JPH02220970A - Electric power steering device - Google Patents

Abstract

PURPOSE:To miniaturize the title device, and to reduce resistance when an electric motor is not driven by forming a mechanism for connecting the electric motor to a steering shaft by means of a planetary gear mechanism arranged coaxially to the steering shaft. CONSTITUTION:A planetary gear mechanism 51 is provided coaxially to a steering shaft 13 consisting of an input shaft part 15, an output shaft part 19, and a torsion bar part 35, and an electric motor 31 is axially supported to an output gear 69. When a relative rotation rate of the input shaft part 15 with respect to the output shaft part 19 becomes more than a prescribed value, the electric motor 31 is driven, so that auxiliary rotation driving force is applied to the output shaft part 19 by the planetary gear mechanism 51, and steering operation force is reduced. When the electric motor 31 is not driven, resistance against manual rotation of the steering shaft 13 is reduced owing to a planetary gear construction, and this device can also be miniaturized in construction.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electric power steering device in which a steering shaft is rotationally driven by an electric motor in response to rotation of a steering wheel.

(Prior Art) Power steering is a vehicle steering mechanism that applies auxiliary rotational driving force to the steering shaft in accordance with the rotation of the steering wheel in order to reduce the steering force required to steer the vehicle. Devices have been proposed, and such power steering devices are often hydraulically actuated.

In a hydraulic power steering device, for example, the flow rate of hydraulic oil is adjusted depending on the vehicle speed, so that the steering operation force is effectively reduced when the vehicle is running at low speed. When the vehicle is running at relatively high speeds, in order to ensure the running stability of the vehicle,
Vehicle speed-sensitive control is performed so that the steering force is not reduced compared to when driving at low speeds. In a hydraulic power steering device that performs such vehicle speed-sensitive control, the hydraulic pressure generated by a hydraulic pump that is constantly driven by the engine mounted on the vehicle is constant even when the vehicle is running at low speed. is used to provide auxiliary rotational driving force to the steering shaft, but it is not used and disappears when the vehicle is running at high speed. Therefore, when the vehicle is running at high speed, the engine Output would be wasted.

Therefore, it is possible to provide auxiliary rotational driving force to the steering shaft as needed without wasting engine output, and the configuration can be simplified compared to a hydraulically operated type. An electric power steering device that uses an electric motor to provide an auxiliary rotational driving force to the steering shaft according to the rotation of the steering wheel is also disclosed in, for example, Japanese Patent Laid-Open No. 60-53463 or Japanese Patent Laid-Open No. 62-137270. It has been proposed as follows. In these conventionally proposed electric power steering devices, the rotational driving force from the electric motor is applied to the steering via a reduction gear mechanism consisting of a combination of spur gears engaged with the output part of the electric motor or a pole nut mechanism. The steering shaft is configured to be transmitted to the shaft, thereby providing auxiliary rotational driving force to the steering shaft when the electric motor is activated.

(Problem to be Solved by the Invention) However, as described above, an electric power steering device in which the rotational driving force is transmitted from the electric motor to the steering shaft via a reduction gear mechanism or a pole nut mechanism consisting of a combination of spur gears. In this case, in order to obtain a sufficient reduction ratio in the rotational driving force transmission section, the size of the drive force transmission section must be increased, and when the steering wheel is rotated with the electric motor in an inactive state, Due to its structure, the rotational drive force transmission unit that connects the steering shaft has a large resistance to rotation of the steering shaft, which may affect proper manual steering wheel operation. be.

In view of these points, the present invention provides an electric motor with an auxiliary rotational driving force to a steering shaft in response to rotation of a steering wheel, and the transmission of rotational driving force from the electric motor to the steering shaft is improved by comparison. This is done using a mechanism that can be made compact and provide a sufficient reduction ratio, and when the steering wheel is rotated when the electric motor is not in operation, the rotational drive that connects the electric motor and the steering shaft is used. An object of the present invention is to provide an electric power steering device in which the resistance of a force transmitting part to rotation of a steering shaft is reduced, and proper manual steering wheel operation is ensured.

(Means for Solving the Problem) In order to achieve the above object, an electric power steering device according to the present invention includes an input shaft portion connected to a steering wheel, an output shaft portion engaged with a steering gear portion, and , a steering shaft comprising a connecting portion between an input shaft portion and an output shaft portion, and a rotation amount detection device provided in association with the connecting portion for detecting a relative rotation amount of the input shaft portion with respect to the output shaft portion. an input rotating section that is arranged coaxially with the steering shaft and transmits an external rotational driving force, and an output rotating section that transmits a rotational driving force corresponding to the external rotational driving force to the steering shaft. The electric motor includes a planetary gear mechanism and an output section provided with a gear section that meshes with the input rotation section of the planetary gear mechanism, and the electric motor detects the output shaft section of the input shaft section of the steering shaft by the rotation amount detection section. When it is detected that the amount of rotation relative to the planetary gear mechanism has exceeded a predetermined value, the output section is rotationally driven to transmit external rotational driving force to the input rotation section of the planetary gear mechanism. .

(Function) In the electric power steering device according to the present invention configured as described above, the planetary gear mechanism disposed coaxially with the steering shaft transmits rotational driving force from the electric motor to the steering shaft. A rotational driving force transmission section is formed. When the steering wheel is rotated and the amount of relative rotation of the input shaft portion of the steering shaft to the output shaft portion exceeds a predetermined value, the electric motor is activated according to the output of the rotation amount detection portion that detects this. The rotational driving force of the electric motor is transmitted to the input rotational part of the planetary gear mechanism, and the planetary gear mechanism outputs rotational driving force corresponding to the rotational driving force transmitted to the input rotational part. is transmitted to the steering shaft, and auxiliary rotational driving force is applied to the steering shaft.

In this way, the steering operation force is reduced in response to the rotational operation of the steering wheel, but the rotational drive force transmission section that connects the electric motor and the steering shaft is coaxial with the steering shaft. By forming the planetary gear mechanism arranged in When the steering wheel is turned when the steering wheel is not in operation, the planetary gear mechanism has a structure that provides little resistance to the rotation of the steering shaft, so it is difficult to manually adjust the steering wheel properly. Operation is ensured.

(Example) FIG. 2 shows an example of an electric power steering device according to the present invention.

In this example, the steering wheel 11 is connected to the upper end portion of the input shaft portion 15 of the steering shaft 13, and the lower end portion of the output shaft portion 19 of the steering shaft 13 is connected to the steering wheel via the joint portion 21. It is connected to a gear mechanism 23.

A planetary gear mechanism section 27 including a housing 25 connected to a steering column 24 is attached to an intermediate portion of the steering shaft 13.
Further, an electric motor 31 to which an electromagnetic clutch 31a is attached is supported by the housing 25 and attached to the planetary gear mechanism section 27. The electric motor 31 and the electromagnetic clutch 31a attached thereto are connected to a motor control circuit section for driving and controlling them, but illustration thereof is omitted in FIG. 2.

1 and 3 show details of the intermediate portion of the steering shaft 13 and the planetary gear mechanism 27 attached thereto in the example shown in FIG. It is shown together with 33. In addition, FIG. 3 shows mA-mA in FIG.
Line cross section and ■B-I [[B line cross section is shown.

1 and 3, an input shaft portion 15 inserted through and supported by the steering column 24 is connected to an output shaft portion 19 via a torsion bar portion 35. ．． The torsion bar portion 35 and the output shaft portion 19 constitute the steering shaft 13. Input shaft part 1
5 and the torsion bar part 35 is connected to the end 35a of the torsion bar part 35 on the input shaft part 15 side.
While the sleeve 37 is splined,
A concave portion 15a formed in the input shaft portion 15 is engaged with a spline, and an end portion 35a of the torsion bar portion 35
, the input shaft portion 15 and the sleeve 37 are connected to the engagement pin 3
9 restricts the movement of each axial direction. Further, the connection between the output shaft portion 19 and the torsion bar portion 35 is such that a sleeve 41 is attached to the end portion 35b of the torsion bar portion 35 on the output shaft portion 19 side.
are spline-engaged, and the spacer 43 is engaged with a stepped portion formed at the end 35b of the torsion bar portion 35, and is screwed into a threaded portion formed at the end 35b of the torsion bar portion 35. The sleeve 41 is fitted with a recess 19a formed in the output shaft portion 19, with its axial movement being restricted by a nut 45.
This is achieved by spline engagement.

Sleeves 37 and 41 arranged on torsion bar part 35
, the housing 25 of the planetary gear mechanism 27 connected to the steering column 24 via the bearings 47 and 49 is connected to the sleeves 37 and 4, respectively.
1 is attached so that it can rotate freely. A planetary gear mechanism 51 disposed coaxially with the steering shaft 13 is housed inside the housing 25.

A planetary gear mechanism 51 disposed coaxially with the steering shaft 13 includes a drive sun gear 53. which is integrally formed with the sleeve 41. The sleeve 41 is fitted into the sleeve 41 via a spacer 55, and faces the drive sun gear 53 with a flange provided on the spacer 55 sandwiched therebetween, and an integrally formed cylindrical portion is spline-engaged with the housing 25. Fixed sun gear 57 with limited rotation. A planetary carrier 59 is rotatably engaged with the outer circumferential surface of the sleeve 41 and has a ring gear 59a on its peripheral edge, and a planetary carrier 59 is provided with ring gears 59a on the side surface of the planetary carrier 59 at equal angular intervals on the same circumference. , is configured to include three planetary gears 63 rotatably attached to a mounting shaft 65, and each of the three planetary gears 63 is
A large diameter gear 61 that meshes with the driving sun gear 53 and a small diameter gear 62 that meshes with the fixed sun gear 55 are integrally formed.

Furthermore, the housing 2 in the planetary gear mechanism section 27
5, the output shaft 31b of the electric motor 31 is
The output shaft 31b is rotatably supported by the housing 25 via bearings 66 and 67, and the output gear port 9, which meshes with a ring gear 59a provided on the planetary carrier 59, is formed by a spline. are engaged.

In this way, in the planetary gear mechanism 51, the planetary carrier 59 plays a role as an input rotating part to which the rotational driving force of the output shirt 31b of the electric motor 31 is transmitted from the output gear port 9 as an external rotational driving force. achieve,
Further, the three planetary gears 63 serve as an output rotation unit that transmits rotational driving force corresponding to the rotational driving force of the output shaft 31b of the electric motor 31 to the steering shaft 13 via the sleeve 41. has been done.

Further, inside the housing 25 of the planetary gear mechanism section 27, a sleeve 71 into which the sleeve 37 is inserted is screwed onto the end of the sleeve 41 on the sleeve 37 side.
The rotation amount detects the relative rotation amount of the input shaft portion 15 with respect to the output shaft portion 19 in the steering shaft 13 based on the relative displacement amount in the rotation direction of the torsion bar portion 35 between the sleeve 37 and the sleeve 71. A torque sensor 73 is attached as a detection section. A detection output signal St is obtained from the torque sensor 73 and is supplied to the motor control circuit section 33 .

With this configuration, when the steering wheel 11 is rotated, the rotation of the steering wheel 11 is transmitted to the steering shaft 13 , and the input shaft portion connected by the torsion bar portion 35 is transmitted to the steering shaft 13 . 15 and the output shaft portion 19 cause relative rotation as the torsion bar portion 35 twists, and the amount of relative rotation of the input shaft portion 15 with respect to the output shaft portion 19 is detected by the torque sensor 73. and,
When the amount of relative rotation of the input shaft section 15 with respect to the output shaft section 19 exceeds a predetermined value, then the torque sensor 73
In response to the detection output signal St sent from the motor, the motor control circuit unit 33 operates the motor 31 and engages the electromagnetic clutch 31a attached to the motor 31, so that the output shaft 31b of the motor 31 is rotationally driven. state.

Thereby, the rotational driving force of the output shaft 31b of the electric motor 31 is transmitted from the output gear port 9 to the ring gear 5 provided on the planetary carrier 59 in the planetary gear mechanism 51.
9a, the planetary carrier 59 is rotated, and as the planetary carrier 59 rotates, each of the three planetary gears 63 rotates around the mounting shaft 65, and the small diameter gear 62 meshes with the rotation of the planetary carrier 59. It is set to revolve around a fixed sun gear 57. the result,
A drive sun gear 53 that meshes with a large diameter gear 61 integrally formed with a small diameter gear 62 in a planetary gear 63 is connected to an output gear 9. The steering shaft 1 is rotated while being reduced in speed based on a reduction ratio determined by the ratio of the number of teeth of the ring gear 59a1 and the large diameter gear 61.
The output shaft portion 19 at No. 3 is rotationally driven by the auxiliary rotational driving force from the electric motor 31.

Then, the rotation of the output shaft portion 19 under the application of the auxiliary rotational driving force from the electric motor 31 is transmitted to the steering gear mechanism 23, and the steering operation force is reduced.

Next, when the steering wheel 11 is rotated with the electric motor 31 in a non-operating state, the steering wheel 1
The rotation of the input shaft portion 15 accompanying the rotation of the input shaft portion 1 is transmitted to the output shaft portion 19 through the torsion bar portion 35,
Further, the rotation of the output shaft section 19 is transmitted to the steering gear mechanism 23. Further, in such a case, the rotation of the output shaft portion 19 is transmitted to the drive sun gear 53 via the sleeve 41. Thereby, the planetary gear 63 consisting of a large diameter gear 61 that meshes with the drive sun gear 53 and a small diameter gear 62 that is integrally formed with the large diameter gear 61 rotates around the mounting shaft 65 and the fixed sun gear 57 that the small diameter gear 62 meshes with. Further, the planetary carrier 59 and the output gear port 9 that meshes with the ring gear 59a provided on the planetary carrier 59 are rotated, and the rotational driving force of the output shaft portion 19 is transferred to the planetary gear mechanism 51. It will be transmitted to

However, when doing so, the output shaft portion 19
The transmission of the rotational driving force from the planetary gear mechanism 51 to the planetary gear mechanism 51 is as follows.
Due to the structural characteristics of the planetary gear mechanism 51, the transmission is performed with relatively high efficiency, and the resistance of the planetary gear mechanism 51 to rotation of the steering shaft 13 is small, so that the steering operation force is relatively low. It will be a small target.

(Effects of the Invention) As is clear from the above explanation, according to the electric power steering device according to the present invention, the rotational driving force of the electric motor is transmitted to the steering shaft in accordance with the rotation of the steering wheel. In applying auxiliary rotational driving force to the steering shaft, the mechanism that connects the electric motor and the steering shaft is formed by a planetary gear mechanism arranged coaxially with the steering shaft, so that the rotational driving force from the electric motor to the steering shaft is reduced. can be transmitted using a mechanism that can be relatively compact and provide a sufficient reduction ratio, and when the steering wheel is rotated while the electric motor is in a non-operating state, Due to its structure, the planetary gear mechanism has a low resistance to rotation of the steering shaft, and has the advantage of ensuring proper manual steering wheel operation.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a main part of an example of an electric power steering device according to the present invention, FIG. 2 is a side view showing an example of an electric power steering device according to the present invention, and FIG. 3 is a view similar to that shown in FIG. TJiA-mA line cross section and I[IB-I
[It is a cross-sectional view showing the IB line cross section. In the figure, 11 is a steering wheel, 13 is a steering shaft, 15 is an input shaft part, 19 is an output shaft part, 23 is a steering gear mechanism, 27 is a planetary gear mechanism part, 31 is an electric motor, 31b is an output shaft, 3
3 is a motor control circuit section, 35 is a part of a torsion bar, 51
is a planetary gear mechanism, 69 is an output gear, and 73 is a torque sensor. Patent applicant Mazda Motor Corporation

Claims (1)

[Scope of Claims] A steering shaft comprising an input shaft portion connected to a steering wheel, an output shaft portion engaged with a steering gear portion, and a connecting portion between the input shaft portion and the output shaft portion. a rotation amount detection section provided in association with the coupling section and configured to detect the relative rotation amount of the input shaft section with respect to the output shaft section; a planetary gear mechanism having an input rotation part to which a driving force is transmitted and an output rotation part to transmit a rotational driving force according to the external rotational driving force to the steering shaft; and the input rotation of the planetary gear mechanism. an output part provided with a gear part that meshes with the output part, and when the rotation amount detection part detects that the relative rotation amount of the input shaft part of the steering shaft with respect to the output shaft part has exceeded a predetermined value, An electric power steering device comprising: an electric motor that rotationally drives the output section to transmit external rotational driving force to the input rotation section of the planetary gear mechanism.