 6, the plurality of seat load sensors being arranged side by side in a first direction along a seat surface; a control unit connected to the plurality of seat load sensors and capable of selectively acquiring detection results of one or more of the plurality of seat load sensors.

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