Rotation sensor accommodable to an eccentricity of a rotation portion of a member to be detected relative to a rotating shaft of the sensor

There is provided a highly reliable rotation sensor which is capable of accurate detection of a rotation state. The rotation sensor comprises: a rotor rotating together with a rotation portion of a detection side; a first supporting member for rotatably supporting the rotor; and a detecting member secured to the first supporting member for detecting a rotation state of the rotor. The first supporting member is supported movably in both directions, that is, an X direction orthogonal to the direction of the rotating shaft of the rotor and a Y direction which is orthogonal to the direction of the rotating shaft of the rotor and orthogonal to the X direction.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a rotation sensor such as a throttle
 position sensor, attached to a throttle valve, for detecting an opening
 level of the valve, and more particularly to a rotation sensor
 accommodable to the eccentricity of a rotation portion of the valve
 relative to the rotating shaft of the sensor.
 2. Description of the Related Art
 FIG. 23 is a schematic diagram showing a conventional rotation sensor as
 described above. As shown in the figure, a shaft 52 is coupled to a rotor
 51 of a detection side, the shaft 52 is rotatably supported at a location
 of a bearing 53, and a magnetized code plate 54 that is integrally
 connected to the tip of the shaft 52. In the vicinity of the circumference
 of the code plate 54 that is disposed a magnetism detecting element 55,
 which is supported by a casing (not shown).
 By way of example, the conventional rotation sensor, which has a so-called
 one-point support configuration in which the shaft 52 is supported at one
 point, has the shaft 52 supported by the bearing 53 with some backlash so
 that it is freely rotatable. If the rotor 51 is attached to the shaft 52
 with their center axes in misalignment or if in its place the rotor 51
 itself rotates eccentrically, then the code plate 54 will rotate
 eccentrically, and a gap G between the code plate and the magnetism
 detecting element 55 will change greatly. As a consequence, a linear
 output will not be obtained in a magnetic variable resistor. This has been
 a disadvantage of conventional rotation sensors.
 If the shaft 52 is supported at two points to solve this disadvantage,
 although a relative positional relationship between the code plate 54 and
 the magnetism detecting element 55 can be maintained to a degree of the
 clearance between the shaft 52 and the bearing 53, without enhancing the
 accuracy of mounting dimensions, detailed detection of rotation states
 would become impossible because of actuating force decreased due to center
 misalignment. Another disadvantage is that the eccentricity of the shaft
 52 causes wear on the two-point support portions, reducing the operating
 life of the sensor.
 SUMMARY OF THE INVENTION
 An object of the present invention is to solve these disadvantages of the
 related art and provide a highly reliable rotation sensor capable of
 correctly detecting rotation states.
 To achieve the above described object, the present invention provides a
 rotation sensor comprising:
 a rotor having a magnetized portion on, e.g., a circumferential side,
 rotating together with a rotation portion of a detection side such as,
 e.g., a throttle valve;
 a first supporting member for rotatably supporting the rotor; and
 a detecting member, secured to the first supporting member, and having a
 hole IC for detecting a rotation state of the rotor,
 wherein the first supporting member is supported movably in both
 directions, that is, an X direction which is orthogonal to the direction
 of the rotating shaft of the rotor and a Y direction which is orthogonal
 to the direction of the rotating shaft of the rotor and orthogonal to the
 X direction.
 According to the present invention, as previously described, since both the
 rotor and the detecting member for detecting a rotation state thereof are
 supported by the first supporting member and the rotor and the detecting
 member are movable together in the X and Y directions, even if the
 rotation portion becomes eccentric, the rotor and the detecting member
 together can follow the eccentricity and the spacing between the rotor and
 the detecting member is always constant, and therefore there is no output
 variation due to the eccentricity of the rotation portion.
 Since this construction eliminates the need to support the shaft at two
 points, there can be provided a rotation sensor which is free of decrease
 in actuating force, capable of correct detection of a rotation state, and
 highly reliable.
 A rotation sensor of the present invention may comprise:
 a second supporting member for supporting the first supporting member; and
 a third supporting member for supporting the second supporting member,
 wherein the first supporting member is supported movably to the Y direction
 by the second supporting member, and
 the second supporting member is supported movably to the X direction by the
 third supporting member.
 According to the present invention, if both the first supporting member and
 the third supporting member are constructed from a synthetic resin and the
 second supporting member is constructed from metal, friction resistance is
 reduced and the rotation sensor moves smoothly in the X and Y directions,
 so that it can detect a rotation state more correctly.
 According to the present invention, Y-direction guide means which permits
 the travel of the first supporting member in the Y direction and prevents
 the travel thereof in the X direction is provided in the second supporting
 member, and X-direction guide means which permits the travel of the second
 supporting member in the X direction and prevents the travel thereof in
 the Y direction is provided in the third supporting member, whereby the
 travel in the X and Y directions is distinctly divided so that the
 rotation sensor can respond appropriately to the eccentricity of a
 rotation portion.
 According to the present invention, since the third supporting member is
 formed with an exterior member of the sensor in a fixed state, the third
 supporting member need not be provided additionally, so that parts can be
 reduced in quantity, size, and weight.
 According to the present invention, a terminal is provided in the third
 supporting member, and the terminal and the detecting member are connected
 by a flexible connecting wire, whereby the first supporting member moves
 without trouble and a rotation state can be correctly detected.
 According to the present invention, a concave housing part is formed in the
 first supporting member and the detecting member is inserted and secured
 within the housing member, and thereby the detecting member is disposed
 close to the rotor, so that correct detection of a rotation state can be
 made and the detecting member does not project substantially from the
 first supporting member, providing no obstacle for the travel of the first
 supporting member.
 According to the present invention, if the first supporting member is of
 shape of almost rectangular frame and is disposed in sliding on the second
 supporting member, the first supporting member moves stably.
 According to the present invention, since the rotor has a magnetized
 portion on the circumferential side and the detecting member is a
 magnetism detecting element, the reliability of detection is high and the
 configuration of the detection part is simple and inexpensive.
 According to the present invention, since a rotation part of a detection
 side is a throttle valve, there can be provided a highly reliable throttle
 position sensor capable of correct detection of a rotation state.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Hereinafter, a rotation sensor according to an embodiment of the present
 invention will be described with the accompanying drawings. FIG. 1 is a
 perspective view showing a rough shape of a rotation sensor according to
 the embodiment; FIG. 2 is a front cross-sectional view of the rotation
 sensor; FIG. 3 is a cross-sectional view taken along the line 3--3 of FIG.
 2; and FIG. 4 is a cross-sectional view taken along the line 4--4 of FIG.
 2.
 In these figures, the reference numeral 1 denotes a housing and 2 denotes a
 printed wiring board, which is disposed within the housing 1 and connected
 to plural terminals 3 fitted to the housing 1 as shown in FIGS. 2 and 3.
 The reference numeral 4 denotes an almost cylindrical rotor; 5, a first
 supporting member of almost frame shape; 6, three detecting members each
 consisting of a hole IC, secured to the first supporting member 5; 7, a
 flexible printed wiring board of almost T-character shape, with the three
 detecting members 6 soldered, connected to the printed wiring board 2; 8,
 a second supporting member; and 9, a cover of almost plate shape.
 FIGS. 5, 6, and 7 are a front view, a vertical cross-sectional view, and a
 horizontal cross-sectional view of the housing 1, respectively. As shown
 by these figures, the housing 1, constructed from a synthetic resin which
 is of almost box shape, has a concave housing part 10 formed inside it and
 a through hole 11 provided at a position corresponding to the bottom of
 the concave housing part 10. At the top and bottom of the concave housing
 part 10 are provided guide stage parts 12 which extend in parallel to the
 X direction, and a third supporting member is formed by supporting the
 second supporting member 8 movably in the X direction by the guide stage
 part 12.
 FIGS. 8, 9, and 10 are a front view, a vertical cross-sectional view, and a
 side view of the rotor 4, respectively. FIGS. 11, 12, and 13 are a front
 view, a vertical cross-sectional view, and a side view of a core
 supporting member 13 used for the rotor 4, respectively.
 The rotor 4 comprises a core supporter 13, a core ring 14 supported
 thereby, a magnetic shield ring 15, and a core ring supporting member 16
 for supporting the core ring 14 to the core supporter 13. The core
 supporter 13 is constructed from a synthetic resin which is of almost
 cylindrical shape, and has a non-circular engagement hole 18 formed inside
 it, through which a rotating shaft 17 (e.g., a metallic rotating shaft
 connected to a throttle valve. See FIGS. 1 and 9), a rotor of a detection
 side, is fitted.
 On the cylindrical part 19 of the core supporter 13 are successively fitted
 a magnetic shield ring 15, a core ring 14, and a core ring supporting
 member 16. In this case, a concave part 13a provided in the flange of the
 core supporter 13 and a projected part 14a provided in the core ring 14
 engage with each other to determine the position of a rotation direction.
 An anchoring groove 20 of circular ring shape is formed on the
 circumferential side of the cylindrical part 19, a projection part 16a
 inserted in the anchoring groove 20 is provided on the inner
 circumferential side of the core ring supporting member 16, and the
 engagement of the anchoring groove 20 and the projection part 16a causes
 the core ring 14 to rotate integrally while being supported in a
 sandwiched form between the core supporter 13 and the core ring supporting
 member 16. The core ring 14, which is constructed from, e.g., a plastic
 magnet, although not shown, is magnetized to the N or S pole on the
 circumferential side of the core ring 14 to maintain a proper positional
 relationship with the engagement hole.
 The above described magnetic shield ring 15 is provided to prevent a
 situation in which a rotating shaft constructed from magnetic members such
 as iron exerts an influence on a flux distribution of the core ring 14 and
 output changes depending on the existence of the rotating shaft (because a
 reference value is determined in the state in which no rotating shaft
 exists) and the shape thereof, so that a reference value is not obtained.
 FIG. 14 is a front cross-sectional view of the first supporter 5; FIG. 15,
 a cross-sectional view taken along the line 15--15 of FIG. 14; FIG. 16, a
 cross-sectional view taken along the line 16--16 of FIG. 14; and FIGS. 17
 and 18 are a side view and a bottom view of the first supporter 5,
 respectively.
 The first supporter 5 is constructed from a synthetic resin and has a frame
 part 21 of almost rectangular shape, and has a housing part 22 at the
 center of the front to house most of the rotor 4, as shown in FIG. 14.
 Element securing parts 23 are concavely mounted, and groove parts 23a are
 continuously provided, so as to receive and guide the terminals of the
 detecting members 6. Small holes 24 are formed in positions opposite to
 the housing part 22 of the element securing parts 23. As shown in FIG. 2,
 each detecting member 6 is completely buried in the housing part 22. A
 projection 21a is provided at the bottom of the housing part 22 upon which
 a flexible printed board 7 is fitted, and both are integrated so that no
 stress is applied to the soldering parts of the detecting members 6 as the
 supporter 5 moves.
 The rotor 4 is inserted from the front of the housing part 22 with some
 pressure at a total of four locations, the three element securing parts 23
 and the concave part 5a which contact tightly with the rotor 4 and bend
 evenly. Therefore, the rotor 4 does not go off-center in the X and Y
 directions and is supported without backlash. For the shaft line
 direction, an anchoring claw 25 (see FIGS. 9 or 10) projected in ring
 shape in the core ring supporting member 16 of the rotor 4 contacts
 tightly with a second supporter 8 as shown in FIGS. 3 and 4, and a
 projection 13b convexly provided in ring shape in a core supporter 13
 contacts tightly with a cover 9. Therefore, the rotor is supported without
 backlash so that it can rotate smoothly. As shown in FIG. 2, in this
 support state, each detecting member 6 is disposed in opposed relation to
 and close to a magnetized portion of the core ring 14 via a small hole 24.
 FIG. 19 is a front view of the second supporter 8; FIG. 20, a
 cross-sectional view taken along the line 20--20 of FIG. 19; FIG. 21, a
 cross-sectional view taken along the line 21--21 of FIG. 19; and FIG. 22,
 a side view of the second supporter 8.
 The second supporter 8 is constructed from a synthetic resin, is
 rectangular in front shape, has a through hole 26 formed at the central
 portion thereof, and has guide walls 27 provided in the both sides which
 extend backward. As shown in FIGS. 4, 19, and 21, a first supporter 5 is
 supported with some pressure between the guide walls 27 in both sides. But
 since a side opposite to the base is open, the supporter 8 can bend and
 move vertically without backlash in the X direction, that is, is supported
 movably in the Y direction as shown in FIG. 2.
 L-shaped holes 8a extending between the base forming the through hole 26
 and the guide walls 27 are provided at the four corners, so that the
 supporter 8 can bend slightly in the Y direction and is supported in a
 sandwiched form without backlash between the guide stages 12. Projected
 parts 8b are formed along the X direction on the back of the base, so that
 the supporter 8 can move without backlash in the Y direction and smoothly
 in the X direction.
 As shown in FIG. 1, a through hole 29 is formed at a predetermined position
 of the cover 9. The rotor 4 is supported rotatably by the first supporter
 5 as shown by the dotted arrow in FIG. 1, the first supporter 5 is
 supported movably by the second supporter 8 only in the Y direction
 orthogonal to the rotating shaft direction of the rotor 4, the second
 supporter 8 is supported movably by the housing 1 (a third supporter) only
 in the X direction orthogonal to the rotating shaft direction of the rotor
 4, a snap foot 9a of the cover 9 engages with a projection 1a on the side
 of the housing 1 to support the supporter 8, and the openings of the
 housing 1 are covered with the cover 9.
 In the assembled rotation sensor, as shown in FIG. 4, the core supporter 13
 (cylindrical part 19) is loosely inserted around it in the through hole 11
 of the housing 1, the through hole 26 of the second supporter 8, and the
 through hole 29 of the cover 9, and extends outward from the housing 1 and
 the cover 9.
 The rotating shaft 17 is inserted and engaged in the engagement hole 18 of
 the core supporter 13, and the rotor 4 rotates together with the rotating
 shaft 17, while the first supporter 5 is prevented from rotating by the
 second supporter 8 and the housing 1 (third supporter). A rotation state
 of the rotating shaft 17 is detected and outputted using a magnetic
 variable resistor by plural detecting members (hole ICs) via the rotor 4
 (core ring 14).
 Although the first supporter can also be cylindrical in shape, if the shape
 of the first supporter is rectangular as in the above described
 embodiment, since the first supporter contacts with the second supporter
 in four locations, a high dimensional accuracy is obtained, so that the
 first supporter can be supported stably without backlash.
 Although the housing is used also as the third supporter in the above
 described embodiment, the present invention is not limited to the above
 embodiment. For example, an exterior member of the sensor in another fixed
 state such as the cover can also be used as a third supporter.
 In the above described embodiment, the rotor is provided with a magnetized
 portion and a hole IC is used in the detecting member to magnetically
 detect a rotation state. However, the present invention is not limited to
 the above embodiment. For example, a rotor is provided with a part having
 a high reflectivity and a part having a low reflectivity, and a detecting
 member is provided with a light emitting element and a light receiving
 element, whereby a rotation state can be optically detected.
 In the above described embodiment, a flexible printed wiring board is used
 between a detecting member and a terminal. However, the present invention
 is not limited to the above embodiment. Other flexible connecting wires
 such as coated signal wires may be used as signal wires.
 A rotation sensor according to the present invention is applicable not only
 to throttle position sensors but also to rotation sensors of other uses
 such as encoders. Further, the configuration according to the present
 invention is applicable to variable resistors and contact sensors.
 According to the present invention, as previously described, since both the
 rotor and the detecting member for detecting a rotation state thereof are
 supported by the first supporting member, and the rotor and the detecting
 member are movable together in the X and Y directions, even if the
 rotation portion becomes eccentric, the rotor and the detecting member
 together can follow the eccentricity and the spacing between the rotor and
 the detecting member is always constant, and therefore there is no output
 variation due to the eccentricity of the rotation portion.
 Since this construction eliminates the need to support the shaft at two
 points, there can be provided a rotation sensor which is free of decrease
 in actuating force, capable of correct detection of a rotation state, and
 highly reliable.