JP2002173035A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device capable of securing sufficient collapse stroke while maintaining mountability on a vehicle. SOLUTION: Since a seal member 19 and a lower column tube 101c are arranged inside of a radius direction of coils 150A, 150B, it is not necessary to arrange a connection part of the seal member 119 or the lower column tube 101c and a housing main body 101a in an axial direction of the coils 150A, 150B. Accordingly, sufficient collapse stroke can be secured in a compact structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus, and more particularly to an electric power steering apparatus capable of detecting steering torque with high accuracy to perform steering control.

[0002]

2. Description of the Related Art In an electric power steering apparatus mounted on a vehicle, a torque sensor is provided to detect a steering torque for use in driving control of a motor.

FIG. 8 shows an example of such a conventional electric power steering apparatus. In the electric power steering apparatus of FIG. 8, the input shaft 2 disposed coaxially
And an output shaft 3 are connected via a torsion bar 4 and a cylindrical member 10 made of a conductive and non-magnetic material.
Are integrated with the input shaft 2 in the rotation direction so as to surround the outer peripheral surface of the output shaft 3, and at least a portion of the output shaft 3 surrounded by the cylindrical member 10 is provided with a groove ( (Not shown), and a window (not shown) is formed in the cylindrical member 10 so that the degree of overlap with the groove changes according to the relative rotation position between the cylindrical member 10 and the output shaft 3. The coils 20A and 20A surround the portion where the window is formed.
B is provided. According to such an electric power steering device, the self-inductance of the coils 20A and 20B and the mutual inductance of the Using the change in inductance, the torsion of the torsion bar 4, that is, the steering torque can be detected from the induced electromotive force generated in the coils 20A and 20B, thereby providing a lightweight and compact configuration.

[0004]

By the way, in such a conventional electric power steering apparatus,
The coils 20A and 20B, the sealing member 5 for sealing between the housing 1 and the input shaft 2, and the joint between the housing 1 and the lower column tube 1A need to be directly arranged in the axial direction. The steering wheel (right side in the figure) side end protrudes, and its end face,
Upper column tube 1B with bracket 6 attached
There is a problem that the gap with the end face, that is, the collapse stroke S is further reduced. Collapse stroke S
Since the steering system is required to have a predetermined length in order to absorb the impact due to the contraction of the steering system during a vehicle collision,
If this is to be ensured by the prior art, there arises a problem that the overall length of the electric power steering device becomes longer and the mountability of the vehicle deteriorates.

According to the present invention, while maintaining the mountability of a vehicle,
An object of the present invention is to provide an electric power steering device capable of securing a sufficient collapse stroke.

[0006]

To achieve the above object, an electric power steering apparatus according to the present invention comprises a housing, an input shaft for inputting a steering force, an electric motor for generating a rotational force, and a steering mechanism. An output shaft connected to the torsion bar connecting between the input shaft and the output shaft,
A detection device for detecting the amount of twist of the torsion bar,
A power transmission mechanism for transmitting the rotational force from the electric motor to the output shaft, wherein the detection device is provided on one of the input shaft and the output shaft, and is formed of a magnetic material. A sensor member having a hole or notch communicating with the periphery, a cylindrical member provided on the other of the input shaft and the output shaft, and extending so as to surround at least a part of the sensor member; A coil member for detecting an amount of twisting of the torsion bar based on an overlapping state of the notch and the cylindrical member, wherein at least one of a seal member and a column tube is disposed radially inside the coil member; It is characterized by the following.

[0007]

The electric power steering apparatus according to the present invention includes a housing, an input shaft for inputting a steering force, an electric motor for generating a rotational force, an output shaft connected to a steering mechanism, the input shaft and the output. A torsion bar connecting between the shaft and a torsion bar, a detection device for detecting a twist amount of the torsion bar, and a power transmission mechanism for transmitting the rotational force from the electric motor to the output shaft; A sensor member provided on one of the input shaft and the output shaft, formed of a magnetic material, and having a hole or notch communicating the inner and outer circumferences, and provided on the other of the input shaft and the output shaft. Detecting a torsion amount of the torsion bar based on a cylindrical member extending so as to surround at least a part of the sensor member, and an overlapping state of the hole or notch and the cylindrical member. And at least one of a seal member and a column tube is disposed radially inward of the coil member, so that a joint between the seal member and the column tube and the housing is formed by the coil member. There is no need to arrange in the axial direction,
Therefore, a sufficient collapse stroke can be ensured with a compact configuration. When the column tube is arranged inside the coil member in the radial direction, it is sufficient that a part (for example, an end) of the column tube is arranged.

Further, the housing made of a conductive material or a conductive member separate from the housing is disposed radially inward of the coil member, and the seal member is attached to the conductive member. Preferably, the space between the inner peripheral surface and the outer peripheral surface of the input shaft is sealed.

Further, on the radially inner side of the coil member,
Preferably, the column tube is fitted to the housing made of a conductive material.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing an electric power steering apparatus 100 according to a first embodiment, cut along an axis of an input shaft.

In FIG. 1, a main body 101a and a lid member 10 are provided.
1b is attached to a vehicle body (not shown) by a bracket 6A.
The lower column tube 101c that is joined to the upper column tube 101 is telescopically fitted to an upper column tube 101d attached to a vehicle body (not shown) by a bracket 6B.

An input shaft 102 extends in the column tubes 101c and 101d, and an output shaft 10 extends in the housing 101.
3 extend. The right end of the input shaft 102 in the figure is connected to a steering shaft 102A, and the steering shaft 102A is further connected to a steering wheel (not shown). Steering shaft 102A
Is rotatably supported by the bearing 104 with respect to the upper column tube 101d. Output shaft 103 at left end
A torsion bar 105 whose right end is connected to the input shaft 102 by press fitting extends in the hollow output shaft 103. The left end of the output shaft 103 is similarly connected to a rack and pinion steering device (not shown) via a joint and an intermediate shaft (not shown). The output shaft 103
Is rotatably supported on the lid member 101b by bearings 114 and 115.

A detecting device for detecting a steering torque, that is, a torque sensor 106 is provided around the left end of the input shaft 102 based on the fact that the torsion bar 105 is twisted in proportion to the received torque. The torque sensor 106 described in detail below is a non-contact torque sensor,
A relative angular displacement between the input shaft 102 and the output shaft 103 based on the torsion of the torsion bar 105 is detected by a coil as a change in impedance in a predetermined magnetic circuit,
This is output to a control circuit (not shown) as an electric signal.

A worm wheel 113 is fixedly mounted around the center of the output shaft 103 by press fitting or the like. The worm wheel 113 meshes with a worm 130a connected to a rotating shaft 130 of an electric motor (not shown). The electric motor is connected to a control circuit (not shown). The control circuit inputs information such as the output of the torque sensor 106 and the vehicle speed, supplies predetermined electric power to the electric motor, and supplies an appropriate auxiliary torque. Is generated.

FIG. 2 shows a part of the input shaft 102 and the output shaft 10.
3 is an exploded perspective view showing the device 3 including the surrounding parts. As shown in FIG. 2, the input shaft 102 of the output shaft 103
A flange portion 103a is formed on the outer peripheral surface of the portion close to. The flanged cylindrical member 120 is arranged so as to abut the flange portion 103a.

On the other hand, a sensor member 130 is arranged on the outer periphery of the end of the input shaft 102 in a manner described later. The sensor member 130 made of a magnetic material includes a disc portion 131 and a disc portion 13.
1 has a plurality of pillar portions 132 formed at equal intervals on the outer periphery and extending in the axial direction. In the present embodiment, a recess is formed between adjacent pillar portions 132. Disk part 1
Four notches 131b are formed in the 31 opening 131a.

FIG. 3 is a view for explaining a method of assembling the sensor member 130 to the input shaft 102. The state shown in FIG.
02, and 4 formed at the end of the input shaft 102.
The two positioning protrusions 102a are passed through the opening 131a of the sensor member 130, and are positioned so as to engage with the notches 131b (see FIG. 3B). Further, the positioning member 102a protruding from the disk portion 131a is bent toward the surface of the disk portion 131a and caulked (see FIG. 3C), so that the sensor member 130 is connected to the input shaft 102.
Are mounted in a state where positioning is performed in the radial direction and the rotation direction. Sensor member 1
Preferably, 30 is formed from ferrite or martensite (ie, magnetic) stainless steel. In the assembled state, the thin cylindrical member 120 is provided so as to surround the sensor member 130.

Returning to FIG. 2, a cylindrical member 120 formed by press-forming a thin plate of a conductive and non-magnetic material (for example, aluminum) has a cylindrical portion 121.
And a flange portion 122. Flange part 12
2 has four openings 12a which are bent and protrude in the axial direction from the inner peripheral edge of the opening 122a.
2b are formed at equal intervals. In the assembled state,
The protrusion 122b is provided on the flange 103a of the output shaft 103.
The cylindrical member 120 is positioned with respect to the output shaft 103 in the radial direction and the rotation direction. The cylindrical member 120 may be attached to the output shaft 103 or the worm wheel 113 by screwing, or may be formed integrally with the output shaft 103 or the worm wheel 113.

The cylindrical portion 121 of the cylindrical member 120 has rectangular windows 121a and 121b arranged at equal intervals in the circumferential direction.
Is formed. Windows 121a, 12 arranged in multiple rows
1b is 180 degrees out of phase with each other, is maintained in a state close to the pillar portion 132 of the sensor member 130 in the assembled state, and has no relative rotation between the input shaft 102 and the output shaft 103. (Steering torque is zero)
Then, the center in the width direction of each pillar 132 and the window 121a
Are positioned so that the phase with the center in the width direction is 90 degrees, and the center in the width direction of the space of the adjacent pillar portion 132 and the window 121
b is positioned such that the phase with the center in the width direction is 90 degrees in the opposite direction.

A male stopper 103c is formed at an end of the output shaft 103 on the input shaft 102 side. The male stopper 103c is a cross-shaped shaft having four protrusions whose outer peripheral surface protrudes radially outward.

A female stopper 102b is formed at the end of the input shaft 102 in correspondence with the male stopper 103c. The female stopper 102b is a cross-shaped hole having four concave portions whose inner peripheral surface is concave inward in the radial direction, and the circumferential width of each concave portion is slightly larger than the circumferential width of the convex portion of the male stopper 103c. As a result, the relative rotation between the input shaft 102 and the output shaft 103 is restricted to a predetermined angle range (about ± 5 degrees).

Returning to FIG. 1, the main body 1 of the housing 101 will be described.
01a, the coils 150A, 1 of the same standard are surrounded so as to surround the cylindrical portion 121 (FIG. 2) of the cylindrical member 120.
A yoke 150 made of a magnetic material that supports the bobbin around which 50B is wound on the inner peripheral side is fixed. However, the coils 150A and 150B are coaxial with the cylindrical member 120, and one coil 150A surrounds a portion of the cylindrical member 120 where the window 121a is formed, and the other coil 150A
OB surrounds the portion of the cylindrical member 120 where the window 121b is formed.

In this embodiment, the torque sensor 1
Reference numeral 06 includes a sensor member 130, a cylindrical member 120, and coils 150A and 150B as coil members.

The inner cylindrical portion 101e of the main body 101a of the housing 101 extends axially inward from the right end of the main body 101a, and is located radially inward of the sensor member 130 when assembled. The input shaft 102 is located radially outward. A mounting bracket 1 is provided on the left end of the lower column tube 101c in the drawing.
01g is welded and fastened to the main body 101a using the bolt 101h, so that the lower column tube 101c is joined to the right end side opening of the inner cylindrical portion 101e. On the inner periphery of the free end of the inner cylindrical portion 101e,
Seal member 119 for sealing between the input shaft 102 and the outer periphery
Is attached.

The ends of the coils 150A and 150B are connected to a board 151 housed in a sensor case 101f formed in the main body 101a, and a motor control circuit (not shown) is formed on the board 151. I have. Since the specific configuration of the motor control circuit is not the gist of the present invention, it will not be described in detail.
As disclosed in Japanese Patent No. 0492, an oscillating unit for supplying an alternating current of a predetermined frequency to the coils 150A and 150B,
A first rectifying and smoothing circuit for rectifying and smoothing the self-induced electromotive force of the coil 150A and outputting the same, a second rectifying and smoothing circuit for rectifying and smoothing the self-induced electromotive force of the coil 150B and outputting the same, and first and second rectifiers A differential amplifier that amplifies and outputs a difference between outputs of the smoothing circuit, a noise removal filter that removes high-frequency noise from the output of the differential amplifier, and a relative position between the input shaft 102 and the cylindrical member 120 based on the output of the noise removal filter. A torque calculation unit that calculates the direction and magnitude of the rotational displacement and multiplies the result by, for example, a predetermined proportional constant to obtain a steering torque generated in the steering system; and reduces the steering torque based on the calculation result of the torque calculation unit. And an electric motor (not shown) that supplies a driving current that generates a steering assist torque.

Next, the operation of this embodiment will be described.
Now, assuming that the steering system is in a straight running state and the steering torque is zero, no relative rotation occurs between the input shaft 102 and the output shaft 103. Therefore, the input shaft 102 and the cylindrical member 12
No relative rotation occurs between zero.

On the other hand, when a steering wheel (not shown) is steered to generate a torque on the input shaft 102, the torque is transmitted to the output shaft 103 via the torsion bar 104. At this time, a frictional force is generated on the output shaft 103 according to the frictional force between the steered wheels and the road surface and the frictional force such as the meshing of the gears of the rack and pinion type steering device. The relative rotation that the output shaft 103 is delayed due to the torsion bar 105 being twisted, and the cylindrical member 120 and the output shaft 1
Relative rotation also occurs between 03. The direction and amount of the relative rotation are determined according to the steering direction of the steering wheel and the generated steering torque.

Here, the cylindrical member 120 and the input shaft 102
When relative rotation occurs, the degree of overlap between the pillar 132 of the sensor member 130 and the windows 121a and 121b of the cylindrical member 120 changes from the initial state.

As a result, the input shaft 102 and the cylindrical member 12
Since the self-inductance of the coil 150A and the self-inductance of the coil 150B change in opposite directions according to the relative rotation between 0,
The self-induced electromotive forces of A and 150B also change in opposite directions. Therefore, when the difference between the self-induced electromotive forces of the coils 150A and 150B is obtained, the difference is linear according to the direction and the magnitude of the steering torque (sinusoidal change when viewed macroscopically, but substantially linear in the range of use). Will change. On the other hand, a change in self-inductance due to temperature or the like is canceled in the differential amplifier in the motor control circuit.

Further, a torque calculation section in the motor control circuit determines a steering torque based on the output of the differential amplifier, and a motor drive section outputs a drive current corresponding to the direction and magnitude of the steering torque (not shown). Supply to electric motor. Then
The electric motor generates a rotational force corresponding to the direction and magnitude of the steering torque generated in the steering system, and the rotational force is transmitted to the output shaft 103 via the worm 130a and the worm wheel 113. Since the steering assist torque is applied to the output shaft 103, the burden on the driver is reduced.

According to the present embodiment, the most output shaft 103 radially inside the cylindrical member 120 and the sensor member 130
Since the seal 119 is disposed on the side, the configuration of the electric power steering apparatus 100 can be made compact, and thereby the collapse stroke S can be secured long.

Here, if a magnetic material such as the input shaft 102 exists inside the coils 150A and 150B in the radial direction, the magnetic field is disturbed by the whirling of the input shaft 102 and the deterioration with time due to rust on the shaft surface. As a result, the self-inductance generated in the coils 150A and 150B becomes inappropriate, and there is a possibility that the torque cannot be accurately detected. Therefore, in the present embodiment, the coil 15
0A and 150B in the radial direction and the sensor member 1
Since the inner cylindrical portion 101e of the housing 101, which is a conductive member, is interposed on the inner side in the radial direction of the cylindrical member 30 and the cylindrical member 120 and on the outer side in the radial direction of the input shaft 102, the inner cylindrical portion 101e is formed by the so-called skin effect. Thus, the influence of the input shaft 102 can be eliminated as much as possible, and stable and accurate torque detection can be performed. The outer peripheral surface of the inner cylindrical portion 101e and the coil 150
Since the magnetic flux can be concentrated between the inner peripheral surfaces of A and 150B by the skin effect and the magnetic field can be strengthened, the spontaneous magnetization of the sensor member 130 can be increased, and the detection sensitivity can be improved.

It is also conceivable that the sensor member is formed as a separate member and fitted around the input shaft or the output shaft.
In such a case, since the groove bottom becomes the shaft surface, the magnetic field may be disturbed as described above, and accurate detection may not be possible. Further, when the shaft surface is rusted, there is a possibility that the detection sensitivity is reduced. However, according to the present embodiment, the non-magnetic housing 101 is provided radially inside the coils 150A and 150B, radially inside the sensor member 130 and the cylindrical member 120, and radially outside the input shaft 102. This problem can be avoided because the inner cylindrical portion 101e is interposed.

FIG. 4 is a sectional view showing an electric power steering apparatus 200 according to the second embodiment, cut along an input shaft. Regarding the second embodiment,
As compared with the first embodiment, only the joining method of the main body 201a and the lower column tube 201c is different.
The description of the other components is omitted.

In the present embodiment, the left end of the lower column tube 201c is press-fitted so as to be inserted into the inner cylindrical portion 201e, so that the lower column tube 201c as in the first embodiment is fitted. The body 20
A mounting bracket for mounting to 1a is not required, so that the collapse stroke S can be secured longer, and the number of parts and cost can be reduced.

FIG. 5 is a sectional view showing an electric power steering apparatus 300 according to the third embodiment, cut along an input shaft. Regarding the third embodiment,
Since only the dividing position of the housing 201 is different from that of the first embodiment, the description of the other components is omitted.

In the present embodiment, the housing 30
The joining position of the main body 301a and the cover member 301b constituting the first shaft 1 is near the abutting end of the input shaft 103 and the output shaft 102. According to the present embodiment having such a configuration, assembling and disassembly of the electric power steering device 300 are facilitated.

As described above, the present invention has been described in detail with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and may be appropriately modified within a range not to impair the gist of the present invention. Of course, it can be improved.

Further, as for the sensor member, a modified example shown in FIGS. In the sensor member 130 'of FIG. 6, the vicinity of the mounting end of the adjacent pillar portion 132' is not connected, and is directly connected to the disk portion 131. In the sensor member 130 "of FIG. 7, the end opposite to the disk portion 131" of the pillar portion 132 "is connected by a ring-shaped member 133" to increase the rigidity of the pillar portion 132 ".

[0040]

According to the present invention, there is provided an electric power steering apparatus comprising: a housing; an input shaft for inputting a steering force; an electric motor for generating a rotational force; an output shaft connected to a steering mechanism; A torsion bar connecting between the output shaft, a detecting device for detecting a twist amount of the torsion bar, and a power transmission mechanism for transmitting the rotational force from the electric motor to the output shaft, The detection device is
A sensor member provided on one of the input shaft and the output shaft, formed of a magnetic material, and having a hole or notch communicating the inner and outer circumferences, provided on the other of the input shaft and the output shaft, A cylindrical member that extends so as to surround at least a part of the sensor member, and a coil member that detects a torsion amount of the torsion bar based on an overlapping state of the hole or notch and the cylindrical member, Since at least one of the seal member and the column tube is arranged on the radially inner side of the coil member, it is necessary to arrange the joint between the seal member and the column tube and the housing in the axial direction of the coil member. Therefore, the collapse stroke can be sufficiently secured with a compact structure.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an electric power steering apparatus according to a first embodiment, cut along an axis of an input shaft.

FIG. 2 is a perspective view showing a part of an input shaft 102 and an output shaft 103 in an exploded state including peripheral parts.

FIG. 3 is a diagram illustrating a method of assembling a sensor member with respect to an input shaft.

FIG. 4 is a cross-sectional view showing an electric power steering apparatus according to a second embodiment, which is cut along an axis of an input shaft.

FIG. 5 is a sectional view showing an electric power steering apparatus according to a third embodiment, cut along an axis of an input shaft.

FIG. 6 is a view showing a modification of the sensor member, and FIG.
(A) is a view of the same viewed from the axial direction, and FIG.
(B) is a diagram viewed in a direction perpendicular to the axis.

FIG. 7 is a view showing another modification of the sensor member, and FIG.
FIG. 7A is a view of the same viewed from the axial direction, and FIG.
(B) is a diagram viewed in a direction perpendicular to the axis.

FIG. 8 shows a conventional electric power steering device.
It is sectional drawing cut | disconnected and shown along the axis of an input shaft.

[Explanation of symbols]

100, 200, 300 Electric power steering device 101, 201, 301 Housing 101c, 201c, 301c Inner cylindrical part 102 Input shaft 103 Output shaft 104 Torsion bar 106 Torque sensor 120 Cylindrical member 130, 130 ', 130 "Sensor member 150 Yoke

Claims (3)

[Claims] 1. A housing, an input shaft for inputting a steering force, an electric motor for generating a rotational force, an output shaft connected to a steering mechanism, and a torsion connecting the input shaft and the output shaft. A detection device that detects the amount of twisting of the torsion bar; and a power transmission mechanism that transmits the rotational force from the electric motor to the output shaft. The detection device includes the input shaft and the output. A sensor member provided on one of the shafts and formed of a magnetic material and having a hole or notch communicating the inner and outer circumferences; and a sensor member provided on the other of the input shaft and the output shaft, and at least a part of the sensor member And a coil member that detects the amount of twist of the torsion bar based on the overlapping state of the hole or notch and the cylindrical member. Radially inside the coil member, the seal member and the electric power steering apparatus, wherein at least one of the column tube is arranged. 2. A housing made of a conductive material or a conductive member separate from the housing is disposed radially inward of the coil member, and the seal member is attached to the conductive member. The electric power steering apparatus according to claim 1, wherein a space between an inner peripheral surface of the electric power steering shaft and an outer peripheral surface of the input shaft is sealed. 3. The electric power steering apparatus according to claim 1, wherein the column tube is fitted into the housing made of a conductive material on a radially inner side of the coil member. .