JP7842402B2 - Electronic cymbals - Google Patents

Description

This invention relates to an electronic cymbal capable of detecting strikes on its striking surface and outputting an electrical signal.

Conventional electronic cymbals, as disclosed in, for example, Patent Document 1, comprised an electronic cymbal body with a pad section having a striking surface that can be struck by a performer, and a frame section supporting the back side of the pad section; a vibration sensor capable of detecting strikes on the striking surface of the pad section; and an output cable for outputting the detection signal detected by the vibration sensor to the outside. When a performer struck the striking surface of the electronic cymbal body with a stick, the vibration sensor could detect the strike and output a signal externally, allowing for performance similar to that of an acoustic cymbal.

Furthermore, conventional electronic cymbals have been proposed that feature openings at predetermined positions on the striking surface, giving them a design similar to effect cymbals used in acoustic instruments. These electronic cymbals have openings at predetermined positions on the striking surface, and to prevent the striking surface from appearing too thick, the openings are designed so that their diameter expands from the striking surface side to the back side. This allows for the reproduction of the shape of effect cymbals with openings on the striking surface while making the striking surface appear thinner, thus improving the design aesthetics.

Japanese Patent Publication No. 2005-331972 Japanese Patent Publication No. 2019-159219

However, in the conventional technology described above, the opening is formed so that the hole diameter expands from the striking surface side to the reversible side. While this allows for the reproduction of the effect cymbal's shape and makes the striking surface appear thinner, it requires the integral formation of reinforcing parts such as ribs protruding from the edge of the opening. This means the ribs become visible from the opening, potentially hindering the impression of a thin striking surface.

This invention was made in view of these circumstances, and its objective is to provide an electronic cymbal that can reproduce the shape of an effect cymbal with an opening formed on the striking surface, while also reinforcing the opening edge of the opening and making the striking surface appear thinner.

The invention described in claim 1 is an electronic cymbal comprising: a main body having a striking surface that can be struck by a performer, with an opening formed at a predetermined position on the striking surface; a reinforcing portion projecting from the opening edge of the opening on the back side of the main body; and a detection means attached to the main body that can detect striking of the striking surface and output an electrical signal, characterized in that the reinforcing portion is formed such that the outer edge of the opening protrudes more significantly from the central edge of the opening relative to the main body than the central edge of the opening relative to the main body.

The invention described in claim 2 is characterized in that, in the electronic cymbal described in claim 1, the reinforcing portion is formed to protrude in an arc shape along the edge of the opening.

The invention described in claim 3 is characterized in that, in the electronic cymbal described in claim 1, the reinforcing portion is formed only on the outer edge of the opening relative to the main body, and the reinforcing portion does not protrude from the central edge of the opening relative to the main body.

The invention described in claim 4 is characterized in that, in the electronic cymbal described in claim 1, the reinforcing portion is formed with a continuously decreasing protrusion dimension from the opening edge on the outer edge side of the main body to the opening edge on the central side of the main body.

The invention described in claim 5 is characterized in that, in the electronic cymbal described in claim 1, the main body comprises a pad portion on which the striking surface is formed and a frame portion supporting the back side of the pad portion, the opening is formed to penetrate the pad portion and the frame portion, and the reinforcing portion is formed to protrude from the back side of the frame portion.

The invention described in claim 6 is characterized in that, in the electronic cymbal described in claim 5, the frame portion has a cover member attached to its bottom surface to cover the detection means, and the edge of the cover member and the frame portion around its periphery are formed smoothly and continuously.

According to the invention of claim 1, the reinforcing portion is formed such that the outer edge of the opening protrudes more significantly from the central edge of the main body than the central edge of the opening relative to the main body. This allows for the reproduction of the shape of an effect cymbal with an opening formed on the striking surface, while simultaneously reinforcing the opening edge and making the striking surface appear thinner.

According to the invention of claim 2, since the reinforcing portion is formed to protrude in an arc shape along the edge of the opening, the opening edge of the opening can be reinforced over the entire length of the extending direction of the reinforcing portion, and the opening edge can be effectively reinforced.

According to the invention of claim 3, the reinforcing portion is formed only on the outer edge of the opening relative to the main body, and no reinforcing portion is formed protruding from the central opening relative to the main body. Therefore, the opening edge can be reinforced without forming a reinforcing portion that is visible from the opening.

According to the invention of claim 4, the reinforcing portion is formed with a continuously decreasing projection dimension from the outer edge opening to the central opening to the main body. This allows the reinforcing portion to be smoothly formed along its extension direction, effectively reinforcing while further improving its aesthetic appeal.

According to the invention of claim 5, the opening is formed to penetrate both the pad portion and the frame portion, and the reinforcing portion is formed to protrude from the back side of the frame portion. Therefore, the reinforcing portion can be made by protruding from the back side of the frame portion, which is difficult to see through the opening, thus ensuring reliable reinforcement while maintaining aesthetic appeal.

According to the invention of claim 6, the frame portion has a cover member attached to its bottom surface to cover the detection means, and the edge of the cover member and the frame portion around its periphery are formed smoothly and continuously. This prevents the cover member from being visible through the opening from the striking surface side, and also eliminates the protruding portion on the bottom side of the main body, thereby improving the design.

Perspective view showing the overall appearance of the complete electronic cymbal of the present invention. Three-view drawing showing the main body of the electronic cymbal. Cross-sectional view along line III-III in Figure 2 Exploded perspective view showing the main body of the electronic cymbal. This is a bottom view showing the main body with the cover member removed. This is a bottom view showing the main body with the cover member and piezoelectric element removed. Cross-sectional view along line VII-VII in Figure 6 A schematic diagram showing the piezoelectric element attached to the electronic cymbal. Cross-sectional view of the IX-IX line in Figure 8. Three-view drawing showing the pad section of the electronic cymbal. Perspective view of the pad section from below. Three-view drawing showing the frame of the electronic cymbal. Perspective view of the frame section from below. Three-view drawing showing the cover component of the electronic cymbal. Perspective view of the cover component from below. A bottom view showing an electronic cymbal according to another embodiment of the present invention, in which the reinforcing portion is formed along the opening edge and only on the outer edge side of the opening. A bottom view showing an electronic cymbal according to another embodiment of the present invention, in which the reinforcing portion is formed linearly only on the outer edge opening. A schematic cross-sectional view showing the piezoelectric element attached to the electronic cymbal. Three-view drawing showing the buffer member attached to the piezoelectric element of the electronic cymbal.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
As shown in Figures 1 to 6, the electronic cymbal according to this embodiment comprises a main body 1 having a striking surface F that can be struck by a performer, which is composed of a pad portion 2 and a frame portion 3; a piezoelectric element 4 (detection means) attached to the inner circumferential surface S of the frame portion 3 in the main body 1; and a cover member 8.

As shown in Figure 1, the main body 1 is supported at a predetermined height by a support stand T that extends vertically from the stand legs Ta. The main body 1 comprises a pad section 2 having a striking surface F that can be struck by a performer, and a frame section 3 that supports the back side of the pad section 2. The pad section 2 has multiple openings Ha, and the frame section 3 has multiple openings Hb. These openings Ha and Hb communicate to form the opening H of the main body 1. In the figure, the symbol L indicates a tightening member for tightening and fixing the main body 1 to the support stand T.

The pad portion 2 is made of a rubber material or soft resin (in this embodiment, silicone rubber) that can be struck with a stick, and consists of a disc-shaped member with an insertion hole 2a formed at the center through which the support stand T can be inserted, as shown in Figures 10 and 11. The striking surface F formed on the upper surface of the pad portion 2 is composed of a cup portion Fb formed by bulging in the center of the pad portion 2, an edge portion Fc formed at the periphery of the pad portion 2, and a bow portion Fa consisting of the region between the cup portion Fb and the edge portion Fc.

The frame portion 3 is made of a hard resin or metal (ABS resin in this embodiment) and consists of a disc-shaped member with a through hole 3a formed at its center, through which the support stand T can be inserted, as shown in Figures 12 and 13. Furthermore, the main body portion 1 is formed by attaching and integrating the pad portion 2 to the surface of the frame portion 3, and a bulging portion 3b is formed in the center of the main body portion, corresponding to the cup portion Fb of the pad portion 2.

Furthermore, a mounting surface Sa for attaching the piezoelectric element 4 is formed on the inner circumferential surface S of the bulging portion 3b in the frame portion 3. As shown in Figures 12 and 13, multiple mounting surfaces Sa (four in this embodiment) are formed along the circumferential direction (circumferential direction) on the inner circumferential surface S of the frame portion 3 in the main body portion 1, and a piezoelectric element 4 is attached to each mounting surface Sa.

As shown in Figures 14 and 15, the cover member 8 is an annular member with an opening 8a in the center through which a support stand T or the like can be inserted. As shown in Figures 2 and 3, it is attached to the back side of the frame portion 3, covering the inner circumferential surface S of the bulging portion 3b, and also covering the substrate 5 (see Figures 3-6) on which a predetermined electrical circuit is formed. This substrate 5 is electrically connected to each piezoelectric element 4, and the detection signals of each piezoelectric element 4 are transmitted to the substrate 5. In this embodiment, as shown in the enlarged view of Figure 3, the edge of the cover member 8 and the frame portion 3 around its periphery are formed smoothly and continuously.

The piezoelectric element 4, acting as a vibration sensor (detection means), is attached to the mounting surface Sa formed on the main body 1 (frame 3) via a buffer member D. It is a sensor capable of converting vibrations generated by striking the striking surface F into electrical signals. As shown in Figures 8 and 9, it comprises, for example, an upper electrode 4a made of a silver conductor, a lower electrode 4b made of, for example, a brass plate, and a piezoelectric ceramic 4c interposed between the upper electrode 4a and the lower electrode 4b.

Furthermore, the upper electrode 4a is connected to wiring h1, and the lower electrode 4b is connected to wiring h2. When the performer strikes the striking surface F and vibrations are transmitted to the piezoelectric element 4, the entire structure flexes due to the vibration, and a voltage corresponding to the amount of flexure is generated. When this voltage is generated, the upper electrode 4a acts as the positive electrode and the lower electrode 4b acts as the negative electrode, causing current to flow through wirings h1 and h2. This current is then output as an electrical signal via the circuit board 5 and output cable 6.

However, although the piezoelectric element 4 generates voltage and outputs an electrical signal by bending in direction b perpendicular to the mounting surface Sa, it has a structure that makes it difficult to bend in direction a parallel to the mounting surface Sa. Therefore, vibration in direction b perpendicular to the mounting surface Sa has a higher output characteristic (higher voltage or higher current output characteristic) compared to vibration in direction a parallel to the mounting surface Sa.

Furthermore, the piezoelectric element 4 according to this embodiment has a cushioning member D made of polyurethane foam or the like attached to its bottom surface. As shown in Figure 9, the surface of the cushioning member D is attached to the mounting surface Sa with an adhesive or the like, while maintaining close contact. The cushioning member D is formed in a cylindrical shape, and as shown in Figure 9, its outer diameter is smaller than the outer diameter of the piezoelectric element 4 (preferably about 67% of the diameter of the piezoelectric element, which acts as a vibration node for the piezoelectric element 4), ensuring that the deflection of the piezoelectric element 4 due to vibration is maintained.

Furthermore, an edge sensor E is attached to the peripheral edge on the surface side of the frame portion 3, enabling detection of impacts to the edge portion Fc of the pad portion 2. This edge sensor E, like the piezoelectric element 4, is electrically connected to the substrate 5 via wiring, and the detection signal is transmitted to the substrate 5. The output cable 6 is connected to the piezoelectric element 4 (vibration sensor) and the edge sensor E via the substrate 5, and is capable of outputting the detection signals detected by the piezoelectric element 4 and the edge sensor E to the outside. The output cable 6 has an output jack J at its tip, allowing connection to an external signal processing device (not shown).

When the performer strikes the striking surface F of the pad section 2 with a stick, causing the main body section 1 to vibrate, the piezoelectric element 4 detects the strength of the strike, and an electrical signal corresponding to that strength is output via the output cable 6 to an external signal processing device (not shown). Furthermore, depending on the on/off state of the edge sensor E, the strike to the edge section Fc is identified. If a strike is detected while the edge sensor E is off, it is determined that the strike occurred to the bow section Fa or the cup section Fb, and a predetermined musical tone is output.

As shown in Figures 3 and 4, the shaft sleeve 7 is made of a cylindrical elastic member (rubber in this embodiment) with an insertion hole formed in its center. This shaft sleeve 7 is interposed between the frame portion 3 and the support stand T within the insertion hole 3a of the frame portion 3, thereby suppressing the transmission of vibrations generated by impacts to the main body portion 1 to the support stand T.

As shown in Figures 6 and 7, the mounting surface Sa consists of a surface inclined vertically β from a horizontal plane (a plane including the horizontal direction α) toward the center of the main body 1, and the piezoelectric elements 4 are mounted concentrically at equal intervals around the central axis C of the main body 1 (see Figures 3 and 7). That is, since the inner circumferential surface S formed on the frame portion 3 of the main body 1 is shaped like a frustoconical pyramid, multiple (four in this embodiment) mounting surfaces Sa are formed at equal intervals along the circumferential direction centered on the central axis C on this inner circumferential surface S, and piezoelectric elements 4 are mounted concentrically on each of these mounting surfaces Sa.

Furthermore, if the shape of the main body 1, including a predetermined region (a predetermined region on the inner or outer circumferential surface), is considered as a virtual cone shape, then multiple mounting surfaces Sa are formed concentrically around the central axis C on the side surface of the virtual cone shape (a sector-shaped surface in the unfolded view, the same applies hereinafter). Moreover, each mounting surface Sa consists of a surface inclined at a predetermined angle from the horizontal plane to the vertical β towards the center of the frame 3 in the main body 1. Therefore, the piezoelectric elements 4 can be arranged three-dimensionally (three dimensions composed of horizontal α and vertical β), and the piezoelectric elements 4 can be sufficiently deflected by vibrations in either the horizontal α or vertical β direction. This allows for good and uniform output of electrical signals in response to vibrations in both the horizontal α and vertical β directions accompanying the striking of the striking surface F.

Furthermore, if the shape of the main body 1, including a predetermined area, is considered as a virtual cone shape, then multiple mounting surfaces Sa are formed concentrically around the central axis C on the side surface of the virtual cone shape (four in this embodiment). The mounting surfaces Sa in this embodiment are formed along the circumferential direction on the inner circumferential surface S of the frame portion 3 in the main body 1. As shown in Figures 6 and 7, they consist of a plane (flat surface) corresponding to the mounting portion of the piezoelectric element 4 (buffer member D in this embodiment), and as shown in Figures 5 and 6, they have substantially the same shape (circular) and dimensions (diameter) as the outer shape of the piezoelectric element 4. Note that the piezoelectric element 4 is not limited to having a circular outer shape; it may also have an elliptical or rectangular shape. In such cases, the mounting surface Sa will have substantially the same shape as the outer shape of the piezoelectric element 4.

In this embodiment, the electronic cymbal has a design similar to an effect cymbal in an acoustic instrument, achieved by forming an opening H at a predetermined position on the striking surface F. This opening H is formed by aligning an opening Ha formed in the pad portion 2 with an opening Hb formed in the frame portion 3. It penetrates from the surface of the main body portion 1 (the striking surface F of the pad portion 2) to the back surface (the back surface of the frame portion 3), and is formed to widen in diameter from the striking surface F side to the back surface side.

Furthermore, as shown in Figure 3, the back side of the opening H (opening Hb formed in the frame portion 3) of the electronic cymbal according to this embodiment is provided with a reinforcing portion G that protrudes from the opening edge of the opening H. This reinforcing portion G consists of a rib integrally formed on the periphery of the opening Hb in the frame portion 3. As shown in Figures 3 and 5-7, the opening edge on the outer edge side (outer diameter side) relative to the main body portion 1 protrudes more significantly than the opening edge on the central side (inner diameter side) relative to the main body portion 1.

Furthermore, as shown in Figures 3 and 5-7, the reinforcing portion G according to this embodiment is formed to protrude in an arc shape along the edge of the opening H (opening Hb of the frame portion 3), and the protruding dimension is continuously reduced from the outer edge of the opening relative to the main body portion 1 to the central edge of the opening relative to the main body portion 1 (the protruding dimension gradually decreases from the outer diameter side to the inner diameter side).

According to this embodiment, the reinforcing portion G is formed such that the outer edge of the opening protrudes more significantly from the central edge of the main body 1 than from the central edge of the opening 1. This allows for the reproduction of the shape of an effect cymbal with an opening H formed in the striking surface F, while simultaneously reinforcing the opening edge of the opening H and making the striking surface F appear thinner. In other words, since the main body 1, supported at a predetermined height by the support stand T, is easily visible through the opening H, and the outer side is difficult to see, it is possible to suppress the protrusion dimension of the reinforcing portion G on the outer edge side (inner diameter side) while ensuring the protrusion dimension on the central side (outer diameter side), thereby effectively reinforcing the opening edge while making the striking surface F appear thinner.

Furthermore, since the reinforcing portion G according to this embodiment is formed to protrude in an arc shape along the edge of the opening H, it can reinforce the opening edge of the opening H over the entire extension direction of the reinforcing portion G, thereby effectively reinforcing the opening edge. Moreover, since the reinforcing portion G according to this embodiment is formed with a continuously decreasing protrusion dimension from the outer edge of the opening to the central edge of the opening to the main body 1, the reinforcing portion G can be formed smoothly over the extension direction, thereby effectively reinforcing while further improving the aesthetic appearance.

Furthermore, in this embodiment, the opening H is formed to penetrate both the pad portion 2 and the frame portion 3, and the reinforcing portion G is formed to protrude from the back side of the frame portion 3. Therefore, the back side of the frame portion 3, which is difficult to see through the opening H, can be made to protrude and serve as the reinforcing portion, ensuring reliable reinforcement while maintaining aesthetic appeal. Additionally, the frame portion 3 has a cover member 8 attached to its bottom surface to cover the piezoelectric element (detection means), and the edge of the cover member 8 and its peripheral frame portion 3 are formed smoothly and continuously. This prevents the cover member 8 from being visible through the opening H from the striking surface F side, and eliminates the protruding portion on the bottom side of the main body portion 1, improving aesthetic appeal.

Furthermore, in this embodiment, the mounting surface Sa consists of a surface inclined vertically β from a horizontal plane (a plane including the horizontal direction α) toward the center of the main body 1. Since the piezoelectric elements 4 are mounted concentrically at equal intervals around the central axis C of the main body 1, the piezoelectric elements 4 can reliably and stably convert any strikes from various directions onto the striking surface F into electrical signals and output them.

Furthermore, if three or more piezoelectric elements 4 are mounted concentrically at equal intervals around the central axis C of the main body 1 according to this embodiment, the impact on the striking surface F can be stably converted into an electrical signal by the piezoelectric elements 4 and output uniformly for impacts in various directions. Moreover, since the mounting surface Sa according to this embodiment is provided along the circumferential direction on the outer or inner circumferential surface of the main body 1, the piezoelectric elements 4 can receive vibrations caused by the impact on the striking surface F more uniformly over the entire circumference of the striking surface F, thereby suppressing variations in the output of the electrical signal due to differences in the striking location.

Furthermore, the mounting surface Sa according to this embodiment is formed along the circumferential direction on the outer or inner circumferential surface of the main body 1 and consists of a flat surface corresponding to the mounting portion (cushioning member D) of the piezoelectric element 4. Therefore, compared to fixing to a curved surface, the piezoelectric element 4 can be fixed more stably to the mounting surface Sa. Note that the mounting surface Sa is not limited to a flat surface; it may also be a curved surface forming the inner circumferential surface S (or outer circumferential surface).

Furthermore, since the mounting surface Sa according to this embodiment has substantially the same shape and dimensions as the outer shape of the piezoelectric element 4, the mounting position of the piezoelectric element 4 relative to the inner circumferential surface S of the main body 1 can be accurately determined during the mounting work of the piezoelectric element 4, thereby improving the positioning accuracy of the piezoelectric element 4. In other words, by mounting the piezoelectric element 4 in accordance with the mounting surface Sa, the positioning of the piezoelectric element 4 is performed naturally, improving positioning accuracy.

Furthermore, in this embodiment, the piezoelectric element 4 is fitted with a cushioning member D, and since the cushioning member D is in contact with the mounting surface Sa, damage to the piezoelectric element 4 due to vibrations caused by striking can be avoided. The cushioning member D only needs to have cushioning properties and be attachable to the bottom surface of the piezoelectric element 4; its material and shape are not limited.

Although this embodiment has been described above, the present invention is not limited thereto. For example, as shown in Figure 16, the reinforcing portion G may be formed only on the outer edge (outer diameter side) of the opening relative to the main body 1, and the reinforcing portion G may not protrude from the central (inner diameter side) opening relative to the main body 1. In this case, the opening edge can be reinforced without forming a reinforcing portion G that is visible from the opening H.

Furthermore, as shown in Figure 17, the reinforcing portion G may be formed only on the outer edge (outer diameter side) of the opening relative to the main body 1, and the reinforcing portion G may not protrude from the central (inner diameter side) opening relative to the main body 1. Moreover, the reinforcing portion G may be formed along the circumferential direction of the main body 1 (frame portion 3). In addition, the reinforcing portion G is not limited to having an inverted triangular cross-sectional shape; it may also be a rib with other cross-sectional shapes, such as a rectangle or a U-shape.

Furthermore, the buffer member D is not limited to a cylindrical shape as in the above embodiment, but may also be annular, as shown in Figures 21 and 22. In such annular buffer member D, the back surface Db is attached to the bottom surface (lower electrode 4b) of the piezoelectric element 4 with an adhesive, and the front surface Da is attached to the mounting surface Sa with an adhesive. The annular buffer member D has an outer diameter t1 that is approximately equal to the outer diameter of the piezoelectric element 4. This allows the piezoelectric element 4 to follow the deflection of the main body 1 well while suppressing excessive free vibration of the piezoelectric element 4 itself due to impact. Therefore, it is possible to maintain the voltage of the output electrical signal while accelerating attenuation and preventing false sound generation.

However, it is preferable that the inner diameter t2 of the hollow portion of the annular cushioning member D is 60-80% of the outer diameter t1, and most preferably 70% of the outer diameter t1. In other embodiments of the annular cushioning member D, the surface Da that is in close contact with the mounting surface Sa is a flat surface, but it may also be a surface with slits formed over part or the entire circumference of the surface Da, or the ratio of the inner diameter t2 to the outer diameter t1 may be a different ratio.

In this embodiment, the main body 1 is composed of a pad portion 2 and a frame portion 3, with a mounting surface Sa formed on the inner circumferential surface S of the frame portion 3. However, the mounting surface may be formed on the inner circumferential surface of a single main body 1. Furthermore, in this embodiment, the piezoelectric element 4 is used to detect the impact on the striking surface F and output an electrical signal. However, other types of vibration sensors may be used to detect vibrations caused by impact.

If the electronic cymbal has a reinforced section formed where the outer edge of the opening protrudes more significantly from the central edge of the main body than the central edge of the opening, then this method can be applied to cymbals with different external shapes or those with added functions.

1. Main body 2. Pad portion 2a. Insertion hole 3. Frame portion 3a. Insertion hole 3b. Bulging portion 4. Piezoelectric element (vibration sensor) (detection means)
5. Circuit board 6. Output cable 7. Axis sleeve 7a. Insertion hole 8. Cover member 8a. Opening S. Inner circumferential surface Sa. Mounting surface T. Support stand Ta. Stand leg J. Output jack F. Striking surface Fa. Bow part Fb. Cup part Fc. Edge part L. Tightening members H, Ha, Hb. Opening D. Cushioning member Da. Surface Db. Back surface E. Edge sensor G. Reinforcement part (rib).

Claims (6)

A main body having a striking surface that can be struck by a performer, and having an opening formed at a predetermined position on the striking surface,
A reinforcing portion is formed to protrude from the opening edge of the opening on the back side of the main body,
A detection means attached to the main body is capable of detecting strikes on the striking surface and outputting an electrical signal,
An electronic cymbal equipped with,
An electronic cymbal characterized in that the reinforcing portion is formed such that the outer edge of the opening protrudes more significantly from the central edge of the main body than the central edge of the opening relative to the main body. The electronic cymbal according to claim 1, characterized in that the reinforcing portion is formed to protrude in an arc shape along the edge of the opening. The electronic cymbal according to claim 1, characterized in that the reinforcing portion is formed only on the outer edge of the opening relative to the main body, and the reinforcing portion does not protrude from the central opening relative to the main body. The reinforcing portion is characterized by being formed with a continuously decreasing protrusion dimension from the outer edge of the opening relative to the main body to the central edge of the opening relative to the main body, as described in claim 1. The electronic cymbal according to claim 1, characterized in that the main body comprises a pad portion on which the striking surface is formed and a frame portion supporting the back side of the pad portion, the opening is formed passing through the pad portion and the frame portion, and the reinforcing portion is formed protruding from the back side of the frame portion. The frame portion is characterized in that a cover member covering the detection means is attached to its bottom surface, and the edge of the cover member and the frame portion around its periphery are formed smoothly and continuously, as described in claim 5.