JP2006051913A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device reducing noise generated at a fitting part of a motor output shaft for transmitting assist torque of the electric power steering device and a deceleration mechanism input shaft or preventing the motor from being damaged by transmitting excessive input from a wheel to the motor. <P>SOLUTION: The output shaft of the motor and the input shaft of the deceleration mechanism part are made in the non-contact state by transmitting output torque of the motor by utilizing magnetic force. Further, effect of a torque limiter is exhibited by adjusting magnetic force. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric power steering device, and more particularly to an electric power steering device that reduces noise generated at a connecting portion between a motor and a speed reduction mechanism.

  An electric power steering device for energizing a steering device of an automobile with an assisting force (assist torque) by a rotational force of a motor uses a transmission mechanism such as a gear or a belt to drive the driving force of the motor via a speed reduction mechanism. An assist torque is applied to the shaft. An example of a simple configuration of such an electric power steering apparatus will be described with reference to FIG. A steering shaft 102 (steering shaft 102a, steering shaft 102b) of the steering handle 101 is coupled to a tie rod 106 of a steering wheel via a speed reduction mechanism 103, universal joints 104a and 104b, and a pinion rack mechanism 105. The steering shaft 102 a is provided with a torque sensor 107 that detects the steering torque of the steering handle 101. A motor 108 that assists the steering force of the steering handle 101 is applied to the steering shaft 102 b via the speed reduction mechanism 103. It is connected.

  In such an electric power steering apparatus, the engagement between the output shaft of the motor 108 that generates assist torque and the input shaft of the speed reduction mechanism 103 is mainly a contact type by spline fitting, and is reversed from the steering wheel. Each time the steering shaft rotates slightly with respect to the input, it may reach the output shaft of the motor via the speed reduction mechanism and generate abnormal noise (noise). In order to reduce the magnitude of such noise, Patent Document 1 takes an improvement measure to reduce noise by installing an elastic body between the output shaft of the motor 108 and the input shaft of the speed reduction mechanism unit 103. It was.

  Further, a large impact torque may be applied to the torque transmission path of the electric power steering apparatus from the outside depending on the road surface state during the steering operation of the vehicle. In order to cut off the impact torque, Patent Document 2 discloses an electric power steering. A torque limiter is attached to the motor of the device to cut off.

JP-A-11-198829 JP-A-9-84300

  However, with the electric power steering device that implements the above-mentioned noise reduction measures using an elastic body, the noise cannot be reduced as much as expected. And the impact torque is amplified due to the inertia of the torque limiter itself.

  The present invention has been made for the above-mentioned circumstances, and an object of the present invention is to sufficiently reduce the noise generated at the output shaft of the motor and the input shaft of the speed reduction mechanism, and also relates to an external impact torque. Another object of the present invention is to provide an electric power steering device in which vibration from a vehicle is not transmitted to a motor via a rigid body, and conversely, vibration from the motor is not transmitted to a mechanism portion via a rigid body.

The present invention relates to an electric power steering apparatus including a motor that applies a steering assist force to a steering mechanism, and a speed reduction mechanism that transmits torque generated on an output shaft of the motor to the steering mechanism. The above-mentioned object is that the output shaft of the motor and the input shaft of the speed reduction mechanism section are fitted in a non-contact manner, and torque transmission means for transmitting torque generated on the output shaft of the motor to the input shaft of the speed reduction mechanism section Achieved by having
Moreover, the said objective is effectively achieved when the said torque transmission means transmits the said torque via magnetic force.
Further, the above object is more effectively achieved by setting the strength of the magnetic force to a predetermined amount in order to impose a limit on the amount of torque transmitted.

According to the electric power steering apparatus of the present invention, since the output shaft of the motor and the input shaft of the speed reduction mechanism section are not in contact with each other, an electric power steering apparatus that does not generate noise can be provided.
In addition, since there is a limit on the amount of magnetic force used for transmission, the electric power that prevents the impact torque from being transmitted from the steered wheels to the motor, or the vibration from the motor is not transmitted to the mechanism, and prevents the motor from being destroyed. A steering device can be provided.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a motor 108 and a speed reduction mechanism unit 103 to which the present invention is applied. A worm wheel 10 is coaxially fixed to the motor steering shaft 102b connected to the steering handle 101 so as to be integral with the steering shaft 102b in the rotational direction, and the worm 11 meshing with the worm wheel 10 is contained in the housing 12. The bearings 12a and 12b are rotatably supported. That is, the speed reduction mechanism input shaft 2 of the speed reduction mechanism portion 103 penetrates so that the worm 11 is integrated in the rotation direction and the axial direction, and one end portion of the speed reduction mechanism input shaft 2 is inside the housing 12 via the bearing 12a. A position slightly inside the other end of the speed reduction mechanism input shaft 2 is rotatably supported in the housing 12 via a bearing 12b. The motor output shaft 1 of the motor 108 and the speed reduction mechanism input shaft 2 of the speed reduction mechanism 103 are fitted in a non-contact manner as shown in FIG. This non-contact is an important point of the present invention.

  Next, means for transmitting the output torque of the motor 108 to the speed reduction mechanism 103 in a non-contact manner will be described. In this embodiment, magnetic force is used as the torque transmission means, and specifically, the magnetic force of a permanent magnet is used. FIG. 2A is an enlarged view of the fitting portion A between the motor output shaft 1 and the speed reduction mechanism input shaft 2. FIG. 2B is a cross-sectional view taken along arrow XX in FIG. In FIG. 2, a permanent magnet 3-1 (S pole) and 3-2 (N pole) are embedded in the motor output shaft 1 of the motor so that the central axis of the motor output shaft 1 is symmetrical. On the other hand, the distal end portion 2a of the speed reduction mechanism input shaft 2 of the speed reduction mechanism portion 103 has permanent magnets 3-3 (N pole) and 3-4 (S pole) at positions facing the permanent magnets 3-1 and 3-2, respectively. ) Is embedded. The permanent magnets 3-3 (N pole) and 3-4 (S pole) may be attached to the outer periphery. As shown in FIGS. 2 (A) and 2 (B), the permanent magnets 3-1, 3-2, 3-3, 3-4 are cut out of a cylindrical portion as an example of the embodiment. It has a different shape.

  How the rotational torque of the motor output shaft 1 configured as described above is transmitted to the speed reduction mechanism input shaft 2 will be described below. When the motor output shaft 1 rotates, the permanent magnets 3-1 (S pole) and 3-2 (N pole) embedded in the motor output shaft 1 rotate accordingly. When the permanent magnets 3-1 and 3-2 are rotated, the permanent magnets 3-3 (N pole) and 3-4 (S pole) at positions facing them are the same as the permanent magnets 3-1 and 3-2. Rotates by adsorption force. When a rotational force is applied to the permanent magnets 3-3 and 3-4, the speed reduction mechanism input shaft 2 in which the permanent magnets 3-3 and 3-4 are embedded also rotates together. In this way, the rotational torque of the motor output shaft 1 is transmitted to the rotation of the speed reduction mechanism input shaft 2. However, there is a limit to the torque that can be transmitted for the following reason.

  The strength of torque that can be transmitted from the motor output shaft 1 to the speed reduction mechanism input shaft 2 is the strength of the magnetic force of the permanent magnets 3-1, 3-2, 3-3, 3-4, or the permanent magnet 3-1. 3-3, and the distance D between the permanent magnets 3-2 and 3-4. The stronger the magnetic force of the permanent magnet and the shorter the distance D between the magnets, the stronger the torque that can be transmitted. Therefore, in consideration of the maximum value (predetermined amount) of torque to be transmitted, the strength of the magnetic force of the permanent magnets 3-1, 3-2, 3-3, 3-4, or the distance D should be determined. .

  As described above, since the motor output shaft 1 and the speed reduction mechanism input shaft 2 are not in contact with each other, no noise is generated and a function as a torque limiter is provided. The effect which prevents damage etc. is acquired.

  FIG. 3 shows an embodiment in which the configuration of torque transmission means between the motor output shaft 1 and the speed reduction mechanism input shaft 2 is different. In this embodiment, the front end 1b and the front end 2b of the motor output shaft 1 and the speed reduction mechanism input shaft 2 have a cylindrical shape, and permanent magnets 3-5 (S pole) and 3-6 are provided on the front end 1b. (N pole) is embedded, and permanent magnets 3-7 (N pole) and 3-8 (S pole) are embedded in the tip 2b so as to face each other.

  Also in this configuration, when the motor output shaft 1 is rotated by the attractive force between the permanent magnet 3-5 and the permanent magnet 3-7 and the attractive force between the permanent magnet 3-6 and the permanent magnet 3-8, the speed reduction mechanism is input. The shaft 2 rotates and torque is transmitted.

  Also in this embodiment, the strength of torque that can be transmitted from the motor output shaft 1 to the speed reduction mechanism input shaft 2 is the strength of the magnetic force of the permanent magnets 3-9, 3-6, 3-7, 3-8, Alternatively, it is determined by the distance D between the permanent magnets 3-5 and 3-7 and the permanent magnets 3-6 and 3-8. The stronger the magnetic force of the permanent magnet and the shorter the distance D between the magnets, the stronger the torque that can be transmitted. Therefore, in consideration of the maximum value (predetermined amount) of torque to be transmitted, the strength of the magnetic force of the permanent magnets 3-5, 3-6, 3-7, 3-8, or the distance D should be determined. .

  As described above, since the motor output shaft 1 and the speed reduction mechanism input shaft 2 are not in contact with each other, no noise is generated and a function as a torque limiter is provided. The effect which prevents damage etc. is acquired.

  FIG. 4 shows an embodiment in which the configuration of torque transmission means between the motor output shaft 1 and the speed reduction mechanism input shaft 2 is further different. In this embodiment, the tip portion 1c of the motor output shaft 1 has a plate-like shape, while the tip portion 2c of the speed reduction mechanism input shaft 2 is a cylinder so as to be fitted to the tip portion 1c. It has a flat shape. Plate-like permanent magnets 3-9 (S pole) and 3-10 (N pole) are embedded in the tip portion 1c, and the plate-like permanent magnet 3-11 (N pole) is placed in the tip portion 2c so as to face each other. And 3-12 (S pole) are embedded.

  Also in this configuration, when the motor output shaft 1 rotates due to the attracting force between the permanent magnet 3-9 and the permanent magnet 3-11 and the attracting force between the permanent magnet 3-10 and the permanent magnet 3-12, the speed reduction mechanism is input. The shaft 2 rotates and torque is transmitted.

  In this embodiment, the motor output shaft and the speed reduction mechanism input shaft can be brought into non-contact with each other while having a mechanical restraining means in the rotational direction.

FIG. 5 shows a structure in which a triangular pyramid protrusion is provided on the shaft surface of the motor output shaft 1 of the motor of the embodiment of FIG. On the other hand, a triangular pyramid projection is provided on the inner side of the input shaft, the shape of the deceleration mechanism input shaft 2 of the speed reduction mechanism section being different from the above projection. A permanent magnet 3-13 (S pole) and 3-14 (N pole) are embedded in the motor output shaft 1 of the motor so that the central axis of the motor output shaft 1 is symmetrical. On the other hand, permanent magnets 3-15 (N pole) and 3-16 (S pole) are arranged at positions facing the permanent magnets 3-13 and 3-14, respectively, at the tip of the speed reduction mechanism input shaft 2 of the speed reduction mechanism section. Embedded. Also in this case, as the motor output shaft 1 rotates, the rotational torque is transmitted to the speed reduction mechanism input shaft 2 by the attractive force of each permanent magnet.

  In this embodiment, the motor output shaft and the speed reduction mechanism input shaft can be brought into non-contact with each other while having a mechanical restraining means in the rotational direction.

  In the torque transmission method using magnetic force, the torque is not transmitted when an excessive torque greater than the torque that can be transmitted is applied due to the strength of the permanent magnets (the strength of the magnetic force) and the distance between the permanent magnets. Idle. Therefore, by adjusting the strength of the permanent magnets (the strength of the magnetic force) and the distance between the permanent magnets, if an excessive torque exceeding the set torque value (predetermined amount) is applied, If the sheath distance is adjusted, a torque limiter function can be provided.

  As described above, since the output torque of the motor can be transmitted to the speed reduction mechanism without contact, there is an effect that noise is not generated. Moreover, since it is non-contact, the effect which does not generate | occur | produce abrasion of components can also be expected. In addition, the function of the torque limiter can be provided to prevent the motor shaft from being damaged due to reverse input.

  In the above description, a permanent magnet is used as the magnetic force generating means. However, the same effect can be obtained even if an electromagnet is used. Further, when the output shaft of the motor and the input shaft of the speed reduction mechanism section are not in contact with each other, the same effect can be obtained even if a gas other than air exists between them. In addition, the same effect can be obtained even if a liquid, for example, cooling oil or the like exists between the two. Moreover, there is no restriction | limiting in the shape of a magnet, For example, you may arrange a square-shaped magnet in circular arc shape. Further, the shapes of the motor output shaft and the speed reduction mechanism input shaft are not limited, and the same effect can be obtained with a triangle, square, or other polygon. Further, the same effect can be obtained even if the shapes (relationship between male and female) of the motor output shaft and the speed reduction mechanism input shaft of the embodiment are interchanged.

  As described above, if the present invention is used, the output torque of the motor can be transmitted to the speed reduction mechanism section in a non-contact manner, and there is an effect that no noise is generated or parts are not worn. Furthermore, there is an effect that excessive input from the wheel is not transmitted to the motor via the rigid body, or vibration from the motor is not transmitted to the mechanism portion via the rigid body.

It is a block diagram which shows the relationship between a motor and a deceleration mechanism part. It is a figure which shows the relationship between the motor output shaft and deceleration mechanism input shaft in Example 1. FIG. It is a figure which shows the relationship between the motor output shaft and deceleration mechanism input shaft in Example 2. FIG. It is a figure which shows the relationship between the motor output shaft in Example 3, and the deceleration mechanism input shaft. It is a figure which shows the relationship between the motor output shaft and deceleration mechanism input shaft in Example 4. FIG. It is a block diagram of an electric power steering device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor output shaft 2 Deceleration mechanism input shaft 2a Tip part 1b, 2b Tip part 1c, 2c Tip part 3-1, 3-3, 3-5, 3-7, 3-9, 3-11, 3-14, 3-15 N pole magnet 3-2, 3-4, 3-6, 3-8, 3-10, 3-12, 3-13, 3-16 S pole magnet

Claims (3)

An electric power steering apparatus comprising: a motor that applies a steering assist force to a steering mechanism; and a speed reduction mechanism that transmits torque generated on an output shaft of the motor to the steering mechanism.
A torque transmitting means for fitting the output shaft of the motor and the input shaft of the speed reduction mechanism portion in a non-contact manner and transmitting torque generated on the output shaft of the motor to the input shaft of the speed reduction mechanism portion; An electric power steering device. The electric power steering apparatus according to claim 1, wherein the torque transmission means transmits the torque via magnetic force. The electric power steering apparatus according to claim 2, wherein the intensity of the magnetic force is set to a predetermined amount in order to impose a limit on the amount of torque transmitted.

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