JP3985678B2 - Electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering apparatus including a steering assisting electric actuator in the middle of a column shaft that connects a steering member such as a steering wheel and a steering mechanism.
[0002]
[Prior art]
More specifically, in response to the operation of a steering member such as a steering wheel, the electric actuator for assisting steering is driven based on the detection result of the steering torque applied to the steering member by the driver, and the generated force of the electric actuator is steered. As a form of an electric power steering apparatus that assists steering by transmitting to the take-off mechanism, the generated force of the electric actuator is transmitted to the middle of the column shaft that communicates the steering member and the steering mechanism, and assists the rotation of the column shaft. There is a column assist type electric power steering device.
[0003]
Many of the electric power steering devices of this type use a motor as an electric actuator because the column shaft to be transmitted is a rotating shaft, and the rotation of the motor attached to the outside of the housing that supports the column shaft This is transmitted to the column shaft via a transmission device arranged inside the, and the column shaft is rotated. The transmission is configured as a reduction gear to obtain a sufficient steering assist force with a small, small output motor, and further, a high reduction ratio can be obtained in a space-saving manner, so it is connected to the output end of the motor. A worm gear reduction device is widely used in which the worm is engaged with a worm wheel fitted in the middle of the column shaft (see, for example, Patent Document 1).
[0004]
[Patent Document 1]
JP 2000-95120 A
[Problems to be solved by the invention]
However, in the column assist type electric power steering apparatus as described above, since the electric actuator configured to be transmitted to the column shaft is located inside the passenger compartment, it is difficult to avoid interference with the driver's undercarriage. There is a problem of obstructing driving operation such as brake operation.
[0006]
In particular, when a motor is used as the electric actuator and a worm gear reduction device is used as a transmission device from the motor to the column shaft, the motor can be reduced in size, but the axial direction of the motor connected to the worm is the worm wheel. Since the motor is mounted so as to protrude tangentially to the outside of the column shaft housing, there is significant interference with the driver's undercarriage, and prevention of driving operation hindrance However, there is a problem that the mounting position of the motor is restricted.
[0007]
It is also possible to install a steering assisting motor on the outside of the column shaft housing so as to be parallel to this and transmit the rotation of the motor to the column shaft by a spur gear transmission. In order to obtain a reduction ratio equivalent to that of the worm gear reduction device, there is a problem that the transmission device is enlarged, and when the reduction device is reduced and the transmission device is reduced in size, the motor itself is increased in size. There is a problem and the desired interference prevention effect cannot be obtained.
[0008]
The present invention has been made in view of such circumstances, and the electric actuator for assisting the steering and the transmission device from the electric actuator can be compactly configured around the column shaft, so that the driver's suspension can be obtained. An object of the present invention is to provide an electric power steering device that reduces the degree of interference and does not hinder driving operations.
[0009]
[Means for Solving the Problems]
An electric power steering apparatus according to a first aspect of the present invention transmits a generated force of an electric actuator driven in accordance with an operation of a steering member to a column shaft connecting the steering member and a steering mechanism, In the electric power steering apparatus for assisting steering performed by transmitting the rotation to the steering mechanism, a linear motor is used as the electric actuator, and is supported on the same axis as the column shaft. And a screw mechanism that is configured on an opposing circumference of the movable cylinder and the column shaft, and converts axial movement of the movable cylinder into rotation of the column shaft. .
[0010]
In the present invention, a linear motor is used as an electric actuator for assisting steering, and the operation of the traveling element of the linear motor is transmitted to a moving cylinder supported coaxially with the column shaft, and the axial movement of the moving cylinder by this transmission is performed. Is converted by a screw mechanism arranged on the periphery of the column shaft, and a rotational force for assisting steering is applied to the column shaft. The transmission provided with the moving cylinder and the screw mechanism is configured to be compact by being coaxial with the outside of the column shaft, reducing the degree of interference with the driver's suspension, and effectively preventing the inhibition of driving operation. it can.
[0011]
An electric power steering apparatus according to a second aspect of the present invention is characterized in that the linear motor according to the first aspect is configured such that the movable cylinder is a traveling element and is coaxial with the movable cylinder and the column shaft. And
[0012]
In the present invention, the steering assist linear motor is integrally formed as a traveling element that constitutes a transmission device for the column shaft, and the linear motor and the transmission device are compactly arranged outside the column shaft. This further reduces the degree of interference with the driver's undercarriage and prevents the driving operation from being hindered.
[0013]
Furthermore, an electric power steering apparatus according to a third aspect of the present invention includes a steering angle sensor that detects a steering angle based on a movement position of the movable cylinder in the axial length direction.
[0014]
In the present invention, the angle of steering performed over a plurality of rotations of the column shaft is detected with high accuracy with a simple configuration using the movement position in the axial length direction of the movable cylinder corresponding to the rotation position of the column shaft as a medium. .
[0015]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic diagram showing an overall configuration of an electric power steering apparatus according to the present invention, in which steering is performed in the middle of a column shaft 3 that connects a rack and pinion type steering mechanism 1 and a steering wheel 2 as a steering member. It is configured as a column assist type electric power steering device that transmits the generated force of the auxiliary electric actuator M and assists the operation of the steering mechanism 1 according to the rotation of the column shaft 3.
[0016]
The steering mechanism 1 includes a cylindrical rack housing H ₁ that extends in the left-right direction of a vehicle body (not shown), and a rack shaft 10 that is supported inside the rack housing H ₁ so as to be movable in the axial direction. It has. Both ends of the rack shaft 10 projecting on both sides of the rack housing H ₁ are connected to knuckle arms 12 and 12 of left and right front wheels 11 and 11 as steering wheels via separate tie rods 13 and 13, By moving the rack shaft 10 in both directions, the knuckle arms 12 and 12 are pushed and pulled through the tie rods 13 and 13 to steer the left and right front wheels 11 and 11.
[0017]
In the vicinity one end of the rack housing H _1, to cross it and the shaft center and the pinion housing H ₂ is continuously provided, the inside of the pinion housing H _2, rotatably pinion in the axis around A shaft 14 is supported. The pinion shaft 14 is shown only with an upward projecting portion of the pinion housing H ₂ , and this projecting portion is connected to the lower end of the column shaft 3 via an intermediate shaft 16 having universal joints 15 and 15 at both ends. Has been.
[0018]
At the bottom of the pinion shaft 14 which extends inside the pinion housing H _2, a pinion (not shown) is provided integrally. A rack tooth is formed on the rack shaft 10 supported inside the rack housing H ₁ over an appropriate length including the crossing position with the pinion housing H _2, and the rack teeth serve as the pinion shaft 14. The lower pinion is engaged with the pinion.
[0019]
The column shaft 3 is rotatably supported on the same axis in a cylindrical column housing H ₃ , and is fixedly supported in a rearward and upward direction inside a passenger compartment (not shown). The column housing ₃ is fitted and fixed to the upper end portion of the column shaft 3 protruding from the upper portion of the column housing H ₃ .
[0020]
With the above configuration, when the steering wheel 2 is rotated for steering, the column shaft 3 to which the steering wheel 2 is fitted and fixed rotates around the axis, and this rotation is rotated via the intermediate shaft 16 to the pinion shaft. 14, the rotation of the pinion shaft 14 is converted into movement in the axial direction of the rack shaft 10 at the meshing portion of the pinion and rack teeth, and the left and right front wheels 11 and 11 are steered as described above by this movement.
[0021]
The steering assisting electric actuator M for assisting such steering is provided in the transmission housing H ₄ coaxially connected to the lower portion of the column housing H ₃ , the transmission means 4 (see FIG. 2), and the steering wheel. And a torque sensor T that detects a steering torque applied to the column shaft 3 in response to the operation 2.
[0022]
For example, as disclosed in Japanese Patent No. 3173903 by the applicant of the present application, the torque sensor T is configured such that the middle part of the column shaft 3 has a first axis on the steering wheel 2 side and a second axis on the steering mechanism 1 side. And these are connected via a small-diameter torsion bar, and the circumferential direction generated between the first and second shafts due to the twisting of the torsion bar due to the action of the steering torque applied to the steering wheel 2 It has a known configuration for detecting relative displacement, and only the arrangement position is shown in FIG. 1, and a detailed description of the configuration and operation is omitted.
[0023]
FIG. 2 is a longitudinal sectional view schematically showing the configuration of the steering assisting electric actuator M and the transmission means 4 inside the transmission housing H ₄ . As shown in the figure, a column shaft 3 is rotatably supported on the shaft center portion of the transmission housing H ₄ , and the column shaft 3 has a cylindrical shape coaxially with the column shaft 3 on the outside. The movable cylinder 40 is supported so as to be movable in the axial direction.
[0024]
Screw grooves having a semicircular cross section are formed on the inner peripheral surface of the moving cylinder 40 as described above and the outer peripheral surface of the column shaft 3 facing the inner side thereof, and these screw grooves are passed through a plurality of balls. A ball screw mechanism (screw mechanism) 41 is constituted by screwing, and the ball screw mechanism 41 and the moving cylinder 40 constitute the transmission means 4.
[0025]
Also on the outer peripheral surface of the moving cylinder 40, a plurality of magnets 42, 42 ... are arranged in the axial direction, on the inner peripheral surface of the transmission housing H ₄ for further surrounding the outside of the moving cylinder 40, the magnet 42, A plurality of stator coils 43, 43, which face the outer surface of 42, with a slight gap and are arranged at intervals corresponding to these magnets 42, 42, are provided as a linear motor as an electric actuator M However, the movable cylinder 40 is configured as a traveling element.
[0026]
In the electric actuator M configured as described above, the moving force in the axial direction is applied to the moving cylinder 40 including the magnets 42, 42, by the action of a moving magnetic field formed by energization control of the stator coils 43, 43,. Is added. This moving force is transmitted to the column shaft 3 via a ball screw mechanism 41 formed on the opposed peripheral surface of the moving cylinder 40 and the column shaft 3, and a rotational force around the axis is applied to the column shaft 3.
[0027]
That is, the generated force of the linear motor as the electric actuator M is transmitted to the column shaft 3 by the operation of the transmission means 4 including the moving cylinder 40 that also serves as a traveling element and the ball screw mechanism 41, and the column shaft 3 is rotated around the axis. The rotation of the column shaft 3 is transmitted to the steering mechanism 1 through the intermediate shaft 16, and the steering generated as described above is assisted by the operation of the steering mechanism 1.
[0028]
At this time, the rotational force (steering assisting force) applied to the column shaft 3 is changed by drive control of the steering assisting electric actuator M. The drive control of the electric actuator M is performed by the operation of the steering control unit 5 shown in FIG. The steering control unit 5 is provided with a steering torque detection result from the torque sensor T configured as described above in the middle of the column shaft 3, and the vehicle speed and yaw rate are determined from the running state sensors 50 provided in each part of the vehicle. Further, detection results of a running state that affects steering such as lateral acceleration and longitudinal acceleration are given.
[0029]
Further, the steering control unit 5 is given a detection result of the steering angle from a steering angle sensor 44 attached to the transmission housing H ₄ . As shown in FIG. 2, the steering angle sensor 44 is attached to the transmission housing H ₄ so as to face the end surface of the movable cylinder 40. For example, the end surface of the movable cylinder 40 is irradiated with light and the reflected light from the end surface is captured. And an optical sensor that emits an output corresponding to the received light level. Since this output corresponds to the moving position of the moving cylinder 40 that moves as described above and the rotational position of the column shaft 3 that accompanies this movement, it is used as a result of detecting the steering angle that indicates the amount of rotational operation of the steering wheel 2. be able to.
[0030]
The rotation operation of the steering wheel 2 for steering is generally performed a plurality of times on both the left and right sides starting from the neutral position during straight traveling, during which the moving cylinder 40 moves over a predetermined stroke in the axial length direction. Therefore, according to the steering angle sensor 44 whose detection target is the moving position, the steering angle for a plurality of rotations of the steering wheel 2 can be detected with high accuracy over a whole area with a simple configuration. Become. The steering angle sensor 44 may be any sensor as long as an output corresponding to the position of the movable cylinder 40 can be obtained. The steering angle sensor 44 is not limited to the optical sensor described above, and may be configured using other sensors such as a magnetic sensor. .
[0031]
The steering control unit 5 determines a control target value based on the detection result of the steering torque given from the torque sensor T, and determines the control target value based on the detection result of the running state given from the running state sensor 50 and the steering angle sensor 44. Is corrected based on the detection result of the steering angle given from the control unit, an operation command is issued to the steering assist electric actuator M to obtain a corrected control target value, and the drive current of the electric actuator M configured as a linear motor is increased or decreased. Control action to control. As a result, a steering assist force according to the state of steering is applied to the column shaft 3, and the driver operating the steering wheel 2 can feel a light and good steering feeling.
[0032]
In the electric power steering apparatus according to the present invention, the transmission means 4 that transmits the generated force of the steering assisting electric actuator (linear motor) M that is driven and controlled as described above to the column shaft 3 is coaxial with the column shaft 3. inside the moving cylinder 40 which is supported, and a ball screw mechanism 41 that is configured to face the circumferential surface of the moving cylinder 40 and the column shaft 3, the transmission housing H ₄ provided continuously at the bottom of the column housing H ₃ Te Further, since the electric actuator M configured as a linear motor is coaxially configured with the movable cylinder 40 as a traveling element, a protruding portion to the outside of the column housing H ₃ is provided. This reduces the amount of interference with the driver's undercarriage when operating the steering wheel 2 and hinders driving operations such as accelerator operation and brake operation. It is possible to effectively prevent.
[0033]
Furthermore, since the transmission from the electric actuator M to the column shaft 3 occurs through deceleration by the ball screw mechanism 41, the electric actuator M can be reduced in size, and the above-described interference mitigation effect can be further enhanced.
[0034]
The electric actuator M configured as a linear motor may be attached to the outside of the column housing H ₃ and connected to the movable cylinder 40 by a connecting member such as a connecting rod. Also in this case, the effect of reducing the degree of interference with the driver's suspension can be obtained by making the transmission means 4 compact.
[0035]
In the above embodiment, the ball screw mechanism 41 is used to convert the movement of the movable cylinder 40 in the axial direction into the rotation of the column shaft 3, but a trapezoidal screw or the like is used instead of the ball screw mechanism 41. Other screw mechanisms may be used, and further, a screw mechanism using a bearing disclosed in Japanese Patent Application Laid-Open No. 2001-187955 or the like, a so-called bearing screw may be used.
[0036]
Furthermore, in the above embodiment, although the application example to the vehicle provided with the rack and pinion type steering mechanism 1 was described, the present invention is applicable to a vehicle provided with a steering mechanism other than the rack and pinion type. Needless to say, the same effect can be obtained.
[0037]
【The invention's effect】
As described above in detail, in the electric power steering device according to the present invention, the transmission device that transmits the generated force of the steering assisting electric actuator to the column shaft can be configured compactly around the column shaft, so that It becomes possible to reduce the degree of interference to the surroundings and effectively prevent the inhibition of driving operation.
[0038]
In addition, a linear motor as an electric actuator for assisting steering can be compactly formed around the column shaft together with the transmission device, so that the degree of interference with the driver's suspension can be further reduced. By making the movement position of the movable cylinder corresponding to the rotation position of the shaft a detection target, it becomes possible to detect the steering angle accompanied by the rotation of the column shaft a plurality of times with a simple configuration with high accuracy. The invention has an excellent effect.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an overall configuration of an electric power steering apparatus according to the present invention.
FIG. 2 is a longitudinal sectional view schematically showing configurations of a steering assisting electric actuator and transmission means inside a transmission housing;
[Explanation of symbols]
1 Steering mechanism 2 Steering wheel (steering member)
3 Column shaft
40 Moving cylinder
41 Ball screw mechanism (screw mechanism)
44 Steering angle sensor H ₃ Column housing H ₄ Transmission housing M Electric actuator (linear motor)

Claims (3)

The generated force of the electric actuator driven according to the operation of the steering member is transmitted to the column shaft connecting the steering member and the steering mechanism, and the rotation of the column shaft is transmitted to the steering mechanism to assist steering. In the electric power steering device to
Using a linear motor as the electric actuator,
A movable cylinder supported coaxially with the column shaft and moving in the axial direction by transmission from the linear motor;
An electric power steering apparatus comprising: a screw mechanism configured on an opposing circumference of the movable cylinder and the column shaft, and converting axial movement of the movable cylinder into rotation of the column shaft. 2. The electric power steering apparatus according to claim 1, wherein the linear motor is configured such that the movable cylinder serves as a traveling element and is coaxial with the movable cylinder and the column shaft. The electric power steering apparatus according to claim 1 or 2, further comprising a steering angle sensor that detects a steering angle based on a movement position of the movable cylinder in the axial length direction.

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