JPS633881Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a ball screw type gear mechanism of a steering device.

FIG. 1 is a longitudinal cross-sectional view of a ball screw type gear mechanism of a conventional steering device, and FIG. 2 is a cross-sectional view thereof.

Generally, a ball screw type gear mechanism 1 of a steering device is mainly composed of a worm shaft 3, a ball nut 5, and a sector shaft 7.

That is, inside the gear housing 8, there is a worm shaft 3 connected to the steering shaft.
is rotatably supported via bearings 9 and 11. Bearings 9, 11 in the wormshaft 3
A threaded portion 13 is formed in between, and a ball nut 5 is screwed into this threaded portion 13 via a ball. Therefore, this ball nut 5 is movable in the axial direction of the wormshaft. Furthermore, a rack portion 15 is carved on the lower side surface of the ball nut 5 in the drawing.

Wormshaft 3 inside gear housing 8
A sector shaft 7 is disposed below the worm shaft 3 so as to be perpendicular to the worm shaft 3.
The sector shaft 7 is rotatably supported in a cantilevered manner by a bearing 17, and is formed with a sector gear 19 that meshes with the rack portion 15. This sector gear 19 is connected to the sector shaft 7
It is formed into a tapered shape whose diameter increases at the tip side, and the entire tooth width is engaged with the rack part 15. In addition, the sector shaft 7 is provided at the tip of the sector shaft 7.
A T-shaped groove 21 is carved in the vertical direction of the T-shaped groove 2.
1, a center adjusting screw 23, which will be described later, can be disposed therein.

A center end cover 25 that covers the tip of the sector shaft 7 is fixed to the gear housing 8 on the tip side of the sector shaft 7 with bolts 27 . Center end cover 25
A center adjusting screw 23 is screwed coaxially with the sector shaft 7 so as to be adjustable and movable in the axial direction. It can come into contact with the tip end surface 28 of the shaft 7. Therefore, by adjusting the center adjusting screw 23, the sector shaft 7 is moved in the direction of the bearing 17, and the gap between the rack portion 15 and the sector gear 19 is adjusted to an optimum state.

Therefore, the operating force from the steering shaft is applied to the ball nut 5 via the wormshaft 3.
When the ball nut 5 moves in the axial direction of the wormshaft 3, the sector shaft 7 is rotated in the circumferential direction due to the engagement between the rack part 15 and the sector gear 19. is transmitted to the wheels.

However, in such a conventional ball screw type gear mechanism, the sector gear 1 may be damaged due to wear of the bearing 17 or misalignment of the center end cover 25.
The gap between the rack part 9 and the rack part 15 becomes large. Alternatively, since the sector shaft 7 is supported in a cantilevered state, the rigidity of this gear mechanism is low, and therefore the sector shaft 7 is bent downward in the radial direction due to the load from the ball nut 5, and the sector gear 19 and the rack part 15 are A gap is created between the two. If this gap becomes large, not only will abnormal noise be generated, but also the contact pressure between the sector gear 19 and the rack portion 15 will be reduced, and therefore the frictional force generated between these 19 and 15 will be reduced, making it difficult for the vehicle to move straight. A problem arises in that the sense of direction is reduced and the steering stability performance is deteriorated.

This gap can also be adjusted using the center adjust screw 23, but in this case, it must be adjusted periodically, and it is impossible for the crew to do this, so it is difficult to handle. The above inconvenience cannot be avoided. In addition, in order to avoid deflection of the sector shaft 7, it is possible to support the tip of the sector shaft 7 or increase the rigidity by increasing the diameter of the sector shaft 7, but in these cases, parts Problems arise in that the number of points increases and the weight increases.

This idea was created in view of the above-mentioned conventional problems, and aims to reduce the gap between the vehicle sector gear and the rack part, especially when the vehicle is traveling straight, thereby improving steering stability when traveling straight. It is an object of the present invention to provide a ball screw type gear mechanism for a steering device that can reduce the clearance while maintaining good steering operability even when turning.

In order to achieve the above object, the ball screw type gear mechanism of the steering device according to the present invention has a gear housing and a worm shaft that is rotatably supported within the gear housing and connected to the steering shaft, through a ball. a ball nut having a rack portion formed on one side; a sector shaft rotatably supported within the gear housing, connected to a wheel, and having a sector gear screwable to the rack portion; In the ball screw type gear mechanism of the steering device, a pressing member is interposed between the sector gear rear part of the sector shaft and the gear housing and presses the rear part in the direction of the ball nut, and the pressing member is brought into contact with the rear part. The diameter of the circumferential surface of the rear surface portion is set to a maximum diameter at a rear surface position corresponding to a neutral steering position of the sector gear, and decreases in diameter over a constant angle range on both sides as it moves away from the position. do.

With this structure, the sector gear is constantly pressed in the direction of the ball nut by the pressing member, and the sector gear and the rack are engaged with each other with zero gap. In particular, since the circumferential diameter of the rear surface to which the pressing force is applied is the maximum diameter at the position corresponding to the straight-ahead running state, the above-mentioned pressing force is maximum in the straight-ahead running state, and the sector gear and rack part Sufficient frictional force is ensured. This provides a good direct feeling and improves steering stability when traveling straight ahead.

On the other hand, when turning left and right, the circumferential diameter of the corresponding back surface is reduced, so the pressing force is alleviated. This moderately reduces the frictional force between the sector gear and the rack.
The steering operability of the vehicle is maintained satisfactorily.

Hereinafter, embodiments of this invention will be described with reference to the drawings.

FIG. 3 is a longitudinal sectional view showing an embodiment of the ball screw type gear mechanism of the steering device according to this invention;
FIG. 4 is a cross-sectional view of the same embodiment, and the same parts as in the conventional example are designated by the same reference numerals and the explanation thereof will be omitted.

Ball screw type gear mechanism 30 of steering device
In this case, the sector gear rear surface portion 33 of the sector shaft 31 is formed in an elliptical shape. That is, both side surfaces of the conventional circular sector gear rear surface section as shown by the two-dot chain line in the figure are cut into a curved shape to form a side surface section 34A with a small radius, and the tip end 34B of the sector gear rear surface section 33 is formed into an elliptical long section. formed in line with the axis.

A dogleg-shaped leaf spring 35 is interposed between the gear box 8 and the sector gear rear surface 33 as a pressing member. This leaf spring 35 is in a biased state and abuts against the sector gear back surface 33, pressing the sector shaft 31 toward the ball nut 5.

Therefore, even if there is wear between the sector gear 19 and the rack part 15 or wear of the bearing 17, the biasing force of the leaf spring 35 will always keep the gap between the sector gear 19 and the rack part 15 to zero, and the gap between these two parts will be maintained at zero. The contact pressure between 19 and 15 is maintained at an optimum level.
Therefore, the frictional force between the sector shaft 31 and the ball nut 5 becomes large, resulting in a good direct feeling.
Steering stability can be improved.

Further, the sector gear rear surface 33 is formed in an elliptical shape, and the leaf spring 35 comes into contact with the tip 34B of the sector gear rear surface when the vehicle is running straight.
A large biasing force acts on the sector shaft 31, increasing the frictional force between the sector gear 19 and the rack portion 15, and improving the running stability of the vehicle when the vehicle is running straight.

Furthermore, when the vehicle is steered, the leaf spring 35 comes into contact with the rear surface portion 34A of the sector gear rear surface, so that the biasing force from the leaf spring 35 against the sector shaft 31 is relatively small, so that the sector gear 19
The frictional force between the rack portion 15 and the rack portion 15 is also relatively small, and the steering operability of the vehicle can be improved.

FIG. 5 is a longitudinal cross-sectional view showing another embodiment of the ball screw type gear mechanism of the steering device according to this invention, and FIG. 6 is a cross-sectional view of the same embodiment, showing the same parts as the first embodiment. are given the same reference numerals and their explanation will be omitted.

Ball screw gear mechanism 40 of steering device
A cylindrical protrusion 43 is formed at a position of the gear housing 41 facing the sector gear back surface 33 . A sleeve 47 having a roller 45 is fitted inside the protrusion 43 so as to be slidable in the axial direction of the protrusion 43, and a guide 49 is screwed onto the tip of the protrusion 43. A compression coil spring 51 is interposed between the sleeve 47 and the guide portion 49 in a biased state, and the roller 45
is brought into contact with the sector gear back surface 33 to apply a pressing force to the sector shaft 31 in the direction of the ball nut 5.

Therefore, according to this invention, not only can the same effects as those of the first embodiment be obtained, but also the roller 45 rotatably supported by the sleeve 47 comes into contact with the sector gear back surface 33. Therefore, these sector gear rear parts 33
The frictional resistance between the roller 45 and the roller 45 can be reduced, and steering operability can be improved.

FIG. 7 is a longitudinal cross-sectional view showing still another embodiment of the ball screw type gear mechanism of the steering device according to this invention, and FIG. 8 is a cross-sectional view of the same embodiment, showing the same parts as the second embodiment. are given the same reference numerals and their explanation will be omitted.

In the ball screw type gear mechanism 60 of this steering device, a protrusion 63 substantially similar to the protrusion 43 is formed in the gear housing 61, but the protrusion 63 has an opening near its inner tip. A cap portion 65 is integrally formed.

A sleeve 47 that rotatably supports the roller 45 is disposed inside the protruding portion 63 and inside the cap portion 65, and forms a hydraulic chamber 66 with the cap portion 65. Further, an O-ring 67 is provided at a position inside the protrusion 63 that contacts the sleeve 47.
is fitted to keep the hydraulic chamber 66 in a sealed state.
Furthermore, a guide portion 68 is screwed onto the outside of the cap portion 65 inside the protrusion portion 63. A through hole 69 is bored in this guide portion 68, and this through hole 6
9, engine oil is forced into the hydraulic chamber 66.

Therefore, the pressure from the hydraulic chamber 66 causes the roller 45 to come into contact with the sector gear rear surface 33 in a pressed state, and a pressing force in the direction of the ball nut 5 acts on the sector shaft 31, thereby closing the gap between the sector gear 19 and the rack part 15. Let be zero.

According to the above embodiment, the same effects as in the second embodiment can be obtained. Furthermore, although engine oil is used to press the sector shaft 31, the hydraulic pressure of this engine oil increases as the engine speeds up, i.e., as the engine rotates at higher speeds. You can get it.

As described above, the ball screw gear mechanism of the steering device according to this invention can reduce the gap between the sector gear and the rack portion, and can improve steering stability when traveling straight by reducing the gap particularly when traveling straight. It is also possible to reduce the gap while maintaining good steering operability even when traveling in a corner, and has the effect of maintaining a good steering feel throughout the entire steering range.

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional view showing a ball screw type gear mechanism of a conventional steering device, Fig. 2 is a cross sectional view thereof, and Fig. 3 is an example of a ball screw type gear mechanism of a steering device according to this invention. FIG. 4 is a cross-sectional view of the same embodiment, FIG. 5 is a vertical cross-sectional view of another embodiment of the invention, FIG. 6 is a cross-sectional view of another embodiment, and FIG. The figure is a longitudinal cross-sectional view showing still another embodiment of the invention, and FIG. 8 is a cross-sectional view of still another embodiment of the same. 3...Wormshaft, 5...Ball nut, 8...Gear housing, 15...Rack part,
19... Sector gear, 30... Gear mechanism, 31...
...Sector shaft, 33...Sector gear rear part,
35... Leaf spring, 40... Gear mechanism, 45... Roller, 51... Compression coil spring, 60... Gear mechanism, 66... Hydraulic chamber.

Claims (1)

[Scope of utility model registration request] a gear housing, a ball nut which is screwed through a ball to a wormshaft which is rotatably supported within the gear housing and connected to the steering shaft, and which has a rack portion formed on one side thereof; A ball screw type gear mechanism of a steering device including a sector shaft connected to a wheel and having a sector gear that can be screwed into the rack part, wherein the sector gear rear part of the sector shaft and the gear housing are connected to each other. A pressing member that presses the rear surface in the direction of the ball nut is provided in between, and the circumferential diameter of the rear surface is set to a maximum at the rear surface corresponding to the neutral steering position of the sector gear. 1. A ball screw type gear mechanism for a steering device, characterized in that the diameter is narrowed over a certain angular range on both sides as it moves away from the position.