Patent Description:
In the related art, various sensors such as proximity sensors and photoelectric sensors have been used to detect presence/absence of objects in detection areas. For example, a proximity sensor includes a coil that generates a magnetic field and detects presence/absence of an object by measuring a change in impedance of the coil due to a dielectric current generated in the object that has approached the coil. Also, a photoelectric sensor detects presence/absence of an object by emitting light from a light projecting unit to a detection area and analyzing light transmitted through or reflected by the object using a light receiving unit. These sensors may be manufactured by housing electronic components such as a coil inside a housing provided with an opening and inserting a part of a clamp that protects the electronic components into the opening.

Also, a sealing resin may be provided inside the housing to seal a gap between the housing and the clamp. At this time, there is a concern that the sealing resin with which the gap is filled may leak out of the gap between an inner wall of the housing and an outer wall of the clamp to the outside of the sensor. Thus, the leakage of the sealing resin is prevented by forming a rib that abuts on the inner wall of the housing on the outer wall of the clamp and pressing the clamp into the housing. Patent Literature <NUM> describes a clamp provided with a belt-shaped projection (corresponding to the rib) on the outer wall.

Patent literature <CIT> proposes a device having an electrical circuit positioned in a housing, and a molding material is arranged in an inner space of the housing. A covering device is arranged between the electrical circuit or a part of the electrical circuit and the molding material. The covering device is manufactured from a continuous finished material and is compressible, and forces are charged through the finished material and are effected in a direction of the electrical circuit.

However, there is a concern that in the aforementioned method, the sealing resin which has exuded from between the housing and the rib may leak to the outside of the sensor for some reasons such as a reason that the height of the rib is slightly smaller than a defined dimension.

Thus, an objective of the present invention is to provide a sensor capable of preventing leakage of a sealing resin from between a housing and a clamp.

A sensor according to an aspect of the present invention includes: a cylindrical-shaped housing which has an opening formed at one end; an electronic component which is housed in the housing; a cylindrical-shaped clamp of which one end is inserted into the housing from the opening; and a sealing resin which seals a gap between an inner wall of the housing and an outer wall of the clamp, on the outer wall, the clamp having a rib which rises towards the inner wall of the housing, the rib including an apex and a sloped surface which extends from the apex towards another end of the clamp and which intersects the outer wall of the clamp, and the sealing resin, which exudes from between the inner wall of the housing and the apex and which is positioned on the sloped surface, having a recess resulting from surface tension. A viscosity of a sealing resin in a liquid form that solidifies and forms the sealing resin may be equal to or greater than <NUM> mPa s, and the sloped surface may intersect the outer wall of the clamp at an angle of equal to or greater than <NUM>°.

According to the aspect, a flow of the sealing resin stops between the inner wall of the housing and the sloped surface of the rib due to the surface tension even in a case in which the sealing resin exudes from between the inner wall of the housing and the rib. In other words, it is possible to prevent the sealing resin from leaking from between the housing and the clamp to the outside of the sensor. In addition, it is possible to prevent leakage of the sealing resin with higher precision as compared with a case in which the viscosity of the liquid resin is equal to or less than <NUM> mPa·s or the sloped surface intersects the outer wall of the clamp at an angle of equal to or less than <NUM>°.

In the aspect, the rib may be continuously formed along an outer circumferential direction of the clamp.

According to the aspect, it is possible to prevent leakage of the sealing resin over the entire periphery of the outer wall of the clamp.

In the aspect, a plurality of the ribs may be formed in an aligned manner in an axial direction of the clamp.

According to the aspect, it is possible to prevent leakage of the sealing resin with higher precision as compared with a case in which only one rib is formed.

In the aspect, the sensor may be a proximity sensor.

According to the aspect, it is possible to detect presence/absence of a detection target in a non-contact manner.

A manufacturing method of a sensor according to another aspect of the present embodiment includes: inserting an electronic component into a cylindrical-shaped housing having an opening formed at one end; inserting one end of a cylindrical-shaped clamp into the housing from the opening; and sealing a gap between an inner wall of the housing and an outer wall of the clamp with a sealing resin, on the outer wall, the clamp having a rib which rises towards the inner wall of the housing, the rib including an apex and a sloped surface which extends from the apex towards another end of the clamp and which intersects the outer wall of the clamp, and the sealing resin, which exudes from between the inner wall of the housing and the apex and which is positioned on the sloped surface, having a recess resulting from surface tension. A viscosity of a sealing resin in a liquid form that solidifies and forms the sealing resin may be equal to or greater than <NUM> mPa s, and the sloped surface may intersect the outer wall of the clamp at an angle of equal to or greater than <NUM>°.

According to the present invention, it is possible to provide a sensor capable of preventing leakage of a sealing resin from between a housing and a clamp.

An embodiment of the present invention will be described with reference to the accompanying drawings. Note that components with the same reference signs applied thereto in each drawing have the same or similar configurations.

Referring to <FIG> and <FIG>, an inner structure of a sensor <NUM> will be described. <FIG> is an exploded perspective view of the sensor <NUM> according to an embodiment of the present invention. <FIG> is a sectional view along the II-II in a state in which the sensor <NUM> illustrated in <FIG> has been assembled. Although a case in which the present invention is applied to a proximity sensor will be described as an example in the present specification, the present invention is not limited to the proximity sensor and can be applied to various sensors such as a photoelectric sensor.

The sensor <NUM> according to the present embodiment includes a housing <NUM>, a clamp <NUM>, a substrate <NUM>, cable wires <NUM>, a cable <NUM>, a ring component <NUM>, a detection unit <NUM>, and a shield <NUM>. The housing <NUM> is formed into a cylindrical shape, and electronic components such as a substrate <NUM> are housed therein. The housing <NUM> has an opening <NUM> at one end, and the electronic components such as a substrate <NUM> are inserted into the opening <NUM>. The housing <NUM> is formed from metal, a resin, or the like. The sensor <NUM> has a columnar shape or may be a prism shape in which outer peripheries of the housing <NUM> and the clamp <NUM> are polygonal shapes.

An end of the clamp <NUM> is connected to the opening <NUM> of the housing <NUM> to protect the electronic components such as a substrate <NUM> housed in the housing <NUM>. As represented by the arrow in <FIG>, if the direction directed from the clamp <NUM> to the housing <NUM> along the axial direction of the sensor <NUM> is defined to be a front side, and the direction directed from the housing <NUM> to the clamp <NUM> is defined to be a rear side, a front portion <NUM> of the clamp <NUM> is inserted into the housing <NUM> from the opening <NUM> as illustrated in <FIG>. Although a large area of the substrate <NUM> is housed in the housing <NUM>, a rear area of the substrate <NUM> is housed in the clamp <NUM>. Also, a part of the cable wires <NUM>, the ring component <NUM>, and the cable <NUM> is housed in the clamp <NUM>.

Although the clamp <NUM> can be formed from a resin, metal, or the like, the clamp <NUM> is preferably formed from a transparent material through which visible light is transmitted such that a display lamp <NUM> located inside the sensor <NUM> is visible from the outside.

As illustrated in <FIG>, the outer wall of the front portion <NUM> of the clamp <NUM> is provided with ribs <NUM> rising toward the inner wall of the housing <NUM>. The ribs <NUM> prevent a sealing resin from leaking from between the housing <NUM> and the clamp <NUM> to the outside of the sensor <NUM> when the sealing resin is provided inside the sensor <NUM>. In the present embodiment, the ribs <NUM> are continuously formed along an outer circumferential direction of the clamp <NUM>. Also, two ribs <NUM> are formed in an aligned manner in the axial direction of the clamp <NUM>. Note that the number of ribs <NUM> is not limited thereto and may be one or three or more. Details of the ribs <NUM> will be described later using <FIG>.

The substrate <NUM> is a substrate on which a control circuit (not illustrated) for controlling the detection unit <NUM> and a current supply circuit (not illustrated) for supplying a current to the detection unit <NUM> are mounted, and a part thereof is housed in the housing <NUM>. The detection unit <NUM> is attached to the end of the substrate <NUM> on the front side as illustrated in <FIG>. The detection unit <NUM> detects presence/absence of a detection target in a non-contact manner. The detection unit <NUM> includes a core <NUM> in which a coil <NUM> is housed and the coil <NUM> wound therearound in an annular shape. On the other hand, a land <NUM> is provided at an end of the substrate <NUM> on the rear side and is electrically connected to the cable wires <NUM>. Here, a method of detecting a detection target performed by the sensor <NUM> will be described. First, an excitation current is supplied from the current supply circuit mounted on the substrate <NUM> to the coil <NUM>. The coil <NUM> generates a magnetic field on the basis of the supplied excitation current. If a detection target such as a metal target approaches the coil <NUM> in this state, an eddy current is generated inside the detection target due to the rule of electromagnetic induction. Since the eddy current generates a magnetic field, a magnetic flux penetrating through the coil <NUM> and thus an impedance of the coil <NUM> changes. The control circuit connected to the detection unit <NUM> measures the change in impedance of the coil <NUM> and detects presence/absence of the detection target.

The display lamp <NUM> that displays an operation state of the sensor <NUM> is mounted on the substrate <NUM>. The display lamp <NUM> may be, for example, an LED. In the present embodiment, the display lamp <NUM> is turned on in a case in which the power of the sensor <NUM> is turned on or the sensor <NUM> detects a detection target.

The cable <NUM> is obtained by applying a protective coating to a plurality of cable wires <NUM>. The cable wires <NUM> are electrically connected to the land <NUM> of the substrate <NUM>, The cable wires <NUM> may supply power from an external power source to the circuits mounted on the substrate <NUM>. Also, the cable wire <NUM> may transmit output signals from the control circuit mounted on the substrate <NUM> to external equipment such as an amplifier.

The ring component <NUM> is provided at an outer periphery of the cable <NUM> to prevent breakage of the cable <NUM>. Specifically, the ring component <NUM> is formed through injection molding or the like at a position of the cable <NUM> where an end of the protective coating is covered. Also, the ring component <NUM> comes into close contact with the sealing resin provided inside the housing <NUM> to secure the cable <NUM> to the clamp <NUM>.

A sealing ring <NUM> is provided in a region between the cable <NUM> and the clamp <NUM> behind the ring component <NUM> so as to surround the cable <NUM>. The sealing ring <NUM> seals a gap between the inner wall of the clamp <NUM> and the outer periphery of the cable <NUM>. The sealing ring <NUM> prevents liquid and dust from entering inside from the outside of the sensor <NUM>. Also, the sealing ring <NUM> prevents the sealing resin provided inside the sensor <NUM> from leaking to the outside.

The shield <NUM> removes noise from the outside. The shield <NUM> is provided to surround a part of the detection unit <NUM> and the substrate <NUM> and prevents noise from reaching the detection unit <NUM> and the substrate <NUM>. The shield <NUM> may be formed from a metal film, for example, or may be formed from a laminated member of a copper foil and a polyimide resin.

<FIG> is a diagram illustrating a state in which the sealing resin (a first resin <NUM> and a second resin <NUM>) are provided inside the sensor <NUM> illustrated in <FIG>. Also, <FIG> is a diagram illustrating a process of providing the sealing resin inside the sensor <NUM>.

The first resin <NUM> out of the sealing resin is provided in a front area inside the housing <NUM> as illustrated in <FIG> and covers a part of the detection unit <NUM> and the substrate <NUM>. The first resin <NUM> secures the substrate <NUM> to the housing <NUM> and prevents positional deviation of the substrate <NUM>. The second resin <NUM> is provided in a rear area inside the housing <NUM> and inside the clamp <NUM>. The second resin <NUM> seals a gap between the housing <NUM> and the clamp <NUM> represented as a dashed-line area A. Also, a clearance where no resin is present is provided between the first resin <NUM> and the second resin <NUM>.

Referring to <FIG>, the process of providing the first resin <NUM> and the second resin <NUM> inside the housing <NUM> will be described. First, as illustrated in (a) of <FIG>, the housing <NUM> is disposed such that the front surface <NUM> is located on the lower side, and the first resin <NUM> in a liquid form is poured from the opening <NUM> into the housing <NUM>. Thereafter, the substrate <NUM> with the detection unit <NUM> and the shield <NUM> attached thereto is inserted into the housing <NUM>. In this state, the first resin <NUM> is solidified, and the substrate <NUM> is secured to the housing <NUM>.

Next, the cable wires <NUM> are connected to the land of the substrate <NUM> as illustrated in (b) of <FIG>. The connection between the cable wires <NUM> and the land may be performed through soldering. Thereafter, the second resin <NUM> is poured from the opening <NUM> into the housing <NUM> as illustrated in (c) of <FIG>.

Next, the clamp <NUM> is inserted into the opening <NUM> of the housing <NUM> as illustrated in (d) of <FIG>. Before the second resin <NUM> is solidified, the entire sensor <NUM> is vertically inverted as illustrated in (e) of <FIG>. Then, the second resin <NUM> moves to the side of the clamp <NUM> due to an influence of gravity, and a clearance is provided between the first resin <NUM> and the second resin <NUM>. In this state, the second resin <NUM> is solidified. The sealing resin is provided inside the housing <NUM> by the aforementioned method. Note that the method is not limited to the aforementioned method, and the sealing resin may be provided inside the sensor <NUM> by a method of providing minute pores in the housing <NUM> or the clamp <NUM> and filling the inside of the sensor <NUM> with the sealing resin from the pores or the like.

As described above, the second resin <NUM> in the liquid form is poured into the sensor <NUM>. Therefore, the second resin <NUM> that has been poured into the housing <NUM> may enter the gap between the housing <NUM> and the clamp <NUM>. As illustrated in <FIG>, the outer wall of the clamp <NUM> is provided with the ribs <NUM>. The ribs <NUM> prevent the second resin <NUM> from flowing and prevents the second resin <NUM> from leaking from the gap between the inner wall of the housing <NUM> and the outer wall of the clamp <NUM> to the outside of the sensor <NUM>. Here, the ribs <NUM> will be described using <FIG> and <FIG>.

<FIG> is an enlarged view of the dashed-line area A illustrated in <FIG> and is a diagram illustrating an example of the shape of the ribs <NUM>. <FIG> is a diagram illustrating another example of the shape of the ribs <NUM>.

As illustrated in <FIG>, the ribs <NUM> rising toward the inner wall 10a of the housing <NUM> are formed on the outer wall 20a of the clamp <NUM>. Each rib <NUM> has an apex <NUM> and two sloped surfaces 26a and 26b. The apex <NUM> is a connecting surface that connects the sloped surface 26a and the sloped surface 26b. The sloped surface 26a is a sloped surface inclined downward from the apex <NUM> to the front side of the sensor <NUM> while the sloped surface 26b is a sloped surface inclined downward from the apex <NUM> to the rear side of the sensor <NUM>. Note that although two ribs <NUM> are formed, both the ribs <NUM> have a similar configuration, and the rib <NUM> located on the front side of the sensor <NUM> will thus be described as an example in the present embodiment.

As illustrated in <FIG>, the sloped surface 26b intersects the outer wall 20a of the clamp <NUM> at an angle α. The size of the angle α is adjusted such that a flow of the second resin <NUM> which has exuded from between the inner wall 10a of the housing <NUM> and the apex <NUM> stops between the inner wall 10a of the housing <NUM> and the sloped surface 26b due to surface tension. The size of the angle α is defined on the basis of the viscosity of the second resin <NUM> in the liquid form. A relationship between the size of the angle α and the viscosity of the second resin <NUM> will be described using <FIG>.

The second resin <NUM> in the liquid form that has poured into the sensor <NUM> enters the gap between the inner wall 10a of the housing <NUM> and the outer wall 20a of the clamp <NUM> and moves in the arrow direction represented in <FIG> in the gap. Specifically, the second resin <NUM> moves from the sloped surface 26a toward the apex <NUM>. As described above, the flow of the second resin <NUM> stops between the inner wall 10a of the housing <NUM> and the sloped surface 26b due to surface tension even in a case in which the second resin <NUM> has exuded from between the inner wall 10a of the housing <NUM> and the apex <NUM>. The shape of the second resin <NUM> that has exuded does not project toward the advancing direction of the second resin <NUM> and has a recess 51a toward the inside of the second resin due to an influence of the surface tension.

The shape of the rib <NUM> is not limited to the shape illustrated in <FIG>. For example, a surface of the rib <NUM> located on the front side (the side on which the second resin <NUM> enters inside) of the sensor <NUM> may not be the sloped surface 26a and may be a side surface <NUM> that substantially perpendicularly intersects the outer wall 20a of the clamp <NUM> as illustrated in <FIG>. Also, although two ribs <NUM> are provided in the axial direction of the clamp <NUM> in the present embodiment, the number of ribs <NUM> is not limited and may be one or three or more.

<FIG> is a table illustrating a relationship between the viscosity of the second resin <NUM> and the angle α formed between the sloped surface 26b and the outer wall 20a of the clamp <NUM>. The table in <FIG> illustrates a result of verifying whether or not a flow of the second resin <NUM> that has exuded stops at the gap between the inner wall 10a of the housing <NUM> and the sloped surface 26b with each of the viscosity of the second resin <NUM> and the angle α changed. The table illustrated in <FIG> shows the result of verification performed by changing the viscosity of the second resin <NUM> to "<NUM> mPa·s", "<NUM> mPa·s", and "<NUM> mPa·s" and changing the angle of the angle α to "<NUM>°", "<NUM>°", and "<NUM>°".

As illustrated in <FIG>, when the viscosity of the second resin <NUM> is <NUM> mPa·s and the angle α is <NUM>°, the flow of the second resin <NUM> does not stop at the gap between the inner wall 10a of the housing <NUM> and the sloped surface 26b. On the other hand, when the viscosity of the second resin <NUM> is <NUM> mPa·s and the angle α is <NUM>° or <NUM>°, the flow of the second resin <NUM> stops at the gap between the inner wall 10a of the housing <NUM> and the sloped surface 26b.

In a case in which the viscosity of the second resin <NUM> is <NUM> mPa·s or <NUM> mPa·s, the flow of the second resin <NUM> stops at the gap between the inner wall 10a of the housing <NUM> and the sloped surface 26b regardless of which of <NUM>°, <NUM>°, and <NUM>° the angle α is. In other words, it is possible to stop the flow of the resin with a lower viscosity at the gap between the inner wall 10a of the housing <NUM> and the sloped surface 26b as the angle α increases (as the angle formed between the inner wall 10a of the housing <NUM> and the sloped surface 26b is smaller). The size of the angle α and the viscosity of the resin used as the second resin <NUM> may be determined based on the verification result as illustrated in <FIG>.

According to the sensor <NUM> in the present embodiment, the flow of the second resin <NUM> stops between the inner wall 10a of the housing <NUM> and the sloped surface 26b of each rib <NUM> due to surface tension even in a case in which the second resin <NUM> exudes from between the inner wall 10a of the housing <NUM> and the rib <NUM>. In other words, it is possible to prevent the second resin <NUM> from leaking from between the housing <NUM> and the clamp <NUM> to the outside of the sensor <NUM>.

Also, since the ribs <NUM> are continuously formed along the outer circumferential direction of the clamp <NUM>, it is possible to prevent the second resin <NUM> from leaking over the entire periphery of the outer wall of the clamp <NUM>. In addition, the plurality of ribs <NUM> are formed in an aligned manner in the axial direction of the clamp <NUM>. Therefore, it is possible to prevent leakage of the second resin <NUM> with higher precision as compared with a case in which only one rib is formed.

Claim 1:
A sensor (<NUM>) comprising:
a cylindrical-shaped housing (<NUM>) which has an opening (<NUM>) formed at one end;
an electronic component which is housed in the housing (<NUM>);
a cylindrical-shaped clamp (<NUM>) of which one end is inserted into the housing (<NUM>) from the opening (<NUM>); and
a sealing resin (<NUM>) which seals a gap between an inner wall (10a) of the housing (<NUM>) and an outer wall (20a) of the clamp (<NUM>),
wherein on the outer wall (20a), the clamp (<NUM>) has a rib (<NUM>) which rises towards the inner wall (10a) of the housing (<NUM>),
the rib (<NUM>) comprises an apex (<NUM>) and a sloped surface (26b) which extends from the apex (<NUM>) towards another end of the clamp (<NUM>) and which intersects the outer wall (20a) of the clamp (<NUM>), and the sensor (<NUM>) is characterized in that:
the sealing resin (<NUM>), which exudes from between the inner wall (10a) of the housing (<NUM>) and the apex (<NUM>) and which is positioned on the sloped surface (26b), has a recess (51a) resulting from surface tension,
wherein a viscosity of a sealing resin in a liquid form that solidifies and forms the sealing resin (<NUM>) is equal to or greater than <NUM> mPa s, and
the sloped surface (26b) intersects the outer wall (20a) of the clamp (<NUM>) at an angle of equal to or greater than <NUM>°.