JPH0386683A - Deceleration mechanism for motor-driven power steering device - Google Patents

Abstract

PURPOSE:To reduce the number of parts to restrict the generation of great gear noise by decelerating the rotating speed of an electric motor at the gear ratio of a hypoid gear pinion on the output shaft end of the electric motor to a hypoid gear on the shaft end of a pinion, and transmitting the decelerated speed to the pinion. CONSTITUTION:A hypoid gear pinion 23 is provided on the shaft end connected to an electric motor m', and a hypoid gear wheel 24 is provided on the shaft end of a pinion 6'. The rotating speed of the electric motor m' is decelerated at the gear ratio between a pair of the hypoid gears 23, 24 to be transmitted to the pinion 6'.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention provides a reduction mechanism for an electric power steering device,
For more information, see Electric motors for forced steering.

and a pinion for forced steering, the electric power steering device is of a type in which the pinion is rotated by the drive of the electric motor and the rotational force is transmitted to the steering rack.
The invention relates to a speed reduction mechanism interposed between the electric motor and the pinion.

(Prior Art) A power steering device for steering a car, an outboard motor, etc. is equipped with an electric motor for forced steering and a pinion for forced steering, and the pinion rotates when the electric motor is driven. 2. Description of the Related Art Electric power steering devices that transmit power to a steering rack are known.

FIG. 3 shows a schematic configuration of a conventional electric power steering device for an automobile based on the above method.

Here, the rotation of the steering wheel 1 is transmitted to a steering rack 4 via a steering pinion 3 provided at the tip of an input shaft 2 linked to the steering wheel 1. That is, when the steering wheel 1 rotates, the pinion 3 rotates in conjunction with the rotation, and the rack 4 meshing with the pinion 3 moves in the left-right direction in the figure due to the rotational force of the pinion 3. The wheels 5 are steered by the movement of 4.

In addition to the pinion 3 provided on the input shaft 2, the rack 4 is also engaged with a pinion 6 for forced steering that rotates when driven by an electric motor m for forced steering. When the pinion 6 rotates,
As in the case described above, the rack 4 moves left and right in the figure to steer the wheels 5.

The rack 4 is moved by the pinion 6 when the rack 4 cannot be moved by the rotation of the pinion 3 due to the rotation of the steering wheel 1 (due to installation pressure, etc.). That is, rotate the steering wheel l,
If the rack 4 is not moved by the rotational force of the rotating pinion 3, the electric motor m is driven to rotate the pinion 6, and the rack 4 is forcibly moved by the rotational force. In this case, a strain sensor 7 is provided on the pinion side, a detection signal from the strain sensor 7 is sent to a controller C, and the controller C drives and controls the electric motor m according to the detection signal from the strain sensor 7. .

A speed reduction mechanism R is interposed between the electric motor m and the pinion 6 to reduce the rotational speed of the electric motor m to a predetermined speed and transmit it to the pinion 6.

The speed reduction mechanism R here is an electric motor m that rotates at high speed.
Since the rotation of
Conventionally, the system is generally composed of two sets of planetary gears.

FIG. 4 shows the detailed structure of the speed reduction mechanism R.

Here, the electric motor m and the pinion 6 are arranged to face each other so that their axes are on the same line. Between the electric motor m and the pinion 6, there is interposed a speed reduction mechanism R including two sets of planetary gears built into the casing 10.

A sun gear 9 that rotates in conjunction with the rotation of the output shaft 8 is provided at an end of the output shaft 8 of the electric motor m. The rotation of sun gear 9 is transmitted to planetary gear 12 which is interposed between ring gear 11 provided on the inner peripheral surface of cylindrical casing 10 and sun gear 9 and meshes with both.

Therefore, when the sun gear 9 is rotated by the drive of the electric motor m, the planetary gear 12 comes to revolve around the sun gear 9 while rotating. In this case, the sun gear 9 is rotatably supported on the shaft core of the first carrier 13, and the planetary gear 12 is supported on the support shaft 14 provided on the first carrier 13.
is rotatably fitted to the In addition, the first carrier 13
is rotatably supported by the shaft core portion of the shaft end of the pinion 6, and rotates as the planetary gear 12 revolves.

Further, a sun gear 16 that rotates in conjunction with the rotation of the first carrier 13 is provided on a shaft 15 portion of the first carrier 13 that is provided on the opposite side of the axis from the support shaft 14 . The rotation of this sun gear 16 is caused by the ring gear 11
and sun gear 16, and is transmitted to planetary gear 17 which meshes with both. Therefore, the first carrier 1
When the sun gear 16 rotates in conjunction with the rotation of the planet gear 3, the planetary gear 17 comes to revolve around the sun gear 16 while rotating. In this case, the planetary gear 17 is connected to the second carrier 1
It is rotatably fitted onto a support shaft 19 provided at 8. Further, the second carrier 18 has its shaft core portion connected to the pinion 6.
It is integrally and non-rotatably fitted to the shaft end of the planetary gear 17, and rotates as the planetary gear 17 revolves. Then, the binion 6 rotates integrally with the rotation of the second carrier 18, and the rack 4
is moved in the left-right direction (in the case shown, in the direction perpendicular to the plane of the paper), thereby power-assisting the steering force.

In the reduction mechanism R, the rotation speed of the output shaft 8 of the electric motor m is such that the rotation of the output shaft 8 is transmitted to the sun gear 9 → planet gear 12 → ring gear 11 → sun gear 16 → planet gear 17 → ring gear 11. In the process of deceleration, the speed is sequentially decelerated and transmitted to the pinion 6. Also, its reduction ratio is sun gear 9, planet gear 12, ring gear 1.
1 and the gear ratios of the sun gear 16, planet gear 17, and ring gear 11.

(Problems to be Solved by the Present Invention) By the way, in the above-mentioned conventional electric power steering device, there are two sets of speed reduction mechanisms R interposed between the electric motor m for forced steering and the pinion 6 for forced steering. However, in the case of such a reduction mechanism H, the number of parts is extremely large (sun gear 9, planet gear 12, ring gear 11, first carrier 13,
, sun gear 16, planet gear 17, second carrier 18, etc.), which increases costs and generates loud gear noise (
There was a problem in that a knocking sound was generated between the teeth of each gear that meshed with each other (due to the large number of meshes).

This idea was made in view of the circumstances mentioned above.
The purpose is to provide a speed reduction mechanism for an electric power steering device that has a small number of parts and does not generate loud gear noise.

(Means for Solving the Problems) In order to achieve the above object, the reduction mechanism of the electric power steering device of this invention connects an electric motor for forced steering and a pinion for forced steering to a shaft linked to the electric motor. A hypoid gear pinion is provided at the end, and a hypoid gear wheel is provided at the shaft end of the pinion, and the rotational speed of the electric motor is reduced by the gear ratio of the pair of hypoid gears and transmitted to the pinion.

(Operation of the present invention) In the speed reduction mechanism with such a configuration, the specified speed reduction can be achieved using only the set of hypoid gears (pinion and wheel), so the number of parts can be reduced, and the hypoid gears make tooth-to-tooth contact with each other. Therefore, gear noise caused by meshing is extremely small.

(Embodiment of the present invention) Hereinafter, an embodiment of the present invention will be described in detail based on the drawings.

FIG. 1 shows a reduction mechanism R' of an electric power steering device according to this invention.

Here, the forced steering electric motor m' and the forced steering pinion 6' are arranged such that their axes 0 and O' are perpendicular to each other. And those electric motors m'
A speed reduction mechanism R' is interposed between the pinion 6' and the pinion 6'. In this case, the casing 20 of the electric motor m' and the casing 21 of the pinion 6' are connected via the casing 22 of the speed reduction mechanism R'.

The speed reduction mechanism R' includes a hypoid gear pinion 23 provided at the end of the output shaft 8' of the electric motor m', and a pinion 6.
The electric motor m' is provided with a set of hypoid gears including a hypoid gear wheel 24 provided at the shaft end of the electric motor m', and the rotation of the output shaft 8' of the electric motor m' is transmitted to the pinion 6' through the hypoid gear pinion 23 and the hypoid gear wheel 24. At the same time, the rotational speed of the output shaft 8' is transmitted to
The gear ratio of the hypoid gear pinion 23 and the hypoid gear wheel 25 is used to reduce the speed.

In this case, the hypoid gear pinion 23 is offset from the axis of the hypoid gear wheel 24, as shown in FIG.
They are interlocked. Such a hypoid gear pinion 23 is arranged on the axis 0 of the electric motor m' and is connected to the casing 22 by a plurality of angular bearings 25.2.
5', and the rear end is rotatably supported by the output shaft 8.
’ is linked. On the other hand, hypoid gear wheel 2
4 is integrally and non-rotatably fitted with its shaft core to the shaft end of pinion 6', and is rotatably engaged with hypoid gear pinion 23. Therefore, when the output shaft 8' of the electric motor m' rotates, the hypoid gear pinion 23 rotates in conjunction with it, and the rotation is transmitted to the pinion 6' via the hypoid gear wheel 24.
The rack 4' moves in the left-right direction (in the illustrated case, in a direction perpendicular to the plane of the drawing) by the rotational force of the pinion 6'.

Note that, as described above, when the output shaft 8' of the electric motor m' rotates and the hypoid gear pinion 23 rotates,
A thrust force is generated in this hypoid gear pinion 23 due to engagement with the hypoid gear wheel 24, but this thrust force is generated by the angular bearing 25.
′ is absorbed. Also, when the rack 4' moves due to the rotational force of the binion 6', the rack 4'
This thrust force is absorbed by the plurality of angular bearings 26 and 26' that rotatably support the end of the rack 4' of the binion 6', and thereby the hypoid gear wheel 24 and the hypoid gear The meshing state of the pinion 23 is always in a predetermined state.

In the case of the speed reduction mechanism R' of the embodiment configured as described above, the - set of hypoid gears (binion 23 and wheel 24) enables a specified speed reduction, so the number of parts is small and it can be provided at low cost. . Additionally, since it uses a hypoid gear in which the teeth contact each other while sliding, the gear noise is extremely low.

Note that even if the above-mentioned hypoid gear's binion 23 and wheel 24 are replaced with a worm gear and worm wheel, the number of parts and gear noise can be reduced. It has many drawbacks, such as extremely low conversion efficiency and reverse rotation efficiency, and is larger than a hypoid gear due to the meshing structure of both gears, so it is not preferred in practice.

(Effects of the present invention) As explained above, the deceleration mechanism of the electric power steering device of this idea arranges the electric motor for forced steering and the binion for forced steering so that their axes are perpendicular to each other. Also, a hypoid gear pinion is provided at the output shaft end of the electric motor, and a hypoid gear wheel is provided at the shaft end of the pinion, and the rotational speed of the electric motor is reduced by the gear ratio of the pair of hypoid gears,
Since the signal is transmitted to the pinion, the number of parts can be reduced, the gear can be provided at low cost, and there is no loud gear noise.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a reduction mechanism of an electric power steering device according to an embodiment of this invention, Fig. 2 is a schematic side view showing the engagement state of the hypoid gear pinion and hypoid gear wheel of the reduction device, and Fig. 3 is a conventional one. FIG. 4 is a detailed sectional view of a speed reduction mechanism provided in the electric power steering device. 4'... Rack for steering, 6'... Binion for forced steering, 8'... Output shaft of electric motor, 23... Hypoid gear pinion, 24... Hypoid gear wheel, m'...・Electric motor for forced steering, R'...
Reduction mechanism.

Claims (1)

[Claims] The electric power steering device includes an electric motor for forced steering and a pinion for forced steering, and the pinion rotates when the electric motor is driven, and the rotational force is transmitted to the steering rack. In the speed reduction mechanism interposed between the motor and the pinion, a hypoid gear pinion is provided at the shaft end linked to the electric motor, and a hypoid gear wheel is provided at the shaft end of the pinion, and the gear ratio of the pair of hypoid gears determines the A speed reduction mechanism for an electric power steering device, characterized in that the rotational speed of an electric motor is reduced and transmitted to the pinion.