JP2578655B2 - Electric power steering device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus in which a steering force is assisted by a driving force of an electric motor.

(Prior Art) FIG. 2 shows an overall view of a rack-and-pinion type electric power steering apparatus as an object, and FIG. 3 shows a conventional example of an electric drive unit, in which a wheel 1 has a knuckle arm 2. To the steering link 3. A rack 4 is formed on the steering link 3, and a pinion 5 a formed on a pinion shaft 5 and a second pinion 7 provided on a pinion shaft 6 of the reduction gear R are engaged with the rack 4. .

In the speed reducer R, an electric motor m is installed in a case 8, and these cases 8 and the electric motor m are connected by fastening bolts 9.

The speed reducer R includes a row A gear mechanism located on the electric motor m side, a row B gear mechanism located on the pinion shaft 6, and a ring gear 10 installed on the inner peripheral side of the case 8. It is configured. The A-row side gear mechanism meshes with the A-row side sun gear 12 fixed to the output shaft 11 of the electric motor m and the A-row side sun gear 12 and also engages with the ring gear 10. The A-row planet gear 13 that revolves around the A-row sun gear 12 while rotating by the rotational force of the above, and is connected to the A-row planet gear 13 via a bearing 14 so that the A-row planet gear 13 rotates. And an A-row carrier 15 that rotates as the A-row planet gear 13 revolves.

The row B side gear mechanism meshes with the row B sun gear 16 fixed to the row A carrier 15 and both the row B sun gear 16 and the ring gear 10.
B-planet gear 17 which revolves around the B-row sun gear 16 along the ring gear 10 while rotating by the rotational force from 16, and is connected to the B-row planet gear 17 via a bearing 18, Row B planet gears 17
And a row B carrier 19 that rotates with the revolution of the row B planet gear 17.

The B-row carrier 19 is fixed to the pinion shaft 6, and the A-row carrier 15 and the pinion shaft 6 are rotatably supported via a bearing 20.

The rotation of the ring gear 10 is restricted by a plurality of pins 21, and an oil seal 22 and a bearing 23 are mounted between the pinion shaft 6 and the case 8. Further, reference numeral 24 in the figure denotes a seal ring.

The input shaft 26 together with the steering wheel 25
Is turned, the pinion shaft 5 attempts to rotate in connection therewith, but at this time, the pinion 5a does not rotate because the rack 4 is difficult to move due to the ground resistance of the wheels 1. If the pinion 5a does not rotate as described above, a distortion is generated therein. This distortion is detected by a distortion sensor (not shown) and transmitted to the controller C.

Then, the controller C rotates the electric motor m according to the signal from the distortion sensor. When the electric motor m rotates in this way, the A-row sun gear 12 rotates together with the output shaft 11. Due to the rotation of the row A sun gear 12, the row A planet gear 13 rotates and revolves around the row A sun gear 12 along with the ring gear 10. The A-row side carrier 15 rotates by the revolution of the A-row side planet gear 13. When the row A carrier 15 rotates, the row B sun gear 16 rotates, and with this rotation, the row B planet gear 17 revolves around the row B sun gear 16 along the ring gear 10 while rotating. .
Due to the revolution of the B-row side planet gear 17, the B-row side carrier 19 rotates, and the pinion shaft 6 further rotates. By such an action, the rotation of the electric motor m is transmitted to the pinion shaft 6 in a decelerated state.

If the pinion shaft 6 rotates as described above,
The second pinion 7 fixed thereto also rotates to move the rack 4 left or right to steer the wheels 1.

(Problem to be Solved by the Present Invention) In the conventional device as described above, if the electric motor m fails and the output shaft 11 is stuck, even the manual steering with the steering wheel 25 cannot be performed. That is, when the output shaft 11 of the electric motor m is fixed, even if the steering wheel 25 is turned to rotate the pinion 5a to move the rack 4, the reduction gear R side engaged with the same rack 4 Since the rotation of the second pinion 7 is blocked due to the fixation of the electric motor m, the rack 4 does not move.

For this reason, if the electric motor m breaks down and the output shaft 11 is stuck, manual steering operation cannot be performed, resulting in a problem that a very dangerous state is caused.

Further, when an impact force is generated at the kickback or at the lock end, an overload due to the inertia of the electric motor m acts on components such as the output shaft and each gear, so that there is a problem that they are damaged.

An object of the present invention is to provide an electric power steering device that can perform a manual steering operation even when an electric motor fails, and that can absorb an impact.

(Means for Solving the Problem) According to the present invention, a rack meshing with a pinion connected to a steering wheel is connected to wheels, and the driving force of an electric motor is transmitted through a second pinion meshing with the rack. In a rack-and-pinion type electric power steering device that assists the steering force, an A-row side sun gear fixed to the output shaft of the electric motor, a mesh with the A-row side sun gear, and a reduction gear case. An A-line planet gear that meshes with a ring gear attached to the inner surface in a state where rotation is restricted, rotates by the rotation of the A-row sun gear, and revolves around the A-row sun gear along the ring gear. Row A connected to the row A planet gears and rotating with the revolution of the row A planet gears A side carrier, a row B sun gear fixed to the row A carrier, and rotating with the rotation of the row A carrier, meshing with the row B sun gear, and meshing with the ring gear; A reduction gear comprising a B-row planet gear that rotates by rotation and revolves around the B-row sun gear along the ring gear, and a B-row carrier that rotates as the B-row planet gear revolves. The present invention relates to an electric power steering apparatus in which the output of the motor is transmitted to a second pinion of a pinion shaft connected to the B-row carrier and transmitted to a rack that meshes with the pinion.

Further, according to the present invention, the ring gear in the electric power steering device is divided into a row A and a row B, and a friction torque slip mechanism is radially provided on an outer periphery of the ring gear on the row A. The torque slip mechanism has a pad having an arcuate surface in contact with the outer peripheral surface of the row A ring gear, and normally regulates the rotation of the row A ring gear by urging the pad in the direction of the row A ring gear. And a resilient member that permits rotation of the A-row side ring gear when a load equal to or greater than the set value is applied.

(Operation of the Present Invention) According to the electric power steering apparatus of the present invention, the rotation of the A-row side ring gear is normally restricted by the frictional force with the pad. Then, the A-row side sun gear is rotated by the rotation of the motor, whereby the A-row side planet gear rotates on its own axis, and revolves around the A-row side sun gear along the A-row side ring gear in a spring restrained state. Due to the revolution of the planet gears on the row A,
The row carrier rotates. The rotation of the sun gear on the row B causes the planet gears on the row B to rotate and revolve around the sun gear on the row B along the ring gear. Due to the revolution of the B-row planet gear, the B-row carrier rotates,
As a result, the pinion shaft is decelerated to a predetermined value and rotated to operate the rack 4 and the wheels 1 as in the conventional case.

For example, when the output shaft is fixed due to a failure of the motor or the like, the A-row side ring gear rotates against the friction of the outer periphery due to the biasing force of the elastic member acting via the pad. Prevents the lock state from occurring. Therefore, as described above, the electric motor m
Even if the lock state occurs, the manual steering operation is guaranteed, and conversely, even if an impact force is applied from the wheel side, it can be absorbed and not transmitted to the electric motor m.

(Embodiment of the Present Invention) Hereinafter, an embodiment will be described with reference to FIG.

The ring gear of this embodiment is composed of an A-row side ring gear 27 and a B-side ring gear.
It is divided into a row side ring gear 28. The rotation of the B-row side ring gear 28 is restricted by a plurality of pins 29. On the other hand, the rotation of the A-row side ring gear 27 is regulated by the friction type torque slip mechanism 30.

The friction type torque slip mechanism 30 includes a box 31 formed by projecting a part of the case 8 radially outward and a box 31 disposed in the box 31 and having an inner circular surface formed by the A-line ring gear 27. Pad 32 contacting the outer peripheral surface of
And a torque spring 33 housed in the box 31 to urge the pad 32 in the direction of the ring gear 27, and an adjusting screw 34 for adjusting the spring force of the torque spring 33.

The pad 32 has its arc-shaped contact surface pressed against the row A ring gear 27 by a torque spring 33.
The rotation of the row side ring gear 27 is regulated by the frictional force between the row side ring gear 27 and the pad 32.

If the output shaft 11 is stuck due to a failure of the electric motor m or the like, a large overload occurs and the A-row side sun gear 11 is fixed. Slip rotation is enabled against friction based on the urging force of the torque spring 33, thereby preventing the occurrence of a mechanical lock state. Normally, the row A ring gear 27 is provided with a friction type torque slip mechanism 30.
Therefore, the rotation of the electric motor m is transmitted to the pinion shaft 6 in a state where the rotation of the electric motor m is reduced to a predetermined value by the same operation as in the related art.

Also, in the unlikely event that the electric motor m breaks down and the output shaft 11 is fixed and the steering by the steering wheel 25 is required, the rotational force is changed from the input shaft 26 → the pinion shaft 5 → the pinion 5 a → the rack 4 → At the same time as being transmitted to the wheels 1, it is also transmitted to the reduction gear R via the rack 4 → the second pinion 7 → the pinion shaft 6. If the rotational force of the steering wheel 25 at this time overcomes the torque slip value of the friction type torque slip mechanism 30, the A-row side ring gear 27 rotates while being in contact with the pad 32.

Therefore, even if the electric motor m breaks down as described above, if the steering wheel 25 is turned with a force equal to or higher than the torque slip value, the manual steering operation is guaranteed.

Furthermore, when the kickback from the road surface or the impact force at the lock end acts reversely via the rack 4 and the second pinion 7 during normal operation of the electric motor m, a large load acts on each gear. When this load exceeds the torque slip value of the friction type torque slip mechanism 30, the row A side ring gear 27 is driven by the friction type torque slip mechanism.
It rotates against friction caused by 30 biasing forces. When the ring gear 27 rotates in this manner, the impact force is absorbed as described above, and the impact force does not damage components such as the electric motor and the gear.

 According to the present embodiment, the following effects are exhibited.

First, even in the event that the motor output shaft 11 is stuck in the event of a failure of the electric motor m, the A-row side ring gear 27 can overcome the outer peripheral friction and rotate to maintain the slip state, thereby enabling manual steering. In addition, damage to components such as gears can be prevented.

Further, the friction type torque slip mechanism 30 of the present embodiment has a simple configuration and is inexpensive as compared with, for example, an electromagnetic clutch type.

Further, since the frictional force is applied to the pad 32 having an arcuate surface that comes into contact with the outer peripheral surface of the A-row side ring gear 27, another structure such as a ball, a roller, or a claw is used. The impulses at the time of slipping and at the time of starting the electric motor are smaller than those at the time.

Further, the torque slip value can be easily changed by selecting the material of the pad 32 or changing the spring load by the adjusting screw 34.

(Effect of the Present Invention) According to the rack and pinion type electric power steering apparatus of the present invention, even if the output shaft of the electric motor is stuck, the ring gear on the side of the A row can be rotated to maintain the slip state. Steering is guaranteed and its safety can be maintained.

Further, even if the impact force from the pinion shaft side acts reversely through the wheels and the rack, the slip state can be maintained by rotating the row A ring gear as described above, so that damage to the components such as each gear and the like can be prevented. Can be prevented.

Moreover, according to the electric power steering device of the present invention, the configuration is simpler and less expensive than, for example, a power steering device having an electromagnetic clutch.

Still further, since the frictional force is used between the outer peripheral surface having an arcuate surface abutting on the row A side ring gear and the inner peripheral surface of the pad, other configurations, for example, using balls, rollers, claws, etc. There is also an advantage that the slip and the urge at the time of starting the electric motor are reduced as compared with the case of FIG.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of an electric power steering apparatus showing an embodiment of the present invention, FIG. 2 is an overall configuration diagram of a rack and pinion type electric power steering apparatus to which the present invention is applied, and FIG. It is sectional drawing of the principal part of the conventional electric power steering device. 6 ... pinion shaft, 7 ... second pinion, 8 ...
... case, m ... electric motor, 11 ... output shaft, 12 ... A
Row side sun gear, 13 ... A Row side planet gear, 15 ... A
Row carrier, 16 ... B row sun gear, 17 ... B row planet gear, 19 ... B row carrier, 27 ... A row ring gear, 28 ... B row ring gear, 30 ... Friction type Torque slip, 32 ... Pad, 33 ... Spring as elastic member.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Ichiro Miyara 2548 Tsuchida, Kani-shi, Gifu Kayaba Industrial Co., Ltd. Inside Gifu-Kita Plant (72) Inventor Keita Suzuki 1-1-1, Daihatsu-cho, Ikeda-shi, Osaka (72) Inventor Hidenori Katayama 1-1-1, Daihatsu-cho, Ikeda-shi, Osaka Dai-Hatsu Kogyo Co., Ltd. (56) References JP-A-62-218267 (JP, A) JP-A-62-103773 (JP, U.S.A.) ) Actually open 1987-205077 (JP, U)

Claims (1)

(57) [Claims] A rack meshing with a pinion connected to a steering wheel is connected to wheels, and a driving force of an electric motor is transmitted through a second pinion meshing with the rack to assist power steering. In the rack-and-pinion type electric power steering device described above, a row A-side sun gear fixed to the output shaft of the electric motor, a state meshed with the row A-side sun gear, and rotation restricted by the inner surface of the reduction mechanism case. Meshes with the ring gear attached at step A, rotates along with the rotation of the sun gear on the side of row A, and rotates along the ring gear.
Row A planet gear revolving around the row sun gear, row A carrier connected to the row A planet gear, and rotating with the rotation of the row A planet gear, fixed to the row A carrier A row B sun gear that rotates with the rotation of the row A carrier, meshes with the row B sun gear, meshes with the ring gear, rotates by the rotation of the row B sun gear, and rotates along the ring gear. The output of the motor is supplied to the B-row carrier via a speed reducer composed of a B-row planet gear revolving around the row sun gear and a B-row carrier rotating with the revolution of the B-row planet gear. To the second pinion in the pinion shaft connected to the pinion, and to the rack engaged with the pinion, The ring gear is divided into row A and row B, and a friction torque slip mechanism is radially provided on the outer periphery of the ring gear on row A. The friction type torque slip mechanism is provided on the outer peripheral surface of the row A ring gear. A pad having an arcuate surface in contact with the pad, and in normal times, the pad is urged in the direction of the row A side ring gear to regulate the rotation of the row A side ring gear.
An electric power steering apparatus, comprising: an elastic member that allows rotation of the row side ring gear.