JPS628862A - Steering device - Google Patents

Abstract

PURPOSE:To level off the characteristics of a charge of a preload torque at the neutral point of the steering by forming a corrected gear face either on the addendum side of a sector gear or on the addendum side of a rack gear on a basis of an intermeshing line when the steering is in a neutral position. CONSTITUTION:Sector gear teeth 31 through 34 of a sector gear 30 are formed in such a way that the amount of addendum modification is increased from the end surface A of a small pitch diameter to the end surface B of a large pitch diameter. And sector gear faces 32a and 33a which face each other, of a pair of sector gears 32 and 33 come in contact with rack gear faces 23a and 23b of a center rack gear 23, which is meshed with the above mentioned sector gear, at an intermeshing line P when the steering is in a neutral position. A corrected gear face S is formed either on the addendum side from the intermeshing line P of the sector gear faces 32a and 33a or on the addendum side from the intermeshing line P of the rack gear faces 23a and 23b, in such a way that the amount of correction is increased in proportion to the distance from the intermeshing line toward the direction that each face of gear teeth is swelled up.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a steering wheel of a type that is provided with a conical sector gear and that moves this sector gear in the axial direction to adjust the backlash between it and the rack. Regarding equipment.

[Prior art]

As shown in FIGS. 3 and 4, for example, this type of steering device includes a rack 20 that is slidably supported by a casing 10 and moves back and forth in response to rotation of a steering shaft 15, and The casing 10 is perpendicular to the moving direction of
a sector gear 3 having an output shaft 13 pivotally supported by the output shaft 13 and four sector teeth 31 to 34 that are integrally provided on the output shaft 13 and mesh with the rack teeth 21 to 25 of the rack 20;
0, and the sector teeth 31 to 34 have tooth tips in the shape of a fan-shaped cone and are cut by gradually increasing the amount of displacement from the small diameter end A toward the large diameter end B. In this type of steering device, the rack tooth 2 located in the center
A negative puff crush is applied between the pair of sector teeth 32 and 33 meshing with the center rack tooth 23, and a positive backlash is applied between the other rack teeth and the sector teeth.
Both sectors! 32. A preload torque is applied to the steering wheel near the neutral steering position where it meshes with 33 to stabilize the steering wheel.

[Problem that the invention seeks to solve]

In such a steering device, since the amount of displacement of the sector teeth 32 and 33 differs depending on the location, the meshing line P with the rack teeth 23
As shown in FIG. 1, the tooth tip surface of the rack 20 and the sector 6
It is inclined with respect to the intersection line R with 32. Therefore, the length of the mesh line P at the steering neutral position is L, but the length of the mesh line P at the steering neutral position is
Since the length of the mesh line becomes shorter as the rotation angle of the sector gear 30 rotates from the neutral steering position, the change characteristics of the preload torque with respect to the rotation angle of the sector gear 30 change from the neutral steering position as shown by the two-dot chain line T1 in FIG. It becomes a mountain shape with the top. However, if there is a machining error in the sector teeth 32, 33 and the rack tooth 23, or if there is a machining error or assembly error in parts such as the steering device or the steering link mechanism, the apex of the above-mentioned change characteristics may shift from the steering neutral position. There is a problem in that the steering characteristics become asymmetrical in the vicinity of straight-line travel, resulting in poor straight-line travel performance, especially at high speeds. The present invention solves this problem by flattening the preload torque change characteristic near the center.

[Means for solving problems]

For this purpose, the steering device according to the present invention includes a rack 20 that is slidably supported by a casing 10 and moves back and forth in response to rotation of a steering shaft 15, as shown in FIGS. 1 to 4. An output shaft 13 that is orthogonal to the moving direction of the rack 20 and supported by the casing 10; and rack teeth 21 to 25 of the rack 20 that are provided integrally with the output shaft 13;
The sector gear 30 has four sector teeth 31 to 34 that mesh with the sector gear 30, and the tips of the teeth of the sectors 631 to 34 form a fan-shaped cone shape, and the amount of displacement gradually increases from the small diameter end A toward the large diameter end B. In a power steering device in which the gears are cut in the same manner as shown in FIG. The sector tooth surfaces 32a and 33a are on the dedendum side of the mesh line P, and the rack tooth surfaces 23a and 23b are on the tooth tip side of the mesh line P, with reference to the mesh line P that the teeth contact at the neutral steering position. The amount of correction is made on at least one of the tooth surfaces 32a, 33a, 23a,
This is characterized in that a modified tooth surface S is formed that increases in the direction of the bulge of the tooth 23b.

[Effect]

As shown in FIG. 1, the length of the meshing line P is fixed at the steering neutral position, but as the sector gear 3o rotates from the neutral position, the meshing line P moves in parallel on the sector tooth surfaces 32a and 33a. The length of the meshing line moving on the modified tooth surface S decreases. However, as this meshing line moves, the amount of modification of the modified tooth surface S at the destination increases, so the negative banklash increases, and even though the length of the meshing line decreases, the preload torque decreases. , is kept almost constant as shown at T in FIG. If the rotation angle of the sector gear 3o becomes large and the length of one mesh line becomes 0, the preload torque also becomes 0.

〔Effect of the invention〕

As described above, according to the present invention, at the steering neutral position,
The change characteristics of preload torque become flat. Therefore, even if the characteristics as a whole deviate to the left or right due to processing errors or assembly errors of parts, the steering characteristics near the steering neutral position will not become left-right asymmetrical, so that satisfactory straight running performance can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIGS. 3 and 4, the casing 10 of the steering device
A cylinder surface 10a is formed on the cylinder surface 10a, and the integrally formed piston 11 and rack 2o are slidably guided and supported on the cylinder surface 10a. The rack 20 has a ball screw shaft 1
2 are screwed together via balls, and the ball screw shaft 12 is connected via a servo valve 14 provided at one end of the casing 10.
Rotated by a steering shaft 15 connected to a steering handle,
The rack 20 is reciprocated. During this operation, the servo valve 14 supplies pressurized fluid from a pump (not shown) to the steering shaft 15.
According to the manual steering torque applied to the piston 11, the torque is supplied to the working chambers on both sides of the piston 11 to provide assist force to the steering device.

An output shaft 13 is rotatably supported on the casing 10 in a direction perpendicular to the sliding direction of the rack 20, and the output shaft 13 has a sector gear 30 having four sector teeth 31-34 that mesh with the rack teeth 21-25 of the rack 20. are integrated. As shown in the figure, the sectors 131 to 34 have tooth tip surfaces in the shape of a fan-shaped cone, and are cut so that the amount of displacement gradually increases from the small diameter end A toward the large diameter end B. As shown in FIG. 4, the bearing member 16 fixed to the casing 10 is connected to the output shaft 1.
3 is pivotally supported, and an adjustment screw 17 is provided at the center thereof.

As shown in FIGS. 1 to 3, in the neutral steering position, the pair of central sectors 632.33 mesh with the central rack teeth 23, and in this state, the tip of the adjusting screw 17 is brought into contact with the output shaft 13. , sector tooth 32.33 and rack M123
The axial position of the output shaft 13 is adjusted so as to provide an appropriate negative banklash during the period. When the output shaft 13 rotates, the other rack teeth 21, 22, 24, 25 become sector teeth 3.
1 to 34, but in this state, the other rack teeth 21, 22, 24, and 25 and sector teeth 31 to 34 mesh with each other.
An appropriate positive backlash should be given between 34 and 34.

Next, the shapes of the sector tooth surfaces 32a and 33a facing each other in the central sector 132, 33 will be explained. FIG. 1 shows the meshing state of the rack 20 and the sector gear 30 at the neutral steering position, and the meshing line P where the sector tooth surfaces 32a, 33a and the rack tooth surfaces 23a, 23b of the center rack tooth 23 come into contact [Only on the 1st surface 32a side] FIG. ) is inclined with respect to the intersection line R between the top surface of the rack 20 and the sector tooth surface 32a, and the meshing line P is connected to the small diameter end A of the sector gear 30 at a point Pa away from the bottom of the tooth. It intersects with the large diameter end B at a point pb close to the tooth bottom.Therefore, the sector tooth surface 3
2a, with this meshing line P as a boundary, the tooth tip side has a normal tooth profile including a dislocated tooth profile, and the tooth root side has a modified tooth surface S in which negative backlash gradually increases, as described below.

FIG. 2(a) shows a partially enlarged sectional view of the small diameter end A at the neutral steering position. Figure 2 (in al, rack tooth surface 2
As described above, the sector tooth surface 32a that meshes with the tooth surface 32a has a normal tooth profile that gives the above-mentioned appropriate negative banklash with the meshing point Pa as the boundary, and the tooth profile that provides the above-mentioned appropriate negative banklash on the tooth root side. The modified tooth surface S is formed in a direction that bulges out from the tooth profile 32c. The amount of correction of the modified tooth surface S with respect to the normal tooth profile 32c, that is, the amount of bulge from the tooth profile 32c is the meshing point P.
The rack tooth surface 23 is increased according to the distance from a to the root of the tooth.
The negative backlash is made to gradually increase between a and a. When the sector gear 30 rotates in the direction of the arrow in FIG. 2 (al), the meshing point moves from Pa along the modified tooth surface S. For example, the distance is 4 microns at the moving position of the meshing point corresponding to the rotation angle of 4 degrees of the sector gear 30.

As shown in FIG. 1, the width of the modified tooth surface S gradually narrows as it moves from the small diameter end A to the large diameter end B of the sector gear 30, but it is located on the mesh line P1 parallel to the mesh line P at the neutral steering position. The amount of correction in is basically the same. Large diameter end B
As shown in FIG. 2(b), the meshing point Pb is close to the tooth bottom, so the modified tooth surface S is small, and it is below the above-mentioned intersection line R and comes into contact with the rack tooth surface 23a. The shape of the sector tooth surface 32a has been described above, but
The shape of the sector tooth surface 33a facing this is also similar.

Note that the sector tooth surface 32b on the opposite side of the sector 832.33
, 33b and the rack tooth surfaces 22a, 24a of the rack teeth 22, 24 meshing therewith, as in the conventional case, an appropriate positive backlash is provided.

At the neutral steering position, as shown in FIG. 1, the sector tooth surfaces 32a, 33a and the rack tooth surface 23a.

The length of each engagement line P (only the one on the sector tooth surface 32a is shown) that 23b comes into contact with is L.

When the sector gear 30 rotates from the neutral position in the direction of the arrow shown in the figure, each meshing line P moves in parallel on the sector tooth surfaces 32a and 33a, and the meshing line P on the sector tooth surface 32a is corrected on the root side as shown in the drawing. When it moves on the tooth surface S and becomes the meshing line P1, its length Ll becomes smaller than that, and it moves further until the meshing point Pa at the small diameter end A reaches the meshing point Pr on the intersection line R mentioned above. ,
The length of the mesh line is O. On the other hand, the meshing line (not shown) on the other sector tooth surface 33a moves in parallel toward the tooth tip, and its length increases to the tooth width of the sector gear 30.

Sector tooth surfaces 32a, 33a and rack tooth surface 23a.

If the amount of negative backlash is constant, the preload torque between the sector gear 30 and the rack 20 due to the contact between the gears 23b and 23b will be as shown by the two-dot chain line T1 in FIG. Decreases as length decreases. However, in this embodiment, as the meshing line P1 moves toward the root side on the modified tooth surface S, the amount of negative bank lash increases, so the decrease in the length of the meshing line P1 is compensated for, and the preload torque is As shown by T in the figure, it is kept almost constant.

When the sector gear 30 rotates and the engagement point Pa reaches the above-mentioned point Pr, the preload torque rapidly decreases to zero.

In this way, according to this embodiment, the preload torque change characteristics are flat near the neutral steering position, so even if the characteristics deviate from side to side due to manufacturing errors, the steering characteristics near the neutral steering position will become asymmetrical. Therefore, satisfactory straight-line running characteristics can be obtained.

In the above, an example has been described in which the corrected tooth surface S is formed on the dedendum side of the meshing line P of the sector tooth surfaces 32a, 33a. Tooth surface 23a.

23b can also be carried out by forming a similar modified tooth surface on the tooth tip side from the meshing line P. Alternatively, the sector tooth surface 3
This can also be carried out by forming modified tooth surfaces on both the root side of the rack tooth surfaces 2a and 33a and the tooth tip side of the rack tooth surfaces 23a and 23b.

[Brief explanation of drawings]

1 to 4 show an embodiment of the steering device according to the present invention, FIG. 1 is a perspective view showing the meshing state at the steering neutral position, and FIGS. 2(a) and (bl show the same state) A partially enlarged sectional view at the small diameter end and large diameter end of the sector gear, FIG. 3 is a longitudinal sectional view of the whole, FIG. 4 is a sectional view IV-IV in FIG. 3,
FIG. 5 is a characteristic diagram of preload torque with respect to ten rotation angles of the sector gear. Explanation of symbols 10...Casing, 13...Output shaft, 15...
Steering shaft, 20... Rack, 21-25... Rack tooth, 23a, 23b... Rack tooth surface, 30... Sector gear, 31-34... Sector tooth, 32a, 33a...
・Sector tooth surface, A...Small diameter end, B...Large diameter end, P.
...Matching line, S...Corrected tooth surface.

Claims (1)

[Claims] a rack that is slidably supported by a casing and moves back and forth in response to the rotation of the steering shaft; an output shaft that is pivotally supported by the casing orthogonal to the direction of movement of the rack; and a rack that is integrally attached to the output shaft. The sector gear is provided with four sector teeth that mesh with the rack teeth of the rack, and the sector teeth have tooth tips that form a fan-cone shape and gradually increase the amount of displacement from the small diameter end toward the large diameter end. In a steering device in which gears are cut at a steering gear, a line of engagement is defined by which each sector tooth surface facing each other of a pair of center sector teeth and each rack tooth surface of a center rack tooth that meshes with these are in contact at a neutral steering position. As a reference, at least one of the tooth base side of the meshing line of each sector tooth surface and the tooth tip side of the meshing line of each rack tooth surface is adjusted according to the distance from the meshing line. A steering device characterized in that a modified tooth surface is formed in which the tooth surface increases in a direction in which each of the tooth surfaces bulges.