Patent Description:
When a driver drives a vehicle such as an automobile, the driver can change the driving direction of the vehicle by turning a steering wheel while holding the steering wheel. The steering wheel is also referred to as a driving wheel.

Further embodiments of the invention result from the dependent claims and the corresponding description. Such a steering wheel may include a sensor device configured to detect whether a driver is holding the steering wheel. Specifically, an electrode (such as a capacitive sensor), configured to detect whether a driver is holding the rim of the steering wheel, may be provided inside the rim of the steering wheel. In addition, a heater may also be provided inside the rim of the steering wheel such that the driver does not feel cold when the driver's hand contacts or is placed in proximity to the steering wheel. However, if the heater is provided inside the rim of the steering wheel, the detection accuracy of the sensor device may be decreased due to external influences such as an electromagnetic field formed around the heater and a change in detection sensitivity associated with a temperature change.

In view of the above, it is desirable to provide a sensor device that can detect whether a person's hand contacts or is in proximity to a steering wheel with high accuracy.

According to an aspect of an embodiment, a capacitive sensor device for use with a steering wheel is provided. The steering wheel includes a rim and a spoke that is connected to the inner side of the rim, and the sensor device is provided on the spoke. The sensor device includes an electrode configured to be capacitively coupleable to an object to be detected, and includes a controller configured to detect a change in capacitance of the electrode, and determine whether the object is in proximity to the rim based on the change in the capacitance of the electrode. The change in the capacitance occurs in response to the object being in proximity to the rim. As an illustrative example, the controller may be configured to determine whether the object is in proximity to the spoke based on the change in the capacitance of the electrode. The change in the capacitance may occur in response to the object being in proximity to the spoke.

According to the present disclosure, a sensor device can detect, with high accuracy, whether a person's hand contacts or is in proximity to a rim or a spoke of a steering wheel in conditions in which a capacitive sensor is unable to be provided inside the rim.

In the following, embodiments of the present invention will be described. The same elements are denoted by the same reference numerals, and the description of the same elements will not be repeated.

First, related-art steering wheels will be described with reference to <FIG>. As illustrated in <FIG>, a steering wheel used in a vehicle typically includes an annular rim <NUM> and a spoke <NUM>. The spoke <NUM> is connected to the inner side of the rim <NUM> and is also connected to a steering column (not illustrated). Typically, when a driver drives a vehicle, the driver operates or turns the steering wheel while holding the rim <NUM> with the hands. In the automobile market, self-driving vehicles have been introduced in recent years. However, because a self-driving function is considered to be a driving support function, even if a vehicle has a self-driving function, the driver is still required by law to place their hands on the steering wheel while driving. In light of this, it is preferable for self-driving vehicles to have a function to determine whether a driver's hand is placed at a position where the driver can immediately operate the steering wheel, and alert the driver in response to determining that the driver's hand is not placed at a position where the driver can immediately operate the steering wheel. For example, a steering wheel including a capacitive sensor inside a rim <NUM> is devised so as to determine whether one or both of a driver's hands are holding the steering wheel.

Further, vehicles may be used in cold regions. In such a case, if a steering wheel is excessively colder than the body temperature of a driver, the driver would feel cold when the driver contacts the steering wheel with the hands. As a result, it may be difficult for the driver to touch the steering wheel for a long period of time, and the driver's driving may be hindered. For this reason, the steering wheel may include a heater inside a rim <NUM> so as to heat and warm the rim <NUM> of the steering wheel while the driver is driving the vehicle. Examples of the heater include a heating element that generates heat by causing a current to flow through a heating wire or the like. The heating element is an element that generates heat through the resistance, and may be formed of a metallic material, such as nichrome, having a relatively high resistance.

Accordingly, in the above case, the steering wheel may include both the heater and the sensor, such as a capacitive sensor, inside the rim <NUM>. If the heater is provided inside the rim <NUM> of the steering wheel, the heater is preferably provided in a part of the rim <NUM> that is likely to be held by the driver, which may be different from person to person. Similarly, if the sensor such as a capacitive sensor is provided inside the rim <NUM> of the steering wheel, the sensor is preferably provided in a part of the rim <NUM> that is likely to be held by the driver, which may be different from person to person.

In view of the above, both the heater and the sensor such as a capacitive sensor may be disposed around the circumference of the rim <NUM>, and one of the heater and the sensor is disposed inward relative to the other. Specific examples will be described with reference to a cross-sectional view of a steering wheel in which a heater is provided around a capacitive sensor as illustrated in <FIG>, and a cross-sectional view of a steering wheel in which a capacitive sensor is provided around a heater as illustrated in <FIG>.

For example, in the steering wheel as illustrated in <FIG>, a capacitive sensor <NUM> is provided around a core metal <NUM> that forms the center portion of a rim <NUM> of the steering wheel. A heater <NUM> is provided around the capacitive sensor <NUM>, and an outer skin <NUM> is provided around the heater <NUM>. With this configuration, when a driver's hand contacts or is in proximity to the rim <NUM> of the steering wheel, the capacitance of the capacitive sensor <NUM> changes. A controller (not illustrated) that is electrically connected to the capacitive sensor <NUM> detects the amount of change in the capacitance, generates a detection signal, and determines whether the driver's hand contacts or is in proximity to the rim <NUM> of the steering wheel by comparing the detection signal to a predetermined threshold. However, in the example illustrated in <FIG>, the heater <NUM> composed of a resistor made of an electrically conductive metal is disposed adjacent to the capacitive sensor <NUM>. Typically, the electrically conductive metal has a large capacitance, and thus, the heater has a large capacitance. Therefore, as compared to when there is no influence of the heater <NUM>, if the heater <NUM> is disposed adjacent to the capacitive sensor <NUM>, a change in the capacitance of the capacitive sensor <NUM> would be affected by the heater <NUM>. As a result, the magnitude of a detection signal generated by the controller based on the change in the capacitance of the capacitive sensor <NUM> would change due to the influence of the heater <NUM>, thus causing the controller to fail to make an accurate determination. Further, a temperature change may cause a change in the capacitance of the capacitive sensor <NUM>. Therefore, if heat from the heater <NUM> warms the capacitive sensor <NUM>, the magnitude of a detection signal, generated by the controller based on a change in the capacitance of the capacitive sensor <NUM>, would change before and after the capacitive sensor <NUM> is warmed. Therefore, the controller would be unable to make an accurate determination based on the detection signal.

Further, in the steering wheel as illustrated in <FIG>, a heater <NUM> is provided around a core metal <NUM> that forms the center portion of a rim <NUM> of the steering wheel. A capacitive sensor <NUM> is provided around the heater <NUM>, and an outer skin <NUM> is provided around the capacitive sensor <NUM>. With this configuration, heat generated by the heater <NUM> warms the outer skin <NUM> via the capacitive sensor <NUM>, and is transferred to the driver's hands. Thus, as compared to the configuration illustrated in <FIG>, it would take time to warm the rim <NUM>, and power consumed by the heater <NUM> would also increase.

Further, similar to the configuration illustrated in <FIG>, in the configuration illustrated in <FIG>, the electrically conductive heater <NUM> is disposed adjacent to the capacitive sensor <NUM>. Therefore, the magnitude of a detection signal, generated based on a change in the capacitance of the capacitive sensor <NUM>, would become unstable, thus making it difficult for the controller to make an accurate determination based on the detection signal. Further, similar to the configuration illustrated in <FIG>, in the configuration illustrated in <FIG>, if heat generated by the heater <NUM> warms the capacitive sensor <NUM>, the magnitude of a detection signal, generated based on a change in the capacitance of the capacitive sensor <NUM>, would change before and after the capacitive sensor <NUM> is warmed. Therefore, it would be difficult for the controller to make an accurate determination based on the detection signal.

As described above, if the capacitive sensor <NUM> is provided inside the rim <NUM> in the steering wheel, it may be difficult to accurately determine whether the driver's hand contacts the steering wheel.

Next, a steering wheel sensor <NUM> (corresponding to a "sensor device" recited in the claims) according to a first embodiment and a steering wheel <NUM> (corresponding to a "steering wheel" recited in the claims) will be described with reference to <FIG>. As illustrated in <FIG>, the steering wheel <NUM> according to the first embodiment includes a rim <NUM>, a spoke <NUM>, and a steering wheel sensor <NUM> provided on the spoke <NUM>. The spoke <NUM> is connected to the inner side of the rim <NUM> and is also connected to a steering column (not illustrated). The steering wheel sensor <NUM> includes a capacitive sensor <NUM> (corresponding to an "electrode" recited in the claims) and a controller <NUM> (corresponding to a "controller" recited in the claims). The capacitive sensor <NUM> can be capacitively coupled to an object (hereinafter referred to as an "operation body") to be detected and having a capacitance. In the first embodiment, the capacitive sensor <NUM> is provided along edge portions 121a, 121b, and 121c, facing the inner peripheral surface of the rim <NUM>, of the spoke <NUM>. A heater <NUM> configured to heat and warm the rim <NUM> is provided inside the rim <NUM>. That is, the capacitive sensor <NUM> and the heater <NUM> are provided at different positions of the steering wheel <NUM>.

As illustrated in <FIG>, the controller <NUM> is electrically connected to the capacitive sensor <NUM>.

In the first embodiment, the controller <NUM> generates a detection signal based on a change in the capacitance of the capacitive sensor <NUM>, and further performs a coding process on the detection signal so as to facilitate the transmission of the detection signal. The controller <NUM> communicates with an external device illustrated in <FIG> and transmits the detection signal to the external device. The external device determines whether a driver's hand is placed at a position where the driver can immediately operate the steering wheel by comparing the detection signal to a predetermined threshold, and alerts the driver if the driver's hand is not placed at a position where the driver can immediately operate the steering wheel.

Note that the controller <NUM> may determine whether the driver's hand is placed at a position where the driver can immediately operate the steering wheel.

Accordingly, in the steering wheel <NUM>, because the capacitive sensor <NUM> is provided away from the heater <NUM>, the possibility that a change in the capacitance of the capacitive sensor <NUM> is affected by the capacitance of the heater <NUM> is virtually eliminated. Further, the possibility that a detection signal, generated by the controller <NUM> based on the change in the capacitance of the capacitive sensor <NUM>, is affected by the capacitance of the heater <NUM> is virtually eliminated. Further, because the possibility that heat from the heater <NUM> is transferred to the capacitive sensor <NUM> is virtually eliminated, the controller <NUM> can accurately detect whether the driver's hand contacts or is in proximity to the steering wheel without being affected by the heater <NUM>. Further, the heater <NUM> can efficiently warn the rim <NUM> without being affected by the heat capacity of the capacitive sensor <NUM>.

Note that, while the controller <NUM> can detect whether the operation body having a capacitance, such as the driver's hand, contacts or is in proximity to the steering wheel based on a change in the capacitance of the capacitive sensor <NUM>, the value of the capacitance of the capacitive sensor <NUM> depends on the distance between the capacitive sensor <NUM> and the operation body to be detected. As the operation body approaches the capacitive sensor <NUM>, the value of the capacitance of the capacitive sensor <NUM> increases, and as the operation body moves away from the capacitive sensor <NUM>, the value of the capacitance of the capacitive sensor <NUM> decreases. By utilizing the above, the controller <NUM> can adjust a detection area by adjusting a threshold or by using a plurality of thresholds to be compared to a detection signal generated based on a change in the capacitance of the capacitive sensor <NUM>. For example, as illustrated in <FIG>, even if the operation body is located in an area furthest from the rim <NUM>, the controller <NUM> can determine whether the operation body is in proximity to the rim <NUM> based on a change in the capacitance of a portion (such as 130a or 130b) of the capacitive sensor <NUM>. Specifically, as illustrated in <FIG>, the controller <NUM> can determine whether the operation body is located in any of detection areas 150a, 150b, and 150c, which are set in the surroundings of the rim <NUM> and between the rim <NUM> and the edge portions 121a, 121b, and 121c, facing the inner peripheral surface of the rim <NUM>, of the spoke <NUM>.

In the first embodiment, the capacitive sensor <NUM> is included in the steering wheel sensor <NUM>. The driver side of the steering wheel sensor <NUM> is covered by an exterior panel <NUM> illustrated in <FIG>. The capacitive sensor <NUM> is formed of an electrical conductor such as one line-shaped conductive wire, and is provided along the edge portions of the spoke <NUM>. As illustrated in <FIG>, the detection areas 150a, 150b, and 150c extend along a plane that includes the rim <NUM>.

Further, the above-described rim <NUM> and the spoke <NUM> are connected by connecting portions. Specifically, as illustrated in <FIG>, connecting portions 120a, 120b, and 120c connect the spoke <NUM> to the inner side of the rim <NUM>. A space is formed between the rim <NUM> and a part, extending from the connecting portion 120a to the connecting portion 120b, of the spoke <NUM>. Similarly, a space is formed between the rim <NUM> and a part, extending from the connecting portion 120a to the connecting portion 120c, of the spoke <NUM>. Similarly, a space is formed between the rim <NUM> and a part, extending from the connecting portion 120b to the connecting portion 120c, of the spoke <NUM>.

The capacitive sensor <NUM> of the steering wheel sensor <NUM> includes a sensor portion 130a (corresponding to a "fragment" recited in the claims). The sensor portion 130a is provided along the edge portion 121a, facing the rim <NUM>, of the spoke <NUM>. The capacitive sensor <NUM> further includes a sensor portion 130b (corresponding to a "fragment" recited in the claims) provided along the edge portion 121b, facing the rim <NUM>, of the spoke <NUM>. The capacitive sensor <NUM> further includes sensor portions 130c and 130d (corresponding to "fragments" recited in the claims). The sensor portions 130c and 130d are provided along parts of the edge portion 121c, facing the rim <NUM>, of the spoke <NUM>. The capacitive sensor <NUM> further includes a sensor portion 130e (corresponding to a "fragment" recited in the claims) and a sensor portion 130f (corresponding to a "fragment" recited in the claims). The sensor portion 130e is provided along the connecting portion 120a, connecting the spoke <NUM> to the rim <NUM>, and the sensor portion 130f is provided along the connecting portion 120b.

As described above, the sensor portion 130e (corresponding to a "fragment" recited in the claims) of the capacitive sensor <NUM> is provided along the connecting portion 120a, connecting the spoke <NUM> to the rim <NUM>, the sensor portion 130f (corresponding to a "fragment" recited in the claims) of the capacitive sensor <NUM> is provided along the connecting portion 120b, and a sensor portion <NUM> (corresponding to a "fragment" recited in the claims) of the capacitive sensor <NUM> is provided along the connecting portion 120c.

As illustrated in <FIG>, the capacitive sensor <NUM> is formed of one conductive wire. The capacitive sensor <NUM> includes the sensor portion 130c, the sensor portion 130f, the sensor portion 130a, the sensor portion 130e, the sensor portion 130b, the sensor portion <NUM>, and the sensor portion 130d, which are connected in this order. In the first embodiment, the capacitive sensor <NUM> may be formed of two conductive wires. For example, the capacitive sensor <NUM> may be formed of a conductive wire that includes a part of the sensor portion 130e, the sensor portion 130a, the sensor portion 130f, the sensor portion 130c, and formed of a conductive wire that includes the other part of the sensor portion 130e, the sensor portion 130b, the sensor portion <NUM>, and the sensor portion 130d.

That is, the outer periphery of the spoke <NUM> includes the edge portions (121a and 121b) and the connecting portions (120a, 120b, and 120c), and the capacitive sensor <NUM> extends continuously along the outer periphery of the spoke <NUM>.

In a configuration according to the first embodiment, it is assumed that the driver mainly holds lower portions 110a and 110b of the rim <NUM> while the driver is driving the vehicle. For example, when the lower portion 110a of the rim <NUM> is held by the driver, the driver's hand is placed in proximity to the sensor portion 130a of the capacitive sensor <NUM> and within the detection area 150a, thus allowing the driver's hand to be detected. Further, when the lower portion 110b of the rim <NUM> is held by the driver, the driver's hand is placed in proximity to the sensor portion 130b of the capacitive sensor <NUM> and within the detection area 150b, thus allowing the driver's hand to be detected.

Further, while the driver is driving the vehicle, the driver's hand may contact a connecting portion between the spoke <NUM> and the rim <NUM> or contact the vicinity of the connecting portion. For example, if the driver's hand contacts the connecting portion 120a of the spoke <NUM> or contacts the vicinity of the connecting portion 120a, the driver's hand is in proximity to the sensor portion 130e of the capacitive sensor <NUM> and within the detection area 150a or the detection area 150b, thus allowing the driver's hand to be detected by the controller <NUM>. Further, if the driver's hand, approaching the sensor portion 130e of the capacitive sensor <NUM>, is placed in proximity to the connecting portion 120a side of the sensor portion 130a or the connecting portion 120a side of the sensor portion 130b, the driver's hand enters the detection area 150a or the detection area 150b, thus allowing the driver's hand to be detected by the controller <NUM>.

Further, if the driver's hand contacts the connecting portion 120b of the spoke <NUM> or contacts the vicinity of the connecting portion 120b, the driver's hand is placed in proximity to the sensor portion 130f or the sensor portion 130c and within the detection area 150c, thus allowing the driver's hand to be detected by the controller <NUM>. If the driver's hand contacts the connecting portion 120c of the spoke <NUM> or contacts the vicinity of the connecting portion 120c, the driver's hand is placed in proximity to the sensor portion <NUM> or the sensor portion 130d and within the detection area 150d, thus allowing the controller <NUM> to detect the driver's hand.

In the following, a steering wheel sensor and a steering wheel according to a second embodiment will be described with reference to <FIG> and <FIG>. In the second embodiment, the same elements as those of the first embodiment are denoted by the same reference numerals.

In a configuration according to the second embodiment, it is assumed that the drive mainly holds an upper portion 110c of the annular rim <NUM> illustrated in <FIG> while the driver is driving the vehicle.

In the second embodiment, as illustrated in <FIG>, the steering wheel <NUM> includes the annular rim <NUM>, the spoke <NUM> that is connected to the inner side of the rim <NUM>, and the steering wheel sensor <NUM> that is provided on the spoke <NUM>. The connecting portions 120a, 120b, and 120c connect the spoke <NUM> to the rim <NUM>.

The steering wheel sensor <NUM> includes the capacitive sensor <NUM> (corresponding to the "electrode" recited in the claims). The capacitive sensor <NUM> is provided along the edge portions, facing the inner peripheral surface of the rim <NUM>, of the spoke <NUM>, and can be capacitively coupled to an object ("operation body") to be detected and having a capacitance. Further, the steering wheel sensor <NUM> includes a capacitive sensor <NUM> (corresponding to the "electrode" recited in the claims). The capacitive sensor <NUM> is provided along the edge portion, facing the inner peripheral surface of the rim <NUM>, of the spoke <NUM>, and can be capacitively coupled to the operation body having a capacitance. Further, the steering wheel sensor <NUM> includes the controller <NUM> that is electrically connected to the capacitive sensor <NUM> and to the capacitive sensor <NUM>.

The capacitive sensor <NUM> includes the sensor portions 130a and 130b (corresponding to the "fragments" recited in the claims). The sensor portions 130a and 130b are provided along the lower edge portions 121a and 121b, facing the inner peripheral surface of the rim <NUM>, of the spoke <NUM>. The capacitive sensor <NUM> further includes the sensor portion 130c (corresponding to the "fragment" recited in the claims) and the sensor portion 130d (corresponding to the "fragment" recited in the claims). The sensor portion 130c and the sensor portion 130d are provided along parts of the upper edge portion 121c of the spoke <NUM>. The sensor portion 130c is located closer to the connecting portion 120b, and the sensor portion 130d is located closer to the connecting portion 120c.

The capacitive sensor <NUM> is formed of one conductive wire. The capacitive sensor <NUM> includes the sensor portion 130c, the sensor portion 130f, the sensor portion 130a, the sensor portion 130e, the sensor portion 130b, the sensor portion <NUM>, and the sensor portion 130d, which are connected in this order. The sensor portions of the capacitive sensor <NUM> have different electrical resistance values based on the distances from the rim <NUM>.

The capacitive sensor <NUM> is provided along a part of the upper edge portion 121c, facing the inner peripheral surface of the rim <NUM>. Further, the capacitive sensor <NUM> is located at a position where the sensor portion 130c and the sensor portion 130d of the capacitive sensor <NUM> are not provided.

In the second embodiment, the capacitive sensor <NUM> is provided along the part of the upper edge portion 121c so as not to overlap the capacitive sensor <NUM>. However, the capacitive sensor <NUM> may be provided so as to overlap the capacitive sensor <NUM> to the extent that misdetection does not occur.

As illustrated in <FIG>, the capacitive sensor <NUM> and the capacitive sensor <NUM> are connected in parallel to the controller <NUM>.

The capacitive sensor <NUM> has an electrical resistance value different from those of the capacitive sensor <NUM>. As illustrated in <FIG>, the capacitive sensor <NUM> is provided along the part of the upper edge portion 121c of the spoke <NUM>, and is located away from the connecting portion 120b and the connecting portion 120c. In other words, the capacitive sensor <NUM> is provided along the center part of the upper edge portion 121c of the spoke <NUM>. If the spoke <NUM> has a typical shape, such as a T-shape, the distance between the capacitive sensor <NUM> and the rim <NUM> is greater than the distance between the capacitive sensor <NUM> and the rim <NUM>. Therefore, the detection sensitivity of the capacitive sensor <NUM> is preferably set to be higher than the detection sensitivity of the capacitive sensor <NUM>.

If the operation body contacts or is placed in proximity to the rim <NUM>, the capacitance of the capacitive sensor <NUM> or the capacitance of the capacitive sensor <NUM> changes. When there is a change in the capacitance of the capacitive sensor <NUM> or in the capacitance of the capacitive sensor <NUM>, the controller <NUM> detects the change, and generates a detection signal. Based on the detection signal, the controller <NUM> or an external device illustrated in <FIG> determines whether the operation body contacts or approaches the rim <NUM>. At this time, the controller <NUM> determines whether the operation body contacts or is placed in proximity to the rim <NUM> by comparing the detection signal to thresholds that are set based on the distances between the rim <NUM> and the capacitive sensors <NUM> and <NUM>.

As illustrated in <FIG>, detection areas 150a, 150b, and 150c are set in the surroundings of the rim <NUM> and a space between the rim <NUM> and the capacitive sensor <NUM>.

If the operation body is located with the detection area 150a, the detection area 150b, the detection area 150c, or the detection area 150d, the capacitance of the capacitive sensor <NUM> or capacitance of the capacitive sensor <NUM> changes. The controller <NUM> detects the change in the capacitance of the capacitive sensor <NUM> or capacitance of the capacitive sensor <NUM>, and generates a detection signal.

The controller <NUM> or the external device illustrated in <FIG> determines whether the operation body contacts or is placed in proximity to the rim <NUM> based on the detection signal.

Claim 1:
A sensor device (<NUM>) of a capacitive type being provided on a spoke of a steering wheel, the steering wheel including a rim (<NUM>) and the spoke (<NUM>) that is connected to an inner side of the rim (<NUM>), the sensor device (<NUM>) comprising:
an electrode (<NUM>) configured to be capacitively coupleable to an object to be detected; and
a controller (<NUM>) configured to detect a change in capacitance of the electrode (<NUM>), and determine whether the object is in proximity to the rim (<NUM>) or the spoke based on the change in the capacitance of the electrode (<NUM>), the change in the capacitance of the electrode (<NUM>) occurring in response to the object being in proximity to the rim (<NUM>) or the spoke;
A) characterized in that the electrode (<NUM>) includes a plurality of fragments having different electrical resistance values based on distances from the rim (<NUM>),
or
B) characterized in that the controller (<NUM>) is configured to make the determination by comparing a signal from the electrode (<NUM>) to a threshold, the threshold being set based on a distance between the rim (<NUM>) and the electrode (<NUM>).