JP4285248B2 - Torque sensor and steering angle sensor - Google Patents

Description

  The present invention relates to a torque sensor and a steering angle sensor applied to, for example, an electric power steering device for an automobile.

  There is an electric power steering device (steering device) for assisting the force for operating the steering wheel of an automobile. This is a mechanism that detects torque applied to the steering shaft and rotates an electric motor provided in the steering mechanism in accordance with the detected torque.

  As such a torque detection means, a first cylinder fixed to the output shaft and an input shaft connected to the output shaft via a torsion bar are fixed to the first cylinder opposite to the first cylinder. A torque sensor including a second cylinder and a detection coil that electromagnetically couples with the first and second cylinders is known (see Patent Document 1, etc.).

  A tooth surface is provided at a predetermined pitch in the circumferential direction on the opposing surface or outer peripheral surface of each cylindrical body. When torque acts on the steering shaft, an electrical change occurs in the detection coil by changing the area of the tooth surface overlapping in the axial direction. The torque sensor detects torque based on this electrical change.

  A torque sensor having a function as a steering angle sensor for detecting the steering angle of the steering shaft is also known (see Patent Document 2).

JP-A-7-294346 JP 2001-91375 A

  By the way, the tooth surface provided in each cylindrical body is generally formed by cutting such as an NC lathe. However, according to the cutting process, there are problems that it takes a long time for the process, and the material characteristics (magnetic characteristics, etc.) of the metal material change due to heat generated during the process. This makes it very difficult to adjust the sensor characteristics after cutting, which takes time and causes an increase in manufacturing costs.

  Therefore, an object of the present invention is to provide a torque sensor and a steering angle sensor that can be manufactured at low cost by facilitating manufacture.

In order to achieve the above object, a first aspect of the present invention is a torque sensor mounted on an input shaft and an output shaft connected via a torsion bar, and comprising a magnetic body fixed to the output shaft. One cylindrical body, a second cylindrical body made of a magnetic body fixed to the input shaft so as to face the first cylindrical body, and fixed to the input shaft so as to face the second cylindrical body. A third cylindrical body made of a magnetic material, a disc made of a non-magnetic material that is mounted on the opposing surface of each cylindrical body and has a plurality of through holes formed at predetermined intervals in the circumferential direction, and the first A torque sensor comprising: a detection coil that is electromagnetically coupled to the second cylindrical body; and a temperature compensation coil that is electromagnetically coupled to the second and third cylindrical bodies .

A second aspect of the present invention is the torque sensor according to the first aspect , wherein the through hole is formed by punching.

According to a third aspect of the present invention, there is provided a main cylinder made of a magnetic body fixed to a steering shaft, a sub cylinder made of a magnetic body mounted on the fixed side so as to face the main cylinder, and each cylinder. A disc made of a non-magnetic material that is mounted on each of the opposing surfaces of the body and has a circular arc-shaped through-hole of a predetermined length along the circumferential direction, and a detection coil that electromagnetically couples with the main and sub cylinders. A steering angle sensor including the steering angle sensor.

A fourth aspect of the present invention is the steering angle sensor according to the third aspect , wherein the through hole is formed by punching.

A fifth aspect of the present invention is the steering angle sensor according to the third or fourth aspect , wherein the through hole has a semicircular shape.

  According to the present invention, it is possible to produce the torque sensor and the steering angle sensor at low cost by facilitating the production.

  A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a side sectional view of a torque sensor according to an embodiment of the present invention.

  As shown in FIG. 1, this torque sensor is mounted on a steering shaft 1 of an automobile. The steering shaft 1 includes an input shaft 2 attached to a steering wheel (not shown) and an output shaft 3 attached to a steering mechanism (not shown). The input shaft 2 and the output shaft 3 are connected via a torsion bar 4. Specifically, openings are provided at the ends of the input shaft 2 and the output shaft 3, and the torsion bar 4 is accommodated in these openings. An annular case 5 is attached to a fixed side of a vehicle body (not shown). The case 5 is pivotally supported on the input shaft 2 via a bearing 6.

  A cylindrical first cylindrical body 7 made of a conductive material and a magnetic material (for example, low carbon steel, stainless steel, cast iron, etc.) is fixed to the outer peripheral surface of the output shaft 3. Specifically, the first cylinder 7 is press-fitted into the output shaft 3.

  On the outer peripheral surface of the input shaft 2, a cylindrical second cylindrical body 8 made of a conductive material and a magnetic material is provided opposite to the first cylindrical body 7 in the axial direction, and the second cylindrical body 8 has a shaft. A cylindrical third cylindrical body 9 made of a conductive material and a magnetic material is fixed so as to face the direction. Specifically, the second cylinder 8 and the third cylinder 9 are press-fitted into the input shaft 2.

  The first and second cylinders 7 and 8 and a detection coil 20 described later are provided for the purpose of detecting a steering torque acting on the steering shaft 1. The second and third cylinders 8 and 9 and a temperature compensation coil 21, which will be described later, are provided for temperature compensation when detecting the steering torque and the steering angle.

  A cylindrical fourth cylinder 10 made of a conductive material and a magnetic material is fixed to an inner peripheral surface of a detection coil 22 (yoke 19), which will be described later, facing the third cylinder 9 in the axial direction. ing. Specifically, the fourth cylinder 10 is press-fitted into the detection coil 22 (yoke 19). The inner peripheral surface of the fourth cylinder 10 is provided without contacting the outer peripheral surface of the input shaft 2 with a predetermined interval. Here, the 4th cylinder 10 should just be provided immovably. For example, the fourth cylinder 10 may be fixed to the inner peripheral surface of the case 5 via a support or the like.

  Here, in the present embodiment, the “main cylinder” in the claims is the “third cylinder 9”, and the “sub cylinder” is the “fourth cylinder 10”. It is. The “detection coil that electromagnetically couples with the main and sub cylinders” is the “detection coil 22”.

  The third and fourth cylinders 9 and 10 and the detection coil 22 are provided for the purpose of detecting the steering angle of the steering shaft 1. That is, the torque sensor shown in FIG. 1 can detect the steering angle in addition to the detection of the steering torque.

  A first disk 11 or a second circle made of a non-magnetic material (for example, a low-permeability material such as aluminum or stainless steel, the same shall apply hereinafter) is provided on the opposing surface of each cylinder 7, 8, 9, 10. Each of the plates 12 is mounted. In detail, the 1st disc 11 is each attached to the opposing surface of the 1st, 2nd cylinders 7 and 8, and the 2nd and 3rd cylinders 8 and 9. As shown in FIG. On the opposing surfaces of the third and fourth cylinders 9 and 10, second disks 12 are mounted, respectively.

  FIG. 2 is a front view of the first disc 11. FIG. 3 is a front view in which two first disks 11 are stacked in the axial direction. FIG. 4 is a front view of the second disk 12. FIG. 5 is a front view in which two second disks 12 are stacked in the axial direction.

  As shown in FIG. 2, a plurality of through holes 13 are formed on the side surface of the first disc 11 at a predetermined interval in the circumferential direction. The through hole 13 is formed by punching.

  As shown in FIG. 3, the opposing first disks 11 are arranged such that the through holes 13 are shifted by half the pitch. Thereby, the opposing through-holes 13 form overlapping portions 14 (indicated by hatching in the figure) that overlap in the axial direction.

  As shown in FIG. 1, a stopper 15 extending in the axial direction and having a predetermined width is provided on the outer peripheral surface of the input shaft 2 on the output shaft 3 side. On the other hand, a stopper guide groove 16 extending in the axial direction and having a predetermined width is provided on the inner peripheral surface of the output shaft 3 on the input shaft 2 side.

  The stopper 15 of the input shaft 2 is inserted into the stopper guide groove 16 of the output shaft 3, and the input shaft 2 and the output shaft 3 are approximately half the circumferential length of the through hole 13 of the first disc 11. Only be able to rotate relative.

  As shown in FIG. 4, an arc-shaped through-hole 17 having a predetermined length is formed on the side surface of the second disk 12 along the circumferential direction. The through hole 17 is formed in a semicircular shape (that is, an arc shape with an extension angle of 180 °) by punching.

  As shown in FIG. 5, the opposing second disks 12 are arranged such that the through holes 17 are shifted by half the pitch. Thereby, the opposing through-holes 17 form overlapping portions 18 (indicated by hatching in the figure) that overlap in the axial direction.

  Here, in FIG. 5, of the two second disks 12 stacked in the axial direction, the front side in the drawing is the third cylindrical body 9 side, and the back side in the drawing. It is assumed that the fourth cylinder 10 side is shown in FIG. In the present embodiment, the fourth cylinder 10 is fixed to the inner peripheral surface of the detection coil 22 and is provided so as not to contact the outer peripheral surface of the input shaft 2. The cylinder 9 and the fourth cylinder 10 have different inner and outer diameters of the second disk 12 to be mounted.

  As shown in FIG. 1, three ring-shaped yokes 19 made of a magnetic material are juxtaposed and fixed to the inner peripheral surface of the case 5. In the groove of each yoke 19, a detection coil 20, a temperature compensation coil 21, and a detection coil 22 are wound.

  The detection coil 20 is provided so as to cover the outer peripheral surfaces of the first and second cylinders 7 and 8 (opposite surfaces of the first and second cylinders 7 and 8). The cylinders 7 and 8 are electromagnetically coupled. The temperature compensation coil 21 is provided so as to cover the outer peripheral surfaces of the second and third cylinders 8 and 9 (opposing surfaces of the second and third cylinders 8 and 9). The cylinders 8 and 9 are electromagnetically coupled. The detection coil 22 is provided so as to cover the outer peripheral surfaces of the third and fourth cylinders 9 and 10 (opposing surfaces of the third and fourth cylinders 9 and 10). The cylinders 9 and 10 are electromagnetically coupled.

  FIG. 6 is a schematic diagram showing a detection circuit of the torque sensor of FIG.

  As shown in FIG. 6, the detection coil 20, the temperature compensation coil 21, and the detection coil 22 constitute a capacitor 23 and a parallel circuit, respectively. Each parallel circuit is connected to a voltage / current converter 27 via a transmitter 25 that generates a high-frequency signal for detecting impedance via a resistor 24 and a differential amplifier 26.

  A differential amplifier 26 and a voltage / current converter 27 shown on the upper side in the drawing are for detecting the steering torque τ, and are connected to a parallel circuit of the detection coil 20 and the temperature compensation coil 21. On the other hand, a differential amplifier 26 and a voltage / current converter 27 shown on the lower side in the figure are for detecting the steering angle θ, and are connected to a parallel circuit of the detection coil 22 and the temperature compensation coil 21. Yes.

  Next, the operation of the torque sensor according to the present embodiment will be described.

  When a current flows through the detection coil 20, the temperature compensation coil 21, and the detection coil 22 by the high-frequency signal from the transmitter 25 shown in FIG. 6, as shown in FIG. A magnetic circuit that circulates through the cylinders 7 and 8, a magnetic circuit that circulates through the temperature compensation coil 21, the second and third cylinders 8 and 9, and a detection coil 22, the third and fourth cylinders 9, 10 Are respectively formed. These magnetic circuits are formed through the through hole 13 (overlapping portion 14) of the first disc 11 or the through hole 17 (overlapping portion 18) of the second disc 12.

  When the steering shaft 1 (the input shaft 2 and the output shaft 3) is not rotated (when the steering torque is 0), the voltages of the detection coil 20 and the temperature compensation coil 21 are equal. When the steering shaft 1 is rotated, a steering torque acts on the torsion bar 4, and the first cylinder 7 and the second cylinder 8 are relatively rotated. Thereby, the area of the overlapping portion 14 of the first disk 11 changes (increases or decreases). When the area of the overlapping portion 14 changes, the impedance of the detection coil 20 changes. Then, the end voltage of the detection coil 20 changes. On the other hand, the impedance and the end voltage of the temperature compensation coil 21 do not change even when the steering shaft 1 rotates.

  These impedances are detected as voltages of the detection coil 20 and the temperature compensation coil 21 by the detection circuit shown in FIG. Since the difference between these voltages, that is, the amount of change in the end voltage of the detection coil 20 changes in proportion to the steering torque, the steering torque can be detected from the voltage change. Further, the change (increase or decrease) in the end voltage of the detection coil 20 corresponds to the steering direction of the steering shaft 1.

  The second cylinder 8 and the third cylinder 9 to which the temperature compensation coil 21 is electromagnetically coupled are fixed on the same axis (in this embodiment, the input shaft 2). Therefore, the impedance of the temperature compensation coil 21 changes only when the second and third cylinders 8 and 9 are deformed due to the influence of temperature or the like. Therefore, by taking the voltage difference between the detection coil 20 and the temperature compensation coil 21, it is possible to cancel out the voltage change due to the temperature change and to compensate the temperature of the output value (voltage) of the detection coil 20 that changes due to the steering torque. .

  When the steering shaft 1 (the input shaft 2 and the output shaft 3) is rotated, the third cylinder 9 is rotated relative to the fourth cylinder 10. Thereby, the area of the overlapping portion 18 of the second disk 12 changes (increases or decreases). When the area of the overlapping portion 18 changes, the impedance of the detection coil 22 changes. At this time, the impedance of the temperature compensation coil 21 does not change.

  These impedances are detected as voltages of the detection coil 22 and the temperature compensation coil 21 by the detection circuit shown in FIG. The difference between these voltages is a voltage corresponding to the steering angle, and a change (increase or decrease) in this voltage corresponds to the steering direction of the steering shaft 1. By taking the difference from the temperature compensation coil 21, the output value (voltage) of the detection coil 22 that varies depending on the steering angle can be temperature compensated as in the case of the steering torque.

  Here, since the through hole 17 of the second disk 12 is formed in a semicircular shape, it can cope with detection of a steering angle in a range of about ± 90 degrees. Here, the main cylinder (in this embodiment, the third cylinder 9) may be attached to the steering shaft 1 via a speed reduction mechanism or the like. In this way, the main cylinder (third cylinder 9) is rotated at a reduced speed with respect to the rotation of the steering shaft 1 at a predetermined ratio. Thereby, the through-hole 17 can respond | correspond to the detection of the steering angle of the range more than +/- 90 degree | times. However, in this case, since the third cylinder 9 rotates relative to the steering shaft 1 (the input shaft 2 or the output shaft 3), the cylinder fixed to the outer peripheral surface of the output shaft 2 for temperature compensation. It is necessary to arrange the body separately. This cylinder is electromagnetically coupled to the second cylinder 8 and the temperature compensation coil 21.

  Next, a steering device (power steering device) equipped with the torque sensor of the present embodiment will be described.

  FIG. 7 is a schematic diagram of a steering apparatus to which the torque sensor of FIG. 1 is attached.

  As shown in FIG. 7, the steering apparatus includes a steering wheel (steering) 28 attached to the input shaft 2 and a pinion gear 29 attached to the output shaft 3. The pinion gear 29 meshes with a rack gear portion 31 provided on a tie rod 30 extending in the lateral direction of the automobile. The tie rod 30 is connected to the wheels 34 via a drag link 32, a knuckle arm 33, and the like.

  When the steering wheel 28 is operated and the steering shaft 1 is rotated, this rotation is converted into a linear motion along the lateral direction of the vehicle by the pinion gear 29 and the rack gear portion 31 of the tie rod 30. This achieves wheel steering. At this time, the control unit 35 detects the steering torque (detection signal from the torque sensor) loaded on the steering shaft 1. The control unit 35 drives the electric motor (electric motor) 36 based on the detection signal (steering torque). The electric motor 36 rotates the steering shaft 1 via the speed reducer 37. Thereby, the force which steers the steering wheel 28 is assisted.

  If the driver releases the steering wheel 28 while the vehicle is traveling, it is necessary to return the wheel 34 to face the traveling direction of the vehicle. At this time, the control unit 35 detects the steering angle of the steering shaft 1 (detection signal from the steering angle sensor). The control unit 35 drives the electric motor (electric motor) 36 based on the detection signal (steering angle). The electric motor 36 rotates the steering shaft 1 via the speed reducer 37. Thereby, the wheel 34 is controlled to face the traveling direction of the automobile.

  Next, the operation of the present embodiment will be described.

  First and second discs 11 and 12 made of a non-magnetic material are mounted on the opposing surfaces of the cylinders 7, 8, 9 and 10. The side surfaces of the first and second disks 11 and 12 are provided with through-holes 13 formed at predetermined intervals in the circumferential direction or arc-shaped through-holes 17 formed along the circumferential direction. ing. The through holes 13 and 17 play the same role as the tooth surface of the cylinder described in the background art section. In the present embodiment, the steering torque and the steering angle are detected according to changes in the overlapping portions 14 and 18 of the through holes 13 and 17.

  In the present embodiment, through holes 13 and 17 are formed in the first and second discs 11 and 12 by punching, and the first and second discs 11 and 12 are formed into cylindrical tubes. It is mounted on the opposing surfaces of the bodies 7, 8, 9, and 10. With such a configuration, the machining time can be greatly reduced as compared with the case where the tooth surfaces are formed on the cylinders 7, 8, 9, and 10 by cutting. Further, since the first and second disks 11 and 12 are made of a non-magnetic material, it is not necessary to consider the magnetic characteristics, and the sensor characteristics can be easily adjusted.

  By adopting such a configuration, it is possible to easily manufacture the cylinders 7, 8, 9, and 10 (discs 11 and 12), reduce the manufacturing cost, and manufacture the torque sensor at a low cost. be able to.

  By the way, the metal material expands or contracts due to thermal deformation. Due to thermal deformation, the distance between the cylinders 7, 8, 9, 10 and the distance between the coils 20, 21, 22 (yoke 19) and the cylinders 7, 8, 9, 10 change, and the amount of magnetic flux changes. Therefore, an error due to temperature may occur. For this reason, in the present embodiment, the temperature compensation coil 21 and the temperature compensation coil 21 are electromagnetically coupled, and the second and third cylinders fixed on the same axis (in this embodiment, the input shaft 2). 8 and 9 for temperature compensation.

  Here, the third cylinder 9 may be fixed to the outer peripheral surface of the output shaft 3. In this case, the third cylindrical body 9 is provided to face the first cylindrical body 7 from the side opposite to the second cylindrical body 8, and the temperature compensation coil 21 is provided to the first and third cylindrical bodies 7, What is necessary is just to provide so that the outer peripheral surface of 9 (opposing surface of the 1st, 3rd cylinders 7 and 9) may be covered. In short, in order to perform temperature compensation, it is only necessary to have a pair of cylinders provided on the same axis (input shaft 2 or output shaft 3) and a coil for temperature compensation electromagnetically coupled to the pair of cylinders. .

  In the present embodiment, the temperature compensation coil 21 is commonly used for detection of steering torque and steering angle. By doing in this way, the torque sensor of this Embodiment can detect a steering torque and a steering angle with high precision, without being influenced by a temperature change.

  The torque sensor according to the present embodiment includes third and fourth cylinders 9 and 10 for detecting a steering angle, and a detection coil 22 that is electromagnetically coupled to the third and fourth cylinders 9 and 10. It has. According to this embodiment, the torque sensor and the steering angle sensor can be integrated, and the processing circuit unit of the torque sensor and the steering angle sensor can be made common. With this configuration, the torque sensor (steering angle sensor) can be manufactured at a lower cost than when the torque sensor and the steering angle sensor are manufactured separately, and the torque sensor (steering angle sensor) Miniaturization can be achieved.

  It should be noted that the torque sensor of the present embodiment can be applied to devices other than automobile steering devices.

  For example, the torque sensor according to the present embodiment can be mounted on a drive shaft of an automobile, an input shaft of a transmission, and an output shaft of the transmission. By attaching the torque sensor of the present embodiment to these shafts, the engine output can be reduced to the limit, so that energy can be used with high efficiency and fuel efficiency can be improved.

  Moreover, by mounting on an electric brake of an automobile and detecting the pressing torque of the brake pad, it is possible to improve the response performance of the brake and improve the stability of the vehicle body by brake control.

It is side surface sectional drawing of the torque sensor which concerns on one embodiment of this invention. It is a front view of a 1st disc. It is the front view which piled up two 1st discs in the axial direction. It is a front view of a 2nd disc. It is the front view which piled up two 2nd discs in the axial direction. It is the schematic which shows the detection circuit of the torque sensor of FIG. It is the schematic of the steering device with which the torque sensor of FIG. 1 was mounted | worn.

Explanation of symbols

1 Steering shaft 2 Input shaft 3 Output shaft 4 Torsion bar 7 First cylinder 8 Second cylinder 9 Third cylinder (main cylinder)
10 Fourth cylinder (sub cylinder)
DESCRIPTION OF SYMBOLS 11 1st disk 12 2nd disk 13 Through-hole 17 Through-hole 20 Detection coil (steering torque)
21 Temperature compensation coil 22 Detection coil (steering angle)

Claims (5)

A torque sensor attached to an input shaft and an output shaft connected via a torsion bar, wherein the first tube is made of a magnetic material fixed to the output shaft, and the first tube is connected to the input shaft. A second cylinder made of a magnetic body fixed to face the body, a third cylinder made of a magnetic body fixed to the input shaft so as to face the second cylinder, and each cylinder a disc made of a nonmagnetic material having a plurality of through holes are formed at predetermined intervals on opposed surfaces respectively mounted circumferentially of, the above-described first, second cylindrical body and a detection coil electromagnetically coupled, the A torque sensor comprising a temperature compensation coil that electromagnetically couples to the second and third cylinders . The torque sensor according to claim 1 , wherein the through hole is formed by punching.   A main cylinder made of a magnetic material fixed to the steering shaft, a secondary cylinder made of a magnetic material attached to the fixed side so as to face the main cylinder, and a mounting surface on each cylinder. And a disc made of a non-magnetic material in which a circular arc-shaped through hole having a predetermined length is formed along the circumferential direction, and a detection coil that electromagnetically couples with the main and sub cylinders. Steering angle sensor. The steering angle sensor according to claim 3 , wherein the through hole is formed by punching. The steering angle sensor according to claim 3 or 4 , wherein the through hole has a semicircular shape.

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