Rotation sensor

Abstract: A highly reliable rotation sensor is capable of correct detection of a rotation state even in case of eccentricity of a rotating shaft. The rotation sensor comprises: a rotor (4) rotating together with a rotating shaft; a first supporting member (5) for rotatably supporting the rotor (4); and a detecting member (6), secured to the first supporting member (5), for detecting a rotation state of the rotor (4), wherein the first supporting member (5) is supported movably with respect to a fixed external part such as a housing in both directions, that is, an X direction orthogonal to the direction of the rotating shaft of the rotor (4) and a Y direction which is orthogonal to the direction of the rotating shaft of the rotor (4) and orthogonal to the X direction. The first supporting member may be linearly slidingly movable on a second supporting member, which is linearly slidingly movable on a fixed housing member.

Description: 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. 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 is integrally at the tip of the shaft 52. In the vicinity of the circumference of the code plate 54 is disposed a magnetism detecting element 55, which is supported by a casing not shown. 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. Therefore, when the rotor 51 is attached to the shaft 52 with their center axes in misalignment or the rotor 51 itself rotates eccentrically, if the code plate 54 rotates via the shaft 52 as the rotor 51 rotates, since the code plate 54 rotates eccentrically, a gap G between the code plate and the magnetism detecting element 55 changes greatly and therefore a linear output is not 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. 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 rotating together with a rotation portion of a detection side around a Z-axis and having a magnetized portion at an outer circumferential surface; an almost rectangular first supporting member having a pair of sidewalls extending along an X-axis and a pair of sidewalls extending along a Y-axis, said member rotatably supporting the rotor at its central part and including a magnetic detecting element oppositely faced against the magnetized portion to detect a rotating state of said rotor; and a second supporting member having a pair of guide walls extending along the Y-axis and holding the pair of sidewalls extending along the Y-axis of said first supporting member therebetween and movably guiding the first supporting member in a Y direction; and a housing having a concave housing part for storing said second supporting member and X-direction guide means arranged above and below the second supporting member along the Y-axis and holding the second supporting member therebetween and guiding said second supporting member movably in an X direction. 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. Preferably, the rotation sensor includes 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. Preferably , 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. Preferably, the 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. Also, 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. Preferably, 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. Preferably , 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. Advantageously , 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. Also, 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. In addition , 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. Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which: Fig. 1 is an exploded perspective view showing a rough shape of a rotation sensor according to the present invention. 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. Fig. 4 is a cross-sectional view taken along the line 4-4 of Fig. 2. Fig. 5 is a front view of a housing used in the rotation sensor. Fig. 6 is a vertical cross-sectional view of the housing. Fig. 7 is a horizontal cross-sectional view of the housing. Fig. 8 is a front view of a rotor used in the rotation sensor. Fig. 9 is a vertical cross-sectional view of the rotor. Fig. 10 is a side view of the rotor. Fig. 11 is a front view of a core supporter used in the rotation sensor. Fig. 12 is a vertical cross-sectional view of the core supporter. Fig. 13 is a side view of the core supporter. Fig. 14 is a front cross-sectional view of a first supporter used in the rotation sensor. Fig. 15 is a cross-sectional view taken along the line 15-15 of Fig. 14. Fig. 16 is a cross-sectional view taken along the line 16-16 of Fig. 14. Fig. 17 is a side view of the first supporter. Fig. 18 is a bottom view of the first supporter. Fig. 19 is a front view of a second supporter used in the rotation sensor. Fig. 20 is a cross-sectional view taken along the line 20-20 of Fig. 19. Fig. 21 is a cross-sectional view taken along the line 21-21 of Fig. 19. Fig. 22 is a side view of the second supporter. Fig. 23 is a schematic diagram showing a conventional rotation sensor. 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, groove parts 23a are continuously provided, the terminals of the detecting members 6 are guided, and 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, 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. Although the rotor 4 is inserted from the front of the housing part 22 with some press, a total of four locations, the three element securing parts 23 and the concave part 5a which contact tightly with the rotor 4, bend evenly, and 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 press 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. 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.

Claims: A rotation sensor comprising: a rotor (4) rotating together with a rotation portion of a detection side around a Z-axis and having a magnetized portion at an outer circumferential surface; an almost rectangular first supporting member (5) having a pair of sidewalls extending along an X-axis and a pair of sidewalls extending along a Y-axis, said member rotatably supporting the rotor (4) at its central part and including a magnetic detecting element (6) oppositely faced against the magnetized portion to detect a rotating state of said rotor (4); and a second supporting member (8) having a pair of guide walls (27) extending along the Y-axis and holding the pair of sidewalls extending along the Y-axis of said first supporting member (5) therebetween and movably guiding the first supporting member (5) in a Y direction; and a housing (1) having a concave housing part (10) for storing said second supporting member (8) and X-direction guide means (12) arranged above and below the second supporting member (8) along the Y-axis and holding the second supporting member therebetween and guiding said second supporting member (8) movably in an X direction. The rotation sensor according to Claim 1, wherein both said first supporting member and said housing are constructed from a synthetic resin and said second supporting member is constructed from metal. The rotation sensor according to Claim 1 or 2, wherein a terminal is provided in said housing, and said terminal and said detecting member are connected by a flexible connecting wire. The rotation sensor according to Claims 1, 2 or 3, wherein said first supporting member is of shape of almost rectangular frame and the first supporting member is slidably disposed on said second supporting member. The rotation sensor according to any preceding claim, wherein the rotation part of said detection side is a throttle valve. The rotation sensor according to any preceding claim, wherein said first supporting member is provided with a frame part (21) resiliently contacted with said rotor (4) and flexed to support said rotor in a rotatable manner.

Inventors: OGAWA TOSHITO, YAMAZAKI KENJI, OGAWA, TOSHITO, YAMAZAKI, KENJI, Yamazaki, Kenji, Gureisu Furukawa, Room 206, 161-1
Applicants: ALPS ELECTRIC CO LTD, ALPS ELECTRIC CO., LTD.
Application year: 1999
Main classification: G01P1
IPC codes: G01B7, G01D5, G01P3, G01P1, G01B21