JPS6139649Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention attempts to prevent chatter vibration of a steering wheel during steering of an integral type power steering device equipped with a torsion bar. In general, in an integral power steering system that uses torsional displacement of a torsion bar by steering operation to actuate a valve and switch pressure oil from a hydraulic pump to assist power, the steering wheel is used when driving at low speeds or when parking in a garage. When the vibration is large, a vibration can be felt on the steering wheel, causing discomfort to the driver.

The main causes are pulsations in the pressure oil supplied from the hydraulic pump to the power steering system, fluctuations in road resistance (tire stick slip), and worm shafts with worm grooves rotatably supported in the gear case. Due to minute fluctuations in rotational resistance, the worm shaft and input shaft resonate using the torsion bar as a spring, which causes the spool to vibrate, causing oil pressure fluctuations, which in turn induce self-excited vibrations in the hydraulic system, and this vibration causes the steering shaft to is transmitted to the steering wheel via the

Therefore, as shown in FIG.
A damping ring 03 made of tetrafluoroethylene, which is fixed to the outer periphery of the O-ring 02 by the elasticity of the O-ring 02, is pressed against the inner periphery of the left end of the wormshaft 04. Even if the wormshaft 04 vibrates due to tire stick slip due to road reaction force, the O-ring 02 and the vibration damping ring 03 made of tetrafluoroethylene keep the input shaft 01, torsion bar 05, and wormshaft 04 Since the torsion bar 05 is almost integrally connected, the vibration of the torsion bar 05 can be prevented, and the natural frequency of the vibration system consisting of the input shaft 01, the torsion bar 05, and the wormshaft 04 increases, and the wormshaft 04
An attempt was made to prevent the vibration entering the system from resonating with the vibration system.

However, since there is a large frictional force between the input shaft 01 and the wormshaft 04 to prevent the above-mentioned resonance, the input shaft 0
1 and when the input shaft 01 is twisted by the spring action of the torsion bar 05, hysteresis occurs between the force and displacement, so that the rotation angle of the steering wheel and the steering angle of the wheels are linearly proportional. Otherwise, the smoothness of steering will be impaired. Further, when the worm shaft 04 is subjected to vibration and rotates, the spool 06 moves, causing oil to flow into one oil chamber 07. At this time, since there is a frictional force between the input shaft 01 and the wormshaft 04, both shafts 01 and 04 do not easily move in the direction of zeroing the phase, so a large amount of oil flows into one of the oil chambers. When the spool 06 moves in the opposite direction due to the vibration, the spool 06 sends oil to the other oil chamber 08, and since the phase of both shafts 01 and 04 is difficult to reach zero, the amount of oil decreases. There will be more. Then, by repeating this, there was a problem in that the amplitude of the vibration increased.

In addition, if the input shaft 01 and the wormshaft 04 are slightly deviated from the same axis, the contact pressure of the damping ring 03 to the wormshaft 04 will become uneven, and the damping force will vary depending on the direction of vibration. However, since the resonance between the input shaft 01 and the worm shaft 04 could not be sufficiently suppressed, there was a problem in that the frictional force between the two shafts 01 and 04 could not be reduced.

This invention solves the above-mentioned problems, and includes an input shaft connected to the steering wheel, a worm shaft coaxially connected to the input shaft via a torsion bar, and a threaded groove on the worm shaft that allows rotation. a rack piston fitted into the rack piston, an output shaft engaged with the outer edge of the rack piston in a direction substantially perpendicular to the axial direction and connected to the wheel, a spool extending in a direction substantially perpendicular to the axial direction and provided within the worm shaft. , extending parallel to the axial direction and provided on the input shaft, the spool is moved by relative angular displacement between the input shaft and the worm shaft to supply pressurized oil to one of the axial end surfaces of the rack piston. In an integral power steering device having a drive pin, a movable body that is interlocked with the drive pin extending from the input shaft and movable within the worm shaft at a substantially right angle to the axial direction, and a space between the movable body and the worm shaft. The gist of the present invention is an integral type power steering device characterized by having a vibration damping member interposed between the two and providing frictional resistance between the two.

Vibrations generated on the output shaft due to tire stem slip, etc. that occur when steering resistance is large, such as during stationary steering, are caused by vibrations caused by the rack piston, worm shaft, etc.
It is transmitted to the input shaft via the torsion bar. Furthermore, this vibration is transmitted to the moving member by a drive pin protruding from the input shaft. However, since this movable member is provided with frictional resistance by a vibration damping member between it and the worm shaft, the vibrations are attenuated by this frictional resistance.

In particular, the main cause of vibrations transmitted to the steering handle is hydraulic vibration caused by vibration of the spool, and by reducing this vibration, vibrations can be effectively prevented.

By the way, the vibration damping member damps vibrations of the moving member relative to the worm shaft, thereby damping vibrations of the spool relative to the worm shaft, damping vibrations of the hydraulic system of the power steering device, and suppressing vibrations of the steering device. Therefore, the frictional resistance caused by the vibration damping member can be made small, so that almost no hysteresis occurs in the steering angle when the input shaft is twisted and returned, and the steering feeling is improved.

Furthermore, the damping member is simply interposed between the moving member and the worm shaft, and is therefore smaller and cheaper than conventional damping members.

Embodiments of the present invention will be described below with reference to the drawings.

In the first embodiment shown in FIGS. 2 and 3, a worm shaft 1 has a threaded groove 2 formed at its right end and a series of balls 5 inserted into a threaded groove of a rack piston 4 fitted in a gear case 3a. The large-diameter left portion thereof is rotatably supported while supporting an axial load by thrust needle bearings 6a and 6b. Rack teeth 25 are provided on a part of the outer circumference of the rack piston 4, and the output shaft 2
4, and the end of the output shaft 24 is connected to a steering wheel via a pitman arm and linkage (not shown).

The input shaft 7 is located on the coaxial line of the worm shaft 1, and one end is supported by a radial bearing 9 press-fitted into the inner diameter hole 8 of the worm shaft 1, and the other end is supported by a radial bearing 10 fixed to the top cover 11. It is rotatably supported by the valve housing 3b and connected to a steering wheel via a steering shaft (not shown).

The input shaft 7 and the worm shaft 1 are connected by a torsion bar 12 and fixing pins 26, 27, and the torsion bar 12 allows them to be angularly displaced relative to each other. In addition, in case of excessive relative angular displacement, a pin 33 fixed to the input shaft 7 is abutted and locked in a groove 32 provided in the inner diameter portion of one end of the worm shaft 1, as shown in FIG. This suppresses excessive relative angular displacement between the shafts 1 and 7. A spool 20 forming a moving body is slidably inserted into a sleeve 28 that is integrally provided in a hole formed on the left side of the worm shaft 1 and extending in a direction perpendicular to the shaft. It is fixed to a large diameter flange portion 13 of the input shaft 7 and connected to a drive pin 21 . sleeve 2
8 has a valve housing 3b as shown in FIG.
The first cylindrical chamber 3 communicates with a port 34 provided in the
5, a first annular chamber 36 communicating with the first hydraulic chamber 22 surrounded by the rack piston 4, the gear housing 3a and the valve housing 3b, and an oil reservoir (not shown) located on the right side of the first annular chamber 36. A second cylindrical chamber 37 and a first cylindrical chamber 35 communicate with each other.
A second hydraulic chamber 23 located on the left side of the rack piston 4 and connected to a second hydraulic chamber 23 surrounded by the gear housing 3a.
An annular chamber 38 and a third cylindrical chamber 39 located to the left of the second annular chamber 38 and communicating with an oil reservoir (not shown) are formed.

The damping member includes a sleeve 28 as shown in FIG.
One end is provided in the groove 29 and is in direct contact with the spool 20 on its inner surface, and is made of a member 30 such as tetrafluoroethylene that can smoothly move the spool 20 and provide a certain amount of frictional resistance, and a predetermined tension force is applied. It consists of an elastic body 31 such as an O-ring that should be attached to the member 30 mentioned above.

Next, the operation will be explained.

When you turn the handle (not shown) to the right,
The input shaft 7 rotates clockwise via a steering shaft (not shown). However, due to the ground resistance of the wheels, the output shaft 24, rack piston 4,
The worm shaft 1 does not move, so that the input shaft 7 and the worm shaft 1 undergo a relative angular displacement due to the torsion bar 12. This relative angular displacement causes the drive pin 21 provided on the flange 13 of the input shaft 7 to move the spool 20 to the right in FIG.
4. Pressure oil is supplied to the second pressure oil chamber 23 through the first cylindrical chamber 35, the second annular chamber 38, and an oil passage (not shown), and at the same time supplies pressure oil to the third cylindrical chamber 39 and the second annular chamber 38. The rack piston 4 is moved to the left, and the output shaft 24 is rotated to the left with hydraulic assistance, thereby enabling steering.

Further, at this time, the pressure oil in the second pressure oil chamber 22 flows from the first annular chamber 36 to the second cylindrical chamber 37 through an oil passage (not shown), and further flows to an oil reservoir (not shown).

With the above configuration, when the steering resistance is large, such as when parking the vehicle or parking the vehicle, the tire stakes slips due to the reaction force of the road surface, and vibration of the tire due to this stakeslip is transmitted to the output shaft 24, which is further transmitted to the output shaft 24 via the rack teeth 25. It is transmitted to the worm shaft 1. The vibration of the worm shaft 1 is transmitted to the input shaft 7 using the torsion bar 12 as a spring thread, and tries to vibrate the spool 20, but this spool 20 is connected to a member 30 forming a damping material having a preset frictional resistance. Since the movement is restricted by the elastic body 31 and the elastic body 31, the vibration is not transmitted to the hydraulic system. Therefore, the axial movement of the rack piston 4 is suppressed, and thereby the axial vibration of the worm shaft 1 is also suppressed, and unlike the conventional case, the input shaft and the worm shaft resonate and cause chatter vibration to the steering wheel. It is possible to prevent this from occurring, and it is possible to improve the driver's steering sensation.

The input shaft 7 and the worm shaft 1 are only connected via the torsion bar 12, and there is no direct frictional pressing force acting between the two shafts as in the conventional case. Since no hysteresis occurs between the twisting and return of the spool 20, the axial movement of the spool 20 is restricted by a damping member made of an O-ring 31 and a member 30 made of tetrafluoroethylene, etc. As a result, the spool 20 does not move due to high frequency vibrations such as tire stick slip, and therefore the vibrations are attenuated because the hydraulic system does not vibrate. In addition, since it is only necessary to suppress the vibration of the spool 20, the frictional force applied between the spool 20 and the sleeve 28 by the vibration damping member can be small.
The damping member is small and can be formed at low cost.

In the second embodiment shown in FIGS. 4 and 5, instead of providing the damping member between the spool 20 and the sleeve 28 in the first embodiment, a plunger is installed on the worm shaft 1 separately from the spool 20 and the sleeve 28. 4
1 and a sleeve 42, and this plunger 41
and the sleeve 42, the member 30 and the O-ring 31
A damping member consisting of the following is interposed. Components common to those in the first embodiment will be described with the same reference numerals.

In FIGS. 4 and 5, the sleeve 42 is provided within the input shaft 7, which is symmetrical with the axes of the sleeve 28 and the input shaft 7, and extends parallel to the sleeve 28. A plunger 41 forming a movable body is fitted into the sleeve 42 so as to be movable in the axial direction thereof, and a drive pin 40 forming a drive pin provided on the input shaft 7 and extending parallel to its axis is connected to the fifth drive pin 40 . As shown in the figure, it is fitted into the central reduced diameter portion of the plunger 41. The vibration damping members include O-rings 31a and 31b fitted into grooves 29a and 29b of the plunger 41, and this O-ring 31.
The O-rings 31a, 31b are press-fitted into the outer circumferences of the O-rings 31a,
It consists of members 30a and 30b made of tetrafluoroethylene, etc., which come into contact with the sleeve 42 by the pressing force of 31b. Further, the same operation and effect as the first embodiment described above is achieved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a conventional integral type power steering device, FIG. 2 is a sectional view showing a first embodiment of the present invention, FIG. A sectional view showing a second embodiment of the present invention,
FIG. 5 is a view taken along the - arrow in FIG. 4. 1...Worm shaft, 4...Rack piston, 7
...Input axis, 12...Torsion bar, 2
0...Spool, 21...Drive pin, 28...
...Sleeve, 30...Member, 31...O-ring,
40...Drive pin, 41...Plunger, 4
2...Sleeve.

Claims (1)

[Scope of utility model registration request] An input shaft connected to the steering wheel, a worm shaft coaxially connected to the input shaft via a torsion bar,
A rack piston rotatably fitted into a thread groove of the worm shaft; an output shaft engaged with the outer edge of the rack piston in a direction substantially perpendicular to the axial direction of the shaft; and an output shaft connected to the wheel; A spool extending from the worm shaft is provided on the input shaft, and the spool is moved by relative angular displacement between the input shaft and the worm shaft to apply pressure oil to one of the axial end surfaces of the rack piston. an integral type power steering device having a drive pin that supplies the input shaft, a movable body interlocked with the drive pin extending from the input shaft and movable substantially perpendicularly to the axial direction within the worm shaft; the movable body and the worm shaft; An integral type power steering device characterized by comprising a vibration damping member interposed between the two and providing frictional resistance between the two.