JPH0537743Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention is a rack-and-pinion type electric power steering device, specifically, power can be transmitted from an electric motor to a pinion connected to a steering wheel using a staggered gear mechanism. The present invention relates to an electric power steering device connected to an electric power steering device.

(Prior art) An electric power steering device includes an electric motor in the steering force transmission system from the steering wheel to the steering wheel, and uses the steering assist force outputted by the electric motor together with the manual steering force applied to the steering wheel. The information is transmitted to the opposite wheels, reducing the driver's steering burden. Conventionally, as this type of electric power steering device, for example, one described in Japanese Patent Application Laid-Open No. 59-50864 has been known. This electric power steering device transmits manual steering force applied to the steering wheel to the rack shaft by meshing a pinion connected to the steering wheel with a rack shaft connected to the steering wheel, and also connects a ball screw to the rack shaft. A ball screw groove of the mechanism is formed, and a ball nut connected to the output shaft of the electric motor is screwed into the ball screw groove of the rack shaft via a large number of balls, and the steering assist force output from the electric motor is transferred to the rack shaft through the ball screw mechanism. to communicate.

(Problem to be solved by this invention) However, in such conventional electric power steering devices, high precision is required for machining the ball screw groove of the ball screw mechanism onto the rack shaft. Because it is long, it is difficult to process with high precision due to the effects of heat treatment distortion, etc.
There were problems in that the manufacturing cost was high and assembly was difficult.

Furthermore, in such conventional electric power steering devices, the ball nut is screwed into the ball screw groove formed in the rack shaft via a large number of balls to form a ball screw mechanism, so that the steering reaction force is reduced during steering. There was also a problem in that when the bending moment caused by the bending moment acts on the rack shaft and the rack shaft becomes deflected, the transmission efficiency is also affected.

This invention was made in view of the above-mentioned problems, and aims to provide an electric power steering device that is low in manufacturing cost, easy to assemble, and is not affected by the deflection of a rack shaft.

(Means for solving the problem) This invention involves fixing a pinion gear to a pinion shaft connected to a steering wheel, and meshing the pinion gear with rack teeth formed on a rack shaft connected to a steering wheel. At the same time, an output shaft of an electric motor is connected to the rack shaft, and the steering assist force outputted by the electric motor is transmitted to the steering wheels together with the manual steering force applied to the steering handle, thereby steering the steering wheels. In the electric power steering device, the electric motor is arranged coaxially with the rack shaft,
A first staggered gear is fixed to the output shaft of the electric motor, and a second staggered gear that meshes with the first staggered gear is fixed to the pinion shaft, and the steering assist output from the electric motor is provided. The gist is that the force is transmitted by said first staggered gear and said second staggered gear.

(Function) According to the electric power steering device of this invention, the manual steering force applied to the steering wheel is transmitted to the rack shaft via the pinion shaft, pinion gear, and rack teeth, and the steering assist force generated by the electric motor is is transmitted to the pinion shaft, that is, the rack shaft, through a first staggered gear fixed to the output shaft of the electric motor and a second staggered gear fixed to the pinion shaft and meshed with the first staggered gear. . Therefore, there is no need to perform high-precision machining on the rack shaft, reducing manufacturing costs, and the rack shaft can be easily assembled by simply meshing the rack teeth with the pinion gear. High reliability can be obtained without significantly affecting transmission efficiency.

(Example) Hereinafter, an example of this invention will be described based on the drawings.

The drawing is a sectional view of a main part of an embodiment of the electric power steering device according to the invention.

In the drawings, reference numeral 11 denotes a gear case supported by a vehicle body (not shown), and the gear case 11 is constructed by joining a plurality of members via seal members. Inside the gear case 11, a pinion shaft 12 is rotatably supported by bearings 13, 14, and 15, and is connected to a steering handle (not shown) via a steering shaft or the like on the right side of the drawing. pinion shaft 1
2, an upper shaft 12a and a lower shaft 12b are coupled by a torsion bar (not shown) so that they can be elastically rotated relative to each other, and the upper shaft 12a is connected to the steering handle, and the lower shaft 12b is connected to a pinion. gear 1
6 and a second staggered bevel gear 17 are fixedly installed. As will be described later, the pinion gear 16 meshes with rack teeth 18a formed on the rack shaft 18, and the second staggered bevel gear 17 meshes with the first staggered bevel gear 17 fixed to the output shaft 20 of the electric motor 19. bevel gear 21
They mesh with each other to form a staggered gear mechanism 22.

The rack shaft 18 is supported by the gear case 11 to be slidable in the axial direction via a metal bearing 28 between the left end in the figure, and has rack teeth 18a formed over an axial sliding range. This rack shaft 18
As is well known, the ends protruding from both left and right ends of the gear case 11 are connected to the knuckle arms of the steered wheels via a steering linkage or the like.

The electric motor 19 is disposed approximately in the center of the gear case 11 coaxially with the rack shaft 18. The electric motor 19 has a field magnet 29 fixed to the inner circumferential wall of the gear case 11, and a rotor 30 rotatably disposed between the field magnet 29 and the rack shaft 18. The rotor 30 is formed by fixing a laminated iron core 33 having a skew groove on the outer periphery of a substantially cylindrical output shaft 20 and a multi-wound armature winding 34. It is supported by the gear case 11 while being allowed to be displaced in the axial direction. The armature winding 34 of this rotor 30 is connected to the output shaft 2.
A control drive circuit 2, which will be described later, is connected via a commutator 35 fixedly attached to
6.

A first staggered bevel gear 21 is integrally provided on the output shaft 20 of the rotor 30 of this electric motor 19 at the right end in the figure, and as described above, this first staggered bevel gear 21 is fixed to the pinion shaft 12. It meshes with the provided second staggered bevel gear 17 so as to transmit power, thereby forming a staggered gear mechanism 22. These first and second staggered bevel gears 21, 17 are, as is well known, a hyperboloid of revolution.
A tooth trace is formed in the direction of the generatrix line with a part of the pitch plane as the pitch surface. This staggered gear mechanism 22 has a first
The staggered bevel gear 21 is biased by a spring 37 compressed between the flange portion 20a formed at the left end of the output shaft 20 in the figure and the inner ring of the bearing 31, and is turned into the second staggered bevel gear 17. The gears 17 and 21 come into elastic contact, and the bump between the gears 17 and 21 is eliminated.

Around the pinion shaft 12 of the gear case 11,
A torque sensor 23 is disposed coaxially with the pinion shaft 12 near the joint between the upper shaft 12a and the lower shaft 12b of the pinion shaft 12. The torque sensor 23 is
A substantially cylindrical movable iron core 2 into which a pinion shaft 12 is inserted
4, and a differential transformer 25 arranged around the movable iron core 24. The movable iron core 24 is connected to the upper shaft 12a and the lower shaft 12b of the pinion shaft 12 via cam mechanisms, respectively.
2a and the lower shaft 12b due to relative rotational displacement by the torsion bar, the lower shaft 12b is displaced in the axial direction. The differential transformer 25 is connected to a control drive circuit 26 and receives a pulse signal from the control drive circuit 26 and sends a signal representing the magnitude of the displacement of the movable iron core 24, that is, the direction of action of the steering torque, to the control drive circuit 26. Output. The control drive circuit 26 includes a microcomputer and the like, and is connected to a power source 27 such as a battery. This control drive circuit 26 includes the torque sensor 23 described above.
and the output signals of the vehicle speed sensor, etc., and control the current flowing from the power source 27 to the electric motor 19 based on the processing results.

Next, the operation of this embodiment will be explained.

This electric power steering device uses a control drive circuit 2 based on an output signal from a torque sensor 27 or the like.
6 controls the current applied to the electric motor 19 from the power source 27, and the electric motor 19 outputs a steering assist force according to the applied current. The steering assist force outputted by the electric motor 19 is transmitted to the first staggered bevel gear 21.
and a second staggered bevel gear 17 to the pinion shaft 12 via a staggered gear mechanism 22,
Together with the manual steering force transmitted from the steering wheel to the pinion shaft via the steering shaft, the pinion gear 16 acts on the rack shaft 18 via the rack teeth 18a, and the rack shaft 18 moves in the axial direction to rotate the steering wheel. steer. Therefore, the steering burden on the driver is reduced by the steering assist force output by the electric motor 19, and light steering becomes possible.

On the other hand, in this electric power steering device, an electric motor 19 is configured coaxially with a rack shaft 18, and an output shaft 20 of this electric motor 19 is connected to a pinion shaft 12 connected to a steering handle, and a relatively small staggered bevel gear mechanism. They are connected via 22. Therefore,
This electric power steering device does not need to be enlarged, especially in the radial direction of the rack shaft 18.
It can be easily installed in a vehicle with a narrow engine room, and there is no need to provide a separate pinion shaft for transmitting steering assist force around the rack shaft 18, and the number of parts can be reduced. In this electric power steering device, as described above, the output shaft 20 of the electric motor 19 is connected to the easy shaft 18.
Since the pinion gear 16 that meshes with the rack teeth 18a is connected to the fixed pinion shaft by the staggered gear mechanism 22, there is no need to perform high-precision machining such as the above-mentioned ball screw groove on the rack shaft 18. , its manufacturing cost is low, and the transmission efficiency is not affected by the deflection of the rack shaft 18.
Even if a bending moment is applied to the rack shaft 18 during steering, smooth operation can be maintained and high reliability can be obtained.

In the above embodiment, a skew bevel gear is shown as a hyper boloidal gear that connects the output shaft 20 of the electric motor 19 and the pinion shaft 12, but a hypoid gear is also used. Needless to say, it is possible to use

(Effects of the invention) As explained above, according to the electric power steering device according to the invention, the pinion shaft connected to the steering wheel is connected to the electric motor coaxially with the rack shaft by means of a staggered gear mechanism. A pinion gear connected to the output shaft and fixed to the pinion shaft is meshed with the rack teeth of the rack shaft to transmit manual steering force and steering assist force, which allows for miniaturization and a reduction in the number of parts. High-precision machining is not required, which reduces manufacturing costs, and furthermore, it is possible to prevent transmission efficiency from decreasing due to bending of the rack shaft, thereby achieving high reliability.

[Brief explanation of the drawing]

The drawing shows an elastic member of an electric power steering device according to an embodiment of the invention. 11... Gear case, 12... Pinion shaft, 1
6... Pinion gear, 17... Second staggered bevel gear, 18... Rack shaft, 18a... Rack tooth,
19...Electric motor, 20...Output shaft, 21...First
staggered bevel gears, 22... staggered gear mechanism.

Claims (1)

[Scope of utility model registration request] A pinion gear is fixed to a pinion shaft connected to a steering wheel, the pinion gear is meshed with rack teeth formed on a rack shaft connected to a steering wheel, and an output shaft of an electric motor is connected to the rack shaft. , an electric power steering device that transmits a steering assist force outputted by the electric motor to a steering wheel together with a manual steering force applied to the steering handle to steer the steering wheel, the electric motor being coaxial with the rack shaft; a first staggered gear is fixed to the output shaft of the electric motor, a second staggered gear that meshes with the first staggered gear is fixed to the pinion shaft, and the electric motor An electric power steering device characterized in that the steering assist force outputted by the steering assist force is transmitted by the first staggered gear and the second staggered gear.