JP2007139614A - Torque sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque sensor capable of detecting a fine torque applied to an output shaft receiving rotation from a motor or the like. <P>SOLUTION: An end yoke 7 and the first and second cylindrical yokes 5, 6 are arranged so as to enclose an elastic cylindrical body 4 where a plurality of slits 4d are arranged, to thereby constitute a magnetic circuit together with the elastic cylindrical body 4, and a yoke having each built-in coil 10 is press fitted so that a separation groove 11 is formed on an adjacent yoke. Hereby, each yoke is integrated and its inner/outer circumference can be processed before including each coil, and each yoke can be arranged accurately concentrically. While one shaft part is press fitted into a thick-walled flange 4a of the elastic cylindrical body 4, a serration 3c is provided on the other shaft part to which a thin-walled cylindrical end 4b is connected, and the thin-walled cylindrical end 4b is caulked from its circumference along the serration 3c. Consequently, when mounting the elastic cylindrical body 4 on the shaft part, a strain such as a torsion is not generated on a bridge part 4e of the elastic cylindrical body 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement in a torque sensor that detects a minute torque applied to an output shaft that receives rotation from a motor or the like and rotates.

  Conventionally, a torque sensor shown in FIGS. 4 and 5 has been developed as a torque sensor for detecting a minute torque applied to an output shaft of a motor or the like. This torque sensor 1 has a housing 2, and a torsion bar 3 having an input shaft portion 3a, an output shaft portion 3b, and a torsion portion 3c having a cross-shaped cross section is rotatably held in the housing hole 2a. Yes. Engagement projections 3d that can be engaged with the tool shaft side such as the motor side and the driver bit are provided at the ends of the input shaft portion 3a and the output shaft portion 3b, respectively. Only rotation can be transmitted to 3b. The torsion bar 3 is provided with an elastic cylindrical body 4 including a thick flange 4a, a thin cylindrical end portion 4b, and a thin cylindrical portion 4c positioned therebetween so as to cover the torsion portion 3c of the torsion bar 3. The input shaft portion 3a is press-fitted into the thick flange 4a, and the output shaft portion 3b is fixed to the thin cylindrical end portion 4b with an adhesive 12. The thin cylindrical portion 4c of the elastic cylindrical body 4 is provided with a plurality of slits 4d on the input shaft portion 3a side and the output shaft portion 3b side, and a bridge portion 4e is formed between two adjacent slits. . The slits 4d extend on the circumference of the slit at an equal interval with respect to the axis with a predetermined inclination angle, and the inclinations are opposite to each other.

  In addition, the housing 1 includes a convex first cylindrical yoke 5, a concave second cylindrical yoke 6, and ends positioned at both ends thereof so as to contain the thin cylindrical portion 4 c of the elastic cylindrical body 4 in the housing hole 2 a of the housing 2. Part yokes 7a and 7b are arranged. The first cylindrical yoke 5 and the second cylindrical yoke 6 are combined with each other to form one excitation coil 9, and the end yokes 7a and 7b are combined with the first cylindrical yoke 5 or the second cylindrical yoke 6 to detect the detection coil. 10 is built in. The first cylindrical yoke 5 and the second cylindrical yoke 6 have annular walls 5a and 6a projecting inward, respectively. The annular walls 5a and 6a and the end yokes 7a and 7b are bridges of the elastic cylindrical body 4. It is configured to be positioned with a slight gap from the portion 4e.

  In this torque sensor 1, the rotation of the input shaft portion 3 a is transmitted to the output shaft portion 3 b via the elastic cylindrical body 4, but if a slight load torque is applied to the output shaft portion 3 b side, the torsion portion of the torsion bar 3 Twist occurs in 3c in the direction of the arrow shown in FIG. 6, and the elastic cylinder 4 is also twisted in the inclination direction of the slit 4d located on the output shaft portion 3b side by the twist. At this time, the bridge portion 4e formed by the slit 4d located on the output shaft portion 3b side is distorted in a drum shape, and the bridge portion 4e formed by the slit 4d located on the input shaft portion 3a side is distorted in a drum shape. Due to this distortion, the gap between the bridge portion 4e and the first cylindrical yoke 5 and the second cylindrical yoke 6 changes, and the end yokes 7a and 7b, the bridge portion 4e, the first cylindrical yoke 5 and the second cylindrical yoke 6 are formed. The number of magnetic fluxes in the magnetic circuit to be changed is changed, and a voltage change corresponding to this is detected by the detection coil 10. This voltage change is detected by the detection coils 10 at both ends, and these are amplified by a differential circuit (not shown), and the output value of the torque sensor 1 is detected. A torque value applied to the output shaft portion 3b is calculated from the detected value.

Patent 3,692,494

  In this torque sensor 1, if the gap between the bridge portion 4e of the elastic cylindrical body 4 and the end yokes 7a and 7b, the first cylindrical yoke 5 or the second cylindrical yoke 6 is not uniform over the entire circumference, the detection accuracy is affected. Therefore, each yoke manufactured one by one requires high precision inner and outer periphery processing that strictly controls the tolerance, shape accuracy and surface roughness of each yoke so that they can be positioned concentrically. Not only is a processing machine required, but the processing time is also long. Further, a high concentricity must be selected from a large number of manufactured yokes and assembled in the housing 2, and extra yokes must be manufactured, resulting in a high part cost.

  Further, when the elastic cylindrical body 4 is fixed to the output shaft portion 3b of the torsion bar 3, if the bridge portion 4e is distorted by torsion, torque ripple appears or the linearity of the detected value is deteriorated. The output shaft portion 3b is fixed to the thin cylindrical end portion 4b with an adhesive 12 so that no load is applied to the bridge portion 4e. For this reason, the adhesive 12 hardens or becomes brittle due to a change over time, and further, the output shaft 3b and the thin cylindrical end 4b of the elastic cylindrical body 4 due to the difference in thermal expansion between the output shaft 3b and the adhesive 12. May be peeled off, and it is necessary to strengthen the adhesion between the output shaft portion 3b and the thin cylindrical end portion 4b.

  In order to solve the above problems, the present invention provides an end yoke and a cylindrical yoke so as to surround the outer periphery of an elastic cylindrical body having a plurality of slits on the circumference, and a detection coil and an excitation coil are respectively disposed on these yokes. In a torque sensor that arranges a coil and forms a magnetic circuit together with an elastic cylinder and detects a radial displacement of the elastic cylinder as a torque value from a change in magnetic flux in the magnetic circuit, a yoke on which each coil is arranged It is press-fitted into the adjacent yoke so that a separation groove is formed on the outer periphery. The two adjacent yokes may be integrally processed so that the outer periphery and the inner hole are concentric in the press-fitted state, and may have positioning markings on the outer periphery. Good. Further, the press-fitted yoke may be integrally processed and then reassembled with the built-in excitation coil and detection coil. Moreover, the elastic cylindrical body may be fixed to a torsion bar having a torsion part.

  According to another invention, the end yoke and the cylindrical yoke are arranged so as to surround the outer periphery of the elastic cylindrical body provided with a plurality of slits on the circumference, and the detection coil and the excitation coil are respectively disposed on these yokes. In a torque sensor that forms a magnetic circuit together with an elastic cylinder and detects a radial displacement of the elastic cylinder as a torque value from a change in magnetic flux in the magnetic circuit, a thick wall is formed at each end of the elastic cylinder. A flange and a thin cylindrical end are provided, and one shaft is press-fitted into the thick flange, while a non-rotating groove is provided on the other shaft connected to the thin cylindrical end, and a thin wall is formed along the anti-rotation groove. The cylindrical end is caulked from its outer periphery. The elastic cylinder may be attached to a torsion bar.

  According to the present invention, the cylindrical yoke in which the exciting coil is built in and the end yoke arranged so as to sandwich the exciting coil are detachably press-fitted with the separation groove. Therefore, these yokes can be once press-fitted and integrated to form an inner and outer peripheral shape without a coil being arranged in each yoke. In addition, after processing of these yokes is completed, a tool can be inserted into the separation groove, the yokes can be detached, and then an excitation coil and a detection coil can be incorporated in each yoke, and these can be re-press-fitted and fixed. Thereby, not only can the outer peripheral shape of each yoke manufactured individually and its inner hole be processed concentrically, the housing hole of the housing and the inner hole of each yoke can be positioned accurately concentrically. In addition, since the end face of the end yoke can be processed simultaneously with the processing of its outer periphery, these squarenesses can be secured, and the input and output shaft portions can be arranged concentrically with the inner hole of the yoke.

  According to another aspect of the invention, a rotation stop groove is provided in the output shaft portion connected to the thin cylindrical end portion of the elastic cylindrical body, and the thin cylindrical end portion is caulked from the outer periphery along the rotation stop groove. Therefore, when attaching the elastic cylindrical body to the output shaft portion, the bridge portion of the elastic cylindrical body is not subject to distortion such as torsion. The elastic cylinder can be firmly fixed to the shaft portion.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. 1 and 2, reference numeral 1 denotes a torque sensor having a housing 2 provided with a storage hole 2a. In the storage hole 2a, a torsion bar 3 having a cross-shaped torsion part 3c having a cross-section is rotatably held via bearings. The input shaft part 3a and the output shaft part 3b located at both ends of the torsion bar 3 are rotatably held. Are provided with engaging projections 3d so as to be connected to the drive shaft side of a motor (not shown) and the tool shaft side such as a driver bit (not shown). The output shaft portion 3b is provided with a serration 3e extending as a rotation stop groove in parallel with the axis thereof, and the serration 3e is disposed so as to slightly protrude from a thin cylindrical end portion 4b described later.

  The torsion bar 3 is arranged so that an elastic cylindrical body 4 comprising a thick flange, 4a thin cylindrical end portion 4b, and a thin cylindrical portion 4c having a thin cylindrical shape located between them, includes the torsion portion 3c. An input shaft portion 3a of the torsion bar 3 is press-fitted into the thick flange 4a. Further, as shown in FIG. 3, an output shaft 3b is inserted into the thin cylindrical end 4b, and the thin cylindrical end 4b is caulked at a position where the serration 3e slightly protrudes. The caulking portion of the thin cylindrical end portion 4b is pushed into the groove of the serration 3e, and the elastic cylindrical body 4 and the output shaft portion 3b of the torsion bar 3 are configured to rotate integrally. The thin cylindrical end 4b is caulked by rotating a caulking tool (not shown) having a caulking roller rotatably disposed around the thin cylindrical end 4b toward the thin cylindrical end 4b. 4e is configured so as not to be distorted.

  The thin cylindrical portion 4c of the elastic cylindrical body 4 is provided with a plurality of slits 4d on the input shaft portion 3a side and the output shaft portion 3b side, and a bridge portion 4e is formed between two adjacent slits 4d. ing. The slits 4d are inclined at a predetermined inclination angle with respect to the axis of the elastic cylindrical body 4 at equal intervals, and the inclinations are opposite to each other, and one bridge portion 4e is inclined in the inclination direction of the slit 4d. When the drum portion is twisted, the other bridge portion 4e is twisted in the direction opposite to the inclination direction of the slit 4d and is distorted into a drum shape.

  A first cylindrical yoke 5, a second cylindrical yoke 6, and bottomed cylindrical end yokes 7a and 7b sandwiching the first cylindrical yoke 5 and the second cylindrical yoke 6 are disposed in the housing hole 2a of the housing 2. The first cylindrical yoke 5 and the second cylindrical yoke 6 have annular walls 5a and 6a in the cylinder, and the end yoke 7 has an inner hole equal to the inner diameter of the annular walls 5a and 6a. The first cylindrical yoke 5 has protrusions at both ends, and the second cylindrical yoke 6 has a recess at one end and a protrusion at the other end. Further, the end yokes 7a and 7b have recesses corresponding to the protrusions of the adjacent first cylindrical yoke 5 or second cylindrical yoke 6, and the first cylindrical yoke 5, the second cylindrical yoke 6 and these are connected to each other. The sandwiched end yokes 7 a and 7 b are press-fitted and fixed integrally with adjacent ones, and these yokes are press-fitted into the housing holes 2 a of the housing 2 so as to enclose the elastic cylindrical body 4.

  The first cylindrical yoke 5 and the second cylindrical yoke 6 incorporate an exciting coil 9 wound around a bobbin-like coil holder 8 made of an insulating material, and the end yokes 7a and 7b similarly A detection coil 10 wound around the coil holder 8 is incorporated. At this time, the gap between the inner walls of the annular walls 5a and 6a and the end yokes 7a and 7b of the first cylindrical yoke 5 and the second cylindrical yoke 6 and the thin cylindrical portion 4c of the elastic cylindrical body 4 is uniform in the entire circumferential direction. The first magnetic circuit is constituted by the first cylindrical yoke 5, the end yoke 7 a and the elastic cylindrical body 4, and the second cylindrical yoke 6, the end yoke 7 b and the elastic cylindrical body 4 are used for the second magnetic circuit. A magnetic circuit is configured.

  Further, the projections of the first cylindrical yoke 5 and the second cylindrical yoke 6 are longer than the hole depth of the corresponding recess, and a separation groove 11 is formed between two adjacent yokes. 11 is configured such that a blade edge such as a flathead screwdriver (not shown) can be inserted. Furthermore, two adjacent yokes have positioning markings on the outer periphery, and the inner and outer peripheral shapes and surface roughness of at least two integrated yokes are processed with a predetermined processing accuracy, and these are disassembled. The assembly position when reassembling each coil later is shown.

  In the torque sensor, the two adjacent yokes are integrated with the separation groove 11 formed therein, and therefore can be separated from the separation groove 11. Therefore, when processing the inner and outer peripheral shapes and surface roughness of each yoke, before the yokes are press-fitted into the housing 2, the detection coil 10 and the exciting coil 9 are integrated without being incorporated, Circumferential shape and surface roughness can be processed, and each yoke can be processed accurately and concentrically. Further, since the integrated yoke can process not only the inner and outer circumferences but also the end surfaces of the end yokes 7a and 7b, the squareness of the end surfaces can be ensured accurately.

  After these processes are completed, if marking is performed on two adjacent yokes, and a tool is pushed into the separation groove 11 to release each yoke, the end yokes 7a and 7b, the first cylindrical yoke 5 and the first Each of the two cylindrical yokes 6 includes a detection coil 10 and an excitation coil 9, and each yoke can be press-fitted again according to the marking and reassembled. Therefore, by simply pushing the reassembled yoke into the housing 2, the outer periphery of each yoke and the center of the inner hole can be made to coincide with each other, and these can also be made to coincide with the center of the housing hole 2a of the housing 2. it can.

  Further, when the elastic cylindrical body 4 inserted through the integrated yoke is fixed to the torsion bar 3, the input shaft portion 3a is press-fitted into the thick flange 4a of the elastic cylindrical body 4, while the output shaft portion 3b A thin cylindrical end portion 4b of the elastic cylindrical body 4 is caulked from the periphery of the provided serration 3e. Therefore, the bridge portion 4e of the elastic cylindrical body 4 is not distorted by the caulking, and only the torsion due to the load applied to the output shaft portion 3a is transmitted to the bridge portion 4e, and this can be accurately detected.

In this embodiment, the torsion bar 3 is inserted into the elastic cylinder 4 and the elastic cylinder 4 is fixed so as to contain the torsion part 3c. However, the input shaft part 3a and the output shaft part 3b are separately provided. As a body, both shaft portions may be connected by an elastic cylindrical body 4. Further, it may be possible to press-fit until the edges of the two adjacent yokes are in close contact with each other. In this case, a part of one of the edges is scraped and a groove is cut into a part of the outer periphery of the two adjacent yokes. 11 may be formed. Furthermore, the marking for positioning may be an inscription or other method. Moreover, the output shaft portion 3b and the input shaft portion 3a of the torsion bar 3 to which the elastic cylindrical body 4 is attached may be reversed and attached to the housing 2, and after the adhesive is applied to the thin cylindrical end portion 4b. The thin cylindrical end 4b may be caulked.

It is a longitudinal cross-sectional view of this invention. It is a principal part expanded sectional view of this invention. It is principal part explanatory drawing which shows the state which rotated the caulking part of the elastic cylinder which concerns on this invention 90 degree | times. It is a longitudinal cross-sectional view which shows the conventional torque sensor. It is a partially cutout principal part external view which shows the attachment state of the elastic cylinder which concerns on the conventional torque sensor. It is principal part expansion explanatory drawing explaining the operation state of the elastic cylinder which concerns on the conventional torque sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Torque sensor 2 Housing 2a Storage hole 3 Torsion bar 3a Input shaft part 3b Output shaft part 3c Torsion part 3d Engaging protrusion 3e Serration 4 Elastic cylindrical body 4a Thick flange 4b Thin cylindrical end part 4c Thin cylindrical part 4d Slit 4e Bridge Part 5 First cylindrical yoke 5a Annular wall 6 Second cylindrical yoke 6a Annular wall 7a, 7b End yoke 8 Coil holder 9 Excitation coil 10 Detection coil
11 Separation groove
12 Adhesive

Claims (7)

An end yoke and a cylindrical yoke are arranged so as to surround the outer circumference of an elastic cylinder having a plurality of slits on the circumference, and a detection coil and an excitation coil are arranged on these yokes, respectively, and a magnetic circuit is formed together with the elastic cylinder. In a torque sensor configured to detect a displacement in the radial direction of the elastic cylindrical body as a torque value from a change in magnetic flux in the magnetic circuit,
A torque sensor characterized in that a yoke in which each coil is disposed is press-fitted into an adjacent yoke so as to form a groove by separating the outer periphery. The torque sensor according to claim 1, wherein at least two adjacent yokes are integrally processed so that the outer periphery and the inner hole are concentric in a press-fitted state. The torque sensor according to claim 1, wherein two adjacent yokes have positioning markings on an outer periphery. 4. The torque sensor according to claim 1, wherein the press-fitted yoke is integrally processed and then reassembled with the built-in excitation coil and detection coil. The torque sensor according to claim 1, 2, 3, or 4, wherein the elastic cylindrical body is fixed to a torsion bar having a torsion portion. An end yoke and a cylindrical yoke are arranged so as to surround the outer circumference of an elastic cylinder having a plurality of slits on the circumference, and a detection coil and an excitation coil are arranged on these yokes, respectively, and a magnetic circuit is formed together with the elastic cylinder. In a torque sensor configured to detect a displacement in the radial direction of the elastic cylindrical body as a torque value from a change in magnetic flux in the magnetic circuit,
A thick flange and a thin cylindrical end are provided at the ends of the elastic cylinder, respectively, and one shaft is press-fitted into the thick flange, while a rotation stop groove is formed on the other shaft connected to the thin cylindrical end. A torque sensor characterized in that a thin cylindrical end portion is caulked from the outer periphery along the anti-rotation groove. The torque sensor according to claim 6, wherein the elastic cylindrical body is attached to a torsion bar.

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