JP4609915B2 - Position detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a position detection device used in various measuring devices and control devices for automobiles, machine tool robots, and the like.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, position detection devices have been used in various measuring devices and control devices for automobiles, machine tool robots, and the like to detect the amount and position of movement of a movable part.
[0003]
An example of such a position detection apparatus is the position detection apparatus proposed by the applicant of the present application in Japanese Patent Application Laid-Open No. 11-141355.
[0004]
As shown in FIG. 9, the position detection device 100 includes magnets 101 and 102, a sensor 103, and a detection circuit 104. The magnets 101 and 102 are configured to move relative to the sensor 103. The detection circuit 104 is connected to the sensor 103.
[0005]
Magnets 101 and 102 are magnetic field generating means and are arranged to generate magnetic fields in opposite directions. The magnets 101 and 102 give the sensor 103 a magnetic field whose strength and direction gradually change as the relative position becomes far. As the magnets 101 and 102, a permanent magnet made of barium ferrite, plastic, rubber, or the like, a permanent magnet made by sintering SmCo, an electromagnet, or the like can be used.
[0006]
The sensor 103 is a magnetic sensing means, which senses the magnetic field applied from the magnets 101 and 102, and converts the strength of the magnetic sensing magnetic field into an electric signal. As the sensor 103, for example, a sensor made by winding a coil made of a conductive material around a core made of a high magnetic permeability material can be used. As the sensor 103, an MR element, a Hall element, an MI element, or the like can be used.
[0007]
The detection circuit 104 includes a circuit for exciting and driving the sensor 103, a circuit for detecting an electric signal output from the sensor 103, and the like. The detection circuit 104 supplies the electrical signal detected by the sensor 103 to, for example, a control circuit that controls the ignition timing of the engine.
[0008]
In the position detection apparatus 100 described above, the sensor 103 senses the magnetic field generated from the magnets 101 and 102, and detects the relative position between the sensor 103 and the magnets 101 and 102 based on the strength of the magnetic field sensed. be able to. In addition, on the straight line connecting the magnets 101 and 102, the direction and strength of the magnetic field change linearly. Therefore, the sensor 103 provided on this straight line can linearly detect the relative position between the sensor 103 and the magnets 101 and 102.
[0009]
The position detection apparatus 100 has a very good magnetic field sensitivity of the sensor 103, and can detect the relative position even when the relative positions of the magnets 101 and 102 and the sensor 103 are greatly separated. In addition, since the position detection apparatus 100 has the above-described configuration, the position detection apparatus 100 is very robust, small, and inexpensive.
[0010]
[Problems to be solved by the invention]
By the way, as described above, the position detection device 100 is used in various measurement devices and control devices for automobiles, machine tool robots, and the like.
[0011]
However, a magnetic field generated from a magnetic field generation source other than the magnets 101 and 102 (hereinafter referred to as a disturbance magnetic field) is present at a place where various measurement devices, control devices, machine tool robots, and the like of automobiles are used. . For example, in a field where a machine tool robot is used, a leakage magnetic field from a motor or the like exists. In an automobile, an alternator, an electromagnetic clutch, or the like generates a magnetic field.
[0012]
The position detection device 100 uses a magnetic field. Therefore, when the position detection device 100 is used in a place where a disturbance magnetic field is generated, the sensor 103 senses the disturbance magnetic field together with the magnetic fields from the magnets 101 and 102. That is, the disturbance magnetic field affects the magnetic field that the sensor 103 senses. When a disturbance magnetic field affects the magnetic field that the sensor 103 senses, the position detection device 100 erroneously detects the relative position between the sensor 103 and the magnets 101 and 102. For example, when the position detection device 100 is used in an opening detection device for a vaporizer mounted on an automobile or the like, the opening of the vaporizer is erroneously detected.
[0013]
The present invention has been proposed in view of such a conventional situation, and it is possible to reduce the influence of a disturbance magnetic field, and position detection with little error when used in a place where the disturbance magnetic field exists. An object is to provide an apparatus.
[0014]
[Means for Solving the Problems]
  A position detection apparatus according to the present invention includes a magnetic field detection means having a magnetic sensing means for strongly sensing a uniaxial magnetic field,First magnetic shielding means for covering the magnetic sensing means so that the end in the uniaxial direction is exposed;A magnetic field generating means for applying a magnetic field whose position changes relative to the magnetic sensitive means and whose intensity continuously changes in accordance with the change in the relative position to the magnetic sensitive means;A magnetic field generated from at least the magnetic sensing means or another magnetic field generation source existing outside the movement range in the movement direction of the magnetic field generation means. With magnetic shielding meansIt is characterized by that.
[0021]
In the position detection apparatus according to the present invention, at least the magnetosensitive means out of the magnetic field existing outside the moving range in the moving direction of the magnetic detecting means or the magnetic field generating means by the second magnetic shielding means. A uniaxial magnetic field that is particularly sensitive to magnetism is shielded.
[0022]
Therefore, the position detection device according to the present invention is less affected by the magnetic field existing outside the movement range in the moving direction of the magnetic detection means or the magnetic field generation means with respect to the magnetic field sensed by the magnetic sensing means. Become. In other words, the position detection device according to the present invention is less affected by the disturbance magnetic field with respect to the magnetic field sensed by the magnetic sensing means.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a position detection apparatus to which the present invention is applied will be described in detail with reference to the drawings.
[0024]
As shown in FIGS. 1 and 2, the position detection device 1 to which the present invention is applied includes a sensor 2, magnets 3 and 4, a detection circuit 5, a first shield 6, and a second shield 7. Prepare. In FIG. 1, the detection circuit 5 is not shown. The magnets 3 and 4 are attached so as to move relative to the sensor 2. The detection circuit 5 is connected to the sensor 2.
[0025]
For example, the position detection device 1 is attached to a vaporizer or the like as described later, and is used to detect the opening degree of the vaporizer. In the present embodiment, the position detection device 1 is configured such that the magnets 3 and 4 move relative to the sensor 2. The position detection device 1 detects the opening of the carburetor by detecting the amount of movement of the magnets 3 and 4 relative to the sensor 2.
[0026]
The sensor 2 is a magnetic sensing means, which senses the magnetic field from the magnets 3 and 4 and outputs it as an electrical signal. The sensor 2 is particularly strongly sensitive to a uniaxial magnetic field. Hereinafter, this uniaxial direction is referred to as a magnetic sensitive direction of the sensor 2.
[0027]
As shown in FIG. 3, the sensor 2 includes a rectangular annular core 10 that forms a closed magnetic circuit, and two coils 11 and 12 that are wound around the core 10. The coils 11 and 12 are wound around, for example, two opposite sides of the core 10 in the longitudinal direction. In the sensor 2, the direction in which the coils 11 and 12 are wound is a magnetic sensitive direction. In the present embodiment, the longitudinal direction of the sensor 2 indicated by the arrow A in FIG.
[0028]
The core 10 is made of a magnetic material having conductivity. The core 10 is preferably made of a high magnetic permeability material containing, for example, an amorphous metal containing permalloy, Fe, Co, Si, B, or the like. If a high permeability material is used for the core 10, the sensor 2 becomes highly sensitive due to its saturation characteristics. In the present embodiment, the core 10 is formed by performing heat treatment after etching permalloy into a square ring shape. In the present embodiment, as shown in FIG. 3, the core 10 has an outer dimension of 5.0 mm × 2.0 mm and an inner diameter of 2.0 mm × 1.0 mm.
[0029]
The coils 11 and 12 are made of a conductive material. The coils 11 and 12 are formed by, for example, winding a Cu wire 50 times around two opposite sides of the core 10 in the longitudinal direction. In the present embodiment, a Cu wire is wound around the core 10 so that the coils 11 and 12 form opposite spirals.
[0030]
The sensor 2 is excited when, for example, a high-frequency pulse current flows through the coils 11 and 12. When the sensor 2 senses a magnetic field in the magnetic sensing direction, the impedance change of the coils 11 and 12 becomes large.
[0031]
The sensor 2 is efficient because the magnetic flux generated by being excited by the coils 11 and 12 circulates in the core 10 by energizing the coils 11 and 12 so as to be in reverse phase with the core 10 having a rectangular ring shape. Good excitation is performed, and the sensitivity of the magnetic field from the magnets 3 and 4 is good. In addition, the sensor 2 takes a differential output from the two coils 11 and 12, thereby reducing noise and improving signal output.
[0032]
When the position detection device 1 is attached to a vaporizer or the like as will be described later, the magnetic sensing direction of the sensor 2 is a magnetic field generated from a magnetic field generation source other than the magnets 3 and 4 (hereinafter referred to as a disturbance magnetic field). It attaches so that it may become a substantially orthogonal direction. Therefore, in the position detection device 1, the influence of the disturbance magnetic field on the magnetic field sensed by the sensor 2 is reduced.
[0033]
The core 10 may have the shape shown in FIG. 4 according to the specifications of the sensor 2 and the cost at the time of production. In FIG. 4, two substantially rectangular cores 14 and 15 made of a high permeability material are connected to each other by a substantially rectangular nonmagnetic material 16 at each end, and coils 17 and 18 are respectively connected to the cores 14 and 15. 1 shows an open magnetic path type sensor 19 around which is wound.
[0034]
The magnets 3 and 4 are magnetic field generating means, and give the sensor 2 a magnetic field whose strength and direction change linearly as the relative position increases. At this time, the magnets 3 and 4 are arranged so as to generate a magnetic field in a direction parallel to the magnetic sensing direction of the sensor 2. Moreover, the magnets 3 and 4 are arrange | positioned so that the magnetization direction may be opposite. By arranging the magnets 3 and 4 so that the magnetization directions are opposite to each other, the magnetic field that the sensor 2 senses according to the relative position between the sensor 2 and the magnets 3 and 4 is not only the strength but also the direction. Change. Therefore, the position detection device 1 can accurately detect the relative position between the sensor 2 and the magnets 3 and 4. Further, the magnets 3 and 4 are arranged to move with respect to the sensor 2. The magnets 3 and 4 are disposed so as to move in a direction perpendicular to the respective magnetization directions.
[0035]
As the magnets 3 and 4, a permanent magnet made of barium ferrite, plastic, rubber, or the like, a permanent magnet made by sintering SmCo, an electromagnet, or the like can be used. When electromagnets are used for the magnets 3 and 4, the magnetic field variations as seen in the permanent magnets can be eliminated.
[0036]
As shown in FIG. 5, the detection circuit 5 includes an oscillation circuit 20 for driving the sensor 2, a bridge circuit 21 for detecting an electric signal from the sensor 2, and a differential circuit 22 for taking a differential output of the bridge circuit 21. Composed. Here, the oscillating circuit 20 is an oscillating means for exciting the coils 11 and 12 at a high frequency, and the bridge circuit 21 and the differential circuit 22 detect the impedance of the coils 11 and 12, and based on this impedance, the sensor 2 and the magnet Relative position detecting means for detecting a relative position with respect to 3 and 4. The detection circuit 5 supplies the detected signal to, for example, various measurement devices and control devices of an automobile.
[0037]
The first shield 6 is a first disturbance magnetic field shielding means. The first shield 6 covers the sensor 2 so that the end in the magnetic sensitive direction is exposed. In the present embodiment, the first shield 6 covers substantially the entire sensor 2 in the longitudinal direction.
[0038]
Therefore, by providing the first shield 6, the influence of a magnetic field other than the magnetic sensing direction on the magnetic field that the sensor 2 senses is reduced. Further, by providing the first shield 6, the sensor 2 is sensitive even when the magnetic sensing direction of the sensor 2 and the direction of the disturbance magnetic field are not substantially perpendicular due to, for example, an attachment error of the position detection device 1. The influence of the disturbance magnetic field on the magnetic field is reduced.
[0039]
The second shield 7 is a second disturbance magnetic field shielding means that shields a magnetic field existing outside the moving range of the moving direction of the magnets 3 and 4, and in particular, the same direction as the magnetic sensitive direction of the sensor 2. The disturbance magnetic field is shielded. In the present embodiment, the shape of the second shield 7 is such that the length in the moving direction of the magnets 3 and 4 is substantially the same as the moving range of the magnets 3 and 4, and the magnetic field generated from the magnets 3 and 4 The length in the same direction is substantially equal to the length of the sensor 2 in the magnetic sensing direction.
[0040]
Therefore, by providing the second shield 7, the influence of the disturbance magnetic field existing outside the moving range in the moving direction of the magnets 3 and 4 is reduced with respect to the magnetic field that the sensor 2 senses. Further, even when the magnetic sensing direction of the sensor 2 and the direction of the disturbance magnetic field are deviated from the substantially vertical direction due to, for example, an attachment error of the position detection device 1, the influence of the disturbance magnetic field can be reduced.
[0041]
The first shield 6 and the second shield 7 (hereinafter collectively referred to as a shield) are preferably made of a pure iron-based material having a high saturation magnetic flux density and a small residual magnetism. When the applied magnetic field is sufficiently small with respect to the saturation magnetic properties of the material forming the shield, the influence of hysteresis can be ignored, so there is no need to pay particular attention to the material. For example, when a weak magnetic field is detected by separating the sensor 2 and the magnets 3 and 4 apart from each other, it is preferable that the shield be made of permalloy or the like that is less affected by hysteresis.
[0042]
By the way, in this position detection device 1, the strength of the magnetic field from the magnets 3 and 4 sensed by the sensor 2 is detected using the eddy current generated in the core 10, and the relative relationship between the magnets 3 and 4 and the sensor 2 is detected. The position is detected. The eddy current is a current generated so as to circulate in the conductor when the conductor is placed in a changing magnetic field.
[0043]
Below, the method to detect the relative position of the magnets 3 and 4 and the sensor 2 using the eddy current which generate | occur | produces in the core 10 is demonstrated.
[0044]
First, the coils 11 and 12 are driven by high frequency excitation by the oscillation circuit 20 so that the magnetic flux in the core 10 is not saturated.
[0045]
When the coils 11 and 12 are driven at a high frequency, since the core 10 itself has conductivity, an eddy current is generated in the core 10, and the impedance of the coils 11 and 12 has a 90 ° phase with respect to the drive wave. In addition to the impedance loss component due to the shifted self-induction, the impedance loss component due to the eddy current that is 180 ° out of phase with the driving wave is generated. Both of these components change their values according to the change in the magnetic permeability μ of the sensor core material. In particular, by exciting the core 10 so as not to saturate, the eddy current loss greatly contributes to the impedance of the coils 11 and 12. It becomes like this. The impedance obtained by combining these two components shows a very large change with respect to the change in the relative position between the magnets 3 and 4 and the sensor 2.
[0046]
The reason why the impedance loss due to the eddy current changes according to the magnitude of the magnetic field is that the eddy current actually varies depending on the magnetic permeability μ of the sensor core. In general, in the case of a magnetic material, the magnetic permeability μ is not simply expressed as a constant, but changes according to the magnitude of the magnetic field.
[0047]
In the present embodiment, as the sensor 2, a core 10 that is conductive and magnetic is formed by winding the coils 11 and 12, and an eddy current generated in the core 10 is used. Although the magnetic fields from the magnets 3 and 4 are detected, the sensor 2 may be any sensor that strongly senses the magnetic field in the uniaxial direction. For example, an MR element or a Hall element can be used as the sensor 2.
[0048]
In the present embodiment, the position detection device 1 is configured such that the magnets 3 and 4 move relative to the sensor 2. Therefore, the length of the second shield 7 in the moving direction of the magnets 3 and 4 is substantially equal to the moving range of the magnets 3 and 4. However, the position detection device to which the present invention is applied may be configured such that the sensor moves relative to the magnet. In the position detection device, the length of the second shield in the movement direction of the sensor needs to be approximately equal to the movement range of the sensor.
[0049]
Next, a vaporizer equipped with the position detection device 1 will be described in detail with reference to FIGS.
[0050]
Here, FIG. 6 shows a side view of the vaporizer 31 to which the position detection device 1 is mounted, and FIG. 7 shows a cross-sectional view of the vaporizer 31 taken along line X-X ′ in FIG. 7.
[0051]
The vaporizer 31 includes a so-called direct acting valve, and includes a main body 32 and a chamber 33 into which liquid fuel is injected. The chamber 33 is connected to a fuel introduction passage 44 formed in the main body 32, and liquid fuel is injected.
[0052]
The main body 32 includes a cab body 34, a direct acting piston valve 35, a lid 36, and a spring 37. The piston valve 35 is inserted into a valve chamber 42 formed in the cab body 34, and opens and closes a venturi passage 41 formed in the cab body 34. The lid 36 is attached to the upper opening of the cab body 34 so as to close the valve chamber 42. The spring 37 is provided between the lid 36 and the piston valve 35 and biases the piston valve 35.
[0053]
The cab body 34 is made of, for example, zinc die cast, and has a venturi passage 41 through which intake air flows in the direction of arrow C shown in FIG. The cab body 34 is provided with a cylinder portion 43. The cylinder portion 43 is formed with a valve chamber 42 that opens into the venturi passage 41. Further, a fuel introduction passage 44 is formed in the cab body 34. The fuel introduction passage 44 extends vertically downward from the venturi passage 41 so as to be coaxial with the cylinder portion 43, and a jet needle 46 provided in the piston valve 35 is inserted therein. Further, the cab body 34 is provided with a fuel introduction portion 45 that is integrated with the fuel introduction passage 44 and extends into the chamber 33.
[0054]
A substantially oval and bottomed cylindrical piston valve 35 is inserted into the valve chamber 42 formed in the cylinder portion 43 in a direction perpendicular to the direction of the intake air flowing through the venturi passage 41. The piston valve 35 is slidable with respect to the cylinder portion 43, and is held by the cylinder portion 43 so that the moving axis of the vertical movement does not shift. The piston valve 35 adjusts the amount of intake air flowing through the venturi passage 41 by moving up and down in the valve chamber 42.
[0055]
A bottomed cylindrical lid 36 having a shape corresponding to the cylinder portion 43 is attached to the upper end opening of the cylinder portion 43 to close the valve chamber 42 formed in the cylinder portion 43. A spring 37 is provided between the lid 36 and the piston valve 35. The spring 37 urges the piston valve 35 in a direction to close the venturi passage 41.
[0056]
In addition, an engagement portion 43a that restricts movement of the piston valve 35 in the closing direction is formed at the upper end opening of the cylinder portion 43, and the upper end of the piston valve 35 corresponds to the engagement portion 43a. A collar portion 35a is formed in the opening. When the piston valve 35 is urged by the spring 37 in a direction to close the venturi passage 41, the collar portion 35a and the engaging portion 43a are engaged. Therefore, the piston valve 35 is maintained in a state in which the venturi passage 41 is closed most when no force is applied in the direction of releasing the venturi passage 41. The opening of the piston valve 35 at this position is referred to as an idling opening.
[0057]
A jet needle 46 is provided outside the bottom surface of the piston valve 35. The jet needle 46 is inserted into a fuel introduction passage 44 formed vertically downward with respect to the venturi passage 41, and moves in the vertical direction along with the piston valve 35. Such a jet needle 46 adjusts the amount of fuel sucked into the venturi passage 41 from the chamber 33.
[0058]
When the carburetor 31 is applied to, for example, a motorcycle, one end of a slot cable (not shown) of the piston valve 35 is stopped, and an extended end of the slot cable is connected to an accelerator grip. Then, by operating the accelerator grip, the piston valve 35 moves in the vertical direction to change the passage area of the venturi passage 41 from fully closed to fully open, and the amount of fuel sucked into the venturi passage 41 Adjust. Thus, in the carburetor 31, the fuel can be mixed with the intake air and supplied to the engine, and the rotational speed of the engine can be changed.
[0059]
In the carburetor 31, the venturi passage 41 is not completely closed even when the piston valve 35 reaches the idling opening degree. Therefore, a predetermined amount of fuel is sucked into the venturi passage 41 from the chamber 33. Has been. Therefore, in the carburetor 1, the intake air mixed with a predetermined amount of fuel can be supplied to the engine while the piston valve 35 is at the idling opening degree.
[0060]
The carburetor 31 having the above-described configuration is equipped with the position detection device 1 to which the present invention is applied as an opening detection device for detecting the opening of the piston valve 35.
[0061]
More specifically, the magnets 3 and 4 are provided on the piston valve 35, and the sensor 2, the detection circuit 5, the first shield 6, and the second shield 7 are provided on the cylinder portion 43.
[0062]
In addition, the position detection device 1 is attached to the vaporizer 31 so that the magnetic sensing direction of the sensor 2 and the direction of the disturbance magnetic field generated from the alternator 50 are substantially perpendicular.
[0063]
The magnets 3 and 4 are embedded in the side surface of the piston valve 35 with a predetermined interval, and are bonded by an epoxy resin or the like. At this time, the magnets 3 and 4 are embedded in the piston valve 35 so that the straight line connecting the magnets 3 and 4 coincides with the moving direction of the piston valve 35. For example, one magnet 3 is provided at a position closest to the bottom surface 42a of the valve chamber 42, and the other magnet 4 is provided approximately in the middle between the collar portion 35a and the bottom surface 35b. The magnets 3 and 4 are embedded in the piston valve 35 so that the magnetization direction is substantially perpendicular to the moving direction of the piston valve 35 and the magnetization directions are opposite to each other. One magnet 3 is provided so that the generated magnetic field is in the direction indicated by arrow D in FIG. 6, that is, the same direction as the direction in which intake air flows into the venturi circuit 41, and the other magnet 4 is generated. 6 is provided so as to be in the direction indicated by the arrow E in FIG. 6, that is, the direction opposite to the direction in which the intake air flows into the venturi circuit 41.
[0064]
The sensor 2 covered with the first shield 6 is provided on the outer surface of the cylinder portion 43 so that the magnetic sensing direction is substantially the same as the magnetization direction of the magnets 3 and 4. Further, the detection circuit 5 and the second shield 7 are also provided on the outer surface of the cylinder portion 43 in the same manner as the sensor 2. At this time, the length of the second shield 7 in the longitudinal direction of the vaporizer 31 is substantially equal to the length of the moving direction of the magnets 3 and 4, and the magnetization direction of the magnetic field generated from the magnets 3 and 4 is The length in the same direction is substantially equal to the length of the sensor 2 in the magnetic sensing direction.
[0065]
By mounting each member of the position detection device 1 at the position described above, the opening degree of the piston valve 35 in the carburetor 31 can be detected.
[0066]
In the vaporizer 31, as the piston valve 35 opens, the positions of the magnets 3 and 4 with respect to the sensor 2 move. Accordingly, the strength and direction of the magnetic field that the sensor 2 senses changes continuously.
[0067]
More specifically, when the opening degree of the piston valve 35 is the idling opening degree, the sensor 2 is strongly sensitive to the magnetic field generated from one magnet 4, and the magnetic field generated from the other magnet 3 is almost the same. Not magnetized. As the piston valve 35 is opened, the sensor 2 gradually becomes less sensitive to the magnetic field generated from one magnet 4, and gradually becomes more sensitive to the magnetic field generated from the other magnet 3. When the piston valve 35 is fully opened, the sensor 2 hardly senses the magnetic field generated from the one magnet 4 and strongly senses the magnetic field generated from the other magnet 3.
[0068]
That is, as the piston valve 35 is opened, the direction and intensity of the magnetic field that the sensor 2 senses changes as described below. First, when the opening degree of the piston valve 35 is the idling opening degree, the sensor 2 strongly senses the magnetic field in the arrow D direction. Next, as the piston valve 35 is opened, the sensor 2 becomes less sensitive to the magnetic field in the direction of arrow D. When the sensor 2 reaches the same position from the two magnets 3 and 4, the magnetic field that the sensor 2 senses becomes zero. Next, the sensor 2 senses a magnetic field in the direction of arrow E. Further, as the piston valve 35 opens, the sensor 2 becomes more sensitive to the magnetic field in the direction of arrow E. Finally, when the piston valve 35 is fully opened, the sensor 2 most strongly senses the magnetic field in the direction of arrow E.
[0069]
As described above, the strength and direction of the magnetic field sensed by the sensor 2 changes as the piston valve 35 opens. Therefore, the position detection device 1 to which the present invention is applied can detect the relative position between the sensor 2 and the magnets 3 and 4 by detecting the strength and direction of the magnetic field that the sensor 2 senses. The opening degree of the valve 35 can be detected.
[0070]
Further, the position detection apparatus 1 to which the present invention is applied is configured such that the direction of the magnetic field of the sensor 2 is substantially perpendicular to the direction of the disturbance magnetic field, or the first shield 6 and the second shield 7. Is disposed, the relationship between the relative position of the sensor 2 and the magnets 3 and 4 and the magnetic field to which the sensor 2 is sensitive changes linearly. Therefore, the position detection device 1 to which the present invention is applied can accurately detect the relative position between the sensor 2 and the magnets 3 and 4, and when used as an opening detection device for the vaporizer 31, The opening degree of the vaporizer 31 can be detected with high accuracy.
[0071]
Below, based on an experimental example, the relationship between the relative position of the sensor 2 and the magnets 3 and 4 in the position detection apparatus 1 and the strength and direction of the magnetic field that the sensor 2 senses will be described.
[0072]
Experimental example 1
Each member of the position detection device 1 was attached to the vaporizer 30 so that the magnetic sensing direction of the sensor 2 and the direction of the disturbance magnetic field were substantially perpendicular.
[0073]
That is, the two magnets 3 and 4 were embedded in the side surface of the piston valve 35 at a predetermined interval and bonded with an epoxy resin. At this time, the magnets 3 and 4 were embedded in the piston valve 35 so that the straight line connecting the magnets 3 and 4 coincided with the moving direction of the piston valve 35. One magnet 3 is provided at a position closest to the bottom surface 42a of the valve chamber 42, and the other magnet 4 is provided approximately in the middle between the collar portion 35a and the bottom surface 35b. Further, the magnets 3 and 4 are provided so that the magnetization direction is substantially perpendicular to the moving direction of the piston valve 35 and is opposite thereto.
[0074]
Further, the sensor 2, the detection circuit 5, the first shield 6, and the second shield 7 are provided on the outer surface of the cylinder portion 43. The sensor 2 was covered with the first shield 6 in the longitudinal direction so that the end in the magnetic sensing direction was exposed. And this sensor 2 was provided in the outer surface of the cylinder part 43 so that a magnetic sensing direction might become substantially the same as the magnetization direction of each magnet 3 and 4. FIG. The length of the second shield 7 in the longitudinal direction of the vaporizer 31 is substantially equal to the length of the moving direction of the magnets 3 and 4, and the length in the same direction as the magnetization direction of the magnetic field generated from the magnets 3 and 4. The length of the sensor 2 is approximately equal to the length of the sensor 2 in the magnetic sensing direction.
[0075]
The sensor 2 has a structure in which the coils 11 and 12 are wound so as to form opposite spirals on two opposite sides of the rectangular annular core 10 in the longitudinal direction.
[0076]
The coils 11 and 12 were driven at a high frequency so that the magnetic flux in the core 10 was not saturated, and the output from the sensor 2 that changed according to the eddy current generated in the core 10 was measured. And the relationship between the relative position of the sensor 2 and the magnets 3 and 4 and the electrical signal output from the sensor 2 was investigated.
[0077]
Experimental example 2
Except that the second shield 7 was not attached, each member of the position detection device 1 was attached to the vaporizer 31 as in Experimental Example 1, and the relative position of the sensor 2 and the magnets 3 and 4 and the output from the sensor 2 were output. The relationship with the electrical signal is investigated.
[0078]
Experimental example 3
Except that the first shield 6 was not attached, each member of the position detection device 1 was attached to the vaporizer 31 as in Experimental Example 2, and the relative positions of the sensor 2 and the magnets 3 and 4 and the output from the sensor 2 were output. The relationship with the electrical signal is investigated.
[0079]
Experimental Example 4
Each member of the position detection device 1 is mounted in the same manner as in Example 3 except that the members of the position detection device 1 are attached so that the magnetic sensing direction of the sensor 2 and the direction of the disturbance magnetic field are not substantially perpendicular. It attached to the vaporizer | carburetor 31, and investigated the relationship between the relative position of the sensor 2 and the magnets 3 and 4, and the electrical signal output from the sensor 2. FIG.
[0080]
The results of Experimental Examples 1 to 4 are shown in FIG.
[0081]
From FIG. 8, in Experimental Example 4 in which the magnetic sensing direction of the sensor 2 and the direction of the disturbance magnetic field are not substantially perpendicular, the electric signal output from the sensor 2 gradually depends on the relative position of the sensor 2 and the magnets 3 and 4. Variations in what was changing were seen. That is, the electric signal output from the sensor 2 according to the relative position of the sensor 2 and the magnets 3 and 4 did not change linearly.
[0082]
On the other hand, in Experimental Example 3 in which the magnetic sensing direction of the sensor 2 and the direction of the disturbance magnetic field are substantially perpendicular, the electric signal output from the sensor 2 according to the relative position of the sensor 2 and the magnets 3 and 4 is a straight line. Changed.
[0083]
Further, in the experimental example 2 provided with the first shield 6, the sensor 2 and the magnets 3, 4 are controlled according to the relative positions of the sensor 2 and the magnets 3, 4 at the same time. The output electrical signal changed more linearly as compared with Experimental Example 3.
[0084]
Further, in the experimental example 1 including the first shield 6 and the second shield 7 at the same time as making the magnetic sensing direction of the sensor 2 and the direction of the disturbance magnetic field substantially vertical, the relative position of the sensor 2 and the magnets 3, 4. As a result, the electric signal output from the sensor 2 changed more linearly than in the experimental example 2.
[0085]
【The invention's effect】
The position detection device according to the present invention has a disturbance magnetic field with respect to a magnetic field that the magnetic sensing means senses by making the uniaxial direction of the magnetic sensing means that strongly senses a magnetic field in the uniaxial direction and the direction of the disturbance magnetic field substantially perpendicular to each other. Less influence.
[0086]
In addition, the position detection apparatus according to the present invention includes first magnetic shielding means that covers a magnetic sensing means that strongly senses a uniaxial magnetic field. The first magnetic shielding means covers the magnetic sensing means so that the end in the uniaxial direction is exposed. Therefore, the position detecting device includes the first magnetic shielding unit, so that the magnetic field other than the uniaxial direction is less affected by the magnetic field sensed by the magnetic sensing unit.
[0087]
Moreover, the position detection apparatus according to the present invention includes the second magnetic shielding means. This second magnetic shielding means is a uniaxial magnetic field in which at least the magnetic sensing means is particularly strong in the magnetic field among the magnetic fields existing outside the moving range of the magnetic sensing means or the magnetic field generating means. Shielding. Therefore, the position detection device includes the second magnetic shielding unit, so that the magnetic field disturbed by the magnetic sensing unit is a disturbance magnetic field that exists outside the moving range in the moving direction of the magnetic sensing unit or the magnetic field generation unit. Of these, at least a uniaxial disturbance magnetic field is less affected.
[0088]
For the reasons described above, the position detection device according to the present invention is less affected by the disturbance magnetic field with respect to the magnetic field sensed by the magnetic sensing means. The change in the output electrical signal is linear. Therefore, the position detection device according to the present invention can accurately detect the relative positions of the magnetic field generating means and the magnetic sensing means.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a position detection device to which the present invention is applied.
FIG. 2 is a plan view showing the position detection device.
FIG. 3 is a plan view showing a sensor provided in the position detection device.
FIG. 4 is a plan view showing an example of another sensor provided in the position detection device.
FIG. 5 is a circuit diagram of a detection circuit provided in a position detection device to which the present invention is applied.
FIG. 6 is a side view of a vaporizer equipped with a position detection device to which the present invention is applied.
FIG. 7 is a sectional view of the vaporizer.
FIG. 8 is a diagram illustrating a relationship between a positional relationship between a sensor and a magnetic field generation unit and a signal output of the sensor in a position detection device to which the present invention is applied and a conventional position detection device.
FIG. 9 is a schematic diagram showing a conventional position detection device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Position detection apparatus, 2 Sensor, 3, 4 Magnet, 5 Detection circuit, 6 1st shield, 7 2nd shield, 10 core, 11, 12 coil

Claims (3)

A magnetic field detecting means having a magnetic sensing means for strongly sensing a uniaxial magnetic field;
First magnetic shielding means for covering the magnetic sensing means so that the end in the uniaxial direction is exposed;
Magnetic field generation in which a position changes relative to the magnetic sensing means, and a magnetic field whose strength and / or direction continuously changes in accordance with the change in the relative position is applied to the magnetic sensing means. Means and
Second magnetic shielding means for shielding the uniaxial magnetic field among magnetic fields generated from at least the magnetic sensing means or another magnetic field generation source existing outside the moving range in the moving direction of the magnetic field generating means. A position detection device comprising: The first magnetic shielding means, the position detecting device according to claim 1, wherein the length of the axial direction is substantially equal to the length of the axial direction of the magnetism-sensitive means. The magnetic field detection means includes
A magnetic sensing means comprising a core made of a high magnetic permeability material and a coil driven by high frequency excitation;
Oscillating means for high frequency excitation driving of the coil;
Detecting the impedance of the coil, the position detecting according to claim 1, further comprising a relative position detecting means for detecting the relative position between the magnetism-sensitive means and said magnetic field generating means on the basis of the impedance apparatus.

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