JPH10194149A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a rack shaft from an excessive external force, owing to the hitting of the rack shaft to a stopper resulting from a large bending amount of the rack shaft, when an excessive external force is operated to the rack shaft. SOLUTION: In this electric power steering device, a rack tooth 5a is formed on the front surface of one end of a rack shaft 5 extended in the car width direction, a pinion 4 is engaged to the rack tooth 5a, a rack guide 50 pushing out the rear surface of the rack shaft is installed, a screw part is formed at the other end of the rack shaft, a nut is installed to the screw part, and an auxiliary torque according to a steering torque is to be added to the rack shaft through the nut. The rack guide is provided at the center side of the car body by the pinion, the rack shaft, the pinion, the rack guide, and the nut are housed in a steering gear box 21 in a bulk, and a stopper 22a to limit the bending of the one end of the rack shaft is provided in the steering gear box 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement in an electric power steering device mounted on a vehicle.

[0002]

2. Description of the Related Art In recent years, electric power steering devices have been frequently used in order to reduce the steering force of a steering wheel to provide a comfortable steering feeling. This type of electric power steering apparatus generates an auxiliary torque according to a steering torque by an electric motor and transmits the auxiliary torque to a steering system. For example, Japanese Patent Application Laid-Open No. Hei 7-165089 discloses a "steering apparatus". is there. According to FIGS. 1 and 3 of the publication, the ball nut mechanism 33 is used.
(The numbers are quoted from those described in the official gazette. The same applies hereinafter.) Is attached to one end of the rack shaft 2 and the rack shaft 2
A rack 8 is provided at the other end of the
Is engaged. Then, the rack shaft 2 is placed at the position where the pinion 6 and the rack 8 are engaged with each other.
A rack guide 10 is provided for pressing the engaging portion to eliminate play at the engaging portion.

FIGS. 10 (a) to 10 (c) are schematic illustrations of a conventional electric power steering apparatus. FIG. 1 and FIG. 3 shown in the above prior art are shown again to explain the prior art. FIG. Note that the reference numerals are different from those in the related art. 1A is a schematic plan view of a steering device. A steering device 100 has tie rods 102 and 102 and a knuckle arm 10 at both ends of a rack shaft 101. FIG.
The wheels 104, 104 are connected via the wheels 3, 103, and a ball nut mechanism 105 is connected to one end of the rack shaft 101.
And a rack 106 is provided at the other end of the rack shaft 101, and a pinion 107 is engaged with the rack 106,
The rack shaft 101 is pressed by a rack guide 108 from the opposite side of the pinion 107.

FIG. 1B shows a rack shaft 101 shown in FIG.
According to this schematic diagram, the rack shaft 101 is supported at two positions, that is, the position of the ball nut mechanism 105, the position of the pinion 107 and the position of the rack guide 108, and the support span is long. .

(C) shows the rack shaft 101 shown in (b) above.
FIG. 4 is a schematic operation diagram of the surroundings. According to this operation diagram, the road surface reaction force during traveling, particularly during steering, is reduced by the tie rods 102, 102.
Through the rack shaft 101. Therefore, external forces or moments (hereinafter, referred to as “moments M, M”) caused by the road surface reaction force act on both ends of the rack shaft 101. As a result, the rack shaft 101 bends in the vehicle longitudinal direction (vertical direction in the drawing) as shown by the solid line and the dotted line in this figure.

[0006]

The above-mentioned FIG.
In the steering apparatus shown in (1), the following points can be cited as general causes of vibration of the rack shaft 101. (1) The road surface reaction force during traveling, particularly during steering, is
The vibration is transmitted to the rack shaft 101 through the second shaft 102 and the second shaft 102, and causes vibration of the rack shaft 101 in the longitudinal direction of the vehicle body (first trigger). (2) At the moment when each ball of the ball nut mechanism 105 comes into contact with and separates from the threaded portion of the rack shaft 101, the force acting on the threaded portion from the ball fluctuates. This is a trigger for generating vibration in the rack shaft 101 (second trigger).

The rack shaft 101 shown in FIG. 10 amplifies the vibration when the frequency of the first trigger and the frequency of the second trigger match. Moreover, when the frequency (frequency) of the amplified vibration matches the natural frequency of the rack shaft 101, the rack shaft 101 vibrates greatly due to resonance. When the rack shaft 101 vibrates greatly, the vibration is transmitted to the vehicle interior via the steering handle, and causes noise in the vehicle interior. Further, if vibration is transmitted to the steering handle, it is not preferable in terms of steering feeling. To suppress the resonance of the rack shaft 101, it is conceivable to change the natural frequency by changing the diameter of the rack shaft 101, or to provide a vibration damping member or the like on the rack shaft 101, but the rack shaft 101 becomes heavy. , The structure becomes complicated.

On the other hand, the moment M can become excessive. Even if the moment M is excessive, the rack shaft 101 needs to withstand sufficiently. For this reason, the diameter of the rack shaft 101 may be changed, but it becomes heavy.

Accordingly, an object of the present invention is to provide (1) a technique capable of easily suppressing vibration of a rack shaft during traveling, particularly during steering, with a simple structure, and (2) changing the strength of the rack shaft itself. It is an object of the present invention to provide a technique capable of protecting a rack shaft from an excessive moment with a simple structure without any problem.

[0010]

In order to achieve the above object, according to the present invention, a rack tooth is formed on a front surface of one end of a rack shaft extending in a vehicle width direction, and a pinion is formed on the rack tooth. And a rack guide for pushing the rear surface of the rack shaft is attached, a screw portion is formed at the other end of the rack shaft, a nut is attached to this screw portion, and an auxiliary torque according to the steering torque is applied via the nut. In an electric power steering device that is added to a rack shaft, the rack guide is disposed closer to the center of the vehicle than the pinion, and the rack shaft, pinion, rack guide, and nut are collectively stored in a steering gear box. The box is provided with a stopper for limiting the amount of deflection of one end of the rack shaft.

An external force or moment (hereinafter, referred to as "moment") due to the road surface reaction acts on both ends of the rack shaft. When the other end of the rack shaft is bent away from the pinion by the moment and the screw mechanism (combination of the screw portion and the nut), the rack shaft is supported only by the screw mechanism and the rack guide. On the other hand, when the other end of the rack shaft is bent in a direction in which the rack shaft is pressed against the pinion, the rack shaft has a structure in which bending can be suppressed by a screw mechanism, a rack guide, and a pinion. Therefore, the mode (mode) of bending or bending differs depending on the bending direction of the rack shaft. That is, when the rack shaft is deformed in the front-rear direction of the vehicle body by the road surface reaction force and the screw mechanism, the swing waveform when deforming forward and the swing waveform when deforming rearward have asymmetric shapes. Since the swing waveform is asymmetric,
The natural frequency of the rack shaft differs depending on the bending direction, and there is no fear of vibration amplification due to resonance. As a result, vibration of the rack shaft can be easily suppressed. When the vibration of the rack shaft is suppressed, the vibration of the steering handle is also suppressed, so that the steering feeling is enhanced. Further, since vibration transmitted to the vehicle interior via the steering handle is suppressed, noise in the vehicle interior can be prevented.

When an external force or moment (hereinafter, referred to as "normal external force") caused by a road surface reaction force during normal running, particularly during normal steering, acts on the rack shaft, the rack shaft has a small amount of deflection. Therefore, it does not hit the stopper. The rack shaft operates smoothly because it does not hit the stopper. as a result,
A good steering feeling can be maintained during normal running, particularly during normal steering. On the other hand, when an external force or a moment (hereinafter, referred to as “excessive external force”) caused by an excessive road surface reaction force acts on the rack shaft, the rack shaft hits the stopper because the amount of deflection is large. For this reason, the rack shaft can be protected from excessive external force. Therefore, the reliability of the electric power steering device is further improved. Further, since the stopper portion is simply provided in the steering gear box, there is no need to increase the number of parts. For this reason, the productivity of the electric power steering device increases.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings should be viewed in the direction of reference numerals. FIG. 1 is a system diagram of an electric power steering device according to the present invention. The electric power steering device 1 includes a rack and pinion mechanism 3 (including a pinion 4 and a rack shaft 5) connected to a steering handle 2, and steering. A steering torque detecting means 6 for detecting a steering torque of the steering system generated by the steering wheel 2, a control means 7 for generating a control signal based on a detection signal of the steering torque detecting means 6, and a control signal of the control means 7 An electric motor 8 that generates an auxiliary torque corresponding to the steering torque based on the steering torque, and a ball screw (ball nut mechanism) 9 that transmits the auxiliary torque of the electric motor 8 to the rack shaft 5. And wheels (steering wheels) 13 via knuckle arms 12
13 is a device that steers 13.

FIG. 2 is an overall configuration diagram of the electric power steering apparatus according to the present invention, which is a view as viewed from the rear of the vehicle body, and is a cross-sectional view of a main part. The electric power steering device 1 includes a rack and pinion mechanism 3, an electric motor 8,
The ball screw 9 is collectively housed in a steering gear box 21 extending in the vehicle width direction (the left-right direction in this figure), and the steering gear box 21 is a substantially tubular first housing 22 bolted to each other in the longitudinal direction.
And the second housing 23. First housing 2
Reference numeral 2 denotes a bracket 24 for mounting to a vehicle body (not shown), and the second housing 23 includes a mounting member 25 for mounting to the vehicle body.

The rack shaft 5 extending in the vehicle width direction has a pinion 4 engaged at one end, a ball screw 9 is assembled at the other end, and tie rods 11, 11 are connected at both ends. It penetrates the steering gear box 21 so as to slide in the direction. The steering gear box 21 has a rack guide 50 mounted between the pinion 4 and the ball screw 9. That is, the rack guide 50 is arranged closer to the vehicle body than the pinion 4.
The rack and pinion mechanism 3 will be described in detail with reference to FIG. In the figure, 26, 26 are ball joints, 27, 2
7 is a rubber cover.

In the vehicle width direction, the axial center position of the ball screw 9 in the axial direction is A (hereinafter referred to as "ball screw center A"), and the center position of the engagement between the pinion 4 and the rack shaft 5 is B (hereinafter referred to as B). When the center position of the rack guide 50 is C (hereinafter, referred to as “rack guide center C”), the distance L ₁ from the ball screw center A to the rack guide center C is referred to as “L”. , the ratio between the distance L ₂ from the rack guide center C to the pinion center B, generally 3: 1 to 5: is preferably set to 1.

FIG. 3 is a sectional view taken along the line 3-3 in FIG. 2. The electric power steering apparatus 1 includes a tubular input shaft 31 connected to the steering handle 2 (see FIG. 1), and an inner portion of the input shaft 31. Insert the upper part of the pin 32 into the input shaft 31
A main steering system is constituted by a torsion bar (elastic member) 33 connected by the above and an output shaft 34 which is serrated and connected to a lower portion of the torsion bar 33 and has the pinion 4 provided below.

The steering torque detecting means 6 is provided between the input and output shafts 3.
The steering torque of the steering system is detected by detecting the relative torsion angles 1 and 34, and comprises a torsion bar 33, a slider 35 and a sensor 36. More specifically, the torsion bar 33 is a member that literally generates a twist angle with respect to the torque, and the input shaft 3
1 and the output shaft 34 generate a relative torsional displacement.
A cylindrical slider 35 having an inclined groove 35a and a vertically long straight groove 35b is connected to the input shaft 31 and the output shaft 34.
And the slider 35 can be displaced in the axial direction according to the relative torsional displacement. The displacement at this time is proportional to the torque, and the displacement is converted into an electric signal by the variable inductance sensor 36.

The input shaft 31, the torsion bar 33 and the output shaft 34 are concentric. In the figure, reference numerals 41 and 42 denote a third housing and a fourth housing, which are mounted on an upper portion of the first housing 22. 43 is the input shaft 3
1 and bearings 44 and 45 for supporting both ends of the output shaft 34.

FIG. 4 is a sectional view taken along line 4-4 of FIG. The rack guide 50 is
Guide part 5 for pushing out the rear surface (left side in this figure) of rack shaft 4
1, an adjustment bolt 53 for pushing the guide portion 51 via a compression spring (elastic member) 52, and a lock nut 54 for locking the position of the adjustment bolt 53. The adjustment bolt 53 is screwed into the first housing 22. The rack guide 50 having such a configuration is provided in the first housing 2.
By pressing the guide portion 51 with an appropriate pressing force via the compression spring 52 with the adjusting bolt 53 screwed into the rack 2, a preload is applied to the rack shaft 5 by the guide portion 51, and the rack shaft 5 is pressed against the pinion 4. be able to. In the figure, reference numeral 55 denotes a contact member provided on the guide portion.

FIG. 5 is a sectional view taken along the line 5-5 in FIG. 2, and rack teeth 5a are provided on the front surface (the upper surface in this figure) of one end of the rack shaft 5.
Forming a meshing pinion 4 with the rack teeth 5a, the rack guide center C away from the pinion center B by a distance L _2, the rear surface of the rack shaft 4 at the rack guide 50 extruding the (lower surface in this figure) It shows that you did.
That is, the pinion 4 supports the rack shaft 5 from the front of the vehicle body, and the rack guide 50 presses the rack shaft 5 from the rear of the vehicle body.

By the way, the steering gear box 21
The first housing 22 has a stopper portion 2 for limiting the amount of deflection of the one end portion of the rack shaft 5 rearward (downward in the figure).
2a. For details, see the first
At one end of the housing 22, an inner edge portion is used as a stopper portion 22a.
a is in the position D of the distance L ₃ from the pinion center B. Therefore, if the gap S ₁ between the rear surface of the rack shaft 5 and the inner surface of the first housing 22 is set to a predetermined size δ (hereinafter, referred to as “gap size δ”), the stopper portion 22 a The amount of deflection of the rack shaft 5 at the position can be limited within the gap dimension δ.

FIG. 6 is a sectional view of a main part around a rack shaft, an electric motor and a ball screw according to the present invention. The electric motor 8 includes the stator 61 and the rotor 6 housed in the second housing 23.
The rotor 62 has a tubular output shaft 63 that is rotatably inserted through the rack shaft 5. The output shaft 63 has both ends rotatably supported in the first and second housings 22 and 23 via bearings 64 and 65, and has a nut 71 of the ball screw 9 in the other end.
Is attached. The bearing 65 supports the ball screw 9 via the output shaft 63 at or near the center A of the ball screw.

The ball screw 9 is provided with a nut 71 of the outer cylinder.
And a screw portion 5b formed on the rack shaft 5 operates via a ball (not shown), and the ball reaching the end of the screw groove of the nut 71 circulates through the tube, so-called internal portion. This is a general configuration of a circulation type or an external circulation type, and a detailed configuration is omitted for convenience. That is, the ball screw 9 is a screw mechanism including a combination of the screw portion 5b and the nut 71. In the figure, reference numeral 72 denotes a lock screw that is screwed into the inner surface of the output shaft 63, and prevents the nut 71 from moving in the axial direction with respect to the output shaft 63.

Next, the operation of the electric power steering apparatus having the above configuration will be described. FIGS. 7A to 7D are diagrams for explaining the operation of the electric power steering apparatus according to the present invention (first).
It is. FIG. 7A is a schematic plan view in which the electric power steering apparatus 1 of FIG. 2 is combined with the system of FIG. Note that the reference numerals of the respective parts are the same as those shown in FIGS. 1 and 2, and a description thereof will be omitted.

FIG. 7B is a further schematic diagram around the rack shaft 5 shown in FIG. 7A. The rack shaft 5 is supported by a ball screw center A and a pinion center B, and a rack guide center C is shown. Indicates that it was pressed. More specifically, since the ball screw 9 is assembled to the rack shaft 5, the ball screw 9 supports the rack shaft 5 from the front of the vehicle body and the rear of the vehicle body (vertical direction in the drawing). The pinion 4 supports the rack shaft 5 from the front of the vehicle body, and the rack guide 50 presses the rack shaft 5 from the rear of the vehicle body.

FIG. 7C is a schematic operation diagram (first) around the rack shaft 5 shown in FIG. 7B, and FIG.
It is a schematic operation figure (2nd) around the rack axis | shaft 5 shown to (b). At both ends of the rack shaft 5, an external force or moment (hereinafter, “moment Mf from the front of the vehicle body”, “moment Mr from the rear of the vehicle body”) due to the road surface reaction force and the ball screw 9 during traveling, particularly during steering, is described. ) Works. FIG.
(C), the moment Mf from the front of the vehicle body,
When the end of the rack shaft 5 is bent away from the pinion 4 by Mf, the rack shaft 5 is supported only by the ball screw 9 and the rack guide 50. As a result, the rack shaft 5 bends as indicated by the thick solid line in FIG.

On the other hand, as shown in FIG. 7D, when the end of the rack shaft 5 is bent in the direction of pressing against the pinion 4 by the moments Mr and Mr from the rear of the vehicle body, the rack shaft 5 The three members, the rack guide 50 and the pinion 4, have a structure in which bending can be suppressed. As a result, the rack shaft 5 bends with the ball screw center A, the pinion center B, and the rack guide center C as fulcrums, as indicated by the thick solid line in the figure.

Therefore, the mode (mode) of bending or bending differs depending on the bending direction of the rack shaft 5. That is, when the rack shaft 5 is deformed in the front-rear direction of the vehicle body due to the road surface reaction force and the ball screw 9, FIGS.
As described above, the oscillating waveform when deforming forward and the oscillating waveform when deforming backward have asymmetric shapes. Since the rocking waveform is asymmetric, the natural frequency of the rack shaft 5 differs depending on the bending direction, and there is no fear of vibration amplification due to resonance. As a result, vibration of the rack shaft 5 can be easily suppressed. When the vibration of the rack shaft 5 is suppressed, the vibration of the steering handle is also suppressed, so that the steering feeling is enhanced. Further, since vibration transmitted to the vehicle interior via the steering handle is suppressed, noise in the vehicle interior can be prevented.

Further, the distance L ₁ from the ball screw center A to the rack guide center C, the ratio of the distance L ₂ from the rack guide center C to the pinion center B, approximately 3: 1
By setting 5: 1, the natural frequency of the rack shaft 5 and
The natural frequency of the mounting portion of the steering gear box 21 does not match. By shifting the resonance point of the rack shaft 5 from the resonance point of the portion where the steering gear box 21 for housing the steering system and the rack-and-pinion mechanism 3 is mounted, the vibration of the rack shaft 5 is not transmitted to the vehicle body. . Therefore, the noise in the cabin is further reduced, good commercial value is obtained, and the steering feeling is further enhanced.

FIGS. 8A and 8B are explanatory diagrams (second) of the operation of the electric power steering apparatus according to the present invention, and FIG. 8A shows the operation of the present embodiment. b) shows the effect of the comparative example. First, in the comparative example of FIG. 8B, the amount of deflection of one end of the rack shaft 5 toward the rear of the vehicle body is not limited. External force caused from the front end of the rack shaft 5 in the road surface reaction force (hereinafter, referred to as "external force P".) May acts, longer distance L ₅ from the rack guide center C to the point of action of the external force P. For this reason, the amount of deflection of the rack shaft 5 is large, and at this time, the maximum bending moment Mb acting on the rack shaft 5 is also large.

On the other hand, in this embodiment shown in FIG. 8A, the amount of deflection of one end of the rack shaft 5 toward the rear of the vehicle body is limited to the clearance dimension δ by the stopper portion 22a. When an external force acts on one end of the rack shaft 5 from the front of the vehicle body, the rack shaft 5 does not bend more than the clearance dimension δ at the position D of the stopper portion 22a. For this reason, the amount of deflection of the rack shaft 5 is small.
When a larger external force P acts, the stopper portion 22
the distance L ₄ is shorter from the position D of a to the point of action of the external force P, the maximum bending moment Ma acting on the rack shaft 5,
It is extremely smaller than the maximum bending moment Mb.

From the above, if the external force P is small due to the road surface reaction force during normal traveling, particularly during normal steering (hereinafter, referred to as "normal external force P"), the rack shaft 5 is not used. Since the deflection amount is small, it does not hit the stopper portion 22a. Since it does not hit the stopper portion 22a, the rack shaft 5 operates smoothly. On the other hand, if the external force P is large due to the excessive road surface reaction force (hereinafter, referred to as “excessive external force P”), the rack shaft 5 has a large amount of deflection, so that the stopper 2
It corresponds to 2a. For this reason, the rack shaft 5 can be protected from an excessive external force P.

In general, since the rack shaft 5 has a smaller mechanical strength at the portion where the rack teeth 5a are provided than the other portions, it is necessary to give sufficient consideration to an excessive external force P. On the other hand, in the present embodiment, since the amount of bending of one end of the rack shaft 5 toward the rear of the vehicle body is limited, the portion having the rack teeth 5a can be sufficiently protected from excessive external force P.

In the above embodiment of the present invention,
Stopper portion 5a provided on steering gear box 21
May be any as long as it limits the amount of deflection of one end of the rack shaft 5 toward the rear of the vehicle body, and may have, for example, the following configuration. FIG. 9 is a modified example of the stopper portion according to the present invention, and shows a modified example of the configuration shown in FIG. The first housing 22 has a protruding stopper 22 inside one end thereof.
b. Therefore, the clearance S ₂ of a predetermined size between the surface and the stopper portion 22b after the rack shaft 5 [delta]
(Hereinafter, referred to as “gap size δ”), the amount of deflection of the rack shaft 5 at the position of the stopper portion 22b can be limited to within the gap size δ.

In the above embodiment of the present invention,
The one end and the other end of the rack shaft 5 are not limited to only the ends of the rack shaft 5 but simply refer to positions for engaging the pinion 4 or assembling the ball screw 9 for convenience. is there. Further, the rack guide 50 only needs to apply a preload to the rack shaft 5 with an appropriate pressing force and press the rack shaft 5 against the pinion 4. For example, the presence or absence of the compression spring (elastic member) 52 is optional. is there.

[0037]

According to the present invention, the following effects are exhibited by the above configuration. According to the first aspect of the present invention, a rack tooth is formed on the front surface of one end of a rack shaft extending in the vehicle width direction, a pinion is engaged with the rack tooth, and a rack guide for pushing a rear surface of the rack shaft is attached. In the electric power steering device, a screw portion is formed at the other end of the rack shaft, a nut is attached to the screw portion, and an auxiliary torque corresponding to a steering torque is applied to the rack shaft via the nut. The rack shaft, the pinion, the rack guide, and the nut are collectively housed in a steering gear box, and a stopper portion for limiting the amount of deflection of one end of the rack shaft is provided in the steering gear box. It is characterized by having been provided.

An external force or moment (hereinafter, referred to as "moment") caused by the road surface reaction acts on both ends of the rack shaft. When the other end of the rack shaft is bent away from the pinion by the moment and the screw mechanism (combination of the screw portion and the nut), the rack shaft is supported only by the screw mechanism and the rack guide. On the other hand, when the other end of the rack shaft is bent in a direction in which the rack shaft is pressed against the pinion, the rack shaft has a structure in which bending can be suppressed by a screw mechanism, a rack guide, and a pinion. Therefore, the mode (mode) of bending or bending differs depending on the bending direction of the rack shaft. That is, when the rack shaft is deformed in the front-rear direction of the vehicle body by the road surface reaction force and the screw mechanism, the swing waveform when deforming forward and the swing waveform when deforming rearward have asymmetric shapes. Since the swing waveform is asymmetric,
The natural frequency of the rack shaft differs depending on the bending direction, and there is no fear of vibration amplification due to resonance. As a result, vibration of the rack shaft can be easily suppressed. When the vibration of the rack shaft is suppressed, the vibration of the steering handle is also suppressed, so that the steering feeling is enhanced. Further, since vibration transmitted to the vehicle interior via the steering handle is suppressed, noise in the vehicle interior can be prevented.

When an external force or moment (hereinafter, referred to as "normal external force") due to a road surface reaction force during normal running, particularly during normal steering, acts on the rack shaft, the rack shaft has a small amount of deflection. Therefore, it does not hit the stopper. The rack shaft operates smoothly because it does not hit the stopper. as a result,
A good steering feeling can be maintained during normal running, particularly during normal steering. On the other hand, when an external force or a moment (hereinafter, referred to as “excessive external force”) caused by an excessive road surface reaction force acts on the rack shaft, the rack shaft hits the stopper because the amount of deflection is large. For this reason, the rack shaft can be protected from excessive external force. Therefore, the reliability of the electric power steering device is further improved. Further, since the stopper portion is simply provided in the steering gear box, there is no need to increase the number of parts. For this reason, the productivity of the electric power steering device increases.

[Brief description of the drawings]

FIG. 1 is a system diagram of an electric power steering device according to the present invention.

FIG. 2 is an overall configuration diagram of an electric power steering device according to the present invention.

FIG. 3 is a sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is a sectional view taken along line 4-4 in FIG. 2;

FIG. 5 is a sectional view taken along line 5-5 of FIG. 2;

FIG. 6 is a sectional view of a main part around a rack shaft, an electric motor, and a ball screw according to the present invention.

FIG. 7 is an operation explanatory view (first) of the electric power steering device according to the present invention;

FIG. 8 is a view for explaining the operation of the electric power steering apparatus according to the present invention (second).

FIG. 9 is a modified example of the stopper according to the present invention.

FIG. 10 is a schematic explanatory view of a conventional electric power steering device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 2 ... Steering handle, 3 ... Rack and pinion mechanism, 4 ... Pinion, 5 ... Rack shaft, 5a ... Rack teeth, 5b ... Screw part, 8
... electric motor, 9 ... ball screw, 21 ... steering gear box, 22a, 22b ... stopper part, 50 ... rack guide, 71 ... nut.

Claims (1)

[Claims] A rack guide is formed on the front surface of one end of a rack shaft extending in the vehicle width direction, a pinion is engaged with the rack teeth, and a rack guide for pushing a rear surface of the rack shaft is attached. In an electric power steering device, a screw portion is formed at the other end portion, a nut is attached to the screw portion, and an auxiliary torque corresponding to a steering torque is applied to a rack shaft via the nut. The rack shaft, the pinion, the rack guide, and the nut are collectively housed in a steering gear box, and a stopper for limiting the amount of deflection of one end of the rack shaft is provided in the steering gear box. An electric power steering device characterized by the above-mentioned.