JP7848262B2 - Seat Wetness Detection Device - Google Patents

Description

This invention relates to a seat wetness detection device for detecting wetness in the seat portion of a seat.

The applicant has already proposed, in Patent Document 1, a seat wetness detection device that is miniaturizable, easily mountable to seats, and capable of accurately detecting seat wetness through simple control. This seat wetness detection device comprises a millimeter-wave sensor that transmits and receives millimeter waves toward the seat, and a reflector positioned inside the seat that reflects the millimeter waves from the sensor. The device determines seat wetness based on the degree of signal attenuation due to moisture in the reflected waves from the reflector.

In a specific embodiment of such a seat wetness detection device, the millimeter-wave sensor was mounted on the armrest portion on the side of the seat, positioned to irradiate millimeter waves from the side towards the seat surface located directly below it. Furthermore, multiple small, roughly rectangular metal plates were arranged at different positions beneath the seat surface, which was within the millimeter-wave irradiation range, to serve as reflectors.

Patent No. 7239647

Regarding the aforementioned seat wetness detection device, improvements were desired to address the following problem in its specific embodiment. Specifically, the millimeter-wave sensor is mounted on the armrest portion on the side of the seat surface, irradiating the seat surface with millimeter waves from a close, lateral position. Therefore, the irradiation range of the millimeter waves on the seat surface is relatively narrow, and if the metal plate, which acts as the reflector, is even slightly misaligned from the front of the millimeter-wave sensor, the reflection intensity decreases drastically, further narrowing the detection area.

Furthermore, depending on the positional relationship between the millimeter-wave sensor in the armrest and the seat, the areas slightly forward and to the sides of the seat surface tended to be blind spots in the millimeter-wave illumination range, making it difficult to detect wetting in those areas. In addition, since the reflective metal plates were placed separately from the seat's original frame, the number of parts and assembly steps increased, leading to higher costs. Moreover, even a slight deviation in the angle of each metal plate from the angle directly facing the millimeter-wave sensor drastically weakened the millimeter-wave reflection intensity, as mentioned above, requiring adjustment of the reflection angle of the metal plates, which was cumbersome.

This invention addresses the problems of the prior art described above. It aims to provide a seat wetness detection device that allows for a wide irradiation range of electromagnetic waves, including millimeter waves, across the entire seat surface, eliminating blind spots where water leakage detection on the seat surface is impossible. Furthermore, it eliminates the need for the cumbersome process of adjusting the reflection angle of the reflector, enabling simpler and more accurate detection of seat wetness over a wider area without increasing costs.

To achieve the aforementioned objectives, one aspect of the present invention is:
A seat wetness detection device for detecting wetness on a seat,
A sensor is installed at a height that looks downward from the seat portion of the seat, and transmits electromagnetic waves from the front towards the seat surface of the opposite seat, and receives the reflected waves that are returned from the front.
It comprises a reflective section that is positioned within the seat so as to overlap the seat surface in a plan view, and which also serves as the seat frame within the seat,
The reflective portion is capable of receiving electromagnetic waves transmitted from the sensor over its entire upper surface and reflecting them back toward the sensor.
The system is characterized by its ability to determine whether the seat is wet based on the degree of attenuation of the signal intensity due to moisture in the reflected wave received by the sensor.

The seat wetness detection device according to the present invention allows for the simple and accurate detection of seat wetness over a wider area without increasing costs.

This is a perspective view showing a seat to which the seat wetness detection device according to this embodiment is applied. A perspective view showing the internal structure of a seat to which the seat wetness detection device according to this embodiment is applied. This is a front view showing the internal structure of a seat to which the seat wetness detection device according to this embodiment is applied. This is a plan view showing the internal structure of a seat to which the seat wetness detection device according to this embodiment is applied. This is a side view showing the internal structure of a seat to which the seat wetness detection device according to this embodiment is applied. This is a perspective view showing the seat frame, which also serves as the reflective part of the seat wetness detection device according to this embodiment. This is a plan view showing the seat frame, which also serves as the reflective part of the seat wetness detection device according to this embodiment. This is a side view showing the seat frame, which also serves as the reflective part of the seat wetness detection device according to this embodiment. This is a bottom view showing the seat frame, which also serves as the reflective part of the seat wetness detection device according to this embodiment. This is a perspective view showing the corner reflector that forms the reflective part of the seat wetness detection device according to this embodiment. This is a perspective view showing a corner reflector unit that forms the reflective part of the seat wetness detection device according to this embodiment. This is a plan view showing a corner reflector unit that forms the reflective part of the seat wetness detection device according to this embodiment. This is a side view showing the support bracket for the reflective portion of the seat wetness detection device according to this embodiment. This is a plan view showing the support bracket for the reflective portion of the seat wetness detection device according to this embodiment. This is a front view showing the support bracket for the reflective portion of the seat wetness detection device according to this embodiment. This is a schematic block diagram showing the seat wetness detection device according to this embodiment. This diagram illustrates how millimeter waves from the millimeter-wave sensor of the seat wetness detection device according to this embodiment change in the dry and wet states of the seat. This is an explanatory diagram showing an example of a method for detecting seat wetness in the seat wetness detection device according to this embodiment. This flowchart shows an example of the processing after detecting seat wetness in the seat wetness detection device according to this embodiment. This is a perspective view showing the internal structure of a seat to which the seat wetness detection device according to Modification 1 of this embodiment is applied. This is a plan view showing the internal structure of a seat to which the seat wetness detection device according to Modification 1 of this embodiment is applied. This is an explanatory diagram showing an example of a graph displaying the signal intensity of the reflected wave in a seat wetness detection device according to Modification 1 of this embodiment. This is a perspective view showing the internal structure of a seat to which the seat wetness detection device according to Modification 2 of this embodiment is applied. This is a plan view showing the internal structure of a seat to which the seat wetness detection device according to Modification 2 of this embodiment is applied. This is an explanatory diagram showing an example of a graph displaying the signal intensity of the reflected wave in a seat wetness detection device according to a modified example 2 of this embodiment.

Hereinafter, a representative embodiment of the present invention will be described based on the drawings.
Figures 1 to 19 show one embodiment of the present invention.
The seat wetness detection device 10 according to this embodiment uses electromagnetic waves, particularly millimeter-wave radar, to detect wetness of the seat 1, especially the seat portion 3. Hereinafter, the seat 1 will be described using a seat installed in the passenger compartment of a railway vehicle as an example. Note that the components, shapes, numerical values, etc. shown in the embodiments described below are all examples of the present invention and are not intended to limit the present invention.

<Overview of Seat 1>
As shown in Figure 1, the seat 1 consists of a seat portion 3 attached to a base 2, with a backrest 4 supported on the rear end side of the seat portion 3. The base 2 is a metal base that supports the entire seat 1 on the floor, and includes, for example, a pair of side plates 20, 20 fixed opposite each other on the left and right sides. The front ends of each side plate 20 are connected via a front shaft 21, the rear ends of each side plate 20 are connected via a rear shaft 22, and the approximate centers of each side plate 20 are connected via an intermediate shaft 23.

As shown in Figures 1 to 5, the seat portion 3 is formed by attaching a cushion 3a to a seat frame 30, which is a seat frame fixed to the leg base 2, and covering the surface of the cushion 3a, including the seat surface, with a cover. The seat frame 30 is made of metal and is generally formed in a roughly rectangular panel shape, but as shown in Figures 6 to 9, it is configured to also serve as a reflector portion 31, which will be described later. A mounting portion 30b for supporting the backrest frame 40, described below, is provided at the rear end of the seat frame 30. The seat frame 30 is assembled to the upper side of the front shaft 21 and the rear shaft 22 via a mounting bracket 30c. Although not shown, armrests may be provided on both sides of the seat portion 3, similar to the aforementioned Patent Document 1.

The backrest 4 is formed by attaching a cushion 4a to a backrest frame 40, which is a back frame supported at the rear end of the seat frame 30, and covering the surface of the cushion 4a with a cover. The backrest frame 40 is formed by combining multiple metal materials to create a vertically elongated, roughly rectangular panel. Here, the backrest frame 40 is rotatably supported at the rear end of the seat frame 30, and the tilt angle of the backrest 4 is preferably adjustable via a damper 5 of the reclining mechanism.

As shown in Figure 1, the upper side of the backrest 4 is provided with front side sections 4b that extend forward from both the left and right sides, and a separate headrest 4c is attached between them. A reading light 6 is provided on one of the front side sections 4b, and a millimeter-wave sensor 11, described later, is located inside beside it. As shown in detail in Figure 2, a support bracket 50 for attaching the millimeter-wave sensor 11 is fixed to one end of the upper end 41 of the backrest frame 40. The support bracket 50, along with the millimeter-wave sensor 11, will also be described in detail later.

In such a seat 1, the seat frame 30 (reflective part 31) within the seat 3, which is the target of wetness detection, is made of metal and does not transmit electromagnetic waves. However, the cushion 3a is generally made of synthetic resin such as foamed urethane and therefore transmits electromagnetic waves, and the cover is also generally made of cloth and therefore transmits electromagnetic waves. Furthermore, the millimeter waves transmitted from the millimeter-wave sensor 11, described later, are also reflected by the leg rest 2 and other parts of the seat 1. However, the reflection angle of such reflected light is not such that it returns to the millimeter-wave sensor 11 except for slight diffuse reflection.

<Overview of the seat wetness detection device 10>
Figure 16 is a schematic block diagram showing the seat wetness detection device 10 according to this embodiment. As shown in Figure 16, the seat wetness detection device 10 includes a millimeter-wave sensor 11, a reflector 31, and a controller 60. The millimeter-wave sensor 11 and the controller 60 are connected to each other via wireless or wired means so that they can send and receive signals from one another. A display unit 65 and an operation unit 66 are also connected to the controller 60. Here, the millimeter-wave sensor 11 corresponds to the "sensor" of the present invention.

The millimeter-wave sensor 11, as will be described in detail later, comprises a transmitting unit 12 that transmits millimeter waves, a type of electromagnetic wave, and a receiving unit 13 that receives millimeter waves. Figure 16 also illustrates the state in which millimeter waves transmitted from the millimeter-wave sensor 11 toward the base unit 3 (hereinafter referred to as "transmitted waves") are returned as millimeter waves reflected by the reflecting unit 31 (hereinafter referred to as "reflected waves"). Here, since millimeter waves have a constant frequency as a so-called chirp signal, they are represented as a sine wave whose magnitude (amplitude) is expressed as a function of time.

<About millimeter waves>
The millimeter waves used in this embodiment refer to electromagnetic waves with a frequency band of 30 to 300 GHz, and are called "millimeter waves" (EHF) because their wavelength is 1 to 10 mm. Millimeter waves generally have the characteristics of being highly linear, being able to be treated like lasers, being able to secure a wide bandwidth, and being able to penetrate various materials such as synthetic resins and cloths. Furthermore, as a result of the inventors' diligent research, it has been found that the signal strength of millimeter waves is easily attenuated by moisture.

Experiments conducted by the inventors revealed that when millimeter waves (indicated as F in Figure 1) were irradiated onto the seat portion 3 of the seat 1 using the millimeter-wave sensor 11 described below, the millimeter waves passed directly through the cushion 3a of the seat portion 3 and were reflected by the internal metal seat frame 30 and leg rest 2. When the seat portion 3 was in a normal dry state, the reflected waves from the seat frame 30, etc., did not differ significantly from the signal strength at the time of transmission. However, when the seat portion 3 was wet, a clear attenuation of the reflected wave signal strength was observed. Therefore, it was found that millimeter waves are easily absorbed by moisture.

<Millimeter-wave sensor 11>
The millimeter-wave sensor 11 is generally a module capable of measuring the distance, direction, and speed to a distant target, but in this embodiment, it is used specifically for measuring the signal strength of millimeter waves reflected from the reflector 31, which will be described later. Therefore, in the usage mode of the millimeter-wave sensor 11 in this embodiment, the processing for measuring the distance, direction, and speed to the reflector 31, which is fixed in a fixed position, is omitted. The millimeter-wave sensor 11 comprises a transmitting unit 12 that transmits the generated millimeter waves toward the base 3, and a receiving unit 13 that receives the millimeter-wave sensor reflected from the reflector 31.

More specifically, the millimeter-wave sensor 11 typically consists of radio frequency components for transmission (TX) and reception (RX), analog components such as a synthesizer and clock, an A/D converter, a digital signal processor (DSP), and digital components such as a microcontroller (MCU). The millimeter-wave sensor 11 transmits millimeter waves generated by the synthesizer from the TX antenna, and receives the reflected waves from the target (reflector 31) with the RX antenna. Therefore, in this embodiment, the TX antenna corresponds to the "transmitting unit 12," and the RX antenna corresponds to the "receiving unit 13."

The millimeter-wave sensor 11 also has a function to generate an IF signal (intermediate frequency used for calculations) by mixing the transmitted wave and the reflected wave in a mixer, and to acquire information such as the position of the target (reflector 31) by performing various signal processing based on the data obtained from this IF signal. This allows the millimeter-wave sensor 11 to distinguish reflected waves from the auxiliary reflectors 31A and 31B (described later) separately from the reflector 31, and generate electrical signals according to the signal strength of each. The electrical signals generated here are output to the controller 60 (described later).

Such a millimeter-wave sensor 11 has several advantages: it is highly resistant to environmental changes due to the linearity of millimeter waves, offers excellent high-range resolution due to its wide bandwidth, enables high-precision detection due to the short wavelength of millimeter waves, and allows for miniaturization of the circuit and antenna. One of its features is its miniaturization capability, allowing it to be constructed as a substrate of only a few centimeters square. Therefore, as shown in Figure 1, the millimeter-wave sensor 11 of this embodiment can be installed even in the limited space within the front side portion 4b above the backrest 4.

As shown in Figures 2 to 5, a support bracket 50 is fixed to one upper end of the backrest frame 40, and the millimeter-wave sensor 11 is attached to the support bracket 50. By positioning the millimeter-wave sensor 11 on the upper side of the backrest 4 at a height that faces downwards towards the seat 3, millimeter waves can be irradiated from the front over almost the entire surface of the seat 3. The seat surface of the seat 3 refers to the upper, approximately horizontal surface of the cushion 3a that primarily contacts the seated person, and corresponds to the area that overlaps with the seat frame 30 in a plan view.

Furthermore, the angle of the millimeter-wave sensor 11 relative to the seat 3, that is, the angle of millimeter-wave irradiation directed towards the seat 3, can be adjusted by the support bracket 50. More specifically, as shown in Figure 2, an angle member 42 is fixed along the approximately horizontal upper end 41 of the backrest frame 40, and a support bracket 50 is attached to one end of the angle member 42 facing outwards from the seat. Here, the support bracket 50 is mounted at an angle closer to the inside of the seat, such that its vertical back portion 51 points toward a perpendicular line passing through the center of the seat surface of the seat 3.

<Support bracket 50>
As shown in Figures 13 to 15, the support bracket 50 comprises a rear surface 51 that forms a vertical surface, a pair of side surfaces 52, 52 that are bent forward at a right angle from both ends of the rear surface 51, and a mounting surface 53 that is supported between the side surfaces 52 in a position facing the rear surface 51. The mounting surface 53 is the part on its front side to which the millimeter-wave sensor 11 is attached, and is supported so that its angle can be adjusted in the vertical direction.

Specifically, the lower edge of the mounting surface 53 is pivotally supported via a horizontal rotating shaft 54 installed between each side surface 52. Meanwhile, a horizontal movable shaft 55 is pivotally supported on the upper edge of the mounting surface 53. Each side surface 52 has an arc-shaped guide groove 56 centered on the rotating shaft 54, and both ends of the movable shaft 55 are movably fitted into the guide grooves 56 of each side surface 52.

The movable shaft 55 is formed in a bolt shape, with one end serving as the bolt head 55a, contacting the guide groove 56 of one side portion 52, and the other end fitted with a nut 55b that contacts the guide groove 56 of the other side portion 52. Therefore, by loosening the nut 55b, the mounting surface portion 53 (i.e., the millimeter-wave sensor 11) can be adjusted to any tilt angle around the rotation axis 54, and by tightening the nut 55b at the desired tilt angle, it can be fixed at that angle. The specific shape of the millimeter-wave sensor 11 itself, which is attached to the mounting surface portion 53, is well known, so a detailed explanation is omitted.

<Reflector 31>
As shown in Figures 1 and 2, a reflector 31, which also serves as the seat frame 30, is provided beneath the seat surface of the cushion 3a of the seat 3. The reflector 31 is configured to receive millimeter waves transmitted from the millimeter wave sensor 11 and reflect them back towards the millimeter wave sensor 11 across its entire upper surface. More specifically, as shown in Figures 6 to 9, the upper surface 30a of the seat frame 30 serves as the reflector 31, and a plurality of corner reflectors 32 are integrally arranged in a densely packed manner on the same plane, with their respective opening surfaces overlapping the upper surface 30a.

As shown in Figure 10, the corner reflector 32 is a reflector made by joining three right-angled isosceles triangular metal plates. With the corner reflector 32, regardless of which surface the millimeter wave is incident on, reflection occurs repeatedly within the three surfaces, allowing the reflected wave to be accurately reflected in the direction from which the millimeter wave was incident. In other words, the corner reflector 32 can widen the directivity of the reflected wave compared to other reflector shapes, and a uniform reflected wave can be obtained regardless of the incident angle of the millimeter wave. Therefore, even if the millimeter wave sensor 11 is located above the backrest 4 and the distance increases, causing the reflected wave to weaken, the reflection efficiency can be increased accordingly.

As shown in Figure 6, the multiple corner reflectors 32 are joined together by welding or other means at the edges of their respective openings, so that their openings are closely aligned on the same plane and form a single continuous reflective section 31. This reflective section 31 is integrated as part of the seat frame 30 itself, occupying as wide an area as possible on the upper surface 30a of the seat frame 30. Areas on the upper surface 30a of the seat frame 30 that cannot accommodate the reflective section 31 (multiple corner reflectors 32) are left as a horizontal, plate-like upper surface 30a.

In this embodiment, the area of the upper surface 30a of the seat frame 30 into which the reflective section 31 is incorporated is pre-cut out, and the entire reflective section 31, which consists of multiple connected corner reflectors 32, is integrally incorporated into this area by welding or the like. Thus, the reflective section 31, which also serves as the seat frame 30, may be constructed separately and later attached as part of the seat frame 30, or it may be integrally molded together with the seat frame 30 by sheet metal press molding or casting.

The specific number and arrangement of the multiple corner reflectors 32 forming the reflective section 31 are design matters that can be determined as appropriate, not limited to the illustrated example. As shown in Figures 11 and 12, a predetermined number of corner reflectors 32 (five in the illustrated example) may be pre-configured as units constituting the reflective section 31, for example, by arranging them in a straight line. The unit formed by combining the five corner reflectors 32 in a straight line, as shown in Figures 11 and 12, directly constitutes the auxiliary reflective sections 31A and 31B, which will be described later, separate from the reflective section 31.

<Controller 60>
As shown in Figure 16, the controller 60 consists of, for example, a microcomputer and peripheral electronic equipment, and specifically consists of a processor (CPU), non-volatile memory (ROM) for storing programs executed by the processor and various fixed data, and volatile memory (RAM) for storing data temporarily required for program execution, etc., as its main components. The controller 60 has the functions of an input unit 61, a control unit 62, an output unit 63, a storage unit 64, etc.

The input unit 61 receives input of various information, such as the electrical signals from the millimeter-wave sensor 11, and various other information, such as numerical values specified by the operation unit 66.
The control unit 62 controls the transmission of millimeter waves from the transmitter unit 12 of the millimeter-wave sensor 11 and processes the electrical signals from the millimeter-wave sensor 11 to detect wetting of the seat 1 (more precisely, the seat portion 3) based on the degree to which the signal strength is attenuated by moisture as the millimeter waves pass through the inside of the seat 1. The specific method for detecting wetting of the seat portion 3 will be described later.

The control unit 62 controls the transmission of millimeter waves from the transmitter unit 12 of the millimeter-wave sensor 11 to repeat, for example, at a predetermined period. More specifically, the control unit 62 should be set to transmit millimeter waves from the transmitter unit 12 of the millimeter-wave sensor 11 at predetermined timings. Here, the predetermined timing can be determined as appropriate, for example, just before arrival at the next station where passengers disembark, or when the train arrives at the final station.

The output unit 63 outputs information regarding the wetness of seat 1 detected by the control unit 62. The output destination of the signal from the output unit 63 is mainly the display unit 65, but is not limited to the display unit 65.
The memory unit 64 stores programs and various data used by the control unit 62 to detect the wetness of seat 1. Examples of such data include pre-measured values, such as the signal strength of the reflected wave when seat 1 is dry.

The display unit 65 displays the determination result regarding the wetness of seat 1 from the control unit 62. The display unit 65 may, for example, use a computer monitor, and will display various information, including the determination result, in a visually readable format using text, images, etc. In addition to the display by the display unit 65, sound notifications such as artificial voice or alarms may also be provided through an audio output device such as a speaker.

The operation unit 66 is operated by the user for tasks such as inputting numerical data necessary for various processes performed by the control unit 62. The operation unit 66 can be, for example, a computer mouse, keyboard, or touch panel. Users of the seat wetness detection device 10 can input various data required by the control unit 62 for processing and instruct processing operations by operating this operation unit 66.

<Operation of the seat wetness detection device 10>
Next, we will explain how the seat 1 is detected to be wet by the seat wetness detection device 10.
In Figure 16, the millimeter-wave sensor 11 generates millimeter waves using a synthesizer at a predetermined timing based on a command from the control unit 62 of the controller 60, and transmits the millimeter waves from its front side toward the seat surface of the seat portion 3 below.

As shown in Figure 1, since the millimeter-wave sensor 11 is located on the upper side of the backrest 4, the distance from the millimeter-wave sensor 11 to the seat 3 is greater than, for example, if it were located on the armrest immediately to the side of the seat 3. This allows for a wider irradiation range of millimeter waves onto the seat 3. Furthermore, in this embodiment, the millimeter-wave sensor 11 is positioned on the front side 4b of the backrest 4, away from the center, to prevent the sitter from feeling a foreign object on their head. However, it is also possible to irradiate the seat 3 with millimeter waves from an angle that is as directly facing its front as possible.

The transmitted waves from the millimeter-wave sensor 11 pass through the cushion 3a of the seat 3 and are reflected by the reflector 31, which also serves as the seat frame 30. These reflected waves then pass through the cushion 3a again and return to the millimeter-wave sensor 11, where they are received by the receiver 13. As shown in Figure 6, since the reflector 31 also serves as the seat frame 30, the number of parts and assembly steps can be reduced compared to a case where the reflector is placed separately from the seat frame 30, thereby lowering the manufacturing cost of the seat 1.

Furthermore, the reflective section 31 is capable of receiving and reflecting millimeter waves across its entire upper surface. Therefore, it is possible to detect the degree of wetness over a wide area, such as the entire seat surface of the seat section 3. Moreover, while, for example, if multiple reflectors were locally arranged within the seat section 3, it would be necessary to adjust the reflection angle of each reflector, this cumbersome process is unnecessary with the reflective section 31 of this embodiment.

In particular, the reflective section 31 is formed by integrally connecting multiple corner reflectors 32, each closely arranged on the same plane where its opening surface overlaps with the upper surface 30a of the seat frame 30. With this type of reflective section 31, it is possible to increase the reflection efficiency across its entire surface using the individual corner reflectors 32, and even at greater distances from the millimeter-wave sensor 11, a stronger reflection intensity can be achieved without angle adjustment compared to a flat reflector.

Then, when the reflected wave from the reflector 31 returns to the millimeter-wave sensor 11 and is received, the millimeter-wave sensor 11 mixes the transmitted wave and the reflected wave using a mixer to generate an IF signal (intermediate frequency), and various signal processing is performed based on the data obtained from this IF signal. The electrical signal generated by the millimeter-wave sensor 11 is output to the controller 60 and stored in the memory unit 64. The electrical signal stored in the memory unit 64 is digitally converted by an AD conversion circuit, etc., and stored in the memory area of the control unit 62. The control unit 62 performs a process to calculate the signal strength of the reflected wave from the reflector 31 based on the electrical signal received from the millimeter-wave sensor 11.

Figure 16(b) shows an example of a graph displaying the signal intensity of the reflected wave from the reflector 31. The horizontal axis represents the optical distance from the millimeter-wave sensor 11 to the reflector 31, and the vertical axis represents the signal intensity of the reflected wave. Here, the distance on the horizontal axis is proportional to the time from the time of transmission wave output until the reflected wave returns, and is predetermined by the arrangement of the reflector 31. The signal intensity on the vertical axis is expressed as a relative value, and its unit is not particularly limited. The peak of the signal intensity of the reflected wave from the reflector 31 occurs at a predetermined point on the horizontal axis depending on the distance from the transmitter 12.

The chirp of the reflected wave from the reflector 31 is processed, for example, using an FFT to detect the distance to the reflector 31. Since the distance to the reflector 31 is fixed, the distance FFT corresponding to the chirp will show a peak at the same point (horizontal axis). The control unit 62 determines the wetness of the seat 1 based on the results of this graphing process. Here, the wetness of the seat 1 is synonymous with the moisture contained primarily in the cushion 3a of the seat 3.

Figure 17 shows how the millimeter waves from the millimeter-wave sensor 11 change when the seat 3 is in a normal dry state and when the seat 3 is wet due to some cause. The transmitted wave from the millimeter-wave sensor 11 (transmitter 12) toward the seat 3 shows a significant difference between the initial signal strength of the transmitted wave and the signal strength of the reflected wave across the entire upper surface of the reflector 31, depending on whether it is in a "dry state" (no moisture present) or a "wet state" (moisture present).

The [Concept] in Figure 17 schematically illustrates the state in which the transmitted wave from the millimeter-wave sensor 11 is reflected by the reflector 31 and returns as a reflected wave. As shown in the [Concept] in Figure 17(a), when the seat 3 is dry, the transmitted wave from the millimeter-wave sensor 11 passes through the cushion 3a and reaches the reflector 31 with little attenuation, and the reflected wave from the reflector 31 similarly returns to the millimeter-wave sensor 11 with little attenuation. On the other hand, as shown in the [Concept] in Figure 17(b), when the seat 3 is wet, the transmitted wave from the millimeter-wave sensor 11 passes through the cushion 3a and is considerably attenuated by the moisture before reaching the reflector 31, and the reflected wave from the reflector 31 is further attenuated before returning to the millimeter-wave sensor 11.

Thus, in a wet state, the millimeter waves emitted from the millimeter-wave sensor 11 are significantly weaker when they return to the sensor 11 compared to a dry state. In other words, the inventors' experiments have confirmed that the signal intensity of the reflected wave is significantly lower in a wet state than in a dry state. Therefore, the control unit 62 can detect the wetness of the seat 1 based on the ratio (signal ratio) between the signal intensity of the reflected wave in a wet state and the signal intensity of the reflected wave in a dry state.

The graph in Figure 17 shows the signal intensity of the reflected wave from the reflector 31. As shown in the graph in Figure 17(a), when seat 1 is dry, the peak signal intensity of the reflected wave is, for example, 5000 as a relative value. On the other hand, as shown in the graph in Figure 17(b), when seat 1 is wet, the peak signal intensity of the reflected wave is, for example, 2800 as a relative value. Thus, the signal intensity of the reflected wave is significantly attenuated in the wet state than in the dry state. Specifically, in the numerical example mentioned above, the attenuation in the wet state is 0.56 (2800/5000) times that of the dry state, or 44%.

The aforementioned signal ratio of 0.56 approaches 1.0 as seat 1 dries and its moisture content decreases. Based on this value, a threshold for the acceptable level of wetness of seat 1 is determined, for example, between 0.56 and 1.0. Specifically, if the threshold is set to 0.8 based on data from subjective tests that assess the feeling of "wetness," then the system will determine that the seat is wet if the attenuation of the reflected wave signal intensity is less than 0.8. Of course, a threshold of 0.8 is merely an example; it can be set to another value, such as 0.5, as appropriate.

Such threshold settings can be adjusted as appropriate by the operation unit 66. Specifically, for example, it can be set to read the signal strength at a height H mm on the vertical axis of the graph. Here, the height H mm can be arbitrarily changed. Furthermore, as will be described later, the signal strength height H mm can be set to use the average value of ±w on the horizontal axis. Here, the width ±w can also be arbitrarily changed. It is also desirable to allow arbitrary changes to the timing and frequency Y Hz of signal strength reading. Note that the comparison of peak signal strength values does not necessarily require graphing.

Furthermore, it would be beneficial to allow users to arbitrarily change the maximum and minimum values (Max and Min) of the signal strength to be read. Regardless of the settings, as mentioned earlier, the system should be configured to set a flag indicating that the seat is wet when the attenuation rate of the reflected wave signal strength falls below 1/X (X > 1). When this flag is set, the display unit 65 should display a warning, such as the word "wet," indicating that seat 1 is wet, as shown in the [Monitor] section of Figure 17(b). Subsequent processing will be described later.

As described above, when determining the signal ratio of the reflected wave signal intensity in wet and dry conditions, the calculation can be performed using the peak value or the average value over a predetermined width ± w. However, to minimize errors, the following calculation is also possible. That is, using the signal intensity peak as a reference, the determination of whether the seat portion 3 is wet or not can be made based on the area ratio in a predetermined range of the graph, including the signal intensity within the ± w width on the horizontal axis, as mentioned above.

Furthermore, as another determination method, a predetermined range on the horizontal axis of the graph may be set to include the peak of the signal intensity of the reflected wave from the reflector 31 and a predetermined width before and after it. The determination of whether the seat portion 3 is wet or not may then be based on the area ratio within this predetermined range. That is, as shown in Figure 18, the determination of whether the seat portion 3 is wet may be based on whether the ratio of the area enclosed by the quadratic curve of signal intensity when the seat portion 3 is dry to the area enclosed by the quadratic curve of signal intensity when the seat portion 3 is wet exceeds a predetermined threshold.

The specific threshold setting is the same as in the case of comparing the peak values mentioned above. The calculation of the area enclosed by curves or lines (horizontal axis, etc.) representing signal strength on the graph can be done using well-known formulas, and it is advisable to program this calculation in advance. Furthermore, the area of each region on the graph to be compared can be set using the operation unit 66, similar to the threshold setting.

The determination of such thresholds and predetermined ranges in the graph are design considerations that can be appropriately determined based on data from various experiments and simulations. Of course, the comparison using area ratios in the graph mentioned above does not necessarily depend on geometric processing; for example, wetness detection could be performed by comparing the integrated values of signal intensity and distance data for dry and wet conditions.

<Response after detecting wetness in seat 3>
Figure 19 is a flowchart showing an example of processing after the seat wetness detection device 10 detects wetness in the seat portion 3. When wetness in the seat portion 3 is detected by the control unit 62 of the controller 60, as described above (step S101), information regarding the seat number of the wet seat is output to, for example, the driver's cab of the vehicle (step S102).

Based on this, the information is output to the display on seat 1 (step S103), to the conductor's tablet (step S104), and further to a monitor on the ground outside the vehicle (step S111). Furthermore, based on the information output to the ground monitor, the inventory status of replacement parts (cushion 3a of seat 3) is confirmed (step S112).

Next, the conductor checks the actual wetness of the seat portion 3 of seat 1, as displayed on the tablet (step S105). At this point, they determine whether or not the seat portion 3 needs to be replaced (step S106). If the conductor determines that the seat portion 3 needs to be replaced, they request transportation to the next station based on the availability of replacement parts (step S113). The conductor then receives the replacement parts at the next station (step S107), removes the wet seat portion 3, and replaces it with a new seat portion 3 (step S108).

Incidentally, in the aforementioned detection of wetting of the seat portion 3, a decision was made selectively based on whether or not the attenuation of the millimeter-wave signal intensity exceeded a threshold. The actual need to replace the seat portion 3 was then determined, for example, manually. However, it is also possible to control the system to automatically determine whether or not such replacement is necessary. Such control can be implemented relatively easily by modifying the program in the controller 60.

In other words, the detection of wetting of the seat portion 3 in step S101 in Figure 19 may be controlled not by an alternative judgment of whether the degree of attenuation of the millimeter-wave signal strength is above or below a certain threshold, but by, for example, dividing the degree of attenuation of the signal strength into multiple ranks for judgment. This would allow for measures such as locally drying the slightly wet areas of the seat portion 3 without replacing the entire seat portion 3, if the wetness rank is low.

<Modification 1 of the reflective section 31>
Figures 20 to 22 show a modified example 1 of the reflective section 31 according to the embodiment.
In this modified example 1, in addition to the reflective portion 31 that forms the upper surface of the seat frame 30 as described above, a front end auxiliary reflective portion 31A is added along the front end side of the periphery of the seat frame 30. The front end auxiliary reflective portion 31A is configured to receive electromagnetic waves transmitted from the millimeter-wave sensor 11 that have deviated in front of the reflective portion 31 and to reflect them back toward the millimeter-wave sensor 11.

More specifically, the front auxiliary reflector section 31A consists of a unit formed by linearly combining the five corner reflectors 32 shown in Figures 11 and 12, and is integrally connected along the front end of the seat frame 30. This connection can be achieved, for example, by welding them together via a narrow, thin metal plate, or by directly welding the open ends of the corner reflectors 32 forming the front auxiliary reflector section 31A. The angle at which the front auxiliary reflector section 31A is connected can be adjusted from a state where it is horizontally aligned with the upper surface of the reflector section 31 to a state where it is bent upward toward the millimeter-wave sensor 11 on the upper side of the backrest 4.

Thus, the front auxiliary reflector 31A is constructed separately from the reflector 31 and attached to the seat frame 30 afterwards, or it may be constructed to be integrated with the seat frame 30 or the reflector 31 from the beginning. In this case, the total number of parts and assembly man-hours for the seat 1 are reduced. In either configuration, it is preferable that the front auxiliary reflector 31A be adjustable to the optimal angle toward the millimeter-wave sensor 11. The specific length and size of the front auxiliary reflector 31A, i.e., the number and arrangement of the corner reflectors 32, are design matters that can be determined as appropriate.

In Figure 1, the distance from the seat surface of the seat portion 3 to the reflector portion 31 below it is equal to the thickness of the cushion 3a. Therefore, a portion of the seat's periphery (front edge and side edge) located above the irradiation angle from the millimeter-wave sensor 11 to the reflector portion 31 will be outside the millimeter-wave transmission and reception path. By providing a front auxiliary reflector portion 31A on the front edge of the seat frame 30, the millimeter-wave transmission and reception path can be extended, making it possible to detect wetting in the corresponding portion of the seat's periphery without any omissions.

As mentioned above, the millimeter-wave sensor 11 also has the function of acquiring positional information of an object (reflector 31, etc.). Therefore, it can distinguish between reflected waves from the reflector 31 and the front auxiliary reflector 31A, and generate electrical signals corresponding to the respective signal strengths. Consequently, when the signal strengths of the reflected waves from each reflector 31 and 31A are represented on the same graph, for example, as shown in Figure 22, the peaks in the signal strength of each reflector 31 and 31A will occur at different points on the horizontal axis depending on the distance from the millimeter-wave sensor 11. This makes it possible to precisely and comprehensively determine the wetness of the seat 3, all the way to the front end of the seat surface, by comparing the peaks of the reflected wave signal strengths and the area ratios in the graph for each route within the cushion 3a leading to each reflector 31 and 31A.

<Modified example 2 of the reflective section 31>
Figures 23 to 25 show yet another modified example 2 of the reflective section 31 according to this embodiment.
In this modified example 2, in addition to the aforementioned reflective section 31 and front end auxiliary reflective section 31A, a pair of side end auxiliary reflective sections 31B1 and 31B2 are added along both ends of the periphery of the seat frame 30. The side end auxiliary reflective sections 31B1 and 31B2 are configured to receive electromagnetic waves transmitted from the millimeter-wave sensor 11 that have deviated to the side of the reflective section 31, and to reflect them back toward the millimeter-wave sensor 11.

More specifically, the side-end auxiliary reflectors 31B1 and 31B2, like the front-end auxiliary reflector 31A, consist of units formed by linearly combining the five corner reflectors 32 shown in Figures 11 and 12, and are integrally connected along the side ends of the seat frame 30. The side-end auxiliary reflectors 31B1 and 31B2 can be constructed separately from the reflector 31 and retrofitted to the seat frame 30, or they can be pre-assembled integrally with the seat frame 30 or the reflector 31. Furthermore, it is preferable that the side-end auxiliary reflectors 31B1 and 31B2 be configured to be adjustable to the optimal angle toward the millimeter-wave sensor 11.

Even when these side-edge auxiliary reflectors 31B1 and 31B2 are added, if the signal intensity of the reflected waves from each reflector 31, 31A, 31B1, and 31B2 is represented on the same graph, the peak signal intensity for each reflector 31, 31A, 31B1, and 31B2 will occur at different points on the horizontal axis depending on the distance from the millimeter-wave sensor 11, as shown in Figure 25. This allows for a detailed and comprehensive determination of the wetness of the seat 3, including the front and both sides of the seat surface, by comparing the peak signal intensity of the reflected waves and the area ratios in the graph for each route within the cushion 3a leading to each reflector 31, 31A, 31B1, and 31B2.

<Structure and Effects of the Invention>
Although this embodiment has been described above, the present invention is not limited to the embodiments described above. The present invention derived from the embodiments described above will be described below.

First, the present invention relates to a seat wetness detection device 10 for detecting wetness of a seat 1,
A sensor 11 is provided at a height overlooking the seat portion 3 of seat 1, and transmits electromagnetic waves from the front towards the seat surface of the opposing seat portion 3, and receives the reflected waves that are returned by the reflection of the electromagnetic waves from the front.
It comprises a reflective part 31 that is provided within the seat 3 so as to overlap the seat surface in a plan view, and which also serves as the seat frame 30 within the seat 3,
The reflective portion 31 is capable of receiving electromagnetic waves transmitted from the sensor 11 over its entire upper surface and reflecting them back toward the sensor 11.
The system is characterized by its ability to determine whether the seat portion 3 is wet based on the degree of attenuation of the signal intensity due to moisture in the reflected wave received by the sensor 11.

With this type of seat wetness detection device 10, the sensor 11 is positioned at a height that faces downwards towards the seat portion 3 of the seat 1, allowing electromagnetic waves to be transmitted from the front to the entire seat surface of the seat portion 3. Furthermore, the distance from the sensor 11 to the seat surface is relatively large, ensuring a wide range of electromagnetic wave irradiation.

Furthermore, since the reflective section 31, which reflects electromagnetic waves from the sensor 11, also serves as the seat frame 30, the number of parts and assembly steps can be reduced compared to a case where the reflective section 31 is provided separately from the seat frame 3, thus reducing costs. Moreover, the reflective section 31 can receive electromagnetic waves and reflect them back towards the sensor 11 across its entire upper surface. Therefore, the troublesome task of adjusting the reflection angle of the reflective section 31 is unnecessary.

The seat wetness detection device 10 determines the wetness of the seat 3 based on the degree to which the signal intensity of the reflected wave from the reflector 31, which covers a wide area of the seat 3, is attenuated by moisture as it passes through the seat 3, relative to the transmitted wave from the sensor 11 positioned at a high location. This determination allows for simpler and more accurate detection of seat wetness over a wider area.

Furthermore, in this invention, the seat frame 30 is formed in a panel shape, and the upper surface of the seat frame 30 is characterized by having multiple corner reflectors 32 integrally connected as the reflective portion 31, with their respective opening surfaces closely aligned on the same plane.

With this type of seat frame 30's reflective section 31, the reflective efficiency can be increased across its entire surface by the individual corner reflectors 32. Even at greater distances from the sensor 11, a strong reflective intensity can be achieved without fine adjustments to the angle, compared to a flat reflector.

Furthermore, the present invention is characterized by the provision of auxiliary reflective sections 31A, 31B1, and 31B2, which are attached to the reflective section 31 along at least a portion of the periphery of the seat frame 30, and which receive electromagnetic waves transmitted from the sensor 11 that have deviated from the reflective section 31, and are capable of reflecting them back toward the sensor 11.

Since these auxiliary reflective sections 31A, 31B1, and 31B2 extend outward from the periphery of the seat frame 30, they can reliably receive and reflect electromagnetic waves that pass through the seat 3 but miss the reflective section 31. Therefore, wetting of the area of the seat surface of the seat 3, including the area extending to the end, can be reliably detected. The auxiliary reflective sections 31A, 31B1, and 31B2 may be constructed separately from the reflective section 31 and added later as needed, or they may be pre-assembled with the reflective section 31 to reduce the number of parts and assembly time.

Furthermore, in this invention, the sensor 11 is characterized by being provided on the upper side of the backrest 4, which is supported on the rear end side of the seat portion 3.

As described above, by positioning the sensor 11 on the upper side of the backrest 4, the distance from the sensor 11 to the seat surface of the seat 3 is greater than, for example, if it were positioned on the armrest immediately to the side of the seat 3. This allows for a wider range of electromagnetic wave irradiation to be secured for the seat 3. Furthermore, it becomes possible to irradiate the seat surface of the seat 3 from an angle as close as possible to its front. Additionally, the sensor 11 can be assembled and completed as a single component within the scope of a single seat 1 product.

Furthermore, in the present invention, the sensor 11 is attached to the backrest frame 40 within the backrest 4 via a support bracket 50 that allows adjustment of the irradiation angle of electromagnetic waves from the front side toward the seat 3.
This makes it easy to adjust the irradiation range of the electromagnetic waves transmitted from the sensor 11 so that it overlaps with the entire seat surface of the seat portion 3, which is located directly below and in front of the seat 1, according to the various design specifications of the seat 1.

Furthermore, in the present invention, the determination of whether the seat portion 3 is wet is made by determining whether the ratio of the peak value of the reflected wave signal intensity reflected from the reflecting portion 31 and received by the sensor 11, when the seat portion 3 is dry, to the peak value of the seat portion 3 when it is wet, exceeds a predetermined threshold.
By making a determination based solely on the numerical comparison of the peak signal strength, the wetness of seat 1 can be determined with extremely simple control.

Furthermore, in the present invention, the determination of whether the seat portion 3 is wet is made by determining whether the ratio of the area enclosed by the quadratic curve representing the signal strength when the seat portion 3 is dry to the area enclosed by the quadratic curve representing the signal strength when the seat portion 3 is wet exceeds a predetermined threshold, in a graph representing the signal strength of the reflected wave reflected from the reflecting portion 31 and received by the sensor 11.
By using this method of determining signal strength by comparing the area of a quadratic curve, the variation in measurement accuracy in determining whether seat 1 is wet can be reduced, further improving the accuracy of the detection results.

Furthermore, the present invention is characterized by comprising a display unit 65 that displays the result of determining whether the seat portion 3 is wet.
This allows the display unit 65 to easily provide information regarding the wetness determination result of seat 1. Therefore, anyone who sees the display can more easily take measures regarding the wetness of seat 1.

Although this embodiment has been described above with reference to the drawings, the specific configuration is not limited to these embodiments, and any changes or additions that do not depart from the spirit of the present invention are also included. For example, the seat 1 to be detected by the seat wetness detection device 10 is not necessarily limited to seats installed in the passenger compartment of a railway vehicle, but may also be seats in other vehicles such as aircraft, buses, or ships, or the seat portion of seats installed in movie theaters or theaters.

Furthermore, the placement of the millimeter-wave sensor 11 is not limited to the backrest 4 of seat 1. It could also be placed on the back of the backrest of another seat located in front of seat 1, or on the vehicle's ceiling or overhead racks. Moreover, the electromagnetic waves used in this invention are not necessarily limited to millimeter waves. Additionally, the shape and size of the reflecting section 31 and the auxiliary reflecting sections 31A and 31B, as well as their specific arrangement, angles, and number, are not limited to the embodiments described above.

This invention is not limited to seats installed in the passenger compartments of various vehicles such as railway cars, aircraft, automobiles, and ships, but can also be broadly applied to seats installed in movie theaters, theaters, and the like.

1...Seat 2...Footrest 3...Seat portion 4...Backrest 10...Seat wetness detection device 11...Millimeter wave sensor 30...Seat portion frame 31...Reflector 31A...Front end auxiliary reflector 31B...Side end auxiliary reflector 50...Support bracket 60...Controller 61...Input unit 62...Control unit 63...Output unit 64...Storage unit 65...Display unit 66...Operation unit

Claims (7)

A seat wetness detection device for detecting wetness on a seat,
A sensor is installed at a height that looks downward from the seat portion of the seat, and transmits electromagnetic waves from the front towards the seat surface of the opposite seat, and receives the reflected waves that are returned from the front.
It comprises a reflective section provided on the same plane as the seat surface in a plan view, and which also serves as the seat frame within the seat,
The reflective portion is capable of receiving electromagnetic waves transmitted from the sensor over its entire upper surface and reflecting them back toward the sensor.
Based on the degree of attenuation of the signal intensity due to moisture in the reflected wave received by the aforementioned sensor, it is possible to determine whether the seat is wet .
The seat frame is provided with an auxiliary reflective portion attached to the reflective portion, extending outward from a portion of the periphery of the seat frame,
The seat wetness detection device is characterized in that the auxiliary reflective section is capable of adjusting its angle to receive electromagnetic waves that have passed through a part of the periphery of the seat located above the irradiation angle of the electromagnetic waves transmitted from the sensor to the reflective section and have deviated from the reflective section, and to reflect them toward the sensor, thereby enabling the detection of wetness in a part of the periphery of the seat via a different route than that between the sensor and the reflective section . The seat wetness detection device according to claim 1, characterized in that the seat frame is formed in a panel shape, and the upper surface of the seat frame is integrally connected to the reflective portion, with a plurality of corner reflectors arranged closely together on the same plane with their respective openings. The seat wetness detection device according to claim 1, characterized in that the sensor is provided on the upper side of the backrest supported on the rear end side of the seat portion. The seat wetness detection device according to claim 3 , characterized in that the sensor is attached to the backrest frame within the backrest via a support bracket that allows adjustment of the irradiation angle of electromagnetic waves from the front side toward the seat. The seat wetness detection device according to claim 1, characterized in that the determination of whether the seat is wet is made by determining whether the ratio of the peak value of the reflected wave signal intensity when the seat is dry to the peak value when the seat is wet exceeds a predetermined threshold, based on the signal intensity of the reflected wave reflected from the reflecting part and the auxiliary reflecting part and received by the sensor. The seat wetness detection device according to claim 1, characterized in that the determination of whether the seat is wet is made by determining whether the ratio of the area enclosed by the quadratic curve representing the signal intensity when the seat is dry to the area enclosed by the quadratic curve representing the signal intensity when the seat is wet exceeds a predetermined threshold, in a graph representing the signal intensity of the reflected waves reflected from the reflecting part and the auxiliary reflecting part and received by the sensor. The seat wetness detection device according to claim 1, 2, 3, 4, 5, or 6 , further comprising a display unit for displaying the result of determining whether the seat is wet.