JPS6023250Y2 - Rotary valve type power steering device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a rotary valve type power steering device in which the method of fixing a torsion bar to a worm shaft is improved.

FIG. 1 is a longitudinal sectional view of a conventional rotary valve type power steering device.

In the figure, a stub shaft 1 whose tip half has a cylindrical shape is connected to a bundle on the right side in the figure, and is rotated by the bundle operation. A cylindrical worm shaft 2 is arranged in the stub shaft 1 and the worm shaft 2.
rotate independently from each other within a predetermined angular range, and rotate integrally beyond this angle.

A torsion bar 3 is arranged concentrically inside the cylinder of the worm shaft 2, and one end (left side) of this torsion bar 3 becomes slightly thicker and fits into the inner peripheral surface of the worm shaft 2. A pin 4 is inserted into the portion to prevent rotation.

The other end (right side) of the torsion bar 3 is slightly thicker like the one end and is fitted into the inner circumferential surface of the stub shaft 1, and a pin 5 is similarly inserted into this fitting part to prevent rotation. There is.

Note that 6 and 7 are O-rings for preventing oil from leaking from this fitting portion.

A cylindrical rotor 8 is provided on the outer periphery of the stub shaft 1, and this rotor 8 has pins 9 mounted on the stub shaft 1.
It is engaged with and rotates together with it.

A cylindrical sleeve 1 is further provided concentrically around the outer circumference of the rotor 8.
0 is provided, and this sleeve 10 is connected to the worm shaft 2
It is engaged with a pin 11 implanted in and rotates together with the pin 11.

The rotor 8 and sleeve 10 constitute a well-known rotary valve.

Note that 12, 13, 14, and 15 are flow paths formed in the rotary valve for passing oil.

On the other hand, a piston 16 is provided concentrically on the outer periphery of the worm shaft 2, and the piston 16 and the worm shaft 2 are connected by a worm mechanism using a ball 17.

Therefore, when the worm shaft 2 rotates, the piston 16 is decelerated and moves in the axial direction within the cylinder body 18.

Further, rack teeth 19 are formed on a part of the outer periphery of the piston 16, and a sector shaft 20 connected to a pitman arm (not shown) is engaged with the rack teeth 19.

A left cylinder chamber 21 is formed in a space surrounded by the left side of the cylinder body 18 and piston 16 in the figure, and a right cylinder chamber 22 is formed in a space surrounded by the right side of the cylinder body 18 and piston 16 in the figure. has been done.

A ring-shaped flow path 23 is formed on the outer peripheral surface of the piston 16, and this flow path 23 connects to the left cylinder chamber 21 via a flow path 24.
At the same time, it opens into the sector shaft chamber 25.

This sector shaft chamber 25 is connected to the flow path 15 of the rotary valve via flow paths 26 and 27.

Further, the right cylinder chamber 22 is connected to the flow path 14 of the rotary valve via a flow path 28.

Note that 29 is an outlet connected to an oil tank.

In such a configuration, when the handle is in the neutral position, pressurized oil from the pump enters through the inlet (not shown), passes through channels 12, 13, and enters channels 14 and 15, while at the same time entering the outlet 29. Go through and return to the tank.

At this time, the oil that has entered the flow path 14 passes through the flow path 28 and enters the right cylinder chamber 22, and the oil that has entered the flow path 15 enters the flow paths 27 and 26, the sector shaft chamber 25, and the flow paths 23 and 24.
It then enters the left cylinder chamber 21.

Since the flow paths 14 and 15 are connected to each other outside the flow path 13, the left cylinder chamber 21 and the right cylinder chamber 22 have the same pressure.
Since no pressure difference is generated between them, the piston 16 maintains a neutral position without any actuation force acting in the axial direction.

Here, when the handle is turned to the right, the stub shaft 1 rotates in the same direction, but the worm shaft 2 does not immediately rotate and stops because the load of the ground resistance of the tire is acting on the worm shaft 2. Therefore, the torsion bar 3 connected between the stub shaft 1 and the worm shaft 2 is twisted.

On the other hand, due to the rotation of the stub shaft 1, the rotor 8 of the rotary valve
rotates relative to the sleeve 10 to switch the flow path, and the pressure oil entering from the inlet (not shown) flows into the flow path 1.
2, 13, 15, 27, 26, sector shaft chamber 25,
The oil enters the left cylinder chamber 21 through channels 23 and 24, and the oil in the right cylinder chamber 22 flows out through channels 28 and 14 from an outlet 29 into the tank.

As a result, a pressure difference is generated between the left cylinder chamber 21 and the right cylinder chamber 22, and the piston 16 receives an operating force in the right axial direction in the figure.

When the stub shaft 1 has turned by a predetermined angle or more, the stub shaft 1 hits the worm shaft 2 in the direction of rotation, so from this point on, the worm shaft 2
The piston 16 is worm-coupled by the rotation of the worm shaft 2, which rotates together with the stub shaft 1.
moves to the right in the figure and rotates the sector shaft 20 clockwise in the figure.

In this case, the actuation force due to oil pressure is applied to the piston 16.
Since the steering wheel is attached in the same direction as the steering wheel, steering can be done with light operating force.

When the rotation of the stub shaft 1 stops after turning the handle, the load on the worm shaft 2 is lightened by the actuation force generated by the oil pressure of the piston 16, so that the twisted torsion bar 3 returns to the neutral position.

As a result, the sleeve 10 also returns to the neutral position with respect to the rotor 8 and becomes the same as the initial state, and the pressure difference between the left cylinder chamber 21 and the right cylinder chamber 22 disappears.

Next, if you turn the steering wheel to the left from the neutral position,
The stub shaft 1 rotates in the same direction, but since the load on the worm shaft 2 is heavy, the torsion bar 3 is twisted.

As a result, the rotation of the stub shaft 1 causes the rotor 8 to rotate in the opposite direction relative to the sleeve 10, switching the flow path, and the oil now enters the right cylinder chamber 22 and flows out from the left cylinder chamber 21.

Therefore, a pressure difference is generated between the right cylinder chamber 22 and the left cylinder chamber 21, and the piston 16 receives an operating force in the left axial direction in the figure.

Then, it operates in the same manner as described above, and steering is performed with a light operating force.

In this way, each time the left and right handlebars are operated, the torsion bar 3
Since torsional torque is frequently applied between the torsion bar 3 and the worm shaft 2, strong rotational stress is applied to the fixed portion of the torsion bar 3 and the worm shaft 2.

Therefore, in the conventional power steering device, a pin 4 is inserted through the center of the fixed part of the worm shaft 2 and the torsion bar 3 in the radial direction to prevent this fixed part from slipping due to rotational stress. It had a rotation stop function.

However, the use of pins in this manner has disadvantages in that the assembly work becomes troublesome, the number of parts increases, and the cost increases.

The present invention has been made in view of these points, and its purpose is to provide a rotary valve type power steering device that is easy to assemble and can reduce costs.

In order to achieve this objective, the present invention forms a serration joint and a guide portion having a smooth outer peripheral surface on the outer peripheral surface of one end of the torsion bar, and a serration joint and a guide portion with a smooth outer peripheral surface on the inner peripheral surface of the worm shaft. A smooth sealing surface is formed, and the torsion bar is inserted into the worm shaft, and the serration joint formed on the torsion bar is press-fitted and fixed into the serration joint formed on the worm shaft, and the guide part and sealing surface create a small clearance. It is designed to have a sealing function.

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 2 is a longitudinal sectional view of an embodiment of the rotary valve type power steering device according to the present invention.

In the figure, parts that are the same as those in FIG. 1 or have the same functions are given the same numbers, and their operations are exactly the same.

Reference numeral 31 designates a serration portion as a serration connection portion formed on the circumferential surface of the tip end of one end of the torsion bar 3, and 32 designates a guide portion formed near the serration portion 31.

Note that 29a is an inlet for supplying pressure oil from the pump to the rotary valve.

Here, the structure of the fixing portion between the torsion bar 3 and the worm shaft 2 will be explained in detail with reference to FIGS. 3 to 5.

FIG. 3 is an enlarged longitudinal sectional view of this fixing part.

A serration portion 31 formed on the surface of the tip of one end of the torsion bar 3 is press-fitted into an inner circumferential surface 33 as a serration connection portion formed on the inner circumference of the worm shaft 2.

The guide portion 32 formed on the circumferential surface of the torsion bar 3 near the serration portion 31 has a smooth surface, and the worm shaft 2 has a smooth surface.
A minute clearance is formed with a gap of approximately 15μ skin between the inner circumferential surface 34 as a sealing surface.

Since the gap in this part is so small that oil cannot pass through due to the surface tension caused by its viscosity, it has a sealing function.

To fix one end of the torsion bar 3 to the worm shaft 2, insert the torsion bar 3 into the cylinder of the worm shaft 2 from the left side in the figure, and finally press-fit the serrations 31 into the inner peripheral surface 33. At this time, the guide portion 32 enters the inner circumferential surface 34, maintains concentricity, and plays the role of a guide.

It goes without saying that the diameter of the thickest portion of the other end (the right end in the figure) of the torsion bar 3 is set smaller than the diameter of the inner peripheral surface 34.

Further, a relief portion 35 is formed at the end of the serration portion 31 to prevent the serration portion 31 from hitting in the axial direction when the torsion bar 3 is press-fitted, thereby preventing variation in the press-fit depth.

FIG. 4 is a cross-sectional view of the serration portion 31 of the torsion bar 3.

The serration portion 31 is made up of a plurality of triangular protrusions, approximately 9
It is formed by forging at four locations at 0' intervals.

FIG. 5 is a sectional view taken along the line ■-■ in FIG.

Before press-fitting, the serrations 31 are sharp as shown by the dotted line, and the inner circumferential surface 33 is also flat as shown by the dotted line, but since the serrations 31 are formed to have higher hardness than the inner circumferential surface 33. When press-fitted, the tips of the serrations 31 sink into the inner circumferential surface 33 as shown in the figure, and because they are engaged and fixed like gears, there is no possibility of them sliding against each other in the direction of rotation.

In such a configuration, when the handle is turned to the right, the stub shaft 1 rotates in the same direction, the torsion bar 3 is twisted, and the rotor 8 of the rotary valve integrally formed with the stub shaft 1 moves into the sleeve 10. The flow path is switched by rotating relative to the flow path.

The oil that entered from the inlet 29a flows through the flow path 12.15.
, 27, 26 and enters the left cylinder chamber 21, while the oil in the right cylinder chamber 22 flows out through the outlet 29 through the flow path 28, 14.

As a result, a pressure difference occurs between the left cylinder chamber 21 and the right cylinder chamber 22, and the piston 16 receives an operating force to the right in the figure.
By adding this operating force, steering can be performed with a light operating force.

Similarly, when the bundle is turned to the left, the rotor 8 rotates in the opposite direction relative to the sleeve 10, the flow path of the rotary valve is switched, and the oil enters the right cylinder chamber 22 and flows into the left cylinder. It flows out from chamber 21.

As a result, a pressure difference is generated between the right cylinder chamber 22 and the left cylinder chamber 21, and the piston 16 receives an actuation force to the left, and the addition of this actuation force allows steering to be performed with a light operation force.

In this way, in this invention, the work of fixing the torsion bar and the worm shaft is facilitated by using the guide part and press-fitting it as a guide, and the serration joint parts of the torsion bar and the worm shaft are fixed together by press-fitting. Therefore, it is possible to obtain fixing strength sufficient to withstand the rotational stress of torsion.

On the other hand, since the guide portion forms a minute clearance with respect to the sealing surface of the worm shaft, dimensional accuracy is not required as much as in press-fitting, and processing is easier.

In addition, if there is no slight clearance in this part, oil will leak when the bundle is operated, reducing the pressure difference between the left cylinder chamber and the right cylinder chamber, reducing the effect of making the bundle operation easier.However, in this invention, the guide part Since the guide function and the oil sealing function are created by forming a small clearance at the same time, oil leakage in this area is prevented and power steering characteristics do not deteriorate.

In the above embodiment, the serrations are formed at four locations on the circumferential surface of the torsion bar, but the serrations may be formed at any number of locations as long as they are two or more, or may be formed over the entire circumference.

Furthermore, in the above embodiments, the serrations as serration joints are formed on the outer peripheral surface of the torsion bar.
The serrations may be formed on the inner circumferential surface of the worm shaft, and the flat outer circumferential surface of the torsion bar may be press-fitted into the serrations to form a serration connection portion.

Conventional models used pins to prevent rotation of the torsion bar and worm shaft, and O-rings were installed to seal this part, but the present invention eliminates the need for pins and O-rings, and also simplifies the installation work. Furthermore, the fixing work by press-fitting becomes easier, which has the effect of reducing costs.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view of a conventional rotary valve type power steering device;
The figure is a longitudinal sectional view of one embodiment of the rotary valve type power steering device according to the present invention, FIG. 3 is a partially enlarged longitudinal sectional view thereof, FIG. 3 is a sectional view taken along the line ■-■ in FIG. 3. 1... Stub shaft, 2... Worm shaft, 3... Torsion bar 5...
...Pin, 7...0 ring, f3------
-Rotor, 10...Sleeve, 16...
・Piston, 17...Ball, 18...
・Cylinder body, 19...Rack teeth, 20・
...Sector shaft, 21...Left cylinder chamber, 22...Right cylinder chamber, 31...
・Serration part, 32...Guide part, 33,
34...Inner peripheral surface.

Claims (1)

[Scope of utility model registration request] A stub shaft that rotates by bundle operation, a cylindrical worm shaft provided concentrically with this stub shaft, and a torsion bar that has one end fixed to the inner circumference of this worm shaft and the other end fixed to the stub shaft. , a rotary valve including a rotor provided on the stub shaft and a sleeve provided on the worm shaft; and a piston that is worm-coupled to the outer periphery of the worm shaft and moves axially within the cylinder body by rotation of the worm shaft. , a rotary valve type power steering device comprising a sector shaft that rotates due to the movement of the piston, in which a guide portion having a serration joint portion and a smooth outer circumferential surface is formed on the outer circumferential surface of one end of the torsion bar; A serration joint and a smooth sealing surface are formed on the inner peripheral surface of the worm shaft, and the torsion bar is inserted into the worm shaft, and the serration joint formed on the torsion bar is press-fitted into the serration joint formed on the worm shaft. The rotary valve type power steering device is configured to have a sealing function by forming a minute clearance between the guide portion and the sealing surface.