JPH08133105A - Power steering device - Google Patents

Abstract

PURPOSE: To provide a power steering device equipped with a torque sensor which can detect change in torque with high sensitivity. CONSTITUTION: This device is made up of an input shaft 1 that rotates due to the rotation of a handle; an output shaft connected to the input shaft 1 through a torsion bar so as to be able to conduct relative rotation; inside sensor rings 15 that are fitted to the input shaft 1 and form rectangular tooth portions 16 at a fixed pitch; outside sensor rings 25 that are furnished to the output shaft and form at a fixed pitch tooth portions 26 inclined in regard to the rotary direction of the output shaft; and detection coils 73 to detect the change of the overlap surface of the outside sensor ring tooth portions and the inside sensor ring tooth portions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering system equipped with a torque sensor for highly sensitively detecting a torque acting between an input shaft connected to a steering wheel and an output shaft connected to a steering mechanism.

[0002]

2. Description of the Related Art An electric power steering device is being developed as a power steering device for assisting a force for operating a steering wheel of an automobile. This has a structure in which the torque applied to the steered wheels is detected and the motor provided in the steering mechanism is rotated according to the detected torque. As a power steering device of this type, FIG.
There are the following. FIG. 8 is a half-cut sectional view showing a torque sensor portion of a conventional power steering apparatus. An input shaft 1 connected to a steering wheel and an output shaft (not shown) connected to a pinion of a steering mechanism are connected via a torsion bar TB. End portions of the inner sensor ring 55 fitted to the input shaft 1 at a constant pitch, and end portions of the outer sensor ring 65 fitted to the output shaft. The change in the overlapping portion (overlap surface L '(see FIG. 9)) of the rectangular tooth portions 66 formed at a constant pitch in the portion is detected as a change in the inductance of the detection coil 73, and the torsion bar TB is detected.
Is detected as the rotational torque acting between the input shaft 1 and the output shaft. That is, as shown in FIG. 9, the tooth portion 56 of the inner sensor ring 55 and the outer sensor ring 65 tooth portion 66 when the handle is neutral (when no rotational torque acts between the input shaft 1 and the output shaft).
With reference to the overlap plane L'0 of
[B]), when the handle is rotated to the left (Fig. 9).
[A]), the overlapping surface of the tooth portion 56 and the tooth portion 66 increases to L′ 1, so the output voltage induced in the detection coil 73 increases, and conversely, when the handle is rotated to the right (FIG. 9 [C]), the overlapping surface of the tooth portion 56 and the tooth portion 66 is reduced to L'2, and thus the output voltage induced in the detection coil 73 is reduced. The rotational torque generated between the input shaft 1 and the output shaft is detected based on the amount of change in the induced output voltage.

[0003]

By the way, since the torsion amount of the torsion bar TB when the rotational torque acts between the input shaft 1 and the output shaft by steering is very small,
The tooth portion 5 in the torque sensor portion of the power steering apparatus described above.
6 and the tooth portion 66 have a slight change in the overlapping surface L, and the tooth portion 56 and the tooth portion 66 change in accordance with the change in the rotational torque.
The rate of change of the area of the overlapping surface L ′ (area change rate), that is, the rate of change of the inductance of the detection coil 73 is small. Therefore, there is a problem that the sensitivity to changes in the rotational torque acting between the input shaft 1 and the output shaft is low and the steering force cannot be properly assisted.

In order to solve the above problems, it is an object of the present invention to provide a power steering system equipped with a torque sensor capable of detecting a change in torque with high sensitivity.

[0005]

The structure of the invention for solving the above-mentioned problems is such that an input shaft for transmitting rotation from a handle is connected to the input shaft so as to be relatively rotatable via a torsion bar. The output shaft, a first sensor ring that is a magnetic cylindrical member that is fitted and fixed to the input shaft, and has tooth portions with a constant pitch formed at the ends, and a magnetic member that is fitted and fixed to the output shaft. A second member, which is a member and has teeth with a constant pitch formed at positions overlapping the teeth of the first sensor ring.
The sensor ring is provided on the outer periphery of the overlapping portion of the tooth portion of the first sensor ring and the tooth portion of the second sensor ring, and the tooth portion of the first sensor ring and the tooth of the second sensor ring are provided. A detection coil that detects a change in the overlapping surface of the portion as a change in inductance, and a rotational torque that acts between the input shaft and the output shaft according to an output voltage that changes due to a change in the inductance of the detection coil. In the power steering apparatus for detecting, the tip end portion of the tooth portion of at least one of the first sensor ring and the second sensor ring is inclined with respect to the rotation direction of the input shaft.

[0006]

When the handle is rotated to rotate the input shaft, the torsion bar is twisted according to the rotational torque, and the first sensor ring fixed to the input shaft is relative to the second sensor ring fixed to the output shaft. Rotate to. With this rotation,
The area of the overlapping surface of the tooth portion of the first sensor ring and the tooth portion of the second sensor ring changes. At this time, since the tip of at least one tooth portion of the first sensor ring or the second sensor ring is inclined with respect to the rotation direction of the input shaft, the area of the overlapping surface changes greatly. As a result, since the rate of change in the inductance of the detection coil changes significantly, the rotational torque that acts between the input shaft and the output shaft can be detected with high sensitivity.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical cross-sectional view showing a connecting portion 3 of an input shaft 1 and an output shaft 2 of a power steering apparatus according to this embodiment, and FIG. 2 is an enlarged half-cut sectional view of a torque sensor portion 72 of the connecting portion 3. . The right end of the input shaft 1 is connected to a handle (not shown) so as to rotate integrally with the handle. The input shaft 1 is composed of a hollow shaft 10, which is rotatably supported by a housing G fixed to the vehicle body at the rightward portion, and a flange portion 12 is formed at the leftward portion. As shown in FIG. 3, a large number of substantially L-shaped tooth portions 11 are formed at the tip of the flange portion 12. Further, a torsion bar TB that constitutes a connecting portion 3 is inserted in a hollow portion at the center of the input shaft 1, and is integrally connected to the input shaft 1 by a pin at the right end.

The output shaft 2 is a member 2 having a substantially T-shaped cross section.
No. 0, the small diameter portion 22 is rotatably supported by the housing G, the other end of the torsion bar TB is spline-engaged with the right end, and the torsion bar TB is twisted to be rotatable relative to the input shaft 1. It has become. The left end of the output shaft 2 is connected to a pinion (not shown) of the steering mechanism. On the outer periphery of the right end of the large diameter portion 23, as shown in FIG.
Character-shaped tooth portions 21 are formed, are respectively inserted in the valleys of the tooth portions 11 formed on the above-mentioned input shaft 1, and the tooth portions 11 and 21 are opposed to each other in the circumferential direction with a constant gap, When a torque larger than the torsional reaction force of the torsion bar TB acts between the input shaft 1 and the output shaft 2, the tooth portions 11, 21
Are configured so that the side surfaces thereof contact. Further, a gear 32 of a reduction mechanism that decelerates and transmits power from a motor (not shown) that assists the steering force is key-engaged with the outer periphery of the small diameter portion 22.

Next, the structure of the torque sensor portion 72, which is a feature of the present invention, will be described with reference to FIG. Torque sensor 72
Is mainly the inner sensor ring 15 and the outer sensor ring 25.
And a detection coil 73. As shown in the perspective view of FIG. 4, the inner sensor ring 15 is a cylindrical magnetic body member, and a large number of rectangular tooth portions 16 are formed on the left end portion thereof at a constant pitch. The inner sensor ring 15 is fitted and fixed to the input shaft 1 through the non-magnetic magnetic shield spacer 74 at the center of the input shaft 1 in the axial direction, and is rotated integrally with the input shaft 1. .

As shown in the perspective view of FIG. 5, the outer sensor ring 25 is a cylindrical magnetic member having a large number of teeth 26 formed at the right end thereof at a constant pitch. The tooth portion 26 is formed such that the tip portion 26 a is inclined with respect to the circumferential direction of the output shaft 2. And this outer sensor ring 2
5 is fitted and fixed to the tip of the tooth portion 21 of the output shaft 2 so as to rotate integrally with the output shaft 2.

The inner sensor ring 15 and the outer sensor ring 25 described above are positioned so that the tooth portions 16 and 26 are opposed to each other, and the handle is in a neutral state (when no torque acts on the input shaft 1 and the output shaft 2). As shown in FIG. 6B, the tooth portion 16 and the tooth portion 26 are located at positions displaced with respect to the rotation direction of the input shaft 1. Further, the detection coil 73 is fixed in the housing G, which supports the input shaft 1, by a sensor guide 75 and a sensor spacer 76, and the tooth portion 16 and the tooth portion 26.
Is wound and inserted in a ring shape at a position opposed to. The sensor guide 75 and the sensor spacer 76 are both made of a magnetic material. The sensor guide 75 guides the inner sensor ring 15, the sensor spacer 26 guides the outer sensor ring 26, and the sensor guide 75, the sensor spacer 76, and the inner side. The sensor ring 15, the outer sensor ring 25, and the overlapping portion (overlap surface L) of the tooth portion 16 and the tooth portion 26 form a magnetic path R through which the magnetic flux generated by the detection coil 73 passes. Further, an oscillator (not shown) is connected to the detection coil 73, and the magnetic flux generated by the oscillating operation of the oscillator flows through the magnetic path R to induce a voltage, and the area of the overlap plane L changes. By doing so, the inductance of the detection coil 73 changes and the induced voltage is increased or decreased. That is, the area of the overlapping surface L between the tooth portion 16 and the tooth portion 26 (see FIG. 6) is obtained by changing the rotational torque applied to the torsion bar TB by the detecting coil 73, and changing the twist amount accordingly. Is detected based on the change of.

The operation of the power steering apparatus having the above configuration will be described with reference to FIG. First, when the handle is neutral,
The teeth 15 and 16 are located at the position [B], and the area of the overlapping surface at this time is L0.
When the handle is turned to the left, the input shaft 1 is rotated to the left,
As a result, the torsion bar TB is twisted to the left. Then, as shown in FIG. 6A, since the inner sensor ring 15 fixed to the input shaft 1 rotates relative to the outer sensor ring 26 fixed to the output shaft 2, the tooth portion 16 and the tooth portion 26. The area is increased to L1 on the overlapping surface, and the change is detected by the detection coil 73, and the rotational torque at that time is detected. Conversely, when the handle is turned to the right, the input shaft 1 is rotated to the right, which causes the torsion bar TB to be twisted to the right. Then, as shown in FIG. 6C, the inner sensor ring 15 fixed to the input shaft 1 relatively rotates with respect to the outer sensor ring 26 fixed to the output shaft 2, and thus the tooth portion 16 and the tooth portion 26. The area of the overlapping surface is reduced to L2, and the change is detected by the detection coil 73, and the rotational torque at that time is detected.

In the power steering apparatus of this embodiment having the above-described operation, the area change of the overlap surface L'of the conventional power steering apparatus changes only in the rotation direction of the input shaft 1 (Fig. 9), since the tip end portion 26a of the tooth portion 26 of the outer sensor ring 25 is inclined in the rotation direction of the input shaft 1, the change in the area of the overlapping surface L is different between the rotation axis direction and the rotation direction of the input shaft 1. Since it changes to both, the rate of area change (area change rate) of the overlapping surface L can be increased (see FIG. 6).
Since the change rate of the inductance of the detection coil 73 can be increased, the torque can be detected with high sensitivity.

In the power steering apparatus of this embodiment, the tip end 26a of the tooth portion 26 of the outer sensor ring 25 is set in the rotational direction of the output shaft 2 in order to increase the area change rate of the overlapping surface. Is tilted, but on the contrary,
The tip of the tooth portion 16 of the inner sensor ring 15 may be inclined with respect to the rotation direction of the input shaft 1, and the shape of the tooth portion 16 of the outer sensor ring 25 may be rectangular. Further, as shown in FIG. 7, the shape of the tooth portion 16 of the inner sensor ring 15 may be inclined with respect to the rotation direction of the input shaft 1 similarly to the shape of the tooth portion 26 of the outer sensor ring 25.

Further, in the power steering apparatus of this embodiment, the assisting of the steering force is performed by the motor,
If the power steering apparatus detects the rotational torque acting between the input shaft 1 and the output shaft 2, the steering force may be assisted electrically by a motor or hydraulically by a cylinder or the like.

[0016]

As described above, in the power steering apparatus of the present invention, the tip of at least one tooth portion of the first sensor ring or the second sensor ring is inclined with respect to the rotation direction of the input shaft. Therefore, since the rate of change of the area of the overlapping surface is large, the rate of change of the inductance of the detection coil can be increased, and the torque can be detected with high sensitivity.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a power steering apparatus showing an embodiment of the present invention.

FIG. 2 is an enlarged half-cut sectional view showing a torque sensor of the power steering apparatus according to the embodiment of the present invention.

FIG. 3 is a perspective view showing a flange portion of an input shaft and a large diameter portion of an output shaft.

FIG. 4 is a perspective view showing an inner sensor ring.

FIG. 5 is a perspective view showing an outer sensor ring.

FIG. 6 is an explanatory view showing the operation of the embodiment of the present invention.

FIG. 7 is an explanatory view showing another embodiment of the present invention.

FIG. 8 is a half-cut sectional view showing a torque sensor of a conventional power steering apparatus.

FIG. 9 is an explanatory diagram showing an operation of the conventional power steering apparatus.

[Explanation of symbols]

 1 Input Shaft 2 Output Shaft 15 Inner Sensor Ring (First Sensor Ring) 16, 26 Teeth 25 Outer Sensor Ring (Second Sensor Ring) 26a Tip 72 Torque Sensor 73 Detection Coil L0, L1, L2 Overlap Surface TB Torsion bar

Claims (1)

[Claims] 1. An input shaft for transmitting rotation from a handle, an output shaft connected to the input shaft for relative rotation via a torsion bar, and a magnetic cylindrical member fitted and fixed to the input shaft. And a first sensor ring having a tooth portion with a constant pitch formed at an end thereof, and a magnetic member fitted and fixed to the output shaft, and fixed at a position overlapping the tooth portion of the first sensor ring. The tooth portion of the first sensor ring is provided on the outer periphery of a second sensor ring having a tooth portion of a pitch, the tooth portion of the first sensor ring and the tooth portion of the second sensor ring that overlap each other. And a detection coil that detects a change in the overlapping surface of the tooth portion of the second sensor ring as a change in inductance, and the input according to an output voltage that changes according to a change in the inductance of the detection coil. In a power steering apparatus that detects a rotational torque that acts between a shaft and the output shaft, a tip portion of the tooth portion of at least one of the first sensor ring and the second sensor ring is arranged in a rotation direction of the input shaft. A power steering device characterized by being tilted with respect to one another.