JP2006218896A - Reduction gear for electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reduction gear for an electric power steering device capable of easily forming a sensor gear part even if a reduction gear part is formed of a resin such as MC nylon. <P>SOLUTION: This reduction gear 30 for the electric power steering device transmitting an auxiliary steering force of a power assist motor 13 to the steering shaft 11 of a vehicle comprises a core 31 fixable to the steering shaft 11, the reduction gear part 32 installed on the outer peripheral surface of the core 31 and engageable with a worm 18 on the power assist motor 13 side, and a resin sensor gear part 33 installed on the core 31 and engageable with the sensor pinion 22 of an angle sensor 15. The reduction gear part 32 and the sensor gear part 33 are formed separately from each other, and separately injection-molded. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a reduction gear for an electric power steering apparatus that transmits an auxiliary steering force by an electric motor to a steering shaft of a vehicle.

  The electric power steering device detects steering torque and other signals generated in the steering shaft by operating the steering wheel, drives the electric motor based on the detected signal, rotates the steering shaft via the speed reduction mechanism, and generates steering force. It is to assist.

  Conventional electric power steering devices are known in which an angle sensor for detecting the steering angle of the steering shaft is arranged around the worm gear speed reduction mechanism so that the control circuit for controlling the electric motor obtains optimum steering characteristics. (For example, refer to Patent Document 1).

  For example, as shown in FIG. 4, the worm gear reduction mechanism 100 includes a worm 101 that rotates together with the drive shaft of the electric motor, and a worm wheel 110 that is externally fitted to the steering output portion 102 a of the steering shaft 102 and meshes with the worm 101. The steering output of the electric motor controlled based on the steering torque detected by the torque sensor 102b is applied to the steering output unit 102a.

  As shown in FIGS. 4 and 5, the worm wheel 110 is appropriately splined on the outer peripheral surface of a metal core 111 fitted on the steering output portion 102a, and the processed surface is integrated with a synthetic resin. A formed cylindrical reduction gear portion 112 is provided. Wheel teeth 113 that mesh with the worm 101 are formed on the outer peripheral surface of the reduction gear portion 112, and a sensor gear that meshes with the sensor pinion 104 of the angle sensor 103 on the inner peripheral surface of the axial end portion of the reduction gear portion 112. The part 114 is integrally formed.

In addition, as shown in FIG. 6, the worm wheel 120 described in Patent Document 1 appropriately performs cross knurling or the like on the outer peripheral surface of a metal core 121, and the wheel teeth 122 mesh with the worm 101 on the processed surface. Is formed integrally with a synthetic resin such as MC nylon (monomer cast nylon), and a sensor gear portion 124 that meshes with the sensor pinion 104 of the angle sensor 103 is formed on the inner peripheral surface of the end portion of the core metal 121. Formed.
JP 2004-161150 A

  Incidentally, in the worm wheel 110 shown in FIG. 5, a synthetic resin capable of integrally molding the reduction gear portion 112 and the sensor gear portion 114 is used. However, as a resin material for the reduction gear portion 112, mechanical strength, heat resistance In the case of using MC nylon having excellent properties and wear resistance, it is difficult to form the sensor gear portion 114 integrally with the reduction gear portion 112. Therefore, as in the worm wheel 120 shown in FIG. The side surface of the gold 121 needs to be cut or plastically formed to form the sensor gear portion 124, which causes a problem that the manufacturing cost increases.

  The present invention has been made in order to eliminate such inconveniences, and an object of the present invention is to provide an electric power steering capable of easily forming a sensor gear portion even if it is a resin reduction gear portion such as MC nylon. The object is to provide a reduction gear for a device.

The above object of the present invention can be achieved by the following constitution.
(1) A reduction gear for an electric power steering device that transmits an auxiliary steering force by an electric motor to a steering shaft of a vehicle,
A core bar fixable to the steering shaft;
A reduction gear portion made of resin that is provided on the outer peripheral surface of the metal core and can mesh with the drive gear on the electric motor side;
A sensor gear portion made of resin that is attached to the metal core and can mesh with a sensor pinion of an angle sensor;
Have
The reduction gear for an electric power steering apparatus, wherein the reduction gear portion and the sensor gear portion are separate bodies and are separately injection-molded.

  According to the present invention, the sensor gear portion that meshes with the sensor pinion of the angle sensor and the reduction gear portion that meshes with the drive gear on the electric motor side are separate and are separately injection-molded. Even if it is a reduction gear part, a sensor gear part can be formed easily and reduction of manufacturing cost can be aimed at.

  Hereinafter, a reduction gear for an electric power steering apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a column-type electric power steering apparatus 10. Reference numeral 11 denotes a steering shaft, 12 denotes a housing of the steering shaft 11, 13 denotes a power assist motor (electric motor), and 14 denotes a worm gear reduction mechanism. (See FIG. 2), 15 is an angle sensor.

  The steering shaft 11 includes a steering input portion 11a and a steering output portion 11b, and is supported inside the housing 12 so as to be rotatable about an axis. The housing 12 is fixed to a predetermined position in the vehicle interior with the lower portion inclined forward, and a steering wheel (not shown) is fixed to the upper end of the steering input portion 11a.

  The steering input part 11a and the steering output part 11b are connected via a torsion bar 16 of a torque sensor 11c (see FIG. 2), and the steering transmitted from the steering wheel to the steering output part 11b via the steering input part 11a. Torque is detected by the torque sensor 11c, and the output of the power assist motor 13 is controlled based on the detected steering torque. A rack and pinion type motion conversion mechanism (not shown) is connected to the front end of the steering output portion 11b via a universal joint 17 and the like, and front wheels are attached to wheels provided at both ends of the rack of the rack and pinion type motion conversion mechanism. Tires are attached.

  The worm gear reduction mechanism 14 is disposed at an intermediate position in the axial direction of the steering shaft 11, and as shown in FIG. 2, a worm wheel 30 as a reduction gear, and a worm 18 as a drive gear meshing with the worm wheel 30, A gear case 19 that houses the worm wheel 30 and the worm 18 is provided, and a steering assist force is applied from the power assist motor 13 to the steering output portion 11b via the worm gear reduction mechanism 14.

  The rotating shaft of the worm 18 is spline-coupled to the driving shaft of the assist power motor 13 and is rotatably supported by a gear case 19 via a bearing. In this gear case 19, a steering output portion 11b supports the bearings 20 and 21. It is rotatably supported via.

  As shown in FIGS. 2 and 3, the worm wheel 30 is a resin-made deceleration gear that meshes with the worm 19 on the side of the power assist motor 13 on the outer peripheral surface of a metal core 31 fitted and fixed to the steering output portion 11 b. It has a gear part 32 and a sensor gear part 33 that meshes with the sensor pinion 22 of the angle sensor 15.

  As shown in FIG. 3, the core metal 31 includes an annular plate portion 35 having a fitting hole 34 fitted to the steering output portion 11 b, and a cylindrical portion 36 provided on the outer peripheral portion of the annular plate portion 35. And.

  The reduction gear teeth 32 are made of MC nylon, and are appropriately formed on the processed surface by subjecting the outer peripheral surface of the cylindrical portion 36 of the core bar 31 to appropriate cross knurling. The sensor gear 33 is separated from the reduction gear teeth 32 and is integrally formed on the core 31 by injection molding of a resin material such as polyacetal (POM) or polybutylene terephthalate (PBT).

  After such molding, the sensor gear portion 33 is cylindrical, and the base end portion is fitted into the inner peripheral portion of the cylindrical portion 36 of the core metal 31, and the distal end portion projects from the end surface of the cylindrical portion 36. Teeth 37 that mesh with the worm 18 are formed on the outer peripheral surface. Further, a plurality of retaining holes 38 are formed in the circumferential direction in the annular plate portion 35 of the core metal 31, and the retaining member 38 is filled with a resin material, so that the sensor gear portion 33 is prevented from being detached. .

  Therefore, in the present embodiment, the sensor gear portion 33 that meshes with the sensor pinion 22 of the angle sensor 15 and the reduction gear portion 32 that meshes with the worm 18 on the power assist motor 13 side are separate and are separately injection-molded. In order to form the sensor gear portion 33, it is not necessary to perform post-processing such as cutting or plastic working on the core 31. As a result, the sensor gear portion 33 can be easily formed and the manufacturing cost can be reduced. Can do.

In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it can change suitably.
For example, in the above embodiment, the case where the teeth 37 that mesh with the sensor pinion 22 are formed on the outer peripheral surface of the sensor gear portion 33 is illustrated, but the sensor pinion 22 is formed on the inner peripheral surface and the side surface of the sensor gear portion 33 and other places. Teeth 37 that mesh with each other may be formed.

It is sectional drawing which shows the electric power steering apparatus which is one Embodiment of this invention. It is sectional drawing for demonstrating the worm gear reduction mechanism of the electric power steering apparatus which is one Embodiment of this invention. It is sectional drawing for demonstrating the worm wheel for electric power steering apparatuses which is one Embodiment of this invention. It is sectional drawing for demonstrating the worm gear reduction mechanism which employ | adopted the conventional worm wheel. It is sectional drawing for demonstrating an example of the conventional worm wheel. It is sectional drawing for demonstrating the other example of the conventional worm wheel.

Explanation of symbols

11 Steering shaft 13 Power assist motor (electric motor)
15 Angle sensor 18 Worm (drive gear)
22 Sensor pinion 30 Worm wheel (reduction gear)
31 Core 32 Reduction gear part 33 Sensor gear part

Claims (1)

A reduction gear for an electric power steering device that transmits auxiliary steering force by an electric motor to a steering shaft of a vehicle,
A core bar fixable to the steering shaft;
A reduction gear portion made of resin that is provided on the outer peripheral surface of the metal core and can mesh with the drive gear on the electric motor side;
A sensor gear portion made of resin that is attached to the metal core and can mesh with a sensor pinion of an angle sensor;
Have
The reduction gear for an electric power steering apparatus, wherein the reduction gear portion and the sensor gear portion are separate bodies and are separately injection-molded.

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