JP2004074962A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device enabling a control part to detect accurate steering torque. <P>SOLUTION: A spiral cable 9 is housed in a storage member arranged in the inner circumference of a supporting member 8 and wound spirally, and a steering shaft 51 is arranged on the inner circumference side. In the spiral cable 9, the inner circumference side end part is connected to a strain detection element 21 of a strain detection part 2 arranged in a strain causing part 51a in the steering shaft 51, while the outer circumference side end part is connected to a connection part 33b in a control board 31. In this structure, strain quantity caused in the strain detection element 21 due to torsion of the steering shaft 51 can be transmitted to a control part 3 without any overlapping noise. In this way, the control part 3 can detect accurate steering torque. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric power steering device that assists a steering force of a vehicle steering.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as described in Japanese Patent Publication No. 7-62639, an electric power steering apparatus is provided with a strain detector on a connecting member connected to a steering shaft so that when a steering torque is applied to the steering shaft, the connecting member is connected. When the member is twisted, the resistance value of the strain detector changes, and the resistance value of the strain detector is amplified by the amplifier circuit and output to the control unit.
[0003]
[Problems to be solved by the invention]
However, in the above-described electric power steering apparatus, the rotation of the steering shaft causes the distortion detector provided on the connecting member to also rotate. Since the signal is output to the control unit, noise due to sliding of the slip ring is superimposed on the electric signal. Then, since the electric signal including noise is transmitted to the control unit, there is a problem that the control unit cannot detect an accurate steering torque.
[0004]
The present invention has been made in view of the above problems, and has as its object to provide an electric power steering device that allows a control unit to detect an accurate steering torque.
[0005]
[Means for Solving the Problems]
In order to solve the above problem, according to the first aspect, a connecting member that is connected to a steering wheel, rotates when a steering torque is applied to the steering wheel, and is twisted on itself, and is provided on a rotating side connecting member, and the torsion of the connecting member. And a control unit provided on a fixed side for determining a steering assist force for assisting the steering torque based on the distortion amount detected by the distortion detection unit. The electric power steering device is characterized in that the distortion detection unit and the control unit are connected via a spirally wound transmission line.
[0006]
With this configuration, since the distortion detection unit and the control unit are connected via the transmission line, the distortion is transmitted to the control unit without superimposing noise on the amount of distortion generated in the distortion detection unit due to the torsion of the connecting member. be able to. Further, the distortion detection unit is provided on the connection member on the rotation side, and the control unit is provided on the fixed side, and the distortion detection unit and the control unit are connected via a spirally wound transmission line. Therefore, the occurrence of disconnection of the transmission line due to the rotation of the connecting member can be suppressed.
[0007]
Further, in claim 2, there is an amplification unit that amplifies the distortion amount detected by the distortion detection unit and converts it into an electric amount, and outputs the electric amount to the control unit. The amplification unit is provided on a fixed side, A connection member is provided on the inner peripheral side of the transmission line, the inner peripheral end of the transmission line is connected to the distortion detecting unit, and the outer peripheral end of the transmission line is connected to the amplifier. .
[0008]
With this configuration, by providing the connecting member on the inner peripheral side of the transmission line, it is possible to prevent the electric power steering apparatus from being enlarged in the radial direction. In addition, since the amplifying unit is provided on the fixed side, the inner end of the transmission line is connected to the distortion detecting unit, and the outer end of the transmission line is connected to the amplifying unit, thereby rotating the connecting member. Can suppress the occurrence of disconnection of the transmission line.
[0009]
In the third aspect, the distortion detecting section has a plurality of distortion detectors for detecting a distortion amount, and the distortion detectors are provided intensively on a part of the outer peripheral surface of the connecting member, and the inner peripheral portion of the transmission line is provided. The side end is connected to the strain detector.
[0010]
According to this configuration, since the plurality of strain detectors are provided concentrated on a part of the outer peripheral surface of the connecting member, it is possible to easily attach the strain detecting unit to the connecting member. Further, the transmission line can be easily connected to the distortion detector.
[0011]
According to a fourth aspect of the present invention, the control unit and the amplifying unit are supported by a support member that rotatably supports the connecting member.
[0012]
With this configuration, by providing the control unit and the amplification unit on the support member that rotatably supports the connecting member, the control unit and the amplification unit can be fixed.
[0013]
Further, in claim 5, there is provided an amplifying unit that amplifies the amount of distortion detected by the distortion detecting unit and converts it into an electric amount, and outputs the electric amount to the control unit. A connection member is provided on the inner peripheral side of the transmission line, the inner peripheral end of the transmission line is connected to the amplifier, and the outer peripheral end of the transmission line is connected to the control unit.
[0014]
With this configuration, by providing the transmission line on the outer peripheral side of the connecting member, it is possible to prevent the electric power steering device from being enlarged in the radial direction. Further, since the amplifying unit is provided on the rotation-side connecting member, the connecting member is connected by connecting the inner peripheral end of the transmission line to the amplifying unit and connecting the outer peripheral end of the transmission line to the control unit. The occurrence of disconnection of the transmission line due to rotation of the transmission line can be suppressed.
[0015]
According to a sixth aspect of the invention, there is provided a housing member for housing the transmission line.
[0016]
With this configuration, by accommodating the transmission line in the accommodation member, when the diameter of the transmission line increases or decreases due to rotation of the connecting member, the transmission line does not come into contact with other members, thereby improving reliability. Can be.
[0017]
According to a seventh aspect of the present invention, the connecting member has one end connected to the steering wheel and the other end connected to the steered wheels, and is formed as a single member.
[0018]
According to this configuration, the responsiveness when transmitting the steering torque applied to the steering to the steered wheels can be improved by forming the connecting member as one member. Further, the connecting member can be supported by at least two supporting members.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments shown in the drawings will be described.
[0020]
FIG. 1 is an axial sectional view of a part of the electric power steering device 1. FIG. 2 is an axial sectional view along the steering shaft 51 of the electric power steering device 1. FIG. 3 is an exploded perspective view of a housing member that houses the spiral cable 9. 4A is a front view of the control unit 3, and FIG. 4B is a side view of FIG. FIG. 5 is a radial cross-sectional view of a part of the electric power steering device 1. FIG. 6 is a circuit diagram of the distortion detector 21.
[0021]
The electric power steering device 1 according to the present embodiment is provided in a vehicle cabin, and as shown in FIGS. 1 and 2, a distortion detection unit 2, an amplification unit 10, a control unit 3, an electric motor 4, and a power transmission unit 5 The distortion detection unit 2, the control unit 3, and the power transmission unit 5 are provided in the housing 6 and the cover 7, and the electric motor 4 is provided in the yoke 49.
[0022]
The steering shaft 51 forms a connecting member, one end of which is connected to the steering wheel, and the other end of which is connected to the steered wheels. The steering shaft 51 rotates when a steering force is applied to the steering. Further, the steering shaft 51 is formed of one member, and has a planar strain-generating portion 51a formed by grinding and polishing the outer peripheral surface. The strain generating portion 51a is provided at a position close to the inner peripheral side of the control unit 3.
[0023]
The distortion detector 2 detects a steering torque applied to the steering, and has a plurality of distortion detectors 21.
[0024]
The distortion detector 21 is a foil and is provided intensively on one surface of the strain generating portion 51a of the steering shaft 51, which is a rotating side, and is adhered, and detects a distortion amount caused by twisting of the steering shaft 51. To do. As shown in FIG. 6, the distortion detector 21 is connected so as to form a Wheatstone bridge circuit 21a composed of R1, R2, R3 and R4, and its output eo is input to the control unit 3 via the spiral cable 9. Is done. The spiral cable 9 is housed in a housing member, as shown in FIGS. 2 and 3, and the housing member is provided on the inner periphery of the support member 8 and includes a surrounding member 22 and a bottom member 23. ing.
[0025]
The surrounding member 22 covers one end side in the axial direction and the outer peripheral side of the spiral cable 9, and has a hook portion 22 a on the outer peripheral portion and a takeout portion 22 b through which the outer diameter side end of the spiral cable 9 is inserted. .
[0026]
Three hook portions 22 a are provided in the circumferential direction, protrude toward the bottom member 23 in the axial direction, and are hooked on the axial end surface of the bottom member 23. A first insertion hole 22c is formed in the take-out portion 22b on the axial end surface on the control board 3 side, and the spiral cable 9 is inserted into the first insertion hole 22c.
[0027]
The bottom member 23 covers the other end in the axial direction and the inner peripheral side of the spiral cable 9, and has a second insertion hole 23 a through which the inner end of the spiral cable 9 is inserted.
[0028]
The amplification unit 10 amplifies the distortion amount based on the distortion amount detected by the distortion detection unit 2 and converts the distortion amount into an electric amount. The quantity of electricity converted by the amplification unit 10 is output to the control unit 3. Further, as shown in FIG. 4A, the amplification unit 10 is provided on a control board 31 of the control unit 3 which is a fixed side.
[0029]
The control unit 3 controls the duty of the current flowing to the electric motor 4 based on the distortion amount converted by the amplification unit 10.
[0030]
The control board 31 has a plate shape, and as shown in FIG. 4A, has a planar shape in which a rectangular shape and a semicircle shape are combined, and the input shaft 51 is provided at the center of the semicircle side. A round hole 31a for passing through is provided. The control board 31 is provided with a through hole 31b to which the motor terminal 41 of the electric motor 4 is connected.
[0031]
The switching transistor 32 is directly fixed to the slope portion 82 of the support member 8 by screwing or the like. As shown in FIG. 2, the switching transistor 32 is connected to the control board 31 such that a terminal taken out to the side of the switching transistor 32 is bent toward the steering side in the axial direction.
[0032]
As shown in FIG. 4A, a control element 33, relays 34 and 35, and a capacitor 36 are directly mounted on the control board 31.
[0033]
The control element 33 is an element such as a microcomputer 33a, and determines a current to be supplied to the electric motor 4 according to the amount of electricity converted by the amplifying unit 10, and generates a signal for duty-controlling the switching transistor 32. I do.
[0034]
The microcomputer 33a is connected to the amplifying unit 10, receives the amount of electricity changed by the amplifying unit 10, and converts the amount of distortion into a digital signal. The relay 34 conducts and cuts off the current flowing to the electric motor 4 when an ignition switch (not shown) is turned on and off. The relay 35 is connected to the electric motor 4 and the switching transistor 32 to prevent the electric motor 4 from generating electric power when the electric motor 4 is rotated in response to a steering input when the drive circuit of the electric motor 4 fails. The current flowing between them is interrupted. The capacitor 36 suppresses fluctuations in the power supply voltage.
[0035]
The spiral cable 9 forms a transmission line, is housed in the above-described housing member provided on the inner circumference of the support member 8, is spirally wound, and has a steering shaft 51 provided on the inner circumference side. The spiral cable 9 has a connection portion of a control board 31 whose inner diameter end is connected to the strain detector 21 and whose outer diameter end is connected to the amplifier 10 as shown in FIG. 33b.
[0036]
The electric motor 4 applies a steering assist force for assisting the steering torque of the steering determined by the control unit 3 to the steering shaft 51, and has a magnet 48 on the inner circumference of a magnetic yoke 49. This is a DC motor including a field, an armature 47 rotatably supported on the inner periphery of the field, and a brush 43 slidingly contacting a commutator 46 provided on the armature 47. The brush 43 is urged in the inner diameter direction by a spring 44 provided in the brush holder 43a, so that the brush 43 is slidably contacted with the commutator 46. Further, as shown in FIG. 5, the electric motor 4 is assembled with the opening end surface of the yoke 49 abutting on the side surface of the housing 6 and fixed to the frame end 70 by the bolt 18.
[0037]
As shown in FIG. 1, the electric motor 4 is electrically connected to the brush 43 via a pigtail 42 and includes a metal motor terminal 41 provided in the housing 6. It is resistance-welded to a plate 19a which is insert-molded in a resin holder plate 19.
[0038]
The holder plate 19 fixes a brush holder 43a that slidably holds the brush 43. As shown in FIG. The electric motor 4 is attached to the housing 6 by being inserted into the housing 6 through an opening 20 formed in a side surface of the housing 6.
[0039]
The motor terminal 41 is for power supply, and is bent substantially at a right angle. After the electric motor 4 is assembled to the housing 6 as shown in FIGS. The other end is connected to the substrate 31 via solder, and the other end is connected to a terminal plate 43c held between the end frame 43d and the brush holder 43a via a rubber mount 43b.
[0040]
The end frame 43d is an iron plate, is fixed to the yoke 49, and is sandwiched between the housing 6 and the yoke 49. The rubber mount 43b absorbs vibration generated when the brush 43 slides on the outer peripheral surface of the commutator 46. The terminal plate 43c holds a metal terminal inside a resin member. When the terminal in the terminal plate 43c is connected to the motor terminal 41 and the pigtail 42, a current is supplied from the battery to the brush 43. Supplying.
[0041]
The current determined by the control unit 3 and subjected to the duty control by the switching transistor 32 is supplied to the armature 47 via the motor terminal 41, the plate 19a, the pigtail 42, and the brush 43.
[0042]
The power transmission unit 5 transmits the steering assist force output from the electric motor 4 to the steered wheels, and includes a steering shaft 51, a worm wheel 52, and a worm gear 53.
[0043]
As shown in FIG. 1, the worm gear 53 is fixed to the armature shaft 45 of the electric motor 4 via the transmission member 16, and rotates by transmitting the torque of the armature shaft 45.
[0044]
As shown in FIG. 2, the worm wheel 52 is fixed to the outer periphery of the steering shaft 51, and the outer periphery of the worm wheel 52 meshes with the worm gear 53. The worm wheel 53 rotates in the circumferential direction when the worm gear 53 rotates.
[0045]
The housing 6 is made of aluminum, and a support member 8 is provided inside the housing 6. The housing 6 rotatably supports a steering shaft 51 via a bearing 12.
[0046]
The cover 7 is made of aluminum similarly to the housing 6, and covers an opening of the housing 6 provided to accommodate the torque sensor 2, the amplification unit 10, the control unit 3, and the power transmission unit 5 in the housing 6. , For fixing the bearing 13 that supports the input shaft 51. The cover 7 presses the support member 8 so that the support member 8 comes into contact with the inner wall of the housing 6. The cover 7 is fixed to cover fixing portions 71a and 71b provided on the housing 6, as shown in FIG. The cover fixing portion 71a is provided at a position close to a line where the outer wall of the housing 6 and the outer wall of the yoke 49 are in contact with each other. The cover fixing portion 71b is provided at a position symmetric with respect to the axis of the cover fixing portion 71a.
[0047]
The support member 8 is made of aluminum, and supports the control unit 3 on a surface on the steering side in the axial direction as shown in FIG. 2, and rotatably supports the steering shaft 51 via the bearing 11. Further, the support member 8 has a contact portion 81 that contacts the inner wall of the housing 6. Further, as shown in FIG. 4B, the support member 8 has a power supply terminal for connection to a battery and a signal terminal for inputting a vehicle speed signal, an engine speed signal, and the like. The connector 15 is fixed.
[0048]
(Effect of this embodiment)
In the electric power steering apparatus 1 according to the present embodiment, since the distortion detection unit 2 and the control unit 3 are connected via the spiral cable 9, the distortion detector 21 of the distortion detection unit 2 is twisted by the steering shaft 51. Can be transmitted to the control unit 3 without superimposing noise on the amount of distortion generated in. Thereby, the control unit 3 can detect an accurate steering torque.
[0049]
Further, since the spiral cable 9 is spirally wound and the steering shaft 51 is provided on the inner peripheral side, it is possible to prevent the electric power steering device 1 from being enlarged in the radial direction.
[0050]
Further, the inner peripheral end of the spiral cable 9 is connected to the distortion detector 21 provided on the steering shaft 51, and the outer peripheral end is connected to the connection part 33 b of the control board 31 supported by the support member 8. Thus, the occurrence of disconnection of the spiral cable 9 due to the rotation of the steering shaft 51 can be suppressed.
[0051]
Further, since the strain detector 21 is provided to be concentrated on one side of the strain generating portion 51a of the steering shaft 51, the strain detector 21 can be easily bonded to the strain generating portion 51a. Further, connection between the inner peripheral end of the spiral cable 9 and the strain detector 21 can be facilitated.
[0052]
Further, since the spiral cable 9 is housed in the housing member, when the diameter of the spiral cable 9 increases or decreases due to the rotation of the steering shaft 51, the spiral cable 9 does not come into contact with other members. Improvement can be achieved.
[0053]
Further, the steering shaft 51 has one end connected to the steering wheel and the other end connected to the steered wheel side, and is constituted by a single member. Performance can be improved. Further, the steering shaft 51 can be supported only by the bearings 11 and 12.
[0054]
The strain detector 21 is a foil and is adhered to the strain-generating portion 51a of the steering shaft 51. Is also good.
[0055]
Although the amplifying unit 10 of the present embodiment is provided on the control board 31 on the fixed side, it may be provided on the outer peripheral surface of the steering shaft 51 on the rotating side. In this case, disconnection of the spiral cable 9 due to rotation of the steering shaft 51 can be suppressed by connecting the amplification unit 10 and the connection unit 33b of the control board 31 with the spiral cable 9.
[Brief description of the drawings]
FIG. 1 is an axial sectional view of a part of an electric power steering device.
FIG. 2 is an axial sectional view along a steering shaft of the electric power steering device.
FIG. 3 is an exploded perspective view of a housing member that houses the spiral cable.
FIG. 4A is a front view of a control unit, and FIG. 4B is a side view of FIG.
FIG. 5 is a radial sectional view of a part of the electric power steering device.
FIG. 6 is a circuit diagram of a distortion detector.
[Explanation of symbols]
1. Electric power steering device,
2... Distortion detector,
3 ... Control unit,
4: Electric motor,
5. Power transmission unit,
6 ... housing,
7 ... Cover,
8. Supporting member,
9 Spiral cable (transmission line),
21: strain detector,
31 ... control board,
51 ... steering shaft (connection member),
52… worm wheel,
53 ... Worm gear.

Claims (7)

A connecting member that is connected to a steering wheel, rotates when a steering torque is applied to the steering wheel, and generates a twist in itself;
A distortion detection unit provided on the rotation-side connection member, for detecting a distortion amount caused by torsion of the connection member,
An electric power steering apparatus comprising: a steering assisting force that assists the steering torque based on the distortion amount detected by the distortion detection unit, and a control unit provided on a fixed side.
The electric power steering device according to claim 1, wherein the distortion detection unit and the control unit are connected via a transmission line wound spirally. An amplification unit that amplifies the distortion amount detected by the distortion detection unit, converts the distortion amount into an electric amount, and outputs the electric amount to the control unit,
The amplification unit is provided on a fixed side,
The connection member is provided on an inner peripheral side of the transmission line, and an inner peripheral end of the transmission line is connected to the distortion detection unit, and an outer peripheral end of the transmission line is connected to the amplification unit. The electric power steering apparatus according to claim 1, wherein The distortion detection unit has a plurality of distortion detectors for detecting the distortion amount,
The strain detector is provided concentrated on a part of the outer peripheral surface of the connecting member,
The electric power steering apparatus according to claim 2, wherein an inner peripheral end of the transmission line is connected to the distortion detector. The electric power steering apparatus according to claim 2, wherein the control unit and the amplification unit are supported by a support member that rotatably supports the connection member. An amplification unit that amplifies the distortion amount detected by the distortion detection unit, converts the distortion amount into an electric amount, and outputs the electric amount to the control unit,
The amplifying unit is provided on the connecting member,
The connection member is provided on an inner peripheral side of the transmission line, and an inner peripheral end of the transmission line is connected to the amplification unit, and an outer peripheral end of the transmission line is connected to the control unit. The electric power steering device according to claim 1, wherein: The electric power steering apparatus according to any one of claims 1 to 5, further comprising a housing member that houses the transmission line. 7. The connecting member according to claim 1, wherein one end of the connecting member is connected to the steering wheel, and the other end is connected to a steered wheel side. Electric power steering device.

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