JP2000177609A - Motor driven power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power steering system which is easy to assemble and has good steer feeling by unitizing a stator and a rotor of a hollow brushless motor. SOLUTION: This device is provided with a rack shaft 5 which is linked with a steering wheel via a rack gear and a pinion gear both installed to a gear box 2, a hollow brushless motor 40 which is composed of a stator 43 comprising a coil annularly arranged inside a stator sleeve fitted inside a motor case 41 installed to the gear box 2, and a rotor 47 comprising a permanent magnet fixed to a rotor sleeve 48 fitted to an outer periphery of a hollow rotary shaft 51 penetrated by the shaft 5, and a ball screw 53 which is composed of a tapped ball groove 55 and a ball both provided at the shaft 5, and a ball nut 54 provided in an inner periphery of a rack gear side end part of the rotary shaft 51. The ball screw 53 is provided between the rack gear and the motor 40.

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 an assist motor mounted on the same axis as a rack shaft connected to a steering wheel and controlling the direction of the wheels.

[0002]

2. Description of the Related Art An electric power steering apparatus is often used to reduce the steering force of a steering wheel to provide comfortable steering.

In recent years, an electric power steering apparatus having an assist motor mounted on the same axis as a rack shaft for controlling the direction of wheels has been used.

[0004] For example, there is an electric power steering apparatus disclosed in Japanese Patent Application Laid-Open No. 10-194140. this is,
A commutator motor is directly connected to the rack shaft.
That is, a hollow output shaft is provided on the same axis as the shaft,
A wound rotor is fixed to the hollow output shaft. Also,
A motor case is attached to the gear box, and a permanent magnet as a stator is fitted inside the motor case. The rotor winding is energized via a commutator.

On the other hand, the rack shaft is provided with a rack gear on one side and a ball screw on the other side with respect to the motor.
The ball screw is rotated according to the rotation of the motor to apply a thrust as an assist torque to the shaft.

[0006]

The above structure is generally assembled as follows.

A rotor around which a coil is wound and a brush are attached to the hollow output shaft.

This hollow output shaft is fixed to a gear box.

A rack shaft with a ball screw is inserted into the hollow output shaft integrated with the gear box (from the left side in the figure).

[0010] A motor case having a permanent magnet mounted inside is mounted.

At this time, when assembling them, it is desired that the above-mentioned steps can be performed as an assembling operation only from the left side of the gear box, for example, from the advantage that the assembling operation can be made more efficient and automated.

However, in the above configuration, the rotor around which the coil is wound is provided on the outer periphery of the hollow output shaft, and the outer diameter is larger than the large diameter portion in which the ball screw is stored. It had the following problems.

(1) Since the motor is a winding rotor,
A commutator for energization is required, cost is increased, and a problem of abrasion of the commutator also occurs, and maintenance of the commutator is troublesome.

(2) Since the coil is a wound rotor, the motor has a large inertia and adversely affects the steering feeling.

Therefore, in order to solve these problems,
It is considered that a brushless type motor is used, but in that case, a new problem occurs.

That is, structurally, a stator having a coil wound around the motor case is mounted on the motor case side, and a rotor made of a permanent magnet is mounted on the hollow output shaft side.
The inner diameter on the stator side is much smaller than that of the conventional type. Then, the large diameter portion for storing the ball screw is located at the left end (left end from the stator) of the hollow output shaft in a state where the diameter is larger than the inner diameter of the rotor, and when attaching the motor case to the hollow output shaft, The large-diameter portion interferes with the stator of the motor case, causing a problem that the above-described assembling operation from one direction cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a power steering system in which a stator and a rotor of a hollow brushless motor are unitized to be easily assembled and have a good steering feeling. Is to do.

[0018]

Means adopted by the present invention to solve this problem will be described with reference to the reference numerals used in the embodiments. In other words, the means mounted on the gear box 2 is connected via a rack gear 5b and a pinion gear 5a. A rack shaft 5 connected to the steering wheel 1 and a stator 43 having windings annularly arranged in a stator sleeve 46 fitted in a motor case 41 attached to the gear box 2. A hollow brushless motor 40 comprising a rotor 47 having a permanent magnet 49 fixed to a rotor sleeve 48 fitted on the outer periphery of a hollow rotary shaft 51 through which the shaft 5 passes; The provided screw-shaped ball groove 55 and the ball, and the rack gear 5 of the rotary shaft 51
a ball nut 53 provided on an inner peripheral portion of the b-side end portion;
3 is provided between the rack gear 5b and the motor 40, which is a feature of the first invention.

According to a second aspect of the present invention, the rotation sensor 61 includes a rotor 47 sandwiched between the hollow rotation shaft 51 by the rotor sleeve 48 and a sensor sleeve 66 fitted in the motor case 41. It is characterized in that it is composed of the stator 43 to be mounted.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. First, the electric power steering system will be described with reference to FIGS.

When the steering wheel 1 is operated, its steering torque is transmitted to the input shaft 3 of the gear box 2, transmitted to the output shaft 4 via a torsion bar 21 described later, and passed through the pinion gear 5 a at the lower end of the output shaft 4. The rack shaft 5 having the rack gear 5b is driven. This shaft 5 changes the direction of the wheels 7 on both sides via a steering link 6.

The torsion bar 21 generates a torsion angle (a detected amount of torque) according to the steering torque. The potentiometer 30 is rotated according to the twist angle. Although not shown, the potentiometer 30 is composed of a rotating brush and a resistor in contact with the brush, and outputs a voltage corresponding to the rotation angle. This output voltage is input to an electric control device (hereinafter referred to as ECU) 8. And ECU
The motor 40 is driven based on the signal from the motor 8.

The assist torque of the motor 40 is
, The operability is remarkably improved.

Next, the torsion bar type steering torque detecting device 20 will be described with reference to FIG.

The input shaft 3 and the output shaft 4 are rotatably mounted on a gear box 52 for a torque detector. The upper end of the torsion bar 21 is integrated with the input shaft 3 by the pin 22, and the lower end is integrally press-fitted into the hole 4 a of the output shaft 4. Therefore, the torque input to the input shaft 3 is transmitted to the output shaft 4 via the torsion bar 21.

On the other hand, a sleeve 23 is fitted outside the input shaft 3. The sleeve 23 has a long groove 24 parallel to the axial direction and an inclined groove 25. Then, a pin 26 fixed to the output shaft 4 is inserted into the long groove 24,
A pin 27 fixed to the input shaft 3 is inserted into the inclined groove 25. That is, the sleeve 23 moves in the axial direction with respect to the output shaft 4, but does not rotate in the circumferential direction.

Here, the steering torque is changed from the input shaft 3 to the output shaft 4.
When the torque is transmitted to the torsion bar 21, a torsion angle is generated in the torsion bar 21, and a circumferential displacement occurs between the input shaft 3 and the output shaft 4. Therefore, the pin 27 fixed to the input shaft 3 moves in the inclined groove 25, and the sleeve 23 moves up by the dimension H. The steering torque detecting device 20 extracts the dimension H as a detection amount, and a step portion 28 is formed on the outer peripheral surface of the sleeve 23. A lever 31 is in contact with the step portion 28 and transmits the movement amount (dimension H) of the sleeve 23 to the potentiometer 30 as a rotation angle.

Next, the motor 40 will be described with reference to FIGS. The principle is that of a well-known brushless motor.
While the unitization of the rotor 3 and the rotor 47 will be described in detail,
The position of the rotor 47 is detected by a rotation sensor 61 described later, and a three-phase stator winding 45 is detected by a control device (not shown).
Are switched to form a rotating magnetic field.

The motor case 41 has a cylindrical shape, is inserted into the outer peripheral portion 2 b of the gear box 2, and is fixed by screws 42.

In the stator 43 of the present invention, a three-phase stator winding 45 wound around a stator core 44 is annularly disposed and fitted in a stator sleeve 46 made of a magnetic material. After being configured as a unit, it is inserted into the motor case 41 and fixed by appropriate means such as bonding or screwing.

The rotor 47 of the present invention has a permanent magnet 49 of N pole and S pole on the outer peripheral surface of a rotor sleeve 48 made of a magnetic material.
Are arranged alternately and configured as a unit in advance,
The rotor sleeve 48 is fixed to the outer periphery of the hollow rotary shaft 51 by, for example, bonding. The rack shaft 5 passes through the center of the rotating shaft 51.

The winding 45 is supplied with power from a power supply line 50 passing through the motor case 41. Note that a ball bearing 60 is interposed between the rotor shaft 48 and the motor case 41 on the rotating shaft 51.

Although the length of the motor 40 varies depending on the type of vehicle in which the electric power steering device is used, in the present embodiment, the stator 43 and the rotor 47 are fixed in advance so as to be longer than the standard type. If it is press-fitted into the child sleeve 46 and the rotor sleeve 48 and stored as a stock part, the ends of the stator sleeve 46 and the rotor sleeve 48 can be processed to predetermined dimensions and used as needed. Therefore, it can correspond to various things.

As shown in FIGS. 1 and 2, the hollow rotary shaft 51 has a large-diameter portion 52 at the end on the rack gear 5b side. The ball screw 53 has a well-known configuration including a ball nut 54, a threaded ball groove 55 provided on the rack shaft 5 and a ball, and the ball nut 54 is mounted on the large-diameter portion 52. .

The hollow rotary shaft 51 is previously
Inserts the rack shaft 5 mutually screwed from the right direction in the figure through the balls supported by the screw-shaped ball grooves 55, and screw the perforated nut 56 into the threaded portion of the inner periphery of the rotating shaft 51. The ball nut 54 is unitized by tightening together.

A thrust bearing 57 is attached to the outer periphery of the rotating shaft 51 in contact with the large diameter portion 52. Then, the unitized rotating shaft 51 is inserted into the inner peripheral portion 2a of the gear box 2 and the nut 58 is tightened, so that the rotating shaft 51 is rotatably fixed to the gear box 2 (see FIG. 4). .

The rotation sensor 61 of the present invention is mounted between the hollow brushless motor 40 and the ball screw 53 as shown in FIGS. This is iron core 62
And a rotor 65 having a non-circular outer shape and generating a sinusoidal voltage on the stator winding 63 in accordance with the rotation of the rotor 65. It is.

The stator 64 is inserted into the motor case 41 together with the sensor sleeve 66 after being inserted into the sensor sleeve 66, and is inserted between the stator sleeve 46 and the gear box 2.

The stator 64 is rotatable in the circumferential direction when inserted into the sensor sleeve 66, and is press-fitted in the axial direction with the stator sleeve 46 by press-fitting the fixing ring 67 to the end.・ Fixed. Therefore, the stator 64
Is not deformed in the radial direction by the press-fit stress when inserted into the sensor sleeve 66, so that the gap between the rotors 65 is kept uniform.

Further, the motor 40 is mounted on the sensor sleeve 66.
A magnetic shield part 68 for partitioning the both is formed on the end face on the side. Further, the rotor 65 of the present invention is mounted on the outer periphery of the rotating shaft 51 and is clamped and fixed between the rotor sleeve 48 and the step of the rotating shaft 51.

Next, these assembling procedures will be described.

(1) Assembly of the rotor 47 As shown in FIG. Fix it. Next, the rotor 65 of the rotation sensor 61 is inserted while inserting the rotor 65 of the rotation sensor 61 and the rotor sleeve 48 to which the permanent magnet 49 is attached. The rotor sleeve 48 has a rotating shaft 5
1 is fixed by an adhesive. The rotor 47 of the motor 40 and the rotor 65 of the rotation sensor 61 are fixed by adjusting the mounting angle in the circumferential direction to a preset relationship.

(2) Assembly of Motor Case 41 and Stator 43 As shown in FIG. 3, a ball bearing 60 was inserted into the inner peripheral portion of the motor case 41 from the right side in the drawing, and the stator 43 was attached. Insert the stator sleeve 46. Finally, the sensor sleeve 66 to which the stator 64 of the rotation sensor 61 is attached is inserted. In this case, the stator 64 is movable in the circumferential direction with respect to the sensor sleeve 66.

(3) Assembling of the rotor 47 As shown in FIG. 4, a ball nut 54 is mounted on the large diameter portion 52 of the rotating shaft 51, and a screw portion (not shown) of the inner peripheral portion of the large diameter portion 52 is provided. When a nut 56 having a hole is screwed into the nut, the ball nut 54 is fixed to the rotating shaft 51. Then, this unit is moved from the left side in the figure to the inner peripheral portion 2 of the gear box 2.
a, and a ring-shaped fixing nut 58 is screwed and tightened, so that the rotating shaft incorporating the ball nut 54 is rotatably fixed to the gear box 2.

(4) Assembly of Motor Case 41 As shown in FIGS. 1 and 5, the stator 6 of the rotation sensor 61
4 is moved in the circumferential direction to finely adjust the mounting angle with the rotor 65, and then the fixing ring 67 is press-fitted into the sensor sleeve 6.
Fix to 6.

Then, the motor case 41 is inserted into the outer peripheral portion of the rotating shaft 51 from the left side in the figure, fitted into the outer peripheral portion 2 b of the gear box 2, and fixed by screws 42.

(5) Thereafter, although not shown, the pinion gear 5a is assembled to the rack gear 5b.

According to the above embodiment, the following effects can be obtained. (1) Since the ball screw 53 is provided between the motor 40 and the pinion gear 5a and the rack gear 5b,
Since the hollow rotary shaft 51 and the motor case 41 in which the b and the ball screw 53 are unitized can be sequentially assembled to the gear box 2 from one direction, the assembly is easy and the number of assembly steps can be reduced. (2) Since the motor 40 is a brushless motor, no commutator is required, the machine is not worn, the structure is simple, and the cost can be reduced. (3) Since the stator 43 and the rotor 47 of the motor 40 are attached to the stator sleeve 46 and the rotor sleeve 48, respectively, and are unitized in advance, the inertia of the rotor 47 can be reduced and the unit production efficiency can be improved. , Motor 4
The work of arranging 0 on the same axis as the rack shaft 5 can be extremely easily performed. (4) The rotation sensor 61 also includes the rotor 65 and the stator 64, respectively.
Since the units can be assembled independently of each other, assembly and adjustment work can be easily performed.

[0049]

The present invention provides a rack shaft mounted on a gear box and connected to a steering wheel through a rack gear and a pinion gear, and a stator sleeve fitted in a motor case mounted on the gear box. And a rotor having a permanent magnet fixed to a rotor sleeve fitted on the outer circumference of a hollow rotary shaft through which the shaft passes. A motor, a ball screw provided with a screw-shaped ball groove and balls provided on the shaft, and a ball nut provided on an inner peripheral portion of a rack gear side end of the rotating shaft; and Since the motor is provided between the rack gear and the motor, the motor does not require a commutator, the mechanical wear thereof is small, the structure is simple, and the hollow rotating shaft and the fixed shaft are fixed. Since the motor side and the rotor side can be unitized respectively, the motor can be assembled sequentially from one direction, assembling is easy, the number of man-hours can be reduced, and multi-products can be handled. This has a practically excellent effect that it can be easily performed and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view showing an embodiment of the present invention.

FIG. 2 is a front view of a first step showing an assembling process.

FIG. 3 is a front view of a second step showing an assembling process.

FIG. 4 is a front view of a third step showing an assembling process.

FIG. 5 is an enlarged sectional view of a motor and a rotation angle detection sensor.

FIG. 6 is an enlarged vertical sectional side view of the motor.

FIG. 7 is an enlarged vertical sectional side view of a rotation angle detection sensor part.

FIG. 8 is a diagram illustrating a system of the electric power steering device.

FIG. 9 is a longitudinal sectional view of the steering torque detecting device.

FIG. 10 is a view showing a mounting state of a potentiometer.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 steering wheel 2 gear box 5 rack shaft 5 a pinion gear 5 b rack gear 40 motor 41 motor case 43 wire wound stator 44 stator core 45 stator winding 46 stator sleeve 47 rotor 48 rotor sleeve 49 permanent magnet 51 hollow rotation Shaft 52 Large diameter portion 53 Ball screw 54 Ball nut 55 Threaded ball groove 61 Rotation sensor 62 Iron core 63 Winding 64 Stator 65 Rotor 66 Sensor sleeve 67 Fixing ring

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3D033 CA02 CA03 CA04 CA16 CA28 5H019 BB02 BB09 BB19 CC03 DD01 EE14 FF01 FF03 5H611 AA01 BB08 PP05 QQ01 QQ03 RR01 TT01 UA04

Claims (2)

[Claims] 1. A rack shaft mounted on a gear box and connected to a steering wheel via a rack gear and a pinion gear; and a winding wound in a stator sleeve fitted in a motor case mounted on the gear box. A hollow brushless motor comprising a stator arranged in an annular shape, and a rotor having a permanent magnet fixed to a rotor sleeve fitted to the outer periphery of a hollow rotating shaft through which the shaft passes; A threaded ball groove and balls provided on the shaft,
An electric power steering, comprising: a ball screw provided on an inner peripheral portion of a rack gear side end of the rotating shaft; and a ball screw provided between the rack gear and a motor. apparatus. 2. The motor according to claim 1, wherein the rotation sensor comprises a rotor that is sandwiched by the rotor sleeve on the hollow rotation shaft, and a stator that is mounted on the sensor sleeve fitted in the motor case. The electric power steering apparatus according to claim 1, wherein: