JP2816408B2 - Power steering device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an electric power steering apparatus using an electric motor as a source of a steering assist force, and more specifically, from an electric motor to a steering mechanism. The present invention relates to a power steering device provided with a clutch in the middle of a transmission system.

[Conventional technology]

2. Description of the Related Art In recent years, an electric power steering apparatus using an electric motor as a source of a steering assist force has been put to practical use. This is because the steering assist motor arranged in the middle of the steering mechanism is driven based on the detection result of the steering torque, and the operation of the steering mechanism is assisted by the rotational force of the motor, so that steering is performed. It is intended to reduce the labor burden required for steering operation of the vehicle.

When compared with a hydraulic power steering device that uses a hydraulic actuator as a source of steering assist force, the electric power steering device can easily change the characteristics by controlling the rotation of the motor. It has the advantage of being able to realize appropriate characteristics corresponding to the driving conditions, such as the level of steering and the frequency of steering, but can generate sufficient rotational force for steering assistance, and it is difficult to obtain a small motor. thing,
There are difficulties such as that the inertia of the rotating part of the motor affects the steering operation. Therefore, conventionally, an appropriate reduction gear has been arranged between the output shaft of the motor and the transmission shaft to the steering mechanism, and the former difficulty has been solved by the boosting action of the reduction gear. An electromagnetic clutch is arranged between the output shaft and the transmission shaft connected to the steering mechanism, and the operation of the electromagnetic clutch causes the two shafts to be engaged only when necessary, thereby solving the latter difficulty. . The electromagnetic clutch is arranged on a friction plate that rotates in conjunction with each of the output shaft and the transmission shaft, a drive coil fixed to the back of the friction plate on the output shaft side, and a back of the friction plate on the transmission shaft side. The armature part is operated by the excitation of the drive coil, and the friction plates are pressed against each other to engage the two shafts, while the operation of the armature part caused by the demagnetization of the drive coil is performed by the operation of the armature part. This is to release the pressing to interrupt the engagement between the two shafts. Conventionally, the output shaft formed by coaxially fitting one friction plate and its holding body and the other friction plate are integrated. The power transmission shaft formed by coaxially fitting the armature portion thus mounted is separately supported coaxially, and the respective mounting-side ends are abutted with an appropriate gap therebetween. As the reduction gear, a planetary gear reduction gear or a planetary roller reduction gear is used because it can be configured coaxially with an output shaft of a motor and a transmission shaft to a steering mechanism, and can be easily miniaturized. Are arranged side by side on one side of the electromagnetic clutch.

[Problems to be solved by the invention]

However, in the conventional power steering apparatus configured as described above, in order to secure a predetermined initial gap between the friction plates of the electromagnetic clutch, the support portions of both shafts, and both shafts and the holding body or the armature are required. Very high precision processing is required for the fitting part with the part. Also, since the armature and the holder are in a cantilevered support state, the tilting of the friction plates held by them is unavoidable, and to ensure a uniform initial gap in the circumferential direction between both friction plates, There is a problem that a complicated gap adjustment operation is required and a large amount of time is required for assembly. Furthermore, even if sufficient attention is paid to machining and assembly, it is quite difficult to completely prevent the initial gap from being set incorrectly.If the initial gap is too large, slippage occurs between the friction plates during engagement. And transmission to the steering mechanism is obstructed,
Conversely, if the initial gap is too small, there is an inconvenience in operation, such as generation of an unpleasant noise due to sliding contact between the friction plates at the time of interruption.

In the case where the above-described speed reducer is configured between the output shaft of the motor and the transmission shaft to the steering mechanism, a lubricant (grease) applied to a rolling portion of the speed reducer when the speed reducer operates. Has scattered to the electromagnetic clutch side, adhered to both friction plates of the electromagnetic clutch, and the engaging operation of the electromagnetic clutch performed by pressing both friction plates has been disadvantageously hindered.

The present invention has been made in view of such circumstances, and eliminates the inconvenience in processing and assembling an electromagnetic clutch configured between a steering assist motor and a transmission shaft to a steering mechanism. A predetermined initial gap can be reliably realized between the friction plates of the electromagnetic clutch, and the scattering of the lubricant from the speed reducer formed between the motor and the transmission shaft to the electromagnetic clutch can be effectively prevented. An object of the present invention is to provide a power steering device that does not hinder the engagement operation of a clutch.

[Means for solving the problem]

A power steering device according to the present invention is configured to excite and demagnetize a drive coil between an output shaft of a steering assist motor driven based on a detection result of a steering torque and a transmission shaft to a steering mechanism. In a power steering apparatus provided with an electromagnetic clutch for engaging the two shafts by the operation of the accompanying armature portion, an intermediate transmission shaft supported at both ends between the output shaft and the transmission shaft to support the armature portion, A biasing means for biasing the intermediate transmission shaft in the axial direction and pressing the support portion on the output shaft side is provided, further comprising a reduction device configured on the intermediate transmission shaft and Between the electromagnetic clutch,
It is characterized in that it comprises a shielding member for shielding both of them while leaving the penetrating portion of the intermediate transmission shaft.

[Action]

In the present invention, an intermediate transmission shaft that is supported at both ends is provided between the output shaft and the transmission shaft, and the armature portion is supported on the shaft to prevent the armature portion from tilting. The urging means presses against the output shaft side, restrains movement in the axial direction generated between the output shaft and the intermediate transmission shaft and the armature portion supported by the output shaft, and is attached to the output shaft and the armature portion, respectively. A substantially uniform predetermined initial gap is realized in the circumferential direction between the friction plates. In addition, a reduction gear for reducing the rotation of the output shaft and transmitting the rotation to the transmission shaft is formed on the intermediate transmission shaft, and a shielding member is provided between the reduction gear and the electromagnetic clutch to scatter from the reduction gear. The shielding member reliably prevents the lubricant from reaching the electromagnetic clutch, and eliminates the malfunction of the electromagnetic clutch due to the adhesion of the lubricant.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings showing the embodiments. FIG. 1 is a longitudinal sectional view showing a main part of a power steering apparatus according to the present invention.

In the drawing, reference numeral 1 denotes an upper shaft, and 2 denotes a lower shaft, which are coaxially connected via a torsion bar 3 and rotatably supported in a common housing 4 having a cylindrical shape. is there. The upper end of the upper shaft 1 is connected to a steering wheel (not shown), and the lower shaft 2 engages a pinion 2a formed on the outer periphery near the lower end with a rack shaft 5 intersecting the pinion 2a as shown in the figure. A rack-and-pinion type steering mechanism is provided in which steering is performed according to sliding of the rack shaft 5 in the axial direction. Therefore, when an operating torque is applied to the steering wheel, the upper shaft 1 tries to rotate accordingly,
Since the rotation of the lower shaft 2 is restricted by the resistance applied to the steering mechanism, the torsion bar 3 is twisted corresponding to the magnitude and direction of the operation torque, and the upper shaft 1 and the lower shaft 2 are rotated.
A relative angular displacement corresponding to this torsion is generated at the connection portion with the.
In the figure, reference numeral 6 denotes a torque sensor provided at a connecting portion between the upper shaft 1 and the lower shaft 2 in order to detect a steering torque applied to the steering wheel as the relative angular displacement generated therewith.

A large bevel gear 7a is fitted on the outer periphery of the middle part of the lower shaft 2 with the tooth surface facing upward. In the vicinity of the fitted position, a fixed housing 40 having a cylindrical shape is outwardly mounted on the housing 4. It has been extended to. At the open end of the fixed housing 40, a motor 11, which is a source of the steering assist force, an electromagnetic clutch 12 for engaging and disengaging the output of the motor 11, and a planetary gear reduction device 13 for increasing the output of the motor 11 are concentrically mounted. An auxiliary force generating unit 10 arranged side by side is fitted. The auxiliary force generator
The transmission shaft 14, which is the output shaft of 10, extends into the housing 4 through the inside of the fixed housing 40, and the small bevel gear 7b fitted to the extended end meshes with the large bevel gear 7a. is there.
Thereby, the output of the motor 11 is taken out to the transmission shaft 14 via the electromagnetic clutch 12 and the planetary gear reduction device 13, and then transmitted to the lower shaft 2 via the small bevel gear 7b and the large bevel gear 7a meshing therewith. Further, the engagement between the pinion 2a and the rack shaft 5 is converted into sliding in the axial direction of the rack shaft 5 to perform steering. The motor 11 is driven based on the detection result of the steering torque by the torque sensor 6, and generates a force corresponding to the magnitude of the steering torque in the direction of the steering torque applied to the steering wheel. Is transmitted to the rack shaft 5 as described above, and the force required for steering operation for steering is assisted by the generated force of the motor 11.

In the housing 4, a thin, shallow cup-shaped shielding member 8 is mounted as shown in the figure so as to separate the meshing portion of the bevel gears 7a, 7b from the torque sensor 6. . The shielding member 8 prevents the grease for lubrication sealed in the meshing portion of the bevel gears 7a and 7b from scattering and maintains a good lubricating state in the meshing portion, and at the same time, to the components of the torque sensor 6 of the grease. And prevents the steering torque from being erroneously detected due to the adhesion of the grease.

Now, the power steering apparatus according to the present invention is characterized by the internal configuration of the auxiliary force generation unit 10. Figure 2 shows the auxiliary force generator
It is an expanded sectional view of 10.

In the figure, reference numeral 10a denotes a housing that surrounds the entire assisting force generating unit 10, and the output shaft 11a of the steering assist motor 11 and the transmission shaft 14 that is connected to the steering mechanism as described above have their respective ends in the axial direction. At a predetermined distance from the housing 10
a is coaxially supported in the transmission shaft 14a from the output shaft 11a.
The transmission system includes an electromagnetic clutch 12 arranged on the motor 11 side (right side in the figure) and a planetary gear reduction device 13 arranged on the transmission shaft 14 side (left side in the figure) between the two shafts 11a and 14. Consists of

The output shaft 11a of the motor 11 is provided with a thick disk-shaped holding member 20, which forms a part of the electromagnetic clutch 12, as will be described later.
A thick disk-shaped carrier 30 which forms a part of the planetary gear reduction device 13 is spline-coupled to each other coaxially with each other as described later. The holding body 20 and the carrier 30 each have a circular hole with a predetermined depth at the axial center position on the side facing each other, and a ball bearing 20a is internally fitted and fixed in the circular hole of the holding body 20. A ball bearing 30a is fitted in the circular hole so as to be slidable in the axial direction. Intermediate transmission shaft that is a feature of the present invention
15 has both ends supported by the ball bearings 20a, 30a, and is supported at both ends between the output shaft 11a and the transmission shaft 14. The inside of the circular hole formed in the carrier 30 has a wave washer 16 serving as urging means in a state in which both ends are in contact with the end face of the transmission shaft 14 facing the circular hole and the outer ring of the ball bearing 30a. The intermediate transmission shaft 15 is urged toward the output shaft 11a by the wave washer 16 via a ball bearing 30a.

On the outer periphery of the intermediate transmission shaft 15 on the transmission shaft 14 side, a sun gear 31 of the planetary gear reduction device 13 is formed, and the output shaft 11a
The armature portion 22 of the electromagnetic clutch 12 is fitted on the outer periphery on the side. The armature portion 22 has a cylindrical boss portion 22a externally fitted to the intermediate transmission shaft 15, a thin movable plate 22 having one end fixed to the boss portion 22a and extending radially outward.
b, and a friction plate 22c fixed to the surface of the movable plate 22b on the output shaft 11a side. The boss portion 22a is provided with the sun gear 31.
Both ends are sandwiched between the shoulder surface in the forming portion and the inner ring of the ball bearing 20a, and are pressed against the inner ring surface of the ball bearing 20a by the urging force of the wave washer 16 acting through the contact portion with the shoulder surface. ing.

A drive coil 21 is fixedly fitted in the housing 10a at a position substantially aligned with the tip of the output shaft 11a of the motor 11 in the axial direction, and the drive coil 21 is a motor of the holder 20.
It is arranged in a recess formed over the entire circumference on the surface on the 11 side, and faces the bottom of the recess with a small gap. Further, a friction plate 20c is fixed to the other surface of the holding body 20, which is radially aligned with the friction plate 22c of the armature portion 22,
They face each other with a predetermined gap in the axial direction.

The electromagnetic clutch 12 includes a holding body 20 configured as described above,
When the drive coil 21 is demagnetized, only the holder 20 is connected to the output shaft 11a.
When the driving coil 21 is excited, the friction plate 22c of the armature portion 22 is moved together with the movable plate 22b by the action of a magnetic field formed near the armature portion 22 via the holding member 20. Attracted to the side and both friction plates 2
The output of the output shaft 11a is transmitted to the intermediate transmission shaft 15 via the holding body 20 and the armature section 22.

On the other hand, the planetary gear reduction device 13 is a ring gear having a sun gear 31 formed on the outer periphery of the intermediate transmission shaft 15 and a housing 10a which is internally fitted and fixed through a fixed ring 10b lined with a rubber material, and having a tooth surface inside. 33, and a plurality of planetary gears 32, 32,... Pivotally supported by the carrier 30. The sun gear 31 and the ring gear 33 are substantially aligned in the axial direction,
The planetary gears 32, 32 ... are the sun gear 31 and the ring gear 33
In the annular space formed between the two gears 31, 32
Each is meshed. The planetary gears 32, 32 ... revolve with the carrier 30 which rotates in conjunction with the transmission shaft 14, and rotate around respective pivot shafts parallel to the revolving shaft. The torque transmitted to 15 is transmitted through planetary gears 32, 3 via sun gear 31.
Are output to these revolving shafts, that is, the transmission shaft 14 with a predetermined deceleration, and transmitted to the steering mechanism as described above.

Now, in order to reliably perform the above-described engagement by the electromagnetic clutch 12, the gap (initial gap) between the friction plates 20c and 22c before sliding contact is appropriately maintained over the entire circumferential direction. This is very important. In the power steering device according to the present invention, as described above, the armature portion 22 is fitted to the intermediate transmission shaft 15 supported at both ends between the output shaft 11a and the transmission shaft 14, and the output shaft 11a The inclination of the armature portion 22 with respect to the fixed holding body 20 is slight, and the uniformity of the initial gap in the circumferential direction can be maintained extremely well without requiring a complicated adjustment operation at the time of assembly. The intermediate transmission shaft 15 that supports the armature part 22 has a wave washer.
The armature portion 22 and its friction plate 22c are urged toward the output shaft 11a by the urging force of 16, and the sun gear of the intermediate transmission shaft 15 is moved relative to the holder 20 and the friction plate 20c fixed thereto. Both end surfaces of the boss portion 22a are sandwiched and positioned between the shoulder surface at the formation portion 31 and the inner ring of the ball bearing 20a. Therefore, the size of the initial gap can be easily adjusted without the need for adjustment work at the time of assembly by increasing the processing accuracy of the holding plate 20 and the armature portion 22.
That is, in the power steering apparatus according to the present invention, when assembling the electromagnetic clutch 12, there is no need to perform complicated adjustment work of the initial gap between the friction plates 20a and 22a, and a reliable engagement operation is guaranteed.

Further, the planetary gear reduction device 13 is filled with grease to perform a lubricating action at a meshing portion between the sun gear 31 and the ring gear 33 and the planetary gears 32, 32, and the grease is scattered toward the electromagnetic clutch 12 to cause friction. Board 20c, 22
When it adheres to the sliding surface of c, the engagement operation by the electromagnetic clutch 12 is hindered. In the power steering device according to the present invention, the shielding member 9 is provided between the planetary gear reduction device 13 and the electromagnetic clutch 12 to prevent the scattered grease from entering the components of the electromagnetic clutch 12. Shielding member 9 shown in FIG.
Is a thin disk-shaped member sandwiched and fixed between one side end surface of the fixed ring 10b and the inner shoulder surface of the housing 10a. The inner peripheral edge of the shielding member 9 is fitted around the intermediate transmission shaft 15 outside. The boss 22a is opposed to the outer periphery of the boss 22a with a slight gap. That is, the components of the planetary gear reduction device 13 and the components of the electromagnetic clutch 12 are almost completely shielded by the shielding member 9 except for a small portion necessary for the intermediate transmission shaft 15 to penetrate. Therefore, the scattering of the grease generated in the planetary gear reduction device 13 is reliably prevented by the shielding member 9, and it is possible to prevent a defective engagement operation of the electromagnetic clutch 12 caused by the intrusion of the scattered grease. In addition, by providing the shielding member 9, in the planetary gear reduction device 13, a shortage of grease due to the scattering is reduced over time, and normal transmission operation of the planetary gear reduction device 13 is guaranteed for a long period of time. Additional effects can also be obtained.

FIG. 3 is an enlarged sectional view of an auxiliary force generating section 10 showing another embodiment of the present invention.

In the assisting force generator 10 shown in this figure, a planetary roller speed reducer 17 is provided instead of the planetary gear speed reducer 13 in FIG. This planetary roller reduction device 17 has an intermediate transmission shaft.
A plurality of planetary rollers 52, 52, which are respectively in rolling contact with each other, are arranged between a sunshaft 51 formed by increasing the diameter of the middle part of 15 and a fixed ring 53 fixedly fitted in the housing 10a, These are rotatably supported by the carrier 30 spline-coupled to the end of the transmission shaft 14. The driving force of the motor 11, which is taken out to the intermediate transmission shaft 15 by the engagement of the electromagnetic clutch 12, is transmitted to the planetary rollers 52, 52 via a sun shaft 51 formed in the middle of the intermediate transmission shaft 15. The power is transmitted to these revolving shafts, that is, the transmission shaft 14 with a predetermined speed reduction. Fixed ring 53
Are fixed in the housing 10a by being sandwiched between both sides by hollow disc-shaped spacer plates 54 and 55. Spacer plate 5
The inner circumference of 4,55 reaches the inside of the inner circumference of the fixed ring 53, and these spacer plates 54,55 are attached to the planetary rollers 52,52.
The movement of the planetary roller 5 in
.. And the fixed ring 53 are maintained in the axial direction. In this embodiment, the spacer plate 5
4, 55, a shielding member that extends between the electromagnetic clutch 12 and the planetary roller reduction device 17 by extending the spacer plate 54 located on the electromagnetic clutch 12 side to near the outer periphery of the boss portion 22a of the armature portion 22. We use as. That is, in the housing 10a of the auxiliary force generation unit 10, the planetary roller reduction device 1
7 and the electromagnetic clutch 12 are formed by the spacer plate which also functions as a shielding member, except for a small portion necessary for the penetration of the intermediate transmission shaft 15, specifically, for the penetration of the boss portion 22a. Shielded at 54. Therefore, the scattering of the lubricating grease generated in accordance with the operation of the planetary roller reduction device 17 is reliably prevented by the spacer plate 54, so that the engagement operation failure of the electromagnetic clutch 12 is prevented beforehand, and the planetary roller reduction device 17 is prevented. The shortage of grease over time is eliminated, and the normal transmission operation by the planetary roller reduction device 17 is guaranteed for a long period of time.

The electromagnetic clutch 12 in this embodiment is slightly different from the electromagnetic clutch 12 shown in FIG. That is, the armature portion 22 is provided with a disk-shaped holding plate 22d fixed to the outside of the boss portion 22a externally fitted to the intermediate transmission shaft 15 so as to be substantially parallel to the spacer plate 54. A thin movable plate 22b is attached to the surface of the holding member 20 side, and a friction plate 22c is attached to the surface of the movable plate 22b facing the holding member 20 at a plurality of circumferential positions. Then, when a magnetic field is generated in the vicinity of the armature section 22 through the holder 20 by the excitation of the drive coil 21, the friction plate 22c is deformed by the movable plate 22b around the point where the tack is attached, and the friction plate 22c is deformed.
The output shaft 11a and the intermediate transmission shaft 15 are engaged with each other while sliding on the friction plate 20c. The holding plate 22d forms a narrow gap extending radially outward with the spacer portion 54, and grease leaking from between the inner peripheral edge of the spacer plate 54 and the boss portion 22a is formed on the friction plate 20c, It has the effect of preventing it from reaching the sliding contact area of 22c.

In these embodiments, the steering assist motor is
Although the configuration in which the output of the motor 11 is transmitted to the middle of the lower shaft 2 connected to the pinion of the rack and pinion type steering mechanism has been described, the output of the motor 11 may be transmitted to other parts in the steering mechanism. Alternatively, the present invention can be applied to a steering mechanism other than the rack and pinion type.

Further, the urging means of the intermediate transmission shaft 15 is not limited to the wave washer 16 shown in the embodiment, and it goes without saying that other urging means such as a coil spring and a disc spring may be used.

〔effect〕

As described in detail above, in the power steering device according to the present invention, an intermediate transmission shaft supported at both ends is provided between the output shaft of the steering assist motor and the output shaft connected to the steering mechanism. Since the armature portion of the electromagnetic clutch is supported, the inclination of the armature portion can be kept slightly, and since the intermediate transmission shaft is pressed against the output shaft side by the biasing means, the intermediate transmission shaft is And the armature part supported thereby is correctly positioned with respect to the output shaft, and it is possible to easily realize a predetermined circumferentially uniform initial gap between the friction plates respectively attached to the armature part side and the output shaft side, It is possible to prevent the occurrence of operational inconvenience due to the failure of the initial gap beforehand, and the shielding member provided between the reduction gear provided on the intermediate transmission shaft and the electromagnetic clutch is used to reduce the speed reduction gear. Is reliably prevented from entering the components of the electromagnetic clutch, there is no risk of malfunction of the electromagnetic clutch due to the adhesion of the lubricant, and the motor from the steering assist to the steering mechanism is not The present invention has excellent effects, such as reliable transmission of steering assist force.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a main part of a power steering apparatus according to the present invention, FIG. 2 is an enlarged sectional view of an auxiliary force generating section, and FIG. 3 is an auxiliary force generating apparatus showing another embodiment of the present invention. It is an expanded sectional view of a part. 1 ... upper shaft, 2 ... lower shaft, 3 ... torsion bar,
6 Torque sensor 9, Shielding member 10, Auxiliary force generating unit, 11 Motor, 11a Output shaft, 12 Electromagnetic clutch, 13 Planetary gear reduction device, 14 Transmission shaft , 15 ……
Intermediate transmission shaft, 16 Wave washer, 17 Planetary roller reduction gear, 20 Holder, 21 Drive coil, 22
Armature part, 20c, 22c …… Friction plate, 54,55 …… Spacer plate

Claims (2)

(57) [Claims] An operation of an armature section between an output shaft of a steering assist motor driven based on a detection result of a steering torque and a transmission shaft to a steering mechanism in response to excitation and demagnetization of a drive coil thereof. A power steering device provided with an electromagnetic clutch for disengaging the two shafts, an intermediate transmission shaft supported at both ends between the output shaft and the transmission shaft and supporting the armature portion; And a biasing means for biasing the shaft in the axial direction and pressing it against the supporting portion on the output shaft side. 2. The motive power according to claim 1, further comprising a shielding member between the speed reducer formed on the intermediate transmission shaft and the electromagnetic clutch, which shields both of them, leaving a penetrating portion of the intermediate transmission shaft. Steering gear.