JP2001159429A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an electric power steering device at a low cast, as well as to reduce the number of assembling processes by reducing the number of parts of a torque limiter. SOLUTION: The torque limiter 10 is provided with a case 11 fixed to an output shaft 3 of an electric motor, a boss 12 coaxially and provided relatively rotatably in relation to the case 11, and a ring member 13 provided between the side surface of the boss 12 and the side surface of the case 11 and having elasticity in the radial 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 apparatus having a torque limiter for absorbing an excessive torque applied to a motor from a driven shaft.

[0002]

2. Description of the Related Art FIG. 19 is a sectional view of a main part of a conventional electric power steering apparatus described in Japanese Patent Application Laid-Open No. 9-84300, and FIG. 20 is an exploded view of the power steering apparatus shown in FIG. The device has an electric motor (not shown) for transmitting an output to a driven shaft, and a torque limiter 2 for absorbing an excessive torque applied to the electric motor from the driven shaft. The torque limiter 2 includes a case 4 fixed to the output shaft 3 of the electric motor, a cover 5 covering the case 4, and a boss 6 spline-engaged with the driven shaft and rotatable relative to the case 4. And a friction plate 8 provided between the boss 6 and the cover 5 via a spring member 7 and rotatable relative to the boss 6. The friction plate 8 is rotatable with respect to the boss 6 and the case 4
Are integrally rotated by engagement with a rotation restricting portion (not shown) formed in the case 4. The friction plate 8 is pressed against the boss 6 by the urging force of the spring member 7. The cover 5 supports the pressing of the spring member 7 and is fixed to the case 4 by caulking its inner peripheral edge inward.

Next, the operation of the electric power steering apparatus having the above configuration will be described. During normal operation, the steering assist torque generated by the electric motor generates a frictional force between the friction plate 8 and the boss 6 and between the boss 6 and the case 4 due to the pressing of the spring member 7. The rotation torque of the output shaft 3 is transmitted to the case 4, the boss 6 integrated with the case 4, and the driven shaft. When an excessive impact force acts on the electric motor from the wheel side via the driven shaft during the normal operation, when the friction plate 8 in the torque limiter 2 and the boss 6 and the boss 6 and the case 4 The boss 6 rotates relative to the case 4 and the output shaft 3 to absorb the impact torque.

[0004]

In the electric power steering apparatus having the above structure, although an excessive impact torque is applied to the electric motor to prevent, for example, the torque transmission mechanism or the electric motor itself from being damaged, the structure of the torque limiter is reduced. The number of parts is large, the number of assembling steps is increased, and the manufacturing cost is increased.

SUMMARY OF THE INVENTION An object of the present invention is to solve such a problem. An electric power steering system in which the number of components of a torque limiter can be reduced, the number of assembling steps can be reduced accordingly, and the manufacturing cost is low. The aim is to obtain a device.

[0006]

In the electric power steering apparatus according to the first aspect of the present invention, the torque limiter includes a fixed member fixed to an output shaft of the electric motor, and a concentric and relative member with respect to the fixed member. A boss rotatably provided and engaged with the driven shaft; and a ring member provided between a side surface of the boss and a side surface of the fixing member and having elasticity in a radial direction. .

In the electric power steering apparatus according to a second aspect of the present invention, the torque limiter is provided between the inner wall surface of the boss and the output shaft of the motor and the boss engaged with the driven shaft. And a ring member having elasticity.

In the electric power steering apparatus according to the third aspect of the present invention, the clearance between the boss on the driven shaft side with respect to the ring member and the fixed member, and the boss on the non-driven shaft side with respect to the ring member. The clearance with the fixing member is different.

In the electric power steering apparatus according to a fourth aspect of the present invention, the clearance between the boss on the driven shaft side with respect to the ring member and the output shaft, and the boss on the non-driven shaft side with respect to the ring member. The clearance between the motor and the output shaft is different.

In the electric power steering apparatus according to a fifth aspect of the present invention, a blocking member for blocking movement of the boss in the axial direction is provided between the boss and the fixed member.

In the electric power steering apparatus according to a sixth aspect of the present invention, a blocking member for blocking movement of the boss in the axial direction is provided between the boss and the output shaft.

In the electric power steering apparatus according to a seventh aspect of the present invention, a groove is formed at a portion of the fixed member where the protrusion of the ring member comes into contact with the protrusion to prevent the boss from moving in the axial direction by engaging with the protrusion. Have been.

In the electric power steering apparatus according to an eighth aspect of the present invention, a groove is formed at a portion of the boss where the projection of the ring member comes into contact with the projection to prevent the axial movement of the boss by engaging with the projection. ing.

According to the ninth aspect of the present invention, the sliding surface on which the ring member slides is subjected to a heat treatment for hardening the surface, and the sliding of the boss and the fixing member on which the ring member slides. At least one of the moving surfaces is also subjected to a heat treatment for surface hardening.

In the electric power steering apparatus according to a tenth aspect of the present invention, the sliding surface on which the ring member slides is subjected to a heat treatment for hardening the surface, and the boss and the output shaft slide on which the ring member slides. At least one of the moving surfaces is also subjected to a heat treatment for surface hardening.

According to the eleventh aspect of the present invention, there is provided the electric power steering apparatus, wherein the grease interposed between the driven shaft and the boss spline-engaged with the driven shaft, the sliding surface of the ring member and the ring member are provided. The sliding boss and the grease interposed between the sliding surfaces of the fixed member are the same.

In the electric power steering apparatus according to a twelfth aspect of the present invention, grease interposed between the driven shaft and the boss spline-engaged with the driven shaft, the ring member, and the output with which the ring member slides are provided. The grease interposed between the shafts is the same.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below. The same or corresponding parts as those of the conventional example will be denoted by the same reference numerals. Embodiment 1 FIG. FIG. 1 is a sectional view of a main part of an electric power steering device according to Embodiment 1 of the present invention, FIG. 2 is an exploded view of the electric power steering device of FIG. 1, and FIG. 3 is an enlarged view of a portion A in FIG. This electric power steering device includes an electric motor (not shown) for transmitting an output to a driven shaft, and a torque limiter 10 for absorbing an excessive torque applied to the electric motor from the driven shaft. The torque limiter 10 includes a case 11 which is a fixed member fixed to the output shaft 3 of the electric motor;
A boss 12 is provided concentrically with the case 11 so as to be relatively rotatable and is spline-engaged with the driven shaft. The boss 12 is provided between the outer peripheral surface of the boss 12 and the inner wall surface of the case 11. Ring member 1 having elasticity in the radial direction
3 is provided. The ring member 13 has, for example, a trapezoidal cross section, and includes a protruding portion 14 that contacts an inner wall surface of the case 11;
And a foot 15 locked in a groove 16 formed along the circumferential direction of the boss 12.

Next, the operation of the electric power steering apparatus having the above configuration will be described. During normal operation, the steering assist torque generated from the electric motor is applied to the boss 12 and the case 11 by the elastic force acting in the radial direction of the ring member 13.
And the rotation torque of the output shaft 3 is
The power is transmitted to the boss 12 and the driven shaft via the ring member 13. When an excessive impact force acts on the electric motor side from the wheel side via the driven shaft during the normal operation described above, the slide member slides between the boss 12 in the torque limiter 10 and the case 11 via the ring member 13. Occurs, and the boss 12 rotates relatively to the case 4 and the output shaft 3 integrated with the case 4 to absorb an impact torque and prevent, for example, damage to the torque transmission mechanism.

The clearance between the boss 12 and the case 11 is, as shown in FIG.
By making the clearance smaller than the clearance t1 on the driven shaft side, concentric positioning of the case 11, the ring member 13, and the boss 12 can be easily performed during assembly. That is, the boss 12 is pressed into the hole 17 of the case 11 while the ring member 13 is locked in the groove 16 of the boss 12, but the clearance t2 on the press-fit side is small, so that it serves as a so-called guide. When the boss 12 is press-fitted into the hole 17 of the case 11, the boss 12 and the ring member 13 can be press-fitted with the axis of the case 11 coinciding with the axis.

Further, as shown in FIG.
Of the case 11 where the projection 14 of the
Groove 1 that engages with and prevents axial movement of boss 12
8 may be formed. As shown in FIG. 6, the step 19 of the groove 18 may be tapered to prevent the foot 15 of the ring member 13 from colliding with the step 19 and being damaged.

The ring member 13 is subjected to a heat treatment for surface hardening, and at least one of the boss 12 on which the ring member 13 slides and the sliding surface of the case 11 is surface-hardened by induction hardening or the like, so that wear resistance is improved. The characteristics may be improved. Also, grease (not shown) interposed between the driven shaft and the boss 12 that is spline-engaged with the driven shaft, the sliding surface of the ring member 13 and the boss 12 on which the ring member 13 slides, By making the grease interposed between the sliding surfaces 11 identical, it is possible to prevent the grease from changing its characteristics due to a chemical reaction even when both greases intersect.

Embodiment 2 FIG. FIG. 7 is a sectional view of a main part of an electric power steering apparatus according to Embodiment 2 of the present invention.
7 is an exploded view of the electric power steering device in FIG. 7, and FIG. 9 is an enlarged view of a portion B in FIG. This electric power steering device has an electric motor (not shown) for transmitting an output to a driven shaft.
And a torque limiter 20 for absorbing an excessive torque applied to the electric motor from the driven shaft. Torque limiter 2
Reference numeral 0 denotes a support portion 21 which is a fixed member fixed to the output shaft 3 of the electric motor, and is provided concentrically with the support portion 21 so as to be relatively rotatable and is spline-engaged with the driven shaft. A boss 22 and a ring member 13 provided between the inner peripheral surface of the boss 22 and the outer peripheral surface of the support portion 21 and having elasticity in a radial direction are provided.

As shown in FIG. 10, the clearance between the boss 22 and the support portion 21 is such that the clearance t1 on the driven shaft side with respect to the ring member 13 is opposite to the driven shaft side with respect to the ring member 13. , The concentric positioning of the support portion 21, the ring member 13, and the boss 22 during assembly can be easily performed. That is, the ring member 13 is provided in the groove 23 of the support 21.
The support portion 21 is press-fitted into the hole 24 of the boss 22 in a state where the lock is held, but since the clearance t1 on the press-fit side of the support portion 21 is small, it serves as a so-called guide, and the hole 24 of the boss 22 is formed. When press-fitting the support portion 21 into the inside, the support portion 21 and the ring member 13 can be press-fitted in a state in which the support portion 21 and the ring member 13 coincide with the axis of the boss 22.

Also in this embodiment, the first embodiment
Similarly to the above, a groove may be formed at the portion of the boss 22 where the projection 14 of the ring member 13 contacts, to engage the projection 14 and prevent the boss 22 from moving in the axial direction. Further, the step of the groove is tapered, and the ring member 13 is formed.
The foot 15 may be prevented from colliding with the step and being damaged.

The sliding surface of the ring member 13 is subjected to heat treatment, and at least one of the sliding surfaces of the boss 22 and the support portion 21 on which the ring member slides is subjected to, for example, induction hardening to harden the surface. Alternatively, the wear resistance may be improved. Further, by making the grease (not shown) used for the boss 22 of the driven shaft to be spline-engaged and the grease used for the ring member 13 identical to each other even when both greases intersect, the grease is chemically A change in characteristics due to a reaction may be prevented.

Embodiment 3 FIG. 11 is a sectional view of a main part of an electric power steering apparatus according to Embodiment 3 of the present invention, and FIG. 12 is an enlarged view of a portion E in FIG. In this embodiment, a torque limiter 30 includes a boss 31 that is spline-engaged with a driven shaft, and a radially elastic ring member provided between an inner wall surface of the boss 31 and the output shaft 3 of the electric motor. 13 is provided.

In this embodiment, as in the first and second embodiments, the clearance between the boss 31 on the driven shaft side and the output shaft 3 with respect to the ring member 13 and the ring member 13 Thus, the clearance between the boss 31 on the side opposite to the driven shaft and the output shaft 3 is made different, and concentric positioning of the output shaft 3, the ring member 13, and the boss 31 during assembly can be easily performed. You may do so. Further, a groove may be formed at a portion of the boss 31 where the projection 14 of the ring member 13 contacts, to engage with the projection 14 and prevent the boss 31 from moving in the axial direction. The sliding surface of the ring member 13 is subjected to a heat treatment, and at least one of the sliding surfaces of the boss 31 and the output shaft 3 on which the ring member slides is subjected to, for example, induction hardening to harden the sliding surface. Thus, the wear resistance may be improved. Also, by making the grease used for the boss 31 that is spline-engaged with the driven shaft and the grease used for the portion where the ring member 13 slides the same, even when both greases intersect, the grease is chemically A change in characteristics due to a reaction may be prevented.

Embodiment 4 FIG. 13 is a sectional view of a main part of an electric power steering apparatus according to Embodiment 4 of the present invention. FIG. 14 is an exploded view of the electric power steering apparatus of FIG.
FIG. 15 is an enlarged view of a portion C in FIG. The torque limiter 40 of the present embodiment differs from the torque limiter 10 of the first embodiment in that a round C-shaped ring 41 is provided between the boss 12 and the case 11. That is, the ring 41 serving as a blocking member is locked in the groove 42 of the boss 12 and the groove 43 of the case 11, and the ring 41 prevents the boss 12 from moving in the axial direction. Note that, for example, a ring may be used as the blocking member, or another member having the same function may be used.

Embodiment 5 FIG. 16 is a sectional view of a main part of an electric power steering device according to Embodiment 5 of the present invention. FIG. 17 is an exploded view of the electric power steering device of FIG.
FIG. 18 is an enlarged view of a portion D in FIG. The torque limiter 50 of this embodiment differs from the torque limiter 20 of the second embodiment in that a round C-shaped ring 51 is provided between the boss 22 and the support 21. That is, the ring 51 serving as a blocking member is locked in the groove 52 of the boss 22 and the groove 53 of the support 21, and the ring 51 prevents the boss 22 from moving in the axial direction.

[0031]

As described above, according to the electric power steering apparatus of the first aspect of the present invention, the torque limiter includes the fixing member fixed to the output shaft of the electric motor,
A boss, which is provided concentrically with respect to the fixing member and is rotatable relative thereto, and is engaged with the driven shaft; The ring member has both the function of braking the conventional friction plate and the function of elasticity of the spring member, so that the number of parts is reduced as compared with the conventional one. And the number of assembly steps can be reduced accordingly, and the manufacturing cost can be reduced.

Further, according to the electric power steering apparatus of the present invention, the torque limiter is provided between the boss engaged with the driven shaft and the inner wall surface of the boss and the output shaft of the electric motor. Since it is provided with a ring member provided in the radial direction, the number of parts can be reduced as compared with the conventional one, and the number of assembling steps can be reduced accordingly. Manufacturing costs are reduced.

Further, according to the electric power steering apparatus of the third aspect of the present invention, the clearance between the boss on the driven shaft side with respect to the ring member and the fixed member, and the non-driven state with respect to the ring member. Since the clearance between the boss on the shaft side and the fixing member is different, the boss, the ring member and the fixing member can be easily assembled concentrically.

According to the electric power steering apparatus of the fourth aspect of the present invention, the clearance between the boss on the driven shaft side with respect to the ring member and the output shaft, and the non-driven state with respect to the ring member. Since the clearance between the boss on the shaft side and the output shaft is different, the boss, the ring member, and the output shaft can be easily assembled concentrically during assembly.

According to the electric power steering apparatus of the fifth aspect of the present invention, since the blocking member for blocking the movement of the boss in the axial direction is provided between the boss and the fixing member, the boss can be moved in the axial direction of the boss. Movement can be reliably prevented.

According to the electric power steering apparatus of the sixth aspect of the present invention, since the blocking member for blocking movement of the boss in the axial direction is provided between the boss and the output shaft.
The movement of the boss in the axial direction can be reliably prevented.

According to the electric power steering apparatus according to the seventh aspect of the present invention, the portion of the fixing member where the projection of the ring member comes into contact is engaged with the projection to prevent the boss from moving in the axial direction. Since the groove is formed, the movement of the boss in the axial direction can be surely prevented without preparing the movement preventing member.

Further, according to the electric power steering device of the present invention, the boss is prevented from moving in the axial direction by engaging with the projecting portion at the boss where the projecting portion of the ring member contacts. Since the groove is formed, the movement of the boss in the axial direction can be surely prevented without preparing the movement preventing member.

According to the ninth aspect of the present invention, the sliding surface of the ring member is subjected to heat treatment, and at least the sliding surface of the boss and the fixed member on which the ring member slides. Since heat treatment is applied to one of the surfaces, the surface of each sliding surface is hardened, and the wear resistance is improved.

According to the electric power steering apparatus of the tenth aspect of the present invention, the sliding surface on which the ring member slides is subjected to heat treatment, and the boss and the output shaft slide, on which the ring member slides. Since heat treatment is performed on at least one of the surfaces, the surface of each sliding surface is hardened, and the wear resistance is improved.

According to the eleventh aspect of the present invention, there is provided the electric power steering apparatus, wherein the driven shaft and the grease interposed between the bosses spline-engaged with the driven shaft and the sliding surface of the ring member. Also, since the boss on which the ring member slides and the grease interposed between the sliding surfaces of the fixing member are the same, even when the two greases intersect, the grease does not change its properties due to a chemical reaction, and therefore has lubrication. sex,
Grease characteristics such as cooling performance can be secured for a long period of time.

In the electric power steering apparatus according to a twelfth aspect of the present invention, the grease interposed between the driven shaft and the boss spline-engaged with the driven shaft, the ring member and the ring member slide. The grease interposed between the output shafts is the same, so even when the two greases intersect, the characteristics of the grease do not change due to a chemical reaction, and therefore the characteristics of the grease such as lubricity and cooling properties are maintained over a long period of time. Can be secured.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an electric power steering apparatus according to Embodiment 1 of the present invention.

FIG. 2 is an exploded view of the electric power steering device of FIG.

FIG. 3 is an enlarged view of a portion A in FIG. 1;

FIG. 4 is an enlarged view of a main part showing a modification of the first embodiment.

FIG. 5 is an enlarged view of a main part showing another modification of the first embodiment.

FIG. 6 is an enlarged view of a main part showing still another modified example of the first embodiment.

FIG. 7 is a sectional view of a main part of an electric power steering device according to a second embodiment of the present invention.

8 is an exploded view of the electric power steering device of FIG.

FIG. 9 is an enlarged view of a portion B in FIG. 7;

FIG. 10 is an enlarged view of a main part showing a modification of the second embodiment.

FIG. 11 is a sectional view of a main part of an electric power steering apparatus according to Embodiment 3 of the present invention.

FIG. 12 is an enlarged view of a portion E in FIG. 11;

FIG. 13 is a sectional view of a main part of an electric power steering apparatus according to Embodiment 4 of the present invention.

FIG. 14 is an exploded view of the electric power steering device of FIG.

15 is an enlarged view of a portion C in FIG.

FIG. 16 is a sectional view of a main part of an electric power steering apparatus according to Embodiment 5 of the present invention.

17 is an exploded view of the electric power steering device of FIG.

FIG. 18 is an enlarged view of a part D in FIG. 16;

FIG. 19 is a sectional view of a main part of a conventional electric power steering device.

20 is an exploded view of the electric power steering device of FIG.

[Explanation of symbols]

3 output shaft, 10, 20, 30, 40, 50 torque limiter, 11 case (fixing member), 12, 22 boss, 13 ring member, 14 protrusion, 15 foot, 1
6, 18, 23, 42, 43, 52, 53 Grooves, 1
7, 24 holes, 19 steps, 21 support (fixing member), 41, 51 ring (blocking member).

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshinori Tanaka 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 3D033 CA05 5H607 AA11 CC03 DD17 EE03 JJ10

Claims (12)

[Claims] 1. An electric power steering apparatus comprising: an electric motor for transmitting an output to a driven shaft; and a torque limiter for absorbing an excessive torque applied to the electric motor from the driven shaft. A fixing member fixed to the output shaft, a boss provided concentrically with respect to the fixing member and rotatable relative thereto and engaged with the driven shaft, and a side surface of the boss and the fixing member An electric power steering device comprising: a ring member provided between the side surface and a ring member having elasticity in a radial direction. 2. An electric power steering apparatus comprising: an electric motor for transmitting an output to a driven shaft; and a torque limiter for absorbing an excessive torque applied to the electric motor from the driven shaft. An electric power steering apparatus comprising: a boss engaged with a shaft; and a ring member provided between an inner wall surface of the boss and an output shaft of the electric motor and having elasticity in a radial direction. 3. The clearance between the boss on the driven shaft side and the fixed member with respect to the ring member and the clearance between the boss on the driven shaft side opposite to the ring member and the fixed member with respect to the ring member are different. The electric power steering device according to claim 1. 4. A clearance between a boss on the driven shaft side and the output shaft with respect to the ring member and a clearance between the boss on the driven shaft side opposite to the ring member and the output shaft with respect to the ring member. The electric power steering device according to claim 1. 5. The electric power steering device according to claim 1, further comprising a blocking member provided between the boss and the fixing member, the blocking member blocking movement of the boss in the axial direction. 6. The electric power steering apparatus according to claim 2, further comprising a blocking member provided between the boss and the output shaft for preventing movement of the boss in the axial direction. 7. A groove formed in a portion of the fixing member where the protrusion of the ring member abuts to prevent the boss from moving in the axial direction by engaging with the protrusion. The electric power steering device according to claim 5. 8. The boss at which the projection of the ring member abuts is formed with a groove that engages with the projection to prevent the boss from moving in the axial direction. The electric power steering device according to claim 1. 9. A sliding surface on which the ring member slides is subjected to a heat treatment for hardening the surface, and the ring member slides.
8. The electric power steering device according to claim 1, wherein at least one of the sliding surfaces of the boss and the fixed member is subjected to a heat treatment for surface hardening. 10. A heat treatment for surface hardening is performed on a sliding surface on which the ring member slides, and a heat treatment for surface hardening on at least one of the boss and the output shaft sliding surface on which the ring member slides. Claim 2, Claim 4,
An electric power steering apparatus according to claim 6. 11. A grease interposed between a driven shaft and a boss that is spline-engaged with the driven shaft, a sliding surface of the ring member, a boss on which the ring member slides, and a sliding surface of the fixed member. 10. The electric power steering device according to claim 1, wherein the grease interposed therebetween is the same. 12. The grease interposed between a driven shaft and a boss spline-engaged with the driven shaft is the same as the grease interposed between a ring member and an output shaft on which the ring member slides. The electric power steering device according to any one of claims 2, 4, 6, 6, and 10.