JPH0958489A - Steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rack pinion type steering device where a rack shaft which comprises a hollow shaft combined with a solid shaft, is practically so strengthened as to be sufficiently withstood against bending and twisting, ventilation for both sides of a power cylinder can be easily performed when the device is formed as a power steering device, and concurrently, the device is made light in weight. SOLUTION: An engagement part 20a in a circular shape in cross section is projected out of one side of a solid shaft 20, an engaging groove 20b is provided for the base end of the engagement part 20a. The end part of a hollow shaft 21 is outwardly fitted in the engagement part 20a, a thin wall part 21a at the tip end side is inwardly squeezed along the whole of its circumference, an engaging pawl 21b which projected in the inner circumference at the tip end of the thin wall part 21a, is engaged with the engaging groove 20b, and the hollow shaft 21 is combined with the solid shaft 20 so as to be formed into a rack shaft 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rack and pinion type steering device which is widely used as one type of steering device for an automobile.

[0002]

2. Description of the Related Art A rack and pinion type steering device supports a rack shaft slidably in an axial direction in a tubular housing extending in the left-right direction of a vehicle body, and the middle of the rack shaft is supported. While engaging the pinion linked to the steering wheel with the rack teeth formed on the side, both ends of the rack shaft protruding to both sides of the housing are connected to the left and right steering wheels (generally the front wheels) respectively. The rotation of the pinion according to the operation of the steering wheel is converted into the sliding of the rack shaft, and the direction of the steering wheel is changed.

The rack shaft is a long shaft having a length corresponding to the left and right width of the vehicle body. When the rack shaft is a solid shaft, the entire weight of the steering device including the rack shaft becomes excessive. On the other hand, in order to eliminate this inconvenience, if the whole is configured by a hollow shaft, in order to obtain the desired strength for the rack teeth formed in the middle of the rack shaft, a sufficient tooth height and bottom wall thickness are secured. There is a problem that it is difficult to do.

Further, in recent years, the steering force is assisted by the generated force of a power cylinder arranged in the steering mechanism so that the driver's labor required for steering wheel operation for steering can be reduced and a comfortable steering feeling can be obtained. The made power steering device (power steering device) is widely used. In the rack and pinion type steering device, the power cylinder utilizes a part of a housing supporting a rack shaft, and a part of the housing is liquid-tightly sealed to form a cylinder chamber of a predetermined length. A piston fixed to a rack shaft is slidably inserted in the chamber.

However, in this structure, since the inside of the housing supporting the rack shaft is separated into the left and right by the cylinder chamber, the sliding of the rack shaft causes the compression of the air trapped in the separation chambers on both sides. And inconvenience caused by expansion occurs, in order to eliminate this inconvenience,
It is necessary to provide a ventilation means that allows ventilation between the separation chambers, such as connecting the insides of both separation chambers with a communication pipe outside the housing.

In order to solve these problems collectively, conventionally, one side including a rack tooth forming region is set as a solid shaft,
A rack shaft having a hollow shaft on the other side is used. According to this structure, the overall weight can be reduced while ensuring the strength of the rack teeth, and the range extending over the range where the power cylinder is formed is the hollow shaft, and the cylinder chamber is formed by the ventilation hole penetrating the peripheral wall. It is possible to cause the separation chambers on both sides of the above to communicate with the hollow portion, respectively, so that the function as the ventilation means can be performed.

[0007]

In the rack shaft as described above, in general, a hole is bored from one end of the solid shaft to the shaft center portion, and the bored portion is used as a hollow shaft. Is gained by. However, in this case, a long perforation is required in order to reduce the weight as much as possible, and in particular, in the steering apparatus that constitutes the power steering apparatus by providing the above-mentioned power cylinder in the middle of the rack shaft, In order to extend the hollow part used as a ventilation means on both sides of the cylinder chamber, it is necessary to drill a length that exceeds twice the sliding stroke of the rack shaft. There is a drawback that it takes a lot of time and labor.

In Japanese Utility Model Laid-Open No. 4-75776, a hollow pipe material (hollow shaft rod) and a solid shaft material (rack shaft body) are used, and their ends are butted and joined by friction welding. , Configuring a rack shaft is disclosed. FIG.
[Fig. 4] is an enlarged cross-sectional view of this connecting portion.

A rack shaft 10, which is a main body of the rack shaft, has rack teeth 10, 10 ... Formed by flattening a part of its peripheral surface, and an outer edge of an appropriate thickness is formed on one end surface thereof. An annular recessed portion 11 is formed in excess, and a thin neck portion is formed at the axial center position of this recessed portion 11.
An enormous head 13 is projected through 12. The outer diameter of the enlarged head 13 is substantially equal to the inner diameter of the pipe material B to be joined, and the pipe material B is positioned coaxially with the shaft material A by using the enlarged head 13 as a guide as shown in the drawing. , The end portions of the pipe material B are brought into contact with the outer edge of the shaft material A, and are mutually rotated, and the friction heat generated at this time welds them to be integrated. As shown in the drawing, the annular recessed portion 11 and the small-diameter neck portion 12 are provided for retaining the inwardly protruding meat generated by the welding.

According to this structure, there is an advantage that a rack shaft having a desired shape in which the rack tooth forming side is solid and the other portion is hollow can be obtained without requiring troublesome perforation. Further, in Japanese Utility Model Laid-Open No. 4-75776, it is said that the joint between the shaft member A and the pipe member B has sufficient strength against the bending force acting on the rack shaft.

However, the tubular material B, which is the hollow shaft, is
As described above, the shaft member A is abutted and friction welded in a state where the vicinity of the joint end is fitted to the enlarged head 13, and when the bending force F acts on the pipe member B as shown in FIG. A bending force F ₀ increased by the action of the “lever” with the fitting portion with the enlarged head 13 as a fulcrum is applied to the joint portion with the shaft member A. Further, not only the bending force F ₀ but also the twisting force around the shaft acts on the rack shaft at the meshing position with the pinion, and the combined force of both acts on the joint between the shaft A and the pipe B. However, there is a problem that the joint portion is easily damaged.

The present invention has been made in view of such circumstances, and provides a rack shaft formed by connecting a hollow shaft and a solid shaft,
It was realized with sufficient strength against bending and twisting without requiring complicated processing, and when it was configured as a power steering device, it was made lightweight so that it could easily ventilate both sides of the power cylinder. It is an object to provide a rack and pinion type steering device.

[0013]

A steering device according to the present invention comprises a pinion interlocked with a steering wheel meshed with rack teeth formed on a part of a rack shaft, and the pinion according to the operation of the steering wheel. In a rack and pinion type steering device that slides the rack shaft in the axial direction to perform steering, the rack shaft includes a solid shaft including a formation region of the rack teeth, and the solid shaft. A hollow shaft that is externally fitted to a fitting portion that is coaxially formed at one end of the hollow shaft, and that is joined by caulking around the entire circumference in the vicinity of the end edge.

In the present invention, the hollow shaft is externally fitted to the fitting portion at one end of the solid shaft, and the end edges of the hollow shaft are caulked over the entire circumference, so that both shafts are axially and radially oriented. When the bending force is applied, the rack shaft is connected over the entire fitting length, and when the twisting force is applied, the rack shaft is connected by the sliding of the fitting portion. Absorbing, avoiding local concentration of force, alleviating the risk of damage and obtaining sufficient strength.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings showing the embodiments thereof. FIG. 1 is a front sectional view showing a main part of a rack and pinion type steering device according to the present invention.

The illustrated steering device is configured as a power steering device (power steering device) that assists the operating force of a steering wheel (steering wheel) for steering with hydraulic pressure. A rack shaft 2 slidably supported in the axial length direction is provided inside an extended rack housing 1 having a cylindrical shape. The rack shaft 2 includes a solid shaft 20 and a hollow shaft 21. It is configured to be coaxially coupled.

The rack shaft 2 is provided with rack teeth 2a formed over a predetermined length on the outer side of the middle portion thereof, and the portion between the rack teeth 2a including the formation region of the rack teeth 2a is the middle portion. Real axis
It is said to be 20. The end of the rack shaft 2 on the solid shaft 20 side is connected to a steering wheel (not shown) on the same side by a tie rod 23 connected via a ball joint 22.

On the other hand, the hollow shaft 21 is joined to the other end of the solid shaft 20 as will be described later, and is integrated with the solid shaft 20 to form the rack shaft 2. Like the other end of the solid shaft 20, the other end of the hollow shaft 21 (not shown) is connected to the steering wheel on the same side by a tie rod 23 connected via a ball joint 22. When the rack shaft 2 slides inside the vehicle, this sliding is transmitted to the steering wheels on both sides, and these directions are changed for steering.

A rack housing 1 surrounding the outside of the hollow shaft 21.
A sealing member 24, 24 (only one side is shown), which is fitted to the inner circumference of the shaft and slidably contacts the outer peripheral surface of the hollow shaft 21, seals a predetermined length range in a liquid-tight manner. A cylinder chamber S is formed by precisely finishing the inner peripheral surface, and a piston (not shown) fitted in the middle of the hollow shaft 21 is inserted into the cylinder chamber S to form a power cylinder for steering assistance. ing. This power cylinder generates an oil pressure (steering assist force) corresponding to a pressure difference generated on both sides of the piston by the action of the hydraulic pressure supplied to the inside of the cylinder chamber S, and applies this to the rack shaft 2. The operation of assisting the steering caused by the sliding of the rack shaft 2. The hydraulic pressure is supplied to the cylinder chamber S by the oil supply pipes 25, 25 connected near both ends of the cylinder chamber S. (Only one side is shown).

A gear housing 3 is provided in the middle of the rack housing 1 at a position facing the area where the rack teeth 2a of the solid shaft 20 are formed so as to intersect with the rack housing 1.
Are connected. FIG. 2 is an enlarged cross-sectional view taken along the line II-II of FIG. 1, showing a continuous portion of the gear housing 3. As shown in the figure, a pinion shaft 4 is supported in the lower half of the gear housing 3 including the position intersecting with the rack housing 1, and a hollow input shaft 5 is supported in the upper half of the gear housing 3 so as to be rotatable coaxially. These are coaxially connected by a torsion bar 6 inserted in the hollow portion of the input shaft 5.

The pinion shaft 4 is integrally provided with a pinion 4a on the outer periphery of a middle portion thereof, and the pinion 4a crosses the rack housing 1 and the rack teeth 2a on the outer periphery of the solid shaft 20.
Has been engaged. The upper end of the input shaft 5 protruding above the gear housing 3 is connected to a steering wheel (not shown). Thus, when the steering wheel operation for steering is performed, the input shaft 5 rotates about its axis, and this rotation is transmitted to the pinion shaft 4 via the torsion bar 6, and the pinion 4a and the rack teeth 2a. The rack shaft 2 is converted into a sliding state by meshing with and the steering is performed as described above. At this time, the torsion bar 6 connecting the input shaft 5 and the pinion shaft 4 is twisted. Along with this, relative angular displacement occurs.

At the connecting portion between the input shaft 5 and the pinion shaft 4,
The rotary hydraulic control valve 7 that performs the hydraulic pressure supply / discharge operation using the relative angular displacement as described above is configured, and the hydraulic pressure supplied from the hydraulic control valve 7 is connected to the outside of the gear housing 3. The oil is fed to the cylinder chamber S of the power cylinder via the oil feed pipes 25, 25, and the steering assist force corresponding to this operation is obtained in the operation direction of the steered wheels by the operation of the power cylinder in response to this feed. Yes. The supply of oil pressure to the oil pressure control valve 7 and the drainage of oil from the oil pressure control valve 7 are performed via a pump port 30 and a tank port 31 which are formed outside the gear housing 3 and have an opening, respectively. The oil pipe
25 and 25 are connected to respective oil supply ports (not shown) that are similarly formed.

The solid shaft 20 including the formation region of the rack teeth 2a
2 has a pentagonal cross section in which the side opposite to the pinion 4a is flattened and the other side is chevron-shaped as shown in FIG. 2, and the support yoke 32 elastically contacting the chevron surface directs it toward the meshing portion with the pinion 4a. Has been pressed. The rack tooth 2a has a solid shaft 20
It does not hinder the securing of the tooth height and the thickness of the root of the tooth because it is formed on the tooth surface, and since the surface on which the rack tooth 2a is formed is flat as described above, a large effective tooth length can be adopted. And the desired tooth strength is achieved.

The support yoke 32 presses the portion where the rack teeth 2a are formed from the back side, and ensures the engagement with the pinion 4a. Since the rack teeth 2a enable stable transmission between the rack teeth 2a and the pinion 4a, a helical gear having a predetermined inclination on its tooth surface is adopted as shown in FIG.
As a result, when the rack shaft 2 slides along with the rotation of the pinion 4a, a twisting force about the shaft acts on the rack shaft 2. However, the support yoke 32 forms a solid shaft on which the rack teeth 2a are formed. It is elastically contacted with 20 chevron surfaces, and can also perform the function of supporting the twisting force.

Now, the hollow shaft connected to one side of the solid shaft 20.
A tubular member 21 having a circular cross section is used to enable the sliding contact of the sealing members 24, 24 for forming the cylinder chamber S of the power cylinder. 20
The connection with and is performed as follows. FIG. 3 is an enlarged view of a connecting portion between the solid shaft 20 and the hollow shaft 21, and FIG. 4 is an explanatory view of a connecting procedure.

As shown in these figures, a fitting portion 20a for coupling with the hollow shaft 21 is provided at a substantially central position at the coupling side end portion of the solid shaft 20. The fitting portion 20a is a protrusion having a circular cross section having an outer diameter substantially equal to the inner diameter of the hollow shaft 21 to be joined, and an engaging groove 20b having a predetermined width is formed all around the outer circumference of the base end portion thereof. It is installed around. Further, a thin-walled portion 21a having an appropriate length is provided at the coupling-side end of the hollow shaft 21 by thinning the inner diameter side. Engaging claw 21b
Is projected inwardly over the entire circumference.

The connection between the solid shaft 20 and the hollow shaft 21 is
The respective coupling-side end portions are coaxially opposed to each other, and first, as shown in FIG.
As shown by the arrow inside, the hollow shaft 21 is fitted onto the fitting portion 20a of the solid shaft 20 and the thin portion 21a is fitted first, and the hollow shaft 21 is fitted, as shown in FIG.
As shown in Fig. 5, the edge of the engaging claw 21b at the tip of the thin portion 21a is abutted against the end surface of the solid shaft 20, and "caulking" is performed from the outside of the thin portion 21a to remove the thin portion 21a. It is realized as shown in FIGS. 1 and 3 by the procedure of inwardly deforming over the entire circumference and engaging the engaging claw 21b with the engaging groove 20b on the base end side of the fitting portion 20a. This "caulking" is, for example, a method in which a roll rotatably supported about an axis parallel to the rack shaft 2 is rotatably contacted with the outer peripheral surface of the thin-walled portion 21a and is made to circulate around the entire circumference under a predetermined pressure. It is realized by the so-called roll crimping method.

The solid shaft 20 has a notch groove 20c deeper than the engaging groove 20b between the outer peripheral surface of the solid shaft 20 and the end surface of the fitting portion 20a, as indicated by a broken line in the figure. Is formed. In the assembled state shown in FIG. 1, the notch groove 20c opens into the inner space of the rack housing 1 on one side of the cylinder chamber S and the hollow shaft 21 respectively, and a ventilation path that allows ventilation between the both. To form. The same ventilation passage is formed on the other side of the cylinder chamber S in the same manner, and when the rack shaft 2 slides in the rack housing 1, the ventilation on both sides of the cylinder chamber S is the same as the ventilation passage and the hollow. It is formed so as to pass through the inside of the shaft 21 so as not to hinder the sliding.

Under the above-described connection, the hollow shaft 21 is closely fitted with the fitting portion 20a protruding from the solid shaft 20 over a predetermined length and is restrained in the radial direction. The mating claw 21b and the engaging groove 20b are engaged with each other to be restrained in the axial direction, but the rotational force about the axis can be permitted by the relative rotation with respect to the fitting portion 20a. Therefore,
As described above, the twisting force generated in the solid shaft 20 at the meshing portion with the pinion 4a is absorbed by the relative rotation at the coupling portion with the hollow shaft 21 and is not transmitted to the hollow shaft 21.

Since the solid shaft 20 has an irregular cross section such as the pentagonal shape described above, and the support yoke 32 supports the twisting force, the force transmitted to the connecting portion with the hollow shaft 21 is the engaging portion with the pinion 4a. This is a part of the twisting force actually generated, and the above-mentioned twisting force can be absorbed without any trouble. This is because the half portion on the side where the rack teeth 2a are formed is the solid shaft 20, so that the hollow shaft 21 which is limited to the circular cross section due to the construction of the power cylinder and the solid shaft 20 having a different cross section are adopted. Then
This is achieved by allowing the support yoke 32 to bear a part of the twisting force.

On the other hand, since there is only an engaging relationship between the engaging claw 21b on the hollow shaft 21 side and the engaging groove 20b on the solid shaft 20 side, the reaction force from the steered wheel side is generated. The bending force applied to the solid shaft 20 or the hollow shaft 21 by the action of external force such as
Since it is dispersed over the entire fitting length of the hollow shaft 21 and the hollow shaft 21, it is possible to effectively mitigate the risk of breakage of the joint portion due to concentration of bending force.

[0032]

As described in detail above, in the rack and pinion type steering device according to the present invention, the hollow shaft is fitted on one end of the solid shaft, and the end edge of the hollow shaft extends over the entire circumference. By using a rack shaft constructed by connecting both shafts under axial and radial restraint by tightening, the overall weight can be reduced and sufficient strength against bending and twisting force can be obtained. The present invention has excellent effects such as being realized without requiring complicated processing while securing the same.

[Brief description of drawings]

FIG. 1 is a front sectional view showing a main part of a rack and pinion type steering device according to the present invention configured as a power steering device.

FIG. 2 is an enlarged sectional view taken along line II-II of FIG.

FIG. 3 is an enlarged view of a connecting portion between a solid shaft and a hollow shaft.

FIG. 4 is an explanatory view of a procedure for connecting a solid shaft and a hollow shaft.

FIG. 5 is an enlarged cross-sectional view of a connecting portion of a conventional rack shaft formed by connecting a solid shaft and a hollow shaft.

[Explanation of symbols]

 1 rack housing 2 rack shaft 2a rack teeth 4 pinion shaft 4a pinion 20 solid shaft 20a mating part 20b engaging groove 20c notch groove 21 hollow shaft 21a thin part 21b engaging claw S cylinder chamber

Claims (1)

[Claims] 1. A pinion interlockingly connected to a steering wheel meshes with rack teeth formed on a part of a rack shaft, and the rack shaft is axially moved by rotation of the pinion in response to operation of the steering wheel. In a rack and pinion type steering device for sliding and steering, the rack shaft includes a solid shaft including a formation region of the rack teeth, and a fitting portion coaxially formed at one end of the solid shaft. And a hollow shaft that is externally fitted to and is caulked around the entire periphery thereof by caulking.