JP7437284B2 - ground child - Google Patents

Description

The present invention relates to a ground element.

BACKGROUND ART Conventionally, a technique has been known in which a frequency-variable beacon is installed on the ground side, and the beacon is detected on the top of the train to control the stop or speed of the train. The onboard side receives information from the ground side by utilizing the fact that when the onboard child approaches the ground child, it is electromagnetically coupled to the ground child, and as a result, the resonant frequency of the onboard child changes.

Furthermore, in order to increase the amount of information that can be transmitted, a ground element is also known in which a plurality of (for example, two) inductors are arranged one on top of the other with a predetermined overlap width (see Patent Document 1). When the onboard element passes above the ground element, it simultaneously resonates at two types of resonance frequencies with respect to the transmission signal from the onboard element. Therefore, information on the combination of two types of resonance frequencies can be transmitted to the upper side of the vehicle.

Japanese Patent Application Publication No. 2018-188045

However, in the technique of Patent Document 1, the resonant frequency characteristics of the ground element change depending on the passing position of the onboard element, and a situation may occur in which the ground element cannot be detected correctly on the upper side of the vehicle. That is, the two inductors in the ground element are staggered in a direction intersecting the train running direction (sleeper direction) so that their inner regions overlap by a predetermined overlap width. Therefore, if the passing position of the onboard child is shifted in the inductor arrangement direction (sleeper direction) due to the train shaking at the timing when the onboard child passes over the ground coil, each of the two inductors It was thought that there might be a case where the relative distance of the on-vehicle child passing position to the vehicle was significantly different. In that case, since the amount of variation in the resonant frequency characteristics (mainly signal amplitude at the resonant frequency) related to each inductor will be different, it cannot be said that there is a possibility that the ground element cannot be properly detected.

Note that a resonance type is known as an applied method of the variable frequency type. While the variable frequency type is a method that changes the oscillation frequency, the resonance type is a method that increases the amplitude of the resonant frequency among multiple frequencies transmitted to the ground element side (for example, a spread spectrum method or , a method also called a new variable frequency method, a composite wave method, etc.). In a broad sense, it is considered that the resonance type can also be included in the variable frequency type, but for fear that the variable frequency type may be interpreted in a narrow sense, it will be described as a different term in this specification.

An object of the present invention is to provide a beacon technology that can appropriately detect a beacon on the vehicle top side while increasing the amount of information that can be transmitted.

A first invention for solving the above problems includes a first resonant circuit that has a first inductor and resonates at a first resonant frequency with respect to a transmission signal from an onboard element, and a second inductor. and a second resonant circuit that resonates at a second resonant frequency with respect to the transmission signal, and the first inductor has a front-back direction when viewed from above with the train running direction as the front-back direction. The left and right center portions of the second inductor are recessed so that the length is shortened, and the second inductor is recessed at the front and rear center portions so that the length in the left and right direction is shortened in the top view, and the second inductor is recessed so that the length in the left and right direction is shortened when viewed from the top. and the second inductor are arranged in an overlapping manner.

According to the first invention, the first inductor forming the first resonant circuit and the second inductor forming the second resonant circuit are arranged in an overlapping manner. One of the first inductors is recessed at the center of the left and right so that the length in the front and back direction is shortened, and the second inductor is recessed at the center of the front and back so that the length in the left and right direction is shortened. The part is concave. Therefore, even when the first inductor and the second inductor are arranged one on top of the other, the magnetic flux passage area inside the winding of the first inductor and the magnetic flux passage area inside the winding of the second inductor are different. The overlapping area can be reduced. According to this, unlike the technique of Patent Document 1, it is not necessary to dispose the first inductor and the second inductor with a large shift in the sleeper direction. Therefore, even if the passing position of the onboard child is shifted in the direction of the sleeper due to the movement of the train, etc., the relative distances of the passing position of the onboard child with respect to each of the first inductor and the second inductor can be made approximately equal. As a result, the amount of variation in the resonant frequency characteristics related to each inductor becomes approximately the same, and as a result, the ground element can be properly detected.

Further, this ground element resonates at two types of resonant frequencies, a first resonant frequency and a second resonant frequency, with respect to the transmission signal from the onboard element. Therefore, information on the combination of the first resonant frequency and the second resonant frequency can be transmitted from the ground side to the onboard side.

Further, in the second invention, the first inductor has the left and right center portions recessed from both front and rear directions when viewed from the top, and the second inductor has the front and rear center portions recessed from the front and rear directions when viewed from the top. , is the ground coil of the first invention, which is recessed from both left and right directions.

According to the second invention, the first inductor can have a shape in which its left and right center portions are recessed from both front and rear directions, and the second inductor can have a shape in which its front and rear center portions are recessed from both left and right directions.

Further, a third invention provides the ground inductor according to the first or second invention, wherein the first inductor and the second inductor are arranged so that their center portions overlap in the top view. It is.

According to the third invention, since the first inductor and the second inductor are arranged so that their central portions overlap, the vehicle The distance between the upper child and the center of each inductor is the same. Therefore, even if the passing position of the onboard child shifts in the left-right direction (sleeper direction) and moves away from the center, the resonance frequency characteristics of the two resonance circuits do not change significantly.

Further, a fourth invention is the ground element according to any one of the first to third inventions, wherein the first inductor and the second inductor have symmetrical shapes when viewed from above.

According to the fourth invention, the reduction characteristic of the signal level of the resonant frequency with respect to the distance between the passing position of the onboard element and the center portion of each inductor is the same on both the left and right sides. In other words, the signal level will be the same whether the vehicle passes on the left side of the center or on the right side of the center if the distance from the center is the same. . Therefore, even if the horizontal direction of the ground element and the installation position with respect to the rail are not strictly determined, the resonance frequencies related to the two resonance circuits can be equally detected, and thus the ground element can be detected properly.

Further, in a fifth invention, the second inductor has a shape that satisfies a predetermined approximation condition with a shape obtained by rotating the first inductor by 90 degrees clockwise or counterclockwise when viewed from the top. This is a ground coil according to any one of the first to fourth inventions.

According to the fifth invention, the ground element can be configured by rotating one of two inductors having a shape that satisfies a predetermined approximation condition by 90 degrees.

Further, in a sixth aspect of the present invention, the first inductor and the second inductor have an area that overlaps in the top view with an area of the first inductor and the second inductor when resonating with the transmission signal. The ground element according to any one of the first to fifth inventions, wherein the area is such that the electromagnetic coupling state between the ground element and the ground element is in a predetermined reduced state.

According to the sixth invention, the area of the overlapping region of the first inductor and the second inductor in the top view of the ground element is determined by the area of the area where the first inductor and the second inductor overlap when viewed from above of the ground element. The inductors can be arranged one on top of the other to provide an area where the electromagnetic coupling state between the inductors and the inductors is reduced to a predetermined value.

FIG. 2 is a schematic diagram showing a schematic circuit configuration of a ground element and an outline of a track on which the ground element is installed. FIG. 3 is a schematic diagram illustrating a first inductor and a second inductor. FIG. 3 is a diagram showing an extracted first inductor of FIG. 2; FIG. 3 is a diagram showing an extracted second inductor of FIG. 2; FIG. 3 is a diagram illustrating the relationship between the area of an overlapping region when viewed from above and the degree of electromagnetic coupling. The figure which shows the resonance frequency characteristic of a ground element. The schematic diagram explaining the 1st inductor and the 2nd inductor of the ground element in a modification. FIG. 7 is a schematic diagram illustrating a first inductor and a second inductor of a ground element in another modification. FIG. 9 is a diagram showing an extracted first inductor of FIG. 8; FIG. 9 is a diagram showing an extracted second inductor of FIG. 8;

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments described below, and the forms to which the present invention can be applied are not limited to the following embodiments. In addition, in the drawings, the same parts are denoted by the same reference numerals.

FIG. 1 is a schematic diagram showing a schematic circuit configuration of a beacon 1 in this embodiment and an outline of a track on which the beacon 1 is installed. As shown in FIG. 1, the ground element 1 is installed between the left and right rails 3, 3, etc. above the sleepers 5 that support the pair of rails 3, 3, or between the sleepers 5. More specifically, the beacon 1 is oriented so that the arrangement direction of the first inductor L1 and the second inductor L2 intersects the train running direction (the direction along the rails 3, 3), and , will be installed between 3 and 3.

The ground element 1 is a variable frequency or resonant type ground element, and includes a first resonant circuit 11 that resonates at a first resonant frequency f1 in response to a transmission signal from an onboard element of a train passing above; A second resonant circuit 13 that resonates at a second resonant frequency f2 with respect to the transmission signal is provided. The first resonant circuit 11 has a first inductor L1 and a capacitor C1, and the second resonant circuit 13 has a second inductor L2 and a capacitor C2. This ground element 1 has a circuit composed of passive elements, does not require a power source, is not equipped with so-called electronic circuits such as arithmetic circuits, relays, etc., and does not require cable connection with other devices. This is a device that can be installed with just a single device.

FIG. 2 is an overhead view of the ground element 1, and schematically shows the first inductor L1 and the second inductor L2 as seen from the top of the ground element 1. Here, the train running direction is defined as the front-rear direction, and the arrangement direction of the first inductor L1 and the second inductor L2 that intersects with the train running direction is defined as the left-right direction.

As shown in FIG. 2, the region surrounded by the first inductor L1 and the region surrounded by the second inductor L2 have shapes such that some of the regions overlap when the ground element 1 is viewed from above. The area of the overlapping area (hereinafter referred to as "top view overlapping area") is a predetermined area. In FIG. 2, the overlapping region in top view is shown with hatching. Note that this hatching does not mean a solid pattern, but is merely an illustration for easy understanding, and there is no member corresponding to the hatching in the actual ground element 1. The first inductor L1 and the second inductor L2 are each mounted by printing a spiral coil pattern on the substrate 15, for example. The number of turns of the coil pattern can be set as appropriate, and can also be increased by increasing the number of inner layers of the substrate 15 and forming through holes to connect the coil patterns of each inner layer.

The region surrounded by the first inductor L1 can be said to be a magnetic flux passage region inside the winding of the first inductor L1. Similarly, the area surrounded by the second inductor L2 can be said to be a magnetic flux passage area inside the winding of the second inductor L2. The overlapping region in top view is an overlapping region of the magnetic flux passing region inside the winding of the first inductor L1 and the magnetic flux passing region inside the winding of the second inductor L2. If the winding shapes of the first inductor L1 and the second inductor L2 are made into a simple circle or rectangle, the central part of the first inductor L1 and the central part of the second inductor L2 should be overlapped. If they are arranged, the overlapping region in top view becomes large. If it is desired to reduce the overlapping region in top view, it is necessary to arrange the first inductor L1 and the second inductor L2 with a large deviation.

However, according to the present embodiment, since the first inductor L1 and the second inductor L2 have a unique shape, even in the case of FIG. can do. Even if the passing position of the onboard child is shifted in the sleeper direction due to the movement of the train, etc., the relative distances of the passing position of the onboard child with respect to each of the first inductor L1 and the second inductor L2 are made approximately equal. As a result, the amount of variation in the resonance frequency characteristics related to each inductor becomes approximately the same, and as a result, it becomes possible to appropriately detect the ground element 1.

This will be explained in more detail.
FIG. 3 shows an extracted first inductor L1 in FIG. 2, and FIG. 4 shows an extracted second inductor L2 in FIG.

(1) About the shape of each inductor First, as shown in FIG. 3, the first inductor L1 has a length in the front-rear direction of the left and right center portions when viewed from above of the ground element 1, which is equal to the length in the front-rear direction of the left and right sides. It has a concave shape at its left and right center portions so that it is shorter than the length L23. In the example of FIG. 3, the length in the front-rear direction of the left and right center portions is the shortest length L21 at the center portion (near the center) of the first inductor L1. On the other hand, as shown in FIG. 4, the second inductor L2 is recessed so that the length in the left-right direction at the front-rear center portion is shorter than the length L33 in the left-right direction at the front and rear portions when viewed from above. I'm here. In the example of FIG. 4, the length in the left-right direction of the front-rear center portion is the shortest length L31 at the center portion of the second inductor L2.

This can also be expressed as follows. That is, the first inductor L1 is bent in a concave shape such that the left and right center portions of the upper side and the left and right center portions of the lower side approach each other toward the center of the first inductor L1 when viewed from above. It has a shape. On the other hand, the second inductor L2 is bent in a concave shape such that the upper and lower center portions of the left side and the upper and lower center portions of the right side approach each other toward the center of the second inductor L2 when viewed from above. It is the shape.

In this embodiment, the first inductor L1 and the second inductor L2 have a symmetrical shape, and one inductor, the second inductor L2, is the other inductor, the first inductor, in a top view of the ground element 1. The inductor L1 has a shape obtained by rotating the inductor L1 by 90 degrees clockwise or counterclockwise, and a shape that satisfies predetermined approximation conditions.

Specifically, as shown in FIGS. 2 to 4, for example, the shape of the first inductor L1 is such that, when viewed from above of the ground element 1, the left and right center portions leave the center portion of the first inductor L1. The shape of the second inductor L2 is such that, when viewed from above, the front and rear center portions are symmetrically cut out into mountain shapes, leaving the central portion of the second inductor L2. They have a cutout shape, and their shapes are similar in appearance to each other.

The first inductor L1 and the second inductor L2 are arranged in an overlapping manner. In this embodiment, they are arranged so that their central portions overlap in the top view.

(2) Regarding the area of the overlapping region in top view Next, the area of the overlapping region in top view shown with hatching in FIG. The area is set such that the electromagnetic coupling state between the first inductor L1 and the second inductor L2 at the time of resonance with respect to the signal is in a predetermined reduced state. The reduced state refers to a state in which the electromagnetic coupling state between the first inductor L1 and the second inductor L2 at the time of resonance is sufficiently small to be ignored. The degree of electromagnetic coupling between the first inductor L1 and the second inductor L2 at the time of resonance increases or decreases depending on the area of the overlapping region when viewed from above.

Here, with reference to FIG. 5, the relationship between the area of the overlapping region when viewed from above and the degree of electromagnetic coupling will be described. For simple explanation, FIG. 5 shows a ground element 10 having two inductors L1 and L2, each of which has a rectangular shape when viewed from above, and has a predetermined area inside each other. The ground element 10 is shown arranged and configured to overlap as an overlapping region when viewed from above. The ground element 10 shown in FIG. 5 is a ground element with a conventional configuration disclosed in Patent Document 1.

For example, focusing on the magnetic flux generated in the first inductor L1 at the time of resonance, the direction of the magnetic flux generated in the first inductor L1 passing through the second inductor L2 is the first in the inner region of the second inductor L2. The portion 131 of the superimposed region in a top view that overlaps with the first inductor L1 (the hatched portion) and the portion 133 that does not overlap with the first inductor L1 (the portion surrounded by a broken line) are reversed, and each portion 131, 133 magnetic fluxes cancel each other out, and the total sum fluctuates. The same can be said about the direction of the magnetic flux generated in the second inductor L2 at the time of resonance passing through the first inductor L1. Therefore, the area of the overlapping region in a top view is set so that the magnetic fluxes of the portions 131 and 133 are equal so that the sum of the magnetic fluxes of each portion 131 and 133 becomes 0 (or equivalent to zero). If the area is set to , the electromagnetic coupling between the first inductor L1 and the second inductor L2 at the time of resonance can be brought to a substantially zero state (zero equivalent state).

The zero-equivalent state will be explained from another perspective. Generally, the magnetic flux density in an inductor is high inside the winding, and decreases outside the winding as the distance from the inductor increases. As shown in FIG. 2, in the ground element 1 of the present embodiment, the center part of the first inductor L1 and the center part of the second inductor L2 are arranged so as to overlap when viewed from above, and an overlapping area is formed when viewed from above. is the internal region of the winding in both inductor L1 and inductor L2. For example, focusing on the first inductor L1, the magnetic flux density in a portion that is an overlapping region in a top view (inside the first inductor L1) is different from a portion that is not an overlapping region in a top view (for example, an internal region of the inductor L2), The magnetic flux density is higher than that of the external region of the inductor L1. The same holds true when focusing on the second inductor L1. On the other hand, the zero-equivalent state means that, as explained with reference to FIG. 5, the sum of the respective magnetic fluxes is 0 (zero ) (or equivalent to zero). Since the magnetic flux density is high in the top-view superimposed region portion 131, in order to achieve a zero-equivalent state, it is not enough to make the area of the top-view superimposed region slightly smaller than the area of the portion that is not the top-view superimposed region. It is necessary to reduce the area of the overlapping region in top view to a specific area that provides a relative area ratio that makes the magnetic fluxes equal.

Therefore, we perform electromagnetic field analysis in advance to identify the area of the top-view superimposition region that makes the electromagnetic coupling state equivalent to zero, and ensure that the actual area of the top-view superimposition region falls within a predetermined error range with respect to the specified area. By doing so, it is possible to realize a reduced state of electromagnetic coupling.

Therefore, in this embodiment, the first inductor L1 and the second inductor L2 have unique shapes as described with reference to FIGS. 2 to 4. Then, the dimensions of the first inductor L1 and the second inductor L2 are defined so that the area of the overlapping region shown by hatching in FIG. 2 in a top view falls within the above-mentioned error range. Specifically, the width of the left and right sides (length in the left-right direction), the width of the front and rear parts (length in the front-rear direction), the depth of the notch in the left-right center part and the front-rear center, etc. stipulated. According to this, it is possible to suppress a situation where the inductors L1 and L2 are electromagnetically coupled during resonance with a transmission signal from the onboard element, and mutually influence the resonant frequency characteristics (see FIG. 3) of the respective resonant circuits 11 and 13. Therefore, it becomes possible to accurately transmit information on the combination of resonance frequencies f1 and f2 to the ground side.

Furthermore, the inductor is manufactured by pattern mounting of copper foil or the like on the substrate 15, rather than by the conventional method of manually winding electric wires. Therefore, manufacturing variations in the ground element 1 regarding the overlap width W1 can be suppressed to an error range of 5 mm or less with respect to the design width, and a high quality ground element that reliably resonates at two specific resonance frequencies f1 and f2 can be produced. Mass production can be easily and realistically realized.

FIG. 6 schematically shows the resonance frequency characteristics of the ground element 1 and the transmission signals transmitted by the onboard element to detect the resonance frequencies f1 and f2. As shown in FIG. 6, the onboard child outputs a composite signal of a predetermined frequency band f _L to f _H including a plurality of frequency components as a transmission signal. The frequency band f _L to f _H is appropriately set within the range of 50 kHz to 300 kHz. On the other hand, when the onboard element passes above, the beacon 1 simultaneously responds to the transmission signal from the onboard element at two types of resonance frequencies, a first resonant frequency f1 and a second resonant frequency f2. resonate. Therefore, on the onboard side, two types of resonance frequencies f1 and f2 with large amplitudes can be determined from the resonance frequency characteristics of the beacon 1 by analyzing the frequency signal generated in the onboard beacon when the beacon 1 resonates in response to the transmission signal. It can be detected almost simultaneously all at once.

Returning to the explanation of FIG. 1, the capacitors C1 and C2 have required capacitance values according to the corresponding resonance frequencies f1 and f2. For example, two capacitor elements corresponding to different resonance frequencies are selected from a plurality of pre-prepared types (for example, nine types) of capacitor elements with different resonance frequencies, and are mounted on the ground element 1 and connected to each inductor L1, L2. It can be used as Alternatively, a configuration may be adopted in which a plurality of types of capacitor elements are mounted on the ground element 1 and the capacitor elements are selectively connected to each of the inductors L1 and L2 via a switch that selects or combines the capacitor elements.

According to this, by changing the capacitors C1 and C2 without changing the inductors L1 and L2, it is possible to easily configure the ground element 1 that resonates at two desired resonance frequencies f1 and f2. Since the substrate 15 on which the inductors L1 and L2 are mounted can be used in common, it is advantageous in terms of manufacturing cost of the substrate 15. Therefore, the ground element 1 can transmit information indicated by the combination of different resonance frequencies f1 and f2 to the upper side of the vehicle. The total number of combinations is _{MC N} , where M types of resonance frequencies and N are the number of resonance circuits. For example, if the number of resonant circuits is two (N=2) and the number of prepared capacitor elements is nine (M=9), 36 types of information can be transmitted.

As explained above, according to the present embodiment, the first resonant circuit 11 resonates at the first resonant frequency f1 and the first resonant circuit 11 resonates at the second resonant frequency f2 in response to the transmission signal from the onboard element. It is possible to realize a ground element 1 having two resonant circuits 13. The first inductor L1 and the second inductor L2 can be arranged in an overlapping manner so that the area of the overlapping region when viewed from above becomes a predetermined area. In this embodiment, the first inductor L1 and the second inductor L2 are arranged at a position where their central portions overlap when the ground element 1 is viewed from above. Moreover, the first inductor L1 is recessed at its left and right center portions so that its length in the front and back direction is shortened, and the second inductor L2 is recessed at its front and rear center portions so that its length in the left and right direction is shortened. Concave. Therefore, even when the first inductor L1 and the second inductor L2 are arranged in an overlapping manner, the magnetic flux passing region inside the winding of the first inductor L1 and the inside of the winding of the second inductor L2 are The area of the overlapping region in top view, which is the overlapping area with the magnetic flux passing region, can be reduced. In this embodiment, the area is set to be an area where the electromagnetic coupling state between the first inductor L1 and the second inductor L2 at the time of resonance with respect to the transmission signal from the onboard element is reduced to a predetermined state. I can do it. As a result, the area of the overlapping region in top view is reduced, and an arrangement in which the central portion of the first inductor L1 and the central portion of the second inductor L2 overlap is realized. Therefore, unlike the prior art, there is no need to dispose the first inductor and the second inductor with a large shift in the sleeper direction.

That is, in the case of the beacon 10 having the conventional configuration illustrated in FIG. 5, as described above, the resonant frequency characteristics of the beacon 10 change depending on the passing position of the beacon, and the beacon 10 cannot be detected correctly on the onboard side. was there. The beacon 10 shown in FIG. 5 has a configuration in which two inductors are arranged overlapping each other with a predetermined overlap width in the left-right direction (sleeper direction) intersecting the longitudinal direction (train running direction), so the passing position of the onboard shear is If it were shifted in the left-right direction, the distance from the onboard element to the center of each inductor would change, which could result in a situation where the resonance frequency characteristics shown in FIG. 6 could not be obtained.

On the other hand, in the ground element 1 of this embodiment, the first inductor L1 and the second inductor L2 are arranged at a position where their central portions overlap when viewed from above of the ground element 1. However, since the first inductor L1 and the second inductor L2 have a unique shape, the area of the overlapping region in top view is made small, and the area between the first inductor L1 and the second inductor L2 at the time of resonance is The area can be set such that the electromagnetic coupling state of is in a predetermined reduced state. Therefore, even if the passing position of the onboard child is shifted in the direction of the sleeper due to the movement of the train, etc., the relative distance of the passing position of the onboard child with respect to each of the first inductor L1 and the second inductor L2 can be approximately Since they can be made equal, the amount of variation in the resonant frequency characteristics related to each inductor becomes approximately the same, and as a result, the ground element can be detected appropriately. Therefore, even if the passing position of the onboard child is shifted in the left-right direction (sleeper direction) and away from the center, the ground child can be properly detected on the top side of the car.

Moreover, since the information on the combination of the first resonant frequency f1 and the second resonant frequency f2 can be transmitted from the ground side to the onboard side at once, it is possible to increase the amount of information that can be transmitted by this combination, The information indicated by the combination can be reliably transmitted to the top of the vehicle all at once. While increasing the amount of information that can be transmitted, it becomes possible for the vehicle's upper side to properly detect the beacon.

Further, in the present embodiment, the first inductor L1 and the second inductor L2 have symmetrical shapes when viewed from above of the ground element 1. Therefore, the reduction characteristics of the signal level of the resonant frequency with respect to the distance between the passing position of the inductor and the center of each inductor are as follows: In either case, if the distance from the center is the same, the signal level will be the same. Therefore, the ground element 1 can be properly detected without strictly determining the horizontal direction of the ground element 1 or the installation position with respect to the rails 3, 3.

Note that the shapes of the first inductor L1 and the second inductor L2 when the ground element is viewed from above are not limited to the shapes of the above embodiments shown in FIGS. 2 to 4. For example, as shown in FIG. 7, the shape of the first inductor L1 is cut into a rectangular shape symmetrically in the front and rear, with the left and right center portions remaining in the center portion of the first inductor L1 when viewed from above of the ground element 1a. The second inductor L2 has a cutout shape (H-shape), and the shape of the second inductor L2 is cut out symmetrically in a rectangular shape at the front and rear center portions when viewed from above, leaving the center portion of the second inductor L2. It can also have a curved shape (H-shape). In addition to the mountain shape and rectangular shape, although not shown, the shape may be circular or polygonal.

Even in the shape shown in FIG. 7, the length of the first inductor L1 in the front-rear direction at the left and right center portions is shorter than the length in the front-rear direction of the left and right portions when viewed from above. Further, in the second inductor L2, when viewed from above, the length in the left-right direction at the front-rear center portion is shorter than the length in the left-right direction at the front portion and the rear portion. The first inductor L1 and the second inductor L2 are arranged at a position where their central portions overlap in the top view.

Furthermore, in FIGS. 2 and 7, an example is shown in which the first inductor L1 and the second inductor L2 are arranged in an overlapping manner at a position where their central parts (near the center) overlap, but the positional relationship between the two is The positional relationship is not limited to a positional relationship in which the center positions completely overlap in the top view, but the center positions may be slightly shifted in the top view. Specifically, it is sufficient that they are arranged in a positional relationship such that the area of the overlapping region in a top view is reduced to a predetermined state so that two types of resonance frequencies f1 and f2 with large amplitudes can be detected almost simultaneously in the onboard element. . It is preferable to arrange the recessed left and right center portions of the first inductor L1 so that part or all of the recessed front and rear center portions of the second inductor L2 overlap.

The shape is also not limited to the configuration in which the first inductor L1 has a laterally symmetrical shape and the second inductor L2 has a vertically symmetrical shape. FIG. 8 is a schematic diagram illustrating the first inductor L1 and the second inductor L2 of the ground element 1b in this modification. The shapes of the first inductor L1 and the second inductor L2 in a top view of the ground element 1b may also be shaped as shown in FIG. 8. FIG. 9 shows an extracted first inductor L1 in FIG. 8, and FIG. 10 shows an extracted second inductor L2 in FIG.

That is, the first inductor L1 and the second inductor L2 are arranged in an overlapping manner so that the area of the overlapping region when viewed from above becomes an area where a predetermined reduction state is achieved, so that two types of resonance frequencies f1, Any configuration is sufficient as long as it can detect f2 almost simultaneously. Therefore, for example, as shown in FIGS. 8 to 10, the left and right shapes of the first inductor L1 and the upper and lower shapes of the second inductor L2 may each be configured to have different asymmetric shapes.

1, 1a ground element, 11 first resonant circuit, L1 first inductor, C1 capacitor, 13 second resonant circuit, L2 second inductor, C2 capacitor, 15 substrate, f1 first resonant frequency, f2 th 2 resonant frequency, 3 rail, 5 sleeper

Claims (6)

a first resonant circuit having a first inductor and resonating at a first resonant frequency with respect to a transmission signal from the onboard element;
a second resonant circuit having a second inductor and resonating at a second resonant frequency with respect to the transmission signal;
Equipped with
The first inductor is recessed at the left and right center portions so that the length in the front and back direction is shortened when viewed from above with the train running direction as the front and back direction,
The second inductor is recessed in the front and rear central portions so that the length in the left and right direction is shortened in the top view,
the first inductor and the second inductor are arranged in an overlapping manner;
Ground child. In the first inductor, when viewed from above, the left and right center portions are recessed from both front and back directions,
The second inductor is configured such that, when viewed from above, the front and rear central portions are recessed from both left and right directions.
The ground coil according to claim 1. The first inductor and the second inductor are arranged such that their center portions overlap in the top view;
The ground coil according to claim 1 or 2. The first inductor and the second inductor have symmetrical shapes in the top view,
The ground coil according to any one of claims 1 to 3. The second inductor has a shape that satisfies a predetermined approximation condition with a shape obtained by rotating the first inductor by 90 degrees clockwise or counterclockwise when viewed from above.
The ground coil according to any one of claims 1 to 4. The area of the overlapping region of the first inductor and the second inductor in the top view is such that the electromagnetic coupling state between the first inductor and the second inductor at the time of resonance for the transmission signal is is the area that results in a predetermined reduced state,
The ground coil according to any one of claims 1 to 5.

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