JP2006038768A - Torque detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque detector dispensing with enlargement of its diameter. <P>SOLUTION: This torque detector is equipped with first and second rotating bodies 4 and 5 coaxially connected by a connecting shaft 6, and detects torque based on a torsional angle of the connecting shaft 6 when torque is applied to the rotating body 4 or 5. This torque detector is equipped with a light emission means 1 provided on a peripheral surface of the rotating body 4 for outputting a light beam, a reflection means 3 provided on a peripheral surface of the second rotating body for reflecting the light beam outputted by the emission means 1 in a direction different from its incident direction, and a light reception means 2 provided on the peripheral surface of the rotating body 4 for receiving the light beam reflected by the reflection means 3 to output a signal corresponding to a position where the light beam is received. Torque detection is performed by parallelizing the signal outputted by the reception means 2 to the torsional angle. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is suitably used for an electric power steering device of a vehicle and the like, and includes a first rotating body and a second rotating body that are coaxially connected by a connecting shaft, and torque is applied to the first rotating body or the second rotating body. The present invention relates to a torque detection device that detects torque based on the twist angle of a connecting shaft.

  As a vehicle steering apparatus, there is an electric power steering apparatus that assists steering by driving an electric motor to reduce a burden on a driver. This includes an input shaft connected to a steering member (steering wheel, steering wheel), an output shaft connected to a steering wheel by a pinion, a rack, etc., and a connecting shaft that connects the input shaft and the output shaft. The torque detection device detects the steering torque applied to the input shaft based on the angle, and drives and controls the steering assist electric motor linked to the output shaft based on the detected steering torque value. Conventionally, a magnetic detection resolver that detects a rotational position using a coil, an optical encoder detection device that detects transmission of light, or the like is used as a torque detection device of such an electric power steering device.

Patent Document 1 includes two light shielding plates that are respectively connected to and overlapped at both ends of a torsion bar, and a light emitter and a light detector that are provided to face each other so as to sandwich the light shielding plate. There has been proposed a torque sensor (torque detection device) that detects the torque based on the amount of light transmitted through the overlapping portion, in which the areas of the overlapping portions of the respective holes change according to the torsion amount of the torsion bar.
JP-A-6-160208

In the conventional torque detection apparatus as described above, there is a problem that the diameter increases because the coil or the light shielding plate is provided.
The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a torque detection device that does not require an increase in diameter.

  A torque detection device according to a first aspect of the present invention includes a first rotating body and a second rotating body that are coaxially connected by a connecting shaft, and when torque is applied to the first rotating body or the second rotating body, In the torque detection device for detecting the torque based on the twist angle of the connecting shaft, provided on the peripheral surface of the first rotating body, provided on the peripheral surface of the second rotating body, and a light emitting means for outputting a light beam, Reflecting means for reflecting the light beam output from the light emitting means in a direction different from the incident direction, and the light beam reflected by the reflecting means provided on the peripheral surface of the first rotating body, and depending on the received position And a light receiving means for outputting the received signal, wherein the torque is detected by making the signal outputted by the light receiving means correspond to the twist angle.

  In the torque detector according to a second aspect of the present invention, the light receiving means is a light receiving element divided into two in the circumferential direction of the first rotating body, and the difference between the output signals of the divided light receiving elements is defined as the signal. It is comprised so that it may carry out.

  According to the torque detection device of the present invention, it is possible to realize a torque detection device that does not require an increase in diameter. In addition, since the detection is not based on the absolute light quantity, a structure for sealing light is unnecessary.

Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof.
(Embodiment 1)
1 and 2 are a front view (FIG. 1) and a plan view (FIG. 2) schematically showing the configuration of the first embodiment of the torque detection device according to the present invention. In this torque detector, an input shaft 4 (first rotating body) and an output shaft 5 (second rotating body) are coaxially connected by a small-diameter torsion bar 6 (connecting shaft).
On the peripheral surface of the input shaft 4, a light emitting element 1 (light emitting means) that is a light emitting diode or a laser diode that outputs a light beam parallel to the axis toward the output shaft 5 is provided. On the optical path of the light beam output from the light emitting element 1, a lens for focusing the light beam may be provided as necessary.

On the peripheral surface of the output shaft 5, a reflecting plate 3 (reflecting means) for reflecting the light beam output from the light emitting element 1 is provided with a slight angle θ inclined with respect to the incident direction of the light beam. The light beam reflected by the reflecting plate 3 is received by the light receiving element 2 (light receiving means) provided near the light emitting element 1 on the peripheral surface of the input shaft 4. The light receiving element 2 is composed of two photodiodes 2a and 2b divided in the circumferential direction of the input shaft 4, and the dividing line has no torque input to the input shaft 4 and the torsion bar 6 is not twisted. At this time, the reflected light beam from the reflecting plate 3 is positioned so as to be divided into two equal parts. Further, the light receiving surface is positioned so as to be perpendicular to the optical axis of the reflected light beam.
The light receiving element 2 outputs a difference voltage between the output voltages of the two photodiodes 2a and 2b as a detection signal.

  In the torque detection device having such a configuration, when a clockwise torque is input to the input shaft 4, the torsion bar 6 is twisted, and the reflection position of the light beam from the light emitting element 1 is on the reflector 3 in FIG. Shift left. Since the reflection plate 3 is inclined by a minute angle θ, when the reflection position is shifted to the left on the reflection plate 3, the reflection position is moved away from the light emitting element 1, and the reflection position is moved away. The position where the reflected light beam from the reflecting plate 3 is incident on the light receiving element 2 is shifted to the left. Therefore, the output voltages of the photodiodes 2a and 2b are higher in the photodiode 2a, and the difference between them becomes larger as the twist angle of the torsion bar 6 is larger.

  On the other hand, when a counterclockwise torque is input to the input shaft 4, the torsion bar 6 is twisted, and the reflection position of the light beam from the light emitting element 1 is shifted to the right on the reflector 3 in FIG. When the reflection position is shifted to the right on the reflection plate 3, the reflection position approaches the light emitting element 1 by the amount of the shift, and the reflected light beam from the reflection plate 3 is incident on the light receiving element 2. The position shifts to the right. Therefore, the output voltage of the photodiodes 2a and 2b is higher in the photodiode 2b, and the difference between them becomes larger as the twist angle of the torsion bar 6 is larger.

  From the above, the light receiving element 2 outputs a larger voltage signal as the twist angle of the torsion bar 6 is larger as shown in FIG. Moreover, since the twist angle of the torsion bar 6 corresponds to the input torque, the light receiving element 2 outputs a voltage corresponding to the input torque. Further, the clockwise / counterclockwise torque can be made to correspond to the positive / negative of the voltage. Therefore, the torque input to the input shaft 4 can be detected based on the output voltage of the light receiving element 2.

(Embodiment 2)
4 and 5 are a front view (FIG. 4) and a plan view (FIG. 5) schematically showing the configuration of the torque detection device according to the second embodiment of the present invention. In this torque detector, an input shaft 4 (first rotating body) and an output shaft 5 (second rotating body) are coaxially connected by a small-diameter torsion bar 6 (connecting shaft).
On the peripheral surface of the input shaft 4, there is provided a light emitting element 1 a that is a light emitting diode or a laser diode that outputs a light beam slightly inclined with respect to the axis toward the output shaft 5. On the optical path of the light beam output from the light emitting element 1a, a lens for focusing the light beam may be provided as necessary.

On the peripheral surface of the output shaft 5, a cylindrical or columnar reflecting mirror 3a that reflects the light beam output from the light emitting element 1a is provided. The light beam reflected by the reflecting mirror 3 a is received by the light receiving element 2 provided in the vicinity of the light emitting element 1 a on the peripheral surface of the input shaft 4. The light receiving element 2 is composed of two photodiodes 2a and 2b divided in the circumferential direction of the input shaft 4, and the dividing line has no torque input to the input shaft 4 and the torsion bar 6 is not twisted. Is positioned so that the reflected light from the reflecting mirror 3a is divided into two equal parts. Further, the light receiving surface is positioned so as to be perpendicular to the optical axis of the reflected light beam.
The light receiving element 2 outputs a difference voltage between the output voltages of the two photodiodes 2a and 2b as a detection signal.

  In the torque detector having such a configuration, when a clockwise torque is input to the input shaft 4, the torsion bar 6 is twisted, and the reflection position of the light beam from the light emitting element 1a is the same as that on the reflecting mirror 3a in FIG. Shift left. Since the reflection mirror 3a is a curved surface, if the twist angle is small, even if the reflection position shifts to the left on the reflection mirror 3a, the amount of the shift is so far away from the light emitting element 1 that the reflection position is 3 (FIG. 1). However, the incident angle and the reflection angle on the reflecting mirror 3a are increased, and the position where the reflected light beam is incident on the light receiving element 2 is shifted to the left by the increase. Therefore, the output voltages of the photodiodes 2a and 2b are higher in the photodiode 2a, and the difference between them becomes larger as the twist angle of the torsion bar 6 is larger.

  On the other hand, when a counterclockwise torque is input to the input shaft 4, the torsion bar 6 is twisted, and the reflection position of the light beam from the light emitting element 1a is shifted to the right on the reflecting mirror 3a in FIG. Since the reflection mirror 3a is a curved surface, if the twist angle is small, even if the reflection position is shifted to the right on the reflection mirror 3a, the reflection position is such that the reflection position moves away from the light emitting element 1a. 3 (FIG. 1). However, the incident angle and the reflection angle on the reflecting mirror 3a are decreased, and the position where the reflected light beam is incident on the light receiving element 2 is shifted to the right by the decrease. Therefore, the output voltage of the photodiodes 2a and 2b is higher in the photodiode 2b, and the difference between them becomes larger as the twist angle of the torsion bar 6 is larger.

From the above, the light receiving element 2 outputs a larger voltage signal as the twist angle of the torsion bar 6 is larger, as in the first embodiment. Moreover, since the twist angle of the torsion bar 6 corresponds to the input torque, the light receiving element 2 outputs a voltage corresponding to the input torque. Further, the clockwise / counterclockwise torque can be made to correspond to the positive / negative of the voltage. Therefore, the torque input to the input shaft 4 can be detected based on the output voltage of the light receiving element 2.
In the first and second embodiments described above, the light receiving element 2 is the two photodiodes 2a and 2b divided in the circumferential direction of the input shaft 4, but instead of these, a one-dimensional CCD (Charge Coupled Device) is used. ) Can also be used to detect the incident position of the reflected light.

FIG. 6 is a perspective view showing the configuration of the torque detection device disclosed this time. This torque detection device has a small-diameter torsion bar 6 (in this case, separated at an intermediate portion for explanation) provided in the space around each axis of the input shaft 4a and the output shaft 5a. 4a and the output shaft 5a are connected coaxially.
The input shaft 4a is sandwiched between a small-diameter surface and a large-diameter surface parallel to the outer peripheral surface, and has a built-in space 24 with an opening provided on an end surface facing the output shaft 5a. The output shaft 5a is formed on the outer peripheral surface. An opening is provided between the parallel small-diameter surface and large-diameter surface, an opening is provided on the end surface facing the input shaft 4 a, and a space 25 having a cross-sectional shape parallel to the end surface is the same as the space 24.

  The input shaft 4a and the output shaft 5a are made of grease or the like so that the openings of the spaces 24 and 25 are matched with each other, and when torque is input, the input shaft 4a and the output shaft 5a are slidably rotated in opposite directions. The spaces 24 and 25 are shut off from the outside in a state where the end faces to which the coating is applied are in contact with each other.

  A light emitting element 1 b that is a light emitting diode or a laser diode that outputs a light beam parallel to the axis toward the direction of the space 25 is provided on the inner peripheral surface of the space 24. On the optical path of the light beam output from the light emitting element 1b, a lens for focusing the light beam may be provided as necessary.

On the inner peripheral surface of the space 25, a reflection plate 3b that reflects the light beam output from the light emitting element 1b is provided at a slight angle with respect to the incident direction of the light beam. The light beam reflected by the reflecting plate 3 b is received by the light receiving element 2 e provided in the vicinity of the light emitting element 1 b on the inner peripheral surface of the space 24. The light receiving element 2e is composed of two photodiodes 2c and 2d divided in the circumferential direction of the input shaft 4a, and the dividing line has no torque input to the input shaft 4a and the torsion bar 6 is not twisted. Is positioned so as to divide the reflected light from the reflecting plate 3b into two equal parts. Further, the light receiving surface is positioned so as to be perpendicular to the optical axis of the reflected light beam.
The light receiving element 2e outputs a difference voltage between the output voltages of the two photodiodes 2c and 2d as a detection signal.

  In the torque detection device having such a configuration, since it is housed in the spaces 24 and 25 and is blocked from the outside, the dust does not enter from the outside, the light beam is blocked by the dust, attenuates, and cannot be detected accurately. Therefore, torque can be detected stably. Since other operations are the same as those of the torque detection device of the first embodiment described above, description thereof is omitted.

It is a front view which shows typically the structure of embodiment of the torque detection apparatus which concerns on this invention. It is a top view which shows typically the structure of embodiment of the torque detection apparatus which concerns on this invention. It is a characteristic view which shows the operating characteristic of the torque detection apparatus shown in FIGS. It is a front view showing typically composition of an embodiment of a torque detector concerning the present invention. It is a top view which shows typically the structure of embodiment of the torque detection apparatus which concerns on this invention. It is a perspective view which shows the structure of the torque detection apparatus disclosed this time.

Explanation of symbols

1 Light emitting element (light emitting means)
2 Light receiving element (light receiving means)
2a, 2b Photodiode 3 Reflector (reflecting means)
3a Reflector (reflecting means)
4 Input shaft (first rotating body)
5 Output shaft (second rotating body)
6 Torsion bar (connection shaft)

Claims (2)

A first rotating body and a second rotating body connected coaxially by a connecting shaft, and when torque is applied to the first rotating body or the second rotating body, the torque is based on a twist angle of the connecting shaft; In the torque detection device for detecting
A light emitting means that is provided on the peripheral surface of the first rotating body and outputs a light beam, and a reflection that is provided on the peripheral surface of the second rotating body and reflects the light beam output from the light emitting means in a direction different from the incident direction. And a light receiving means that is provided on the peripheral surface of the first rotating body, receives the light reflected by the reflecting means, and outputs a signal corresponding to the received position, and the signal output by the light receiving means Is configured to detect the torque in correspondence with the torsion angle.   2. The light receiving means is a light receiving element that is divided into two in the circumferential direction of the first rotating body, and is configured to use a difference between output signals of the divided light receiving elements as the signal. The torque detection apparatus as described.

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