JP3991841B2 - Vehicle steering system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle steering apparatus including a motor that is driven in accordance with an operation of a steering member such as a steering wheel and applies a moving force in an axial length direction for steering to a steering shaft in a steering mechanism.
[0002]
[Prior art]
Steering of a vehicle is performed by steering a steering member (generally a steering wheel rotation operation) performed by a driver inside a passenger compartment to steer steered wheels (typically left and right front wheels). This is done by telling the steering mechanism located outside the room.
[0003]
In recent years, as a steering device for performing such steering, the rotational force of a motor that is rotationally driven based on the detection result of the steering torque applied to the steering member is transmitted to the steering mechanism, and the steering force is assisted by this rotational force. A steering device (electric power steering device) configured to be widely used has been widely put into practical use, and the steering member and the steering mechanism are mechanically separated to detect the direction and amount of operation of the steering member. A steering device configured to perform steering only by the rotational force of a motor that is rotationally driven based on the result, a so-called steer-by-wire type steering device has also been put into practical use.
[0004]
This type of steering device, for example, converts the rotational motion of the motor into a linear motion and transmits it to the steering shaft in the steering mechanism, and transmits the movement of the steering shaft in the axial direction to the left and right steering wheels. It is configured to perform steering. The motion conversion from the rotation of the motor to the movement of the steering shaft is performed by using a screw mechanism including a screw groove formed on the outer peripheral surface of the steering shaft and a nut member screwed into the screw groove. This is realized by a configuration in which the steering shaft is moved using the screw groove according to the rotation of the nut member according to the rotation of the nut member (see, for example, Patent Documents 1 and 2). The steering shaft is, for example, a rack shaft in a rack and pinion type steering device.
[0005]
[Patent Document 1]
Utility Model Registration No. 2590791 [Patent Document 2]
Japanese Examined Patent Publication No. 4-28583 [0006]
[Problems to be solved by the invention]
Now, the steering devices disclosed in Patent Documents 1 and 2 are different in the structure of the transmission means for transmitting the rotation of the motor attached to the outside of the housing that supports the steering shaft to the nut member. A gear transmission is employed in which the rotation of the drive gear attached to the motor shaft of the motor is transmitted to a driven gear provided on the outer periphery of the ball nut via an intermediate gear to rotate the ball nut.
[0007]
In Patent Document 2, a transmission belt is stretched between a drive pulley attached to the motor shaft of the motor and a driven pulley provided on the outer periphery of the nut member, and the rotation of the motor shaft is A belt transmission is used that transmits to the nut and rotates the ball nut.
[0008]
However, in these, there are two kinds of transmission mechanisms (gear mechanism or belt mechanism and screw mechanism) in the transmission system from the motor to the steering shaft, and the screw shaft and the nut member are used as the screw mechanism. Although the transmission efficiency is good, the ball screw mechanism with a complicated structure is adopted in many cases, and the entire structure of the transmission system is complicated, and a lot of man-hours are required for processing and assembly of each part. There was a problem of requiring.
[0009]
The present invention has been made in view of such circumstances, and transmission from a motor that is rotationally driven in response to an operation of a steering member to a steering shaft that moves in the axial direction for steering is performed with a simple configuration. It is an object of the present invention to provide a vehicle steering apparatus including a novel transmission means that can be reliably performed.
[0010]
[Means for Solving the Problems]
The vehicle steering apparatus according to the first aspect of the present invention transmits the rotational force of the motor driven in accordance with the operation of the steering member to the steering shaft in the steering mechanism, and moves the steering shaft in the axial direction. In a vehicle steering apparatus for performing steering, a belt pulley coaxially fixed to a motor shaft of the motor, a belt groove formed in a spiral shape on an outer peripheral surface of the steering shaft, the belt groove and the belt pulley And a transmission belt stretched between the steering shaft and the motor shaft.
[0011]
In the present invention, the transmission belt is wound up by a belt pulley that is rotated by the transmission from the motor, and a force in a direction along the inclination is applied to the spiral belt groove on the outer peripheral surface of the steering shaft around which the transmission belt is wound. In addition, steering is performed by moving the steering shaft by the action of the axial force component of this force. Transmission from the motor to the steering shaft is made by a simple configuration using only a transmission belt stretched between the two.
[0012]
A vehicle steering apparatus according to a second aspect of the present invention is characterized in that the transmission belt according to the first aspect is wound around the belt groove and the belt pulley a plurality of times.
[0013]
In this invention, the transmission belt stretched between the motor and the steering shaft is wound around the belt pulley fixed to the motor shaft and the belt groove on the outer periphery of the steering shaft a plurality of times, and the friction of the winding portion is Increase resistance to ensure transmission from the motor to the steering shaft.
[0014]
Furthermore, the vehicle steering apparatus according to a third aspect of the present invention acts on the transmission belt in the vicinity of the position where the belt groove is wound, and restricts the movement of the transmission belt in the axial length direction of the steering shaft. It is characterized by providing a guide means.
[0015]
In the present invention, the guide belt arranged as close as possible to the steering shaft acts on the transmission belt stretched between the motor and the steering shaft so that the transmission belt moves in the axial direction of the steering shaft. The steering shaft is reliably moved by the axial length component of the force applied to the belt groove around which the transmission belt is wound.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. FIG. 1 is a schematic diagram showing the overall configuration of a vehicle steering apparatus according to the present invention. The vehicle steering apparatus shown in this figure transmits a rotational force of a steering assisting motor 3 to a rack shaft 1 as a steering shaft, and moves the rack shaft 1 in the axial direction to assist steering. It is configured as an electric power steering device.
[0017]
The rack shaft 1 is movably supported in the axial direction inside the rack housing H ₁ having a cylindrical shape, and extends in the lateral direction of the vehicle body, not shown. Both ends of the rack shaft 1 projecting on both sides of the rack housing H ₁ are connected to the knuckle arms 11 and 11 of the left and right front wheels 10 and 10 as steering wheels via separate tie rods 12 and 12, respectively. By moving the shaft 1 in both the left and right directions, the knuckle arms 11 and 11 are pushed and pulled through the tie rods 12 and 12 so that the left and right front wheels 10 and 10 are steered.
[0018]
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 The shaft 2 is supported. The pinion shaft 2 is shown only with an upward projecting end of the pinion housing H ₂ , and this projecting end is connected to a steering wheel 21 as a steering member via a column shaft 20.
[0019]
The lower half portion of the pinion shaft 2 that extends inside the pinion housing H _2, a pinion (not shown) is provided integrally. In addition, rack teeth (not shown) are formed on the rack shaft 1 supported inside the rack housing H ₁ over an appropriate length including the crossing position with the pinion housing H ₂ . The pinion shaft 2 is engaged with the pinion provided in the lower half of the pinion shaft 2.
[0020]
With the above configuration, when the steering wheel 21 is rotated for steering, the pinion shaft 2 connected to the steering wheel 21 via the column shaft 20 rotates, and this rotation is caused by the rotation of the pinion and the rack teeth. At the meshing portion, the rack shaft 1 is converted into a movement in the axial length direction, and by this movement, the left and right front wheels 10 and 10 are steered as described above, and the steering is performed according to the operation of the steering wheel 21.
[0021]
Motor 3 for steering assistance for assisting such a steering on one side opening of the middle section motor bracket 30 projecting from the outside of the rack housing H _1, the rack housing H ₁ inside of the rack shaft 1 and substantially parallel to And is transmitted to the rack shaft 1 by transmission means 4 (see FIG. 2) configured inside the motor bracket 30.
[0022]
FIG. 2 is a longitudinal sectional view showing a schematic configuration of the transmission means 4 from the steering assisting motor 3 to the rack shaft 1. The motor bracket 30 to which the motor 3 is attached communicates with the inside of the rack housing H ₁ as shown in the figure, and a cylindrical belt is formed at the tip of the motor shaft 31 of the motor 3 protruding into the motor bracket 30. The pulley 40 is coaxially fitted and fixed.
[0023]
On the other hand, the rack shaft 1 supported inside the rack housing H ₁ is provided with a large-diameter portion 41 in which both sides of the communication position with the motor bracket 30 are increased in diameter over an appropriate length in the axial length direction. A belt groove 42 is formed on the outer peripheral surface of the large-diameter portion 41 in the form of a spiral V-groove inclined at a predetermined angle with respect to the axis of the rack shaft 1.
[0024]
The transmission means 4 wraps the transmission belt 43 around the belt pulley 40 and the belt groove 42 as described above, and stretches the transmission belt 43 between the motor shaft 31 and the rack shaft 1 under an appropriate tension. Configured. The transmission belt 43 has a V-shaped cross-sectional shape corresponding to the belt groove 42, and is wound around the belt groove 42 having a spiral shape so as to be fitted into the belt groove 42 a plurality of times. The pulley 40 is also wound around the outer peripheral surface a plurality of times.
[0025]
The transmission belt 43 as described above has a linear portion that is bridged between the motor bracket 30 and the rack housing H ₁ for communication between the belt pulley 40 and the belt groove 42, and these linear portions are connected to these linear portions. , each pair of guide rollers which are supported inside the rack housing H ₁ (guide means) 44 and 44, are brought into rolling contact from both sides in the width direction at as much as possible close positions to the rack shaft 1 .
[0026]
These guide rollers 44, 44 allow the transmission belt 43 to move in the axial direction of the rack shaft 1 while allowing the rotation of the transmission belt 43 between the belt pulley 40 and the belt groove 42 by their rolling. And a guide action for restricting the movement of the winding position of the transmission belt 43 around the belt groove 42 on the circumferential surface of the rack shaft. As a result, the transmission belt 43 can be rotated between the belt pulley 40 and the belt groove 42 without changing the winding position.
[0027]
The guide means of the transmission belt 43 can be constituted by, for example, a plate material, a bar, or the like that abuts on both sides in the width direction of the transmission belt 43, instead of the illustrated guide rollers 44, 44. By using the guide rollers 44, 44 that are in rolling contact with the roller 43, the resistance applied to the transmission belt 43 at these contact portions can be reduced, and a smooth and reliable operation can be performed.
[0028]
When the motor 3 is rotationally driven by the above configuration, the belt pulley 40 fitted to the motor shaft 31 rotates, and the transmission belt 43 wound around the belt pulley 40 is connected to the belt groove 42 on the outer periphery of the rack shaft 1. Rotate to circulate between.
[0029]
FIG. 3 is an operation explanatory view of the vehicle steering apparatus according to the present invention, in which a belt groove 42 on the outer periphery of the rack shaft 1 and a transmission belt 43 wound around the belt groove 42 are shown. As described above, the belt groove 42 on the outer periphery of the rack shaft 1 is a spiral concave groove inclined at a predetermined angle with respect to the shaft center. When the transmission belt 43 rotates, the belt groove 42 follows the inclination thereof. Is applied to the rack shaft 1, which is supported in the rack housing H ₁ so as to be movable in the axial length direction, by the axial force component F ₁ of the friction force F. Is applied to assist the steering performed as described above.
[0030]
At this time, the moving force (steering assist force) applied to the rack shaft 1 is changed by driving control of the steering assist motor 3. The drive control of the motor 3 is performed by, for example, using a control value determined based on a detection result of a steering torque applied to the column shaft 20 according to an operation of the steering wheel 21 as a detection result of a traveling state such as a vehicle speed, a yaw rate, a lateral acceleration, etc. This is performed according to a known control procedure for correcting based on the above. As a result, a steering assist force according to the steering situation is applied to the rack shaft 1, and the steering burden on the driver who operates the steering wheel 21 can be reduced and a good steering feeling can be experienced.
[0031]
In the vehicle steering apparatus according to the present invention, the transmission from the steering assisting motor 3 that is driven and controlled as described above to the rack shaft 1 includes the belt pulley 40 fitted to the motor shaft 31 of the motor 3, and the rack. This is realized by a transmission means 4 having a simple configuration including a spiral belt groove 42 formed on the outer peripheral surface of the shaft 1 and a transmission belt 43 wound around the spiral belt groove 42. In order to ensure this transmission, it is necessary to use a transmission belt 43 that is not stretchable in the length direction. For example, this type of transmission belt 43 has a large number of transmission blocks made of a resin material. It has been put to practical use by a structure formed by connecting thin metal belts having flexibility only in the direction.
[0032]
Further, the transmission belt 43 is wound around the belt pulley 40 and the belt groove 42 a plurality of times, and the friction force F is applied to the belt pulley 40 and the belt groove 42 in a distributed manner over the entire length of the winding length. Transmission from the motor 3 to the rack shaft 1 is reliably performed without causing the transmission belt 43 to slide on the circumference of the belt pulley 40 or the belt groove 42.
[0033]
Further, the transmission belt 43 is held between the guide rollers 44 in the vicinity of the rack shaft 1 and is restricted from moving in the axial direction, and the winding position is changed between the belt pulley 40 and the belt groove 42. The rotation of the motor 3 can be reliably transmitted to the rack shaft 1.
[0034]
In the above embodiment, the application example to the rack and pinion type electric power steering apparatus including the rack shaft 1 as the steering shaft has been described. However, the present invention is directed to steering that moves in the axial direction for steering. Needless to say, the present invention is applicable to any type of electric power steering apparatus that includes a shaft and is configured to assist the movement of the steering shaft by the generated force of the motor.
[0035]
Further, the present invention provides a steering apparatus having a structure in which a steering member such as a steering wheel is mechanically separated from a steering mechanism, and steering is performed only by a rotational force of a motor driven in accordance with an operation of the steering member. It can also be applied to a so-called steer-by-wire type steering apparatus.
[0036]
【The invention's effect】
As described above in detail, in the vehicle steering apparatus according to the first aspect of the present invention, the belt pulley fixed to the motor shaft, the transmission means from the motor driven in response to the operation of the steering member to the steering shaft, This can be realized by a simple configuration in which a transmission belt is stretched between a helical belt groove formed on the outer peripheral surface of the steering shaft.
[0037]
In the vehicle steering system according to the second aspect of the invention, since the transmission belt is wound around the belt pulley and the belt groove a plurality of times, the frictional force is distributed over the entire length of the winding length, which causes the transmission belt to slip. It is possible to perform reliable transmission without the need for transmission.
[0038]
Further, in the vehicle steering apparatus according to the third aspect of the invention, the winding position of the transmission belt can be maintained by the action of the guide means, and the rotation of the motor can be reliably transmitted to the rack shaft. Excellent effect.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an overall configuration of a vehicle steering apparatus according to the present invention.
FIG. 2 is a longitudinal sectional view showing a schematic configuration of a transmission means from a steering assist motor to a rack shaft.
FIG. 3 is an operation explanatory view of the vehicle steering apparatus according to the present invention.
[Explanation of symbols]
1 Rack shaft (steering shaft)
2 Pinion shaft 3 Motor 4 Transmission means
21 Steering wheel (steering member)
31 Motor shaft
40 belt pulley
42 Belt groove
43 Transmission belt
44 Guide roller (guide means)
H ₁ rack housing H ₂ pinion housing

Claims (3)

In a vehicle steering apparatus that transmits a rotational force of a motor driven in accordance with an operation of a steering member to a steering shaft in a steering mechanism, and moves the steering shaft in an axial length direction to perform steering.
A belt pulley coaxially fixed to the motor shaft of the motor;
A belt groove formed in a spiral shape on the outer peripheral surface of the steering shaft;
A vehicle steering apparatus comprising: a transmission belt wound around the belt groove and the belt pulley and stretched between the steering shaft and the motor shaft. The vehicle steering apparatus according to claim 1, wherein the transmission belt is wound around the belt groove and the belt pulley a plurality of times. 3. The vehicle according to claim 1, further comprising a guide unit that acts on the transmission belt in a vicinity of a position where the belt groove is wound, and restricts movement of the transmission belt in the axial direction of the steering shaft. Steering device.

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