PROXIMITY SENSOR

Abstract

A proximity sensor is provided that is capable of reducing the failure rate of a detection surface. The proximity sensor detects a target object. The proximity sensor comprises a detection coil, a head housing, and a power supply cable. The detection coil generates a magnetic field for detection. The head housing contains the detection coil and has a detection surface. The power supply cable is a cable connected to the head housing to supply power to the detection coil. The head housing has a connecting section that routes the power supply cable in a direction that intersects a normal direction of the detection surface to a side of the detection surface opposite that normal direction. The detection coil is positioned at a distance normal to the connecting section.

Description

BACKGROUND OF THE INVENTION 1. TECHNICAL AREA

[0001] The invention relates to a proximity sensor. 2. DESCRIPTION OF THE STATE OF THE ART

[0002] JP 2018-152320A discloses a proximity sensor. A proximity sensor described in JP 2018-152320A is powered via a power supply cable (conductor wire 6) and detects a detection object (detector 700) near a detection surface (detection surface 5a). In the proximity sensor described in JP 2018-152320A, a body section is attached to a support element when the proximity sensor is in use. The nuts 7 and 8 disclosed in JP 2018-152320A serve to attach the body section to the support element, and the body section is attached to the support element by clamping a fastening device between the nuts 7 and 8. The fastening device can be considered part of the support element. The following description of JP 2018 - 152 320 A refers to the detection area (detection area 5a) of the body section (left side in the drawing of Fig. 4 of JP 2018 - 152 320 A) designated as the front, and one side of the power supply cable (conductor wire 6) of body section 5 (right side in the drawing of Fig. 4 of JP 2018 - 152 320 A) is referred to as the reverse side.

[0003] The proximity sensor described in JP 2018 - 152 320 A requires sufficient space to arrange the power supply cable (the conductor wire 6) behind a structure (the body section 5) that includes the detection area (detection area 5a).

[0004] In a case where there is insufficient space behind the support element to which the structure (body section 5) is attached, the proximity sensor described in JP 2018 - 152 320 A must be positioned relatively close to the front to ensure sufficient space for the arrangement of the power supply cable behind the structure or assembly.

[0005] The support element is often positioned in a fixed relationship to the path of the object detected by the proximity sensor, such that the detection surface (detection surface 5a) of the proximity sensor, which is located relatively close to the front, lies close to the path of the object detected (detection body 700). Accordingly, there is a risk that the support element will be damaged by a collision with the object detected (detection body 700). SUMMARY OF THE INVENTION

[0006] The invention was made in light of the problems described above, and its aim is to provide a proximity sensor that can reduce the failure of a detection surface.

[0007] A proximity sensor according to one embodiment of the invention detects a detection object. The proximity sensor comprises a detection coil, a head housing, and a power supply cable. The detection coil generates a magnetic field for detection. The head housing accommodates the detection coil and has a detection surface. The power supply cable is connected to the head housing to supply power to the detection coil. The head housing has a connecting section that guides the power supply cable in a direction that intersects a normal direction of the detection surface on a side opposite the detection surface. The detection coil is positioned at a distance from the connecting section in the normal direction.

[0008] According to the proximity sensor of the invention, it is possible to reduce the failure or breakdown of the detection surface. BRIEF DESCRIPTION OF THE FIGURES Fig. Figure 1 is a schematic diagram of the structure of a proximity sensor; Fig. Figure 2 is a perspective view of an L-shaped proximity sensor; Fig. Figure 3 is a perspective view of a cylindrical proximity sensor; Fig. Figure 4 is a perspective view of a flat proximity sensor; Fig. Figure 5 is a longitudinal section view of the L-type proximity sensor; Fig. Figure 6 is an enlarged perspective view of a longitudinal section of a front section of a head housing; Fig. Figure 7 is a double logarithmic graph with a horizontal axis and a vertical axis of penetration depth versus frequency and a schematic view or legend to explain the double logarithmic graph; Fig. Figure 8 is a perspective view of a longitudinal section of the head housing; Fig. Figure 9 is an enlarged perspective view showing a detection coil and a device connected to the detection coil; Fig. Figure 10A is a diagram representing a picture of a received waveform that has been subjected to zero matching or zero adjustment when no external element is present and no detection object is within a detection range; Fig. Figure 10B is a diagram representing an image of a received waveform that has been zeroed when no external element is present and the object being detected is within the detection range; Fig. 11A is a diagram that represents an image of a received waveform that has been subjected to zero matching when an external element is present and the detection object is not within the detection range; Fig. Figure 11B is a diagram that represents an image of a received waveform that has undergone zero-point correction when an external element is present and the object being detected is within the detection range; Fig. Figure 12 is a partially cropped perspective view of the cylindrical proximity sensor; and Fig. Figure 13 is an enlarged perspective view of a longitudinal section of the flat proximity sensor. DETAILED DESCRIPTION

[0009] The following describes embodiments of the invention with reference to the drawings. It should be noted that identical or corresponding parts are designated with the same reference numerals in the drawings and their descriptions are not repeated.

[0010] The following description may use terms that denote positions or directions, such as "front" and "back". These terms are used for the sake of simplicity to facilitate understanding of the embodiments and do not refer to directions in which actions are actually performed, unless expressly stated otherwise.

[0011] In the following, a proximity sensor 100 according to an embodiment of the invention is described with reference to the drawings. First, based on the Fig. 1. An overview of the proximity sensor 100 is given. Fig. Figure 1 is a schematic diagram of the proximity sensor 100. Fig. Figure 1 shows arrows X, Y, and Z, indicating three mutually orthogonal directions. The directions indicated by arrows X, Y, and Z all correspond to the arrangement of proximity sensor 100, where the direction indicated by arrow X is called the X-axis direction, the direction indicated by arrow Y is called the Y-axis direction, and the direction indicated by arrow Z is called the Z-axis direction. One of the directions along the X-axis is called the +X direction, the other the -X direction. One of the directions along the Y-axis is called the +Y direction, the other the -Y direction. One of the directions along the Z-axis is called the +Z direction, the other the -Z direction.

[0012] The proximity sensor 100 is a sensor that detects the presence or absence, or the position, of a detection object D. As in Fig. As shown in Figure 1, the proximity sensor 100 comprises a head 100H, an amplifier 100A, and a power supply cable 2 connecting the head 100H and the amplifier 100A. The head 100H includes a detection coil 1 and a head housing 3 that accommodates the detection coil 1. The amplifier 100A comprises a transmitter circuit 5, a receiver circuit 6, a control circuit 7, an amplifier board 70 on which the transmitter circuit 5, the receiver circuit 6, and the control circuit 7 are provided, and an amplifier housing 8 that accommodates the amplifier board 70.

[0013] The detection coil 1 generates a magnetic field for detection. The power supply cable 2 supplies power to the detection coil 1, which is powered by a power source (not shown) via the power supply cable 2. The head housing 3 accommodates the detection coil 1. The head housing 3 is arranged such that a normal direction of a detection surface 30, to be described later, runs along the Y-axis direction, and the detection surface 30 points towards the +Y direction. The head housing 3 of the present embodiment has a shape whose longitudinal direction runs along the Y-axis direction and includes a connecting section 34 that guides the power supply cable 2 towards the -Y direction.

[0014] The transmitting circuit 5 supplies the detection coil 1 with a pulsed excitation current. The receiving circuit 6 detects a detection current generated in the detection coil 1. Based on a received signal from the receiving circuit 6, which has detected the current, the control circuit 7 detects the presence, absence, or position of the detection object D. Since the detection current changes according to a change in the magnetic field, the change in the magnetic field is reflected in the received signal of the receiving circuit 6. The control circuit 7 outputs a result indicating the presence, absence, or position of the detection object D.

[0015] The transmitting circuit 5, the receiving circuit 6, and the control circuit 7 are implemented on the amplifier board 70. The power supply cable 2 electrically connects the detection coil 1 and the amplifier board 70. Although the transmitting circuit 5, the receiving circuit 6, and the control circuit 7 are implemented on the amplifier board 70 in the present embodiment, at least the control circuit 7 can be implemented elsewhere. For example, a board on which the transmitting circuit 5 and the receiving circuit 6 are implemented can be housed in the head housing 3.

[0016] The head housing 3 comprises a detection surface 30, which is arranged at an end section of the head housing 3 on the side of the +Y direction, and a head cylinder section 32 with a circumferential shape whose centerline runs along the Y-axis direction. The head cylinder section 32 has a mounting section 31. The fixed section 31 is provided between the connecting section 34 and the detection surface 30 in the Y-axis direction and is a section to which a fastening element such as a nut (not shown) is attached when the head housing 3 is attached to an external element E.

[0017] The amplifier housing 8 accommodates the amplifier board 70. The amplifier housing 8 is located outside the head housing 3.

[0018] In general, a proximity sensor that uses an induced current has a short detection range, meaning that if the object deviates from its assumed path, it will collide with the object being detected (D). Therefore, if the proximity sensor uses an induced current and has a long detection range, the risk of collision with the object is reduced. The proximity sensor 100, which utilizes induced current, includes a sinusoidal type, in which a sinusoidal excitation current is applied to the detection coil 1, and a pulsed type, in which a pulsed excitation current is applied to the detection coil 1. Both types detect changes in the current generated in the detection coil 1; however, the change in current becomes weaker as the distance between the object being detected (D) and the detection coil 1 increases.This means that to achieve a large detection range, even a small change must be detected, but with the sinusoidal type, it is difficult to distinguish between the detection object D and another metal body (external element E) other than the detection object D. With the type where the pulsed excitation current is applied to the detection coil 1, the received signal, which is synchronized with the excitation current, can be a signal with a characteristic change along a time axis, starting from the excitation point, thus providing more information than with the sinusoidal type.For example, it is possible to perform a calculation using an attenuation time from a peak value of the received signal to distinguish between the detection object D and the metal body that is not the detection object D, or to perform processing by comparing the time axes of a multitude of received signals generated in a multitude of detection coils 1. Thus, the pulse type has the advantage that the detection accuracy can be improved by calculation compared to the sine type. The proximity sensor 100 of the present embodiment is a pulse-type proximity sensor in which the pulsed excitation current is supplied to the detection coil 1. The pulse type requires complex processing, such as controlling the application time of the pulsed excitation current to the coil and processing a current generated in the coil.In order to achieve a large detection range, a control circuit 7 is therefore required when detecting the detection object D by the pulse type, which performs relatively complicated procedures, making the amplifier board 70, on which the control circuit 7 is implemented, large.

[0019] Accordingly, the proximity sensor 100, according to the present embodiment, can reduce the size of the head housing 3 while simultaneously achieving a large detection range by housing the amplifier board 70 separately from the head housing 3 within the amplifier housing 8. In particular, since a dimension in the Y-axis direction can be reduced, the proximity sensor 100 can also be positioned in the present embodiment even when there is insufficient installation space in the Y-axis direction with respect to the external element E.

[0020] As in Fig. Figure 1, shown enlarged, shows the power supply cable 2 comprising a core wire 21 through which the detection current flows, and a shielding sleeve 20 that surrounds the core wire 21 with a shield. The shielding sleeve 20 is electrically connected to an electrical shield 43, which will be described later. Note that the shielding sleeve 20 and the electrical shield 43 can be electrically connected, either directly or indirectly. Since the core wire 21, through which the detection current flows, is covered by the shielding sleeve 20, the change in the detection current is hardly influenced from the outside. As explained above, the change in the detection current is weaker the greater the distance between the object being detected D and the detection coil 1.In such a case, in particular, the detection accuracy of the object D, which is located at a greater distance from the detection coil 1, is improved by using a configuration in which the detection current is hardly affected by the environment. Accordingly, the detection accuracy of the proximity sensor 100 is improved by the configuration in which the core wire 21 is shielded.

[0021] The amplifier 100A includes a display unit 9 (for example, an indicator lamp) that displays a result output by the control circuit 7. The display unit 9 is located on the front of the amplifier housing 8. The display unit 9 is positioned on the front of the amplifier housing 8 so that a user can easily perceive the detection result from the proximity sensor 100 by visually locating the amplifier housing 8.

[0022] The head cylinder section 32 is made of metal, and a portion of it is formed as the mounting section 31. Mounting section 31 has a circumferential threaded groove with the Y-axis direction as its centerline. External element E has a screw hole into which a threaded groove is cut to match the threaded groove formed in mounting section 31. If mounting section 31 is a screw, the screw hole in external element E is a nut thread. External element E and mounting section 31 are fastened by screwing them together. Once external element E and mounting section 31 are screwed together, a nut (not shown) can be screwed onto mounting section 31 to further stabilize the positional relationship between external element E and the head housing 3 in the Y-axis direction.In particular, if the head housing 3 is arranged such that it does not project in the direction of the +Y side with respect to the external element E, i.e., on the side of the path of the detection object D in the Y-axis direction, the external element E and the mounting section 31 are often fastened by screws. Therefore, the nut is preferably attached to the mounting section 31, which is positioned on the -Y-direction side with respect to the external element. Note that in the present embodiment, the screw bore is provided in the external element E, and the head housing 3 is fastened to the external element E by screwing the mounting section 31 into the screw bore.In a state in which the head housing 3 is arranged in a through-hole provided in the external element E, the head housing 3 can be constructed such that it is attached to the external element E by arranging the external element E between a nut screwed onto the fastening section 31 on the -Y side relative to the external element E and a nut screwed onto the fastening section 31 on the +Y side relative to the external element E.

[0023] Accordingly, the metallic mounting section 31 is the threaded groove, and thus the proximity sensor 100 can be easily attached to the external element E. In the present embodiment, the threaded groove is provided in the mounting section 31, but can be made of metal, so that the positional relationship between the external element E and the head housing 3 is stabilized when the head housing 3 is attached to the external element E. The head housing 3 can be attached to the external element E by attaching a clamp to the metallic mounting section 31 and then attaching the clamp to the external element E.

[0024] The following describes variants of the proximity sensor 100 based on the Fig. 2, Fig. 3 to Fig. 4 described. Fig. Figure 2 is a perspective view of an L-type proximity sensor 100. Fig. Figure 3 is a perspective view of a cylindrical proximity sensor 100. Fig. Figure 4 is a perspective view of a flat-type proximity sensor 100.

[0025] The in Fig. The proximity sensor 100 shown in Figure 2 is also referred to as an L-type because a side view of the structure with the detection surface 30, which is the head housing 3 of the head 100H including the detection coil 1 (not shown), is L-shaped. Since the structure with the detection surface 30 is cylindrical, the Fig. Proximity sensor 100, also known as cylinder type, is shown in Figure 3. The sensor is located in... Fig. The proximity sensor 100 shown in Figure 4 is also referred to as a flat type, since the structure with the detection surface 30 is box-shaped (has a flat surface).

[0026] Everyone in the Fig. 2, Fig. 3 to Fig. The type of proximity sensor 100 shown in Figure 4 comprises the head housing 3, which forms the assembly with the detection surface 30, and the amplifier housing 8, which is separate from the head housing 3. As shown in the Fig. 2 and Fig. As shown in Figure 3, the head housing 3 of the L-type proximity sensor 100 and the cylinder-type proximity sensor 100 comprises the detection surface 30 and a columnar head cylinder section 32 with a normal direction to the detection surface as its center line. The head housing 3 of the L-type proximity sensor 100 and the head housing 3 of the cylinder-type proximity sensor 100 have elongated shapes, such that the axial direction of the head cylinder section 32 is the longitudinal direction. On the other hand, the flat proximity sensor 100, as shown in Figure 3, comprises the detection surface 30 and a columnar head cylinder section 32 with a normal direction to the detection surface as its center line. Fig. Figure 4 shows a box-shaped head housing 3B, and the head housing 3B has the detection surface 30.

[0027] The following section describes the L-shaped proximity sensor 100 based on the Fig. 5, Fig. 6, Fig. 7, Fig. 8 to Fig. 9 described. First, the L-shaped proximity sensor 100 is described using the following: Fig. 5 described in detail. Fig. Figure 5 is a longitudinal section view of the L-shaped proximity sensor 100.

[0028] As in Fig. As shown in Figure 5, the proximity sensor 100 comprises the detection coil 1, the power supply cable 2 and the head housing 3.

[0029] The detection coil 1 generates a magnetic field for detection. The power supply cable 2 supplies power to the detection coil 1. The head housing 3 accommodates the detection coil 1. The head housing 3 is arranged such that the normal direction of the detection surface 30 runs along the Y-axis and the detection surface 30 points towards the +Y direction. The head housing 3 of the present embodiment has an elongated shape, the longitudinal direction of which runs along the Y-axis, and includes the connecting section 34, which guides the power supply cable 2 towards the -Y direction.

[0030] The head housing 3 has the metallic detection surface 30 on the +Y-direction side of the head housing 3. Since the detection coil 1 is located near the detection surface 30, the detection coil 1 is also located on the +Y-direction side of the head housing 3. The head housing 3 has an elongated shape in the Y-axis direction, and the detection coil 1 is positioned such that a -Y-direction-side end section of the detection coil 1 is positioned relative to the connecting section 34 on the +Y-direction side; thus, the detection coil 1 and the connecting section 34 are spaced apart from each other in the Y-axis direction.

[0031] The connecting section 34 is located on the -Y direction side of the head housing 3 and guides the power supply cable 2 in the -Z direction.

[0032] For the sake of simplicity, the side of the -Y direction of the head housing 3 can be referred to as an end side of the head housing 3 in the longitudinal direction, and the +Y direction can be referred to as an end side of the head housing 3 in the longitudinal direction, i.e., as the side of the detection surface 30. Furthermore, the -Y direction can be referred to as the back and the +Y direction as the front.

[0033] The in Fig. The head housing 3 shown in Figure 5 has a shape in which the connecting section 34 guides the power supply cable 2 in the -Z direction, and thus the head housing has an L-shape in the side view (viewed in the X-axis direction). That is, the connecting section 34 does not extend backwards along the Y-axis direction, which is the normal direction of the detection surface 30, but in a direction that intersects a forward-backward direction (longitudinal direction), which is the Y-axis direction.

[0034] Thus, the L-shaped proximity sensor 100, in which the head housing 3 is L-shaped, is suitable in a case where there is an obstacle behind the head housing 3. This is because, compared to the proximity sensor 100 where the head housing 3 is not L-shaped, the head housing 3, when attached to the external element E, hardly affects the obstacle positioned behind the external element E. However, if the distance between the external element E and an obstacle arranged in the Y-axis direction (i.e., in the forward-backward direction) relative to the external element E is short, the head 100H must also be positioned close to the side in the +Y-axis direction (front) of the L-shaped proximity sensor 100.Since the head housing 3 is positioned such that the detection surface 30 of the head housing 3 is closer to the path of the detection object D, the possibility of a collision between the detection object D and the detection surface 30 increases. Here, the detection surface 30, which can collide with the detection object D, is made of metal, thus increasing its strength. This makes a failure of the head 100H due to a collision with the detection object D less likely. Consequently, the proximity sensor 100H achieves both a degree of freedom in its arrangement, allowing it to be installed even in an environment where the obstacle is located behind the external element E, and reduces the failure rate of the head 100H.

[0035] Note that in the present embodiment, the connecting section 34 is designed to guide the power supply cable 2 in the -Z direction, but it can also be designed to guide the power supply cable 2 in a direction that intersects the normal direction of the detection surface 30. Furthermore, the direction in which the power supply cable 2 is guided through the connecting section 34 is preferably closer to the Y-axis direction, i.e., a direction orthogonal to the longitudinal direction (forward-backward direction). Accordingly, it becomes less likely that the head housing 3 will interact with the obstacle located behind the head housing 3.

[0036] Next, the head housing 3 of the proximity sensor 100 will be examined using… Fig. 6 described in detail. Fig. Figure 6 is a perspective view of a longitudinal section of a point (other end section) on the +Y-direction side of the head housing 3. In Fig. For the sake of simplicity, components other than the detection coil 1 in the head housing 3 have been omitted.

[0037] As in Fig. As shown in Figure 6, the head housing 3 comprises the head cylinder section 32 (body section) made of metal and a cap section 35 made of metal. The head cylinder section 32 is a cylindrical element with a circumferential surface on one circumference, the centerline of which runs along the Y-axis direction, and with an opening towards the +Y direction. The cap section 35 is attached to the head cylinder section 32 to cover the opening of the head cylinder section 32 from the +Y-direction side (front side) of the head cylinder section 32. The cap section 35 attached to the head cylinder section 32 is positioned on a front side of the head housing 3. The cap section 35 includes the detection surface 30 made of metal.

[0038] Since the cap section 35, which is separate from the head cylinder section 32, includes the detection surface 30, the head cylinder section 32 has a shape in which not only a rear end but also a front end of the head cylinder section 32 is open. Accordingly, an inner circumferential surface of the head cylinder section 32 can be cut (thinned) from both end faces of the front end face and the rear end face. Compared to the design in which the detection surface 30 is integral with the head cylinder section 32, the manufacturing difficulty is reduced because cutting can be performed from both end faces in the Y-axis direction.

[0039] More precisely, cutting (milling) is generally carried out by inserting a drill bit, which is a cutting blade, into the head cylinder section 32 while rotating the drill bit. The longer the drill bit, the greater the deflection of the drill tip.

[0040] In the setup where the detection surface 30 is formed integrally with the cylindrical head section 32, the drill bit is inserted only from the rear end face of the cylindrical head section 32. For this reason, a long drill bit must be used to cut the front end region of the cylindrical head section 32, resulting in a large deflection of the drill tip. Consequently, it is difficult to maintain the accuracy of the cutting (thinning) at the front end region of the cylindrical head section.

[0041] Since the front end section of the head cylinder is where the detection coil 1 is located, high precision is required for cutting (thinning). Accordingly, the manufacturing effort is high in the head cylinder section where only the rear end section is open.

[0042] On the other hand, in the setup where the cap section 35 containing the detection surface 30 is separate as in the one described in Fig. As depicted in Figure 6, a rotating drill is inserted from both ends of the front and rear end sections of the head cylinder section 32. Thus, the drill can be inserted from the front of the head cylinder section 32 even if the front of the head cylinder section 32 has already been cut. Since the cutting can be achieved by selecting a relatively short drill bit with slight vibration at the tip of the rotating drill, the cutting (thinning) accuracy is improved. Consequently, the head housing 3 of the proximity sensor 100 encloses the detection surface 30 and the cap section 35 separately from the head cylinder section 32, leaving the front and rear end sections of the head cylinder section 32 open. This reduces manufacturing effort.

[0043] The head cylinder section 32 has a stop section 33 on its inner circumferential surface. When suitably attached to the head cylinder section 32, the stop section 33 abuts the cap section 35. The cap section 35 is attached to the head cylinder section 32 with an adhesive while resting against the stop section 33.

[0044] Since the cap section 35 can be easily attached to the head cylinder section 32 in a suitable manner, the level of difficulty in manufacturing the proximity sensor 100 is reduced.

[0045] The stop section 33 is a circumferential groove with a predetermined width extending from an end section on the +Y side (front side) of the head cylinder section 32 towards the -Y side (rear side) on the inner circumferential surface of the head cylinder section 32. The predetermined width of the circumferential groove corresponds to a dimension of the cap section 35 attached to the head cylinder section 32 in the Y-axis direction (forward-backward direction). The inner diameter of the circumferential groove is slightly larger (by the amount of the gap into which the adhesive penetrates) than the outer diameter of the cap section 35. Accordingly, the circumferential groove forming the stop section 33 serves to position the cap section 35.

[0046] The cap section 35 has a base section 36 with the detection surface 30 and a circumferential section 37 that extends upwards from an outer circumferential edge of the base section 36. In a state where the cap section 35 is attached to the head cylinder section 32, one end (the rear end of the circumferential section 37) of the circumferential section 37 is positioned on the side in the -Y direction (side of the connecting section 34) on the side in the +Y direction, i.e., on the front side relative to one end of the detection coil 1 (rear end 56 of the detection coil 1) on the -Y direction side (side of the connecting section 34).

[0047] Since the cap section 35 is no longer than necessary in the forward-backward direction, the difficulty level of cutting the cap section 35 itself hardly increases. Accordingly, the difficulty level of manufacturing the proximity sensor 100 is reduced.

[0048] In the head cylinder section 32, there is a section that includes an end of the detection coil 1 on the side of the -Y direction (side of the connecting section 34), i.e., a section on the side in the +Y direction relative to a rear end 56 of the detection coil 1 (front section), a thinner section that is thinner than other sections.

[0049] Because the head cylinder section 32 is relatively thin around the outer circumference of the detection coil 1, the magnetic field of the detection coil 1 is hardly obstructed by the head cylinder section 32. Since the head cylinder section 32 also has a relatively thick section on its outer circumferential side in the -Y direction with respect to the detection coil 1, the strength of the head cylinder section 32 can be easily maintained. This allows the proximity sensor 100 to improve its detection accuracy while maintaining its mechanical strength. Furthermore, because the head cylinder section 32 and the cap section 35, which encompasses the detection area 30, are spaced apart, the difficulty of machining the section of the head cylinder section 32 thinning on the +Y side, where the cap section 35 is attached, is reduced.Furthermore, an inner circumference of the end section of the head housing 3 on the +Y direction side is used to position the detection coil 1. The positional accuracy of the detection coil 1 relative to the head housing 3 has a significant influence on the detection range based on the detection area 30. Therefore, if the end section of the head housing 3 on the +Y direction side can be processed with high accuracy using the setup where the head cylinder section 32 and the cap section 35 are spaced apart, the detection range of the proximity sensor 100 can be increased.

[0050] The detection coil 1 preferably generates a magnetic field with an effective frequency of 2 kHz or more and 200 kHz or less. A section comprising the detection area 30 preferably has a thickness of 1.0 mm or less.

[0051] Next, with reference to Fig. 7 the reason for the preferred effective frequency (2 kHz or more and 200 kHz or less) of the magnetic field and the preferred thickness (1.0 mm or less) of the section comprising the detection area 30 is described in detail. Fig. Figure 7 is a double-logarithmic graph with a horizontal axis and a vertical axis of penetration depth versus frequency and a schematic view to explain the double-logarithmic graph.

[0052] As in the double-logarithmic graph of Fig. As shown in Figure 7, the penetration depth decreases as the frequency increases. In other words, the lower the frequency, the greater the penetration depth. Since penetration depth represents the distance over which a magnetic flux line of a given intensity is attenuated to a specific intensity in the direction of an element made of a particular material, the attenuation becomes more difficult as the frequency decreases, and the penetration depth increases. The more easily the magnetic flux line can penetrate the element, the less easily the magnetic flux line is attenuated, and the greater the penetration depth.

[0053] To reduce the attenuation of the magnetic flux by the metal detection surface 30, it is advantageous to generate a magnetic field with a low frequency. However, if the frequency of the generated magnetic field is low, it is difficult to detect a change in the magnetic field as the magnetic flux passes through the detection object D, and there is a risk that the detection object will be reduced or barely detected.

[0054] On the other hand, the pulse type or the relatively low-frequency sine-sine type generally has an effective frequency of 200 kHz or less. In a case where the upper limit of the effective frequency is 200 kHz, that is, in a case where the frequency is 200 kHz (point B in Fig. 7) or less, the penetration depth of stainless steel (SUS304) exceeds 1 mm. Accordingly, in a case where the section comprising the detection surface 30 is made of stainless steel (SUS304) with relatively high mechanical strength, both the mechanical strength and the reduction of magnetic flux attenuation due to the element forming the detection surface 30 can be achieved with an upper limit of 1 mm thickness. Note that in the present embodiment SUS304 is used as the stainless steel, but the stainless steel is not limited to SUS304 and another stainless steel can also be used.

[0055] Next, we will use the following as an example: Fig. 8 describes a filler with which the head housing 3 is filled. Fig. Figure 8 is a perspective view of a longitudinal section of the head housing 3. Fig. In Figure 8, the representation and reference numbers of the filling material have been omitted for the sake of clarity, but the filling material is filled into an area specified as a space within the head housing 3.

[0056] As in Fig. As shown in Figure 8, the proximity sensor 100 comprises the detection coil 1, the power supply cable 2 and the metallic head housing 3, and the head housing 3 is filled with the filler.

[0057] The detection coil 1 generates a magnetic field for detection. The power supply cable 2 supplies power to the detection coil 1. The head housing 3 is made of metal and contains the detection coil 1. The head housing 3 is filled with filler, and the filler is filled to fill the circumference of the detection coil 1 housed within the head housing 3. The filler consists of an adhesive and an additive with a relative dielectric constant lower than that of the adhesive.

[0058] The proximity sensor 100 is a sensor that detects the detection object D, which is a metal body, using an induced current. The presence or absence and the position of the detection object D are detected based on the change in the detection current generated in the detection coil 1. The greater the distance between the detection coil 1 and the detection object D, the weaker the change in the detection current. Therefore, to increase the detection range of the proximity sensor 100, it is necessary to detect even a small change in the detection current. If an interference current is added to the detection current, there is a risk that the detection accuracy will decrease, even if the interference current is weak.

[0059] Since the detection coil 1 is powered via the power supply cable 2, the power supply cable 2 is electrically connected to the detection coil 1. Therefore, the power supply cable 2 can be a path through which the interference current flows, affecting the change in the detection current of the detection coil 1.

[0060] The external element E, to which the head housing 3 is attached, is frequently grounded to a ground G. This is because, in the present embodiment, the external element E is often part of a device containing the proximity sensor 100, and such a device is frequently connected to ground G for safety reasons. Therefore, in many cases, the head housing 3 attached to the external element E is grounded to ground G, and any current generated within the head housing 3 itself flows to ground G. When the head housing 3 is grounded, the power supply cable 2 and the head housing form a circuit via ground G, and there is a risk of interference current flowing from the power supply cable 2 into the head 100H. Therefore, it is advantageous to minimize the capacitive coupling between the head housing 3, the power supply cable 2, and any circuit from the power supply cable 2 to the detection coil 1. For example, air may be present.

[0061] The head housing 3 is filled with filler to improve its mechanical strength. There is a risk that the capacitive coupling of the filler will cause current to flow between the head housing 3 and the circuit between the power supply cable 2 and the detection coil 1. That is, due to the capacitive coupling of the filler, the power supply cable 2, the circuit between the power supply cable 2 and the detection coil 1, and the head housing 3 form a circuit via ground G, creating a risk of interference current flowing from the power supply cable 2 into the head 100H. If this interference current affects the change in the detection current flowing through the detection coil 1, there is a risk that the accuracy of the detection by the proximity sensor 100 will decrease.

[0062] The proximity sensor 100 of the present embodiment has a relative dielectric constant that is lower than in a case where the filler material to be filled contains only an adhesive. Therefore, there is hardly any capacitive coupling between the head housing 3 and the circuit between the power supply cable 2 and the detection coil 1. Accordingly, hardly any interference current flows into the head 100H. Consequently, the proximity sensor 100 can achieve both mechanical strength through the filler material and detection accuracy. Note that in the present embodiment, the head housing 3 is filled with the filler material, but this is not limited to the entire head housing 3. Only the section on the +Y-direction side, including the detection coil 1, can be filled within the head housing 3.Furthermore, it is not necessary to fill the entire head housing 3 circumferentially with the Y-axis as the center line; only an interior space including the detection coil 1 can be filled. In this case, an air gap may exist between the filled area and the head housing 3.

[0063] The filler material has a relative permittivity of 3.7 or less. Because the relative permittivity of the filler material is 3.7 or less, there is virtually no capacitive coupling between the head housing 3 and the circuit between the power supply cable 2 and the detection coil 1. Consequently, the proximity sensor 100 can reduce the decrease in detection accuracy due to noise incoming from the power supply cable 2.

[0064] The interior of the head housing 3 comprises a first chamber containing the detection coil 1 in the Y-axis direction, and a second chamber that does not contain the detection coil 1 and is located on the -Y-axis side relative to the first chamber. A filler material placed in the first chamber has a relative dielectric constant that is lower than that of a filler material placed in the second chamber.

[0065] That is, if the filler placed in the first chamber is a first filler and the filler placed in the second chamber is a second filler, the relative dielectric constant of the first filler is lower than the relative dielectric constant of the second filler.

[0066] In such a setup, capacitive coupling between the circuit between the power supply cable 2 and the detection coil 1 and the head housing 3 readily occurs in the second space filled with the second packing material, i.e., in the space that does not contain the detection coil 1. Accordingly, even when the circuit including the power supply cable 2, the head housing 3, and ground is complete, the current readily flows through the path of the second space that does not contain the detection coil 1. Consequently, even if the interference current enters the head housing 3 from the power supply cable 2, it barely flows near the detection coil 1. Therefore, the influence of the interference current flowing from the power supply cable 2 on the detection current is reduced.Furthermore, since a material for the second filling can be selected with priority given to hardness over the relative dielectric constant, the durability of the entire head can be improved to 100H.

[0067] The head housing 3 has the detection surface 30, which is a surface for detecting the detection object D. An end section of the second chamber on the +Y-direction side is filled with the first filler and the second filler, which are arranged with respect to the end (rear end) 56 in the -Y-axis direction of the detection coil 1 on the -Y-axis side (rear side).

[0068] Accordingly, the interference current, even if it enters from the power supply cable 2, hardly flows near the detection coil 1. Therefore, the influence of the interference current flowing from the power supply cable 2 on the detection current is reduced.

[0069] The proximity sensor 100 further comprises a conductive electrical shield 43. The electrical shield 43 covers the detection coil 1 circumferentially with the Y-axis direction as its center line. One end on the +Y-direction side of the second chamber is filled with the first filler and the second filler, which are arranged on the -Y-direction side (rear end) 54 of the electrical shield 43 with respect to an end on the -Y-direction side (rear end).

[0070] The electrical shield 43 is designed to prevent external interference with the detection coil 1. Therefore, the electrical shield 43 is positioned such that the detection coil 1 is adequately covered in the Y-axis direction. Accordingly, a boundary between the first and second chambers is positioned on the -Y-direction side relative to the -Y-direction-side end of the electrical shield 43, resulting in a long distance between the detection coil 1 and the boundary between the first and second chambers in the Y-axis direction. Consequently, the influence of the interference current coming from the power supply cable 2 on the detection current is reduced.

[0071] The space filled with the packing material in the head housing 3 is subdivided in the Y-axis direction into a front space 51, a middle space 52, and a rear space 53. The front space 51 is a space on the front (+Y-direction) with respect to the rear end 56, which is the end of the detection coil 1 in the -Y-direction within the head housing 3. The middle space 52 is a space on the back (-Y-direction) with respect to the rear end 56 of the detection coil 1 and on the front (+Y-direction) with respect to the rear end 54, which is the -Y-direction end of the electrical shield 43 within the head housing 3. The rear space 53 is a space on the back (-Y-direction) with respect to the rear end 54 of the electrical shield 43 within the head housing 3.

[0072] For example, the front chamber 51 is filled with the first filler, and the middle chamber 52 and the rear chamber 53 are filled with the second filler. In this case, the first chamber is the front chamber 51, and the second chamber is the middle chamber 52 and the rear chamber 53. That is, the boundary between the first chamber and the second chamber is a boundary 56 between the front chamber 51 and the middle chamber 52.

[0073] As another example, the front chamber 51 and the middle chamber 52 are filled with the first filler, and the rear chamber 53 with the second filler. In this case, the first chamber is the front chamber 51, and the middle chamber 52 and the second chamber form the rear chamber 53. That is, the boundary between the first chamber and the second chamber is a boundary 54 between the middle chamber 52 and the rear chamber 53.

[0074] The filler is a mixture of an adhesive and an additive. The adhesive is based, for example, on silicone, urethane, or polyethylene. The additive has a relative dielectric constant that is lower than that of the adhesive. Examples of additive materials include at least one of fluorine, polyimide, chlorine, polyethylene, acrylic, urethane, boron nitride, air, and vacuum filler or aerogel. Examples of additive forms include platelet-shaped primary particles, agglomerated granules, and flakes.

[0075] The Shore hardness after curing of the filler is preferably D0 or higher, preferably D80 or higher. This is because the Shore hardness after curing of the filler is D80 or higher, thus sufficiently improving the mechanical strength of the proximity sensor 100.

[0076] The proximity sensor 100 can further comprise an element 46 that fixes the head board 13 within the head cylinder section 32. The proximity sensor 100 can stabilize the assembly by means of the element 46, which fixes the head board 13 within the head cylinder section 32.

[0077] Details of detection coil 1 are described below using the following examples: Fig. 9 described. Fig. Figure 9 is an enlarged perspective view showing the detection coil 1 and a device connected to the detection coil 1. Fig. 9 are structures used to describe Fig. Numbers 9 are not required and have been omitted for the sake of clarity.

[0078] As in Fig. As shown in Figure 9, the detection coil 1 comprises a coil wire 1L. The power supply cable 2 has a core wire 21. The proximity sensor 100 also includes the head board 13. The head board 13 is housed in the head casing 3 and extends along the longitudinal direction (forward-backward direction). A circuit that electrically connects the coil wire 1L and the core wire 21 is provided in the head board 13. That is, the head board 13 can be described as an element that electrically connects the coil wire 1L and the core wire 21.

[0079] Since both the coil wire 1L and the core wire 21 are flexible linear elements, handling them during assembly is complicated. Because the coil wire 1L and the core wire 21 are housed in the head housing 3 via the head board 13, which has a certain degree of rigidity, the assembly of the proximity sensor 100 is easier to stabilize.

[0080] The proximity sensor 100 further comprises a ferrite core 23 and a core holder 24. The coil wire 1L is wound around the ferrite core 23. The core holder 24 holds the ferrite core 23. The head board 13 is attached to the core holder 24. In a case where the ferrite core 23 and the head board 13 are not fixed to each other and are free to move, there is a risk that a load will be exerted on the coil wire 1L and that the coil wire 1L will be severed by a certain amount or more at the time of assembly due to the separation of the ferrite core 23 and the head board 13. Since the ferrite core 23 and the head board 13 are fixed via the core holder 24, the risk of the coil wire 1L being severed during assembly is reduced.

[0081] The coil wire 1L comprises first coil wires 11L and second coil wires 12L, which are distinct from the first coil wires 11L. The detection coil 1 comprises a first coil 11, around which the first coil wires 11L are wound, and a second coil 12, around which the second coil wires 12L are wound outside the first coil 11. Note that two first coil wires 11L extend from the first coil 11, with one first coil wire 11L being connected to a surface of the head board 13 on the +Z direction side, as shown in Fig. 9 shown, and the other first coil wire 11L is connected to a surface of the head board 13 on the -Z direction side. In the present embodiment, the two first coil wires 11L are connected to different surfaces of the head board 13, but can also be connected to the same surface. Additionally, there are two second coil wires 12L extending from the second coil 12, one of the second coil wires 12L being connected to a surface of the head board 13 on the +Z direction side, as shown in Fig. Figure 9 shows the second coil wire, and the other of the second coil wires 12L is connected to a surface of the head board 13 on the side of the -Z direction. In the present embodiment, the two second coil wires 12L are connected to different surfaces of the head board 13, but can be connected to the same surface.

[0082] Since the first coil 11 and the second coil 12 have different positional relationships, a detection current generated in the first coil 11 and a detection current generated in the second coil 12 are affected differently by surrounding metal bodies such as the detection object D and the external element E. That is, the first coil 11 and the second coil 12 have different properties. Accordingly, the proximity sensor 100 incorporates the first coil 11 and the second coil 12 as a detection coil 1, thereby improving the detection accuracy.

[0083] In the configuration where the proximity sensor 100 comprises the first coil 11 and the second coil 12 as the detection coil 1, there is a risk that the detection accuracy will be affected by a relative positional relationship between the first coil 11 and the second coil 12. Since the first coil 11 and the second coil 12 are frequently positioned on an inner surface of the section of the head housing 3 on the +Y-direction side, the detection accuracy places high demands on the processing accuracy of the section of the head housing 3 on the +Y-direction side.As explained above, in a case where the head cylinder section 32 and a metal cap 35 (a metal cap section 35) containing the detection surface 30 consist of different elements, the difficulty of high-precision machining of the head housing section on the +Y-direction side is reduced. This is particularly effective in the setup where the proximity sensor 100 comprises the first coil 11 and the second coil 12. Since the second coil 12 is positioned outside the first coil 11, it is also located near an inner circumferential surface of the head housing 3, i.e., an inner surface of the head cylinder section 32. Accordingly, the section of the head housing 3 on the +Y-direction side must exhibit high machining accuracy not only near the centerline of the head cylinder section 32 but also along a circumferential section through the centerline.As explained above, in a case where the head cylinder section 32 and the metal cap 35 containing the detection surface 30 are made of different elements, the difficulty of high-precision machining of the section of the head housing on the +Y direction side is reduced, which is why the design in which the proximity sensor 100 includes the first coil 11 and the second coil 12, which is arranged outside the first coil 11, is particularly effective.

[0084] The proximity sensor 100 comprises the transmitter circuit 5, the receiver circuit 6, and the control circuit 7. The transmitter circuit 5 supplies the first coil 11 with the pulsed excitation current. The receiver circuit 6 detects the detection current generated in the first coil 11 and the second coil 12. Based on a received signal from the receiver circuit 6, which has detected the detection current, the control circuit 7 detects the presence or absence, or the position, of the detection object D. Since the detection current changes according to a change in the magnetic field, the change in the magnetic field is reflected in the received signal of the receiver circuit 6. The control circuit 7 outputs a result indicating the presence or absence, or the position, of the detection object D.

[0085] The detection coil 1 comprises the first coil 11 and the second coil 12, which differs from the first coil 11. Since the first coil 11 and the second coil 12 are separated, their arrangements within the head housing 3 are different. Therefore, the change in the detection current due to the change in the magnetic field differs between the detection current of the first coil 11 and the detection current of the second coil 12. The receiving circuit 6 transmits the detection current generated in the first coil 11 (hereinafter referred to as the first detection current) and the detection current generated in the second coil 12 (hereinafter referred to as the second detection current) independently to the control circuit. The control circuit 7 detects the presence or absence and the position of the detection object D based on a first received signal derived from the first detection current and a second received signal derived from the second detection current.At this point, the first and second received signals exhibit different signal changes with respect to a change in a specific magnetic field. For example, even in a case where the magnetic field is changed by both the detection object D of the metal body and the external element E of the metal body, several coils with different arrangements are used as detection coil 1, so that the magnetic field change due to the detection object D of the metal body is easily reflected in the first received signal and the magnetic field change due to the external element E of the metal body is easily reflected in the second received signal, and thus different types of information around the head housing 3 can be detected.Accordingly, during detection in the proximity sensor 100, the control circuit 7 processes the first received signal based on the detection current generated in the first coil 11 and the second received signal based on the detection current generated in the second coil 12, taking into account the characteristics of the first coil 11 and the second coil 12, thereby improving the detection accuracy.

[0086] The receiving circuit 6 comprises a first receiving circuit 61, which detects the detection current generated in the first coil 11, and a second receiving circuit 62, which detects the detection current generated in the second coil 12. According to this configuration, the first detection current and the second detection current can be transmitted simultaneously to the control circuit 7 while remaining independent of each other. Since the period during which the control circuit 7 receives the first received signal and the period during which the control circuit 7 receives the second received signal can be the same, the time required to detect the presence or absence and position of the detection object D using the first and second received signals is reduced.Furthermore, the calculation required to correct for the difference between the time period in which the first received signal is detected and the time period in which the second received signal is detected is eliminated. Accordingly, the receiving circuit 6 comprises the first receiving circuit 61 and the second receiving circuit 62, thereby improving the detection accuracy of the proximity sensor 100.

[0087] Here, the suppression of the influence of the metal body, which is not the detection object D, is demonstrated using the Fig. Sections 10A to 11B describe this in detail. In the following, a temporal change in the first received signal can be referred to as the first received waveform, and a temporal change in the second received signal as the second received waveform. Furthermore, the first and second received waveforms together can be referred to as the received waveform.

[0088] The Fig. Figures 10A to 11B show the first received waveform (code ΔR1) with zero matching and the second received waveform (code ΔR2) with zero matching. In this embodiment, zero matching means that the signal intensity is zeroed when no external element E of the metal body is present and the detection object D of the metal body is not within a detection range. Note that in the Fig. In 10A and up to 11B, the horizontal axis represents time and the vertical axis represents the signal intensity of the received waveform.

[0089] Fig. Figure 10A is a diagram representing the received waveform after zeroing, specifically when no external element E of the metal body is present and the detection object D is not within the detection range. As explained above, the waveform adjusted to zero out a value displayed by the waveform when no external element E of the metal body is present and the detection object D is not within the detection range is a zero-adjusted waveform such that both the first received waveform and the second received waveform in the diagram display a value of zero.

[0090] Fig. Figure 10B is a diagram representing the received waveform after zero matching in a case where no external element E is present and the detection object D is within the detection range. As shown in Fig. As shown in Figure 10B, the change in signal intensity of the first received waveform is greater than the change in signal intensity of the second received waveform. This is because the first coil 11 and the second coil 12 are arranged such that the first detection current generated in the first coil 11 is more easily influenced by the change in the magnetic field caused by the detection object D within the detection range than the second detection current generated in the second coil 12.

[0091] Fig. Figure 11A is a diagram representing an image of the received waveform after zero matching when the external element E is present and the detection object D is not within the detection range. As shown in Fig. As shown in Figure 11A, both the change in signal intensity of the first received waveform and the change in signal intensity of the second received waveform are large. This is because both the first detection current generated in the first coil 11 and the second detection current generated in the second coil 12 are slightly affected by the magnetic field change caused by the external element E to which the head 100H is attached. However, while the magnitude of the change in signal intensity of the first received waveform, which is shown in Figure 11A, is relatively small, the change in signal intensity of the second received waveform is relatively small. Fig. 10B is shown, similar to the amount of change in the signal intensity of the first received waveform, which is shown in Fig. As shown in 11A, the amount of change in the signal intensity of the second received signal, which is in Fig. 11A is shown, obviously greater than the amount of change in the signal intensity of the second received signal, which is shown in Fig. 10B is shown. Furthermore, in Fig. 11A the change in signal intensity of the second received signal is greater than the change in signal intensity of the first received signal. This is because the first coil 11 and the second coil 12 are arranged such that the second detection current generated in the second coil 12 is more easily influenced by the external element E than the first detection current generated in the first coil 11.

[0092] Fig. Figure 11B is a diagram representing an image of the received waveform after zero matching, when the external element E is present and the detection object D is within the detection range. Similar to in Fig. 11A, both the change in signal intensity of the first received waveform and the change in signal intensity of the second received waveform are large, as shown in Fig. 11B is shown because the head 100H is attached to the external element E. In contrast to Fig. However, in 11A, the change in signal intensity of the first received signal is greater than the change in signal intensity of the second received signal. In the Fig. In sections 10A to 11B, the change in signal intensity of the first received signal increases when the magnetic field changes due to at least one of the elements, namely the external element E and the detection object D. Therefore, it is difficult to determine the presence or absence and position of the detection object D based solely on the first received signal. In particular, if the distance between the detection object D and the first coil 11 is large, the detection accuracy decreases slightly because the magnitude of the change in signal intensity of the first signal due to the magnetic field change caused by the detection object D is similar to the magnitude of the change in signal intensity of the second signal due to the magnetic field change caused by the external element E. On the other hand, in the Fig. 10A to 11B: When the magnetic field changes due to the external element E, the change in signal intensity of the second received signal is significantly affected. Thus, the first and second received signals are combined, which improves the accuracy of detecting the presence or absence and position of the detection object D.

[0093] More precisely, the calculation is performed using a difference between the first received waveform subjected to zero matching and the second received waveform subjected to zero matching. This difference is a value obtained by subtracting the second received waveform subjected to zero matching from the first received waveform subjected to zero matching. According to this procedure, the calculation result is in the Fig. 10A and Fig. 11A, which shows the received signal in the absence of the detection object D, a negative value, and the calculation result is in the Fig. 10B and Fig. Figure 11B, which shows the received signal in the presence of the detection object D, has a positive value. As explained above, the detection accuracy of the proximity sensor 100 can be improved.

[0094] The following is another example for detection area 30 based on... Fig. 12 described. Fig. Figure 12 is a partially cropped or cut-out perspective view of the cylindrical proximity sensor 100. Fig. 12 are, as in Fig. 8. To prioritize visibility, the representation and reference numbers of the filler material are omitted, but the filler material is filled into an area specified as space within the head housing 3. Fig. Figure 12 shows the arrows X, Y, and Z, which indicate three mutually orthogonal directions. The directions indicated by the arrows X, Y, and Z all correspond to the arrangement positions of the proximity sensor 100, where the direction indicated by arrow X is called the X-axis direction, the direction indicated by arrow Y is called the Y-axis direction, and the direction indicated by arrow Z is called the Z-axis direction. One of the directions along the X-axis is called the +X direction, the other the -X direction. One of the directions along the Y-axis is called the +Y direction, the other the -Y direction. One of the directions along the Z-axis is called the +Z direction, the other the -Z direction. The normal direction of the detection surface 30 is the Y-axis, and the direction in which the detection surface 30 points is the +Y direction.

[0095] The in Fig. The detection surface 30 shown in Figure 12 is made of resin or plastic. If the detection surface 30 in the proximity sensor 100, which uses the induced current, is made of metal, there is a risk that the detection accuracy will decrease for the following reasons: An eddy current is generated at the detection surface 30 itself due to the magnetic field, which produces noise; and a change in the detection current is generated due to the change in the magnetic field caused by the detection surface 30 itself. Therefore, if the detection surface 30 is made of plastic, the detection accuracy simply decreases or increases. On the other hand, a plastic part has lower strength than a metal part. Therefore, the head housing 3 is filled with filler, which improves the mechanical strength. This allows both the detection accuracy and the strength to be achieved.Note that the head 100H can be easily capacitively coupled between the element containing the detection surface 30 and the detection coil 1. Therefore, the resin element is used as the detection surface 30, which easily prevents interference current from flowing near the detection coil 1.

[0096] However, if the head housing 3 is filled with the filler as explained above, there is a risk that the filler will be capacitively coupled and the detection accuracy of the proximity sensor 100 will decrease. More precisely, if the filler is capacitively coupled, the circuit is formed by the ground connected to the power supply cable 2, the head housing 3, and the head housing 3, and thus there is a risk that the interference current will flow from the power supply cable 2 into the head 100H. Therefore, from the point of view of the detection accuracy of the proximity sensor 100 and the strength of the head 100H, it is particularly effective that the head housing 3 with the plastic detection surface 30 is filled with the filler containing the additive with the relatively low relative dielectric constant.Furthermore, the front chamber 51, located on the +Y-direction side of the head housing 3 and containing the detection coil 1 in the Y-axis direction, is filled with the first filler, which contains the additive with the low relative dielectric constant, and the rear chamber 53, which does not contain the detection coil 1 in the Y-axis direction, is filled with the second filler, which has a higher relative dielectric constant and higher hardness than the first filler. According to this design, it is easy to achieve both the prevention of a reduction in detection accuracy due to the influence of noise acting on the head housing 3 on the detection current and the mechanical strength of the head 100H.

[0097] The following section describes the flat proximity sensor 100 with reference to Fig. 13 described. Fig. Figure 13 is an enlarged perspective view of a longitudinal section of the flat proximity sensor 100.

[0098] In the Fig. The flat proximity sensor 100 shown in Figure 13 is a flat, box-shaped head housing 3B filled with a filler material. The filler material is in Fig. 13, designated with reference number 38.

[0099] The box-shaped head housing 3B is not restricted to a strict box shape and can have an essentially box-shaped form. The box-shaped head housing 3B has a first surface 101 and a second surface 102, which differs from the first surface 101. The first surface 101 comprises the detection surface 30, which is the surface that detects the detection object D. The second surface 102 is attached (fixed) such that it comes into contact with a surface of the external element E.

[0100] The proximity sensor 100 further comprises the head board 13. The head board 13 is housed in the box-shaped head housing 3B and extends along the first surface 101. The head board 13 electrically connects the detection coil 1 and the power supply cable 2.

[0101] If the interference current affects the detection current generated in the detection coil 1, there is a risk that the influence of the interference current from the power supply cable 2 into the head 100H, as described by the capacitive coupling of the contents, will lead to a reduction in the detection accuracy of the proximity sensor 100. Therefore, an area where the capacitive coupling of the contents occurs and the interference current circuit can be formed is located away from the detection coil 1. However, in the head housing 3B, a circuit (corresponding to the head board 13) is arranged near the detection coil 1, in which the power supply cable 2 and the detection coil 1 are electrically connected. Thus, with the flat proximity sensor 100, when the interference current flows from the power supply cable 2 into the head 100H, there is a high probability that the interference current will affect the detection current, compared to other types of proximity sensors 100.Therefore, the design in which the relative dielectric constant of the filler is reduced so that the interference current from the power supply cable 2 hardly flows into the head 100H is particularly effective.

[0102] The embodiment described above is, incidentally, purely illustrative and not limiting. The scope of the invention is not defined by the above description but by the claims, and it is intended that meanings corresponding to the claims and all modifications within the scope are included. Among the assemblies described in the embodiments, any assemblies other than those described as an aspect of the invention in "Means of Solving Problems" are arbitrary and may be deleted and modified accordingly.

[0103] The invention provides the flat proximity sensor and is industrially applicable. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2018 - 152 320 A [0002, 0003, 0004]

Claims

[1] Proximity sensor for detecting a detection object, with: a detection coil that generates a magnetic field for detection; a head housing that accommodates the detection coil and has a metal detection surface; and a power supply cable connected to the head housing to power the detection coil, wherein the head housing has a connecting section that guides the power supply cable in a direction that intersects a normal direction of the detection surface on a side opposite the detection surface in the normal direction, and the detection coil is arranged in a position that is spaced apart in the normal direction from the connecting section. [2] Proximity sensor according to claim 1, wherein the head housing has a surface in a circumferential direction with the normal direction as the center line and comprises a cylindrical metal head section in which a circumferential threaded groove is formed in the surface. [3] Proximity sensor according to claim 1, wherein The head housing includes the following: a cylindrical metal head section having a circumferential surface with the normal direction as its center line and an opening provided in the normal direction, and a metal cap section that includes the detection surface and is attached to the cylindrical metal head section to cover the opening of the cylindrical metal head section, and the cylindrical metal head section has a stop section which rests against the metal cap section in a state in which the metal cap section is attached to an inner circumferential surface of the cylindrical metal head section. [4] Proximity sensor according to claim 1, further comprising: a head board to which a coil wire of the detection coil and a core wire of the power supply cable are connected, wherein the head board electrically connects the coil wire and the core wire. [5] Proximity sensor according to claim 1 or 2, further comprising: a transmitting circuit that supplies a pulsed excitation current to the detection coil; a receiving circuit that detects a detection current generated in the detection coil; a control circuit that outputs a detection result of the detection object based on a received signal from the receiving circuit; an amplifier board on which the control circuit is implemented; and an amplifier housing that accommodates the amplifier board and is different from the head housing, the power supply cable is connected to the amplifier housing. [6] Proximity sensor according to claim 5, wherein the power supply cable is connected to the amplifier board and comprises a core wire through which the detection current flows and a shielding shell that surrounds the core wire with a shield. [7] Proximity sensor according to claim 3, the metal cap section comprises the following: a section of soil that includes the detection area, and a circumferential section that stands up from an outer circumferential edge of the bottom section, and in the normal direction, one end of the circumferential section on the side of the connecting section is positioned in a state in which the metal cap section is attached to the cylindrical metal head part, on the side of the sensing surface relative to one end of the detection coil on the side of the connecting section. [8] Proximity sensor according to claim 3, wherein the cylindrical metal head section comprises a section that is closer to the detection surface than an end of the detection coil on the side of the connecting section in the normal direction, and comprises a thin section that is thinner than other sections. [9] Proximity sensor according to claim 3, wherein the detection coil generates a magnetic field with an effective frequency of 200 kHz or less; and a section encompassing the detection area has a thickness of 1.0 mm or less. [10] Proximity sensor according to claim 3, wherein the detection coil comprises: a first coil around which a first coil wire is wound, and a second coil in which a second coil wire, different from the first coil wire, is wound outside the first coil.

Images