Rotary sensor capable of high-precision detection of rotation angle transmitted from outside

[0002] 1. Field of the Invention

[0003] This invention relates to a rotary sensor and more particularly to a rotary sensor capable of detecting with high precision a rotation angle transmitted from outside.

[0004] 2. Description of Related Art

[0005] A conventional rotary sensor has an unillustrated housing of an approximately cylindrical external shape, in which a disk-like rotator 1 is housed as shown in FIG. 10. The rotator 1 has a bearing portion 1bwhich projects to the right in the drawing from the center of a disk-shaped flange 1a. At the center of rotation of the bearing portion 1b, an oval-shaped shaft hole 1cis formed to a specific depth. In a part of the flange 1anear the root of the bearing portion 1b, a spring retaining portion 1dis projectively formed.

[0006] Around the bearing portion 1ba torsion coil spring 2 is mounted to elastically force the rotator 1 in a direction of rotation. The torsion coil spring 2 is retained at one end by the spring retaining portion 1dand at the other end on the housing side not shown.

[0007] On the left side surface of the flange 1aof the rotator 1 a slider piece not depicted is attached. On the opposite side of this slider piece an unillustrated resistor board on which a resistor pattern is formed is disposed. When the slider piece slides in elastic contact with the resistor pattern with the rotation of the rotator, the resistance value varies, thereby enabling detection of rotation angle of the rotator.

[0008] The conventional rotary sensor in use as an unillustrated throttle valve rotation sensor on an automobile will be explained. The throttle valve is coupled with the drive shaft 3 which transmits rotation of the throttle valve. The forward end 3aof drive shaft 3 is formed oval in configuration. When the conventional rotary sensor is attached on the throttle valve side and the drive shaft 3 is inserted into the shaft hole 1cof the rotator 1, the rotation of the drive shaft 3 is transmitted to the rotator 1.

[0009] The drive shaft 3 stated above is somewhat loose, and relatively off-centered, in a radial direction orthogonal to the axial direction because of assembly requirements of components on the throttle valve side. Absorption of this looseness or deviation from center of the drive shaft 3 has been required on the rotary sensor side.

[0010] In the conventional rotary sensor, therefore, the oval shaft hole 1cis made slightly larger in width and diameter than the forward end portion 3aof the drive shaft 3, so that the drive shaft 3 may be loose-fit in the shaft hole 1cto absorb the radial looseness and relative deviation from center of the drive shaft 3.

[0011] Since the drive shaft 3 is loose-fit in the shaft hole 1c, there occurs a backlash with the rotator 1 when the rotator 1 is rotated by the driven shaft 3, causing an error in the rotation of the rotator 1, resulting in a failure in proper detection of rotation angle on the drive shaft 3 side. To obviate this drawback, the torsion coil spring 2 is adopted to constantly apply an elastic force to the rotator 1 in one direction towards rotation in relation to the drive shaft 3, thus absorbing the backlash.

[0012] That is, when the drive shaft 3 rotates in one direction, the rotator 1 rotates in one direction against the spring force of the torsion coil spring 2. When the drive shaft 3 rotates in the other direction, the rotator 1 is independently rotated in the same direction with the spring force of the torsion coil spring 2.

[0013] The rotation angle of the drive shaft 3, therefore, cannot be detected with high precision if the drive shaft 3 has radical looseness in a radical direction and relative deviation from center.

[0014] The conventional rotary sensor stated above, however, has such a problem that the torsion coil spring 2 used therein is expensive because of a special configuration and accordingly the high cost of the rotary sensor results.

[0015] Since the drive shaft 3 is loose-fit in the shaft hole 1c, there will take place friction between the drive shaft 3 and the shaft hole 1cduring a long-time use, resulting in difficult high-precision detection of rotation angle.

[0016] In view of the above-described problems of the heretofore known rotary sensor, it is an object of this invention to provide a rotary sensor which ensures high-precision detection of rotation angle by absorbing looseness and relative deviation, if any, from center of the drive shaft 3 with respect to the rotary sensor.

[0017] As the first arrangement for solving to the above-described problems, the rotary sensor of this invention is comprised of a drive shaft having a flat portion at the forward end portion, a rotator provided with an engagement hole having a flat portion in which the forward end portion of the drive shaft is inserted, an elastic member having an elastic contact portion, and a rotation angle sensing member for detecting the rotation angle of the rotator; the rotator having a groove formed in parallel with the flat portion adjacently to the flat portion of the engagement hole, and a partition wall between the groove and the flat portion of the engagement hole; the partition wall having an open portion, through which the engagement hole communicates with the groove, from the opening to a specific depth of the engagement hole; and the elastic contact portion of the elastic member inserted in the groove projecting to the engagement hole side through the open portion, into elastic contact with the flat portion of the drive shaft.

[0018] As the second arrangement for solving to the above-described problems, the elastic member is made of a plate spring and the elastic contact portion is projectively formed with the plate spring partly curved. The crest of this curved part is projected to the engagement hole side into elastic contact with the flat portion of the drive shaft.

[0019] Furthermore, as the third arrangement for solving to the above-described problems, the elastic member has a retaining portion formed by raising on the opposite direction of projection of the elastic contact portion, to thereby retain the elastic member.

[0020] Furthermore, as the fourth arrangement for solving to the above-described problems, a through hole is formed in the curved crest part of the elastic contact portion.

[0021] FIG. 1 is a sectional view of a major portion of a rotary sensor of this invention;

[0022] FIG. 2 is a schematic front view of the rotary sensor of this invention;

[0023] FIG. 3 is a rear view of a major portion of the rotary sensor of this invention;

[0024] FIGS. 4A and 4B are a sectional view and a side view of a major portion of the rotator of this invention, respectively;

[0025] FIG. 5 is a perspective view of an elastic member of this invention;

[0026] FIGS. 6A and 6B are a front view and a side view of a drive shaft of this invention, respectively;

[0027] FIG. 7 is a perspective view explaining a modification of the elastic member of this invention;

[0028] FIG. 8 is a perspective view explaining the modification of the elastic member of this invention;

[0029] FIG. 9 is a perspective view explaining a modification of the elastic member of this invention; and

[0030] FIG. 10 is a perspective view of a major portion of a conventional rotary sensor.

[0031] One embodiment of a rotary sensor of this invention will hereinafter be described with reference to the accompanying drawings. FIG. 1 is a sectional view showing a major portion of the rotary sensor of this invention; FIG. 2 is a schematic front view of the rotary sensor of this invention; FIG. 3 is a rear view of a major portion of the rotary sensor of this invention; FIGS. 4A and 4B are a sectional view and a front view of a major portion of a rotator of this invention, respectively; FIG. 5 is a perspective view of an elastic member of this invention; FIGS. 6A and 6B are a front view and a side view of a drive shaft of this invention, respectively; and FIGS. 7 to 9 are perspective views explaining modifications of the elastic member of this invention.

[0032] The rotary sensor of this invention, as shown in FIG. 1, is provided with a housing 10 made of a thermosetting resin, which has an approximately cylindrical outside shape. The housing 10 has a front side plate 10aformed on the right side in the drawing, and a shaft hole 10bformed at the central part of the front side plate 10a.

[0033] In the housing 10 an approximately cylindrical housing section 11 is formed. A rotator 12 is disposed within the housing section 11. The rotator 12, as shown in FIG. 4, has a disk-like flange 12a, on the left and right sides in the drawing of which a small-diameter shaft portion 12band a large-diameter bearing portion 12care projectively formed respectively.

[0034] On the bearing portion 12ca step 12dis formed. On the right of this step 12din the drawing is formed a small-diameter forward end portion 12e. The forward end portion 12eis inserted into a shaft hole 10bof the housing 10, so that the rotator 12 is rotatable on the centerline A as the center of rotation within the housing section 11.

[0035] On the left side surface of the flange 12ain the drawing, a plurality of projections 12fare projectively formed, to thereby position and attach a later-described slider piece 18.

[0036] On the center of rotation of the bearing portion 12c, an engagement hole 13 of specific depth is formed. The engagement hole 13 includes a flat portion 13aand a circular portion 13b, and is formed in a D shape as viewed from the front and chamfered at the opening portion 13c.

[0037] Adjacently to the flat portion 13aof the engagement hole 13, a groove 14 of specific depth and width is formed in parallel with the flat portion 13a.

[0038] A partition wall 15 is formed between the groove 14 and the flat portion 13aof the engagement hole 13. At the partition wall 15, an open portion 16 through which the engagement hole 13 and the groove 14 communicate with is formed to a specific depth from the opening 13cof the engagement hole 13. The open portion 16, as shown in FIG. 4B, is formed smaller in width than the groove 14 and therefore the partition wall 15 projects on both sides of the open portion 16.

[0039] The groove 14 is formed to allow insertion of an elastic member 17 made of a plate spring. The elastic member 17, as shown in FIG. 5, has a cutout portion 17bformed by punching a base plate portion 17awith a press. Surrounded with the cutout portion 17b, a tongue-shaped elastic contact portion 17cand a retaining portion 17dare formed.

[0040] The elastic contact portion 17cis curved in an angle shape, projecting upwardly in the drawing. On the downward side in the drawing, that is, in the opposite direction of projection of the elastic contact portion 17c, a retaining portion 17dis formed by raising.

[0041] The elastic member 17 is provided with a through hole 17eof specific diameter formed by punching in the crest curved part of the elastic contact portion 17b, and a support portion 17fof specific height is formed by bending to the downward side in the same direction as the retaining portion 17dat the right end in the drawing.

[0042] As the elastic member 17 is inserted into the groove 14, the retaining portion 17dat one end side is elastically interposed between the lower side walls of the groove 14 and the support portion 17fon the other end side contacts the side walls of the groove 14. The level base plate portion 17ais pressed into elastic contact with the partition wall 15 on the side surface mainly of the open portion 16 by the elastic force of the retaining portion 17d. And the elastic member 17 is retained in the groove 14.

[0043] When the elastic member 17 is inserted into the groove 14, the curved crest part of the elastic contact portion 17cis positioned on the engagement hole 13 side, protruding through the open portion 16.

[0044] On the left side surface, in the drawing, of the flange 12aof the rotator 12 where the shaft portion 12bis formed, a resilient slider piece 18 which is a part of the rotation angle sensing member is attached. The slider piece 18 is positioned by means of a plurality of projections 12fformed on the flange 12aas shown in FIG. 3, and is fixedly attached to the rotator 12 by thermal caulking or the like.

[0045] On the opposite side of the surface on which the slider piece 18 is mounted, a resistor board 19 having a specific amount of clearance is positioned inside the housing 10 and securely attached by use of adhesive.

[0046] On the surface of the resistor board 19 an unillustrated resistor pattern is formed by printing, so that the slider piece 18 may elastically come into contact with the resistor pattern.

[0047] At the central part of the resistor board 19 there is formed a shaft hole 19ain which the shaft portion 12bof the rotator 12 is inserted. The rotation angle sensing member is made up of the resistor board 19 having the slider piece 18 and the resistor pattern.

[0048] In FIG. 1, below the resistor board 19 a plurality of approximately L-shaped external terminals 20 are unitarily formed with the housing 10 by an insert molding process. The external terminals 20 are connected by soldering to a terminal 30 led out from the end face of the resistor board 19 correspondingly to the resistor pattern.

[0049] In the drawing, on the left side of the resistor board 19 a cover 21 for covering the housing section 11 in the housing 10 is attached by adhesive, thereby hermetically enclosing the interior of the housing section 11. On the inner side on the centerline A of the cover 21, a bearing portion 21ais projectively formed as shown in FIG. 1 to support the shaft portion 12bof the rotator 12, thereby preventing movement of the rotator 12 in a direction perpendicular to the direction of the centerline A and preventing looseness.

[0050] To detect the rotation angle of a throttle valve on for instance an automobile by using the rotary sensor of this invention of the aforesaid configuration, first the housing 10 is attached to the body of the throttle body not depicted. Then, as shown in FIG. 1, a drive shaft 22 coupled with the throttle valve is inserted and positioned in the engagement hole 13 of the rotator 12.

[0051] The drive shaft 22, as shown in FIG. 6, is of such a shape that a round rod-like forward end portion 22ais provided with a flat portion 22bto form a D-shaped forward end portion 22a. The drive shaft 22 is designed to reciprocate within the specific range of rotation angle in interlock with the rotation of the throttle valve on the automobile side.

[0052] The drive shaft 22 stated above has a slight looseness of for instance about 0.1 mm, and relative center deviation, in the radial direction because of an assembly error on the throttle valve side. To properly engage the drive shaft 22 in the engagement hole 13 notwithstanding the presence of the looseness or center deviation, a play is provided between the drive shaft 22 and the engagement hole 13; and after assembling, the play is removed by holding the elastic contact portion 17cof the elastic member 17 in elastic contact with the flat portion 22bof the drive shaft 22 to thereby press the circular portion 13bof the engagement hole 13 against the drive shaft 22 side. Both the drive shaft 22 and the rotator 12 thus rotate as one body without the play.

[0053] Therefore, as the drive shaft 22 rotates in one direction, the rotator 12 can smoothly rotate without a backlash, following the rotation of the drive shaft 22. Even when the drive shaft 22 rotates in the other direction also, the rotator 12 can smoothly rotate, following the rotation of the drive shaft 22 without any backlash, due to the resilience of the elastic member 17. The rotation angle sensing member composed of the slider piece 18, therefore, can perform high-precision detection of rotation angle of the drive shaft 22.

[0054] Referring to FIG. 7 to FIG. 9, modifications of the elastic member 17 used in the rotary sensor of this invention will be explained. First, the elastic member 27 shown in FIG. 7 has a cutout portion 27bformed by punching the base plate portion 27a, thus forming a curved elastic contact portion 27cand a retaining portion 27d. The base plate portion 27ais bent downwardly on both sides in the drawing in the longitudinal direction, to thereby form the first support portions 27e, 27e. On the end of the base plate portion 27awhere the elastic contact portion 27cis formed, a second support portion 27fis formed by bending to the same height as the first support portions 27e. The elastic member 27, provided with the first support portions 27e, 27ethus formed, can reliably be fitted without looseness within the groove 14 and the drive shaft 22 can reliably be pressed in the engagement hole 13 by means of the elastic contact portion 27c.

[0055] The elastic member 37 shown in FIG. 8 has a curved elastic contact portion 37cin the cutout portion 37bformed in the base plate portion 37a. The base plate portion 37ais bent at the end in the longitudinal direction to thereby form first support portions 37d, 37d. On the lower end face of the first support portions 37d, 37d, downwardly projecting wedge-shaped retaining portions 37e, 37eare formed.

[0056] The base plate portion 37ahaving the elastic contact portion 37cthus formed is also provided at the end with a second support portion 37fformed by bending to the same height as the first support portion 37d. The elastic member 37 thus formed can be retained with reliability in the groove 14 by means of the wedge-shaped retaining portions 37e, 37eand the drive shaft 22 can be elastically pressed firmly in the engagement hole 13 by means of the elastic contact portion 37c.

[0057] The elastic member 47 shown in FIG. 9 is provided with a curved elastic contact portion 47cformed by punching a cutout portion 47bin an approximately square base plate portion 47a. An almost central part, in the longitudinal direction, of the base plate portion 47a, is protruding in a circular form in the same direction as the direction of the curved elastic contact portion 47c, forming the retaining portions 47d, 47d.

[0058] The elastic member 47 of such a configuration can easily be manufactured and elastically press to retain the drive shaft 22 in the engagement hole 13 with reliability by means of the elastic contact portion 47c.

[0059] In the embodiments of this invention heretofore explained, the rotation angle sensing member is a resistor type made up of a slider piece 18. It is to be noted, however, that the rotation angle sensing member may be a magnetic type not depicted or other fitted with a magnetic member on the outer periphery of the flange 12aof the rotator 12.

[0060] The rotator of the rotary sensor of this invention is provided with a groove formed in parallel with the flat portion adjacently to the flat portion of the engagement hole, and a partition wall between the groove and the flat portion of the engagement hole. The partition wall has an open portion of a specific depth from the opening of the engagement hole, through which the engagement hole and the groove communicate with. The elastic contact portion of the elastic member inserted in the groove protrudes through the open portion out to the engagement hole side and into elastic contact with the flat portion of the drive shaft. Therefore, if the drive shaft is inserted loose-fit in the engagement hole, the rotator can rotate without a backlash with rotation of the drive shaft. This invention, therefore, can provide a rotary sensor capable of detecting the rotation angle of the drive shaft with high precision by means of the sensing member.

[0061] The elastic member is produced of a plate spring; and the elastic contact portion is projectively formed by curving a part of the plate spring. The curved crest part protrudes to the engagement hole side into elastic contact with the flat portion of the drive shaft. It is, therefore, possible to easily make the elastic member on a press to thereby reduce the cost.

[0062] The elastic member has a retaining portion formed by cutting and bending up on the opposite side of direction of projection of the elastic contact portion, so that the elastic member is retained by this retaining portion. The elastic member, therefore, can be seated reliably in the groove by means of the retaining portion. Therefore, it is possible to prevent the elastic member from coming out and off the groove if the there has occurred looseness in the thrust direction, or in the axial direction of the drive shaft.

[0063] Furthermore, as a through hole is formed in the curved crest part of the elastic contact portion, it is possible to increase the spring pressure per unit area for elastically pressing the elastic contact portion against the flat portion of the drive shaft, and accordingly to reliably press to connect the rotator to the drive shaft.