JPS628861A - Steering device - Google Patents

Abstract

PURPOSE:To level off the characteristics of change in preload torque by correcting either an area of a sector gear tooth face which is from the center of the tooth width to the large pitch diameter side, or an area of a rack tooth face which comes in contact with the said area of the sector gear tooth face, in such way that the negative backlash is removed. 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. A negative backlash is provided between each of the faces of sector gear teeth 32a and 33a which faces each other, of a pair of sector gear teeth 32 and 33 at the center, and each of the faces of rack gear teeth 23a and 23b which are meshed with the above said sector gear teeth. And at least one of either areas S and Sa of the faces of the sector gear 32a and 33a on the large pitch diameter side B, or areas of the faces of the rack-gear teeth 23a and 23b which come in contact with the above said area of the face of the sector gear, is corrected in such a way that the negative backlash is removed.

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. 2 and 3, 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 backlash is provided between the pair of sectors 132 and 33 that mesh with this, and a positive backlash is provided between the other rack teeth and the sector teeth, and the central rack tooth 2
A preload torque is applied to the steering handle near the steering neutral position where the sector 3 engages with both sectors 132 and 33.

[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
O is the 1st TI! As shown in J, it is inclined with respect to the intersection line R between the tooth top surface of the rack 20 and the sector tooth 32. Therefore, the length of the engagement line PO at the steering neutral position is LO,
As the sector gear 30 rotates from the neutral steering position, the length of the mesh line PO becomes shorter, so the change characteristic of the preload torque with respect to the rotation angle of the sector gear 30 is
As shown in OD, it becomes a mountain shape with the steering neutral position at its apex.Therefore, there may be machining errors in the rack 20 and sector gear 30, or machining errors or assembly errors in parts such as the steering device and steering link mechanism. If this happens, the apex G of the change characteristics will deviate from the neutral steering position, and the steering characteristics will become asymmetrical in the vicinity of straight-line driving, resulting in poor straight-line driving performance especially at high speeds. This problem is solved by flattening the 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 3. 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 sector teeth 31 to 34 have tooth tips in a fan-shaped conical shape, and the amount of displacement gradually increases from the small diameter end A to the large diameter end B. Each sector tooth surface 3 facing each other of the central pair of sector teeth 32, 33 with increasing gear cutting
2a, 33a and each rack tooth surface 23a, 23b of the central rack tooth 23 meshing therewith.In the steering device, each of the sector tooth surfaces 32
a.

33a on the side of the large diameter end B from the middle position in the tooth width direction, and a small area of each of the rack tooth surfaces 23a, 23b that abuts on these areas S, Sa (one of the areas S and Sa on the side of the large diameter end B is This is characterized by correction in the direction of eliminating backlash.

[Effect]

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

The meshing line of 23b is PO, and as the sector gear 30 rotates from the neutral position, the meshing line changes to the sector tooth surfaces 32a, 3.
3a to become PI, P2, or in the opposite direction to become P3. However, the line of engagement is from PO to P.
The length of the meshing line is a constant value L1 regardless of the rotation angle of the sector gear 30 until the position moves to P.
Once l is exceeded, the length of the meshing line gradually decreases, for example as shown by the length L2 of the meshing line P2, and finally the length of the meshing line becomes O. Therefore, the preload torque is CEF in Figure 4.
As shown in D, the beam becomes constant near the neutral steering position, and then gradually decreases to O toward both sides.

〔Effect of the invention〕

As described above, according to the present invention, the preload torque change characteristic becomes flat near the neutral steering position. 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. 2 and 3, 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 2o 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 sector teeth 31 to 34 have a fan-shaped conical tip surface 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 the figure, the bearing member 16 fixed to the casing 10
3 is pivotally supported, and an adjustment screw 17 is provided at the center thereof.

As shown in FIGS. 1 and 2, in the neutral steering position, the center pair of sectors i32 and 33 are connected to the center rack tooth 23.
In this state, the tip of the adjusting screw 17 is brought into contact with the output shaft 13, and the sector! 32.33 and rack 823
The axial position of the output shaft 13 is adjusted so as to give an appropriate negative buff crush during this period. When the output shaft 13 rotates, the other rack teeth 21, 22, 24, 25 become the sector teeth 3.
1 to 34, but in this state, other rack teeth 21.22.24.25 and sectors 631 to 34 mesh with each other.
I try to give an appropriate positive buff crush between 34 and 34.

Next, the shapes of the mutually opposing sector tooth surfaces 32a and 33a of the central sector teeth 32 and 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 PO (only the tooth surface 32a side (shown) is inclined with respect to the intersection line R between the tooth top surface of the rack 20 and the sector tooth surface 32a.However, unless the modification described below is made to the sector tooth surface 32a, the meshing will not be possible. The length of the line PO is LO, and the meshing line PO intersects the small diameter end A of the sector gear 30 at a point Pa away from the tooth bottom, and intersects the large diameter end B at a point Pb close to the tooth bottom.

In this embodiment, as shown in FIG.
A region S on the large diameter end B side of the boundary line Q located in the middle in the tooth width direction on 2a in a direction excluding the negative bank lash,
In other words, the thickness of the sector teeth 32 is modified in the direction of decreasing. This correction amount S is kept constant, and its value is set to be the same as or slightly larger than the negative backlash amount.

Further, this correction is performed by using a rack-shaped or full-shaped cutter or grinding wheel and feeding it from the large diameter end B side to the boundary line Q after forming the sector tooth surface 32a. The above has been described about the rack tooth surface 32a, but a region Sa is provided symmetrically to the region S on the sector tooth surface 33a opposite thereto.
Similar modifications shall be made.

The boundary line Q is located closer to the small diameter end A than the intersection O between the above-mentioned intersection line R and the engagement line PO at the neutral steering position, and as the distance between the boundary line Q and the intersection O increases,
The width of the flat portion EF at the center of the preload torque characteristic diagram in FIG. 4 increases. In this embodiment, the boundary line Q is parallel to both end surfaces A and B of the sector gear 30, but the boundary line Q
may be slightly inclined, in which case the central flat part EF
has a slightly convex or concave shape. Also, screw in the adjustment screw 17 to adjust the sector tooth surfaces 32a, 33a and the rack tooth surface 23a.
, 23b, the height of the central flat portion EF can be increased without substantially changing the width direction of the preload torque characteristic diagram. Note that the sector tooth surface 32b on the opposite side of the sector tooth 32°33,
33b and the rack tooth surfaces 22a, 24a of the rack teeth 22, 24 meshing therewith, an appropriate positive backlash is provided as in the conventional case.

According to this embodiment, at the neutral steering position, as shown in FIG.
Each meshing line P0 (sector tooth surface 32
(only those on a are shown) are interrupted by a boundary line Q, each of whose length is Ll, which is shorter than LO. When the sector gear 30 rotates from the neutral position in the direction of the arrow shown in the figure, each meshing line moves in parallel on the sector tooth surfaces 32a and 33a, and the length of the meshing line on the sector tooth surface 32a moves from PO to Pi. is a constant value L1 regardless of the rotation angle of the sector gear 30.
becomes. If Pl is exceeded, the mesh line intersects with the intersection line R, and the portion of the sector tooth surface 32a below the intersection line R does not come into contact with the rack teeth 23a, so for example, the mesh line P2
As shown in the length L2, the length of the meshing line gradually decreases,
After further movement, the engagement point pa of the small diameter end A reaches the above-mentioned intersection line R.
When the upper engagement point Pr is reached, the length of the engagement line becomes 0.

On the other hand, the engagement line (not shown) on the other sector tooth surface 33a moves in parallel to the tooth tip side, and its length remains at Ll (corresponding to P3 on the sector tooth surface 32a).

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

The preload torque between the sector gear 30 and the rack 20 caused by the contact between the sector gear 23b and the rack 20 varies depending on the length of the shorter engagement line, so as shown in CEFD in FIG. 4, the preload torque is constant near the neutral steering position. , and then gradually decreases to 0 on both sides. 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, the areas S and Sa on the large diameter end B side from the boundary line Q at the intermediate position in the tooth width direction on the sector tooth surfaces 32a and 33a,
Although the example in which the correction was made in the direction of eliminating negative backlash has been described, the present invention makes similar corrections to the area on the large diameter end B side on the rack tooth surfaces 23a, 23b that come into contact with the areas S, Sa. It can also be implemented, and sector tooth flank 3
2a.

This can also be carried out by similarly modifying both the regions S, Sa on 33a and the said regions on rack tooth surfaces 23a, 23b.

In the above embodiment, in the neutral steering state, almost the entire tooth width of the sector tooth surfaces 32a, 33a contacts on the meshing line PO, but depending on the tooth shape, in the neutral steering state, for example, the sector tooth surfaces 32a, 33a contact on the meshing line P1, There may be no contact on the large diameter end side B. In such a case, the sector gear 30 is formed with a small amount of displacement so that the contact is made at approximately the gold tooth width. may be modified.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the steering device according to the present invention, in which FIG. 1 is a perspective view showing the meshing state at the neutral steering position, FIG. 2 is a longitudinal sectional view of the whole, and FIG. m-m in Figure 2
The cross-sectional view and FIG. 4 are characteristic diagrams of preload torque with respect to sector gear rotation angle. 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, Q.
・Intermediate position in tooth width direction (border line), S, Sa... area.

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 the steering device, the steering device is configured to provide a negative backlash between the mutually opposing sector tooth surfaces of a pair of central sector teeth and each rack tooth surface of the central rack teeth that mesh with the sector tooth surfaces, At least one of the area on the large diameter end side from the intermediate position in the tooth width direction on each sector tooth surface and the area on each rack tooth surface that abuts this area in a direction to eliminate the negative backlash. A steering device characterized by being modified to.