Steering wheel with built-in detection sensor

Abstract

To provide a detection sensor built-in type steering wheel capable of accomplishing an excellent detection precision.SOLUTION: A detection sensor built-in type steering wheel includes a rim 1R building a detection sensor 12 therein. The rim 1R includes: a metal core 10; an internal-side resin layer 11 formed so as to cover the metal core 10; an external-side resin layer 13 formed at the external side of the internal-side resin layer 11; and a sheet-shape detection sensor 12 placed between the internal-side resin layer 11 and the external-side resin layer 13. Electrode density of the detection sensor 12 changes in a circumferential direction in a cross section orthogonal to an extending direction of the rim 1R in accordance with thickness of the external-side resin layer 13.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a steering wheel with an integrated detection sensor. [Background technology]

[0002] In recent years, a heater has been incorporated into the rim of a steering wheel, and a grip sensor has been incorporated to detect whether or not the driver is gripping the steering wheel for automated driving of level 2 or higher. Patent Document 1 below discloses a steering wheel with a heater and a grip sensor incorporated into the rim. The grip sensor is also called a HoD sensor (Hands On / Off Detection sensor). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2015-502282 Summary of the Invention [Problem to be solved by the invention]

[0004] When a detection sensor such as an HoD sensor is incorporated into a steering wheel rim, a sensor mat is attached to the surface of a resin layer that is the internal structure of the rim, and then a skin material such as leather is attached on top of that. In the above-mentioned Patent Document 1, a heater is also provided between the resin layer and the sensor mat. The skin material has a substantially constant thickness and is the outermost layer of the rim. Since the thickness of the skin material is constant, if the sensitivity of the sensor mat is uniform over the entire area, the detection sensitivity on the rim surface, i.e., on the surface of the skin material, will also be uniform.

[0005] Steering wheels with a skin material on the outermost layer are expensive, and it is desirable to apply detection sensors to steering wheels without a skin material. Steering wheels without a skin material are often used in low-priced vehicles. In this case, the detection sensor is embedded inside the resin layer. However, due to various factors, it is difficult to make the thickness of the resin layer outside the detection sensor uniform, and if the sensitivity of the detection sensor itself is uniform, the detection sensitivity on the rim surface will not be uniform, which will cause problems in detection accuracy.

[0006] An object of the present disclosure is to provide a steering wheel with an integrated detection sensor that can achieve good detection accuracy. [Means for solving the problem]

[0007] The steering wheel with integrated detection sensor according to the present disclosure includes a rim with the detection sensor integrated therein, the rim having a core wire, an inner resin layer formed to cover the core wire, an outer resin layer formed on the outside of the inner resin layer, and a sheet-shaped detection sensor arranged between the inner resin layer and the outer resin layer, and the electrode density of the detection sensor is changed in the circumferential direction in a cross section perpendicular to the extension direction of the rim depending on the thickness of the outer resin layer. Effect of the Invention

[0008] According to the steering wheel with an integrated detection sensor of the present disclosure, good detection accuracy can be achieved. [Brief description of the drawings]

[0009] [Figure 1] 1 is a partially sectional perspective view of a detection sensor-embedded steering wheel according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a cross-sectional view of a rim of the steering wheel. [Diagram 3] FIG. 4 is a partial development view of a sensor mat constituting the detection sensor. [Figure 4]FIG. 4 is a development view showing a punching pattern in the sensor mat. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] A steering wheel 1 according to an embodiment will now be described with reference to Figures 1 to 4. A detection sensor 12 is incorporated inside a rim 1R of the steering wheel 1.

[0011] As shown in FIG. 1, the steering wheel 1 has an annular rim 1R and spokes 1S. The spokes 1S connect the rim 1R to a metal boss plate (not shown) that has a boss attached to the end of the shaft of a steering column. A center pad 1P that also functions as a horn button is attached to the front side (the side facing the driver) of the boss plate. The center pad 1P also serves as a driver's airbag module. The back side of the boss plate is covered with a resin cover. An operation panel with various switches is attached to the front side of each of the left and right spokes 1S (details of the operation panel are not shown).

[0012] FIG. 1 also shows the internal structure of the rim 1R. FIG. 2 shows a cross section of the rim 1R. The cross section in FIG. 2 is perpendicular to the extension direction of the rim 1R (the annular circumferential direction of the annular rim 1R). A metal core 10 is disposed in the center of the rim 1R. A core is also disposed inside the spoke 1S, and the core inside the spoke 1S connects the core 10 of the rim 1R to the boss plate. The strength and rigidity of the steering wheel 1 are mainly ensured by the core (10) and the boss plate. In this embodiment, the core 10 of the rim 1R has a U-shaped cross section. The core 10 is covered with an inner resin layer 11. The inner resin layer 11 is specifically a urethane foam layer. With the core 10 inserted into a mold, the inner resin layer 11 is foam injection molded.

[0013] An outer resin layer 13 is formed on the outside of the inner resin layer 11, and a detection sensor 12 is disposed between the inner resin layer 11 and the outer resin layer 13. Specifically, the outer resin layer 13 is also a urethane foam layer. The detection sensor 12 of this embodiment is a sheet-like sensor mat of a capacitance type HoD sensor. The detection sensor 12 is attached to the surface of the inner resin layer 11, and the outer resin layer 13 is foam injection molded with the steering wheel in this intermediate state inserted into a mold. The outer resin layer 13 is the outermost layer of the steering wheel 1, and may have a thin layer, such as a coating layer, on its surface to improve the appearance and feel.

[0014] As will be explained in detail later, a number of punch holes 12h (see FIG. 4) are formed in the detection sensor 12, and the inner resin layer 11 and the outer resin layer 13 are directly bonded to each other through the punch holes 12h. Since the inner resin layer 11 and the outer resin layer 13 are directly bonded to each other, the outer resin layer 13 is prevented from shifting relative to the inner resin layer 11 at the detection sensor 12 as a boundary, i.e., from peeling off. The detection sensor 12 may be provided not only on the rim 1R but also extending to the spokes 1S.

[0015] As shown in FIG. 2, the cross section of the rim 1R is rarely a perfect circle, and is often an ellipse as shown in FIG. 2 for ease of grip. Also, the ellipse is not a precise cross section, and the curvature of the outer circumference side and the inner circumference side of the rim 1R often differs. In many cases, as shown in FIG. 2, the cross section of the rim 1R is an ellipse with a smaller curvature on the front side and the back side of the steering wheel 1. Also, a depression called a thumb grip for the thumb is often formed on the upper side of the connection with the horizontal spoke 1S. Therefore, depending on the annular circumferential position of the rim 1R, the cross section may be a rounded triangular shape. That is, the cross section of the rim 1R may change depending on the annular circumferential position of the rim 1R.

[0016] The cross-sectional shape shown in FIG. 2 is mainly formed by injection molding of the inner resin layer 11 and the outer resin layer 13, but considering the shape of the steering wheel 1, the parting lines PL of the injection molding die are located at the outer and inner peripheries of the rim 1R. At this time, the thickness of the outer resin layer 13 usually changes in the circumferential direction of the cross section. In the cross section shown in FIG. 2, the thickness is thin in region A and thick in region C. Between these regions A and C, a region B of intermediate thickness is formed. Depending on the thickness of the outer resin layer 13 in these regions A to C, the detection sensitivity of the detection sensor 12, i.e., the electrode density, changes in the circumferential direction of the cross section of FIG. 2.

[0017] FIG. 3 shows a development of the sheet-like detection sensor 12. FIG. 3 shows only a part of the section where the rim 1R has a uniform cross section. The left-right direction of FIG. 3 is the annular circumferential direction of the rim 1R. As shown in FIG. 3, the detection sensor 12 has an electrode 12a corresponding to the region A in FIG. 2, an electrode 12b corresponding to the region B, and an electrode 12c corresponding to the region C. The electrodes 12a to 12c are conductive cloth or metal thin films. The detection sensor 12 is wound around the inner resin layer 11 in the circumferential direction of the cross section in FIG. 2, but the joint is located on the inner circumferential side of the rim 1R. That is, the center of the central electrode 12a shown in FIG. 3 corresponds to the parting line PL on the outer circumferential side of the rim 1R in FIG. 2.

[0018] Therefore, as shown in FIG. 3, the electrode 12a arranged on the inner circumference side of the annular rim 1R is divided into two parts on both edges of the sheet-like detection sensor 12, and the detection sensor 12 is wound around the inner resin layer 11 to form one electrode 12a on the inner circumference side of the rim 1R. A margin 12m is also formed on one of the divided electrodes 12a, which is overlapped with the other electrode 12a when wound. When detecting the driver's grip, the detection frequency is higher on the outer circumference side of the rim 1R than on the inner circumference side, so the seam is arranged on the inner circumference side rather than the outer circumference side. In addition, if there is a seam, there is a high possibility that sink marks will occur on the surface of the outer resin layer 13 that is injection molded on the detection sensor 12, or voids will occur inside the outer resin layer 13. Since the outer circumference side is more noticeable than the inner circumference side, the seam is arranged on the inner circumference side rather than the outer circumference side in consideration of the appearance of the steering wheel 1.

[0019] As described above, the cross-sectional shape of the rim 1R changes along the annular circumferential direction of the rim 1R. To accommodate such shape changes of the rim 1R, it is necessary to accommodate them by adjusting the shape (i.e., thickness) of the inner resin layer 11 and the outer resin layer 13. For this reason, it is difficult to make the thickness of the outer resin layer 13 uniform throughout the entire detection target area, and the thickness of the outer resin layer 13 is changed depending on the position.

[0020] If the thickness of the outer resin layer 13 is made thin and uniform, the resin fluidity during injection molding of the outer resin layer 13 deteriorates, making molding defects more likely to occur. Poor molding of the outer resin layer 13 deteriorates the appearance of the steering wheel 1. Furthermore, if the outer resin layer 13 is made thin, the outer resin layer 13 is more likely to peel off. On the other hand, if the thickness of the outer resin layer 13 is made thick and uniform, the volume of the inner resin layer 11 is reduced accordingly, so that the outer peripheral surface of the inner resin layer 11 comes closer to the core metal 10, and the resin fluidity during injection molding of the inner resin layer 11 deteriorates, making molding defects more likely to occur. Furthermore, if the outer resin layer 13 is thick, the sensitivity of the detection sensor 12 decreases.

[0021] Therefore, in this embodiment, the electrode density of the detection sensor 12 is changed according to the thickness of the outer resin layer 13 so that the detection sensitivity of the detection sensor 12 is uniform in the detection target area while allowing the thickness of the outer resin layer 13 to change. In this embodiment, the electrode density of the detection sensor 12 is changed in the cross-sectional circumferential direction shown in FIG. 2 and also in the annular circumferential direction of the rim 1R. However, it is sufficient that the electrode density of the detection sensor 12 is changed at least in the cross-sectional circumferential direction according to the thickness of the outer resin layer 13. That is, the electrode density of the detection sensor 12 is changed in the regions A to C in FIG. 2. Of course, it is preferable that the electrode density is changed in the annular circumferential direction of the rim 1R in addition to the cross-sectional circumferential direction according to the thickness of the outer resin layer 13.

[0022] The electrode density of the detection sensor 12 will be described with reference to FIG. 4. In this embodiment, the electrode density of the detection sensor 12 is changed by the punch holes 12h formed in the detection sensor 12. If the number of punch holes 12h formed in the electrodes 12a to 12c of the detection sensor 12 is increased, the area of ​​the electrodes 12a to 12c themselves can be reduced. In other words, the amount of metal (conductive material) in the electrodes 12a to 12c is adjusted depending on the number of punch holes 12h. The electrode density of the detection sensor 12 is the ratio of the area occupied by the electrodes 12a to 12c to the area of ​​the detection target area. The formation density of the punch holes 12h is the ratio of the area occupied by the punch holes 12h to the area of ​​the detection target area. In other words, if the formation density of the punch holes 12h is high, the electrode density of the detection sensor 12 is low.

[0023] 2, the thickness of the outer resin layer 13 is thin in region A, and the thickness of the outer resin layer 13 is thick in region C. Therefore, to make the detection sensitivity of the detection sensor 12 uniform in the detection target area, the sensitivity of the detection sensor 12 in region A, i.e., the sensitivity of the electrode 12a, can be reduced, and the sensitivity in region C, i.e., the sensitivity of the electrode 12c, can be increased. The sensitivity of the electrode 12b in region B is set between the sensitivity of the electrode 12a and the sensitivity of the electrode 12c.

[0024] Therefore, as shown in Fig. 4(a), many punch holes 12h are formed in the electrode 12a to reduce the electrode density. That is, the formation density of the punch holes 12h in the electrode 12a is made high. On the other hand, as shown in Fig. 4(c), few punch holes 12h are formed in the electrode 12c to increase the electrode density. That is, the formation density of the punch holes 12h in the electrode 12c is made low. As for the electrode 12b, as shown in Fig. 4(b), the formation density of the punch holes 12h is set so that the electrode density is intermediate between the electrode density of the electrode 12a and the electrode density of the electrode 12c.

[0025] By setting the electrode density of the electrodes 12a to 12c, i.e., the formation density of the punch holes 12h, in this manner, it is possible to make the detection sensitivity of the detection sensor 12 uniform in the detection target area, and to achieve good detection accuracy. In this embodiment, the formation density of the punch holes 12h is changed by changing the formation density of the punch holes 12h. Specifically, the formation density of the punch holes 12h is changed by changing the number of punch holes 12h of the same shape per unit area. However, the formation density of the punch holes 12h may also be changed by changing the size of the punch holes 12h.

[0026] As described above, it is preferable that the electrode density of the detection sensor 12 is changed not only in the cross-sectional circumferential direction of the rim 1R but also along the annular circumferential direction of the rim 1R according to the thickness of the outer resin layer 13. For example, in the thumb grip that is the above-mentioned recess, the thickness of the outer resin layer 13 is thin. On the other hand, the upper side of the thumb grip is formed as a protrusion, so the thickness of the outer resin layer 13 is thick. The electrode density of the detection sensor 12 may be changed along the annular circumferential direction of the rim 1R according to such a change in the thickness of the outer resin layer 13 in the annular circumferential direction of the rim 1R. Specifically, in this embodiment, the electrode density of the detection sensor 12 is changed according to the formation density of the punch holes 12h.

[0027] According to the above embodiment, the rim 1R has a core metal 10, an inner resin layer 11 formed to cover the core metal 10, an outer resin layer 13 formed on the outside of the inner resin layer 11, and a sheet-like detection sensor 12 arranged between the inner resin layer 11 and the outer resin layer 13. The electrode density of the detection sensor 12 is changed in the circumferential direction (cross-sectional circumferential direction) in a cross section perpendicular to the extension direction (annular circumferential direction) of the rim 1R according to the thickness of the outer resin layer 13. This makes it possible to make the detection sensitivity of the detection sensor 12 with respect to the outer surface of the steering wheel 1 uniform. That is, according to the above embodiment, good detection accuracy can be achieved.

[0028] Here, it is particularly preferable that the electrode density is high in the region where the thickness of the outer resin layer 13 is thick and low in the region where the thickness of the outer resin layer 13 is thin. In this way, the detection sensitivity of the detection sensor 12 to the outer surface of the steering wheel 1 can be made uniform, and good detection accuracy can be achieved.

[0029] Also, it is preferable that the electrode density is changed by the formation density of the punch holes 12h formed in the sheet-like detection sensor 12. In this way, uniformity of the detection sensitivity of the detection sensor 12 to the outer surface of the steering wheel 1 can be achieved with a simple structure, particularly with a simple structure of forming the punch holes 12h in the sheet-like detection sensor 12. Also, since the inner resin layer 11 and the outer resin layer 13 are directly bonded through the punch holes 12h, the strength of the rim 1R against twisting is improved and peeling of the outer resin layer 13 is suppressed.

[0030] It is also preferable that the formation density of the punch holes 12h is low in an area where the outer resin layer 13 is thick and high in an area where the outer resin layer 13 is thin. That is, the formation density of the punch holes 12h, i.e., the electrode density of the detection sensor 12, can be adjusted by the formation pattern of the punch holes 12h, and the detection sensor 12 with adjusted detection sensitivity can be easily formed.

[0031] The present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, the steering wheel 1 is described that does not have a skin material such as leather. However, the detection sensor 12 may be embedded in the resin layer (the inner resin layer 11 and the outer resin layer 13) of the rim 1R as described above, and a skin material may be further provided. Since the skin material has a substantially uniform thickness, good detection accuracy can be achieved even in a steering wheel having such a structure. Also, in the above embodiment, the detection sensor 12 is a HoD sensor. However, the detection sensor 12 can also be used as a sensor that detects a switch operation of some device. For example, the detection sensor 12 may be used as a HoD sensor as a whole, and a part of it may be used to detect a switch operation of some device.

[0032] In the above embodiment, the electrode density (the formation density of the punch holes 12h) is changed stepwise in each of the regions A to C, but the electrode density may be changed continuously in accordance with the gradual change in the thickness of the outer resin layer 13. In the above embodiment, the electrode density is changed according to the punch holes 12h, but the electrode density may be changed by bonding conductive mesh members with different opening ratios together. In this case, it is necessary to ensure the conductivity between the mesh members to be bonded together. [Explanation of symbols]

[0033] 1 Steering wheel 1R Rim 1S spoke 1P Center Pad 10 Core wire 11 Inner resin layer 12 Detection sensor 12a~12c electrode 13 Outer resin layer

Claims

1. A detection sensor built-in steering wheel, The detection sensor is incorporated in a rim, the rim has a core metal, an inner resin layer formed so as to cover the core metal, an outer resin layer formed on the outside of the inner resin layer, and a sheet-like detection sensor disposed between the inner resin layer and the outer resin layer, A steering wheel, wherein an electrode density of the detection sensor is changed in a circumferential direction in a cross section perpendicular to an extension direction of the rim according to a thickness of the outer resin layer.

2. 2. The steering wheel according to claim 1, wherein the electrode density is high in an area where the outer resin layer has a large thickness and low in an area where the outer resin layer has a small thickness.

3. 3. The steering wheel according to claim 1, wherein the electrode density is changed by changing a formation density of punch holes formed in the sheet-shaped detection sensor.

4. 4. The steering wheel according to claim 3, wherein a formation density of the punch holes is low in an area where the outer resin layer is thick and is high in an area where the outer resin layer is thin.

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