JPH0274467A - Power steering device - Google Patents

Abstract

PURPOSE:To prevent the hitting noise and a vibration and to improve the response by combining a worm shaft which is divided into two in the axial direction through a torsion bar or the like, and gearing the worm shafts to a worm wheel with the torsion bar or the like in the twisted condition. CONSTITUTION:At the lower end of a torsion bar 20, an output shaft 3 to which the driving force of a motor 5 for auxiliary steering is delivered is connected coaxially, and the output shaft 3 is connected to the pinion shaft of a rack- pinion type motion-converting mechanism. In such a system, worm shafts 22a and 22b divided into two parts in the axial direction and connected coaxially through a torsion bar 22c are held by bearings 24 and 25, on the outer periphery of a worm wheel 23 set outside the output shaft 3 through a key 21, and the rotary shaft of the motor 5 is connected to the worm shaft 22b. The worm shafts 22a and 22b are geared to the worm wheel 23 with the torsion bar 22c twisted, that is, the both shafts are rotated a little in the opposite directions.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a power steering device installed in an automobile.

[Prior Art] A power steering device for an automobile, particularly an electric power steering device, has been developed in which a motor for assisting steering is mounted on a column shaft in a vehicle interior. This is to eliminate the difficulty of securing space and maintenance when installing the motor and transmission mechanism in the engine room.In such devices, a power transmission mechanism consisting of a worm and a worm wheel is used, and the worm wheel is attached to a column. There is a structure in which the worm is attached to a shaft and engaged with a worm attached to the drive shaft of the motor.

(Problems to be Solved by the Invention) By the way, in such a steering device, opposing teeth contact each other due to backlash at the meshing portion of the worm and the worm wheel, causing hammering sounds and vibrations, etc. There is a problem in that responsiveness is reduced and a comfortable steering feeling cannot be obtained.

The present invention has been made in view of the above circumstances, and provides a power steering device that prevents the occurrence of hammering sounds and vibrations at the meshing portion of the worm and the worm wheel, and provides a comfortable steering feeling with excellent responsiveness. For the purpose of providing.

[Means to solve the problem]

The steering device according to the present invention is a power steering device in which a worm shaft rotated by a steering assist motor is engaged with a worm wheel attached to a steering shaft to which steering wheels are interlocked. A connecting means is provided which divides either the worm wheel or the worm shaft into two in the axial direction and coaxially connects the two divided worm foils or the worm shaft with resilience to resist twisting. The worm wheel or the worm shaft connected by the connecting means is characterized in that they are twisted coaxially and meshed with the worm shaft or the worm wheel, respectively.

[Effect]

Either the worm wheel or the worm shaft is divided into two parts in the axial direction and connected by a connecting means.

The connected wormwheels or wormshafts are coaxially twisted and meshed with the wormshaft or wormwheel, respectively. Then, on the connected worm wheel or worm shaft, a force is applied to each of the two halves to rotate in opposite circumferential directions against twisting, and each tooth acts in the direction of rotation of the worm shaft or worm wheel. It is closely meshed with the teeth of the worm shaft or worm wheel in the direction of

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof. FIG. 1 shows a power steering device (hereinafter referred to as
FIG. 2 is a partially cutaway front view showing the configuration of a device of the present invention. In the figure, l is a steering wheel, and the steering wheel 1 is an input shaft 2.
It is connected coaxially to the upper end of the. The lower end of the input shaft 2 is coaxially connected to the upper end of a torsion bar 20 (see Figures 2 and 3), and the torsion bar 20 is inside the housing 4 together with the torque sensor 15 (see Figure 3). It is located in

An output shaft 3 to which the driving force of a steering assist motor 5 is transmitted is coaxially connected to the lower end of the torsion bar 20. The output shaft 3 is connected to a pinion shaft 8 of a rack-binion type motion conversion mechanism 13 via an intermediate shaft 7 having universal joints 7a, 7b at both ends thereof.

Reference numeral 9 in the figure denotes a rack shaft case that is cylindrical and fixed to the vehicle body with its longitudinal direction being the left-right direction. is interpolated.

The lower end of the pinion shaft 8 is inserted into a pinion case 14 which is located near one side of the rack shaft case 9 and communicated with each other, and is formed on the circumferential surface of the pinion shaft 8. The pinion teeth are meshed with rack teeth (both not shown) formed in the axial direction of the rack shaft 10.

As the pinion shaft 8 rotates, the rack shaft 10 moves in its axial direction in response to changes in the meshing position between the nion teeth and the rack teeth.

The left and right ends of the rack shaft 10 protrude from the right and left ends of the rack shaft case 9 by a suitable length, and each is connected to a ball joint 11.
Left and right wheels (not shown) are steered via a, llb and link members 12a, 12b.

FIG. 2 is a sectional view taken along the line ■--■ in FIG. 1, and shows a first embodiment of the main part of the apparatus of the present invention. The lower end of the torsion bar 20 disposed in the housing 4 is fitted into an opening provided at the axial center position of the output shaft 3, and is locked by a pin 20a (see FIG. 3). , a worm wheel 23 is connected to the output shaft 3 via a key 21.
is fitted externally.

The outer periphery of the worm wheel 23 is divided into two in the axial direction,
The worm shafts 22a and 22b, which are coaxially connected via the torsion bar 22c serving as the connection means, are supported by bearings 24 and 25 so that their axes are positioned orthogonal to the axis of the worm wheel 23 and meshed. The worm shaft 22b is connected to the rotating shaft of the motor 5. Here, the worm shafts 22a and 22b are engaged with the worm wheel 23 with the torsion bar 22c twisted, that is, each shaft slightly rotated in opposite directions.

The motor 5 is connected to the control section 6 via a drive circuit (not shown), and is driven to rotate forward or backward according to an output signal from the control section 6.

In the control unit 6, the torque associated with the rotational operation of the steering wheel 1 is detected by the torque sensor 15 using a potentiometer, for example, as a difference between the amount of rotation of the input shaft 2 and the output shaft 3 based on the torsion of the torsion bar 20. Detected and given.

The control unit 6 recognizes the direction and magnitude of the torque acting on the input shaft 2 based on the human power signal from the torque sensor 15, and when a torque of a predetermined value or more is applied to the input shaft 2, the control unit 6 recognizes the direction and magnitude of the torque acting on the input shaft 2 based on the human power signal from the torque sensor 15. A signal is issued to the motor 5 to cause it to rotate forward or reverse. Therefore, by the operation of this control section 6, the rotational force of the motor 5 is applied to the worm shaft 22a according to the direction and magnitude of the torque acting on the input shaft 2.

22b and the worm wheel 23, and the movement conversion mechanism 13 is operated through the intermediate shaft 7, so that the rack shaft 10 moves in the shaft length direction. As a result, the left and right wheels are steered as described above. It will be done.

Now, since the worm shafts 22a and 22b are engaged with the worm wheel 23 with the torsion bar 22c twisted, the worm shafts 22a and 22b each have a force that tries to cancel the twist of the torsion bar 22c. They are added in opposite circumferential directions. In other words, this force causes the worm shaft 22a to rotate in one direction of the worm wheel 23, and the worm shaft 22b to rotate in one direction of the worm wheel 23.
In the other direction of rotation of the worm wheel, each tooth is biased so as to closely mesh with the teeth of the worm wheel without any gaps.

As a result, no matter which direction the drive shaft of the motor 5 is rotated, the worm shafts 22a, 22b and the worm wheel 23
No hitting noise or vibrations will occur at the meshing part with the
Steering operations are performed with good responsiveness.

Next, a second embodiment of the main part of the device of the present invention will be described. FIG. 3 is a sectional view taken along the line ■-■ in FIG. 1, and while the first embodiment described above showed a configuration in which the worm shaft is divided into two, a configuration in which the worm wheel is divided into two is shown here.

As shown in the enlarged cross-sectional view of FIG. 4, the worm wheel externally fitted onto the output shaft 3 in the housing 4 includes worm wheels 23a and 23b divided into two in the axial direction, and each worm foil has two worm wheels 23a and 23b. A center hole having a larger diameter than the outer diameter of the fitting portion of the output shaft 3 is formed in the shaft center, and is inserted between the center hole and the outer peripheral surface of the output shaft 3, and the outer diameter of the output shaft 3 and Torsion tube 2 having fitting holes 23d with approximately equal inner diameters
They are coaxially connected via 3c. One worm wheel 23b is attached to a flange 3 formed on the output shaft 3.
0 with a bolt 31. 23e and 2
3f is a bottle and a bolt for preventing the worm wheels 23a and 23b from rotating relative to the torsion tube 23c, respectively.

Now, the worm foil 23a is configured as described above.

23b, the torsion cylinder 23c is twisted;
That is, each worm wheel is meshed with the worm shaft 22 while slightly rotated in opposite directions.

As a result, the worm shaft 2 in the first embodiment described above
2a and 22b, here a force acts on the worm wheels 23a and 23b to cancel the twist of the torsion cylinder 23c, and the worm wheel 23a moves in one direction of rotation of the worm shaft 22, and the worm wheel 23b
are similarly urged in the other direction of rotation of the worm shaft 22, so that the teeth of each worm wheel closely mesh with the teeth of the worm shaft 22 in the respective rotation directions of the worm shaft 22. As a result, the steering operation is performed with good responsiveness without producing any hammering sounds or vibrations.

In this embodiment, the worm shafts or worm foils are connected using a torsion bar or a torsion tube to provide resilience against twisting, but the present invention is not limited to this. For example, in the case of worm foils, the worm foils are connected to each other by bottles, etc., and the connecting parts are made of rubber,
Alternatively, an elastic material such as a spring may be inserted.

〔effect〕

As described above, in the steering device according to the present invention, either the worm wheel or the worm shaft is divided into two parts in the axial direction and connected through a torsion bar, etc., and the torsion bar or the like is twisted to separate the parts into two parts. The worm wheel or worm shaft is meshed with the worm shaft or the worm wheel, respectively. For example, when using a worm shaft divided into two, each of the two divided worm shafts is rotated in opposite circumferential directions by the force that resists the twisting of the torsion bar, and the teeth of each worm shaft are rotated separately. It is biased in each direction of rotation of the worm wheel and tightly meshes with the teeth of the worm wheel, so that no matter which direction the worm shaft is rotated, the teeth of one of the worm shafts will correspond to the rotation. Since it is closely meshed with the teeth of the worm wheel in both directions, there is no backlash and no hammering noise or vibration occurs. As a result, the present invention has excellent effects such as no reduction in steering responsiveness and a good steering feel.

[Brief explanation of the drawing]

FIG. 1 is a partially broken pressure surface view showing the structure of the steering device according to the present invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. The figure is a sectional view taken along the line ■--■ of FIG. 1, also showing the second embodiment, and FIG. 4 is a partially enlarged sectional view of FIG. 3. 2...Input shaft 3...Output shaft 5...Motor 2
2a, 22b... Worm shaft 22c... Torsion bar 23a, 23b... Worm foil 23
c...Torsion cylinder frame Applicant Koyo Seiko Co., Ltd. Agent Patent attorney Tokio Kawano

Claims (1)

[Scope of Claims] 1. A power steering device in which a worm shaft rotated by a steering assist motor is meshed with a worm wheel attached to a steering shaft to which steering wheels are interlocked, comprising: A connecting means is provided which divides either the worm wheel or the worm shaft into two in the axial direction, and connects the divided worm wheel or the worm shaft coaxially while imparting restorability to resist twisting, and the connecting means is provided. A power steering device characterized in that a worm wheel or a worm shaft connected by a means is meshed with the worm shaft or the worm wheel, respectively, with the worm wheel or the worm shaft twisted coaxially.