JP3671135B2 - Rack and pinion steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rack and pinion type steering device that rotates by rotating a pinion shaft in conjunction with a rotating operation of a steering wheel, and reciprocates a rack shaft that meshes with the pinion shaft in the axial direction.
[0002]
[Prior art]
In general, in a rack and pinion type steering device, a support yoke is provided to press the rack shaft toward the pinion shaft while allowing the rack shaft to move in the axial direction on the opposite side of the pinion across the rack shaft. The rigidity for supporting the shaft is increased, and the backlash at the meshing portion between the rack and the pinion is reduced.
However, since the sliding resistance between the support yoke and the rack bar is large, the rotational torque necessary for the rotation of the steering shaft increases. In particular, at the time of the initial movement of the steering operation, the steering torque itself of the steering wheel is small, so that there is a problem that the above-mentioned sliding resistance adversely affects the steering feeling.
[0003]
Therefore, an attempt has been made to reduce the movement resistance of the rack shaft by holding a ball that is in rolling contact with the rack shaft on a support yoke and urging the ball toward the rack shaft via the ball.
[0004]
[Problems to be solved by the invention]
However, improper contact between the receiving seat provided on the support yoke to receive the ball and the ball will result in the rolling surface between the ball and the rack shaft and the rolling surface between the ball and the support yoke. Slip occurs. For this reason, smooth movement of the rack shaft is hindered, and a desired steering feeling may not be obtained.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a rack and pinion type steering apparatus that can improve the steering feeling.
[0005]
[Means for Solving the Problems and Effects of the Invention]
In order to achieve the above object, the present invention provides a rack and pinion type steering apparatus including a pinion shaft that meshes with each other in a gear case and a rack shaft having an arcuate cross section, and a plurality of balls that make point contact with the peripheral surface of the rack shaft. A cylindrical receiving member which is housed in a housing provided in the gear case so as to be able to advance and retreat, and receives the plurality of balls in a freely rolling manner, and the rack shaft to the pinion shaft side via the receiving member and the plurality of balls . A plurality of balls, each of which includes a pair of balls disposed on both sides of a plane including the center axis of the rack shaft and the center axis of the receiving member, seat for receiving the ball, respectively is formed, the receiving seat comprises a conical tapered surface, in a plane perpendicular to the rack shaft including the center of each ball, the contact point between the ball and the rack shaft, and the balls Receiving part Straight line connecting the contact point with is characterized in that through the substantially center of the ball.
[0006]
In the present invention, on the plane orthogonal to the rack axis, the axis including the center of the ball and orthogonal to the straight line is the rotation axis of the ball . Therefore, when the rack shaft moves in the axial direction along with steering, the balls can roll smoothly without causing any slippage with respect to the rack shaft or the support member. As a result, the steering feeling is improved. Further, the receiving member is formed with a receiving seat for receiving the ball, and this receiving seat includes a conical tapered surface, so that the ball can be stably held by the conical tapered surface, and the behavior of the ball is stabilized. In particular, even if there is some dimensional error in each part, it is preferable in that the ball can be stably held. Moreover, if it is a conical taper surface, a process will be easy.
The present invention also includes a support member that has a concave surface that receives the peripheral surface of the rack shaft when necessary, and is housed in a housing hole provided in the housing so as to be able to move forward and backward. The support member may further include a receiving member receiving hole for receiving and receiving the receiving member and a ball receiving hole for receiving and moving the ball .
[0007]
Further, the present invention has a concave surface for receiving a peripheral surface of the rack shaft when required, further comprising a support member back and forth non fixed in the depth direction of the receiving hole in the housing hole provided in the housing, the support member and it may include receiving a receiving member receiving hole for retractably housing the member, and a ball housing hole for retractably housing the balls.
In these cases, in the initial motion region of the steering operation (the so-called neutral region, which is a small load region with small displacement), the ball contacts the moving rack shaft without slipping, so the movement resistance of the rack shaft Can be reduced, and the steering feeling can be improved. Further, when a heavy load is input, the rack shaft can be firmly supported by receiving the rack shaft by the support member. In the latter case, since the support member does not move, an urging member that urges the support member is unnecessary, and as a result, the number of parts can be reduced.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view of a rack and pinion type steering apparatus according to an embodiment of the present invention. The pinion shaft 1 is rotatably supported in the gear case 4 by rolling bearings 2 and 3, and the rack shaft 5 is supported by a bearing member (not shown) so as to be movable along the axial direction (direction orthogonal to the paper surface). ing. The pinion shaft 1 and the rack shaft 5 are meshed with each other in the gear case 4. Although not shown, both ends of the rack shaft 5 are connected to the steering wheel via tie rods, and the rack shaft 5 moves in the axial direction along with the rotation of the steering wheel (not shown) to perform the steering. .
[0010]
The gear case 4 is provided with a housing 6 on the opposite side of the pinion shaft 1 across the rack shaft 5, and a support yoke 8 as a support member for supporting the rack shaft 5 slides inside the housing hole 7 of the housing 6. It is freely housed. The support yoke 8 is formed in a cylindrical shape, and a concave surface 9 having an arcuate cross section is formed along the peripheral surface 5 a of the rack shaft 5.
A screw portion 10 is formed at the entrance of the housing hole 7 of the housing 6, and a fixing plug 11 is screwed into the screw portion 10 and is fixed by a lock nut 12. The fixed plug 11 is opposed to the back surface 13 of the concave surface 9 of the support yoke 8 with a predetermined gap (for example, 0.1 mm). A spring housing hole 14 made of a circular hole is formed in the back surface 13 of the support yoke 8, and a compression coil spring 15 as a biasing member that biases the support yoke 8 toward the rack shaft 5 in the spring housing hole 14. Is housed.
[0011]
The concave surface 9 of the support yoke 8 is formed with ball receiving holes 16 as a plurality of rolling element receiving holes, and balls 17 as rolling elements that are in rolling contact with the peripheral surface 5a of the rack shaft 5 rotate in the respective ball receiving holes 16. It is held freely. The support yoke 8 constitutes a receiving member that receives the balls 17.
2 is a schematic enlarged cross section of the rack shaft 5 and the support yoke 8 cut along a plane P that includes the center 21 of the ball 17 and is orthogonal to the rack shaft 5 (axis extending in the axial length direction of the rack shaft 5). FIG. With reference to FIG. 2, the present embodiment is characterized in that, in the plane P, the contact point 18 between the ball 17 and the peripheral surface 5 a of the rack shaft 5, and the contact point between the ball 17 and the support yoke 8. That is, the straight line 20 that connects 19 passes through the center 21 of the ball 17 or the vicinity thereof.
[0012]
The ball receiving hole 16 is a hole having an axis parallel to the direction in which the support yoke 8 advances and retreats, and a receiving seat 22 made of, for example, a conical tapered surface is formed at the bottom of the hole. The receiving seat 22 has an arc-shaped contact line 23 with respect to the ball 17, and the contact line 23 includes the contact point 19. It is preferable that the apex angle A of the conical tapered surface forming the receiving seat 22 is set to be approximately twice the contact angle B of the ball with respect to the rack shaft 5 (that is, A = 2B).
[0013]
In the present embodiment, on the plane P, the axis 24 that includes the center 21 of the ball 17 and is orthogonal to the straight line 20 is the rotation axis of the ball 17. Therefore, when the rack shaft 5 moves in the axial direction along with the steering, the balls 17 can roll smoothly with almost no slip with respect to the rack shaft 5 and the support yoke 8. As a result, the steering feeling is improved.
Further, the ball 17 can be stably held by the conical tapered surface forming the receiving seat 22, and the behavior of the ball 17 is stabilized. In particular, even if there is some dimensional error in each part, it is preferable in that the ball 17 can be stably held. Moreover, if it is a conical taper surface, a process will be easy.
[0014]
Next, FIG. 3 is a cross-sectional view of a rack and pinion type steering apparatus according to another embodiment of the present invention. Referring to FIG. 3, in support yoke 8A, receiving member 29 for receiving ball 17 is slidable at the bottom of accommodation hole 26 for accommodating first compression coil spring 25 as a first urging member. A receiving member accommodating hole 28 for accommodating in the housing is formed. A second compression coil spring 27 as a second urging member is also accommodated in the receiving member accommodation hole 28. The diameter of the receiving member accommodation hole 28 is slightly smaller than the diameter of the accommodation hole 26.
[0015]
The second compression coil spring 27 is interposed between an annular spring seat 30 fixed to the bottom of the accommodation hole 26 and a movable receiving member 29. The second compression coil spring 27 urges the ball 17 to the rack shaft 5 side via the receiving member 29. The spring constant of the second compression coil spring 27 is set to be much smaller than the spring constant of the first compression coil spring 25.
On the other hand, at least a pair of balls 17 are disposed on both sides of the top of the rack shaft 5, and are respectively accommodated in small-diameter ball receiving holes 31 formed so as to open in the concave surface 9 of the support yoke 8A. ing. The ball receiving holes 31 for the balls 17 communicate with the receiving member receiving holes 28, respectively. On the concave surface 9 of the support yoke 8A, a low-friction pad 32 is attached for sliding contact with the peripheral surface 5a of the rack shaft 5 when a large load is input.
[0016]
The receiving member 29 is integrally provided with a plurality of protrusions 33 that come into contact with the corresponding balls 17 from the rear. The balls 17 are energized together. On the surface of each projection 33 facing the ball 17, a receiving seat 34 formed of a conical tapered surface that receives the ball 17 is formed. The structure of the receiving seat 34 is the same as that of the receiving seat 22 in FIG. Reference numeral 45 denotes an annular positioning step that contacts the outer edge of the receiving member 29. When the receiving member 29 comes into contact with the positioning step 45, the maximum protrusion amount of the ball 17 from the ball receiving hole 31 is defined.
[0017]
According to the present embodiment, in the initial operation region of the steering operation (so-called neutral region and a small load region with small displacement), as shown in FIG. Since the balls 17 protruding from 31 are in rolling contact with each other, the movement resistance of the rack shaft 5 can be reduced, and the steering feeling can be improved. Further, at this time, the ball 17 can roll smoothly with almost no slip with respect to the rack shaft 5 and the support yoke 8A, so that the steering feeling becomes good.
[0018]
On the other hand, when a heavy load is input, as shown in FIG. 4, the second compression coil spring 27 is bent and the ball 17 is retracted into the ball receiving hole 31, so that the support yoke 8 </ b> A moves the rack shaft 5 through the pad 32. As a result, the rack shaft 5 can be firmly supported.
In addition, since the second compression coil spring 27 is accommodated in the receiving member accommodation hole 28 that has more space than the ball accommodation hole 31 for the ball 17, the coil diameter of the spring, the wire diameter, the spring length, etc. It can be set relatively freely. As a result, it is possible to obtain a desired urging load without particularly sizing the second compression coil spring 27.
[0019]
Next, FIG. 5 shows another embodiment of the present invention. Referring to FIG. 5, the present embodiment is different from the embodiment of FIG. 3 in that the second compression coil spring 35 passes through the inside of the annular spring seat 30 and the first compression coil spring 25. In this manner, one end of the second compression coil spring 35 is in contact with the fixed plug 11 in the same manner as one end of the first compression coil spring 25. In addition, about the structure similar to embodiment of FIG. 3, the same code | symbol was attached | subjected to the figure and the description was abbreviate | omitted.
[0020]
In the present embodiment, the same effects as those of the embodiment of FIG. 3 are obtained. In addition, since the second compression coil spring 35 is interposed between the receiving member 29 and the fixed plug 11 and the set length of the second compression coil spring 35 can be increased, the urging load can be reduced. Is preferable. This is because the balls 17 only have to work so as to roll and come into contact with the rack shaft 5 in the vicinity of the neutral position. From this viewpoint, it is preferable that the biasing load of the second compression coil spring 35 biasing the balls 17 is small. is there.
[0021]
Next, FIG. 6 shows still another embodiment of the present invention. Referring to FIG. 6, the present embodiment is different from the embodiment of FIG. 5 as follows.
That is, a support yoke 36 as a support member that slidably supports the rack shaft 5 in the axial direction is fixed to the fixing plug 37, thereby fixing the rack 6 in the housing hole 7. Accordingly, the first compression coil spring 25 is abolished.
[0022]
Further, a bottomed cylindrical receiving member 39 for receiving the ball 17 is slidably received in a receiving member receiving hole 38 penetrating the support yoke 36. A compression coil spring 40 is accommodated between the receiving member 39 and the fixed plug 37 as an urging member that urges the balls 17 toward the rack shaft 5 via the receiving member 39. The receiving member 39 is provided with a projection 33 that forms a receiving seat 34 having a conical tapered surface that receives each ball 17.
[0023]
The receiving member 39 has a spring receiving seat 41 that is a recess that receives the compression coil spring 40, and a guide peripheral wall 42 that guides most of the outer periphery of the compression coil spring 40 is formed around the spring receiving seat 41. Has been. The fixed plug 37 is similarly formed with a recess 44 for providing the guide peripheral wall 43. In addition, about the structure similar to embodiment of FIG. 5, the same code | symbol was attached | subjected to the figure and the description was abbreviate | omitted.
In the present embodiment, the same operational effects as in the embodiment of FIG. In addition, in the initial operation region of the steering operation (a so-called neutral region, which is a small load region with small displacement), the balls 17 are in rolling contact with the moving rack shaft 5, so that the movement resistance of the rack shaft 5 is reduced. The steering feeling can be improved. When a heavy load is input, the fixed support yoke 36 can receive the rack shaft 5 via the low friction pad 32 and can firmly support the rack shaft 5.
[0024]
Further, since the support yoke 36 is not moved, an urging member that urges the support yoke 36 is unnecessary, and as a result, the number of parts can be reduced.
The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a main part of a rack and pinion steering device according to an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view of FIG. 1, showing a state at the time of a small input.
FIG. 3 is a cross-sectional view of a main part of a rack and pinion steering device according to another embodiment of the present invention.
4 is an enlarged cross-sectional view corresponding to FIG. 3 and shows a state at the time of a large input.
FIG. 5 is a cross-sectional view of a main part of a rack and pinion steering device according to still another embodiment of the present invention.
FIG. 6 is a cross-sectional view of a main part of a rack and pinion steering device according to still another embodiment of the present invention.
[Explanation of symbols]
1 Pinion shaft 5 Rack shaft 6 Housing 8 Support yoke (support member, receiving member)
8A Support yoke (support member)
9 Concave surface 10 Pads 11 and 37 Fixed plug 14 Housing hole 15 Compression coil spring (biasing member)
16 Ball receiving hole (Rolling element receiving hole)
17 balls (rolling elements)
18, 19 Contact point 20 Straight line 21 Center 22 Receiving seat 24 Axis
25 1st compression coil spring (1st biasing member)
26 receiving hole 27 second compression coil spring (second biasing member)
28 receiving member receiving hole 29 receiving member 31 ball receiving hole (rolling element receiving hole)
33 Protrusion 34 Receiving seat 35 Second compression coil spring 36 Support yoke (support member)
38 receiving member receiving hole 39 receiving member 40 compression coil spring

Claims (3)

In a rack and pinion type steering apparatus comprising a pinion shaft that meshes with each other in a gear case and a rack shaft having an arcuate cross section,
A plurality of balls in point contact with the peripheral surface of the rack shaft;
A cylindrical receiving member that is housed in a housing provided in the gear case so as to freely advance and retract, and receives the plurality of balls in a freely rolling manner ;
A biasing member that biases the rack shaft toward the pinion shaft through the receiving member and the plurality of balls ;
The plurality of balls includes a pair of balls arranged on both sides across a plane including the central axis of the rack shaft and the central axis of the receiving member,
The receiving member is formed with a receiving seat for receiving each ball, and the receiving seat includes a conical tapered surface,
In a plane that includes the center of each ball and is perpendicular to the rack axis, a straight line that connects the contact point between the ball and the rack shaft and the contact point between the ball and the receiving member passes through the approximate center of the ball. Rack and pinion type steering device. A support member that has a concave surface for receiving the peripheral surface of the rack shaft when required, and is accommodated in a housing hole provided in the housing so as to be freely reciprocated
A biasing member that biases the support member toward the rack shaft;
The rack-and-pinion steering device according to claim 1, wherein the support member includes a receiving member receiving hole for receiving the receiving member so as to be movable back and forth, and a ball receiving hole for receiving the ball reciprocally. A support member that has a concave surface that receives the peripheral surface of the rack shaft when required, and is fixed to a housing hole provided in the housing so as not to advance or retract in the depth direction of the housing hole ;
The rack-and-pinion steering device according to claim 1, wherein the support member includes a receiving member receiving hole for receiving the receiving member so as to be movable back and forth, and a ball receiving hole for receiving the ball reciprocally.

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