Rotary sensor

Abstract: In a rotary sensor of this invention, an angle detection member (16) is composed of sliding pieces (16a) having contact portions on a rotation body side and a conductive pattern formed on a substrate (17) arranged on a side opposite to the sliding pieces (16a), the operation shaft (23) has a flat projection portion (23a) which extends in a perpendicular direction from the center of rotation at the end, and a groove portion (15d) extends in a direction perpendicular to the axial direction of the operation shaft (23), the projection portion (23a) is mated with the groove portion (15d), and the contact portions (16b) of the sliding pieces (16a) are located at positions in a direction substantially perpendicular to the groove direction of the groove portion (15d).

Description: The present invention relates to a rotary sensor and, particularly to a rotary sensor capable of detecting a rotation angle transmitted from a shaft to be detected with high accuracy. As shown in Fig. 7, a prior art rotary sensor comprises a substantially cylindrical housing 1, a case 2 having a cavity portion 2a therein, and a cover 3 for closing the cavity portion 2a by fixing this case 2 thereto. A shaft hole 3a is formed in the cover 3, and a rotation body 4 having a shaft portion 4a at the center of rotation is stored in the cavity portion 2a. The shaft portion 4a is rotably inserted into the shaft hole 3a of the cover 3 and projects outward from the cover 3. The diameter of the above shaft hole 3a is made slightly larger than the diameter of the shaft portion 4a and the shaft portion 4a is inserted into and mated with the shaft hole 3a. An oval engagement hole 4a, for example, is formed in the end portion of the shaft portion 4a at the center of rotation and an operation shaft 8 which will be described hereinafter is inserted into this engagement hole 4b. A resistor substrate 5 is installed on the cavity portion 2a side of the cover 3, and an unshown substantially U-shaped resistor pattern is formed on the surface of the resistor substrate 5 by printing. Sliding pieces 6 provided on the rotation body 4 are elastically brought into contact with the resistor pattern and slide over the resistor pattern when the rotation body 4 turns so that the resistance value changes with a predetermined curve. A plurality of terminals 7 connected to the above resistor pattern are attached to a lower side in the figure of the above resistor substrate 5 by caulking or the like. To detect the rotation angle of, for example, the throttle valve of a car using this prior art rotary sensor, the cover 3 is attached to a predetermined attachment member (not shown), and the operation shaft 8 which is a shaft to be detected shown by a two-dotted chain line and connected to the throttle valve of the car is press fitted in the engagement hole 4b of the shaft potion 4a. The end portion of this operation shaft 8 is shaved oval and this oval end portion is engaged with the oval engagement hole 4b of the shaft portion 4a to transmit the rotation of the operation shaft 8 to the rotation body 4. As the above operation shaft 8 is displaced or decentered in a thrust direction which is an axial direction and a radial direction perpendicular to the axial direction during-the assembly of the'parts of the throttle valve, the rotary sensor must absorb the displacement or decentering of the operation shaft 8. The absorption of the displacement or decentering of the operation shaft 8 is carried out by making the diameter of the shaft hole 3a in the cover 3 larger than the diameter of the shaft portion 4a of the rotation body 4 so that even when the operation shaft 8 is displaced or decentered in a radial direction, the shaft portion 4a can turn the rotation body 4 smoothly without contact between the shaft portion 4a and the shaft hole 3a. The above-mentioned prior art rotary sensor can detect the rotation angle of the operation shaft 8 because when the operation shaft 8 connected to the rotary shaft of a throttle valve or the like turns at a predetermined angle, the rotation body 4 turns smoothly, the sliding pieces 6 slide over the resistor pattern to change the resistance value, and an unshown control portion detects this change in resistance value. However, as the above-mentioned prior art rotary sensor involves such a problem that, when the operation shaft 8 turns, the rotation body 4 is displaced or decentered by the displacement or decentering of the operation shaft 8, and the sliding pieces are shifted from the track of the resistor pattern with the result of large fluctuations in resistance value because the shaft portion 4a of the rotation body 4 is directly attached to the operation shaft 8 which is displaced or decentered in a thrust direction or radial direction. As a result, the rotation angle cannot be detected with high accuracy. As means of eliminating the influence of the displacement of the operation shaft 8, there is a method in which the operation shaft 8 and the shaft portion 4a are in contact with each other on only one plane in a rotation direction to transmit only the rotation in one direction of the operation shaft 8 to the rotation body 4, and the rotation body 4 is turned along with the rotation of the operation shaft 8 by the spring pressure of a return spring or the like when the operation shaft 8 turns in another direction so that the operation shaft 8 and the shaft portion 4a turn together. However, this method requires such a part as a return spring or the like, thereby increasing the number of parts and boosting costs. For further details of conventional rotary sensors, see GB-A-2,236,191 and US-A-4,806,809. It is an object of the present invention to provide a rotary sensor which solves the above problems and can detect a rotation angle with high accuracy by absorbing the displacement or decentering of the operation shaft 8 even if the operation shaft 8 is displaced or decentered. According to the present invention, there is provided A rotary sensor and an operation shaft, wherein said rotary sensor is engageable with an engagement end provided on an end of said operation shaft of an apparatus for measuring the angle of rotation of said operation shaft about an axis thereof, said rotary sensor comprising: a housing mounted to said apparatus; a rotation body rotatably supported by said housing and having an axis substantially parallel to the axis of said operation shaft said rotation body being provided with sliding pieces attached to a lower surface thereof, said sliding pieces having contact portions, and an engagement portion for mating engagement with said engagement end of said operation shaft, and a substrate having a conductive pattern arranged in a circular annular fashion, with said axis of said rotation body being applied as a centre and in sliding contact with said contact portions of said sliding pieces, characterized in that; said engagement end of said operation shaft comprises either a groove or a projection that extends in a first radial direction which crosses at a right angle said axis of said rotation body and in a second radial direction crossing at right angle with said axis of said rotation body and with said first direction, and said engagement portion of said rotation body comprises a projection or a groove that extends in said first direction for engagement with said engagement end of said'operation shaft, said engagement portion of said rotation body and said engagement end of said operation shaft are in engagement with each other so as to be displaceable relative to each other in said first direction but not displaceable in said second direction, said contact portions are arranged so as to contact said conductive pattern at positions which are in said second direction, said rotation body is not displaced in a radial direction of its axis even if said operation shaft is displaced in said first direction, and said rotation body is displaced in said second direction when said operation shaft is displaced in said second direction, said contact portions of said rotation body are moved in said second direction along with the former displacement and the segments of said contact portions contacted with said conductive pattern move on said conductive pattern in a diameter direction of said conductive pattern. The above and other objects and advantages of the present invention will become apparent from the following description when taken into conjunction the accompanying drawings. 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 a sectional view of key parts of a rotary sensor according to the present invention; Fig. 2 is a schematic plan view for explaining the relationship among key parts according to the present invention; Figs. 3A and 3B are a side view and a front view of an elastic member, respectively, according to the present invention; Figs. 4A and 4B are a side view and a front view of key portions of an operation shaft, respectively, according to the present invention; Fig. 5 is a schematic plan view for explaining the relationship among key parts according to another embodiment of the present invention; Fig. 6 is a schematic plan view for explaining the relationship among key parts according to still another embodiment of the present invention; and Fig. 7 is a sectional view of key parts of a prior art rotary sensor. A rotary sensor according to an embodiment of the present invention will be described hereinunder with reference to the accompanying drawings. Fig. 1 is a sectional view of key parts of the rotary sensor of the present invention, Fig. 2 is a schematic plan view for explaining the positional relationship of key parts of the present invention, Figs. 3A and 3B are diagrams of the elastic member of the present invention, Figs. 4A and 4B are schematic diagrams of the end portion of the operation shaft of the present invention, and Figs. 5 and 6 are schematic plan views of other embodiments of the present invention. As shown in Fig. 1, the rotary sensor of the present invention comprises a housing 10 which is shaped like a box (not shown) and made from a resin material or the like, and the bottom portion of the housing 10 is covered by a bottom wall 11. Part of the bottom wall 11 is projected to the right side of the figure to form a substantially cylindrical storage portion 12 which is defined by a side wall 13 and a bottom plate 14. A support portion 14a is formed substantially at the center of the bottom plate 14 on the storage portion '12 side in such a manner that it projects toward the storage portion 12 and a hemispherical bearing portion 14b which is a recessed portion is formed in the center portion of the support portion 14a. A substrate holding portion 14c for attaching a substrate 17 which will be described hereinafter is formed on the storage portion 12 side of the bottom plate 14 near the side wall 13. In the storage portion 12, a rotation body 15 made of a substantially disk-like resin material is rotably stored with a center line A as the center of its rotation. A pair of engagement walls 15c and 15c opposed to each other with the center line A therebetween are formed on the left side in the figure of the rotation body 15 and a groove portion 15d having a predetermined width and extending in a direction perpendicular to the center line A is formed between the pair of engagement walls 15c and 15c. Substantially semi-circular projection portions 15e and 15e are formed at the ends of the engagement walls 15c and 15c in such a manner that they project toward the groove portion 15d side. A shaft portion 15b whose end portion is substantially hemispherical and projects from the center of rotation is formed on the other right side in the figure of the rotation body 15. This shaft portion 15b is rotably pivoted on the bearing 14b of the bottom plate 14 and cannot move in a direction perpendicular to the center line A. Sliding pieces 16a which are made of a metal plate having spring properties as one of components constituting an angle detection member 16 are attached to a side to which the shaft portion 15b is formed of the rotation body 15. As shown in Fig. 2, the sliding pieces 16a have contact portions 16b which are in sliding contact with a substantially center portion of a conductive pattern composed of resistors 17a and formed on the substrate 17 which will be described hereinafter, and the contact portions 16b are located at positions in a direction substantially perpendicular to the groove direction of the groove portion 15d of the rotation body 15. The insulating substrate 17 is positioned and fixed to the substrate holding portion 14c of the bottom plate 14 on a side opposite to the side to which the sliding pieces 16a are attached of the rotation body 15 by caulking or the like. The conductive pattern is formed on the surface of the substrate 17 and composed of resistors 17a consisting of substantially circular arc resistor patterns and collecting patterns formed by printing or the like, and the contact portions 16b of the sliding pieces 16a are sliding contacted to the substantially center portions in a width direction of the resistors 17a. The above angle detection member 16 consists of the sliding pieces 16a and the substrate 17 having the resistors 17a. At a lower end portion of the substrate 17 shown in Fig. 1, a plurality of substantially L-shaped terminals 18 are connected to the respective resistors 17a, drawn from the end surface of the substrate 17 and guided along the inner surface of the side wall 13, and the end portions 18a of the terminals 18 are drawn to the left side of the figure and soldered to an unshown lead pattern formed on an FPC 19. An upper plate 20 for covering the storage portion 12 is provided on the left side in Fig. 1 of the rotation body 15, attached to attachment projections 11a formed at a plurality of sites of the bottom wall 11 and fixed to the bottom wall 11 by thermally caulking or the like. An opening portion 20a in which the pair of engagement walls 15c and 15c of the rotation body 15 are situated are formed in the center portion of the upper plate 20, and a cylindrical support wall 20b is formed around this opening portion 20a in such a manner that it projects toward the rotation body 15. The support wall 20b prevents the rotation body 15 from being inclined at an angle more than a predetermined angle. A gap 21 is formed between the upper plate 20 and the rotation body 15, and an elastic member 22 is placed in the gap 21. This elastic member 22 is a ring-shaped plate material having spring properties, such as a phosphor bronze plate. As shown in Fig. 3, flat ring-shaped attachment portions 22a are formed in the elastic member 22 at a plurality of sites and an attachment hole 22b is formed in each of the attachment portions 22a. Some parts of the ring-shaped elastic member 22 are curved to form a plurality of elastic portions 22c. The attachment holes 22b are caulked to projections (not shown) formed on the rotation body 15 and the elastic member 22 is attached to the inner wall of the upper plate 20. The spring pressure of the elastic portions 22c is made larger than the spring pressure of the sliding pieces 16a. The plurality of elastic portions 22c of the elastic member 22 are always elastically contacted to the rotation body 15, the rotation body 15 is thereby pressed toward the bottom plate 14 side, the shaft portion 15b is supported by the bearing portion 14b of the support portion 14a, the rotation of an operation shaft 23 which will be described hereinafter is transmitted, and the rotation body 15 is rotably stored in the storage portion 12. To detect the rotation angle of the throttle valve of a car or the like using the rotary sensor of the present invention constituted as described above, the housing 10 is first attached to an throttle body (not shown). Then, as shown in Fig. 1, the operation shaft 23 which is the shaft to be detected and connected to the rotation shaft (not shown) of the throttle valve is inserted into the groove portion 15d formed of the pair of engagement walls 15c and 15c of the rotation body 15 and placed in position. This operation shaft 23 is formed like a cylindrical rod and has a flat projection portion 23a which extends in a direction perpendicular to the center line A as the center of rotation at the end so that it can swing at a predetermined rotation angle. The above projection portion 23a is inserted into the groove portion 15d of the rotation body 15 and the rotation body 15 is turned by the rotation of the operation shaft 23. Although the rotation angle detection range of the above angle detection member 16 is approximately 100° when the angle detection sensor of the present invention is used as a throttle sensor, this rotation angle detection range is not fixed and varies according to the type of sensor and there is available a sensor capable of detecting an endless range of rotation angle. The above operation shaft 23 is displaced in a thrust direction which is an axial direction, or displaced or decentered in a radial direction which is optional direction perpendicular to the axial direction for such a reason as the accuracies of parts of the throttle valve. Preferably, the rotary sensor is able to detect the rotation angle without an error or rotation angle with a little error if any, or the rotation direction of the operation shaft 23 by absorbing the displacement or decentering of the operation shaft 23. That is, since the rotary sensor of the present invention is constituted as shown in Fig. 2 that the contact portions 16b of the sliding pieces 16a are situated at positions in a direction substantially perpendicular to the groove direction (shown by an arrow C) of the groove portion 15d and are in sliding contact with the resistors 17a, when the operation shaft 23 is decentered and the center of the rotation of the operation shaft 23 is displaced in a direction shown by an arrow B, the rotation body 15 is also displaced by the decentering of the operation shaft 23, and the contact portions 16b of the sliding pieces 16a move in a direction shown by the arrow B within the range of the width direction of each of the resistors 17a. Since the distance between an electrode 17b and the contact portion 16b does not change at this point, there is almost no change in resistance value. Since the contact portions 16b are situated substantially at the centers in a width direction of the resistors 17a, even if the operation shaft 23 is displaced or decentered, the contact portions 16b and the resistors 17a are not shifted from each other and do not become nonconductive. Since the projection portion 23a of the operation shaft 23 moves in the groove direction of the groove portion 15d when the displacement or decentering of the operation shaft 23 is in the direction shown by the arrow C which is the groove direction of the groove portion 15d shown in Fig. 2, the displacement or decentering in the direction shown by the arrow C of the operation shaft 23 is not transmitted to the rotation body 15, thereby eliminating its influence upon the resistance value. Further, as the end portion of the shaft portion 15b of the rotation body 15 is supported by and mated with the bearing portion 14b of the bottom plate 14, even if the operation shaft 23 is displaced or decentered in a radial direction, the rotation angle of the operation shaft 23 can be detected with high accuracy. When the operation shaft 23 is displaced in a thrust direction (axial direction), as shown in Fig. 1, the projection portion 23a of the operation shaft 23 situated in the groove portion 15d can freely move in the axial direction of the center line A in the groove portion 15d and can absorb the displacement of the operation shaft 23 in a thrust direction. Preferably, the conductive pattern is formed of the resistors 17a. In another embodiment of the present invention, the conductive pattern may be formed of an electrode having a plurality of pulse generation portions formed radiately and having their center at the center of rotation as shown in Fig. 5, which may be used in an encoder type rotary sensor. In this encoder type rotary sensor, the conductive pattern is formed of an electrode having a plurality of pulse generation portions, output obtained by bringing the contact portions 26b and 26d of sliding pieces 26a and 26c attached to the rotation body 15 into sliding contact with the plurality of pulse generation portions intermittently is processed by a CPU (not shown), and the rotation angle or rotation direction of the operation shaft 23 is detected. The conductive pattern formed of the encoder type electrode as described above consists of an A phase electrode 28, B phase electrode 29 and common electrode 30 formed on the substrate 27 as shown in Fig. 5. The above A phase electrode 28 has a ring-shaped A phase pattern 28a near the periphery of the substrate, and this A phase pattern 28a has a plurality of comb tooth-like pulse generation portions 28b which are formed radiately on an inner side and have their center at the center of the rotation of the rotation body 15. An A phase terminal 28c connected to the A phase pattern 28a is drawn to the outside. The B phase electrode 29 has a ring-shaped B phase pattern 29a on an inner side of the A phase pattern 28a, this B phase pattern 29a has a plurality of comb tooth-like pulse generation portions 29b which are formed radiately on an outer peripheral side and have their center at the center of the rotation of the rotation body 15, and the pulse generation portions 29b are shifted from the pulse generation portions 28b of the A phase pattern 28a at a predetermined angle. A B phase terminal 29c connected to the B phase pattern 29a is drawn to the outside. The common electrode 30 has a common pattern 30a formed like a ring on an inner side of the B phase pattern 29a, and a common terminal 30b connected to the common pattern 30a is drawn to the outside. The A phase pattern 28a, B phase pattern 29a and common pattern 30a are all made of a metal sheet and embedded in the substrate 27 in such a manner that they are exposed from the surface of the substrate 27. The common electrode 30 and the A phase electrode 28 are connected to each other by the A phase sliding piece 26a attached to the rotation body 15. That is, one of the contact portions 26b of the A phase sliding piece 26a is brought into sliding contact with the common electrode 30 and the other contact portion 26b is brought into sliding contact with the pulse generation portions 28b of the A phase electrode 28 intermittently. The contact portions 26b are attached to the rotation body 15 such that they are located substantially at the center of the projection portion of each of the comb tooth-like pulse generation portions 28b. The common electrode 30 and the B phase electrode 29 are connected to each other by the B phase sliding piece 26c attached to the rotation body 15. That is, one of the contact portions 26d of the B phase sliding piece 26c is brought into sliding contact with the common electrode 30 and the other contact portion 26d is brought into sliding contact with the pulse generation portions 29b of the B phase electrode 29 intermittently. The contact portions 26d are attached to the rotation body 15 such that they are located substantially at the center of the projection portion of each of the comb tooth-like pulse generation portions 29b. Also in this encoder type rotary sensor according to another embodiment of the present invention, even when the operation shaft 23 is displaced in a thrust direction, or displaced or decentered in a radial direction, the rotation angle or rotation direction of the operation shaft 23 can be detected with high accuracy by absorbing the displacement or decentering. Preferably, the end of the shaft portion 15b of the rotation body 15 is supported by and mated with the bearing 14b of the bottom plate 14. When the rotation body 15 is elastically urged toward one side (the operation shaft 23 side shown in Fig. 1) and the operation shaft 23 is mated with the groove portion 15d of the rotation body 15, even if the operation shaft 23 is displaced or decentered, the rotation angle or rotation direction of the operation shaft 23 can be detected with high accuracy by absorbing the displacement or decentering. As shown in Fig. 6, the engagement walls 25c and 25c may be formed at two locations in a direction shown by an arrow C which is the groove direction, and the projection portion 23c of the operation shaft 23 may be mated with groove portions 25d and 25d formed by these engagement walls 25c at the two locations. That is, the rotary sensor of the present invention is constituted such that' the groove portions 25d extend in a direction perpendicular to the axial direction of the operation shaft 23, the projection portion 23a is mated with the groove potions 25d, and the contact portions 16b of the sliding pieces 16a are located at positions in a direction (shown by an arrow B) substantially perpendicular to the groove direction (shown by an arrow C) of the groove portions 25d. The groove portions 25d may be formed in the operation shaft 23 and the projection portion 23a may be formed in the rotation body 15.

Claims: A rotary sensor and an operation shaft (23), wherein said rotary sensor is engageable with an engagement end (23a) provided on an end of said operation shaft (23) of an apparatus for measuring the angle of rotation of said operation shaft (23) about an axis thereof, said rotary sensor comprising: a housing (10) mounted to said apparatus; a rotation body (15) rotatably supported by said housing (10) and having an axis (A) substantially parallel to the axis of said operation shaft (23) said rotation body (15) being provided with sliding pieces (16a) attached to a lower surface thereof, said sliding pieces (16a) having contact portions (16b), and an engagement portion (15c) for mating engagement with said engagement end (23e) of said operation shaft (23), and a substrate (17) having a conductive pattern (17a) arranged in a circular annular fashion, with said axis (A) of said rotation body (15) being applied as a center and in sliding contact with said contact portions (16b) of said sliding pieces (16a), characterized in that ; said engagement end (23a) of said operation shaft (23) comprises either a groove (15d, 25d) or a projection (23a) that extends in a first radial direction (C) which crosses at a right angle said axis (A) of said rotation body (15) and in a second radial direction (B) crossing at right angle with said axis (A) of said rotation body (15) and with said first direction (C), and said engagement portion (15c) of said rotation body (15) comprises a projection (23a) or a groove (15d, 25d) that extends in said first direction (C) for engagement with said engagement end (23a) of said operation shaft (23), said engagement portion (15c) of said rotation body (15) and said engagement end (23a) of said operation shaft (23) are in engagement with each other so as to be displaceable relative to each other in said first direction (C) but not displaceable in said second direction (B), said contact portions (16b) are arranged so as to contact said conductive pattern (17a) at positions which are in said second direction (B), said rotation body (15) is not displaced in a radial direction of its axis (A) even if said operation shaft (23) is displaced in said first direction (C), and said rotation body is displaced in said second direction (B) when said operation shaft (23) is displaced in said second direction (B), said contact portions (16b) of said rotation body (15) are moved in said second direction (B) along with the former displacement and the segments of said contact portions (16b) contacted with said conductive pattern (17a) move on said conductive pattern (17a) in a diameter direction of said conductive pattern (17a). The rotary sensor according to Claim 1, wherein the groove (15d, 25d) is formed by a pair of walls (15c, 25c) which are opposed to each other with the center of the rotation of the rotation body (15) therebetween. The rotary sensor according to any preceding claim, wherein the conductive pattern (17a) is formed of a radial pattern and the center of the radial pattern is located at the same position as the center of the rotation of the rotation body (15). The rotary sensor according to any proceeding claim, wherein the rotation body (15) has a shaft portion (15b), which cannot be moved in a direction perpendicular to axis A of the rotation body, and including an elastic member (22) for depressing against the rotation body (15), the rotation body (15) being pivotally supported at the housing (10) by the shaft portion (15b).

Inventors: OKUMURA HIROFUMI, OKUMURA, HIROFUMI, Okumura, Hirofumi, Alps Electric Co., Ltd.
Applicants: ALPS ELECTRIC CO LTD, ALPS ELECTRIC CO., LTD.
Application year: 1999
Main classification: G01D5
IPC codes: F02D35, F02D9, G01B7, H01C10, G01D5