JP2010008228A - Liquid level detecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid level detecting apparatus having a shorter length of a coil to reduce an effect of external noise, being applicable to a small liquid container, and capable of simplifying a structure of the liquid container. <P>SOLUTION: A magnetic force applied from a magnet 131 of a float 130 to a magnetic substance of a sensor 140 is increased or decreased along with a fluctuation of a liquid level L. As a result, permeability within the coil of the sensor 140 is increased or decreased, changing an inductance of the coil. A voltage generated by the coil varies according to this change, allowing a detection of the liquid level L, from relations between the generated voltage and the liquid level L. Since the inductance of the coil is changed by increasing or decreasing an amount of an external magnetic field to be applied from the float 130 to the sensor 140, the apparatus can shorten the length of the coil and simplify a structure of a reservoir tank 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid level detection device, and in particular, shortens a coil length to reduce the influence of external noise and simplifies the structure of a liquid container while enabling application to a small liquid container. The present invention relates to a liquid level detecting device capable of performing the above.

  The liquid level detecting device is used for detecting the liquid level of a liquid such as gasoline, oil, fluid or cooling water of an automobile, and a so-called float type liquid level detecting device is known. This float type liquid level detecting device is disclosed in Japanese Patent Laid-Open No. 63-96424.

According to this liquid level detecting device, a coil standing in a liquid container and subjected to a density density treatment, a magnetic material with a float that is housed in the coil and floats in the liquid, and a coil And an LC oscillation circuit that applies a voltage to the float, and the magnetic substance with a float moves up and down in the coil following the increase and decrease of the liquid level, thereby changing the inductance of the coil and changing the oscillation frequency of the LC oscillation circuit. Let Accordingly, the liquid level can be detected based on the relationship between the liquid level and the oscillation frequency (Patent Document 1).
Japanese Unexamined Patent Publication No. 63-96424 (for example, FIG. 2)

  However, in the above-described conventional technology, it is necessary to give the coil a length equivalent to the moving region of the magnetic substance with the float (that is, the fluctuation region of the liquid level), so that the length of the coil becomes long. was there. Therefore, the wiring length of the coil becomes long, and it is easy to be affected by external noise (for example, a road heater embedded in a road). Moreover, since the space occupied by the coil increases, it is difficult to apply to a small liquid container.

  Furthermore, in the above-described conventional technique, the magnetic body with the float is configured to move up and down in the coil. Therefore, the magnetic body with the float needs to be configured to float in the liquid while the coil is separated from the liquid. In addition, there is a problem that the structure of the liquid container is complicated.

  The present invention has been made to solve the above-described problems. The coil length is shortened to reduce the influence of external noise, and the liquid container can be applied to a small liquid container. An object of the present invention is to provide a liquid level detecting device capable of simplifying the structure.

  In order to achieve this object, the liquid level detection device according to claim 1 detects the liquid level in the liquid container in which the liquid is stored, has a magnet, and detects the liquid in the liquid container. A sensor member having a floating float member, a magnetic body and a coil wound around the magnetic body, voltage applying means for applying a time-varying voltage to the coil of the sensor member, and the coil of the sensor member Circuit means having voltage detecting means for detecting a voltage, and the float member and the sensor member are arranged at positions separated from each other along the direction of change of the liquid level in the liquid container, When the float member is moved following the change in the liquid level, the strength of the magnetic force applied from the magnet of the float member to the magnetic body of the sensor member is increased or decreased. Inductance of is change.

  The liquid level detecting device according to claim 2 is the liquid level detecting device according to claim 1, wherein the coil of the sensor member is wound at an equal pitch.

  The liquid level detecting device according to claim 3 is the liquid level detecting device according to claim 1 or 2, wherein the voltage applied to the coil of the sensor member by the voltage applying means of the circuit means is a rectangular voltage. is there.

  The liquid level detecting device according to claim 4 is the liquid level detecting device according to any one of claims 1 to 3, wherein the sensor member is disposed on a back surface side of a bottom plate constituting a bottom portion of the liquid container. Has been.

  The liquid level detecting device according to claim 5 is the liquid level detecting device according to claim 4, wherein the bottom plate of the liquid container is positioned so as to recede from the liquid level relative to the first bottom plate and the first bottom plate. And a second bottom plate having an opening for supplying the liquid to the outside. The sensor member is disposed on the back side of the first bottom plate.

  According to the liquid level detection apparatus of claim 1, when the liquid level is changed and the float member is moved up and down following the change in the liquid level, the float member The spacing distance from the sensor member is changed, and the strength of the magnetic force applied from the magnet of the float member to the magnetic body of the sensor member is increased or decreased. As a result, the magnetic permeability in the coil is increased or decreased, and the inductance of the coil is changed.

  For example, when the float member approaches the sensor member, the magnetic force applied from the magnet of the float member to the magnetic body of the sensor member increases, thereby reducing the magnetic permeability in the coil and reducing the inductance of the coil. On the other hand, when the float member is moved away from the sensor member, the magnetic force applied from the magnet of the float member to the magnetic body of the sensor member is weakened, thereby increasing the magnetic permeability in the coil and increasing the inductance of the coil.

  In this case, when a time-varying voltage is applied to the coil of the sensor member by the voltage applying means, the waveform of the generated voltage generated in the coil is changed according to the inductance state of the coil. Therefore, the generated voltage is detected by the voltage detecting means, so that the liquid level can be detected based on the relationship between the detection result (voltage) and the liquid level.

  Thus, according to the liquid level detection apparatus of the present invention, the float member includes the magnet, the sensor member includes the magnetic body included in the coil, and the float member is detected as the liquid level changes. In this configuration, the inductance of the coil is changed by increasing or decreasing the amount of external magnetic field applied from the float member to the sensor member.

  Therefore, the length of the coil is set to the same length as the float moving area (that is, the liquid level fluctuation area) as in the conventional product in which the inductance of the coil is changed by changing the position of the float moving up and down in the coil. Since it is not necessary, the length of the coil can be shortened. In addition, unlike the conventional product, there is no need to accommodate the float in the coil, so that the winding diameter of the coil can be reduced.

  As a result, according to the liquid level detecting device of the present invention, the coil length is shortened, so that the coil wiring length can be shortened and the influence of external noise can be reduced accordingly. Moreover, since the coil length is reduced and the winding diameter is reduced, the coil can be reduced in size, and accordingly, the sensor member as a whole can be reduced in size. It can be applied (mounted) to a liquid container.

  Further, according to the liquid level detecting device of the present invention, the float member and the sensor member are arranged at positions spaced apart from each other along the change direction of the liquid level. Unlike the conventional product, it is not necessary to separate the coil from the liquid while the float floats on the liquid in the coil. Therefore, there is an effect that the structure of the liquid container can be simplified.

  According to the liquid level detecting device of the second aspect, in addition to the effect exhibited by the liquid level detecting device of the first aspect, the coil pitch of the coil of the sensor member is wound at an equal pitch. As a result, the production cost can be reduced and the product cost can be reduced. That is, in the configuration in which the density of the winding of the coil is processed as in the conventional product, accuracy is required for the winding work and the number of man-hours increases, resulting in an increase in product cost. On the other hand, in the present invention, since the coil pitch is wound at an equal pitch, the winding accuracy can be relaxed and the number of man-hours can be reduced, thereby reducing the product cost accordingly. be able to.

  Moreover, if the coil pitch of the coil of the sensor member is wound at an equal pitch as described above, the sparse area can be reduced as compared with the case where the winding density needs to be subjected to a sparse / dense process. The number of turns of the coil can be ensured efficiently. That is, if the coil length (winding region) is the same, the number of turns can be increased, and if the number of turns is the same, the length of the coil can be shortened.

  In this case, by increasing the number of windings, the inductance of the coil can be increased, and accordingly, the magnetic body contained in the coil or the magnet of the float member can be reduced, thereby detecting the liquid level. The liquid level detecting device as a whole can be reduced in size and weight while ensuring a possible amount. Alternatively, if the coil inductance can be increased by increasing the number of turns, the separation distance between the float member and the sensor member can be increased. However, it is possible to increase the detectable amount of the liquid level.

  On the other hand, by reducing the length of the coil, the sensor member can be reduced in size, and accordingly the size of the entire liquid level detection device can be reduced. The liquid level detecting device can be applied (mounted) to a smaller liquid container while ensuring the above.

  It should be noted that such equal pitching of the coil pitch cannot be employed in a conventional product that changes the inductance of the coil by changing the position of the float that moves up and down in the coil. Can be adopted for the first time by adopting a configuration in which the inductance of the coil is changed by increasing or decreasing the amount of external magnetic field applied from the float member to the sensor member. As a result, it is possible to simultaneously achieve downsizing of the liquid level detecting device and securing of a detectable amount of the liquid level.

  According to the liquid level detecting device of claim 3, in addition to the effect exhibited by the liquid level detecting device of claim 1 or 2, a rectangular voltage is applied to the coil of the sensor member by the voltage applying means of the circuit means. Since it is a structure, it is easy to make the influence of the change of the inductance of the coil due to the vertical movement of the float member appear in the detection voltage waveform, and it is possible to improve the detection accuracy. In other words, if the voltage waveform applied to the coil is a relatively smooth waveform such as a sin wave in order to suppress a sudden change in voltage, the influence of the inductance change appears in the detected voltage waveform. It is difficult to cause a decrease in detection accuracy. On the other hand, a signal with a large rise and fall can be created by applying a rectangular voltage to the coil as in the liquid level detection device of the present invention, so the effect of changes in inductance is detected. The detection accuracy can be improved by making the voltage waveform easy to appear.

  According to the liquid level detecting device of the fourth aspect, in addition to the effect of the liquid level detecting device according to any one of the first to third aspects, a sensor member is provided on the back surface side of the bottom plate constituting the bottom of the liquid container. Therefore, the liquid container does not need to have a structure in which the sensor member can be disposed, and only the float member can be disposed in the liquid container. As a result, it is possible to simplify the structure of the liquid container and reduce the product cost.

  In addition, such a structure in which only the sensor member is attached to the outside of the liquid container cannot be used in a conventional product that changes the inductance of the coil by changing the position of the float that moves up and down in the coil. As described above, the float member is moved close to and away from the sensor member, and the amount of external magnetic field applied from the float member to the sensor member is increased or decreased, so that the coil inductance can be changed for the first time. As a result, it is possible to simultaneously reduce the size of the liquid level detection device and simplify the structure of the liquid container.

  According to the liquid level detecting device of the fifth aspect, in addition to the effect exhibited by the liquid level detecting device according to the fourth aspect, the bottom plate of the liquid container has a first bottom plate and a liquid level lower than the first bottom plate. And a second bottom plate that opens and has a supply port that supplies liquid to the outside, and the sensor member is disposed on the back side of the first bottom plate, that is, lower than the sensor member. Since the supply port is positioned at the position, when the float member comes into contact with the sensor member due to a drop in the liquid level, it becomes impossible to move the float member further (that is, detection of the liquid level). However, even if it becomes impossible, an interval can be provided between the liquid surface and the supply port so that air can be prevented from being mixed into the supply port.

  Further, in this case, there is an effect that an area with high resolution can be allocated to an area where the liquid level is lowered to a predetermined position (warning level) and a warning is required. That is, according to the liquid level detection apparatus of the present invention, since the inversely proportional relationship is established between the liquid level (the separation distance between the float member and the sensor member) and the detection voltage, the liquid level is lowered. Accordingly, in the case of a configuration in which the float member approaches the sensor member, as the liquid level decreases (the float member approaches the sensor member), the change in the detection voltage with respect to the unit fluctuation of the liquid level increases (the resolution is reduced). Higher).

  Therefore, when the sensor member is disposed on the back surface side of the second bottom plate, the liquid level near the warning level is detected in the region before the resolution is increased. If the sensor member is arranged on the back side of the first bottom plate, the liquid level near the warning level can be detected in the region where the resolution is highest.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1A is a top view of the reservoir tank 1 on which the liquid level detection device 100 according to one embodiment of the present invention is mounted, and FIG. 1B is a front view of the reservoir tank 1. FIG. 2 is a cross-sectional view of the reservoir tank 1 taken along the line II-II in FIG.

  The reservoir tank 1 is one of the components of the brake system that controls the brake pressure of the vehicle. The reservoir tank 1 is configured as a liquid container that supplies and stores brake fluid according to the volume change of the hydraulic system. It is attached to a cylinder (not shown). As shown in FIG. 2, the float member 130 and the sensor member 140 of the liquid level detecting device 100 (see FIG. 4) are attached to the reservoir tank 1.

  As shown in FIGS. 1 and 2, the reservoir tank 1 mainly includes a tank body 10 and a cap 20. The tank body 10 is formed in a box shape having an internal space S from a synthetic resin material, and the brake fluid is stored in the internal space S and the float member 130 of the liquid level detecting device 100 is stored.

  As shown in FIGS. 1 and 2, the tank body 10 includes a bottom plate 11 that constitutes the bottom of the liquid container, and four side plates 12 that stand from the edge of the bottom plate 11 and that constitute the side walls of the liquid container. The top plate 13 connecting the standing ends of the side plates 12 to form the ceiling of the liquid container, and the guide tube 14 standing from the bottom plate 11 are rectangular in a top view (see FIG. 1A). It is configured as a rectangular parallelepiped.

  As shown in FIG. 2, the bottom plate 11 includes a first bottom plate 11a, a pair of second bottom plates 11b positioned so as to recede from the first bottom plate 11a in a direction away from the top plate 13 (downward in FIG. 2), A pair of connecting bottom plates 11c that connect the first bottom plate 11a and the second bottom plate 11b to each other are provided.

  Here, as shown in FIG. 2, the pair of second bottom plates 11 b are positioned with the first bottom plate 11 a interposed therebetween. Therefore, a space (space surrounded by the first bottom plate 11a and the pair of connecting bottom plates 11c) that is recessed toward the top plate 13 side is formed on the bottom surface side (the lower side in FIG. 2) of the bottom plate 11. Using the space, the sensor member 140 of the liquid level detection device 100 (see FIG. 4) is disposed on the bottom surface side of the first bottom plate 11a.

  The sensor member 140 is stored in a box-shaped storage member 21 that is open on one side (the upper side in FIG. 2), and the storage member 21 is sealed on the back side of the bottom plate 11a. It is stored in the storage space of the storage member 21 in a sealed state.

  As shown in FIG. 2, the pair of second bottom plates 11b includes supply ports 11b1 and 11b2. The supply port 11b1 is an opening through which oil fluid flows in and out between the internal space S of the reservoir tank 1 and the master cylinder, and the supply port 11b2 is pumped from the internal space S of the reservoir tank 1 (not shown). It is an opening for supplying oil fluid. Each of these supply ports 11b1 and 11b2 communicates with a master cylinder and a pump via a hose h.

  The top plate 13 includes an inlet 13a as shown in FIG. The inlet 13a is an opening used when the brake fluid is replenished to the internal space S of the master cylinder 1, and is closed by a cap 20 that is detachably mounted as shown in FIGS. .

  The guide cylinder 14 is a cylindrical member for guiding the float member 130 of the liquid level detection device 100 (see FIG. 4), and as shown in FIG. 2, the top plate 13 extends from the surface side of the first bottom plate 11a. It is erected towards. The inner diameter of the guide cylinder 14 is slightly larger than the outer diameter of the float member 130 of the liquid level detecting device 100, and the float member 130 accommodated on the inner peripheral side is moved to a sensor when the liquid level L changes. Guide to the member 140 in the direction of approaching and separating.

  As shown in FIG. 2, a plurality of communication ports 14a are opened at the base of the guide tube 14 (the connection portion with the first bottom plate 11a), and the inside and outside of the guide tube 14 are formed by these communication ports 14a. Is communicated. As a result, when the brake fluid flows in / out from the supply ports 11b1 and 11b2 to the master cylinder or the like and the liquid level L is changed, the liquid level L is equalized inside and outside the guide cylinder 14. Has been.

  The float member 130 is a part of the components of the liquid level detection device 100 (see FIG. 4), and is configured to move up and down within the guide tube 14 as the liquid level L varies. Specifically, the float member 130 includes a magnet 131 and a resin body 132, as shown in FIG.

  The magnet 131 is a permanent magnet that generates a magnetic field (magnetic force), and is embedded in the resin body 132. In the present embodiment, the magnet 131 is composed of a ferrite magnet. However, other types of magnets may be used. Examples of other magnets include alnico magnets, samarium cobalt magnets, and neodymium magnets.

  The resin body 132 is a float for keeping the position of the magnet 131 with respect to the liquid level constant (float). The resin body 132 is formed of a resin material in a columnar shape and is configured to float on the brake fluid when the magnet 131 is embedded. Has been. As described above, the outer diameter of the resin body 132 is slightly smaller than the inner diameter of the guide cylinder 14, and the movement is restricted by the guide cylinder 14, and only in the vertical direction (the fluctuation direction of the liquid level L). It is possible to move to.

  The sensor member 140 is a part of the components of the liquid level detection device 100 (see FIG. 4). When the float member 130 moves up and down with the fluctuation of the liquid level L, the sensor member 140 Is disposed at a position where the separation distance is changed (that is, in the region corresponding to the guide tube 14 on the back surface side of the bottom plate 11a). Here, with reference to FIG. 3, the detailed structure of the sensor member 140 is demonstrated.

  3 (a) is a top view of the sensor member 140, FIG. 3 (b) is a front view of the sensor member 140, and FIG. 3 (c) is taken along the line IIIc-IIIc in FIG. 3 (a). 4 is a cross-sectional view of a sensor member 140. FIG. In FIG. 3, connection lines for electrically connecting the terminal 144 to the outside are omitted.

  As shown in FIG. 3, the sensor member 140 is electrically connected to the magnetic body 141, the bobbin 142 that houses the magnetic body 141, the coil 143 wound around the bobbin 142, and the coil 143. A terminal 144.

  As shown in FIG. 3, the magnetic body 141 is made of a ferrous sintered metal into a round bar shape with a circular cross section, and is fitted into the inner peripheral portion of the bobbin 142. The bobbin 142 is made of a synthetic resin material, and includes a cylindrical body part into which the magnetic body 141 is fitted, and a pair of projecting parts 142a and 142b projecting in a flange shape from the body part radially outward. Prepare.

  The coil 143 is wound on the outer peripheral surface of the bobbin 142 between the pair of overhang portions 142a and 142b so as to be stacked in a plurality of layers at an equal pitch. Therefore, the accuracy can be relaxed and the number of man-hours can be reduced as compared with the case where the density is applied to the winding density, so that the product cost can be reduced accordingly.

  In addition, in this way, if the coil pitch of the coil 143 (FIG. 3 (c) vertical pitch) is a constant pitch, the sparse region is compared with the case where the winding density is subjected to the sparse / dense processing. Therefore, the number of turns of the coil 143 can be efficiently ensured.

  That is, if the length of the coil 143 (FIG. 3 (c) vertical dimension) is the same, the number of turns can be increased. Therefore, the inductance of the coil 143 is increased, and the coil 143 is included by that amount. The magnetic body 141 or the magnet 131 of the float member 130 can be made small. Therefore, it is possible to reduce the size and weight of the entire liquid level detecting device 100 while securing a detectable amount of the liquid level.

  If the inductance of the coil 143 can be increased by increasing the number of windings, the separation distance between the float member 130 (see FIG. 2) and the sensor member 140 can be further increased, so that the liquid level can be detected. While the enlargement of the device 100 itself is suppressed, the detectable amount of the liquid level can be increased.

  On the other hand, if the number of windings is equal, the length of the coil 143 (the vertical dimension in FIG. 3C) can be shortened, so that the liquid level detecting device 100 as a whole can be miniaturized. Therefore, the liquid level detecting device 100 can be applied (mounted) to a smaller liquid container while securing a detectable amount of the liquid level.

  Returning to FIG. 1 and FIG. As described above, the sensor member 140 is disposed on the back surface side of the bottom plate 11, and in the present embodiment, the axial direction of the magnetic body 141 (the vertical direction in FIG. 3C) is the liquid level L. It is made to correspond to the change direction (up and down direction in FIG. 2).

  According to the reservoir tank 1 configured as described above, when the liquid level L in the reservoir tank 1 is changed, the float member 130 is guided by the guide tube 14 in the vertical direction following the change. It is moved (vertically moved in the vertical direction in FIG. 2). When the float member 130 is moved up and down, the separation distance between the float member 130 and the sensor member 140 is changed with the up and down movement, and the magnetic body 141 of the sensor member 140 is changed from the magnet 131 of the float member 130. The strength of the magnetic force applied to (see FIG. 3) is increased or decreased. As a result, the magnetic permeability in the coil 143 (see FIG. 3) is increased or decreased, and the inductance is changed.

  Here, in the present embodiment, as shown in FIG. 2, the sensor member 140 is arranged on the back surface side of the bottom plate 11 constituting the bottom of the reservoir tank 1. That is, it is not necessary to have a structure in which the sensor member 140 is disposed in the reservoir tank 1, and only the float member 130 is disposed in the reservoir tank 1. As a result, the structure of the reservoir tank 1 can be simplified and the product cost can be reduced.

  In addition, as described above, the reservoir tank 1 in the present embodiment has the bottom plate 11 positioned so as to recede from the liquid surface (top plate 13) with respect to the first bottom plate 11a and the first bottom plate 11a, and the brake fluid. Are provided with a pair of second bottom plates 11b in which supply ports 11b1 and 11b2 are opened, and a sensor member 140 is disposed on the back side of the first bottom plate 11a.

  That is, since the supply ports 11b1 and 11b2 are positioned lower than the sensor member 140, the float member 130 comes into contact with the sensor member 140 due to the decrease in the liquid level L, and the float member 130 moves further. Even when the liquid level becomes impossible (that is, when the liquid level L cannot be detected), a space is provided between the liquid level and the supply ports 11b1 and 11b2, and air is supplied to the supply ports 11b1 and 11b2. Can be mixed.

  In this case, a region with high resolution can be assigned to a region where the liquid level L is lowered to a predetermined position (warning level) and a warning is required. That is, in the liquid level detection apparatus 100 according to the present embodiment, an inversely proportional relationship is established between the liquid level L (the separation distance between the float member 130 and the sensor member 140) and the detection voltage Va (FIG. 5). reference).

  Therefore, in the case of the present embodiment in which the float member 130 approaches the sensor member 140 as the liquid level L decreases, as the liquid level L decreases (that is, between the float member 130 and the sensor member 140). As the separation distance decreases, the change in the detection voltage Va with respect to the unit fluctuation of the liquid level L can be increased (that is, the resolution can be increased).

  Therefore, when the sensor member 140 is disposed on the back surface side of the second bottom plate 11b, a region before the resolution is increased (that is, a state in which the separation distance between the float member 130 and the sensor member 140 is large, for example, While the liquid level near the warning level is detected in L2) of FIG. 5, the sensor member 140 is disposed on the back side of the first bottom plate 11a as in the present embodiment. The liquid level near the warning level can be detected in the region where the resolution is the highest (that is, in the state where the separation distance between the float member 130 and the sensor member 140 is sufficiently small, for example, L1 in FIG. 5). As a result, detection at a position with high resolution becomes possible.

  Next, the detailed configuration of the liquid level detection device 100 will be described with reference to FIGS. 4 and 5. FIG. 4A is a block diagram illustrating the electrical configuration of the liquid level detection device 100. FIGS. 4B and 4C illustrate the oscillation voltage applied to the coil 143 by the oscillation power supply 151. FIG. FIG. 6 is a schematic diagram schematically showing a time change of Vi and a time change of the detection voltage Va detected by the signal detection circuit 152;

  In FIG. 4A, the float member 130 is schematically illustrated. In FIG. 4C, a waveform corresponding to the oscillation voltage Vi is illustrated by a broken line, and two types of detection voltages Va when the inductance of the coil 143 changes are illustrated by solid lines S1 and S2.

  FIG. 5 is a schematic diagram schematically showing the relationship between the liquid level L and the detection voltage Va. The liquid level L is a distance from the surface of the second bottom plate 11b of the reservoir tank 1 to the liquid level of the brake fluid (see FIG. 2), and increases as the liquid level is further away from the second bottom plate 11b. The detection voltage Va is a voltage detected by the signal detection circuit 152.

  The liquid level detecting device 100 is a device for detecting the liquid level L of the brake fluid in the reservoir tank 1, and as shown in FIG. 4A, a float member 130, a sensor member 140, a circuit, The circuit device 150 includes an oscillation power source 151 that applies a predetermined voltage to the coil 143 of the sensor member 140, and the coil 143 of the sensor member 140 that is applied with the predetermined voltage by the oscillation power source 151. A signal detection circuit 152 for detecting the generated voltage and a resistor R are mainly provided and connected to the sensor member 140.

  4A, the output terminal of the oscillation power supply 151 is connected to one end of the resistor R, and the other end of the resistor R is the detection terminal of the signal detection circuit 152. Is connected to one end of the coil 143 of the sensor member 140. The other end of the coil 143 is connected to the other detection terminal of the signal detection circuit 152 and the ground terminal of the oscillation power supply 151. Note that the ground terminal of the oscillation power supply 151 is grounded.

  Here, the oscillation power supply 151 is a power supply that oscillates a rectangular wave with a predetermined frequency, and the oscillation power supply 151 applies the oscillation voltage Vi having a rectangular waveform shown in FIG. 4B to the coil 143 of the sensor member 140. Is done. Since the signal detection circuit 152 is connected in parallel with the coil 143 of the sensor member 140 as described above, the voltage generated in the coil 143 can be detected.

  In this case, when the liquid level L of the reservoir tank 1 is changed and the float member 130 is moved up and down following the change in the liquid level L, the float member 130 and the sensor member 140 are moved along with the vertical movement. , And the strength of the magnetic force applied from the magnet 131 of the float member 130 to the magnetic body 141 of the sensor member 140 is increased or decreased. As a result, the magnetic permeability in the coil 143 is increased or decreased, and the inductance of the coil 143 is changed.

  Specifically, when the liquid level L decreases and the float member 130 approaches the sensor member 140 (the float member 130 moves in the direction of arrow D in FIG. 4A), the sensor from the magnet 131 of the float member 130 By increasing the magnetic force applied to the magnetic body 141 of the member 140, the magnetic permeability in the coil 143 is reduced, and the inductance of the coil 143 is reduced.

  On the other hand, when the liquid level L rises and the float member 130 moves away from the sensor member 140 (the float member 130 moves in the direction of arrow U in FIG. 4A), the magnet 131 of the float member 130 moves away from the sensor member 140. When the magnetic force applied to the magnetic body 141 is weakened, the magnetic permeability in the coil 143 is increased, and the inductance of the coil 143 is increased.

  Therefore, when a rectangular waveform oscillation voltage Vi (see FIG. 4B) is applied from the oscillation power supply 151 to the coil 143 of the sensor member 140, the inductance state of the coil 143 (that is, the state of the liquid level L). Accordingly, the waveform of the detection voltage Va generated in the coil 143 and detected by the signal detection circuit 152 is changed (see FIG. 4C).

  That is, when the inductance of the coil 143 decreases due to the decrease in the liquid level L (the proximity of the float member 130 to the sensor member 140), the detected voltage Va oscillates as indicated by the solid line S1 in FIG. The waveform substantially follows the voltage Vi (rises substantially the same as the oscillation voltage Vi).

  On the other hand, when the inductance of the coil 143 increases due to the increase in the liquid level L (the separation of the float member 130 from the sensor member 140), the detected voltage Va oscillates as indicated by the solid line S2 in FIG. The rise is further delayed with respect to the voltage Vi. Therefore, the detection voltage Va has a waveform that gradually rises to the peak voltage of the oscillation voltage Vi.

  Since the relationship between the voltage generated in the coil 143 (that is, the detection voltage Va detected by the signal detection circuit 152) and the liquid level L is obtained in advance as shown in FIG. 5, the signal detection circuit By detecting the voltage of the coil 143 (detection voltages V1, V2 at time t) by the 152, the detection result (detection voltages V1, V2) is used to detect the liquid level L (liquid level L1) as shown in FIG. , L2).

  As described above, in the liquid level detecting device 100 according to the present embodiment, the oscillation power supply 151 applies a rectangular waveform oscillation voltage (rectangular voltage) to the coil 143 of the sensor member 140. The influence of the change in the inductance of the coil 143 due to the movement can be easily expressed in the waveform of the voltage (detection voltage Va) generated in the coil 143, and the detection accuracy can be improved.

  In other words, if the voltage waveform applied to the coil 143 is a relatively smooth waveform such as a sine wave in order to suppress a sudden voltage change in the inductance, the influence of the inductance change appears in the detected voltage waveform. It is difficult to put out and causes a decrease in detection accuracy. On the other hand, if the voltage applied to the coil 143 is a rectangular voltage, a signal with a large rise and fall can be created, so that the influence of the change in inductance can be easily made to appear in the detection voltage waveform, and the detection accuracy. Can be improved.

  The detection of the detection voltage Va of the coil 143 by the signal detection circuit 152 (that is, detection at time t) is performed by monitoring the oscillation voltage Vi by the oscillation power supply 151 by the signal detection circuit 152 and detecting the rising of the oscillation voltage Vi. With the detection, the timer circuit starts timing and is performed at a timing (time t) when a predetermined time has elapsed from the start.

  As described above, according to the liquid level detecting device 100 in the present embodiment, the float member 130 is moved closer to and away from the sensor member 140 as the liquid level L varies, and the sensor member is separated from the float member 130. In this configuration, the inductance of the coil 143 is changed by increasing or decreasing the amount of external magnetic field applied to 140.

  Therefore, the length of the coil is equal to the float movement area (ie, the fluctuation area of the liquid level L) as in the conventional product in which the inductance of the coil is changed by changing the position of the float moving up and down in the coil. Since there is no need to do this, the length of the coil can be shortened. In addition, unlike the conventional product, there is no need to accommodate the float in the coil, so that the winding diameter of the coil can be reduced.

  As a result, by shortening the length of the coil 143, the wiring length of the coil 143 can be shortened, and accordingly, the influence of external noise can be reduced. Further, since the coil 143 is shortened and the winding diameter is reduced, the coil 143 can be miniaturized, and accordingly, the sensor member 140 as a whole can be miniaturized. 100 can be applied (mounted) to a small liquid container (reservoir tank 1).

  Further, according to the liquid level detecting device 100 in the present embodiment, the float member 130 and the sensor member 140 are arranged at positions separated from each other along the changing direction of the liquid level L. Unlike the conventional product in which the coil is moved up and down in the coil, it is not necessary to separate the coil 143 from the brake fluid while the float floats on the brake fluid in the coil.

  That is, it is not necessary to arrange the coil 143 in the internal space S of the reservoir tank 1, and the coil 143 (sensor member 140) can be disposed outside the internal space S, so that the liquid container (reservoir tank 1) The structure can be simplified. As a result, the mold structure for molding the reservoir tank 1 can be simplified and the manufacturing cost can be reduced.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above embodiments, and various improvements and modifications can be made without departing from the spirit of the present invention. It can be easily guessed.

  In the above embodiment, the case where the sensor member 140 is disposed on the bottom plate 11 side of the reservoir tank 1 has been described. However, the present invention is not necessarily limited to this, and it is naturally possible to dispose the sensor member 140 in another position. As another position, the structure arrange | positioned at the top plate 13 side is illustrated, for example.

  That is, in the present embodiment, as the liquid level L decreases, the float member 130 approaches the sensor member 140 and the distance between the two becomes small, but instead, the liquid level L The float member 130 may be separated from the sensor member 140 and the separation distance between the two may be increased as the distance decreases. Even in this case, the inductance of the sensor member 140 (coil 143) can be increased / decreased as the liquid level L varies, so that the generated voltage Va, the liquid level L, and the like, as in the case of the above embodiment. The liquid level L can be detected based on the relationship.

  In the above-described embodiment, the axial direction (the vertical direction in FIG. 3 (c)) of the magnetic body 141 coincides with the changing direction of the liquid level L (that is, the vertical movement direction of the float member 130, the vertical direction in FIG. 2). Although the case where the sensor member 140 is disposed in the orientation has been described, the present invention is not necessarily limited to this, and the direction in which the sensor member 140 is disposed may naturally be another direction.

  For example, when the sensor member 140 is configured to have a shape whose axial direction (FIG. 3 (c) vertical dimension) is longer than the diameter (FIG. 3 (c) horizontal dimension), the axis of the magnetic body 141 is used. The sensor member 140 is disposed such that the center direction (FIG. 3 (c) vertical direction) is perpendicular to the direction of change of the liquid level L (that is, the vertical movement direction of the float member 130, the vertical direction in FIG. 2). Is preferred. Thereby, size reduction as the reservoir tank 1 whole can be achieved.

  In the embodiment described above, the reservoir tank 1 in which the brake fluid is stored is described as an example of the liquid container in which the liquid level detecting device 100 of the present invention detects the liquid level L. However, the present invention is not limited to this. Of course, the present invention can be applied to other liquid containers. As another liquid container, the gasoline container for motor vehicles, oil, or the liquid container in which cooling water is stored is illustrated, for example.

(A) is a top view of the reservoir tank in which the liquid level detection apparatus in one embodiment of the present invention is mounted, and (b) is a front view of the reservoir tank. It is sectional drawing of the reservoir tank in the II-II line | wire of Fig.1 (a). (A) is a top view of a sensor member, (b) is a front view of the sensor member, and (c) is a cross-sectional view of the sensor member taken along line IIIc-IIIc in FIG. 3 (a). (A) is a block diagram illustrating the electrical configuration of the liquid level detection device, and (b) and (c) are detected by a time change of an oscillation voltage applied to a coil by an oscillation power source and a signal detection circuit. It is the schematic diagram which illustrated typically the time change of the detection voltage made. It is the schematic diagram which showed typically the relationship between a liquid level and a detection voltage.

Explanation of symbols

1 Reservoir tank (liquid container)
11 Bottom plate 11a First bottom plate 11b Second bottom plates 11b1, 11b2 Supply port 100 Liquid level detecting device 130 Float member 131 Magnet 140 Sensor member 141 Magnetic body 143 Coil 150 Circuit device (circuit means)
151 Oscillation power supply (voltage application means)
152 Signal detection circuit (voltage detection means)
L Liquid level

Claims (5)

In the liquid level detecting device (100) for detecting the liquid level (L) in the liquid container (1) in which the liquid is stored,
A float member (130) having a magnet (131) and floating in the liquid in the liquid container (1);
A sensor member (140) having a magnetic body (141) and a coil (143) wound around the magnetic body (141);
A voltage applying means (151) for applying a time-varying voltage to the coil (143) of the sensor member (140) and a voltage detecting means (152) for detecting a voltage generated in the coil (143) of the sensor member (140). Circuit means (150) comprising:
The float member (130) and the sensor member (140) are disposed at positions separated from each other along the changing direction of the liquid level (L) in the liquid container (1).
When the float member (130) is moved following the fluctuation of the liquid level (L), the magnet (131) of the float member (130) is moved to the magnetic body (141) of the sensor member (140). The liquid level detecting device (100), wherein the applied magnetic force is increased or decreased to change the inductance of the coil (143).   The liquid level detecting device (100) according to claim 1, wherein the coil (143) of the sensor member (140) is wound at an equal pitch.   3. The liquid according to claim 1, wherein the voltage applied to the coil (143) of the sensor member (140) by the voltage applying means (151) of the circuit means (150) is a rectangular voltage. Surface level detection apparatus (100).   The liquid level according to any one of claims 1 to 3, wherein the sensor member (140) is disposed on a back surface side of a bottom plate (11) constituting a bottom portion of the liquid container (1). Level detection device (100). The bottom plate (11) of the liquid container (1) is located at a position lower than the first bottom plate (11a) and the first bottom plate (11a), and supplies the liquid to the outside (11b1). , 11b2) having a second bottom plate (11b) opened,
The liquid level detecting device (100) according to claim 4, wherein the sensor member (140) is disposed on a back surface side of the first bottom plate (11a).

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