JP7533473B2 - Position detection device and liquid level detection device - Google Patents

Description

The present invention relates to a position detection device and a liquid level detection device equipped with the same.

For example, Patent Document 1 discloses a position detection device that uses eddy currents to detect the position of an object. The position detection device disclosed in Patent Document 1 includes an excitation winding that forms a magnetic field, a sensing winding in which an induced electromotive force is generated by the magnetic field formed by the excitation winding, and an electrically conductive screen that rotates relative to the sensing winding to change the degree to which it shields the sensing winding (see FIG. 53 in the same document, etc.). The position detection device disclosed in Patent Document 1 detects the position of an object based on the induced electromotive force that changes in accordance with the rotational movement of the screen.

Japanese Unexamined Patent Publication No. 159101/1986

Depending on how it is used, the position detection device as described above may require redundancy in order to maintain position detection accuracy even after a failure occurs in part of the sensor. In order to ensure redundancy, multiple position detection devices with the above configuration may be provided, but this would require a large amount of space (mounting space) to attach the position detection devices to a given device.

The present invention has been made in consideration of the above-mentioned situation, and aims to provide a position detection device and a liquid level detection device equipped with the same that can ensure redundancy while preventing the installation space from becoming too large.

In order to achieve the above object, a position detection device according to a first aspect of the present invention comprises:
A position detection device for detecting a position of an object,
a magnetic excitation unit formed on the substrate and excited by application of a voltage;
a detection unit having a plurality of detection coils formed in an annular region around an axis of the substrate, the detection unit generating an induced electromotive force by the excitation unit;
a non-magnetic metal portion that rotates about the axis in response to the change in position, and changes an induced electromotive force generated in the detection portion in accordance with the position;
a control unit that calculates the position based on an induced electromotive force generated in the detection unit,
The detection portion is provided at a plurality of positions different from each other in a radial direction centered on the axis.

In order to achieve the above object, a liquid level detection device according to a second aspect of the present invention comprises:
The position detection device is provided,
the object is a float that floats on a liquid,
The control unit detects a liquid level position of the liquid according to the calculated position.

According to the present invention, it is possible to ensure redundancy while suppressing the increase in installation space.

The upper figure is a schematic side view of the position detection device according to the first embodiment of the present invention, and the lower figure is a schematic plan view of a circuit board for explaining each annular region on the circuit board. FIG. 2 is a functional block diagram of a circuit board. 1B is a diagram showing a first annular region of a circuit board in a plan view, and is a diagram for explaining the patterns of a first excitation portion and a first detection portion formed in the first annular region. FIG. The upper and lower figures are schematic diagrams for explaining wiring patterns etc. which are in an equivalent relationship with each other. 4 is a schematic diagram showing the arrangement of a first excitation unit, a first detection unit, a second excitation unit, and a second detection unit in a plan view. FIG. 13 is a bottom view of the interlocking portion, showing an example of a formation of the nonmagnetic metal portion. FIG. 13 is a bottom view of the interlocking portion, showing another example of the formation of the nonmagnetic metal portion. FIG. 6 is a diagram showing the relationship between an output voltage from a first detection unit and a rotational position of an object. FIG. FIG. 11 is a diagram for explaining an example of a method for calculating a rotational position. FIG. 11 is a diagram for explaining an example of a method for calculating a rotational position. FIG. 11 is a schematic plan view of a circuit board according to a second embodiment, illustrating each annular region in the circuit board. FIG. 11 is a functional block diagram of a circuit board according to a second embodiment. FIG. 11 is a schematic diagram of a liquid level detection device according to a third embodiment. The upper figure is a schematic side view of a position detection device including a circuit board according to a modified example, and the lower figure is a schematic plan view of the circuit board according to the modified example.

A display device according to one embodiment of the present invention will be described with reference to the drawings.

First Embodiment
The position detection device 1 of this embodiment detects the rotational position of an object 2 rotating around an axis line AX, as shown in the upper diagram of Figure 1, and includes a circuit board 100 and an interlocking part 200 that rotates together with the object 2 around the axis line AX.

The circuit board 100 is made of, for example, a printed circuit board, and is configured by providing various circuits and electronic components on an insulating plate-shaped substrate (substrate) 3. The substrate 3 is formed with a through hole H1 through which a shaft 4 connected to an object 2 passes. The shaft 4 is supported by a bearing (not shown) so as to be rotatable about the axis AX. As shown in the upper and lower diagrams of FIG. 1, the circuit board 100 has a first annular region R1, a second annular region R2, and another annular region Ro as annular regions formed about the axis AX. The circuit board 100 also has an outer peripheral region Rx on the outer periphery of the other annular region Ro. As shown in the lower diagram of FIG. 1, the circuit board 100 has, in order from the center side of the axis AX, the through hole H1, the first annular region R1, the second annular region R2, and the other annular region Ro, each formed in a concentric shape centered on the axis AX. In the upper and lower diagrams of FIG. 1, various circuits and electronic components provided on the circuit board 100 are omitted for ease of viewing.

As shown in FIG. 2, the circuit board 100 includes a first excitation unit 10, a first detection unit 20, a second excitation unit 30, a second detection unit 40, and a control unit 50.

The first excitation unit 10 is excited by the application of voltage under the control of the control unit 50, and has two excitation coils 11, 12 formed within the first annular region R1, as shown in Figure 3.

The excitation coil 11 is formed in a circular shape on the center side of the first annular region R1, and the excitation coil 12 is formed in a circular shape on the outer peripheral end of the first annular region R1. Each of the excitation coils 11 and 12 is a coil with a plurality of windings, and is formed, for example, by printing a conductor such as aluminum (Al), silver palladium (Ag/Pd), or gold (Au) on the upper surface of the substrate 3 (the surface on the interlocking part 200 side in the upper diagram of FIG. 1). A voltage is applied to each of the excitation coils 11 and 12 from a terminal not shown.

The first excitation unit 10 may be composed of one of the excitation coils 11, 12. The substrate 3 constituting the circuit board 100 may be a laminated substrate, and the conductive patterns constituting the excitation coils 11, 12 may be provided on the surfaces of each of the laminated substrates to increase the number of windings to form a strong magnetic field.

The first detection unit 20 is a part in which an induced electromotive force is generated by the magnetic field formed by the excited first excitation unit 10, and has two detection coils 21, 22 formed within the first annular region R1, as shown in Figure 3.

The main parts of each of the detection coils 21, 22 are formed by printing a conductor such as aluminum (Al), silver-palladium (Ag/Pd), or gold (Au) on the upper surface of the substrate 3.

3, the detection coil 21 has a pair of ends T1s, T1e electrically connected to the control unit 50, and has a first portion 21a, a second portion 21b, and a third portion 21c as portions electrically connecting one end T1s to the other end T1e. The first portion 21a has one end connected to the end T1s, and is formed in an arc extending clockwise from the end T1s side through the outer periphery of the excitation coil 11, and the other end connected to the second portion 21b. The second portion 21b is a portion formed by folding back from the other end of the first portion 21a. The second portion 21b has one end connected to the first portion 21a, and is formed in an arc extending counterclockwise from the one end side through the outer periphery of the excitation coil 11, and the other end connected to the third portion 21c. The third portion 21c is a portion formed by folding back the other end of the second portion 21b. One end of the third portion 21c is connected to the second portion 21b, and the third portion 21c is formed in an arc shape extending clockwise from the one end side, and the other end is connected to the end portion T1e. As a result, the detection coil 21 is approximately in the shape of a figure eight as shown in FIG. 3.

3, the detection coil 22 has a pair of ends T2s, T2e electrically connected to the control unit 50, and has a first portion 22a, a second portion 22b, and a third portion 22c as portions electrically connecting one end T2s to the other end T2e. The first portion 22a has one end connected to the end T2s, and is formed in an arc extending clockwise from the end T2s side through the outer periphery of the excitation coil 11, and the other end connected to the second portion 22b. The second portion 22b is a portion formed by folding back from the other end of the first portion 22a. The second portion 22b has one end connected to the first portion 22a, and is formed in an arc extending counterclockwise from the one end side through the outer periphery of the excitation coil 11, and the other end connected to the third portion 22c. The third portion 22c is a portion formed by folding back the other end of the second portion 22b. One end of the third portion 22c is connected to the second portion 22b, and the third portion 22c is formed in an arc shape extending clockwise from the one end side, and the other end is connected to the end portion T2e. As a result, the detection coil 22 is approximately in the shape of a figure eight as shown in FIG. 3.

At the points where a part of the detection coil 21 intersects with another part, where a part of the detection coil 22 intersects with another part, and where the detection coil 21 intersects with the detection coil 22, one intersecting wire is insulated from the other intersecting wire by using an insulating layer, a through hole, a via hole, etc. (not shown). As the insulating layer, for example, silicon dioxide (SiO ₂ ) or tantalum pentoxide (Ta ₂ O ₅ ), which is the material of the base material 3, can be used. Specifically, the locations where one wiring intersects with the other wiring are (A) a location where the first portion 21a and the second portion 21b of the detection coil 21 intersect, (B) a location where the first portion 22a and the second portion 22b of the detection coil 22 intersect, (C) a location where the first portion 21a of the detection coil 21 intersects with each of the second portion 22b and the first portion 22a of the detection coil 22, (D) a location where the second portion 21b of the detection coil 21 intersects with each of the third portion 22c, the second portion 22b, and the first portion 22a of the detection coil 22, and (E) a location where the third portion 21c of the detection coil 21 intersects with the first portion 22a of the detection coil 22. In FIG. 3, one of the wirings at such intersecting locations is indicated by a dotted line.

The detection coil 21 and the detection coil 22 are formed on the circuit board 100 so that they have a phase difference of 90° when considering the angle centered on the axis AX. Here, the annular form of the first excitation unit 10 and the first detection unit 20 described above (schematically shown in the lower diagram of FIG. 4) can be considered equivalent to the form shown in the upper diagram of FIG. 4, in which the circumferential direction centered on the axis AX is replaced with a linear direction and developed into a band shape. In other words, the forms shown in the upper diagram of FIG. 4 and the lower diagram of FIG. 4 are in an equivalent relationship. The form shown in the upper diagram of FIG. 4 is a form in which the detection coil 21 and the detection coil 22, which are sine wave or cosine wave shaped and have a phase difference of 90°, are arranged inside the rectangular first excitation unit 10 (excitation coil 12 in this embodiment). Here, if the detection coil 21 is considered to have a shape based on a sine curve, the detection coil 22 is shaped based on a cosine curve. Considering the above-mentioned equivalent relationship, even in the annular first detection unit 20, the detection coil 21 has a shape based on a sine curve, and the detection coil 22 has a shape based on a cosine curve.

The second excitation unit 30 and the second detection unit 40 are formed in the second annular region R2 as shown in Figure 5. The specific shapes and compositions of the second excitation unit 30 and the second detection unit 40 are similar to those of the first excitation unit 10 and the first detection unit 20 described with reference to Figure 3, and therefore will not be described here.

The second excitation unit 30 is excited by the application of a voltage under the control of the control unit 50, and has two excitation coils 31 and 32 formed in the second annular region R2 as shown in FIG. 5. The excitation coil 31 is formed in a circular shape on the center side of the second annular region R2, and the excitation coil 32 is formed in a circular shape on the outer peripheral end of the second annular region R2. A voltage is applied to each of the excitation coils 31 and 32 from a terminal not shown. The second excitation unit 30 may be composed of one of the excitation coils 31 and 32. In addition, the substrate 3 constituting the circuit board 100 may be a laminated substrate, and the number of windings may be increased to form a strong magnetic field by providing a conductive pattern constituting the excitation coils 31 and 32 on the surface of each of the laminated substrates.

The second detection unit 40 is a portion in which an induced electromotive force is generated by the magnetic field formed by the excited second excitation unit 30, and has two detection coils 41, 42 formed in the second annular region R2 as shown in Fig. 5. The detection coils 41 and 42 are formed on the circuit board 100 so that they have a phase difference of 90° when considering the angle centered on the axis line AX. The detection coils 41, 42 of the second detection unit 40 have shapes based on sine waves or cosine waves having a phase difference of 90° from each other, similar to the detection coils 21, 22 of the first detection unit 20.

Next, before describing the control unit 50, the interlocking unit 200 will be described. As shown in the upper diagram of FIG. 1, the interlocking unit 200 has a plate-shaped portion 210 attached to the shaft 4 and a non-magnetic metal portion 220 provided on the lower surface (the surface facing the circuit board 100) of the plate-shaped portion 210. The plate-shaped portion 210 is made of, for example, resin and is formed in a circular shape as shown in FIG. 6A. A through hole H2 for fixing the shaft 4 is provided in the center of the plate-shaped portion 210. The non-magnetic metal portion 220 is provided on the lower surface of the plate-shaped portion 210 and is formed in a semicircular shape as shown in FIG. 6A. The non-magnetic metal portion 220 is provided at a position that covers the first detection unit 20 and the second detection unit 40 (the first annular region R1 and the second annular region R2), and is formed of a non-magnetic metal material that is not magnetized by the magnetic field formed by the first excitation unit 10 and the second excitation unit 30, such as aluminum (Al) or copper (Cu).

The interlocking unit 200 configured as described above rotates and moves with the object 2 around the axis AX relative to the first detection unit 20 and the second detection unit 40 formed on the circuit board 100. An eddy current is generated in the non-magnetic metal part 220 by the excitation of the first excitation unit 10 and the second excitation unit 30, and the generated eddy current acts to reduce the electromagnetic coupling action between the first excitation unit 10 and the first detection unit 20 and between the second excitation unit 30 and the second detection unit 40. When the part covered by the non-magnetic metal part 220 in the first detection unit 20 and the second detection unit 40 changes with the rotation of the object 2, the voltage (induced electromotive force) induced in the first detection unit 20 and the voltage (induced electromotive force) induced in the second detection unit 40 each change. Based on the change in the induced electromotive force generated in this way, the control unit 50 calculates the rotational position of the object 2.

If the non-magnetic metal part 220 can be configured to rotate together with the shaft 4, the plate-shaped part 210 may be omitted from the interlocking part 200. The non-magnetic metal part 220 may be a sector shape other than a semicircular shape, and may be formed into a sector shape having any central angle (for example, about 70° to 90°).

The non-magnetic metal part 220 may have a first arc part 221 and a second arc part 222 formed in an arc shape centered on the axis line AX, as shown in FIG. 6B. The first arc part 221 and the second arc part 222 shown in FIG. 6B are provided at a distance from each other in the radial direction centered on the axis line AX. The first arc part 221 is provided at a position facing the first detection part 20 in the direction along the axis line AX (the vertical direction in the upper diagram of FIG. 1). The second arc part 222 is provided at a position facing the second detection part 40 in the direction along the axis line AX (the vertical direction in the upper diagram of FIG. 1). By dividing the non-magnetic metal portion 220 in this manner and providing a first arc portion 221 corresponding to the first excitation portion 10 and the first detection portion 20 and a second arc portion 222 corresponding to the second excitation portion 30 and the second detection portion 40, it is possible to suppress the occurrence of eddy current action due to the first excitation portion 10 and the first detection portion 20 in the second arc portion 222, and to suppress the occurrence of eddy current action due to the second excitation portion 30 and the second detection portion 40 in the first arc portion 221. As a result, it is possible to suppress the mutual interference between the electromagnetic action of the first excitation portion 10 and the first detection portion 20 and the electromagnetic action of the second excitation portion 30 and the second detection portion 40, which leads to a decrease in detection accuracy.

The control unit 50 has a DSP (Digital Signal Processor), an oscillator that converts a DC voltage from a power source (not shown) into an AC voltage under the control of the DSP and applies it to each of the first excitation unit 10 and the second excitation unit 30, and an ADC (Analog to Digital Converter) that converts a voltage (analog signal) output by the generation of an induced electromotive force in each of the detection coils 21 and 22 of the first detection unit 20 into a digital signal and supplies it to the DSP. An amplifier may be provided between the detection coils 21 and 22 and the ADC.

The DSP of the control unit 50 applies an AC voltage to the excitation coils 11 and 12 that constitute the first excitation unit 10 via an oscillator, exciting the first excitation unit 10. The magnetic field formed by the excited first excitation unit 10 generates an induced electromotive force in each of the detection coils 21 and 22 that constitute the first detection unit 20. The DSP acquires the induced electromotive forces generated in each of the detection coils 21 and 22 as output voltages V1a and V1b that are converted into digital signals via an ADC. Here, the output voltages V1a and V1b corresponding to the induced electromotive force that changes due to the non-magnetic metal part 220 that rotates around the axis AX together with the object 2 are as shown in FIG. 7.

Figure 7 shows the changes in output voltages V1a and V1b with respect to angle θ when the object 2 is in an arbitrary rotational position and the angle θ at which the value of output voltage V1a based on detection coil 21 becomes 0 is set to 0°. In this case, the change in output voltage V1a based on detection coil 21 with respect to angle θ can be expressed as V1a = α sin(θ) (α is a constant). Meanwhile, the change in output voltage V1b based on detection coil 22 with respect to angle θ can be expressed as V1b = α cos(θ). The DSP of control unit 50 calculates angle θ, i.e., the rotational position of object 2, based on the values of output voltage V1a and output voltage V1b.

The DSP of the control unit 50 calculates the angle θ based on the acquired output voltages V1a and V1b, for example, as follows: The DSP first calculates V1a/V1b=V1c, and calculates the relationship between the output voltages from both the detection coil 21 and the detection coil 22 and the angle θ. It can be seen that V1c depends on the angle θ, since V1c=V1a/V1b=αsin(θ)/αcos(θ)=tan(θ).

Here, the data of θ=F(V1) is stored in advance in the memory (ROM (Read Only Memory)) of the DSP as a function F (see FIG. 8B) created based on θ=arctan(V1c), which is the inverse function Fi (see FIG. 8A) of V1c=tan(θ). The function F shown in FIG. 8B is a continuation of the discontinuous parts that occur when the angle θ is 90° or 270° in the inverse function Fi shown in FIG. 8A, and is obtained by translating the range of 90° to 270° of the inverse function Fi by +v and translating the range of 270° to 360° of the inverse function Fi by +2v. Note that v is a constant that can be calculated in advance based on the inverse function Fi. The data of the function F stored in the memory of the DSP is preferably data of a formula that defines the function F, but may also be data of a table configured by associating the output voltage V1 with the angle θ.

The DSP calculates the angle θ indicating the rotational position of the object 2 based on the V1c calculated as above and the data of the function F previously stored in the memory. Specifically, when V1a (=αsin(θ)) is positive and V1b (=αcos(θ)) is positive, the angle θ is between 0° and 90°, so the DSP sets the calculated V1c as V1 as is and substitutes this V1 into the function F to calculate the angle θ (the rotational position of the object 2). When V1b (=αcos(θ)) is negative, the angle θ is between 90° and 270°, so the DSP adds v to the calculated V1c to set the output voltage V1, and substitutes this V1 into the function F to calculate the angle θ (the rotational position of the object 2). Furthermore, when V1a (=α sin(θ)) is negative and V1b (=α cos(θ)) is positive, the angle θ is between 270° and 360°, so the DSP adds 2v to the calculated V1c to obtain the output voltage V1, and substitutes this V1 into the function F to calculate the angle θ (the rotational position of the object 2). In this manner, the DSP calculates the angle θ corresponding to the rotational position of the object 2 in the range of 0° to 360°. The DSP may output the calculated digital data of the angle θ to an external device as is, or may convert it into an analog signal via an ADC (Analog to Digital Converter) before outputting it to an external device.

The DSP of the control unit 50 also applies an AC voltage to the excitation coils 31 and 32 constituting the second excitation unit 30 via an oscillator to excite the second excitation unit 30. The magnetic field formed by the excited second excitation unit 30 generates an induced electromotive force in each of the detection coils 41 and 42 constituting the second detection unit 40. The DSP acquires the induced electromotive forces generated in each of the detection coils 41 and 42 as output voltages V2a and V2b converted into digital signals via an ADC. Here, the output voltage V2a corresponding to the induced electromotive force that changes due to the non-magnetic metal part 220 rotating around the axis AX together with the object 2 changes according to the angle θ in the same manner as the output voltage V1a described above, and the output voltage V2b corresponding to the induced electromotive force changes according to the angle θ in the same manner as the output voltage V1b described above. The DSP of the control unit 50 calculates the angle θ based on the output voltages V2a and V2b from the second detection unit 40 in a manner similar to the manner in which the angle θ is calculated based on the output voltages V1a and V1b from the first detection unit 20.

For example, the DSP of the control unit 50 first calculates the angle θ based on the output voltages V1a and V1b from the first detection unit 20. If it is determined that there is no abnormality in the calculated angle θ, it determines the angle θ calculated based on the output voltages V1a and V1b as the rotational position of the object 2. On the other hand, if (i) the difference between the angle θ calculated based on the output voltages V1a and V1b and a previously calculated angle (for example, the previous value of the angle θ calculated based on the output voltages V1a and V1b) becomes larger than the value previously stored in the memory, or (ii) the angle θ calculated based on the output voltages V1a and V1b indicates an error value, the DSP determines the angle θ calculated based on the output voltages V2a and V2b as the rotational position of the object 2. In this way, in the position detection device 1, two systems are provided, one consisting of the first excitation unit 10 and the first detection unit 20, and the other consisting of the second excitation unit 30 and the second detection unit 40, and the rotational position of the target object 2 is calculated using either of the two systems as necessary, so that redundancy can be ensured. In addition, the first annular region R1 in which the first excitation unit 10 and the first detection unit 20 are formed, and the second annular region R2 in which the second excitation unit 30 and the second detection unit 40 are formed are formed in a concentric shape centered on the axis line AX on the circuit board 100, so that the position detection device 1 can be made smaller than when conventional position detection devices are simply arranged side by side. As a result, the space (mounting space) for mounting the position detection device 1 can be prevented from becoming large.

In addition, if the DSP of the control unit 50 determines that there is no abnormality in the calculated angle θ, it may calculate the average value of the angle θ calculated based on the output voltages V1a and V1b and the angle θ calculated based on the output voltages V2a and V2b, and use the calculated average value as the rotational position of the object 2.

The DSP of the control unit 50 may also determine whether or not an abnormality occurs in the value (V1c = V1a / V1b) before calculating the angle θ based on the function F. In this case, the DSP of the control unit 50 first calculates V1c based on the output voltages V1a and V1b from the first detection unit 20. If it is determined that there is no abnormality in the calculated V1c, the DSP determines the angle θ calculated based on the output voltages V1a and V1b as the rotation position of the object 2. On the other hand, if (i) the difference between the V1c calculated this time and the V1c calculated in the past (for example, the previous value of V1c) becomes larger than the value stored in advance in the memory, or (ii) the V1c calculated this time indicates an error value, the DSP determines the angle θ calculated based on the output voltages V2a and V2b as the rotation position of the object 2. Furthermore, when either V1a or V1b indicates an abnormal value, the DSP may determine that the angle θ calculated based on the output voltages V2a and V2b is the rotational position of the target object 2.

Various components of the DSP IC and the like of the control unit 50, as well as EMC (Electro Magnetic Compatibility) countermeasures components (not shown), such as ceramic capacitors and ground patterns, are mounted on at least one of the upper and lower surfaces of the other annular region Ro of the circuit board 100. Note that at least some of the components of the control unit 50 and the EMC countermeasures components may be mounted on the outer peripheral region Rx located on the outer periphery of the other annular region Ro of the circuit board 100, or on another circuit board electrically connected to the circuit board 100.

The position detection device 1 including the above-described parts is housed, for example, in a housing (not shown). The housing sets the distance between the non-magnetic metal part 220 of the interlocking part 200 and the upper surface of the circuit board 100 to a desired value. The smaller the distance between the non-magnetic metal part 220 and the circuit board 100, the larger the induced voltage will be, and it is preferable to set it to, for example, about 1.0 to 1.5 mm. This concludes the explanation of the first embodiment.

From here on, other embodiments that differ from the first embodiment in some configurations, etc. will be described. Below, the same components as in the first embodiment will be described using the same reference numerals as in the first embodiment, and the differences from the first embodiment will be mainly described.

Second Embodiment
As shown in FIG. 9, the circuit board 100 according to the second embodiment (which is provided in a similar configuration to the position detection device 1 described above) has a first annular region R1, a second annular region R2, a third annular region R3, and another annular region Ro as annular regions formed around the axis AX. The circuit board 100 according to the second embodiment also has an outer peripheral region Rx on the outer peripheral side of the other annular regions Ro. As shown in FIG. 9, the through hole H1, the first annular region R1, the second annular region R2, the third annular region R3, and the other annular regions Ro are formed in the circuit board 100 in the order from the center side of the axis AX in a concentric shape around the axis AX. In FIG. 9, various circuits and electronic components provided on the circuit board 100 are omitted in consideration of the ease of viewing the drawing.

As shown in FIG. 10, the circuit board 100 of the second embodiment includes a third excitation unit 60 and a third detection unit 70 in addition to the first excitation unit 10, first detection unit 20, second excitation unit 30, second detection unit 40, and control unit 50, which are configured similarly to the first embodiment.

The third excitation unit 60 and the third detection unit 70 are formed within the third annular region R3 shown in Figure 9. The specific shapes and compositions of the third excitation unit 60 and the third detection unit 70 are similar to those of the first excitation unit 10 and the first detection unit 20 described with reference to Figure 3, and therefore will not be described here.

The third excitation unit 60 is excited by the application of a voltage under the control of the control unit 50, and has two excitation coils (not shown) formed within the third annular region R3. One of the two excitation coils is formed in a circular shape on the central side of the third annular region R3, and the other is formed in a circular shape at the outer peripheral end of the third annular region R3. A voltage is applied to each of the two excitation coils under the control of the control unit 50. The third excitation unit 60 may be composed of one of the two excitation coils.

The third detection unit 70 is a portion in which an induced electromotive force is generated by the magnetic field formed by the excited third excitation unit 60, and has two detection coils 71, 72 formed within the third annular region R3. The detection coils 71 and 72 are formed on the circuit board 100 so that they have a phase difference of 90° when considering the angle centered on the axis AX. The detection coils 71, 72 of the third detection unit 70 have shapes based on sine waves or cosine waves having a phase difference of 90°, similar to the detection coils 21, 22 of the first detection unit 20 described above.

In the second embodiment, the non-magnetic metal part 220 is not shown, but is provided in a position covering the first detection unit 20, the second detection unit 40, and the third detection unit 70 (first annular region R1, second annular region R2, and third annular region R3). As the object 2 rotates, when the parts covered by the non-magnetic metal part 220 in not only the first detection unit 20 and the second detection unit 40 but also the third detection unit 70 change, the voltage (induced electromotive force) induced in the third detection unit 70 also changes. In the second embodiment, the control unit 50 calculates the rotational position of the object 2 based on the change in the induced electromotive force generated in not only the first detection unit 20 and the second detection unit 40 but also the third detection unit 70.

Although not shown, in the second embodiment, the non-magnetic metal part 220 may also be formed in an arc shape centered on the axis line AX and have a plurality of arc portions spaced apart from one another in the radial direction centered on the axis line AX. The plurality of arc portions are arranged to face each of the plurality of detection parts (the first detection part 20, the second detection part 40, and the third detection part 70).

In the second embodiment, the DSP of the control unit 50 obtains the output voltages V1a and V1b from the first detection unit 20 and obtains the output voltages V2a and V2b from the second detection unit 40, as described above. Furthermore, the DSP applies an AC voltage to the third excitation unit 60 via an oscillator to excite the third excitation unit 60. The magnetic field formed by the excited third excitation unit 60 generates an induced electromotive force in each of the detection coils 71 and 72 constituting the third detection unit 70. The DSP obtains the induced electromotive forces generated in each of the detection coils 71 and 72 as output voltages V3a and V3b converted into digital signals via an ADC. The DSP calculates the angle θ based on the output voltages V3a and V3b from the third detection unit 70 in a manner similar to the method of calculating the angle θ based on the output voltages V1a and V1b and the output voltages V2a and V2b.

In the second embodiment, the DSP of the control unit 50 calculates the angle θ (hereinafter referred to as the first angle) based on the output voltages V1a and V1b, the angle θ (hereinafter referred to as the second angle) based on the output voltages V2a and V2b, and the angle θ (hereinafter referred to as the third angle) based on the output voltages V3a and V3b. The DSP determines the rotational position of the object 2 based on one or more reliable values of the first to third angles calculated in this manner. Specifically, if the DSP determines that the calculated first to third angles contain abnormal values as described in the first embodiment, it excludes the angle that shows the abnormal value and determines the rotational position of the object 2. For example, if the third angle shows an abnormal value, the DSP determines the first angle or the second angle as the rotational position of the object 2, or determines the average value of the first angle and the second angle as the rotational position of the object 2. Also, for example, if the second angle and the third angle indicate abnormal values, the DSP determines the first angle as the rotational position of the object 2. Also, for example, the DSP may select two angles having a small difference between the calculated first to third angles, and determine one of the two selected angles or the average value of the two selected angles as the rotational position of the object 2. Also, if none of the calculated first to third angles indicate an abnormal value, the DSP may determine the angle θ calculated based on an output voltage from a predetermined detection unit as the rotational position of the object 2, or may determine the average of all of the first to third angles as the rotational position of the object 2.

The DSP of the control unit 50 may determine whether an abnormality occurs in the values at the previous stage used to calculate the angle θ based on the function F. The previous values may be V1a/V1b, V2a/V2b, V3a/V3b, or V1a, V1b, V2a, V2b, V3a, V3b. If an abnormality occurs in the values at the previous stage used to calculate the angle θ, the DSP does not calculate the angle θ from the voltage that showed an abnormal value, but calculates the angle θ based on the voltage that did not show an abnormal value. When there are multiple angles θ calculated in this way, they may be handled in the same manner as described in the previous paragraph.

According to the second embodiment described above, the control unit 50 can calculate the rotational position of the object 2 based on the induced electromotive force generated in one or two of the three detection units (first detection unit 20, second detection unit 40, third detection unit 70). As a result, even if an abnormality occurs in a specific detection unit (or the excitation unit corresponding to the specific detection unit), the rotational position of the object 2 can be calculated, and redundancy can be better ensured. This concludes the explanation of the second embodiment.

Third Embodiment
The object 2 that is the subject of rotational position detection in the position detection device 1 of the first and second embodiments described above is not limited, but from here on, we will explain a third embodiment in which the object 2 is a float 2M that floats on liquid, as shown in Figure 11, and the position detection device 1 of the first or second embodiment is applied to a liquid level detection device 1M.

The liquid level detection device 1M of the third embodiment is for detecting the position of the liquid level of a liquid (fuel, etc.) in a tank of a vehicle such as an automobile, and comprises a position detection device 1 having a configuration similar to that described above, a float 2M as an object 2, and an arm 4M as a shaft 4.

The float 2M is made of hard foam rubber or the like and is roughly shaped like a bale; it receives buoyancy from the liquid in the tank and floats on the liquid surface, displacing as the liquid level changes. The arm 4M is a metal rod, one end of which is attached to the float 2M, and the other end is supported on the circuit board 100 side so that it can rotate around the axis AX. Therefore, the float 2M also rotates around the axis AX in response to changes in the liquid level. The arm 4M is formed by bending so that the float 2M can reach the liquid.

The DSP of the control unit 50 of the circuit board 100 calculates the angle θ calculated based on the output voltage from a predetermined detection unit as described above, as the rotational position of the float 2M. The DSP then detects the liquid level position based on function data and table data that pre-store in memory and that define the relationship between the rotational position of the float 2M and the liquid level position of the liquid. The DSP may transmit data on the calculated angle θ to an external device (not shown) (e.g., an in-vehicle device equipped with a microcomputer), and the external device that receives the angle θ data may detect the liquid level position according to the angle θ. In this case, the external device is also included in the configuration of the liquid level detection device 1M.

As described above, the position detection device 1 can ensure redundancy while preventing the installation space from becoming too large, so the liquid level detection device 1M equipped with the position detection device 1 can also ensure redundancy while preventing the installation space from becoming too large. This concludes the explanation of the third embodiment.

Note that the present invention is not limited to the above-described embodiments and drawings. Appropriate modifications (including the deletion of components) may be made without departing from the spirit of the present invention.

(Modification)
In the circuit board 100, the other annular region Ro and the outer peripheral region Rx may be formed integrally without distinction. The circuit board 100 may be formed in a disk shape along the outer edge of the other annular region Ro. The outer peripheral region Rx may be formed in a part of the outside of the other annular region Ro, not over the entire circumference of the outside of the other annular region Ro. For example, as shown in the upper and lower figures of FIG. 12, the position detection device 1 may include a circuit board 100M according to a modified example. As shown in the lower figure of FIG. 12, the circuit board 100M according to the modified example is configured by providing the various circuits and electronic components described above on a base material 3M having a shape combining a semicircular shape and a rectangular shape. In the circuit board 100M according to the modified example, the through hole H1, the first annular region R1, the second annular region R2, and the other annular region Ro are each formed in a concentric shape centered on the axis AX. The outer peripheral region Rx is formed in a part on the outer peripheral side of the other annular region Ro, specifically, on the right side of the outer periphery in the lower diagram of FIG.

In addition, in the above explanation, an example was given of one control unit 50 for multiple detection units, but a structure in which a control unit is provided for each detection unit may also be used. In addition, in the above, an example was given of a coil formed on the upper surface of the substrate 3, 3M, but it is also possible to form the coil on the lower surface or the upper and lower surfaces of the substrate 3, 3M. In addition, in the above, an example was given of a DSP being used for the control unit 50, but it is also possible to use a microcomputer and peripheral ICs instead of a DSP.

Although the above describes an example in which the position detection device 1 detects the rotational position of the object 2 rotating around the axis AX, this is not limiting. The position detection device 1 may be configured so that the non-magnetic metal part 220 rotates around the axis AX in response to a change in the position of the object 2, and may detect the position of the object 2 that moves other than rotational movement (such as linear movement or curved movement). For example, if the position detection device 1 is configured so that the non-magnetic metal part 220 rotates around the axis AX in response to the linear movement of the object 2, the control unit 50 can detect the position of the object 2 that moves linearly in accordance with the angle θ that can be calculated as described above.

The figure shows an example in which a gap is provided between adjacent annular regions (e.g., the first annular region R1 and the second annular region R2) on the circuit board 100, but the two annular regions may be adjacent to each other as long as there is no interference between the circuit formed in one annular region and the circuit formed in the other annular region.

The output voltage V1a and the output voltage V1b based on the first detection unit 20 only need to have a predetermined phase difference from each other. For example, the predetermined phase difference may be 45° or 135°. However, from the viewpoint of determining V1a/V1b according to tan(θ), it is preferable that the predetermined phase difference is 90° as described in the above embodiment. This is because this can suppress the complication of processing. The same applies to the output voltages V2a, V2b based on the second detection unit 40 and the output voltages V3a, V3b based on the third detection unit 70.

In the second embodiment, an example in which three detection units are provided is shown, but it is also possible to provide four or more detection units. In this case, annular regions corresponding to the number of detection units to be increased may be provided between the third annular region R3 of the circuit board 100 and the other annular regions Ro. In other words, the control unit 50 only needs to be able to calculate the rotational position of the object 2 based on the induced electromotive force generated in a number of detection units that is less than the specific number of detection units that are three or more. In this way, even if an abnormality occurs in a specific detection unit, the rotational position of the object 2 can be calculated, and redundancy can be well ensured. In addition, even when four or more detection units are provided, the non-magnetic metal part 220 may be provided with multiple arc portions that face each of the multiple detection units.

The shape and arrangement of the excitation section are not limited to the above examples and can be arbitrary as long as it can form a magnetic field that generates an induced electromotive force in the corresponding detection section.

The above describes an example in which a through hole H1 into which a shaft 4 can be inserted is provided in the base material 3 of the circuit board 100, but if the non-magnetic metal part 220 can rotate around the axis AX together with the object 2 and an appropriate distance can be maintained between the non-magnetic metal part 220 and the circuit board 100, it is not necessary to provide a through hole H1 in the base material 3.

Furthermore, the object 2 to be detected by the position detection device 1 can be any object that moves, and can be selected according to the purpose. For example, the object 2 may be any rotating object mounted on a vehicle (such as an accelerator pedal, brake pedal, or rotating light that moves in a rotating manner) or a linearly moving object such as a shift lever. According to the position detection device 1 described above, it is possible to calculate the position of the object 2 (which may be a rotational position or a linear position) according to the calculated angle θ while ensuring redundancy.

(1) The position detection device 1 described above detects the position of the object 2, and includes an excitation unit (e.g., the first excitation unit 10 and the second excitation unit 30), a detection unit (e.g., the first detection unit 20 and the second detection unit 40), a non-magnetic metal unit 220, and a control unit 50. The excitation unit is formed on a substrate (e.g., the circuit board 100) and is excited by application of a voltage. The detection unit has a plurality of detection coils (e.g., the first annular region R1 and the second annular region R2) formed in an annular region centered on the axis AX on the substrate, and an induced electromotive force is generated by the excitation unit. The non-magnetic metal unit 220 rotates around the axis AX as the position of the object 2 changes, and changes the induced electromotive force generated in the detection unit according to the position of the object 2. The control unit 50 calculates the position of the object 2 based on the induced electromotive force generated in the detection unit. A plurality of detection portions (for example, a first detection portion 20 and a second detection portion 40) are provided at different positions in the radial direction centered on the axis line AX.
As described above, this configuration makes it possible to ensure redundancy while preventing the space for mounting the position detection device 1 (mounting space) from becoming large.

(2) In the position detection device 1 according to the second embodiment, a specific number of detection units, three or more, are provided, and the control unit 50 is capable of calculating the position of the object 2 based on the induced electromotive force generated in a number of detection units, the number of which is less than the specific number.
By doing this, even if an abnormality occurs in a specified detection unit (or an excitation unit corresponding to the specified detection unit), the position of the target object 2 can be calculated, and redundancy can be better ensured.

(3) The non-magnetic metal portion 220 has an arc portion formed in an arc shape centered on the axis line AX, and the arc portions are provided at intervals in the radial direction centered on the axis line AX, and the multiple arc portions (e.g., the first arc portion 221, the second arc portion 222) face each of the multiple detection portions (e.g., the first detection portion 20, the second detection portion 40).
As described above, this configuration can prevent the electromagnetic action of a given detector from interfering with the other detectors, thereby preventing a decrease in detection accuracy.

(4) Specifically, the magnetic excitation unit includes an excitation coil formed in a ring-shaped region and is provided in multiple units corresponding to each of the multiple detection units (for example, a first magnetic excitation unit 10 provided in correspondence with the first detection unit 20, a second magnetic excitation unit 30 provided in correspondence with the second detection unit 40, etc.).

(5) Specifically, two detection coils are provided for one detection unit. The control unit 50 obtains a first output voltage (e.g., output voltage V1a) that changes in a sine wave or cosine wave shape according to the rotational position of the target 2 from one of the two coils (e.g., detection coil 21) in which an induced electromotive force is generated by exciting the excitation unit, and obtains a second output voltage (e.g., output voltage V1b) that changes in a sine wave or cosine wave shape according to the rotational position of the target 2 from the other of the two coils (e.g., detection coil 22) and has a phase difference with the first output voltage, and the control unit 50 calculates the position of the target 2 based on the first output voltage and the second output voltage.

(6) A liquid level detection device 1M according to a third embodiment includes the above-described position detection device 1. The object 2 is a float 2M that floats on the liquid. The liquid level detection device 1M detects the liquid level position of the liquid according to the position of the object 2 (float 2M) calculated by the control unit 50.
According to this configuration, as described above, it is possible to prevent the liquid level detection device 1M from becoming large, while ensuring redundancy.

In the above explanation, explanations of well-known technical matters have been omitted as appropriate in order to facilitate understanding of the present invention.

1: Position detection device, 1M: Liquid level detection device 2: Object, 2M: Float, AX: Axis 100: Circuit board, 3: Base material R1-R3: First to third annular regions, Ro: Other annular regions, Rx: Outer peripheral region 10: First excitation section (11, 12: Excitation coil)
20: first detection unit (21, 22: detection coil)
30: second excitation unit (31, 32: excitation coil)
40: second detection unit (41, 42: detection coil)
50: control unit 60: third excitation unit 70: third detection unit (71, 72: detection coil)
200: Interlocking portion, 210: Plate-shaped portion, 220: Non-magnetic metal portion, 221: First arc portion, 222: Second arc portion, Fi: Inverse function, F: Function

Claims (5)

A position detection device for detecting a position of an object,
a magnetic excitation unit formed on the substrate and excited by application of a voltage;
a detection unit having a plurality of detection coils formed in an annular region around an axis of the substrate, the detection unit generating an induced electromotive force by the excitation unit;
a non-magnetic metal portion that rotates about the axis in response to the change in position, and changes an induced electromotive force generated in the detection portion in accordance with the position;
a control unit that calculates the position based on an induced electromotive force generated in the detection unit,
The detection portion is provided at a plurality of different positions in a radial direction around the axis ,
The magnetic excitation unit includes a magnetic excitation coil formed in the annular region, and is provided in a plurality of units corresponding to the plurality of detection units.
Position detection device. The detection units are provided in a specific number of three or more,
the control unit is capable of calculating the position based on induced electromotive forces generated in a number of the detection units that is less than the specific number of the detection units, among the specific number of the detection units.
The position detection device according to claim 1 . the non-magnetic metal portion has an arc portion formed in an arc shape about the axis,
The arc portion is provided in a plurality of portions spaced apart from each other in the radial direction,
The plurality of arcuate portions face each of the plurality of detection portions.
3. The position detection device according to claim 1 or 2. Two detection coils are provided for one detection unit,
the control unit obtains a first output voltage, which varies in a sine wave or cosine wave manner depending on the position, from one of the two detection coils in which an induced electromotive force is generated by exciting the excitation unit, and obtains a second output voltage, which varies in a sine wave or cosine wave manner depending on the position, from the other of the two detection coils and has a phase difference with the first output voltage;
The control unit calculates the position based on the first output voltage and the second output voltage.
The position detection device according to any one of claims 1 to 3 . A position detection device according to any one of claims 1 to 4 ,
the object is a float that floats on a liquid,
detecting a liquid level position of the liquid in accordance with the position calculated by the control unit;
Liquid level detection device.

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