JP2002308123A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device capable of preventing generation of large operation sound and hammering sound. SOLUTION: This electric power steering device is provided with a ball nut surrounding a rack shaft 1, and a power assisting electric motor for rotating the ball nut through a rotation reduction means having a plurality of gears. The working face of at least one of the above gears is formed of a synthetic resin.

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 for a vehicle, and more particularly, to an electric power steering apparatus employing a deceleration method using a ball screw nut.

[0002]

2. Description of the Related Art Conventionally, a vehicle steering device (steering device) includes a manual type and a power assist type, and the latter reduces a manual force by assisting a manual steering force with some power. Is what you do. This power assisted steering device includes an electric type and a hydraulic type.

[0003] The former electric type is called an electric power steering device. Among them, an electric power steering device with a speed reduction mechanism using a ball screw nut is disclosed in, for example, Japanese Patent Publication No. 6-504. FIG. 4 shows a sectional configuration thereof. In the figure, a first gear 21 is fixed to a rotation shaft of a motor 22, a second gear 32 a integrally formed with a ball screw nut 32 meshes with the first gear 21, and the ball screw nut 32 is Are rotatably supported via a bearing 28. The ball screw nut 32 has a thread groove 32 b of the nut 32 and the ball 2.
The rack shaft 33 in which the thread groove 33b that indirectly engages through the rack shaft 33 is formed. A rack 33a is formed on the left side of the thread groove 33b of the rack shaft 33 in the figure, and meshes with a pinion gear 36 to which rotation of the handle 35 is transmitted via a steering shaft.

[0004]

However, in the above-mentioned conventional ball screw type electric power steering apparatus, the reduction gears such as the first gear 21, the second gear 32a and the ball screw nut 32 are combined with each other. Since the mechanism is employed, a loud operation noise is generated by sliding of a contact portion such as a metal. In particular, when the gear is a steel reduction mechanism, there is a problem that a tapping sound is generated due to a gap between the teeth, which may cause discomfort to the driver of the vehicle.

An object of the present invention is to provide an electric power steering apparatus which can solve the above-mentioned disadvantages of the conventional example and can prevent generation of loud operation noise and tapping noise.

[0006]

In order to achieve the above object, according to the present invention, there is provided a rotating shaft means connected to a steering wheel and rotating with the steering wheel, and capable of linearly moving in the opposite direction for steering a steered wheel. An elongate member, a pinion gear that is drivingly connected to the rotating shaft means and the elongate member, and that rotates according to the rotating shaft means, and is provided at a first axial position of the elongate member; Rack and pinion means comprising a rack gear meshing with the pinion gear;
Screw means provided at a second axial position of the elongated member, nut means surrounding at least a part of the screw means, and a number of balls interposed between the screw means and the nut means A ball screw means comprising: an elongate member, an electric motor unit disposed with a different axis, and a rotation of an output shaft of the electric motor unit being reduced and transmitted to a nut means of the ball screw means. An electric power steering apparatus having at least two meshing elements, wherein at least one of the elements of the rotation reducing means is in contact with another element. Provides an electric power steering apparatus characterized by being formed of a synthetic resin. Further, the electric power steering apparatus according to the present invention is characterized in that at least one of the components of the rotation reduction means is bonded by a chemical bond using an in-metal bonding composite technique or an adhesive. And Further, the electric power steering apparatus according to the present invention is characterized in that the meshing contact surface of the synthetic resin is formed on a smooth surface that is easy to slide. Furthermore, in the present invention, the rotating shaft means connected to the handle and rotating with the handle, a long member linearly movable in the opposite direction to perform steering of the steered wheels, the rotating shaft means and the long member, A rack and pinion means comprising a pinion gear that is drivingly connected and rotates according to the rotary shaft means, and a rack and pinion means provided at a first axial position of the elongated member and meshing with the pinion gear; A screw means provided at a second axial position of the measuring member, a nut means surrounding at least a part of the screw means, and a number of balls interposed between the screw means and the nut means. A ball screw means, an elongate member, and an electric motor unit arranged on a different axis. And an engagement-type rotation reduction device having three engagement elements for transmitting the rotation to the nut means of the screw screw means. An electric power steering device is provided, wherein a part of the element of the (middle gear) in contact with the gear, which is in contact with another element, is formed of a synthetic resin. Further, the electric power steering apparatus according to the present invention is characterized in that the resin of the middle element is joined by chemical bonding by an in-metal bonding composite technique or bonding by an adhesive.

[0007] With the above configuration, the synthetic resin absorbs vibration when the two meshing elements come into contact with each other, and the vibration is suppressed by the good slidability of the surface thereof. The generation of operating noise during driving and the generation of tapping noise due to gaps between these elements are prevented.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional configuration view of an electric power steering apparatus according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line BB of FIG. 1 showing a gear arrangement of a rotation reduction unit, and FIG. 3 is a second embodiment of the present invention. It is a longitudinal cross-sectional view which shows the gear arrangement of the rotation reduction means which shows a form.

In FIG. 1, a pinion gear 6 is fixed to a shaft 12 (see FIG. 2) separate from the output rotation shaft on the same axis as the output rotation shaft of a brushless electric motor 5 which is an electric motor unit. Is engaged with the reduction gear 2.

The reduction gear 2 is externally fitted to a nut-shaped ball screw nut 3 or is formed integrally therewith. The ball screw nut 3 is rotatably supported by the housing 7 via bearings 8 and 8 and a nut damper 13, and is provided with the rack shaft 1 fitted therein, that is, around the rack shaft 1. The rack shaft 1 is formed with a thread groove 1b that indirectly engages with the thread groove 3a of the ball screw nut 3 via the ball 4. That is, the ball screw nut 3 and the rack shaft 1 are
a and a plurality of spherical balls 4 which are rotatably fitted into the valleys of the thread groove 1b.
The ball screw nut 3 is externally fitted to a part of the shaft in the axial direction. The ball screw nut 3 and the ball 4 constitute a known ball screw or ball screw. The pinion gear 6, the reduction gear 2, and the ball screw nut 3 constitute a rotation reduction unit, and the thread groove 1b, the ball screw nut 3, and the ball 4 constitute a ball screw unit. Housing 7
A rack stroke damper 14 is provided at one end of
When the housing 7 and the ball joint collide at the rack end, energy is dissipated.

The electric motor 5 includes a stator (not shown), a rotor having a rotating shaft (not shown), and the like. In this embodiment, the electric motor 5 is arranged in an axial direction substantially parallel to the rack shaft 1. ing. The electric motor 5 may be arranged at an appropriate inclination depending on the installation space. One end of the rack shaft 1 is connected to a tie rod 15 via a universal joint 9.

In the figure of the rack shaft 1, a rack 1a is formed at the left side portion (tip) of the thread groove 1b. The rack 1a is externally fixed to a pinion shaft 10 connected to a lower end of a steering shaft (not shown) connected to a handle (not shown), and is housed in a pinion gear box 11 (not shown). And are engaged. The rotating shaft means is constituted by the steering shaft and the pinion shaft 10, and the rack and pinion means is constituted by the rack 1a and the pinion gear. The rack and pinion means itself is a known means for drivingly connecting the rotating shaft means and the rack shaft 1.

As shown in FIG. 2, the pinion gear 6 fixed to the rotating shaft of the electric motor 5 has its entire teeth or the gear surface formed of a synthetic resin 6a (hatched portion). The synthetic resin 6a has a predetermined elasticity, and its meshing surface is formed on a smooth surface that is easy to slide.

In the case of the pinion gear 6, only the gear surface 6a is made of synthetic resin and the core is made of metal.
Is bonded by an in-mold bonding and compounding technology, for example, by a TRI (tri) system by Toa Denka. At the stage when this bonding is completed, a gear whose entire tooth surface is made of resin 6a is formed. Finish by machining.

The above-mentioned TRI system is a technology for joining a metal such as an aluminum alloy or a copper alloy and a plastic in a mold by chemical bonding by applying electrochemical special metal surface treatment and insert injection molding. Since no adhesive is used, fine parts can be freely designed.

[0016] The core metal and the resin 6a by this TRI system
First, the tooth surface (entire outer peripheral surface) of the cored bar is subjected to an organic plating treatment, and a chemical reaction is caused in the interior immediately below the tooth surface. Next, insert this core into the injection mold,
The molten resin is injected into the same mold, and insert molding is performed, whereby the resin 6a is joined to the tooth surface of the cored bar.

The operation in the above configuration will be briefly described. Although the electric motor 5 is controlled based on information such as the torque applied to the steering wheel by the driver or the vehicle speed, a detailed description of the control circuit is omitted because it is not directly related to the present invention. The control device controls the output of the electric motor 5 so as to obtain an appropriate assisting force according to the detected torque and vehicle speed.

When the pinion gear 6 of the electric motor 5 meshes with the reduction gear 2, the generated vibration is absorbed by the elasticity of the synthetic resin 6a, and the vibration is suppressed by the good slidability due to the smooth surface. For this reason, no operating noise is generated due to the meshing of the gears, and the generation of the gear tapping noise due to the gap between the teeth is sufficiently prevented.

The rotation shaft of the electric motor 5 and the shaft of the pinion gear 6 are connected. In this case, the rotation of the pinion gear 6 is transmitted to the ball screw nut 3 via the reduction gear 2 to rotate the ball screw nut 3, and the rack shaft 1 is driven in any direction of the arrow A by this rotation. Steering of the steered wheels is performed. At this time, the torque of the steering shaft and the vehicle speed corresponding to the load applied to the rack shaft 1 are detected, and the output of the electric motor 5 is controlled in accordance with the detected values. It is added as appropriate.

In this embodiment, only the teeth of the pinion gear 6 are formed of resin. However, the present invention is not limited to this configuration. Only the reduction gear 2 meshing with the pinion gear 6 or both teeth are formed of resin. It may be formed. In short, of at least one of the gears of the rotation reduction unit,
A desired effect can be expected if at least a portion that meshes with the other gear is formed of a synthetic resin.

Next, a second embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. The second embodiment is different from the first embodiment in that the rotation reducing means for transmitting the rotation from the output pinion gear 6 of the electric motor unit 5 to the nut-shaped ball screw nut 3 is different from the first embodiment. In contrast to the two components of the pinion gear 6 and the reduction gear 2 meshing with the pinion gear 6, the second embodiment includes an intermediate gear 18 interposed between the pinion gear 6 and the reduction gear 2. It consists of three elements. Therefore, in FIG. 3, the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the second embodiment, all or any two of the three elements constituting the rotation reduction means can be made of synthetic resin. Preferably, the middle stage, that is, the entire intermediate gear 18 or the gear surface is made of synthetic resin. Just do it. When only the gear surface is made of a synthetic resin, it is preferable to adopt TRI bonding as in the first embodiment. Thus 3
If only the middle stage of the two elements is made of synthetic resin, gear noise such as tapping sound and operation noise can be reduced at lower cost. Also,
When TRI bonding is employed as in the first embodiment and the second embodiment, the strength of the obtained resin gear is improved as compared with the conventional resin gear, so that the outer diameter of the gear can be reduced. Therefore, the center distance between the electric motor 5 and the long member as the rack shaft 1 can be reduced.

[0023]

As described above, according to the present invention,
Of the meshing elements of the rotation reduction means, at least one of the elements in contact with the other element is formed of a synthetic resin, so that vibration at the time of meshing is absorbed by the resin, and the sliding property is good. Vibration is suppressed, and generation of operation noise and generation of tapping noise due to the gap between the meshing elements can be sufficiently prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of an electric power steering device according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line BB of FIG. 1 showing the gear arrangement of the rotation reduction unit.

FIG. 3 is a longitudinal sectional view showing a gear arrangement of a rotation reduction unit according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional configuration diagram of a conventional electric power steering device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rack shaft 1a Rack gear 1b, 3a Thread groove 2 Reduction gear 3 Ball screw nut 4 Ball 5 Electric motor unit 6 Pinion gear (motor side) 6a Resin 7 Housing 8 Bearing 18 Intermediate gear

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Osamu Tatewaki 78 Toba-cho, Maebashi-shi, Gunma Nippon Seiko Co., Ltd. Reference) 3D033 CA02 CA04 3J009 DA11 EA04 EA11 EA21 EA32 EB08 FA08 3J030 AA03 BA01 BC03 BC10 CA10 3J062 AA01 AB22 BA25 BA26 CD02 CD23 CD57

Claims (5)

[Claims] 1. A rotating shaft means connected to a steering wheel and rotating together with the steering wheel, an elongate member capable of linearly moving in the opposite direction to steer a steered wheel, and driving the rotating shaft means and the elongate member. A pinion gear, which is connected to the rotating shaft means, and a rack and pinion means provided at a first axial position of the elongated member and meshes with the pinion gear; A screw means provided at a second axial position of the member; nut means surrounding at least a part of the screw means; and a number of balls interposed between the screw means and the nut means. A ball screw means, an electric motor unit disposed so that the elongate member has an axis different from that of the elongate member; In order to transmit to the nut means clew means,
An electric power steering device comprising: at least two meshing elements; and an engagement type rotation reduction device including: at least two engagement elements, wherein at least one of the elements of the rotation reduction means is in contact with another element. An electric power steering device characterized by being formed of resin. 2. A method according to claim 1, wherein the resin of at least one of the elements of the rotation reduction means is bonded by chemical bonding by an in-metal bonding composite technique or bonding by an adhesive. Electric power steering device. 3. An electric power steering apparatus according to claim 1, wherein said meshing contact surface of said synthetic resin is formed on a smooth surface which is easy to slide. 4. A rotating shaft means connected to the steering wheel and rotating together with the steering wheel; an elongate member capable of linearly moving in the opposite direction to steer the steered wheels; and driving the rotating shaft means and the elongate member. And a pinion gear, which is rotatably connected with the rotating shaft means, and a rack and pinion means provided at a first axial position of the elongated member and meshes with the pinion gear; A screw means provided at a second axial position of the member; nut means surrounding at least a part of the screw means; and a number of balls interposed between the screw means and the nut means. A ball screw means, an electric motor unit arranged with a different axis from the elongate member, and a ball that reduces the rotation of an output shaft of the electric motor unit. In order to transmit to the nut means clew means,
An electric power steering apparatus comprising: a meshing type rotation reducing means having three meshing elements; and an electric power steering apparatus comprising: 2. The electric power steering apparatus according to claim 1, wherein a contact portion with another element is formed of a synthetic resin. 5. The electric power steering apparatus according to claim 4, wherein the resin of the middle element is joined by chemical bonding using an in-metal bonding composite technique or bonding with an adhesive.