Liquid detection sensor

Abstract

To provide a liquid detection sensor that is capable of detecting, with high reliability, intrusion of liquid into the waterproof housing of a detection target device.SOLUTION: A liquid detection sensor 2 for detecting intrusion of water into a rack housing 15 of a steering device 1 includes an electrode 31 inserted into a through hole 150 in the rack housing 15, and detects intrusion of water into the rack housing 15 on the basis of a change in capacitance between the electrode 31 and the rack housing 15.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a liquid detection sensor that detects the intrusion of a liquid into a waterproof housing of a detection target device. [Background technology]

[0002] BACKGROUND ART Conventionally, for example, some steering devices for vehicles are provided with a sensor that detects the intrusion of moisture into the housing (see, for example, Patent Document 1).

[0003] The steering system described in Patent Document 1 includes a cylindrical housing, a steering rod supported while penetrating the housing in the vehicle width direction, a steering motor that moves the steering rod back and forth within the housing, tie rods connected to both ends of the steering rod via ball joints, and a boot that covers the opening of the housing. A sheet-like water droplet sensor with a pair of electrodes is disposed at each of the left and right ends of the housing. If moisture enters the housing due to a tear in the boot or other reason and water droplets adhere to the surface of the water droplet sensor, the electrical resistance between the pair of electrodes of the water droplet sensor decreases, thereby detecting the moisture intrusion. When moisture intrusion is detected, an electronic control unit that controls the steering motor stops operation of the steering motor to prevent the steering motor from failing due to a short circuit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-111032 Summary of the Invention [Problem to be solved by the invention]

[0005] In the device described in Patent Document 1, if foreign matter such as sand or dust that has entered through a torn part of the boot or grease inside the housing adheres to the electrodes of the water droplet sensor, it may not be possible to detect water even if it has entered the housing. Therefore, an object of the present invention is to provide a liquid detection sensor that can detect with high reliability the intrusion of liquid into the housing of the device to be detected. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present invention provides a liquid detection sensor that detects the intrusion of liquid into a waterproof housing of a detection target device, the liquid detection sensor having an electrode inserted into a through hole formed in the housing, and detecting the intrusion of liquid into the housing by a change in the electrostatic capacitance of the electrode. [Effects of the Invention]

[0007] The liquid detection sensor according to the present invention can detect with high reliability the intrusion of liquid into the housing of the device to be detected. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing an example of the general configuration of a steering device of a vehicle to which a liquid detection sensor 2 according to an embodiment of the present invention is attached. [Figure 2] FIG. 2 is a perspective view showing the liquid detection sensor together with a part of the rack housing. [Figure 3] 2 is a perspective view of a liquid detection sensor and a part of a rack housing, seen from a different direction from that shown in FIG. 1. [Figure 4] FIG. 3 is an exploded perspective view of the liquid detection sensor as seen from the same direction as FIG. 2. [Figure 5] FIG. 4 is an exploded perspective view of the liquid detection sensor as seen from the same direction as FIG. 3. [Figure 6] FIG. 2 is a cross-sectional view of the liquid detection sensor and the rack housing. [Figure 7]1(a) is an enlarged perspective cross-sectional view of a part of the liquid detection sensor, and FIG. 1(b) is a perspective view showing an electrode member of the liquid detection sensor. [Figure 8] FIG. 2 is a plan view showing a substrate of the liquid detection sensor. [Figure 9] FIG. 2(a) is a diagram showing the inside of a first member of a cable holder, and FIG. 2(b) is a diagram showing the outside of the first member. [Figure 10] FIG. 2 is a plan view showing a substrate of the liquid detection sensor. [Figure 11] (a) is a cross-sectional view of the periphery of the electrode when no water has entered the rack housing, and (b) is a cross-sectional view of the periphery of the electrode when water has entered the rack housing and accumulated around the periphery of the electrode. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Embodiment Mode] FIG. 1 is a schematic diagram showing an example of the general configuration of a steering device 1 for a vehicle to which a liquid detection sensor 2 according to an embodiment of the present invention is attached.

[0010] The steering device 1 includes a steering wheel 10 that is steered by a driver, a steering shaft 11 connected to the steering wheel 10, a torque sensor 12 that detects the steering torque transmitted from the steering wheel 10 to the steering shaft 11, a steering assist device 13 that assists the steering operation, a cylindrical rack shaft 14 that extends in the left-right direction of the vehicle, a rack housing 15 that accommodates the rack shaft 14, a pair of left and right ball joints 161, 162 connected to both ends of the rack shaft 14, and a pair of ball joints 161, 162. a pair of left and right tie rods 171, 172 each swingably connected to the rack shaft 14 via a pair of bellows-structured boots 181, 182 respectively arranged between both ends of the rack shaft 14 and the pair of left and right tie rods 171, 172; a sealing member 183 covering the opening of the rack housing 15 into which the steering shaft 11 is inserted; and a control device 19 controlling the steering assist device 13 so that a steering assist force corresponding to the steering torque detected by the torque sensor 12 is applied to the steering shaft 11.

[0011] A rack tooth portion 141 is provided on the rack shaft 14, and a pinion gear 111 provided at the tip of the steering shaft 11 meshes with the rack tooth portion 141 inside the rack housing 15. When the steering shaft 11 rotates, the meshing of the rack tooth portion 141 with the pinion gear 111 moves the rack shaft 14 in the left-right direction, and the left and right steered wheels 101, 102 are steered.

[0012] The left and right ends of the rack shaft 14 protrude from the rack housing 15. The boots 181, 182 are made of a flexible material such as rubber or resin, and prevent moisture and the like from entering the inside of the rack housing 15 through the gap between the rack housing 15 and the rack shaft 14. The left and right boots 181, 182 and the sealing member 183 form a waterproof structure for the rack housing 15. In other words, the rack housing 15 is waterproofed to prevent moisture from entering the interior.

[0013] For example, if the boots 181, 182 come into contact with a protrusion on the road or ground while the vehicle is traveling, portions of the boots 181, 182 may be torn or ripped. If the vehicle then travels through a deep puddle in this state, water will seep into the rack housing 15 through the damaged portions of the boots 181, 182. Water that seeps into the rack housing 15 can cause rust and, if it freezes, may interfere with the smooth movement of the rack shaft 14.

[0014] For this reason, in this embodiment, a liquid detection sensor 2 is attached to the rack housing 15. When the liquid detection sensor 2 detects the intrusion of water, a signal indicating that water has infiltrated into the rack housing 15 is sent to, for example, the control device 19, which then alerts the driver by turning on a warning light on the instrument panel, for example. The liquid detection sensor 2 is attached to, for example, the lower end of the rack housing 15 in the vertical direction. The steering device 1 is a detection target device that the liquid detection sensor 2 detects the intrusion of water into the rack housing 15. Next, the configuration of the liquid detection sensor 2 will be described.

[0015] FIG. 2 is a perspective view showing the liquid detection sensor 2 together with a part of the rack housing 15. FIG. 3 is a perspective view showing the liquid detection sensor 2 and a part of the rack housing 15, viewed from a different direction than FIG. 1. FIG. 4 is an exploded perspective view of the liquid detection sensor 2, viewed from the same direction as FIG. 2. FIG. 5 is an exploded perspective view of the liquid detection sensor 2, viewed from the same direction as FIG. 3. FIG. 6 is a cross-sectional view of the liquid detection sensor 2 and the rack housing 15. FIG. 7(a) is an enlarged perspective cross-sectional view showing a part of the liquid detection sensor 2. FIG. 7(b) is a perspective view showing the electrode member 3 of the liquid detection sensor 2. FIG. 8 is a plan view showing the substrate 4 of the liquid detection sensor 2.

[0016] The rack housing 15 has a through-hole 150 that penetrates between the inner peripheral surface 15a and the outer peripheral surface 15b of the rack housing 15, an annular wall 151 that protrudes from the outer peripheral surface 15b so as to surround the opening of the through-hole 150 on the outer peripheral surface 15b side, and a screw hole 152 formed in the portion where the liquid detection sensor 2 is attached. The rack housing 15 is made of metal such as an aluminum alloy, and is electrically grounded.

[0017] The liquid detection sensor 2 includes an electrode member 3 having an electrode 31 inserted into a through-hole 150 in the rack housing 15, a substrate 4 to which the electrode member 3 is connected, an electronic component 5 mounted on the substrate 4, a cable 6 having a plurality of electric wires 61 to 63 connected to the electrodes of the substrate 4 and a sheath 64, a cable holder 7 that holds the end of the cable 6, a sensor case 8 that houses the substrate 4 and the electrode member 3 together with the cable holder 7, a collar 91 embedded in the sensor case 8, and an O-ring 92 attached to the sensor case 8. The liquid detection sensor 2 detects the intrusion of liquid into the rack housing 15 by a change in capacitance between the electrode 31 and the rack housing 15 due to liquid such as water that has infiltrated into the rack housing 15.

[0018] The electrode member 3 is made of, for example, copper or a copper alloy, and integrally includes a flat electrode 31 and a connection wire 32 that connects the electrode 31 to the substrate 4. The electrode 31 is bent at a right angle to the longitudinal direction of the connection wire 32. The connection wire 32 is connected to a through-hole land 40, which is a board electrode of the substrate 4, by, for example, soldering. The electrode 31 is disposed within the through-hole 150 without extending further into the rack housing 15 than the inner circumferential surface 15a, which is the inner surface of the rack housing 15. In other words, the length of the connection wire 32 is set shorter than the distance between the substrate 4 and the inner circumferential surface 15a of the rack housing 15. This prevents the liquid detection sensor 2 from interfering with the rack shaft 14.

[0019] The shape of the through hole 150 and the shape of the electrode 31 are both circular when viewed in the axial direction of the through hole 150 (radial direction of the rack housing 15). The central axis C of the through hole 150 coincides with the center of the electrode 31. The electrode 31 is disposed in the through hole 150 while being housed in the sensor case 8.

[0020] In this embodiment, the substrate 4 is a rigid substrate having a plate-shaped base material made of a dielectric material such as FR4 (glass fiber impregnated with epoxy resin and subjected to a thermosetting treatment), but is not limited to this and may be a flexible substrate having a base material made of a flexible film-like dielectric material such as polyimide. A wiring pattern made of copper foil is formed on the surface of the substrate 4, connecting the electronic component 5 to the multiple electric wires 61 to 63 of the cable 6 and the electrode member 3, but the wiring pattern is not shown in the drawings. The electronic component 5 detects the electrostatic capacitance between the electrode 31 and the rack housing 15. The circuit configuration of the electronic component 5 will be described later.

[0021] The electric wires 61 to 63 of the cable 6 are insulated electric wires in which metal core wires 611, 621, and 631 are covered with insulating coatings 612, 622, and 632 made of an insulator. Of the three electric wires 61 to 63, for example, the electric wires 61 and 62 are used to supply power to the electronic component 5, and the electric wire 63 is used to transmit an output signal from the electronic component 5. The core wires 611, 621, and 631 of the electric wires 61 to 63 are connected, for example, by soldering, to through-hole lands 41 to 43 serving as board electrodes provided on the board 4, respectively. The sheath 64 is a urethane sheath made of, for example, urethane, and collectively covers the three electric wires 61 to 63.

[0022] The cable holder 7 is made of a first member 71 and a second member 72 made of resin, and accommodates a portion of the longitudinal direction of each of the electric wires 61 to 63 led out from the sheath 64. The first member 71 and the second member 72 each have a rectangular bottom plate portion 711, 721, a peripheral wall portion 712, 722 formed along the outer edge of the bottom plate portion 711, 721, and a semi-cylindrical sheath holding portion 713, 723 that holds the sheath 64.

[0023] An outer surface 711a (see FIG. 5) of the bottom plate portion 711 of the first member 71 faces the substrate 4 in parallel. The sheath holding portions 713, 723 are formed into a cylindrical shape by combining the first member 71 and the second member 72, and hold the sheath 64. The first member 71 and the second member 72 are combined by a snap-fit ​​structure. More specifically, claw portions 720a at the tips of multiple snap-fit ​​pieces 720 provided on the second member 72 are engaged with the bottom plate portion 711 of the first member 71.

[0024] 9(a) is a structural diagram showing the inside of the first member 71, and Fig. 9(b) is a structural diagram showing the outside of the first member 71. The first member 71 has a pair of positioning protrusions 714 provided so as to protrude from an outer surface 711a of the bottom plate portion 711 toward the board 4 side, an electric wire holding portion 715 provided so as to protrude from an inner surface 711b of the bottom plate portion 711 toward the second member 72 side, and a wall-like protrusion 716 that abuts against the board 4.

[0025] Each positioning protrusion 714 is composed of a large-diameter cylindrical portion 714a and a small-diameter cylindrical portion 714b, which are arranged coaxially. The large-diameter cylindrical portion 714a abuts against the surface of the substrate 4 facing the first member 71, and the distance between the substrate 4 and the bottom plate portion 711 of the first member 71 is determined by the large-diameter cylindrical portion 714a and the protrusion 716. The substrate 4 is formed with an insertion hole 44 through which the small-diameter cylindrical portion 714b is inserted. The small-diameter cylindrical portion 714b inserted into the insertion hole 44 is pressed toward the substrate 4 while being heated, thereby forming a retaining portion 714c for the substrate 4, as shown in FIG. 6 .

[0026] The electric wire holding portion 715 is formed with holding grooves 715a, 715b, and 715c that accommodate the electric wires 61 to 63, respectively, and the electric wires 61 to 63 are prevented from slipping out of the holding grooves 715a, 715b, and 715c by a bottom plate portion 721 of the second member 72. The bottom plate portion 711 and the electric wire holding portion 715 are formed with lead-out holes 710a, 710b, and 710c that lead out the tip ends of the electric wires 61 to 63 toward the board 4. The electric wires 61 to 63 are bent 90 degrees within the cable holder 7 and led out from the lead-out holes 710a, 710b, and 710c, and the tip ends protruding from the cable holder 7 are connected to the through-hole lands 41 to 43 of the board 4.

[0027] Furthermore, a recess 711c that accommodates a part of the electronic component 5 is formed in the bottom plate portion 711 so as to be recessed from the outer surface 711a. That is, the height H (see FIG. 4) of the electronic component 5 is greater than the thickness of the large-diameter cylindrical portion 714a of the positioning protrusion 714, and the electronic component 5 is accommodated in the recess 711c, thereby reducing the size of the liquid detection sensor 2.

[0028] The sensor case 8 is made up of a case body 81 and a case lid 82. The case body 81 and the case lid 82 are made of injection-molded resin. A metal collar 91 and the electrode member 3 are insert-molded into the case body 81. The case body 81 integrally includes an attachment section 811 into which the collar 91 is insert-molded, an accommodation section 812 that accommodates the substrate 4 and the cable holder 7, an electrode holding section 813 that holds the electrodes 31 of the electrode member 3, a seal holding section 814 into which an O-ring 92 serving as a seal member is fitted, and an outlet section 815 from which the cable 6 is led out.

[0029] As shown in Fig. 6, the sensor case 8 is attached to the rack housing 15 by threading bolts 93 inserted through collars 91 into threaded holes 152 in the rack housing 15. An annular groove 812a is formed in the accommodation portion 812 to accommodate the tip end of the annular wall 151 of the rack housing 15. The electrode holding portion 813 is cylindrical and has a bottom portion 813a and a cylindrical portion 813b, and the electrode 31 is embedded in the bottom portion 813a. A portion of the connection line portion 32 is embedded in the cylindrical portion 813b.

[0030] The seal holding portion 814 is provided on the outer periphery of the electrode holding portion 813, and an O-ring 92 is fitted onto the seal holding portion 814. The lead-out portion 815 is welded to the sheath 64 of the cable 6, thereby preventing moisture from entering the housing portion 812 from the lead-out portion 815. The material of the case main body 81 is preferably a resin that easily dissolves in the sheath 64, and urethane is desirable, for example. Alternatively, the material of the case main body 81 can be polyamide (PA) such as nylon resin, or polybutylene phthalate (PBT).

[0031] In this embodiment, the tip of the electrode holder 813 is disposed within the through-hole 150 without protruding further inward into the rack housing 15 than the inner circumferential surface 15a of the rack housing 15. This makes it possible to prevent the electrode holder 813 from interfering with the rack shaft 14. However, the tip of the electrode holder 813 may protrude further inward into the rack housing 15 than the inner circumferential surface 15a of the rack housing 15 as long as it does not interfere with the movement of the rack shaft 14.

[0032] The case lid 82 integrally includes a flat plate portion 821 that abuts against the tip surface 812b of the storage portion 812 of the case body 81, and a surrounding wall portion 822 that surrounds the outer peripheral surface 812c near the tip surface 812b of the storage portion 812. The storage portion 812 of the case body 81 and the surrounding wall portion 822 of the case lid 82 are welded along the entire periphery by, for example, laser welding or ultrasonic welding. Alternatively, the case lid 82 may be glued to the case body 81. The case lid 82 prevents foreign matter, such as moisture, from entering the storage portion 812. When the storage portion 812 of the case body 81 and the surrounding wall portion 822 of the case lid 82 are welded by laser welding or ultrasonic welding, it is desirable that the case lid 82 be made of the same material as the case body 81. However, the case lid 82 may be made of a different material from the case body 81.

[0033] 10 is a circuit diagram showing an example of the configuration of a capacitance measurement circuit in an electronic component 5. This circuit configuration example can also be used in a touch sensor that detects contact with a human finger, and includes a pulse signal generating unit 51, a resistor 52, a capacitor 53, a gate element 54, and a delay time measuring unit 55. The resistor 52 and the capacitor 53 are connected in series between the pulse signal generating unit 51 and the ground potential. The gate element 54 is connected between the delay time measuring unit 55 and a node 56 between the resistor 52 and the capacitor 53. The node 56 is also connected to the connection line 32 of the electrode member 3.

[0034] FIG. 11(a) is a cross-sectional view of the periphery of the electrode 31 when no water has entered the rack housing 15. FIG. 11(b) is a cross-sectional view of the periphery of the electrode 31 when water W has entered the rack housing 15 and accumulated around the periphery of the electrode 31. A capacitance is generated between the electrode 31 and the rack housing 15, and the magnitude of this capacitance changes depending on whether or not water W has entered. This is because the relative dielectric constant of air is approximately 1.0, while the relative dielectric constant of water is approximately 80.0. In FIGS. 11(a) and 11(b), the strength of the capacitive coupling between the electrode 31 and the rack housing 15 is schematically represented by the difference in thickness of the double-headed arrows.

[0035] A pulse signal generating unit 51 of the electronic component 5 outputs a pulse signal at a predetermined period, and this pulse signal is transmitted to a node 56 via a resistor 52. The electrode 31 and the rack housing 15 form a capacitance 20 in parallel with a capacitor 53. When the capacitance of the capacitance 20 changes, the combined capacitance of the capacitance 20 and the capacitor 53 changes, and the delay time of the voltage input to a delay time measuring unit 55 via a gate element 54 changes. By measuring this change in delay time using the delay time measuring unit 55, the electronic component 5 can detect the capacitance of the capacitance 20, i.e., the capacitance between the electrode 31 and the rack housing 15, and thereby detect the intrusion of water into the rack housing 15.

[0036] Next, a description will be given of a method for manufacturing the liquid detection sensor 2. The liquid detection sensor 2 is manufactured by the following steps 1 to 7. Step 1: A predetermined length of the sheath 64 of the cable 6 is partially removed to expose the electric wires 61 to 63, and the insulating coatings 612, 622, 632 at the ends of the electric wires 61 to 63 are further removed to expose the core wires 611, 621, 631, thereby performing terminal processing. Step 2: The wires 61 to 63 of the terminated cable 6 are inserted into the lead-out holes 710a, 710b, and 710c of the first member 71 of the cable holder 7, and the wires 61 to 63 are held in the holding grooves 715a, 715b, and 715c of the wire holding portion 715. Step 3: The first member 71 and the second member 72 of the cable holder 7 are combined together. Step 4: A portion of the cable 6, the cable holder 7, the electrode member 3, and the collar 91 are placed in a mold, and molten resin is injected into the mold to form the case body 81, thereby obtaining the case body 81 in which the cable 6, the cable holder 7, the electrode member 3, and the collar 91 are insert-molded. Step 5: The substrate 4 is positioned and fixed to the cable holder 7 inside the case body 81. Step 6: The tips of the electric wires 61 to 63 extending from the cable holder 7 are connected to the through-hole lands 41 to 43 of the board 4 on which the electronic component 5 is mounted, and the connection wire portion 32 of the electrode member 3 is connected to the through-hole land 40 of the board 4. Step 7: The case body 81 and the case lid 82 are combined, and the O-ring 92 is attached to the seal holding portion 814 of the case body 81. It should be noted that these steps 1 to 7 are shown as an example, and the liquid detection sensor 2 may be manufactured by other steps as long as the liquid detection sensor 2 of this embodiment is ultimately obtained.

[0037] (Effects of the embodiment) According to the embodiment described above, for example, when water infiltrates into the rack housing 15 through a damaged portion of the boots 181, 182 and a certain amount of infiltrated water W accumulates around the electrode 31, the infiltration of water can be detected with a high degree of certainty.

[0038] (Summary of the embodiment) Next, the technical ideas grasped from the above-described embodiments will be described by using the reference numerals and the like in the embodiments. However, the reference numerals in the following description do not limit the components in the claims to the members and the like specifically shown in the embodiments.

[0039] [1] A liquid detection sensor (2) for detecting intrusion of a liquid into a waterproof housing (rack housing 15) of a detection target device (steering device 1), the liquid detection sensor (2) having an electrode (31) inserted into a through hole formed in the housing (15), and detecting intrusion of a liquid into the housing (15) by a change in the electrostatic capacitance of the electrode (31).

[0040] [2] The liquid detection sensor (2) described in [1] above, wherein the housing (15) is electrically grounded, and detects the intrusion of liquid into the housing (15) by a change in capacitance between the electrode (31) and the housing (15).

[0041] [3] The liquid detection sensor (2) according to [2] above, wherein the electrode (31) is disposed within the through-hole (150) without extending further inward than the inner surface (15a) of the housing (15).

[0042] [4] The liquid detection sensor (2) described in [1] above, further comprising an electronic component (5) that detects the capacitance between the electrode (31) and the housing (15), a substrate (4) on which the electronic component (5) is mounted, and an electrode member (3) that has the electrode (31), wherein the electrode member (3) has a connection line portion (32) that connects the electrode (31) and the substrate (4).

[0043] [5] The liquid detection sensor (2) described in [4] above, further comprising: a cable (6) having a plurality of electric wires (61-63) connected to board electrodes (through-hole lands 41-43) formed on the board (4) and a sheath (64) that collectively covers the plurality of electric wires (61-63); and a sensor case (8) that houses the board (4) and the electrode member (3), wherein the sheath (64) is welded to the sensor case (8).

[0044] [6] The liquid detection sensor (2) described in [5] above, further comprising a cable holder (7) that accommodates a portion of the longitudinal direction of each of the plurality of electric wires (61 to 63) that are led out from the sheath (64), and each tip end of the plurality of electric wires (61 to 63) that protrudes from the cable holder (7) is connected to the substrate electrode (41 to 43).

[0045] [7] The liquid detection sensor (2) according to the above [6], wherein the cable holder (7) is formed with a recess (711c) for accommodating the electronic component (5).

[0046] [8] A liquid detection sensor (2) according to any one of [1] to [7] above, wherein the detection target device (1) is a steering device of a vehicle, and the housing (15) is a rack housing that accommodates a rack shaft (14).

[0047] Although the embodiments of the present invention have been described above, the invention according to the claims is not limited to the above embodiments. It should be noted that not all of the combinations of features described in the embodiments are necessarily essential to the means for solving the problems of the invention. The present invention can be appropriately modified and implemented without departing from the spirit of the invention, and can be modified as follows, for example.

[0048] In the above embodiment, the electrode 31 of the electrode member 3 is described as having a circular flat plate shape, but the shape of the electrode is not limited to this and may be, for example, a cylindrical shape parallel to the inner surface of the through-hole 150 of the rack housing 15. In this case, the capacitance changes due to water that has infiltrated between the electrode and the through-hole 150, and the infiltration of water can be detected by this change in capacitance. Also, the liquid detection sensor may be provided with multiple electrodes, or electrodes may be formed on the substrate of the liquid detection sensor using copper foil residue, and the electrodes of this substrate may be inserted into the through-hole 150.

[0049] Furthermore, in the above embodiment, the case where the liquid detection sensor 2 detects the intrusion of water into the rack housing 15 of the steering device 1 of a vehicle has been described, but the liquid detection sensor of the present invention may also be used to detect the intrusion of liquids such as water into detection target devices other than the steering device 1. Furthermore, the liquid whose intrusion is detected by the liquid detection sensor of the present invention is not limited to water, and the liquid detection sensor of the present invention can be used to detect the intrusion of various liquids into a housing. [Explanation of symbols]

[0050] 1...Steering device (detection target device) 14...Rack shaft 15...Rack housing (housing) 150...Through hole 2...Liquid detection sensor 3...Electrode member 31...electrode 32...connecting line portion 4... Board 41 to 43... Through-hole lands (board electrodes) 5...Electronic components 6...Cables 61~63... Wire 64... Sheath 7...Cable holder 711c...Concave 8...Sensor case 815...Outlet part W…Intrusion water

Claims

1. A liquid detection sensor that detects intrusion of a liquid into a waterproof housing of a detection target device, an electrode inserted into a through hole formed in the housing; detecting the intrusion of liquid into the housing based on a change in capacitance of the electrode; Liquid detection sensor.

2. the housing is electrically grounded; detecting the intrusion of liquid into the housing based on a change in capacitance between the electrode and the housing; The liquid detection sensor according to claim 1 .

3. The electrode is disposed in the through hole without extending further inward than the inner surface of the housing. The liquid detection sensor according to claim 2 .

4. an electronic component for detecting capacitance between the electrode and the housing; a substrate on which the electronic components are mounted; an electrode member having the electrode, The electrode member has a connection line portion that connects the electrode and the substrate. The liquid detection sensor according to claim 1 .

5. a cable including a plurality of electric wires connected to substrate electrodes formed on the substrate and a sheath covering the plurality of electric wires; a sensor case that houses the substrate and the electrode member, The sheath is welded to the sensor case. The liquid detection sensor according to claim 4 .

6. a cable holder configured to accommodate a portion of each of the plurality of electric wires in the longitudinal direction led out from the sheath; a tip end of each of the plurality of electric wires protruding from the cable holder being connected to the board electrode; The liquid detection sensor according to claim 5 .

7. The cable holder has a recess formed therein for accommodating the electronic component. The liquid detection sensor according to claim 6 .

8. the detection target device is a steering device of a vehicle, The housing is a rack housing that accommodates a rack shaft. The liquid detection sensor according to any one of claims 1 to 7.

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