JPH0423737Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to a steering gear device mainly applied to automobiles.

(Prior Art) A conventional steering gear box will be explained with reference to FIGS. 5 and 6. A is a pinion shaft connected to a steering wheel via a steering joint (not shown), B is an oil seal,
c is a top cover, d is a lockite, e and f are bearings and needle bearings that rotatably support the pinion shaft a in the rack housing g, and h is a rack _h1 that meshes with the pinion _a1 provided on the pinion shaft a. i is a rack support arranged on the back side of the rack bar h, l is a rack support cover, k is a rock knight that fixes the rack support cover l to the rack housing g, and j is the rack support cover l and The springs m and m interposed between the rack support i and the left and right tie rods connected to the rack bar h rotate the pinion shaft a around its axis via the steering handle and control its movement. The pinion _a1 of the pinion shaft a and the rack bar h meshing with it change the movement in the Z direction, and the movement of the rack bar h is further transmitted to the left and right wheels via tie rods m, m to move each wheel in a predetermined direction. It is designed to be steered by

(Problems to be solved by the invention) In the steering gear device shown in FIGS. 5 and 6,
During steering, reaction forces act not only in the Z direction but also in _the X and Y directions on the rack bar h due to the meshing of the rack h1 and pinion a1, and the transmission efficiency of the rack _{h1 and} pinion _a1 (steering gear) decreases. It decreases due to tooth meshing, elastic deformation of each member, friction, etc.
One of the dominant factors that reduce the transmission efficiency is the sliding resistance between the rack bar h and the rack support i due to the component force in the Y direction. Now, assuming that the sliding friction coefficient between the rack bar h and the rack support i is μ ₈₉ and the component force in the Y direction is F _Y , the sliding friction force F ₈₉ in this part is expressed by the following equation.

F ₈₉ = μ ₈₉ ×F _Y When the rack bar h and the rack support i are in contact as described above, the steering force and the steering angle have the relationship shown in A in Fig. 3, and as a result, the rack bar h The sliding friction force (steering reaction force of the entire steering system) between the rack support i and the rack support i is as shown in A in FIG.

On the other hand, the characteristics required of a steering gear device are () light steering force when steering at a fixed angle and at large steering angles; () In order to reduce the self-excited vibration (shimmy) of the steering wheel due to the tire excitation force, the steering wheel should have an appropriate amount of damping force, such as friction near the neutral position. () A tight feeling near the neutral position is more desirable than responsiveness during high-speed steering, and the steering force should not be too light near the neutral position. etc. can be mentioned. However, the conventional steering gear devices shown in FIGS. 5 and 6 have the following drawbacks, as is clear from the characteristics shown in A in FIGS. 3 and 4. () In order to reduce the steering force when turning stationary and at large steering angles, if the friction coefficient μ ₈₉ is lowered, the damping force near the neutral position will also decrease relatively, causing shimmy and , the feeling of responsiveness during high-speed steering is lost, and responsiveness deteriorates. ()
Conversely, in order to reduce shimmy and improve responsiveness during high-speed steering, increasing the friction coefficient μ ₈₉ or the biasing force of spring j increases the steering force during stationary steering and large steering angles. If the friction coefficient is lowered to reduce the steering force in this way, problems such as shimmy will occur, and if the friction coefficient is increased to reduce the shimmy, the steering force will increase. , In the steering gear device shown in Figure 6,
Appropriate frictional force is provided at the expense of reducing steering force.

(Means for Solving the Problems) The present invention addresses the above problems, and includes a pinion shaft connected to a housing and a steering handle, rotatably supported within the housing, and having a pinion formed therein. , a rack bar that is slidably supported within the housing and has a rack formed on one surface that meshes with the pinion;
a rack support member slidably disposed within the housing and biased by a spring member to press the back surface of the rack bar; a bearing rotatably disposed in the housing facing the back surface of the rack bar; When the rack bar is in the steering range, the bearing bar comes into contact with the rear surface of the rack bar, and when the rack bar is near neutral, the bearing bar is in contact with the rear surface of the rack bar. A recessed portion having a predetermined level difference from the steering range is provided near the neutral position on the rear surface of the opposing rack bar, and a gap between the bearing and the recessed portion when the bearing faces the recessed portion is set to be smaller than the predetermined level difference. The object of the present invention is to provide an improved steering gear box that can provide a favorable steering feeling depending on the steering condition while maintaining good meshing between the rack and pinion. At the point.

Next, the steering gear box of the present invention will be explained with reference to an embodiment shown in FIGS. 1 and 2. 1 is a pinion shaft, 1a is a pinion, 2 is an oil seal, 3 is a top cover, 4 is a lock nut,
5 is a bearing, 6 is a needle bearing, 7 is a rack housing, 8 is a rack bar, 8a is a rack, 9 is a rack support, 10 is a shaft (bearing support member), 11 is a bearing, 12 is a spring, 13 is a lock nut, 14 is a A rack support cover 15 is a recess provided on the rear surface of the rack bar 8. Further, δ is the clearance between the rack support 9 and the rack support cover 14, δ ₁
is the depth of the recess 15, _δ2 is the amount of overlap between the bearing 11 and the part other than the recess 15 when the rack bar 8 is near the neutral position, and the amount of overlap _δ2 is the above clearance (amount of movement of the bearing 11). The depth δ ₁ of the recess 15 is set to be larger than the lapping amount δ ₂ . Also rack bar 8
The sliding friction coefficient in the sliding friction area between the rack bar 8 and the bearing 11 is set to μ ₈₉ (approximately 0.1 to 0.2), and the rolling friction coefficient in the rolling friction area between the rack bar 8 and the bearing 11 is set to μ ₈₁₁ (approximately 0.04 or less). are doing. That is, the materials and finished surfaces of the friction areas of each of the above-mentioned parts are selected to obtain the above-mentioned coefficient of friction. Further, a pinion shaft 1 connected to a steering handle via a steering joint (not shown) is rotatably supported by a rack housing 7 via a bearing 5 and a needle bearing 6, and the upper part of the rack housing 7 is connected to an oil seal 2. The bearing 11 is rotatably supported by the rack support 9 via the shaft 10, the rack bar 8 meshing with the pinion of the pinion shaft 1 is supported by the rack support 9 so as to be movable in the axial direction, and the spring 12 is A rack bar 8 is pressed against the pinion of the pinion shaft 1 via a rack support 9.

The recess 15 is the cylindrical back surface 8b of the rack bar 8.
Among them, it is provided in a part corresponding to the neutral area N,
Flat portions 8b' corresponding to the steering areas on both sides protrude toward the bearing 11 by _δ1 . Further, a bearing support 16 is inserted into the space formed by the rack support 9 and the rack support cover 14, and the shaft 10 is placed on the bearing support 16.
Through a rolling bearing, for example a ball bearing 11
is supported. The center line of the shaft 10 is parallel to the center line of the pinion shaft 1. Further, a spring 17 is interposed between the bearing support 16 and the rack support 9. As is clear from FIG. 4, when the rack bar 8 is in the neutral position, there is a gap in the direction perpendicular to the axis of the rack bar 8 ( There is a wrap amount of δ ₂ in the Y direction). Further, the above-mentioned δ ₁ and δ ₂ are set to δ ₁ > δ ₂ , and when the rack bar 8 is in the neutral position, the recess 15 in the neutral area on the back side and the ball bearing 1
1, a small gap of δ ₁ −δ ₂ is formed.

(Function) Next, the function of the steering gear device shown in FIGS. 1 and 2 will be explained. As already mentioned, the fifth
In the conventional steering gear device shown in Fig. 6, during steering, reaction forces act on the rack bar h not only in the Z direction but also in the X and Y directions due to the meshing of the rack _h1 and pinion _a1 , _which The transmission efficiency of a ₁ (steering gear) decreases due to tooth meshing, elastic deformation of each member, friction, etc., but one of the dominant factors that decreases transmission efficiency is the component force in the Y direction mentioned above. There is a sliding resistance between the rack bar h and the rack support i. Now Rack Bar h
Letting μ ₈₉ be the sliding friction coefficient between and rack support i, and F _Y be the component force in the Y direction, the sliding friction force F ₈₉ in this part is expressed by the following equation.

F ₈₉ = μ ₈₉ ×F _Y When the rack bar h and the rack support i are in contact as described above, the steering force and the steering angle have the relationship shown in A in Fig. 3, and as a result, the rack bar h The sliding friction force (steering reaction force of the entire steering system) between the rack support i and the rack support i is as shown in A in FIG.

However, in the present invention, when the rack bar 8 is near the neutral position, a small gap of δ ₁ - δ ₂ is formed between the recess 15 of the rack bar 8 and the bearing 11, and the rack bar 8 is in contact only with the rack support 9. Then, the sliding friction force is the same as before, F ₈₉ = μ ₈₉ ×
It becomes F _Y + F ₀ . Here, F ₀ is the frictional force due to the spring force P ₀ and is expressed as F ₀ =μ ₈₉ ×P ₀ . During steering, the rack bar 8 moves in the Z direction, and the bearing 11 moves to the second position relative to the rack bar 8.
Move relative to the position indicated by the two-dot chain line in the figure. As a result, the flat portion 8'b of the rack bar 8 comes into contact with the bearing 11, and the rack support 9 also comes into contact with the rack bar 8. Therefore, the frictional force during steering is a combination of the sliding frictional force and the rolling frictional force. This combined frictional force is expressed by the following equation.

F′ ₈₉ = μ ₈₉ ×P′ ₀ F ₈₁₁ = μ ₈₁₁ ×F _Y However, since F′ ₈₉ changes by only a displacement of δ ₂ with respect to F ₀ , it is possible to set F′ ₈₉ ≒ F ₀ . can. As a result of the above, the total frictional force becomes F=F' ₈₉ +F ₈₁₁ ≈F ₀ +μ ₈₁₁ ×F _Y , and the characteristics shown by B in FIGS. 3 and 4 are obtained.

Further, in this embodiment, since the rack support 9 and the rolling bearing, for example, the ball bearing 11, are independent, during assembly, the rack support cover 14 is held until the outer race 11a of the bearing 11 comes into contact with the recess 15 in the neutral area N of the rack bar. By screwing in and then unscrewing by a certain amount, the wrap amount δ ₂ can be ensured with high accuracy. Therefore, if the step δ ₁ of the recess 15 is machined with high precision, the accuracy of the related components can be easily controlled without being affected by the manufacturing accuracy of the rack support 9, pinion shaft 1, bearing support 16, and rack support cover 14. There are advantages to being able to do so. Furthermore, as long as the condition δ ₁ - ΔW > δ ₂ can be secured for the amount of wear ΔW of the flat surface 8'b of the rack bar 8 and the ball bearing 11, δ ₂ can be adjusted and δ ₂ can be kept constant. be able to. Furthermore, during steering, the center of meshing between the rack bar 8 and the pinion shaft 1 moves toward the pinion side by the amount of δ ₂ described above, so there is an advantage that the steering force is reduced, albeit slightly.

(Effect of the invention) As described above, in the steering gear device of the present invention, when the rack bar is in the steering range, the bearing bar comes into contact with the back of the rack bar, and when the rack bar is near neutral, the bearing comes into contact with the back of the rack bar. In order to prevent this, a recess having a predetermined level difference from the steering range is provided near the neutral position on the rear surface of the rack bar facing the bearing, and a gap between the bearing and the recess when the bearing faces the recess is set to Since it is set smaller than the level difference, the bearing does not come into contact with the back of the rack bar when the steering wheel is near neutral.

Therefore, only the rack support member presses the back surface of the rack bar due to the biasing force of the spring member, and sliding friction acts on the contact surface between the rack support member and the rack bar, increasing the frictional force and causing the sliding of the rack bar to increase. Dynamic resistance increases.

Therefore, the feeling of stability and responsiveness of the steering wheel is improved, and the responsiveness during high-speed steering can also be improved. In addition, it is possible to reduce shimmy near the neutral position of the steering wheel.

On the other hand, when the steering wheel is turned so that the bearing faces the steering range on the back of the rack bar (no longer facing the recess on the back of the rack bar), the bearing comes into contact with the back of the rack bar, causing rolling friction. As a result, the sliding resistance of the rack bar becomes smaller.

Therefore, the steering force can be reduced within a predetermined steering range, and a smooth operation feeling can be obtained.

As described above, according to the present invention, in the vicinity of the neutral position of the steering wheel, only the sliding friction due to the rack support member is applied to the rack bar to improve the feeling of holding the steering wheel, and in the steering range of the steering wheel, the rolling friction due to the bearing is applied to the rack bar. It is possible to obtain a smooth steering feeling by effectively utilizing This has the advantage of providing a favorable steering feel.

In addition, the above-mentioned change in the sliding resistance of the rack bar is achieved by providing a recess near the neutral position on the back of the rack bar, so the steering force can be reliably changed depending on the steering angle range of the steering wheel. This has the advantage of ensuring that an appropriate steering feel is obtained.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal side view showing an embodiment of a steering gear device according to the present invention, Fig. 2 is an enlarged plan view taken along the arrow line in Fig. 1, and Fig. 3 is a graph showing the relationship between steering force and steering angle. FIG. 4 is an explanatory diagram showing the relationship, FIG. 4 is an explanatory diagram showing the frictional force of the rack bar, FIG. 5 is a perspective view schematically showing a conventional steering gear device, and FIG. 6 is a longitudinal sectional side view showing its details. 1...Pinion shaft, 7...Housing,
8... Rack bar, 8a... Rack, 9... Rack support member, 11... Bearing, 12...
Spring member, 15... recess, δ ₁ -δ ₂ ... gap.

Claims (1)

[Scope of utility model registration request] a housing, a pinion shaft connected to a steering handle and rotatably supported within the housing and having a pinion formed thereon; a pinion shaft that is slidably supported within the housing and has a rack formed on one surface that meshes with the pinion; a rack support member slidably disposed within the housing and biased by a spring member to press the rear surface of the rack bar; a rack support member rotatably disposed within the housing opposite the rear surface of the rack bar; When the rack bar is in the steering range, the bearing bar contacts the rear surface of the rack bar, and when the rack bar is near neutral, the bearing bar does not contact the rear surface of the rack bar. A recess having a predetermined level difference from the steering range is provided near the neutral position on the rear surface of the rack bar facing the bearing, and when the bearing faces the recess, the gap between the bearing and the recess is set to be larger than the predetermined level difference. A steering gear device characterized by a small setting.