JPH0211250Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) The present invention is a so-called speed-sensitive type of power that is mounted on a vehicle and assists the steering force of the steering wheel, and also reduces the assisting force according to the vehicle speed. Regarding a steering device.

(Prior art) A type of power steering device includes a valve rotor that rotates integrally with a first shaft rotatably supported within a valve housing, and a valve rotor that is connected coaxially and rotatably relative to the first shaft by a predetermined amount. a valve sleeve that rotates in tandem with a second shaft and is arranged concentrically around the outer periphery of the valve rotor; and a valve sleeve that is provided between the valve sleeve and the valve rotor and can switch the supply/discharge flow path to each oil chamber of the power cylinder. A power rudder comprising a rotary valve type control valve that operates the switching valve mechanism by relative rotation between the two shafts to control supply and discharge of hydraulic oil to each oil chamber of the power cylinder. There is a device to remove it.

By the way, in this kind of power steering device, the two shafts are generally connected by a torsion bar, so that relative rotation occurs between the two shafts. In addition, in this kind of speed-sensitive power steering device, as proposed in Japanese Patent Publication No. 54-9368, for example, an engagement recess provided on either side of the two shafts is used. A ball serving as a cam follower supported on one of the other shafts is engaged, and a hydraulic pressure that increases according to the vehicle speed is applied to this ball, so that the engagement force of the ball with the engagement recess is increased according to the vehicle speed. I have to. Accordingly, in such a power steering device, the relative rotation between the two axes is gradually regulated according to the vehicle speed, so that the assisting force generated according to the degree of the relative rotation decreases according to the vehicle speed.

As described above, in this type of conventional speed-sensitive power steering device, the torsion bar is an essential component as a main component that connects both shafts so that they can rotate relative to each other. In order to control the relative rotation between the two axes, it is necessary to apply a considerably high hydraulic pressure to the ball.

(Purpose of the invention) The present invention has been made to solve this problem, and its main purpose is to provide an engaging recess or an engaging recess with a cam surface provided on one side of both shafts constituting this type of power steering device. The coupling convex portion is connected by engagement with a cam follower that is assembled on the other of the two shafts and whose pressing force increases according to the vehicle speed, and the torsion bar, which was conventionally considered indispensable, is omitted and the torsional rigidity of the device is improved. The object of the present invention is to make it possible to increase the hydraulic pressure applied to the cam follower and to lower the hydraulic pressure applied to the cam follower, and to make it possible to easily change the steering force.

(Structure of the invention) In order to achieve the above object, the present invention provides a power steering device of this type, in which an engaging recess or an engaging convex portion having a pair of cam surfaces is formed at one inner end of the two shafts. At the same time, a cam follower is engaged with each cam surface of the engagement recess or the engagement protrusion through a ball to restrict rotation and is pushed a predetermined amount in the axial direction when the one shaft rotates. Both shafts are assembled to the other shaft with their rotation restricted, and the cam follower is urged in the axial direction by a spring member and hydraulic pressure increased according to the vehicle speed to press the balls against the respective cam surfaces. Its structural feature lies in its connection.

(Operations and Effects of the Invention) As a result, in the present invention, the relative rotation between the two shafts can be regulated according to the pressing force between the cam follower and each cam surface, which connect the two shafts to each other. A speed-sensitive power steering device in which the auxiliary force decreases depending on the vehicle speed can be configured without using a torsion bar, and the torsional rigidity of the device can be increased. In addition, in this invention, the cam follower is preloaded with a spring to press the ball against each force surface, so the hydraulic pressure applied to the cam follower can be small, and by changing the spring member, the steering can be controlled. Power can be easily changed. Furthermore, in the present invention, since the cam follower is engaged with each cam surface via the ball, the dynamic friction and static friction between the two are greater than when the cam follower is directly engaged with each cam surface. The difference becomes smaller, and the stiffness of the steering wheel at the beginning and during the steering becomes equal, improving the steering feeling.

(Embodiment) Hereinafter, an embodiment of the present invention will be described based on the drawings. FIG. 1 shows a power steering device according to the present invention. The power steering device is a rack and pinion type power steering device, and the power steering device includes an input shaft 12 rotatably supported within a valve housing 11 and a pinion shaft 14 rotatably supported within a gear housing 13. The two shafts 12 and 14 are connected to each other by a cam follower 24 and a pressing mechanism 30, which will be described later. A portion of the input shaft 12 inside the valve housing 11 is formed into a valve rotor 21, and a valve sleeve 22 is disposed concentrically around the outer periphery of the valve rotor 21. Further, the pinion shaft 14 is constantly engaged with a rack bar 15 that constitutes the rod of the power cylinder 41.

The valve rotor 21 is connected to the input shaft 12
It is provided with arcuate grooves 21a that are equally formed at eight locations on the outer circumference and extend in the axial direction, and communication holes 21b that extend from the bottom of every other arcuate groove 21a toward the axis and reach the inner hole 21c. Further, the valve rotor 21 has a communication hole 21 located above the valve sleeve 22 that extends from its outer periphery toward the axis and reaches the inner hole 21c.
It is equipped with d.

The valve sleeve 22 is a component of the switching valve mechanism together with the valve rotor 21.
1, and is integrally connected to the upper end of the pinion shaft 14 via a connecting pin 23 at its lower end. This valve sleeve 22 is provided with switching grooves 22a that are equally formed at eight locations on the inner circumference and extend in the axial direction. Of these switching grooves 22a, half of them communicate with the upper annular groove 22b provided on the outer periphery of the valve sleeve 22, and the remaining half communicate with the lower annular groove 22c provided on the outer periphery of the valve sleeve 22.
is connected to. This valve sleeve 22 is similar to a known valve sleeve, and the upper annular groove 22b communicates with the right oil chamber R1 of the power cylinder 41 via the supply/discharge passage 41a, and the lower annular groove 22c communicates with the supply/discharge passage 41a. 41b to the left oil chamber R2 of the power cylinder 41, and a central annular groove 22d provided on the outer periphery of the valve sleeve 22 communicates to a hydraulic pump (not shown) via a supply flow path 42a. The oil chamber R3, which is located above the valve sleeve 22 and has a communication hole 21d, communicates with the tank of the hydraulic pump via the discharge passage 42b.

As a result, in this power steering device, when relative rotation occurs in both shafts 12 and 14, as in the known power steering device, the hydraulic oil supplied through the supply flow path 42a flows into the central annular shape of the valve sleeve 22. The right oil chamber R1 or the left oil chamber R of the power cylinder 41 via the groove 22d, one of the switching grooves 22a, the upper annular groove 22b or the lower annular groove 22c, and one of the supply/discharge passages 41a and 41b.
Supplied within 2 days. At the same time, the hydraulic oil in the left oil chamber R2 or the right oil chamber R1 is transferred to the other supply/discharge channel 41.
b, 41a, lower annular groove 2 of valve sleeve 22
2c or upper annular groove 22b, the other switching groove 22
a, the oil is discharged to the tank via the oil chamber R3 and the discharge passage 42b. As a result, the steering force is assisted when turning the steering wheel to the right or left.

Therefore, in this embodiment, a stepped through hole 14a provided concentrically in the pinion shaft 14
A cam follower 24 is attached so as to be slidable in the axial direction, and an engagement recess 12a is provided at the lower end of the input shaft 12. Furthermore, a pressing mechanism 30 for pressing the cam follower 24 is provided at the lower end of the gear housing 13 .

As shown in FIGS. 1 to 3, the cam follower 24 includes a conical cam piece 24a and a rod portion 24.
The cam piece 24a is provided with a pair of three-dimensional cam surfaces 24c at its upper end, and has elongated holes 24d extending a predetermined length in the axial direction and opening at the outer periphery on both sides. This cam follower 24 is connected to the through hole 1 of the pinion shaft 14.
4a liquid-tightly and slidably in the axial direction,
It is assembled to the pinion shaft 14 via a connecting pin 25 that is inserted into the elongated hole 24d and fixed to the pinion shaft 14. Also, between the engagement recess 12a of the input shaft 12 and the cam piece 24a of the cam follower 24, there is a cage 2 shown in FIG.
Four balls 26b rotatably supported by 6a are interposed. As a result, the cam follower 24
opposes the engagement recess 12a provided at the lower end of the input shaft 12, and elastically engages with the pair of cam surfaces 12b of the engagement recess 12a via the balls 26b due to the pressing force from the pressing mechanism 30. ing.

The pressing mechanism 30 includes a slurry plate 31, a piston 32, and a disc spring 33, which are interposed in the lower end opening 13a of the gear housing 13.
It is assembled by a plug 16 screwed into the lower end opening 13a. The disc spring 33 urges the cam follower 24 toward the engagement recess 12a via the piston 32 and the thrust plate 31, and causes each ball 26b to move on each cam surface 24c of the cam follower 24 to each cam surface 12b of the engagement recess 12a. It is elastically engaged with. The piston 32 is located in the recess 1 of the plug 16.
The oil chamber R4 is fitted into the oil chamber R4 in a liquid-tight manner and slidable in the axial direction, and a hydraulic pressure that increases in accordance with the vehicle speed is applied to the oil chamber R4. Note that the hydraulic pressure generating means for generating such hydraulic pressure may be of a conventionally known type, for example, as shown in FIG.
A hydraulic pump 43 driven by the propeller shaft of the vehicle, an orifice 44 that generates hydraulic pressure according to the vehicle speed, and a relief valve 4 that regulates the maximum pressure.
A means consisting of 5 etc. is used.

In the power steering system of this embodiment configured in this way, when the input shaft 12 is rotated, the disc spring 33 is bent in accordance with the steering force due to the action of each cam surface 12b, and the cam follower 24 is slid. , causing relative rotation in both shafts 12 and 14. Therefore, the steering force of the steering wheel is assisted. However, in this example,
Hydraulic pressure is applied to the piston 32 of the pressing mechanism 30, which increases in accordance with the vehicle speed. Therefore, the apparent spring constant in the rotational direction of both shafts 12 and 14 increases in accordance with the vehicle speed, and the relative rotation of both shafts 12 and 14 is gradually regulated accordingly. Therefore, the assisting force of the steering wheel relative to the steering force decreases according to the vehicle speed.

As described above, according to the power steering device, a speed-sensitive power steering device can be configured without using a torsion bar for the connecting member between the shafts 12 and 14, and the torsional rigidity of the device can be increased. be able to. Also, attach the cam follower 24 to the disc spring 3.
3, the hydraulic pressure applied to the cam follower 24 can be lowered accordingly, and the steering force required for the steering wheel can be easily changed by changing the disc spring 33. . Furthermore, since the cam follower is engaged with each cam surface via the ball, the difference between the dynamic friction and static friction between the two is smaller than when the cam follower 24 is directly engaged with each cam surface 12b. Become. As a result, the stiffness of the steering wheel at the beginning of steering and during the course of steering becomes equal, and the steering feeling is improved.

(Modification) In this embodiment, an example is shown in which the engagement recess 12a is provided on the input shaft 12 side, and the cam piece 24a that engages with the cam follower 24 side of the pinion shaft 14 is provided. In some designs, these may be provided on opposite shaft sides. Alternatively, the cam follower 24 may be integrally fixed to the pinion shaft 14, and the pinion shaft 14 may be assembled to be slidable by a predetermined amount in the axial direction, and this may be pressed by a pressing mechanism. Furthermore, in this embodiment, an example is shown in which the valve rotor 21 is integrally formed with the input shaft 12, but
In the present invention, the valve rotor may be formed separately from the input shaft and connected to the input shaft so as to rotate integrally therewith. In this embodiment, a rack and pinion type power steering device is shown, but the present invention can also be implemented in a recirculating ball type power steering device.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of a power steering device according to an example of the present invention, Fig. 2 is an enlarged partial perspective view of a cam follower used in the device, and Fig. 3 is an enlarged view showing the connecting portion of both shafts in the device. FIG. 4 is a partial vertical sectional view and an enlarged perspective view of the cage used in the device. Explanation of symbols, 11... Valve housing, 12
...Input shaft, 12a...Engagement recess,
14... Pinion shaft, 21... Valve rotor, 22... Valve sleeve, 24... Cam follower, 26b... Ball, 30... Pressing mechanism, 3
3...Disc spring.

Claims (1)

[Scope of utility model registration request] a first rotatably supported within the valve housing;
a valve rotor that rotates integrally with the shaft;
A valve sleeve that rotates integrally with a second shaft coaxially connected to the shaft and capable of relative rotation by a predetermined amount and is arranged concentrically around the outer periphery of the valve rotor, and a power cylinder that is provided between the valve sleeve and the valve rotor. is provided with a switching valve mechanism capable of switching the supply/discharge flow path to each oil chamber of the power cylinder, and the switching valve mechanism is actuated by relative rotation between the two shafts to supply/discharge hydraulic oil to each oil chamber of the power cylinder. In a power steering device equipped with a rotary valve type control valve, an engaging recess or an engaging convex portion having a pair of cam surfaces is formed at the inner end of one of the shafts, and the engaging recess or the engaging convex portion is provided with a pair of cam surfaces. A cam follower is engaged with each cam surface of the engagement convex portion via a ball to restrict its rotation, and is also pushed by a predetermined amount in the axial direction when the one shaft rotates, and causes the other of the two shafts to rotate. The two shafts are connected by being regulated and assembled, and the cam follower is urged in the axial direction by a spring member and hydraulic pressure that increases in accordance with the vehicle speed to press the ball against each of the cam surfaces. power steering device.