JP2003300470A - Motor-driven power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve installing accuracy, and to improve assembling efficiency. <P>SOLUTION: A motor-driven power assist part 5 is arranged in a place different from a place for arranging a pinion gear 91 connected to a steering wheel. A transmission mechanism 1 for playing a role of transmitting motive power from an electric motor 3 for forming the power assist part 5 is composed of a bevel gear mechanism. This motor-driven power steering device is provided with a driving bevel gear 11 connected to the electric motor 3 side, and a driven bevel gear 21 for meshing and engaging with the driving bevel gear 11. The driven bevel gear 21 has a tooth part 211 for meshing and engaging with a tooth part 111 of the driving bevel gear 11, and has a shaft-like part 212 integrally formed with a holding member 622 of a ball nut 62. These gears are integrally formed of the same member. The shaft-like part 212 is supported by a pair of taper roller bearings 7 and 7' with a thrust plate 4 interposed between taper roller bearings. <P>COPYRIGHT: (C)2004,JPO

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 having a power assist section driven by an electric motor, and more particularly to a steering apparatus having a rack and pinion type gear mechanism for the power assist section. The present invention relates to an electric power steering device which is adopted in the above and uses a bevel gear mechanism as a mechanism for transmitting the power from the electric motor to the rack bar.

[0002]

2. Description of the Related Art As an electric power assist device in a conventional steering device having a rack and pinion type gear mechanism, there is, for example, one described in Japanese Patent Laid-Open No. 2001-315655. In this case, the driven bevel gear and the shaft-shaped member for transmitting torque to the ball screw mechanism are separate members, which are connected by a key or a spline. A pair of bearings are provided on the outer diameter side of the shaft-shaped member with a predetermined space therebetween, and the bearings are held by the housing. Therefore, in the above-mentioned conventional one, in order to receive the thrust force applied to the driven bevel gear and the nut bearing on the ball screw side which is connected to the driven bevel gear and is made of a shaft-shaped member, the nut bearing has a predetermined shape. The bearings installed with the interval of
One is to be engaged at the shoulder of the cylindrical housing that houses the rack bar,
The bearing on the other side is adapted to be engaged at a stepped shoulder provided on a part of the nut bearing. And each of these bearings
Each of the inner races is fitted to the outer diameter portion of the nut bearing, and one of the outer races is mounted in the cylindrical housing, and the other one is mounted on the other side. It is designed to be installed inside a ring-shaped attachment part.
Then, the outer peripheral surface of such an attachment part is mounted in the housings on the driving bevel gear side and the driven bevel gear side in a cage-like shape, and from the bevel gear mechanism by interposing such a plurality of cage-causing engagement portions. The transmission mechanism portion is formed.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In this conventional one, it is necessary to increase the precision of the printing basket mating portions at the above-mentioned plural places in order to improve the assembling precision and the meshing precision of the bevel gear mechanism portion, and it is said that the assembling workability is not good. There is a problem. In order to solve such a problem, a shaft-shaped member that is responsible for transmitting torque between the driven bevel gear and the ball screw mechanism and is provided coaxially with the rack bar is provided between the thrust members. A pair of bearings should be used with the plate interposed, and the housing for housing the pair of bearings and the housing for housing the drive bevel gear need not be connected by using a printing mating means. It is an object (problem) of the present invention to provide an electric power steering device having the above configuration.

[0004]

In order to solve the above-mentioned problems, the following measures are taken in the present invention. That is, in the invention of claim 1, the rack and pinion gear mechanism is formed on the basis, and the pinion gear connected to the steering shaft is provided on one side of the rack bar forming the rack and pinion gear mechanism. And an electric power steering device in which a power assist unit mainly including an electric motor is installed in a place different from the place where the pinion gear is installed. The transmission mechanism for transmitting the power from the electric motor to the rack bar side via the ball screw mechanism is composed of a bevel gear mechanism, and the bevel gear mechanism is connected to the electric motor side. A drive bevel gear and a driven bevel gear that meshes with the drive bevel gear in a predetermined state. Furthermore, the shaft-shaped member formed to bear torque between the driven bevel gear and the ball nut forming the ball screw mechanism is supported by a pair of bearings, and a predetermined distance is provided between the bearings. A thrust plate having a thickness is provided, and a housing for holding the driving bevel gear and a housing for holding the driven bevel gear are joined to each other at flange portions thereof, and one of the thrust plates is provided therebetween. It has been decided to adopt a configuration in which a predetermined fastening means is used to couple the parts with the parts interposed.

By adopting such a configuration, in the invention of the present invention, since the seal mating portion is not formed in the fitting portion of the bearing or the fitting portion of the housing, the bevel gear mechanism portion forming the transmission mechanism is formed. It is possible to improve the assembling accuracy and the meshing accuracy. Specifically, a shaft-shaped member formed to transfer torque between a driven bevel gear and a ball nut is supported by a pair of bearings with a thrust plate interposed therebetween, and A sub-assembly such as a bevel gear and a rack bar is housed in a housing on the driven bevel gear side, and the driven bevel gear side housing is placed with the thrust plate interposed therebetween. The power assist section is formed by bringing the driving bevel gears to the housings, joining the flanges formed on the respective housings, and joining the flanges with a predetermined fastening means. I am trying to let you. Therefore, according to the present invention, the assembling work of the bevel gear mechanism portion can be performed without going through the printing work between the housings as in the conventional one. It is possible to improve the meshing accuracy. Further, it becomes possible to install the pair of bearings at a position close to the bevel gear mechanism side with the thrust plate interposed, thereby making it possible to reduce the housing diameter around the ball nut. As a result, the size of the entire device can be reduced. Therefore, a space can be secured around the transmission mechanism section. In addition, the backlash of the bevel gear mechanism can be adjusted in the sub-assembly state on the driven bevel gear side, and the backlash adjustment work can be smoothly performed.

Next, the invention according to claim 2 will be described. This one is also the same as the one described in claim 1 in the basic point. That is, according to the present invention, in the electric power steering apparatus according to claim 1, the driven bevel gear has a tooth portion that meshes with a tooth portion of the drive bevel gear, and with respect to the rack bar. It is provided coaxially and has a shaft-shaped portion integrally formed with a ball nut forming a ball screw mechanism or a holding member thereof, and these tooth portions and the shaft-shaped portion are integrally formed by the same member. It was decided to adopt a configuration adapted to be formed in.

By adopting such a structure, in the present invention, the tooth portion forming the driven bevel gear and the shaft portion are integrally formed, and the shaft portion is Since the extended portion is also integrated with the ball nut or the holding member that holds the ball nut, the diameter of the shaft-shaped portion can be reduced as a whole. Further, it is possible to improve the assembling accuracy and the meshing accuracy of the bevel gear mechanism portion forming the transmission mechanism. Also, the number of parts can be reduced.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 2, the present embodiment is based on a rack-and-pinion type gear mechanism, and includes a steering gear mechanism 9 and a power assist unit 5 mainly including an electric motor 3. And relates to an electric power steering device set so as to be provided in different places.
The specific configuration of the power assist unit 5 is shown in FIG.
As shown in FIG. 6, the ball nut 62 is provided at the rack bar 6 forming the steering gear device and is integrally formed with the ball nut 62 forming the ball screw mechanism 66 or the holding member 622 holding the ball nut 62. Driven bevel gear 21 having a shaft-shaped portion 212 and a tooth portion 211 integrally formed of the same member as the shaft-shaped portion 212, and a drive bevel gear that meshes with the driven bevel gear 21. 11 and an electric motor 3 connected to the rotary shaft of the drive bevel gear 11 via a predetermined joint mechanism. That is, in the present embodiment, the bevel gear mechanism is adopted as the transmission mechanism 1 that serves to transmit the power from the electric motor 3 forming the power assist portion 5 to the rack bar 6. ing. As the bevel gear mechanism adopted in the present embodiment, there is an oblique bevel gear mechanism having a predetermined inclination angle where the crossing angle is not a right angle, but this bevel gear mechanism has a crossing angle of 90 °. The miter gear mechanism of is also included. Further, examples of the bevel gear include a straight bevel gear, a spiral bevel gear, and a Zellore bevel gear.

As shown in FIG. 2, the power assist unit 5 having such a structure is different from the position (position) of the rack and pinion type gear mechanism 9 where the pinion gear 91 connected to the steering shaft is provided. It is designed to be provided at the location (position). In particular, in the present embodiment, the pinion gear 91 and the power assist portion 5 are on the axis of the rack bar 6 forming the rack and pinion type gear mechanism 9, and have substantially symmetrical positions in plan view. In addition, each of them is provided. By adopting such an arrangement configuration, the power assist unit 5
Can be provided at a position away from the place where the pinion gear 91 is installed in a state where left and right balance is maintained, and the structure around the pinion gear 91 in which various parts related to the steering gear mechanism are concentrated can be simplified. Will be able to.

Next, the power assist unit 5 of the present embodiment having such a configuration will be described. As shown in FIGS. 1 and 2, the specific structure is such that it is connected to the rotating shaft of the electric motor 3 through a predetermined joint mechanism such as an Oldham shaft joint and forms the transmission mechanism 1. A drive bevel gear 11 including a bevel gear,
A ball nut 62, which meshes with the tooth portion 111 of the drive bevel gear 11 to form the transmission mechanism 1 and forms a ball screw mechanism 66 with respect to the rack bar 6, is integrally formed coaxially with the ball nut 62. And a driven bevel gear 21 provided in the. The driven bevel gear 21 has a shaft-shaped portion 212 integrally formed on an extension of the holding member 622 that holds the ball nut 62, and is integrally formed of the same member as the shaft-shaped portion 212. The tooth portion 211 is formed.

Specifically, the driven bevel gear 21 has a ring shape as shown in, for example, FIG. 1, and has a tooth portion 211 which meshes with a tooth portion 111 of the drive bevel gear 11. And a shaft portion 212 which is integrally formed on an extension of a holding portion or a holding member 622 which holds the ball nut 62 and which is provided coaxially with the rack bar 6. The shaft-shaped portion 212 and the tooth portion 211 are integrally formed on the basis of an iron-based metal material by cold forging means or the like.

Further, the ring-shaped tooth portion 2 at the shaft-shaped portion 212 of the driven bevel gear 21 having such a structure.
As shown in FIG. 1, a pair of taper roller bearings 7 and 7 ′ are mounted on the rear surface side of 11 through a spacer 215 having a predetermined thickness. Then, the pair of tapered roller bearings 7,
Reference numeral 7'denotes an inner race 71, 71 'fitted on the outer side of the shaft-like portion 212, outer races 72, 72' mounted on the respective flange portions 155, 255 of the housings 15, 25, and these inner races. Race 71, 71 '
And the outer races 72, 72 'and the taper rollers 77, 77' mounted with a predetermined inclination angle.
And consists of. The thrust plate 4 having a predetermined thickness is provided between the tapered roller bearings 7 and 7 ′ having the above-described structure, specifically, between the outer races 72 and 72 ′. ing. Further, the thickness of the spacer 215 is set so that the axial line of the rack bar 6 and the driving bevel gear 1 in the state where the main bevel gear mechanism forming the transmission mechanism 1 is assembled as shown in FIG.
The intersection (O) with the axis 1 is set at a predetermined position. Then, in the state where the pair of taper roller bearings 7 and 7 ′ are assembled with the thrust plate 4 sandwiched therebetween on the shaft-shaped portion 212 forming the driven bevel gear 21, finally, the predetermined fastening is performed. By tightening the nut 79, the work of mounting the tapered roller bearings 7 and 7 ′ on the shaft-shaped portion 212 forming the driven bevel gear 21 is completed. It should be noted that, with respect to the above-mentioned bearing having such a configuration, the tapered roller bearings 7 and 7'are adopted in the present embodiment, but the present invention is not limited to this, and other than this. ,
A pair of angular contact bearings or a pair of ball bearings are also conceivable.

Next, the assembling procedure of the present embodiment having the above structure will be described with reference to FIG. First, the driven bevel gear having the ball nut 62 forming the ball screw mechanism 66 around the rack bar 6 and having the shaft-like portion 212 integrally formed with the holding member 622 holding the ball nut 62. Two
1 is attached coaxially to the rack bar 6 by holding the shaft portion 212. In such a state, the ring-shaped tooth portion 21 on the shaft-shaped portion 212 is formed.
A pair of taper roller bearings 7 and 7 ′ are attached to the shoulder portion formed on the back surface side of 1 through a spacer 215 having a predetermined thickness. The thrust plate 4 is placed between the pair of tapered roller bearings 7 and 7 '.
To intervene. Specifically, first, the inner race 71 of the one tapered roller bearing 7 is fitted to the shaft-shaped portion 212 with the spacer 215 interposed at the rear surface side of the tooth portion 211. As a result, one taper roller bearing 7 is attached to the shaft-shaped portion 2
It is attached to 12. Then, the taper roller bearing 7 ′ on the other side is attached to the outer race 72 of the taper roller bearing 7 with the thrust plate 4 having a predetermined thickness interposed therebetween. Specifically, while the outer race 72 ′ on the other side is in contact with the thrust plate 4, the inner race 71 ′ on the other side is fitted to the shaft portion 212. Then, in such a state, the inner race 71 ′ on the other side is axially tightened with a predetermined fastening nut 79. This completes the work of mounting the taper roller bearings 7 and 7 '.

Next, in the sub-assembly state in which the main ball screw mechanism 66, the driven bevel gear 21 and the pair of taper roller bearings 7 and 7'are mounted around the rack bar 6 in this manner, the driven bevel gear is used. It is mounted in the side housing 25. Specifically, the outer race 72 ′ of the taper roller bearing 7 ′ on the other side is fitted into the housing 25 on the driven bevel gear side. Then, next, at the flange portion 255 of the driven bevel gear side housing 25 in which the driven bevel gear 21 and the rack bar 6 and the like are mounted, the driving bevel gear side housing 15 in which the driving bevel gear 11 is mounted is held. Go to each flange 1
55 and 255 are joined together with the thrust plate 4 interposed therebetween. And further, each of the flange portions 15
Tighten the parts at 5, 255 using a predetermined fastening means 8. As a result, the both 155 and 255 are jointly fixed and fixed together with the thrust plate 4. At this time, since the thicknesses of the thrust plate 4 and the spacer 215 are set to appropriate values in advance, the fastening work of the fastening means 8 causes
The intersection point position (O) of the shaft centers of the bevel gears 11 and 21 forming the transmission mechanism 1 is automatically set to a predetermined planned position. The backlash of the bevel gear mechanism forming the transmission mechanism 1 at this time is adjusted to an optimum state by selecting the thickness of the spacer 215 to an appropriate value in the subassembly state. Become.

Further, in the present embodiment, the shaft-shaped portion 212 of the driven bevel gear 21 is supported by the pair of tapered roller bearings 7 and 7 ', and the pair of tapered roller bearings 7 and 7'is provided. A thrust plate 4 having a predetermined thickness is provided between the outer races 72, 72 'of the bearings forming the roller bearings 7, 7', and further, the drive bevel gear housing 15 for holding the drive bevel gear 11 is provided. The driven bevel gear-side housing 25 holding the driven bevel gear 21 is joined to the flange portions 155 and 255 provided on the driven bevel gear side housing 25, respectively, and the thrust plate 4 is partly interposed between them. Since the configuration is such that the fastening means 8 is used for coupling, the assembling precision and the biting of the bevel gears forming the transmission mechanism portion 1 are set. Gastric accuracy, it is possible to improve by a simple assembly operation. Specifically, as shown in FIG. 1, while adjusting the thickness of the thrust plate 4 installed between the pair of tapered roller bearings 7 and 7'supporting the shaft-shaped portion 212 of the driven bevel gear 21 to an appropriate value, The driven bevel gear 21 on which the bearings 7 and 7'are mounted, and further, the driven bevel gear side in which the driven bevel gear 21 and the rack bar 6 are integrally assembled in a sub-assembly state are incorporated. The housing 25 is brought to the housing 15 on the side of the driving bevel gear with the thrust plate 4 interposed therebetween, and the flange portion 1 formed on each of the housings 15 and 25.
Since the power assist portion 5 is formed by joining 55 and 255 together and further joining the flange portions with a predetermined fastening means 8, it is possible to form a seal between the housings as in the conventional one. Therefore, it is possible to improve the radial assembling accuracy of the driven bevel gear 21 and the meshing accuracy of the bevel gear mechanism portion. In addition, a pair of taper roller bearings 7 and 7'is provided between the thrust plate 4 and
It becomes possible to install it at a position close to the transmission mechanism 1 side with the intervening position, thereby making it possible to reduce the housing diameter around the ball nut 62. As a result, the size of the entire device can be reduced. In addition, a space can be secured around the transmission mechanism 1. Further, the backlash adjustment of the bevel gear mechanism portion forming the transmission mechanism 1 and the like are performed in the sub-assembly state on the driven bevel gear 21 side and by adjusting the spacer 215. Will be done efficiently.

[0016]

According to the present invention, a rack and pinion type gear mechanism is formed as a basis, and a pinion gear connected to a steering shaft is provided on one side of a rack bar forming the rack and pinion type gear mechanism. And an electric power steering device in which a power assist unit mainly including an electric motor is installed in a place different from the place where the pinion gear is installed. The transmission mechanism for transmitting the power from the electric motor to the rack bar side via the ball screw mechanism is composed of a bevel gear mechanism, and the bevel gear mechanism is connected to the electric motor side. It consists of a driving bevel gear and a driven bevel gear that meshes with the driving bevel gear in a predetermined state. In addition, a shaft-shaped member formed to bear torque between the driven bevel gear and the ball nut forming the ball screw mechanism is supported by a pair of bearings and has a predetermined thickness between the bearings. And a housing for holding the drive bevel gear and a housing for holding the driven bevel gear, the flange portions respectively provided on the housing are joined, and a part of the thrust plate is provided therebetween. Since the structure is such that the intervening state is coupled by using a predetermined fastening means, the assembly work of the bevel gear mechanism section does not have to go through the laying work between the housings as in the conventional one. As a result, it is possible to improve the assembling accuracy and meshing accuracy of the bevel gear mechanism portion that forms the transmission mechanism. It became. Further, since the pair of bearings are arranged near the base of the driven bevel gear, the housing diameter around the ball nut can be reduced. As a result, an extra space can be formed around the transmission mechanism.

Further, the driven bevel gear has a tooth portion that meshes with and engages with the tooth portion of the driving bevel gear, and is provided coaxially with the rack bar and forms a ball screw mechanism. Alternatively, since the holding member has a shaft-shaped portion integrally formed, and the tooth portion and the shaft-shaped portion are integrally formed by the same member, the driven umbrella is While the tooth portion and the shaft-shaped portion forming the gear are now integrally formed,
The shaft-shaped portion is such that the extension thereof is integrated with the ball nut or the holding member that holds the ball nut, so that the diameter of the shaft-shaped portion can be reduced as a whole. As a result, an extra space can be formed around the transmission mechanism. Further, the assembling accuracy and the meshing accuracy of the bevel gear mechanism portion forming the transmission mechanism can be improved. Moreover, it has become possible to reduce the number of parts.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an overall configuration around a power assist section and a transmission mechanism section which are main parts of the present invention.

FIG. 2 is an external view showing the overall configuration of the present invention.

[Explanation of symbols]

1 Transmission mechanism 11 Drive bevel gear 111 teeth 15 Housing (drive bevel gear side housing) 155 flange 21 Driven bevel gear 211 Tooth 212 Shaft 215 spacer 25 Housing (driven bevel gear side housing) 255 flange 3 electric motor 4 Thrust plate 5 Power assist section 6 rack bars 62 ball nut 622 holding part (holding member) 66 ball screw mechanism 7 Tapered roller bearing 7'Taper roller bearing 71 Inner Race 71 'inner race 72 outer race 72 'outer race 77 Taper roller 77 'taper roller 8 fastening means 9 Rack and pinion gear 91 pinion gear

Claims (2)

[Claims] 1. A rack and pinion type gear mechanism is formed as a base, and a pinion gear connected to a steering shaft is installed on one side of a rack bar forming the rack and pinion type gear mechanism. In an electric power steering device in which a power assist unit mainly formed of an electric motor is installed in a place different from the place where the pinion gear is installed, the power assist unit is formed and the power assist unit is formed from the electric motor. The transmission mechanism that plays a role of transmitting the power of the above to the rack bar side via the ball screw mechanism is composed of a bevel gear mechanism, and the bevel gear mechanism is a drive bevel gear connected to the electric motor side and the drive. A driven bevel gear that meshes with the bevel gear in a predetermined state. A thrust plate having a predetermined thickness is supported by a pair of bearings, which supports a shaft-shaped member formed so as to transmit torque between a bevel gear and a ball nut forming a ball screw mechanism. A state in which a housing for holding the drive bevel gear and a housing for holding the driven bevel gear are joined to flange portions provided respectively, and a part of the thrust plate is interposed therebetween. The electric power steering device is characterized in that it is connected by using a predetermined fastening means. 2. The electric power steering apparatus according to claim 1, wherein the driven bevel gear has a tooth portion that meshes with a tooth portion of the drive bevel gear, and is coaxial with the rack bar. A ball nut that forms a ball screw mechanism or has a shaft-shaped portion integrally formed with a holding member thereof, and these tooth portions and the shaft-shaped portion are integrally formed by the same member. An electric power steering device characterized by the above.