JP2005214664A - Torque sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque sensor capable of stabilizing a magnetic field generated in the torque sensor. <P>SOLUTION: This torque sensor is constituted of a torsion bar, a first rotating shaft comprising a magnetic material and connected to one end side of the torsion bar, a second rotating shaft connected to the other end side of the torsion bar, a first cylindrical member provided on the first rotating shaft so as to enclose the first rotating shaft and having the first window, the second cylindrical member provided on the second rotating shaft so as to enclose the first window and having the second window, and a coil assembly provided on the circumference of the second cylindrical member and having a coil arranged inside. The torque sensor is also constituted so that a torque is detected, which is generated from the coil between the first rotating shaft and the second rotating shaft as an impedance change by changing the overlapping degree between the first window and the second window resulting from torsion of the torsion bar. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a torque sensor that detects a relative rotational displacement (torque) of an input shaft and an output shaft in an electric power steering apparatus.

Conventionally, as a torque sensor, for example, a technique described in Patent Document 1 has been disclosed. In this publication, an input shaft and an output shaft are connected by a torsion bar in the torque sensor, and a cylindrical member made of aluminum is doubled on the outer periphery of the input shaft. The inner cylindrical member is fixed on the output shaft side, and the outer cylindrical member is provided on the input shaft side. With this configuration, relative rotation occurs between the input shaft and the inner cylindrical member due to torsion of the torsion bar.
JP-A-8-114518 (see FIG. 1).

  However, the above torque sensor has the following problems. When relative rotation occurs between the input shaft and the output shaft, the axis of the input shaft does not completely match the axis of the inner cylindrical member. The interval changes. Therefore, the magnetic field generated in the torque sensor becomes unstable, and the torque detection accuracy may be reduced.

  The present invention has been made paying attention to the above problem, and an object thereof is to provide a torque sensor capable of stabilizing a magnetic field generated in the torque sensor.

  In order to achieve the above object, according to the present invention, a torque sensor includes a torsion bar, a first rotating shaft made of a magnetic material connected to one end of the torsion bar, and a first connected to the other end of the torsion bar. 2 is a through hole provided on the first rotation shaft so as to surround the first rotation shaft and formed in a cylindrical shape with a conductive and non-magnetic material and provided in the axial direction. A first cylindrical member having a first window; and a second rotating shaft so as to surround the first window; a cylindrical shape made of a conductive and non-magnetic material; A second cylindrical member having a second window, which is a through-hole, and a coil assembly provided on the outer periphery of the second cylindrical member and having a coil disposed therein, and torsion of the torsion bar By changing the overlap of the first and second windows , A coil as the impedance change was to detect the torque generated between the first rotary shaft and second rotary shaft.

  Therefore, it is possible to prevent the interval between the first rotating shaft and the first cylindrical member from changing, and the magnetic field generated in the torque sensor can be stabilized.

  Hereinafter, the best mode for realizing the torque sensor of the present invention will be described based on Example 1 shown in the drawings.

FIG. 1 is a system configuration diagram of an electric power steering apparatus according to the first embodiment.
The electric power steering apparatus mainly includes an input shaft 1 and an output shaft 2 connected via a torsion bar 3, coil assemblies 9A and 9B including coils 9a and 9b, a pinion shaft 20, and a rack shaft 21.

  A steering wheel (not shown) is integrally attached to the right side of the input shaft 1 in FIG. 1 in the rotational direction, and a pinion shaft 20 is connected to the output shaft 2. The pinion shaft 20 and the rack shaft 21 constitute a rack and pinion type steering device.

  A cylindrical member 4 is fixed to the input shaft 1 so as to cover the outer periphery of the input shaft 1. A cylindrical member 5 is fixed to the output shaft 2 so as to cover the cylindrical member 4. Details of the cylindrical members 4 and 5 will be described later with reference to FIG.

  Coil assemblies 9A and 9B including coils 9a and 9b are fixed to the case 8 so as to cover the outside of the cylindrical member 5. A substrate 7 is connected to the coil assemblies 9A and 9B via a cable 6. An electric motor control circuit is mounted on the substrate 7.

  The steering force of the driver is transmitted from the input shaft 1, the torsion bar 3, and the output shaft 2 to the rack shaft 21 through the pinion shaft 20, and is transmitted to the steered wheels (not shown). When the driver performs a steering operation, the degree of overlap between the window of the cylindrical member 4 and the window of the cylindrical member 5 changes as the torsion bar 3 fixed between the input and output shafts twists. At this time, when the impedance change generated in the coils 9 a and 9 b is transmitted to the board 7, the steering torque is calculated in the board 7. A drive current that generates a steering assist torque that reduces the steering torque based on the calculation result is supplied to an electric motor (not shown). By transmitting the rotational force of the electric motor to the output shaft 2 via the worm gear 19, a steering assist torque having an arbitrary direction and magnitude is applied.

FIG. 2 is a configuration diagram of the torque sensor according to the first embodiment.
The torque sensor of the first embodiment mainly includes a torsion bar 3, an input shaft 1 (corresponding to a first rotating shaft in claims), an output shaft 2 (corresponding to a second rotating shaft in claims), A cylindrical member 4 (corresponding to a first cylindrical member in claims), a cylindrical member 5 (corresponding to a second cylindrical member in claims), and coil assemblies 9A and 9B including coils 9a and 9b. Is done. The input shaft 1 and the output shaft 2 are connected via fixed portions 3a and 3b of the torsion bar 3. The input shaft 1 and the output shaft 2 are both made of a magnetic material such as iron.

  On the input shaft 1 side end surface of the output shaft 2, a groove 2 a extending further in the radial direction from the insertion portion of the torsion bar 3 is formed. The groove 2 a is formed on the output shaft 2 side end surface of the input shaft 1. The projected portion 1a is inserted. However, the width (circumferential dimension) of the groove 2a is slightly wider than the width of the convex portion 1a, and prevents relative rotation beyond a predetermined range between the input shaft 1 and the output shaft 2.

  The cylindrical member 4 is tightly fixed to the input shaft 1 so as to surround the large diameter portion 1A. The cylindrical member 4 is made of a conductive and nonmagnetic material (aluminum material in this embodiment), and a plurality of first windows 4a provided in the axial direction (corresponding to the first window in the claims). Have

  The cylindrical member 5 is closely fixed to the output shaft 2 so as to cover the cylindrical member 4 at the small diameter portion 5A. The cylindrical member 5 is made of a conductive and non-magnetic material (aluminum material in this embodiment), and a plurality of second windows 5a and 5b (corresponding to the second window in the claims) provided in the axial direction. Have

  The two sets of coil assemblies 9A and 9B are arranged side by side in the axial direction so as to surround the outer periphery of the cylindrical members 4 and 5. The coils 9a, 9b, the first window 4a, and the second windows 5a, 5b are arranged so as to face each other in the radial direction.

(Contrast with torque sensor in conventional example)
FIG. 8 is a diagram showing a configuration of a torque sensor in a conventional example.
In this torque sensor, a cylindrical member made of an aluminum material is provided on the outer periphery of the input shaft 1 in a double manner. Among these cylindrical members, the inner cylindrical member 5 is tightly fixed to the output shaft 2 side via the small diameter portion 5A, and the outer cylindrical member 4 is firmly fixed to the input shaft 1 via the small diameter portion 4A.

  However, in this configuration, when relative rotation occurs between the output shaft 2 and the cylindrical member 5 and the input shaft 1 and the cylindrical member 4 due to torsion of the torsion bar 3, both the cylindrical members 4 and 5 are cantilevered. Since the shaft center of the input shaft 1 and the shaft center of the output shaft 2 do not completely coincide with each other, the distance between the input shaft 1 and the inner cylindrical member 5 changes due to relative rotation. Therefore, the magnetic field generated in the torque sensor becomes unstable, and the torque detection accuracy may be reduced.

  Further, the cylindrical member 4 is closely fixed to the input shaft 1 in the small diameter portion 4A, and the cylindrical member 4 becomes longer in the axial direction and the radial direction, so that the apparatus becomes larger.

  On the other hand, in the torque sensor of the present embodiment, the cylindrical member 4 is provided so as to surround the large-diameter portion 1A of the input shaft 1. The cylindrical member 4 is closely fixed to the input shaft 1 by press fitting or the like, and has a plurality of first windows 4a provided in the axial direction. In addition, the cylindrical member 5 is configured to have a plurality of second windows 5 a and 5 b that are closely fixed to the output shaft 2 so as to cover the cylindrical member 4 and that are provided in the axial direction. Thereby, relative rotation does not occur at least between the input shaft 1 and the cylindrical member 4, and the distance between the input shaft 1 and the cylindrical member does not change. Therefore, the magnetic field generated in the torque sensor is stabilized and the torque detection accuracy is improved (corresponding to claim 1).

  In addition, the cylindrical member 4 is not directly connected to the small diameter portion 4a as in the conventional example, but is directly fixed to the input shaft 1 by press fitting or the like, so that the cylindrical member 4 can be reduced in the axial direction and the radial direction. It becomes. Therefore, the apparatus can be reduced in size.

  Further, since the cylindrical member 4 and the input shaft 1 are closely fixed, the magnetic field generated between the input shaft 1 and the coils 9a and 9b is at least in the gap between the input shaft 1 and the cylindrical member 4 from the first window 4a. There is no entry. Therefore, the magnetic field generated in the torque sensor is stabilized. Therefore, it is possible to improve the torque detection accuracy.

  Next, Example 2 will be described with reference to FIGS. Since the basic configuration of the torque sensor is the same as that of the first embodiment, only different points will be described.

The cylindrical member 4 of Example 2 is closely fixed to the input shaft 1 by caulking. Hereinafter, the caulking and fixing will be described in detail.
FIG. 3 is a side view of the input shaft 1, and FIG. 4 is a side view of the cylindrical member 4. The outer diameter of the large diameter portion 1A is set to φD, and the inner diameter of the cylindrical member 4 is set to φd. The difference between φd and φD is set as an arbitrary caulking allowance.

(When caulking and fixing the input shaft and cylindrical member outside the window in the axial direction)
5A and 5B are a side view and an AA end view when the input shaft 1 and the cylindrical member 4 are caulked and fixed outside the range of the first window 4a in the axial direction.

  The first window 4a is formed at a substantially intermediate portion in the axial direction of the cylindrical member 4, and the input shaft 1 and the cylindrical member 4 are fixed by caulking at a caulking fixing portion 12A outside the range of the first window 4a in the axial direction.

  Since the cylindrical member 4 is caulked and fixed to the input shaft 1 outside the range of the first window 4a, deformation of the cylindrical member 4 and changes in internal stress caused by caulking are unlikely to affect the first window 4a, and torque Detection accuracy is improved.

  In addition, by caulking and fixing outside the range of the first window 4a, the size and shape of the caulking fixing portion 12A are less likely to affect the first window 4a, and the degree of freedom in designing the caulking fixing portion 12A is also increased.

  Further, the caulking fixing portions 12 are provided at equal intervals in the circumferential direction. That is, since the crimping fixing portions 12 are provided at equal intervals, the stress acting on the cylindrical member 4 is evenly applied, and the change in the magnetic field in the circumferential direction is equalized, so that the magnetic field generated in the torque sensor is stabilized. Therefore, it is possible to improve the torque accuracy detection.

  Next, Example 3 will be described with reference to FIG. Since the basic configuration of the torque sensor is the same as that of the first embodiment, only different points will be described.

  Also in the third embodiment, as in the second embodiment, the input shaft 1 is firmly fixed by caulking. Further, the caulking fixing portions 14A are provided at equal intervals in the circumferential direction as in the second embodiment. However, the fixing position is different from the second embodiment. Hereinafter, caulking and fixing according to the third embodiment will be described in detail.

(When fixing the input shaft and the cylindrical member within the range of the first window in the axial direction)
In the third embodiment, a case where the input shaft 1 and the cylindrical member 4 are caulked and fixed within the range of the first window 4a in the axial direction will be described.

  6A and 6B are a side view and a C-C end view when the input shaft 1 and the cylindrical member 4 are caulked and fixed within the range of the first window 4a in the axial direction.

  Since the caulking fixing portion 14A is provided at a substantially intermediate portion in the axial direction of the two sets of coil assemblies 9A and 9B, two sets of influences such as deformation of the cylindrical member 4 generated in the caulking fixing portion 14A and changes in internal stress are caused. The influence on the coils 9a and 9b can be minimized and equalized, and the magnetic field generated in the torque sensor is stabilized. Therefore, it is possible to improve the torque detection accuracy. Further, since it is not necessary to provide the caulking fixing portion 14A outside the first window 4a in the cylindrical member 4, it is possible to reduce the axial direction of the cylindrical member 4. Therefore, the apparatus can be reduced in size.

  Further, the caulking fixing portion 14 </ b> A includes a first concave portion 15 and a convex portion 16 formed in the cylindrical member 4 so as to be fitted to the first concave portion 15 within the range of the first window 4 a in the axial direction. Composed. Furthermore, a second recess 17 is provided on the outer periphery of the input shaft 1 at the same axial position on the outer periphery as the first recess 15.

  Note that when the caulking is fixed within the range of the first window 4 a in the axial direction, the first recess 15 of the input shaft 1 is hidden by the cylindrical member 4. Therefore, by positioning the first recess 15 and the second recess 17, the first recess 15 of the input shaft 1 and the caulking fixing portion 14 </ b> A of the cylindrical member 4 can be easily positioned. Therefore, it is possible to perform caulking and fixing at an appropriate position, and it is possible to minimize the influence of the deformation of the cylindrical member 4 and the change in internal stress caused by the caulking and fixing.

  Next, Example 4 will be described with reference to FIG. Since the basic configuration of the torque sensor is the same as that of the first embodiment, only different points will be described.

  Also in the fourth embodiment, as in the second embodiment, the input shaft 1 is firmly fixed by caulking. Further, the caulking fixing portions 13A are provided at equal intervals in the circumferential direction as in the second embodiment. Further, as in the third embodiment, the input shaft 1 and the cylindrical member 4 are caulked and fixed within the range of the first window 4a in the axial direction. However, the positioning method is different from the third embodiment. Hereinafter, differences from the third embodiment regarding the caulking and fixing of the fourth embodiment will be described in detail.

  FIG. 7 is a side view and a C-C end view when the first recess 15 is used for caulking and the third recess 18 is used for positioning.

  The caulking fixing portion 13 </ b> A includes a first concave portion 15 and a convex portion 16 that is formed in the cylindrical member 4 so as to be fitted into the first concave portion 15 within the range of the first window 4 a in the axial direction. The The input shaft 1 is provided with a third recess 18 in the same axial direction as the first recess 15 and corresponding to the first window 4a of the cylindrical member 4, and the first recess 15 and the caulking fixing portion of the input shaft 1 are provided. The positioning of 13A was performed. Since the third recess is in a position that can be seen from the first window 4a, the caulking fixing portion 13A can be easily positioned even when the first recess 15 of the input shaft 1 is hidden by the cylindrical member 4. Accordingly, it is possible to perform the caulking and fixing at an appropriate position, and it is possible to minimize the influence of the deformation of the cylindrical member 4 and the change in internal stress generated in the caulking and fixing portion 13A.

  Further, technical ideas other than the claims that can be grasped from the respective embodiments will be described below together with the effects thereof.

(A) In the torque sensor according to claim 1,
The torque sensor, wherein the first rotating shaft and the first cylindrical member are fixed in close contact with each other.

  A magnetic field generated between the input shaft 1 and the coils 9a and 9b does not enter the gap between the input shaft 1 and the cylindrical member 4 from the first window 4a. Therefore, the magnetic field generated in the torque sensor is stabilized. Therefore, it is possible to improve the torque detection accuracy.

(B) In the torque sensor according to claim 1,
The first window is formed at a substantially middle portion of the first cylindrical member, and the first rotating shaft and the first cylindrical member are fixed within the range of the first window in the axial direction. Torque sensor characterized by the above.

  In the cylindrical member 4, since it is not necessary to provide the caulking fixing portions 13A and 14A outside the first window 4a in the axial direction, it is possible to reduce the axial direction of the cylindrical member 4. Therefore, the apparatus can be reduced in size.

(C) In the torque sensor described in (b) above,
Two sets of the coil assemblies are arranged side by side in the axial direction so as to face the second window,
A torque sensor, wherein a caulking fixing portion between the first rotating shaft and the first cylindrical member is provided at a substantially intermediate portion in the axial direction of two sets of coil assemblies.

  It is possible to minimize and evenly influence the influence of the deformation of the cylindrical member 4 generated in the crimping fixing portions 13A and 14A, the change of the internal stress, etc. on the two sets of coils 9a and 9b. The magnetic field to be stabilized is stabilized. Therefore, it is possible to improve the torque detection accuracy.

(D) In the torque sensor according to claim 1,
The first window is formed at a substantially intermediate portion in the axial direction of the first cylindrical member, and the first rotating shaft and the first cylindrical member are caulked outside the range of the first window in the axial direction. Fixed.

  Since the caulking is fixed outside the range of the first window 4a of the cylindrical member 4, deformation of the cylindrical member 4 and changes in internal stress due to the caulking are less likely to affect the first window 4a, and the magnetic field generated in the torque sensor is stabilized. . Therefore, it is possible to improve the torque detection accuracy.

(E) In the torque sensor described in (b) or (c) or (d),
The torque sensor, wherein the caulking fixing portions are provided at equal intervals in the circumferential direction of the cylindrical member.

  Since the caulking fixing portions 12A, 13A, and 14A are provided at equal intervals in the circumferential direction of the cylindrical member 4, the change in the magnetic field in the circumferential direction becomes uniform, so that the magnetic field generated in the torque sensor is stabilized. Therefore, it is possible to improve the torque accuracy detection.

(F) In the torque sensor described in (e) above,
The caulking fixing portion is composed of a concave portion formed on the first rotating shaft and a convex portion formed on the first cylindrical member and provided to fit into the concave portion,
The first rotation shaft is in the same axial direction as the first recess corresponding to the protrusion of the first cylindrical member, and the outer periphery of the first recess and the first rotation shaft. A torque sensor comprising: a second recess provided on the outer side in the axial direction than the cylindrical member.

  Since the second concave portion 17 and the first concave portion 15 are caulked and fixed so that they are in the same axial direction on the outer periphery of the input shaft 1, positioning at the time of fixing can be easily performed.

(G) In the torque sensor described in (f) above,
The caulking fixing portion is composed of a concave portion formed in the first rotating shaft and a convex portion formed in the first cylindrical member and provided to fit into the concave portion,
The first rotation axis is a first concave portion corresponding to the convex portion of the first cylindrical member, and the same axial position as the first concave portion, and a position corresponding to the first window. And a third recess provided in the torque sensor.

  Since the caulking is fixed so that the third recess 18 comes to the position of the first window 4a of the cylindrical member 4, the positioning at the time of fixing can be easily performed.

1 is a system configuration diagram of an electric power steering apparatus in Embodiment 1. FIG. It is a torque sensor block diagram in Example 1. FIG. 6 is a side view of an input shaft in Embodiment 2. FIG. 6 is a side view of a cylindrical member in Embodiment 2. FIG. In Example 2, it is the side view and sectional drawing at the time of crimping and fixing the input shaft and the cylindrical member outside the range of the window in the axial direction. In Example 3, it is the side view and sectional drawing in the case of using a 1st recessed part for crimping fixation, and a 2nd recessed part for positioning. In Example 4, it is the side view and sectional drawing in the case of using a 1st recessed part for crimping fixation, and a 3rd recessed part for positioning. It is a block diagram of the torque sensor in a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Input shaft 1a Convex part 1A Large diameter part 2 Output shaft 2a Groove 3 Torsion bar 3a Fixed part 3b Fixed part 4 Cylindrical member 4a 1st window 4c, 4d Window 4A Small diameter part 5 Cylindrical member 5a, 5b 2nd window 5c, 5d Window 5A Small-diameter portion 6 Cable 7 Substrate 8 Case 9A, 9B Coil assembly 9a, 9b Coil 12A Caulking fixing portion 13A Caulking fixing portion 14A Caulking fixing portion 15 First concave portion 16 Protruding portion 17 Second concave portion 18 Third concave portion 19 Worm gear 20 Pinion shaft 21 Rack shaft

Claims (1)

A torsion bar,
A first rotating shaft made of a magnetic material connected to one end of the torsion bar;
A second rotating shaft connected to the other end of the torsion bar;
A first window which is a through hole provided on the first rotating shaft so as to surround the first rotating shaft, formed in a cylindrical shape with a conductive and nonmagnetic material, and provided in a plurality in the axial direction. A first cylindrical member having
A second window which is a through hole provided on the second rotating shaft so as to surround the first window, formed in a cylindrical shape with a conductive and nonmagnetic material, and provided in a plurality in the axial direction. A second cylindrical member having
A coil assembly provided on an outer periphery of the second cylindrical member and having a coil disposed therein;
The coil is generated between the first rotating shaft and the second rotating shaft as a change in impedance by changing the overlapping state of the first window and the second window accompanying the twisting of the torsion bar. A torque sensor characterized by detecting torque to be transmitted.

Images