JPH10152058A - Electrically driven power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce costs by changing conventional three-point supporting to two-point supporting in a rack shaft, and relieving member processing precision and the like. SOLUTION: This electrically-driven power steering device is provided with a rack shaft 2 linked to a steering wheel, a housing A which contains the rack shaft 2 so as to slide freely and retains an engaging part 6 where a rack tooth formed at the rack shaft is engaged with the pinion of a steering shaft 5 linked to a steering wheel, and a motor 1 which is formed at the periphery of the rack shaft 2 coaxially and whose torque is transmitted to the rack shaft 2 as steering auxiliary force through a ball screw mechanism 3. The nut part 19 of the ball screw mechanism 3 is supported on a housing B so as to rotate freely, which is formed with the armature shaft 11 of the motor 1 supported separately from the housing A. The rack shaft 2 is supported at two points of the engaging part 6 and the nut part 19 supported on the housing B so as to move freely in the axial direction.

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 device for a vehicle, and more particularly to a technique effective when applied to an electric power steering device used for a rack and pinion type steering device. is there.

[0002]

2. Description of the Related Art In recent years, many vehicles are equipped with a so-called power steering device for assisting the steering force of the vehicle, and various power steering devices such as a hydraulic type and an electric type have been proposed. Among such power steering devices, an electric power steering device (so-called electric power steering) applied to a rack and pinion type steering device includes:
As disclosed in Japanese Patent Application Laid-Open No. 8-98451, an electric motor provided coaxially with a rack shaft to obtain a steering assist force is known.

In such an electric power steering apparatus, as shown in FIG. 4, an electric motor 52 is provided coaxially with a rack shaft 51, and a steering assist force generated by the electric motor 52 is transmitted to a rack through a ball screw mechanism 53. It is transmitted to the shaft 51. Then, the steered wheels are steered by the steering assist force and the manual steering force,
The driver's steering burden is reduced.

In this case, the rack shaft 51 is connected at both ends to steered wheels via tie rods or knuckle arms and the like, and is connected to a steering shaft 54 connected to a steering handle or the like by rack and pinion. The driver reciprocates in the left-right direction in FIG. 4 by the steering operation of the driver. The electric motor 52 has a configuration in which a cylindrical armature shaft 56 and a field device 57 are coaxially inserted into a cylindrical yoke 55, and power is supplied from a power supply unit 58. Further, the field device 57 includes a magnet 59 attached to the inner periphery of the yoke 55 and an armature core 60 attached to the outer periphery of the armature shaft 56. The rotational force generated by the electric motor 52 is transmitted as a reciprocating motion in the axial direction to the rack shaft 51 via a ball screw mechanism 53 provided at the left end of the armature shaft 56 in the drawing, thereby assisting the steering force.

In the power steering apparatus having such a configuration, the rack shaft 51 is supported at two points, that is, the joint portion with the steering shaft 54 and the ball screw mechanism 53. That is, first, one end of the rack shaft 51 has high rigidity because the rack shaft 51 and the steering shaft 54 are gear-coupled by a rack and pinion, and this is one of the support points when viewed from the rack shaft 51 side. It has become. Further, since the housing 61 holding the connecting portion is fixed to the vehicle body, the rack shaft 51 is supported by the vehicle body by this portion. Next, the other end of the rack shaft 51 is supported by a ball screw mechanism 53 provided at an end of the armature shaft 56. In this case, the ball screw mechanism 53 is in a state where the nut portion 62 and the screw portion 63 are assembled without looseness via the ball 64.
Further, the nut portion 62 is press-fitted or inserted into the armature shaft 56 and fixed by caulking, which also serves as one of the support points of the rack shaft 51.

On the other hand, the armature shaft 56 is rotatably supported by two points, a ball screw mechanism 53 and an angular bearing 65. In this case, the ball screw mechanism 53 is connected to the armature shaft 56 as described above.
From the side, it is one of the supporting points. Also,
The angular bearing 65 is mounted on the housing 61 without play, which is also one of the support points.

The characteristics of the power steering apparatus are measured as follows. In this case, the nut 62 of the ball screw mechanism 53 is connected to the armature shaft 56.
After attaching the motor 52 to the yoke 5
If the motor 5 is assembled, the entire device will be covered, and the characteristics of the electric motor 52 will be measured from the thrust of the rack shaft 51. That is, since the characteristics of the electric motor 52 alone cannot be measured directly, First, nut part 6
Perform measurement without attaching 2. That is, the nut portion 62
The electric motor 52 is assembled by covering the yoke 55 without the motor. Next, the rotation speed and the torque of the electric motor 52 are taken out by using the part to which the nut part 62 should be originally attached. Then, after the measurement, the yoke 55 is removed, the nut portion 62 is attached, and the yoke 55 is covered again to obtain a finished product.

[0008]

However, in such a power steering apparatus, although the rack shaft 51 is directly supported at the above two points, it is connected through the ball screw mechanism 53. The other end of the armature shaft 56 is supported by an angular bearing 65 attached to the housing 61, so that the armature shaft 56 takes a three-point support form in effect. For this reason, there is a problem that friction due to backlash, twisting, or misalignment of the rack shaft 51 is likely to occur, which may cause abnormal noise, deteriorated steering feeling, and defective steering wheel return. On the other hand, in order to prevent such a problem from occurring, there is a problem that extremely strict accuracy is required for each member and their assembling, and the manufacturing cost is increased in terms of processing accuracy and product management.

In the power steering apparatus, the yoke 55 is once attached for measuring the characteristics of the electric motor 52, and is removed and then assembled again. Therefore, it takes time and effort to measure the characteristics, and the characteristics of the electric motor 52 may change between the time of measurement and the time of completion. In this case, the operating characteristics in the final state were not measured, and only the characteristics of the electric motor 52 were estimated from the data before reassembly.

On the other hand, since a yoke to which a magnet that has already been magnetized is attached is difficult to combine with an armature, generally, an unmagnetized yoke is assembled to form a finished product, and then the yoke is magnetized. A method is adopted. However, in the electric motor 52, since the yoke 55 is once pulled out after the characteristics are measured after being magnetized, there is a problem that the difficulty associated with the removal of the yoke 55 always follows. That is, it is not easy to remove the first magnetized yoke 55 first. Secondly, when the yoke 55 is reattached, the opposing member is attracted by magnetism and is vigorously hit, and the impact may damage the respective parts.

It is an object of the present invention to provide an electric power steering apparatus in which a conventional three-point support on a rack shaft is changed to a two-point support, thereby reducing member processing accuracy and the like and reducing costs. .

It is another object of the present invention to provide an electric power steering apparatus which can easily measure the operating characteristics of an electric motor alone and does not cause the above-mentioned problems due to a magnetized yoke. .

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0014]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, the electric power steering apparatus according to the present invention comprises a rack shaft connected to a steering wheel, a rack shaft slidably housed, and rack teeth formed on the rack shaft. A first housing that holds a coupling portion that meshes with a pinion of a steering shaft connected to a steering wheel, an electric motor that is provided coaxially around the rack shaft and supplies a steering assist force to the rack shaft, and an armature of the motor An electric type having a ball screw mechanism for connecting a nut portion connected to a shaft and a screw portion formed on a rack shaft with a ball member interposed therebetween and transmitting the torque of the electric motor to the rack shaft as steering assist force. It is intended for power steering devices. The nut portion of the ball screw mechanism is rotatably supported by a second housing formed separately from the first housing while supporting the armature shaft of the electric motor. And the nut portion supported by the second housing is movably supported in the axial direction.

In this case, the second housing can be formed so that its mounting position can be adjusted to correct the misalignment of the rack shaft.

Further, the power supply portion of the motor may be disposed on the second housing side of the field device of the motor, whereby the power supply portion can be assembled with high rigidity and high accuracy. As a result, it is possible to reduce the brush noise, reduce the advance angle deviation, improve the rectification, and the like.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view showing the overall configuration of an electric power steering apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a main portion of the electric power steering apparatus shown in FIG. It is an expanded sectional view of.

An electric power steering device (hereinafter, abbreviated as a power steering device) according to the first embodiment, as shown in FIGS.
Similar to the conventional power steering device shown in FIG. 4, a hollow electric motor 1 is arranged around a rack shaft 2, and is attached as a steering device for steering wheels such as front wheels of an automobile. The steering assist force generated by the electric motor 1 is transmitted to the rack shaft 2 via the ball screw mechanism 3 to reduce the driver's steering burden. In the power steering apparatus according to the present invention, the rack shaft 2 conventionally supported by three points is changed to a two-point support by integrally providing the ball screw mechanism 3 and the angular bearing 4, whereby the precision of the parts and the assembly are improved. This is to reduce the accuracy.

As shown in FIG. 1, the power steering apparatus according to the first embodiment includes a housing A (first housing), a yoke 7 of the electric motor 1, and a housing B (second housing).
Are integrally connected by a plurality of screws 8a and 8b, respectively, and the rack shaft 2 is mounted inside thereof so as to be slidable in the left-right direction. Steering wheels are connected to both ends of the rack shaft 2 via tie rods, knuckle arms, and the like in a state where the steering wheels are attached to the vehicle body by the mounting holes 10 of the bracket 9 and housing B.

The housing A is a hollow member made of cast iron or aluminum die-cast, and has a joint 6 between the steering shaft 5 and the rack shaft 2 connected to the steering handle at the right end in FIG. I have. In the connecting portion 6, a pinion (not shown) provided on the steering shaft 5 and a rack tooth (not shown) formed on a side portion of the rack shaft 2 mesh with each other. Is converted to left and right movement. In this case, the coupling portion 6 is configured to support the rack shaft 2 by meshing gears, and is one of the rack shaft support points as in the conventional power steering device. A torque sensor (not shown) for detecting the rotational torque of the steering shaft 5 is provided on the shaft of the connecting portion 6, and the auxiliary steering force of the electric motor 1 is controlled based on the detected value.

Next, the motor 1 has a configuration in which a cylindrical armature shaft 11 and a field device 12 are coaxially inserted into a cylindrical yoke 7. Then, the rack shaft 2 is assembled so as to pass through the inside of the armature shaft 11. The field device 12 includes a magnet 14 attached to the inner periphery of the yoke 7 and an armature core 15 attached to the outer periphery of the armature shaft 11. Supplied.

The yoke 7 is a cylindrical member made of iron, and is formed with a substantially constant thickness by a cylindrical pipe. The field device 12 and the power supply unit 13 are accommodated therein. The right side of the yoke 7 in the figure is connected to the housing A by a plurality of screws 8a, and the space between the housing A and the O-ring 16 is airtight. Further, the left side thereof is connected to the housing B by a plurality of screws 8b, and the connection therebetween is performed in a form in which the misalignment of the rack shaft 3 is adjusted as described later.

A plurality of magnets 14 as field poles constituting the field device 12 are arranged in the yoke 7 at intervals in the circumferential direction. On the other hand, the armature shaft 11 has one end (the right end in FIGS. 1 and 2) held by a bearing 17 attached to the housing A.
A tapered spline 18 is formed on the other end side (the left end in FIGS. 1 and 2).
Spline 2 similarly formed at the end of nut portion 19
0 is fitted. Thus, the rotation of the armature shaft 11 is transmitted to the nut 19. In addition,
Armature shaft 1 used in the power steering device
1 is simpler and smaller in size than the conventional one as shown in FIG. For this reason, the cost required for this can be reduced, and the inertia thereof can be reduced.
It is also possible to reduce the size and improve the response speed.

On the other hand, a rubber 21 is provided on the right side of the bearing 17.
The armature shaft 11 is pressed against the nut portion 19 by the elastic force of the rubber 21. Therefore, the spline 18 is engaged with the spline 20 while being pressed against the spline 20, and the rotation of the armature shaft 11 is reliably transmitted to the nut portion 19.
Thus, since the rubber 21 is interposed on the right side of the bearing 17, the armature shaft 11 is supported with some room for movement.
As long as the rubber 21 is an elastic body that exerts a pressing force in the axial direction, its material and form are not limited, and for example, a disc spring, a wave washer, a synthetic resin, or the like can be used.

Next, the power supply section 13 is a section for supplying electric power to the armature, and has a commutator 22 fixed to the armature shaft 11 and a brush 23 which is an electrical contact with the peripheral surface of the commutator 22. It has a configuration. In this case, the brush 23 is held in a brush holder integrally formed with a brush holder stay 24 made of a synthetic resin, and comes into sliding contact with the commutator 22 with a predetermined pressing force by an unillustrated elastic machine. On the other hand, one end of the brush holder stay 24 is
A terminal plate 26 spot welded to the third pigtail 25 is insert-molded through the projection 24a. The brush holder stay 24 is provided in the hole 2 of the housing A.
7 and screwed to the housing A in a state where the tip of the protruding portion 24a protrudes outside. This allows
Projection 24 of brush holder stay 24 from housing A
The terminal plate 26 protrudes together with a to form a power supply terminal.

FIG. 3 is a perspective view showing the manner in which the coupler 28 is attached to the power supply terminal thus formed. As shown in FIG. 3, outside the housing A,
A male terminal is formed by projecting the terminal plate 26 together with the protruding portion 24 a, and a coupler 28, which is a waterproof female terminal, is screwed to the male terminal via an O-ring 29. In this case, from the viewpoint of assisting the steering force, the power supply to the electric motor 1 cannot be interrupted even for a moment. However, in the power steering system, the coupler 2
Since the housing 8 is screwed and fixed to the housing A, it is possible to prevent the coupler 28 from coming off due to vibration or the like, thereby preventing the power supply from being interrupted, and to improve the reliability of the product.

By the way, in the conventional power steering device, as shown in FIG. 4, this terminal portion is fixed by inserting a coupler 67 (male side) integrally formed with the terminal 66 into the housing 61 and fixing the terminal 66 to the terminal 66. One end is fixed to the pigtail 68 of the brush. However, in such a conventional power steering device, the terminal 66 and the pigtail 68 are spot-welded after the coupler 67 is attached to the housing 61. Therefore, in the conventional power steering device, it is necessary to fix the housing 61 having a large size to perform the welding operation, and there is a problem that workability is poor. Also, since the coupler 67 has a non-disassembled structure, when replacing the brush, it is necessary to replace the entire housing 61 or to cut the pigtail 68 and the terminal 66 to replace the brush, and then perform welding again. Was.

In view of the above, in the power steering apparatus, the terminal structure as described above is adopted, and spot welding is performed between the brush holder stay 24 and the pigtail 25 to improve the workability by sub-assembly. . In addition, since the brush A and the housing A can be disassembled, it is sufficient to replace the brush holder stay 24 when replacing the brush 23, and the replacement part can be reduced and the workability can be improved. Further, the number of parts is one less than that of the conventional case (the coupler 67 in FIG. 4 is unnecessary), which also contributes to a reduction in parts costs.

Next, similarly to the housing A, the housing B is a hollow member made of cast iron or aluminum die cast, and has a ball screw mechanism 3 incorporated therein. The ball screw mechanism 3 generally includes a nut 19, a screw 30 formed on the outer periphery of the rack shaft 2, and a number of balls 31 interposed between the nut 19 and the screw 30. It has a simple configuration. Then, the rack shaft 2 holds the nut portion 1 in a state where rotation around the shaft is restricted.
9 supports the nut part 1
9 moves in the left-right direction with rotation.

Here, the nut portion 19 is held rotatably around the axis with respect to the housing B via an angular bearing 4 fixed to the housing B. That is, in the power steering device, unlike the device of FIG. 4, the nut portion 1 of the ball screw mechanism 3 which is conventionally separately provided.
9 and the angular bearing 4 are integrated and housed in a housing B formed separately from the housing A. In addition, the angular bearing 4
Bearing fixing ring 32 screwed into the opening of housing B and step 33 formed inside housing B
Is fixed in a state where the movement in the axial direction is restricted. The axial movement between the nut 19 and the angular bearing 4 is restricted by a bearing fixing ring 34 screwed into the left end of the nut 19 and a step 35 formed on the outer periphery of the nut 19. Is done.

As described above, the rack shaft 2 of the power steering device is used.
Is supported in a housing B by a nut 19 held by an angular bearing 4 fixed thereto, and the nut 19 is also one of the support points of the rack shaft 2. Incidentally, one end of the armature shaft 11 on the commutator 22 side is also a bearing 1.
7, the bearing 17 has a slight backlash between the inner ring and the outer ring because the bearing 17 has a ball inside. That is, in the power steering device, the rack shaft 2 is supported by two points, that is, the joint 6 of the housing A and the nut 19 of the ball screw mechanism 3. In this respect, the conventional power steering system is practically 3
It has a different configuration from the point support.

On the other hand, a tapered spline 20 is formed on the right end side of the inner diameter of the nut 19 as described above, and the spline 1 of the armature shaft 11 is formed there.
8 are fitted. Thereby, the armature shaft 11 and the nut portion 19 are integrally connected,
The armature shaft 11 is supported by the bearing 17 and the nut 19, and the rotation of the armature shaft 11 is transmitted to the nut 19 without loss. Therefore, when the armature shaft 11 rotates, the nut portion 19 rotates with this rotation, and the rack shaft 2 moves in the left-right direction by the operation of the ball screw mechanism 3.

Since the rack shaft 2 is bent by an external force applied from a steering wheel or the like, a clearance is required between the rack shaft 2 and the armature shaft 11 in consideration of the amount of bending. Conventionally, the relationship between the amount of bending and the position of the support point of the rack shaft 2 has not been considered, and the position of the support point has been set arbitrarily. for that reason,
The clearance has to be set so as to sufficiently cope with the bending of the rack shaft 2, which is one of the factors that makes it difficult to reduce the size of the apparatus. Therefore, in the power steering system, the rack shaft 2 is supported at two points of the ball screw mechanism 3 and the connecting portion 6. Are made equal on both sides to minimize the bending of the rack shaft 2. When the rigidity of the rack shaft 2 is different, the bending of the rack shaft 2 can be minimized by determining the fulcrum position in consideration of the ratio. If the bending of the rack shaft 2 can be minimized in this way, the clearance can be minimized, and the size of the device can be reduced, which is advantageous in cost.

Next, a method of assembling the power steering apparatus having such a configuration and its operation will be described.

In the power steering apparatus, first, the above-mentioned four parts are assembled. That is, in the housing A, the rubber 21, the bearing 17, the brush holder stay 24, and the like are attached. In the yoke 7, the magnet 14 and the like are assembled, and in the armature shaft 11, the armature core 15, the commutator 22, and the like are assembled. Further, in the housing B, the ball screw mechanism 3 in which the angular bearing 4 and the rack shaft 2 are combined is assembled.

Next, the housing A and the armature shaft 11 are assembled, the yoke 7 is screwed to the housing A, and then the housing B on which the rack shaft 2 is mounted and the yoke 7 are screwed. Thereafter, the rack shaft 2 inserted into the housing A and the steering shaft 5 are connected, and the pinion teeth of the steering shaft 5 and the rack teeth of the rack shaft 2 are engaged.

Here, in the power steering apparatus, since the ball screw mechanism 3 is configured to be separable from the armature shaft 11, the characteristics of the electric motor 1 alone can be measured at this time. That is, it is possible to receive the end of the armature shaft 11 by a suitable bearing and measure the rotation speed, torque, and the like of the electric motor 1 alone therefrom.

In this case, when the housing B is attached to the yoke 7, the spline 18 formed at the end of the armature shaft 11 and the spline 20 formed at the nut 19 are engaged with each other to fit the two. 7
And the housing B are screwed. Thereby, in the power steering device, screwing is performed while adjusting the mounting position of the housing B so that the rack shaft 2 does not fall or run out, and the misalignment of the rack shaft 2 due to eccentricity or the like is absorbed and corrected. Can be. The yoke 7 is formed with a hole 36 larger than the diameter of the screw 8b for mounting the screw 8b, and the mounting position of the housing B is adjusted by the clearance.

Here, in the power steering device, the rack shaft 2
Are supported at two points: a joint 6 with the steering shaft 5 on the housing A side and a nut 19 on the housing B side.
At the time of attachment, it is supported only by the coupling portion 6. The armature shaft 11 also has a bearing 1
7 and floated as described above.
Therefore, when the housing B is mounted, the mounting position of the housing B, including the armature shaft 11, can be appropriately shifted according to the misalignment of the rack shaft 2. Accordingly, the nut 19, which is another fulcrum, can be attached in a form absorbing the misalignment of the rack shaft 2, and the play and the reduction of friction can be achieved by adjusting the attachment of the housing B. Therefore, strict component accuracy and assembling accuracy, which are conventionally required, are not required, and the cost of the product can be reduced.

Furthermore, since the housing B can be assembled after measuring the characteristics of the electric motor 1 alone, a complicated process such as removing the yoke 7 again to assemble the electric motor 1 is not required. Therefore, the assembling process is simplified, and the characteristics of the electric motor 1 can be obtained accurately and easily because the characteristics of the electric motor 1 can be obtained in the final product form without detaching the yoke 7 after measurement.

The housing A is attached to the vehicle body by a bracket 9 with an elastic body such as rubber interposed therebetween. In this case, in the conventional power steering device, since the housing on the steering shaft 5 side is rigidly connected to the vehicle body, the sound or vibration generated from the electric motor 1 is easily transmitted to the steering wheel, which is one of the causes of impairing the steering feeling. However, in the power unit, since the steering shaft 5 is attached by the bracket 9 and rubber or the like is interposed between the bracket 9 and the housing A, sound and vibration are attenuated there and become difficult to be transmitted to the steering shaft 5. ing.

On the other hand, the power steering device operates as follows. That is, first, the steering handle is operated to rotate the steering shaft 5, and the rack shaft 2 moves in a direction corresponding to the rotation to perform the steering operation. When a steering torque sensor (not shown) is operated by this operation, the brush 23 is connected to the terminal plate 26 via the coupler 28 in accordance with the detected torque.
Power is supplied to the commutator 22 via. And
As a result, the electric motor 1 operates and the armature shaft 1
1 rotates, and the nut portion 19 connected thereto also rotates. When the nut 19 rotates, the steering assist force is transmitted to the rack shaft 3 by the action of the ball screw mechanism 3. Thereby, the movement of the rack shaft 2 is promoted, and the steering force is assisted.

In the power steering apparatus, even when the rack shaft 2 hits a stopper (not shown) and is stopped by stationary turning or sudden turning during vehicle maintenance, the armature shaft 11 generated on the rack shaft 2 is not affected. No axial reaction force due to inertia is transmitted. That is, the reaction force is transmitted from the rack shaft 2 to the ball screw mechanism 3, the angular bearing 4, the housing B, the yoke 7, and the housing A, and the armature shaft 11 generates only a force in the rotational direction due to its inertia. Therefore, the strength requirements imposed on the armature shaft 11 are reduced, and the production cost can be reduced.

(Embodiment 2) FIG. 5 is a sectional view showing the overall configuration of an electric power steering apparatus according to Embodiment 2 of the present invention. The same parts as those of the power steering apparatus according to the first embodiment are denoted by the same reference numerals, and the details are omitted.

The power steering apparatus according to the second embodiment has a basic configuration substantially similar to that of the power steering apparatus shown in FIG.
As shown in FIG.
That is, it is configured to be disposed on the housing B side.
Thus, the precision and rigidity between the commutator 22 and the brush 23 are improved while maintaining the two-point support structure of the rack shaft 2.

As shown in FIG. 5, in the power steering apparatus, the armature core 15 is mounted in a direction opposite to that of FIG. 1, and the power supply portion 13 is also provided on the housing B side of the armature core 15. ing. That is, the commutator 22 and the brush 23 are arranged in the vicinity of the ball screw mechanism 3 and the angular bearing 4 differently from those in FIG.

On the other hand, the armature shaft 11
As in the case of (1), the nut portion 19 of the ball screw mechanism 3 is connected to the nut portion 19, and the nut portion 19 is also supported by the angular bearing 4 fixed to the housing B. That is, one end of the armature shaft 11 is supported by the housing B via the nut 19 and the angular bearing 4. The commutator 22 is fixed to the armature shaft 11, and in these respects, the apparatus shown in FIG. 5 is not different from the apparatus shown in FIG.

In the apparatus shown in FIG. 5, the nut 19b is inserted into the nut holding tube 19a, and a male screw portion is formed on the outer periphery of the female screw portion formed on the inner periphery of the opening end of the nut holding tube 19a. The provided lock nut 43 is screwed into and fixed so as not to rotate relatively. In addition, the angular bearing 4 is fixed to the step portion 44 of the nut holding cylinder 19b by an inner screw lock nut 45a,
It is mounted and fixed by an external screw lock nut 45b so that the axial movement with respect to the housing B is restricted.

Here, looking at the support point of the armature shaft 11, the left side in the figure is supported by the nut 19 supported by the housing B. On the other hand, the right side in the figure is supported by a bearing 17 supported by the housing A. In this case, the housing B is directly attached to the vehicle body via the mounting hole 10, but the housing B is attached to the vehicle body via an elastic body such as rubber by the bracket 9. That is, the mounting rigidity of the housing B is higher than that of the housing A. In addition, the support by the angular bearing 4 is better for the bearing 1.
7 is more accurate than the support by 7. For this reason, the mounting accuracy and rigidity of the armature shaft 11 are higher on the housing B side than on the housing A side.

Therefore, in the first embodiment, the commutator 2
Although the power steering device 2 is mounted on the housing A of the field device 12, the power steering device of the second embodiment is mounted on the housing B to improve the mounting accuracy and rigidity. That is, the commutator 22 is arranged at a position closer to a support point which is superior to the mounting accuracy and rigidity of the armature shaft 11 as compared with the case of FIG. 1, whereby the commutator 22 has high rigidity and high accuracy. It can be assembled in a state.

Also, in relation to the brush 23, the mounting accuracy of the commutator 22 is improved, so that the mounting accuracy between the two is also improved, thereby reducing the brush noise, the advance angle deviation, and the rectification. And so on.

Incidentally, even in the apparatus shown in FIG.
Is supported by two points, that is, a coupling portion 6 of the housing A to the steering shaft 5 and a nut portion 19 of the ball screw mechanism 3, and has a substantially two-point support structure as in the apparatus of FIG. Needless to say. Also, in the device of FIG.
A configuration in which the brush holder 41 and the coupler 42 are integrated is adopted, thereby reducing costs by reducing the number of parts and the number of assembling steps.

Further, in the above embodiment, the housing B is directly mounted on the vehicle body through the mounting hole 10, but in the second embodiment, the power supply section 13 of the armature core 15 is disposed on the housing B side. Therefore, the mode of attachment to the vehicle body is not limited to the above-described example, for example, the bracket 9 can be attached to the vehicle body without setting the attachment hole 10.

Although the invention made by the inventor has been specifically described based on the embodiment, the invention is not limited to the embodiment and can be variously modified without departing from the gist of the invention. Needless to say,

For example, in the above-described embodiment, the whole is divided into three parts, namely, the housings A and B and the yoke 7, but it is sufficient that the rack shaft 2 can be supported at two points. The form of division of each part such as integrating the yoke 7 is not limited to the above example.

The present invention can also be applied to a motor using a brushless motor that does not use a brush for the power supply unit. In this case, as the field device, the core is fixedly mounted on the yoke side and the magnet is fixedly mounted on the armature shaft side, and the power supply unit is provided with a circuit board provided with a power supply means and an armature shaft rotation position detecting device. Further, the present invention can be applied not only to the front wheel steering device but also to a rear wheel steering device having the same specific configuration and mounting environment.

In the above description, the case where the invention made by the inventor is mainly applied to a power steering device of a vehicle, particularly an automobile, which is an application field thereof, has been described. However, the present invention is not limited to this. It can be widely applied to vehicles having a steering mechanism such as machines.

[0060]

Advantageous effects obtained by typical ones of the inventions disclosed in the present application will be briefly described.
It is as follows.

(1) The rack shaft is supported at two points, that is, the joint and the ball screw mechanism, and the conventional three-point support is replaced with two-point support. This reduces the machining accuracy and assembly accuracy of the components and reduces costs. There is an effect that it can be achieved. Further, it is possible to prevent abnormal noise, deterioration of steering feeling, and the like caused by backlash and twisting of the rack shaft.

(2) Since the mounting position of the second housing for accommodating and holding the ball screw mechanism can be adjusted, there is an effect that the misalignment of the rack shaft can be easily corrected when the second housing is mounted.

(3) By disposing the power supply portion of the motor on the second housing side, the power supply portion can be assembled with high rigidity and high accuracy. Accordingly, it is possible to reduce brush noise, lead angle deviation, and improve rectification.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an entire configuration of a power steering device according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of the power steering device shown in FIG.

FIG. 3 is a perspective view showing a state where a coupler is attached to a power supply terminal.

FIG. 4 is a cross-sectional view showing the entire configuration of a conventional power steering device.

FIG. 5 is a cross-sectional view illustrating an entire configuration of a power steering device according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Motor 2 Rack shaft 3 Ball screw mechanism 4 Angular bearing 5 Steering shaft 6 Coupling part 7 Yoke 8a Screw 8b Screw 9 Bracket 10 Mounting hole 11 Armature shaft 12 Field device 13 Feeding part 14 Magnet 15 Armature core 16 O ring 17 Bearing Reference Signs List 18 spline 19 nut portion 20 spline 21 rubber 22 commutator 23 brush 24 brush holder stay 24a projecting portion 25 pigtail 26 terminal plate 27 hole 28 coupler 29 O-ring 30 screw portion 31 ball 32 bearing fixing ring 33 step portion 34 bearing fixing ring 35 stepped portion 36 hole 41 brush holder 42 coupler 51 rack shaft 52 electric motor 53 ball screw mechanism 54 steering shaft 55 yoke 56 armature shaft 5 7 Field device 58 Power supply section 59 Magnet 60 Armature core 61 Housing 62 Nut section 63 Screw section 64 Ball 65 Angular bearing 66 Terminal 67 Coupler 68 Pigtail A Housing (first housing) B Housing (second housing)

Claims (3)

[Claims] 1. A rack shaft connected to a steering wheel, a rack shaft slidably received therein, a rack tooth formed on the rack shaft, and a pinion of a steering shaft connected to a steering handle. A first housing that holds the engaged coupling portion, an electric motor that is provided coaxially around the rack shaft and supplies a steering assist force to the rack shaft, and a nut portion that is connected to an armature shaft of the electric motor. A ball screw mechanism that connects a screw portion formed on the rack shaft with a ball member interposed therebetween, and transmits a rotational force of the electric motor to the rack shaft as steering assist force. The nut portion of the ball screw mechanism is rotatably supported by a second housing formed separately from the first housing while supporting the armature shaft. Is, the rack shaft, an electric power steering apparatus characterized by being movably supported in the axial direction by two points of the coupling portion and said nut portion supported on the second housing. 2. The electric power steering device according to claim 1, wherein the second housing is formed so that its mounting position is adjustable for correcting misalignment of the rack shaft. Electric power steering system. 3. The electric power steering apparatus according to claim 1, wherein a power supply portion of the electric motor is disposed on the second housing side of a field device of the electric motor. Power steering system.