JP2004114865A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce tooth hitting sound between gears by proper adjustment of backlash. <P>SOLUTION: This electric power steering device 1 straight movably supports a rack shaft 3 connected to a large bevel gear 8 inside a housing 5. On the housing 5, a holder part 5a is protruded from a part covering the large bevel gear 8, and a motor housing 10 to hold an electric motor 4 having a small bevel ear 9 connected to an output shaft 4a is engaged in an opening 5d formed in an end surface of the holder part 5a to be movable in a direction X. In the holder part 5a, a screw body 11 is engaged, and a lock part 11a provided at an end part of the screw body 11 is locked to a lock groove 10g of the motor housing 10. By rotation of the screw body 11, the motor housing 10 is moved to adjust backlash between the gears, and an adjusted position is held by tightening a lock nut 12 engaged with the screw body 11. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric power steering device, and more particularly to adjusting a backlash between a large gear included in a steering shaft or a transmission shaft of a steering force such as a steering shaft and a small gear connected to an electric motor for assisting steering. Thus, the rattling noise (rattle noise) is reduced.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is an electric power steering device that assists steering by using a torque generated by an electric motor as a vehicle steering device. In such an electric power steering device, a motor housing holding an electric motor is attached to an opening formed in a housing supporting a transmission shaft of steering force, and a small gear on the electric motor side is attached to a large gear on the transmission shaft side. The gears are engaged to transmit the driving force of the electric motor to the transmission shaft.
[0003]
A steering shaft such as a steering shaft or a rack shaft connected to the steering wheel corresponds to the transmission shaft, and the steering shaft or the steering shaft is assisted by an electric motor. Further, the output shaft of the electric motor is arranged in a parallel, orthogonal or oblique positional relationship with the steering shaft or the steering shaft according to the transmission form of the driving force. A gear of a type corresponding to the positional relationship between the two shafts is applied.
[0004]
The required backlash is necessary to rotate the large gear and small gear smoothly, but if the amount of backlash is not appropriate, excessive rattle noise occurs between the gears. Adjustment is required. The backlash is adjusted by, for example, interposing a shim between the housing and the motor housing, and the required amount of backlash is secured by appropriately changing the number of shims, the thickness of the shim, and the like. Further, a configuration in which a backlash is adjusted by screwing a bearing holder and a motor housing so as to be movable in the output shaft direction is also disclosed (see Patent Document 1).
[0005]
[Patent Document 1]
Japanese Patent No. 2952942 [0006]
[Problems to be solved by the invention]
The conventional backlash adjustment may not be sufficient depending on the positional relationship between the two shafts on which the large gear and the small gear are respectively mounted. For example, when the output shaft obliquely intersects the steering shaft or steering shaft, the intervention of the shim alone stops the adjustment in the output shaft direction, cannot cope with the direction of adjusting the distance between the shafts, and causes the required backlash. It was difficult to adjust the amount. For this reason, there is a problem that the rattle noise between gears cannot be reduced to a required level. Also, the configuration described in Patent Literature 1 described above also only adjusts in the output shaft direction, so that it may be difficult to appropriately adjust backlash.
[0007]
SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and allows a motor housing to move in a direction approaching or moving away from a transmission shaft of a steering force, thereby expanding a degree of backlash adjustment and gearing. An object of the present invention is to provide an electric power steering device capable of reliably reducing noise.
[0008]
[Means for Solving the Problems]
An electric power steering device according to a first aspect of the present invention provides a power transmission steering device, in which an output shaft is provided with a small gear meshing with the large gear in an opening formed in a housing that internally supports a transmission shaft for transmitting a steering force to which the large gear is connected. In the electric power steering device, in which a motor housing for holding a connected steering assist electric motor is fitted to assist the steering force by driving the electric motor, the opening is provided in the axial direction of the output shaft. A dimension in a direction substantially orthogonal to and parallel to a direction in which the output shaft and the transmission shaft are opposed to each other is larger than an outer dimension of the motor housing, and the housing moves the motor housing close to and away from the transmission shaft. And moving means for moving in the parallel direction.
[0009]
According to the first invention, the opening of the housing is formed in a size that allows the fitted motor housing to move, and the housing includes a moving means for moving the motor housing. Moves, and the backlash can be adjusted in a direction different from the adjustment direction by the conventional shim. Therefore, it is possible to adjust the backlash even in a direction that could not be adjusted conventionally. As a result, an appropriate backlash can be ensured, and the rattle between gears can be reliably reduced.
[0010]
As the moving means, a screw body which is screwed into the housing and one end of which is rotatably connected to the motor housing can be applied. By finely adjusting the position of the motor housing by rotating the screw body clockwise or counterclockwise by matching the axial direction of the screw body screwed in this way with the direction in which the motor housing is moved. it can.
[0011]
An electric power steering apparatus according to a second aspect of the present invention is characterized in that the housing further includes position holding means for holding a position where the moving means has moved the motor housing.
[0012]
In the second invention, the position of the motor housing properly adjusted by the moving means is held by the position holding means, so that the once adjusted position can be prevented from shifting until the motor housing is fully fixed to the housing. Thus, the assemblability of the motor housing and the housing can be improved. When the above-mentioned screw body is applied to the moving means, a lock nut which is screwed to the screw body and fixes the screw body to the housing can be used as the position holding means.
[0013]
An electric power steering device according to a third aspect of the present invention is configured such that the opening has an inner surface formed along the parallel direction, and the motor housing has a sliding surface that is in contact with the inner surface. Features.
[0014]
According to the third aspect, the sliding surface of the motor housing abuts on the inner surface of the opening. Therefore, when the motor housing is moved by the moving means, the motor housing can be smoothly moved along the inner surface, and the backlash Fine adjustment of can be performed more easily. In addition, by providing parallel inner surfaces to the openings so as to face each other, and by providing a sliding surface in the motor housing so as to abut each inner surface, the motor housing is twisted in a direction in which the motor housing approaches and separates from the transmission shaft. In addition, it is possible to restrict movement so that the movement does not occur, and a more stable movement form can be secured.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings showing the embodiments.
FIG. 1 shows an overall configuration of an electric power steering device 1 according to an embodiment of the present invention. The electric power steering device 1 according to the present embodiment controls the electric motor 4 for steering assistance held by the motor housing 10 to move the rack shaft 3 corresponding to the transmission shaft for transmitting the steering force of the steering wheel 2 in the axial direction. Is used to assist driving.
[0016]
The rack shaft 3 is supported inside the housing 5 so as to be movable in the left-right direction in the drawing, which is the axial direction, and a rack portion 3a is formed on the right side in the drawing. The rack portion 3a meshes with a pinion (not shown) attached to an end of a steering shaft 6 connected to the steering wheel 2, and when the steering wheel 2 is steered, the steering shaft 6 and the pinion are steered. , And the rotation of the pinion is transmitted through the rack portion 3a to move the rack shaft 3 leftward or rightward.
[0017]
A feed screw mechanism is provided on the left side of the rack shaft 3. The feed screw mechanism has a configuration in which a ball nut 7 is rotatably fitted to a screw groove 3b formed in the rack shaft 3 itself. The ball nut 7 has a number of balls screwed into the screw groove 3b therein, and transmits the rotation of the ball nut 7 to the screw groove 3b through the ball to move the rack shaft 3 leftward or rightward.
[0018]
A large bevel gear 8 is attached to the outer periphery of the ball nut 7 as a large gear connected to the rack shaft 3. The large bevel gear 8 is connected to a small bevel gear 9 (small gear) connected to the output shaft 4 a of the electric motor 4. Are engaged. The driving of the electric motor 4 is controlled by a control device (not shown) according to the rotation state of the steering shaft 6, and the electric motor 4 transmits its own driving force to the rack shaft 3 via the small bevel gear 9 and the large bevel gear 8. The steering force applied to the wheel 2 is assisted.
[0019]
The housing 5 that covers the rack shaft 3 forms a holder portion 5a that projects obliquely near the position where the large bevel gear 8 is located. As shown in FIG. 2, the holder 5a has a flange 5b formed at the end on the protruding side, and an opening 5d communicating with the internal cavity 5c is formed at the end face of the flange 5b.
[0020]
As shown in FIG. 4, the opening 5d has, for example, a rectangular shape, continues to the back of the housing 5 as it is, and is orthogonal to the axial direction of the output shaft 4a, and the output shaft 4a and the rack shaft 3 face each other. The dimension L1 (same for L1 in FIG. 2) in the direction X (similar to X in FIG. 1) is larger than the outer diameter L2 corresponding to the direction X of the motor housing 10. . Two inner surfaces 5f and 5g are formed in the inner peripheral surface of the opening 5d in parallel with the direction X, and each of the inner surfaces 5f and 5g is a flat surface having a small surface roughness.
[0021]
The holder portion 5a has a threaded hole 5i that penetrates the cavity portion 5c from the outside and is formed parallel to the direction X on one peripheral wall 5h orthogonal to the direction X (see also FIG. 2). The holder portion 5a has two fixing screw holes 5e for fixing the motor housing 10 around the flange portion 5b.
[0022]
As shown in FIG. 2, a screw body 11, which is a moving means of the motor housing 10, is screwed into the screw hole 5i of the holder 5a. In the screw body 11, a disk-shaped locking portion 11b is connected to one end of a screw shaft portion 11a in which a screw portion matching the pitch of the screw hole 5i is formed.
[0023]
Further, a lock nut 12 corresponding to a position holding means for holding the position of the screw body 11 is screwed into the screw shaft portion 11a of the screw body 11 screwed into the screw hole 5i, as shown in FIG. Then, the position of the screw body 11 is maintained by being fixedly fastened to the peripheral wall 5h of the holder 5a. Therefore, until the lock nut 12 is tightened, the position of the locking portion 11b can be moved with respect to the peripheral wall 5h by rotating the screw body 11 screwed into the screw hole 5i clockwise or counterclockwise. After the lock portion 11b is adjusted to the required position, the lock nut 12 is tightened to the peripheral wall 5h, so that the lock portion 11b can be held at the adjusted position.
[0024]
On the other hand, as shown in FIGS. 1 and 3, the motor housing 10 for holding the electric motor 4 has a square pillar-shaped shaft holding portion 10a in which bearings 15 and 16 for rotatably supporting the output shaft 4a are fitted. It is formed in a shape in which a rectangular motor flange portion 10b is integrated with an end.
[0025]
The shaft holding portion 10a has an outer shape that can fit into the opening 5d of the holder portion 5a of the housing 5, and as described above, the outer size L2 in the direction X in FIG. 4 is smaller than the size L1 of the opening 5d. The width L3 in the width direction in FIG. 3 is substantially equal to the inner width in the direction orthogonal to the direction X of the opening 5d in FIG. 4, and the two dimensions are set to a so-called loose fit. .
[0026]
Further, when the shaft holding portion 10a is fitted into the opening 5d, the outer surfaces 10c and 10d that come into contact with the inner surfaces 5f and 5g of the opening 5d are smooth sliding surfaces. By forming the shaft holding portion 10a in this way, the shaft holding portion 10a can be smoothly moved in the direction X in FIG. 4 in a state of being fitted in the opening 5d.
[0027]
Further, as shown in FIG. 3, the shaft holding portion 10a has a hole 10f on the tip end surface 10e opposite to the motor flange portion 10b for projecting the output shaft 4a outwardly. A locking groove 10g having a substantially convex cross section is formed continuously upward from the distal end face 10e in the longitudinal direction.
[0028]
The horizontal portion 10h of the locking groove 10g has a size in which the locking portion 11b of the screw body 11 fits, and the vertical portion 10i of the locking groove 10g has a size in which the screw shaft portion 11a of the screw body 11 fits. The vertical portion 10i of the locking groove 10g communicates with one outer surface 10j of the peripheral wall of the shaft holding portion 10a so that the screw body 11 fitted in the locking groove 10g can be moved along the locking groove 10g. The motor flange 10b of the motor housing 10 has elongated holes 10k at positions corresponding to the two fixing screw holes 5e provided on the flange 5b of the holder 5a.
[0029]
Next, the motor housing 10 holding the electric motor 4 in which the small bevel gear 9 is connected to the output shaft 4a is fitted into the opening 5d of the holder 5a to which the screw body 11 is attached, and the small bevel gear 9 is connected to the large bevel gear 8. The procedure for engaging and adjusting the backlash will be described with reference to FIG.
[0030]
First, when the motor housing 10 is fitted into the opening 5d, the vicinity of the connection between the locking portion 11b of the screw body 11 and the screw shaft portion 11a is fitted into the locking groove 10g from the distal end surface 10e, and the small bevel gear 9 and the large The bevel gear 8 is fitted until it meshes. In this state, the meshing state of the small bevel gear 9 and the large bevel gear 8 is confirmed.
[0031]
When the motor housing 10 is moved backward from the rack shaft 3 in the axial direction of the output shaft 4a in order to adjust the backlash between the two gears by checking the meshing state, the flange 5b of the holder 5a and the motor housing 10 are The required number of shims 13 are sandwiched between the motor shim 13b and the motor flange 10b. When the motor housing 10 is moved toward and away from the rack shaft 3 in the direction X, the screw body 11 is rotated clockwise or counterclockwise with the lock nut 12 loosened.
[0032]
Such an adjustment for moving the motor housing 10 in the direction X can be performed only by rotating the screw body 11, so that it is very easy, and the motor housing 10 can be finely moved according to the degree of rotation of the screw body 11. As a result, the backlash can be adjusted so as to reduce the rattling noise. Also, since the motor housing 10 has the outer surfaces 10c and 10d, which are the left and right sliding surfaces, abutting against the inner surfaces 5f and 5g of the opening 5d, the moving direction is regulated so that twisting and twisting do not occur, and the motor housing 10 moves smoothly. Has contributed to the security.
[0033]
After such an adjustment is performed to make a backlash state in which no rattling noise occurs, the position of the adjusted motor housing 10 is maintained by tightening the lock nut 12. Thereafter, the fixing bolt 14 inserted from the long hole 10k of the motor housing 10 is screwed into the fixing screw hole 5e, and the motor housing 10 is fixed to the holder portion 5a of the housing 5, and the mounting of the electric motor 4 is completed. I have.
[0034]
The electric power steering device 1 having the backlash adjusting structure according to the present invention is not limited to the above-described embodiment. For example, in the above embodiment, the large bevel gear 8 is connected to the rack shaft 3 with the ball nut 7 interposed. However, when the rotation of the steering shaft to which the steering wheel is connected is assisted by an electric motor, the large bevel gear 8 is connected to the steering shaft. The present invention is also applicable to fixing the large bevel gear and adjusting the backlash with the large bevel gear fixed in this way.
[0035]
The present invention is also applicable to an arrangement in which an output shaft of an electric motor and a steering shaft or a steering shaft are parallel and orthogonal. Further, the present invention is applied to a case where a hypoid gear, a spur gear, a helical gear, a helical gear, a worm and a worm wheel, and the like are used for the large gear and the small gear according to the positional relationship between the two shafts. This makes it possible to finely adjust the backlash, thereby reliably reducing rattling noise.
[0036]
【The invention's effect】
As described in detail above, in the first invention, fine adjustment of the backlash can be easily performed, and the rattling noise between the gears can be reliably reduced.
According to the second aspect, the adjusted position can be held, so that the adjusted position can be prevented from being shifted by the time of final fixing, and the assembling property can be improved.
According to the third aspect, smooth movement of the motor housing can be realized, and backlash can be more easily adjusted.
[Brief description of the drawings]
FIG. 1 is an overall schematic diagram of an electric power steering device according to an embodiment of the present invention.
FIG. 2 is a schematic partial cross-sectional view of a holder portion of a housing.
FIG. 3 is a perspective view of a motor housing and a screw body.
FIG. 4 is a sectional view taken along line AA of FIG. 1;
[Explanation of symbols]
1 electric power steering device 3 rack shaft (transmission shaft)
4 Electric motor 4a Output shaft 5 Housing 5a Holder 5d Opening 5g, 5f Inner surface 8 Large bevel gear (large gear)
9 Small bevel gear (small gear)
10 Motor housing 10c, 10d Outer surface (sliding surface)
10g Locking groove 11 Screw body (moving means)
11a Screw shaft portion 11b Locking portion 12 Lock nut (position holding means)
X direction

Claims (3)

An electric motor for steering assistance in which a small gear meshing with the large gear is connected to an output shaft is formed in an opening formed in a housing that internally supports a transmission shaft for transmitting a steering force to which the large gear is connected. In an electric power steering device, in which a motor housing to be held is fitted and a steering force is assisted by driving the electric motor,
The opening is
The dimension in a direction substantially orthogonal to the axis length direction of the output shaft and parallel to the direction in which the output shaft and the transmission shaft face each other is larger than the outer dimensions of the motor housing,
The housing is
An electric power steering apparatus, comprising: moving means for moving the motor housing in the parallel direction so as to approach and separate from the transmission shaft. The housing further comprises:
The electric power steering apparatus according to claim 1, further comprising a position holding unit that holds a position where the moving unit has moved the motor housing. The electric power steering according to claim 1 or 2, wherein the opening has an inner surface formed along the parallel direction, and the motor housing has a sliding surface that is in contact with the inner surface. apparatus.

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